阅读说明：本技术 图像形成装置 (Image forming apparatus with a toner supply device ) 是由 末冈丈典 于 2020-03-06 设计创作，主要内容包括：本发明公开了图像形成装置。图像形成装置包括图像承载构件、转印构件、电压源、被配置成检测电流值或电压值的传感器、图像检测部、以及能够基于在测试记录材料上形成的测试图的检测结果执行用于设定要被施加到转印构件的转印电压的模式下的操作。在所述模式下的操作期间,控制器基于当转印部中不存在记录材料时在向转印构件施加电压的情况下由传感器获取的第一检测结果、以及当所述转印部中存在测试记录材料时在向转印构件施加测试电压的情况下由传感器获取的第二检测结果来设定转印电压。(The invention discloses an image forming apparatus. The image forming apparatus includes an image bearing member, a transfer member, a voltage source, a sensor configured to detect a current value or a voltage value, an image detection portion, and an operation in a mode for setting a transfer voltage to be applied to the transfer member can be performed based on a detection result of a test chart formed on a test recording material. During operation in the mode, the controller sets the transfer voltage based on a first detection result obtained by the sensor in a case where the voltage is applied to the transfer member when the recording material is not present in the transfer portion, and a second detection result obtained by the sensor in a case where the test voltage is applied to the transfer member when the test recording material is present in the transfer portion.)

1. An image forming apparatus, comprising:

an image bearing member configured to bear a toner image;

a transfer member configured to transfer a toner image from the image bearing member onto a recording material at a transfer portion with a voltage applied;

a voltage source configured to apply a voltage to the transfer member;

a sensor configured to detect a current value or a voltage value when a voltage is applied from the voltage source to the transfer member;

an image detection section configured to detect an image on a recording material; and

a controller capable of performing an operation in a mode for setting a transfer voltage to be applied to the transfer member when a toner image is transferred onto a recording material, based on a detection result that a test image is transferred onto a test recording material by applying a plurality of different transfer voltages from the voltage source to the transfer member to generate a test pattern and then the test pattern is detected by the image detecting section,

wherein, during operation in the mode, the controller sets a transfer voltage based on a first detection result obtained by the sensor with a voltage applied to the transfer member when no recording material is present in the transfer portion, and a second detection result obtained by the sensor with a test voltage applied to the transfer member when a test recording material is present in the transfer portion.

2. The image forming apparatus according to claim 1, wherein during operation in the mode, the controller sets the transfer voltage based on information on a thickness of the test recording material.

3. The image forming apparatus according to claim 1, wherein the first detection result is a relationship between a voltage and a current acquired by the sensor in a case where a plurality of levels of voltages are applied from the voltage source to the transfer member when no recording material is present in the transfer portion.

4. An image forming apparatus according to claim 3, wherein the relationship is a first relationship, and the controller sets the transfer voltage based on the first relationship and a second relationship between a voltage and a current acquired by the sensor with a plurality of levels of voltage applied to the transfer member from the voltage source when the test recording material is present in the transfer portion.

5. The image forming apparatus according to claim 4, wherein the controller sets the transfer voltage based on information on a difference of the first relation and the second relation, a third relation between information on a thickness of the recording material and an upper limit on the difference, and information on a thickness of the test recording material.

6. The image forming apparatus according to claim 1, wherein the second detection result is a detection result of the sensor acquired when the test image is transferred onto the recording material.

7. The image forming apparatus according to claim 1, wherein the first detection result is a detection result of the sensor acquired when no recording material is present in the transfer portion in a period from an instruction to output a test chart is input to the controller until the test chart is output.

8. The image forming apparatus according to claim 1, wherein during the operation in the mode, the controller performs a process of notifying information on the transfer voltage set by the controller.

9. An image forming apparatus according to claim 1, wherein during operation in the mode, the controller is capable of receiving an instruction to change the transfer voltage set by the controller.

10. The image forming apparatus according to claim 2, wherein the information on the thickness is information on a thickness of the recording material, a basis weight of the recording material, or a kind of the recording material based on the thickness of the recording material or the basis weight of the recording material.

11. The image forming apparatus according to claim 1, wherein the image detecting section detects a density of the test image on the test chart by being supplied with the test chart output from the image forming apparatus.

12. The image forming apparatus according to claim 1, wherein the image detecting section detects a density of the test image on the test chart when the test chart is output from the image forming apparatus.

13. An image forming apparatus according to claim 1, wherein said image bearing member is an intermediate transfer member configured to feed a toner image primarily transferred from another image bearing member to a recording material for secondary transfer.

14. An image forming apparatus according to claim 1, wherein said transfer member is in contact with said image bearing member and forms said transfer portion, wherein a recording material is nipped and fed between itself and said image bearing member.

Technical Field

The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile machine using an electrophotographic type process or an electrostatic recording system.

Background

In an image forming apparatus using an electrophotographic type process or the like, a toner image formed on an image bearing member such as a photosensitive member or an intermediate transfer member is transferred onto a recording material. The transfer of the toner image from the image bearing member to the recording material is generally performed by applying a transfer voltage to a transfer member such as a transfer roller that is in contact with the image bearing member to form a transfer portion. The transfer voltage may be determined based on a transfer portion voltage corresponding to the resistance of the transfer portion detected during the pre-rotation process before the image formation and a recording material portion voltage set in advance depending on the type of the recording material. Thus, an appropriate transfer voltage can be set according to environmental fluctuations, transfer member use history, recording material type, and the like.

However, there are various types and conditions of recording materials used in image formation, and therefore, a preset recording material portion voltage may be higher or lower than an appropriate transfer voltage. In this case, it is proposed to provide an adjustment mode to adjust the set voltage (value) of the transfer voltage in accordance with the recording material actually used in image formation. An image forming apparatus of an intermediate transfer type including an intermediate transfer member will be further described as an example.

Japanese laid-open patent application No.2013-37185 proposes an image forming apparatus operable in an adjustment mode for adjusting a set voltage (value) of a secondary transfer voltage. In this adjustment mode, a chart (chart) in which a plurality of patches (test images) are formed on one recording material is output while switching the secondary transfer voltage for each patch (patch). Also, the density of each patch is detected, and depending on the detection result thereof, an optimum secondary transfer voltage condition is selected.

However, in the above-described conventional image forming apparatus, an image defect causes the recording material to be discharged during secondary transfer and the charge polarity of the toner to be reversed at the associated portion, and the toner is not transferred onto the recording material and causes white void (hereinafter also referred to as "white void") to occur in a dot shape in some cases.

"white voids" are easily visualized on a halftone image, but with respect to image density, it is difficult to distinguish the difference between the occurrence and non-occurrence of "white voids". For this reason, at the set voltage (value) of the secondary transfer voltage selected from the detection result of the patch density as described above, the absolute value of the secondary transfer voltage is excessively large, so that "white void" occurs in some cases.

Disclosure of Invention

Therefore, an object of the present invention is to provide an image forming apparatus capable of appropriately adjusting the setting of the transfer voltage in a configuration in which the setting of the transfer voltage is adjusted by outputting a diagram on which a test image is formed.

According to an aspect of the present invention, there is provided an image forming apparatus including: an image bearing member configured to bear a toner image; a transfer member configured to transfer the toner image from the image bearing member onto a recording material at a transfer portion with a voltage applied; a voltage source configured to apply a voltage to the transfer member; a sensor configured to detect a current value or a voltage value when a voltage is applied from a voltage source to the transfer member; an image detection section configured to detect an image on a recording material; and a controller capable of performing an operation in a mode for setting a transfer voltage to be applied to the transfer member when the toner image is transferred onto the recording material, based on a detection result of the test image being transferred onto the test recording material by applying a plurality of different transfer voltages from the voltage source to the transfer member to generate the test pattern and then the test pattern being detected by the image detecting portion, wherein during the operation in the mode, the controller sets the transfer voltage based on a first detection result acquired by the sensor in a case where the voltage is applied to the transfer member when the recording material is not present in the transfer portion and a second detection result acquired by the sensor in a case where the test voltage is applied to the transfer member when the test recording material is present in the transfer portion.

Other features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

Drawings

Fig. 1 is a schematic cross-sectional view of an image forming apparatus.

Fig. 2 is a block diagram showing a schematic configuration of a control system of the image forming apparatus.

Fig. 3 is a flowchart illustrating an outline of a control process of the secondary transfer voltage.

Fig. 4 is a graph showing voltage-current characteristics acquired in the control of the secondary transfer voltage.

Fig. 5 is a diagram showing an example of table data of recording material partial voltages.

Fig. 6 is a schematic diagram of the chart image data output in the operation in the adjustment mode.

Part (a) and part (b) of fig. 7 are schematic diagrams of the chart image data output in the operation in the adjustment mode.

Fig. 8 is a flowchart showing an outline of an operation procedure in the adjustment mode.

Fig. 9 is a schematic diagram of an adjustment mode setting screen.

Fig. 10 is a graph showing an example of a relationship between the average value of the luminance of the blocks and the adjustment value of the secondary transfer voltage.

Fig. 11 is a graph showing an example of the relationship between the recording material partial voltage and the tendency to generate "white voids".

Fig. 12 is a diagram showing an example of table data of the upper limit of the recording material partial voltage.

Parts (a) and (b) of fig. 13 are graphs showing an example of the process of acquiring the adjustment value.

Fig. 14 is a schematic sectional view of an image forming apparatus in another embodiment.

Detailed Description

Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the accompanying drawings.

[ example 1]

1. Structure and operation of image forming apparatus

Fig. 1 is a schematic sectional view of an image forming apparatus 1 of this embodiment. The image forming apparatus 1 of this embodiment is a tandem type full-color printer capable of forming a full-color image by using an electrophotographic type and adopting an intermediate transfer type. However, the image forming apparatus of the present invention is not limited to the tandem type image forming apparatus, and may be another type of image forming apparatus. Further, the image forming apparatus is not limited to an image forming apparatus capable of forming a full-color image, and may be an image forming apparatus capable of forming only a monochrome image. In addition, the image forming apparatus may also be an image forming apparatus of various uses, such as a printer, various printing machines, a copying machine, a facsimile machine, and a multifunction machine.

As shown in fig. 1, the image forming apparatus 1 includes an apparatus main assembly 10, a feeding portion (not shown), an image forming portion 40, a discharging portion (not shown), a controller 30, an operating portion 70 (fig. 2). Inside the apparatus main assembly 10, a temperature sensor 71 (fig. 2) capable of detecting the temperature inside the apparatus and a humidity sensor 72 (fig. 2) capable of detecting the humidity inside the apparatus are provided. The image forming apparatus 1 can form a four-color full-color image on a recording material (sheet, transfer material) S according to image signals supplied from an image reading portion 80 and an external device 200 (fig. 2), the image reading portion 80 serving as a reading member for reading an image on the sheet. As the external device 200, a host device such as a personal computer, a digital camera, or a smartphone can be cited. Here, the recording material S is a material on which a toner image is formed, and specific examples thereof include plain paper, a synthetic resin sheet instead of plain paper, cardboard, and an overhead projector sheet.

The image forming portion 40 can form an image on the recording material S fed from the feeding portion based on the image information. The image forming portion 40 includes image forming units 50y, 50m, 50c, 50k, toner bottles 41y, 41m, 41c, 41k, exposure devices 42y, 42m, 42c, 42k, an intermediate transfer unit 44 and a secondary transfer device 45, and a fixing portion 46. The image forming units 50y, 50m, 50c, and 50k form yellow (y), magenta (m), cyan (c), and black (k) images, respectively. In the case where the description is applied to all colors, reference may be made to elements having the same or corresponding functions or structures provided for the four image forming units 50y, 50m, 50c, and 50k, where y, m, c, and k are omitted. Here, the image forming apparatus 1 can also form a single-color or multi-color image such as a single-color black image by using the image forming unit 50 for a desired single color or some of four colors.

The image forming unit 50 includes the following components. First, a photosensitive drum 51 as a first image bearing member is provided, the photosensitive drum 51 being a drum-type (cylindrical) photosensitive member (electrophotographic photosensitive member). Further, a charging roller 52 as a roller-type charging member is used as the charging means. Further, the developing device 20 is provided as a developing member. Further, the pre-exposure device 54 is provided as a charge eliminating section. Further, a cleaning blade 55 as a cleaning member is provided as the photosensitive member cleaning member. The image forming unit 50 forms a toner image on an intermediate transfer belt 44b to be described later. The image forming unit 50 is unitized as a process cartridge, and can be mounted to and dismounted from the apparatus main assembly 10.

The photosensitive drum 51 is movable (rotatable) so as to carry an electrostatic image (electrostatic latent image) or a toner image. In this embodiment, the photosensitive drum 51 is an organic photosensitive member (OPC) having a negative charging property with an outer diameter of 30 mm. The photosensitive drum 51 has an aluminum cylinder as a base material and a surface layer formed on the surface of the base material. In this embodiment, the surface layer includes three layers of an undercoat layer, a photocharge-generating layer, and a charge-transporting layer, which are applied and laminated in this order on the substrate. When an image forming operation is started, the photosensitive drum 51 is driven to rotate at a predetermined process speed (peripheral speed) in a direction (counterclockwise) indicated by an arrow in the figure by a motor (not shown) as a driving member.

The surface of the rotating photosensitive drum 51 is uniformly charged by the charging roller 52. In this embodiment, the charging roller 52 is a rubber roller, and the charging roller 52 is in contact with the surface of the photosensitive drum 51 and is rotated by the rotation of the photosensitive drum 51. The charging roller 52 is connected to a charging bias power source 73 (fig. 2). The charging bias power source 73 applies a charging bias (charging voltage) to the charging roller 52 during the charging process.

The surface of the charged photosensitive drum 51 is scanned and exposed by the exposure device 42 in accordance with image information, so that an electrostatic image is formed on the photosensitive drum 51. In this embodiment, the exposure device 42 includes a laser scanner. The exposure device 42 emits a laser beam according to the separation color image information output from the controller 30, and scans and exposes the surface (outer circumferential surface) of the photosensitive drum 51.

The electrostatic image formed on the photosensitive drum 51 is developed (visualized) by supplying developer toner thereto by the developing device 20, so that a toner image is formed on the photosensitive drum 51. In this embodiment, the developing device 20 contains a two-component developer (also simply referred to as "developer") including nonmagnetic toner particles (toner) and magnetic carrier particles (carrier). The toner is supplied from the toner bottle 41 to the developing device 20. The developing device 20 includes a developing sleeve 24. The developing sleeve 24 is made of a nonmagnetic material (aluminum in this embodiment) such as aluminum or nonmagnetic stainless steel. Inside the developing sleeve 24, a magnetic roller as a roller-shaped magnet is fixed and arranged so as not to rotate relative to the main body (developing container) of the developing apparatus 20. The developing sleeve 24 carries and conveys the developer to a developing area facing the photosensitive drum 51. A developing bias power source 74 (fig. 2) is connected to the developing sleeve 24. The developing bias power source 74 applies a developing bias (developing voltage) to the developing sleeve 24 during a developing process operation. In this embodiment, the normal charging polarity of the toner (which is the charging polarity of the toner during development) is negative.

The intermediate transfer unit 44 is arranged to face the four photosensitive drums 51y, 51m, 51c, 51 k. The intermediate transfer unit 44 includes an intermediate transfer belt 44b constituted by an endless belt as a second image bearing member. The intermediate transfer belt 44b is wound around a plurality of rollers such as a driving roller 44a, a driven roller 44d, primary transfer rollers 47y, 47m, 47c, 47k, and an inner secondary transfer roller 45 a. The intermediate transfer belt 44b is movable (rotatable) so as to carry a toner image. The driving roller 44a is rotationally driven by a motor (not shown) as a driving member, and rotates (circulates) the intermediate transfer belt 44 b. The driven roller 44d is a tension roller that controls the tension of the intermediate transfer belt 44b to be constant. The driven roller 44d is subjected to a force that urges the intermediate transfer belt 44b toward the outer peripheral surface by an urging force of a spring (not shown) as a biasing member, and by this force, a tension of about 2kg to 5kg is applied in the feeding direction of the intermediate transfer belt 44 b. The inner secondary transfer roller 45a constitutes a secondary transfer apparatus 45 as will be described later. A driving force is transmitted to the intermediate transfer belt 44b by the driving roller 44a, and the intermediate transfer belt 44b is rotationally driven in the arrow direction (clockwise) in the figure at a predetermined peripheral speed corresponding to the peripheral speed of the photosensitive drum 51. Further, the intermediate transfer unit 44 is provided with a belt cleaning device 60 as an intermediate transfer member cleaning means.

Primary transfer rollers 47y, 47m, 47c, 47k (which are roller-type primary transfer members) as primary transfer members are arranged to face the photosensitive drums 51y, 51m, 51c, 51k, respectively. The primary transfer roller 47 holds the intermediate transfer belt 44b between the photosensitive drum 51 and the primary transfer roller 47. Thereby, the intermediate transfer belt 44b contacts the photosensitive drum 51 to form a primary transfer portion (primary transfer nip portion) 48 with the photosensitive drum 51.

In the primary transfer portion 48, the toner image formed on the photosensitive drum 51 is primarily transferred onto the intermediate transfer belt 44b by the action of the primary transfer roller 47. That is, in this embodiment, the negative toner image on the photosensitive drum 51 is primarily transferred onto the intermediate transfer belt 44b by applying a positive primary transfer voltage to the primary transfer roller 47. For example, when a full-color image is formed, the yellow, magenta, cyan, and black toner images formed on the photosensitive drums 51y, 51m, 51c, and 51k are transferred so as to be sequentially superimposed on the intermediate transfer belt 44 b. A primary transfer power source 75 (fig. 2) is connected to the primary transfer roller 47. The primary transfer power source 75 applies a DC voltage having a polarity opposite to the normal charging polarity (positive in this embodiment) of the toner as a primary transfer bias (primary transfer voltage) to the primary transfer roller 47 during the primary transfer process operation. The primary transfer power source 75 is connected to a voltage detection sensor 75a that detects an output voltage and a current detection sensor 75b that detects an output current (fig. 2). In this embodiment, primary transfer power supplies 75y, 75m, 75c, and 75k are provided for the primary transfer rollers 47y, 47m, 47c, and 47k, respectively, and the primary transfer voltages applied to the primary transfer rollers 47y, 47m, 47c, and 47k can be individually controlled.

In this embodiment, the primary transfer roller 47 has a core bar and an elastic layer of ion conductive foam rubber (NBR rubber). The outer diameter of the primary transfer roller 47 is, for example, 15mm to 20 mm. furthermore, as the primary transfer roller 47, a rubber having 1 × 10 can be preferably used⁵Omega to 1 × 10⁸A roller having a resistance value of Ω (N/N (23 ℃ C., 50% RH) applied at 2 kV).

In this embodiment, the intermediate transfer belt 44b is an endless belt having a three-layer structure including, in order from the inner peripheral surface side, a base layer, an elastic layer, anda surface layer. As the resin material constituting the base layer, a resin such as polyimide or polycarbonate, or a material containing an appropriate amount of carbon black as an antistatic agent in various rubbers can be suitably used. The thickness of the substrate layer is, for example, 0.05[ mm ]]To 0.15[ mm ]]. As the elastic material constituting the elastic layer, a material containing an appropriate amount of an ion conductive agent in various rubbers such as urethane rubber, silicone rubber, and the like can be suitably used. The thickness of the elastic layer is, for example, 0.1[ mm ]]To 0.500[ mm ]]. As a material constituting the surface layer, a resin such as a fluororesin may be suitably used. The surface layer has a small adhesion of the toner to the surface of the intermediate transfer belt 44b, and makes it easier to transfer the toner onto the recording material S at the secondary transfer portion N. The thickness of the surface layer is, for example, 0.0002[ mm ]]To 0.020[ mm ]]In this embodiment, for the surface layer, for example, one kind of resin material such as polyurethane, polyester, epoxy resin or two or more kinds of elastic materials such as elastic material rubber, elastomer, butyl rubber are used as the base material, and, as a material for reducing the surface energy and improving the lubricity of this base material, for example, powder or particles (such as fluorine resin) having one kind or two kinds or different particle diameters are dispersed so that the surface layer is formed in this embodiment, the intermediate transfer belt 44b has 5 × 10⁸To 1 × 10¹⁴[Ω，cm]Volume resistivity (23 ℃, 50% RH), and a hardness of MD1 hardness of 60 ° to 85 ° (23 ℃, 50% RH). In this embodiment, the static friction coefficient of the intermediate transfer belt 44b is 0.15 to 0.6(23 ℃, 50% RH, type94i manufactured by HEIDON). In this embodiment, a three-layer structure is employed, but a single-layer structure of a material corresponding to that of the base layer may also be employed.

On the outer peripheral surface side of the intermediate transfer belt 44b, an outer secondary transfer roller 45b constituting a secondary transfer device 45 together with the inner secondary transfer roller 45a is disposed. The outer secondary transfer roller 45b contacts the intermediate transfer belt 44b in contact with the inner secondary transfer roller 45a, and forms a secondary transfer portion (secondary transfer nip) N between the intermediate transfer belts 44 b. The toner image formed on the intermediate transfer belt 44b is secondarily transferred onto the recording material S in the secondary transfer portion N by the action of the secondary transfer device 45. In this embodiment, a positive secondary transfer voltage is applied to the outer secondary transfer roller 45b, so that the negative toner image on the intermediate transfer belt 44b is secondary-transferred onto the recording material S, which is nipped and fed between the intermediate transfer belt 44b and the outer secondary transfer roller 45 b. The recording material S is fed from a feeding portion (not illustrated) in parallel with the above-described toner image forming operation, and the toner image on the intermediate transfer belt 44b is fed by the registration roller pair 11 provided in the feeding path at the adjusted timing. The sheet is then fed to the secondary transfer portion N.

As described above, the secondary transfer apparatus 45 includes the inner secondary transfer roller 45a as an opposing (counter) member, and the outer secondary transfer roller 45b (which is a roller-type secondary transfer member) as a secondary transfer portion. The inner secondary transfer roller 45a is disposed opposite to the outer secondary transfer roller 45b with the intermediate transfer belt 44b interposed therebetween. A secondary transfer power source 76 (fig. 2) as an applying member is connected to the outer secondary transfer roller 45 b. During the secondary transfer process, the secondary transfer power supply 76 applies a DC voltage having a polarity (positive in this embodiment) opposite to the normal charging polarity of the toner as a secondary transfer bias (secondary transfer voltage) to the outer secondary transfer roller 45 b. The secondary transfer power source 76 is connected to a voltage detection sensor 76a for detecting an output voltage and a current detection sensor 76b (fig. 2) for detecting an output current. The core of the inner secondary transfer roller 45a is connected to the ground potential. Also, when the recording material S is supplied to the secondary transfer portion N, a secondary transfer voltage having a polarity opposite to the normal charging polarity of the toner, which is controlled at a constant voltage, is applied to the outer secondary transfer roller 45 b. In this embodiment, for example, a secondary transfer voltage of 1kV to 7kV is applied, a current of 40 μ a to 120 μ a is applied, and the toner image on the intermediate transfer belt 44b is secondary-transferred onto the recording material S. Here, in this embodiment, an alternative connection is that the inner secondary transfer roller 45a is connected to the ground potential, and a voltage is applied from the secondary transfer power supply 76 to the outer secondary transfer roller 45 b. On the other hand, a voltage from the secondary transfer power source 76 is applied to the inner secondary transfer roller 45a as the secondary transfer member, and the outer secondary transfer roller 45b as the opposing member is connected to the ground potential. In this case, a DC voltage having the same polarity as the normal charging polarity of the toner is applied to the inner secondary transfer roller 45 a.

In this embodiment, the outer secondary transfer roller 45b has a core metal and an elastic layer of ion conductive foam rubber (NBR rubber). The outer diameter of the outer secondary transfer roller 45b is, for example, 20mm to 25 mm. furthermore, as the outer secondary transfer roller 45b, a roller having 1 × 10 can be preferably used⁵Omega to 1 × 10⁸A roller having a resistance value of Ω (measured under N/N (23 ℃, 50% RH), applied at 2 kV).

The recording material S to which the toner image has been transferred is fed to a fixing portion 46 as a fixing member. The fixing section 46 includes a fixing roller 46a and a pressure roller 46 b. The fixing roller 46a includes therein a heater as a heating member. The recording material S carrying the unfixed toner image is heated and pressurized by being nipped and fed between the fixing roller 46a and the pressing roller 46 b. Thereby, the toner image is fixed (fused and fixed) on the recording material S. Here, the temperature (fixing temperature) of the fixing roller 46a is detected by a fixing temperature sensor 77 (fig. 2).

The recording material S to which the toner image is fixed is fed through a discharge path in a discharge portion (not illustrated), discharged through a discharge port, and then stacked on a discharge tray provided outside the apparatus main assembly 10. Further, between the fixing portion 46 and the discharge port of the discharge portion, there is a reverse feeding path (not shown) for reversing the recording material S on which the toner image is fixed on the first surface and for supplying the recording material S to the secondary transfer portion N again. The recording material S resupplied to the secondary transfer portion N by the operation of the reverse feeding path is discharged to the outside of the apparatus main assembly 10 after the toner image is transferred and fixed at the second side. As described above, the image forming apparatus 1 of this embodiment is capable of performing automatic duplex printing in which images are formed on both sides of a single recording material S.

The surface of the photosensitive drum 51 after the primary transfer is discharged by the pre-exposure device 54. Further, the toner (primary untransferred residual toner) remaining on the photosensitive drum 51 without being transferred onto the intermediate transfer belt 44b during the primary transfer process is removed from the surface of the photosensitive drum 51 by the cleaning blade 55 and collected in a collection container (not shown). The cleaning blade 55 is a plate-like member that is in contact with the photosensitive drum 51 with a predetermined pressure. The cleaning blade 55 is in contact with the surface of the photosensitive drum 51 in the opposite direction of the upstream side of the rotation direction of the photosensitive drum 51 at the outer end portion of the free end portion. Further, toner (secondary untransferred residual toner) or adherent such as paper powder remaining on the intermediate transfer belt 44b without being transferred onto the recording material S during the secondary transfer process is removed from the surface of the intermediate transfer belt 44b by the belt cleaning device 60 and collected.

In an upper portion of the apparatus main assembly 10, an automatic original feeding device 81 and an image reading portion 80 are provided. The automatic original feeding device 81 automatically feeds a sheet (for example, a later-described drawing) such as an original or a recording material S on which an image is formed toward the image reading portion 80. The image reading portion 80 reads an image on a sheet fed by the automatic original feeding apparatus 81. The image reading portion 80 illuminates a sheet placed on a flat glass 82 with light from a light source (not shown), and is configured to read an image on the sheet at a predetermined dot density by an image reading element (not shown). That is, the image reading portion 80 optically reads an image on a sheet and converts the read image into an electric signal.

Fig. 2 is a block diagram showing a schematic configuration of a control system of the image forming apparatus 1 of this embodiment. As shown in fig. 2, the controller 30 is constituted by a computer, and includes, for example, a CPU 31, a ROM32 for storing programs for controlling each unit, a RAM33 for temporarily storing data, and an input/output circuit (I/F)34 for inputting/outputting signals to and from the outside. The CPU 31 is a microprocessor that controls the entire image forming apparatus 1, and is a main part of the system controller. The CPU 31 is connected to and exchanges signals with a feeding section (not shown), the image forming section 40, a discharging section (not shown), and an operating section 70 via the input/output circuit 34, and controls the operation of each of these sections. The ROM32 stores an image formation control sequence for forming an image on the recording material S. The controller 30 is connected to a charging bias power supply 73, a developing bias power supply 74, a primary transfer power supply 75, and a secondary transfer power supply 76, respectively, which are controlled by signals from the controller 30. Further, the controller 30 is connected to a temperature sensor 71, a humidity sensor 72, a voltage detection sensor 75a and a current detection sensor 75b of the primary transfer power supply 75, a voltage detection sensor 76a and a current detection sensor 76b of the secondary transfer power supply 76, and a fixing temperature sensor 77.

The operation section 70 includes: operation buttons as input means, and a display portion 70a including a liquid crystal panel as display means. Here, in this embodiment, the display unit 70a is configured as a touch panel, and also has a function as an input section. An operator such as a user and a service person can perform a job (a series of operations of forming and outputting an image or images on one or more recording materials S in response to a start instruction) by operating the operation portion 70. The controller 30 receives a signal from the operation section 70, and operates various devices of the image forming apparatus 1. The image forming apparatus 1 can also execute a job based on an image forming signal (image data, control command) supplied from an external device 200 such as a personal computer.

In this embodiment, the controller 30 includes an image formation pre-preparation processing section 31a, an ATVC processing section 31b, an image formation processing section 31c, and an adjustment processing section 31 d. Further, the controller 30 includes a primary transfer voltage storing/operating section 31e and a secondary transfer voltage storing/operating section 31 f. Here, each of these processing section and storage/operation section may be provided as one portion or a plurality of portions of the CPU 31 or the RAM 33. For example, the controller 30 (specifically, the image forming processing section 31c) may execute the print job as described above. Further, the controller 30 (specifically, the ATVC processing section 31b) may perform ATVC (set mode) for the primary transfer section and the secondary transfer section. The details of ATVC will be described hereinafter. Further, the controller 30 (specifically, the adjustment processing section 31d) may perform an operation in an adjustment mode for adjusting the set voltage of the secondary transfer voltage. The details of the adjustment mode will be described later.

Here, the image forming apparatus 1 executes a job (image output operation, print job) which is a series of operations of forming and outputting one image or a plurality of images on a single or a plurality of recording materials S started by one start instruction. In general, a job includes an image forming step, a pre-rotation step, a sheet (paper) spacing step in the case of forming images on a plurality of recording materials S, and a post-rotation step. In general, the image forming step is performed in the following period: in this period, the formation of an electrostatic image, the formation of a toner image, the primary transfer of the toner image, and the secondary transfer of the toner image, which actually form and output an image on the recording material S, are performed, and the image formation period (image formation period) refers to this period. Specifically, the timing during image formation differs between the positions at which the respective steps of electrostatic image formation, toner image formation, primary transfer of a toner image, and secondary transfer of a toner image are performed. The pre-rotation step is performed in a period of a preparatory operation before the image forming step from the input of the start instruction until the actual image formation is started. When images are continuously formed on a plurality of recording materials S (continuous image formation), the sheet spacing step is performed in a period corresponding to an interval between the recording material S and the subsequent recording material S. The post-rotation step is performed in a period of performing a post-operation (preparation operation) after the image forming step. The non-image-formation period (non-image-formation period) is a period other than the period of image formation (image-formation period), and includes periods of a pre-rotation step, a sheet interval step, a post-rotation step, and also includes a period of a pre-multiple-rotation step, which is a preparatory operation during turning on of a main switch (voltage source) of the image forming apparatus 1 or during recovery from a sleep state.

2. Control of secondary transfer voltage

Next, control of the secondary transfer voltage will be described. Fig. 3 is a flowchart showing an outline of a control process of the secondary transfer voltage in this embodiment. In general, the control of the secondary transfer voltage includes constant voltage control and constant current control, and in this embodiment, constant voltage control is used.

First, the controller 30 (image formation pre-preparation processing section 31a) causes the image forming section to start operation of a job when acquiring information on the job from the operation section 70 or the external device 200. In the information on the job, image information specified by the operator and information on the recording material S are included. In addition, in this embodiment, the information on the recording material S includes the size (width, length) of the recording material S on which an image is to be formed, information (thickness, basis weight, and the like) related to the thickness of the recording material S, and information related to the surface property of the recording material S, such as whether the recording material S is a coated paper. In particular, in this embodiment, the information on the recording material S includes information on the size of the recording material S and information on the kind of the recording material S (the kind of paper) such as "thin paper, plain paper, thick paper …" in relation to the thickness of the recording material S. Incidentally, the kind of the recording material S includes attributes based on general characteristics such as plain paper, thick paper, thin paper, glossy paper, coated paper, and any distinguishable information on the recording material S such as a manufacturer, a brand, a product number, a basis weight, a thickness, and the like. The controller 30 (image formation pre-preparation processing section 31a) writes the job information into the RAM33 (S102).

Next, the controller 30 (image formation pre-preparation processing section 31a) acquires environmental information detected by the temperature sensor 71 and the humidity sensor 72 (S103). In the ROM32, information showing a correlation between environmental information and a target current Itarget for transferring a toner image from the intermediate transfer belt 44b onto the recording material S is stored. The controller 30 (secondary transfer voltage storage/operation section 31f) acquires the target current Itarget corresponding to the environment from the information showing the correlation between the environment information and the target current Itarget based on the environment information read in S103. Then, the controller 30 writes the target current Itarget in the RAM33 (or the secondary transfer voltage storage/operation section 31f) (S104). Incidentally, why the target current Itarget changes depending on the environmental information is because the toner charge amount changes depending on the environment. Information showing the correlation between the environmental information and the target current Itarget has been acquired in advance through experiments or the like.

Next, the controller 30(ATVC processing section 31b) acquires information on the resistance of the secondary transfer section N by ATVC (active transfer voltage control) before the toner image on the intermediate transfer belt 44b and the recording material S to which the toner image is transferred reach the secondary transfer section N (S105). That is, in a state where the external secondary transfer roller 45b and the intermediate transfer belt 44b are in contact with each other, predetermined voltages of a plurality of levels are applied (supplied) from the secondary transfer voltage source 76 to the external secondary transfer roller 45 b. Then, the current value at the time of application of the predetermined voltage is detected by the current detection sensor 76b so that the relationship between the voltage and the current (voltage-current characteristic) as shown in fig. 4 is obtained. The controller 30 writes information on such a relationship between the voltage and the current in the RAM33 (or the secondary transfer voltage storage/operation section 31 f). This relationship between the voltage and the current changes depending on the resistance of the secondary transfer portion N. In the configuration of this embodiment, the relationship between the voltage and the current does not cause the current to change linearly with respect to the voltage (i.e., the current is linearly proportional to the voltage), but causes the current to change so as to be represented by a polynomial composed of two or more voltage terms. For this reason, in this embodiment, in order that the relationship between the voltage and the current may be expressed by a polynomial expression, the number of predetermined voltages or currents supplied at the time of acquiring the information on the resistance of the secondary transfer portion N is three or more (levels).

Then, the controller 30 (secondary transfer voltage storing/operating section 31f) acquires a voltage value to be applied to the external secondary transfer roller 45b from the secondary transfer voltage source 76 (S106). That is, based on the target current Itarget written in the RAM33 in S104 and the relationship between the voltage and the current acquired in S105, the controller 30 acquires the voltage value Vb necessary for flowing the target current Itarget in a state where the recording material S is not present in the secondary transfer portion N. The voltage value Vb corresponds to a secondary transfer portion voltage (transfer voltage corresponding to the resistance of the secondary transfer portion N). In addition, in the ROM32, information for acquiring a recording material partial voltage (transfer voltage corresponding to the resistance of the recording material S) Vp is as shown in fig. 5. In this embodiment, the information is set as table data indicating the relationship between the water content in the ambient atmosphere and the recording material partial voltage Vp for each section (corresponding to the paper kind category) of the basis weight of the recording material S. Incidentally, the controller 30 (image formation pre-preparation processing section 31a) can acquire the ambient water content based on the environmental information (temperature, humidity) detected by the temperature sensor 71 and the humidity sensor 72. Based on the information on the job acquired in S101 and the environmental information acquired in S103, the controller 30 acquires the recording material portion voltage Vp from the above table data. In addition, in the case where the adjustment value is set by an operation in an adjustment mode for setting a setting voltage of the secondary transfer voltage described later, the adjustment value Δ V depends on the adjustment value. As will be described later, in the case where the adjustment value is set by the operation in the adjustment mode, this adjustment value Δ V is stored in the RAM33 (or the secondary transfer voltage storage/operation section 31 f). The controller 30 acquires Vb + Vp + Δ V, which is the sum of the above-described voltage values Vb, Vp, and Δ V, as a secondary transfer voltage Vtr applied from the secondary transfer voltage source 76 to the external secondary transfer roller 45b when the recording medium S passes through the secondary transfer portion N. Then, the controller 30 writes the Vtr (═ Vb + Vp + Δ V) in the RAM33 (or the secondary transfer voltage storing/operating section 31 f). Incidentally, table data for acquiring the recording material partial voltage Vp as shown in fig. 5 is acquired in advance by an experiment or the like.

Here, in some cases, the recording material partial voltage Vp is changed depending on the surface property of the recording material S in addition to information (thickness, basis weight, and the like) related to the thickness of the recording material S. For this reason, the table data may also be set so that the recording material partial voltage Vp also changes depending on the information relating to the surface property of the recording material S. In addition, in this embodiment, information related to the thickness of the recording material S (and, in addition, information related to the surface property of the recording material S) is included in the job information acquired in S101. However, a measuring means for detecting the thickness of the recording material S and the surface property of the recording material S is provided in the image forming apparatus 1, and the recording material partial voltage Vp may also be acquired based on information acquired by the measuring means.

Next, the controller 30 (image forming process section 31c) causes the image forming section to form an image and sends the recording material S to the secondary transfer section N, and causes the secondary transfer device to perform secondary transfer by applying the secondary transfer voltage Vtr determined as described above (S107). Thereafter, the controller 30 (image forming processing section 31c) repeats S107 until all the images in the job are transferred and completely output on the recording material S (S108).

Incidentally, regarding the primary transfer section 48, ATVC similar to the above-described ATVC is also performed in the period from the start of the job until the toner image is fed to the primary transfer section 48, but detailed description will be omitted in this embodiment.

3. Brief summary of simple adjustment modes

Next, an operation in a simple adjustment mode (hereinafter, simply referred to as "adjustment mode") for setting a setting voltage of the secondary transfer voltage will be described. Depending on the type and condition of the recording material S used in image formation, the kind water (moisture) content and the resistance value of the recording material S may be greatly different from those of the standard recording material S. In this case, in the case of using the setting voltage of the secondary transfer voltage of the default recording material portion voltage Vp set in advance as described above, the optimum transfer may not be performed.

That is, first, the secondary transfer voltage needs to be a voltage necessary for transferring the toner from the intermediate transfer belt 44b to the recording material S. Further, the secondary transfer voltage must be suppressed to a voltage level at which abnormal discharge does not occur. However, depending on the type and state of the recording material S actually used for image formation, the resistance may be higher than a value assumed as a standard value. In this case, in the case of using the set secondary transfer voltage of the preset default recording material portion voltage Vp, the voltage required to transfer the toner from the intermediate transfer belt 44b to the recording material S may be insufficient. Therefore, in this case, it is desirable to increase the setting voltage of the secondary transfer voltage by increasing the recording material partial voltage Vp. In contrast, depending on the type and condition of the recording material S actually used for image formation, the water (moisture) content of the recording material S may have increased, with the result that the resistance is lower than a value assumed as a standard value, and therefore discharge may occur. In this case, in the case of using the set voltage of the secondary transfer voltage of the preset default recording material portion voltage Vp, an image defect due to abnormal discharge may occur. Therefore, in this case, it is desirable to lower the setting voltage of the secondary transfer voltage by reducing the recording material partial voltage Vp.

Therefore, it is desirable for an operator such as a user or a service person to adjust (change) the recording material portion voltage Vp depending on, for example, the recording material S actually used for image formation to optimize the set voltage of the secondary transfer voltage during execution of the job. That is, it is desirable to select the optimum recording material portion voltage Vp + Vb (adjustment amount) depending on the recording material S actually used for image formation. This adjustment can be performed by the following method. That is, for example, the operator outputs an image while switching the secondary transfer voltage for each recording material S, and confirms the presence or absence of the occurrence of an image defect in the output image to obtain an optimum secondary transfer voltage, based on which the setting voltage of the optimum secondary transfer voltage (specifically, the recording material portion voltage Vp + Δ V) is determined. However, in this method, since the output operation of the image and the adjustment of the setting voltage of the secondary transfer voltage are repeated, the wasted recording material S increases, and it takes time in some cases.

In this embodiment, the image forming apparatus 1 is operable in an adjustment mode of adjusting the set voltage of the secondary transfer voltage. In the operation in the adjustment mode, a map in which a plurality of representative patches (test images, test patterns, test toner images) are formed is output on the recording material S actually used for image formation while switching the set voltage of the secondary transfer voltage (test voltage) for each patch. And, based on the result of the image reading section 80 reading the output chart, the optimum setting voltage (more specifically, the recording material portion voltage Vp + Δ V of the secondary transfer voltage) is determined. In particular, in this embodiment, information on the recommended adjustment amount Δ V of the setting voltage of the secondary transfer voltage for optimizing the density of the real image is presented based on the luminance information (density information) of the real (solid) block (real image block) on the map. Therefore, the necessity of the operator to confirm the presence or absence of the image defect by eye observation is reduced, so that it becomes possible to more appropriately adjust the setting of the secondary transfer voltage while reducing the operation burden of the operator.

However, as described above, at the set voltage of the secondary transfer voltage selected from the read result of the block, the absolute value of the secondary transfer voltage is excessively large and "white void" occurs in some cases. Since "white holes" are easily visualized in a halftone image, it is difficult to distinguish a difference between occurrence or non-occurrence of "white holes" as an image density.

Therefore, in this embodiment, when the setting voltage of the secondary transfer voltage is adjusted based on the luminance information of the block in the operation in the adjustment mode, the image forming apparatus 1 can limit the range of the adjustment amount. As will be described later in detail, it is known that the recording material portion voltage at which "white voids" are liable to occur has a correlation with information (thickness or basis weight) relating to the thickness of the recording material S. For this reason, in this embodiment, when the set voltage of the secondary transfer voltage is adjusted based on the luminance information of the block in the operation in the adjustment mode, the image forming apparatus 1 can limit the range of the adjustment amount based on the information on the thickness of the recording material S.

4. Drawing (A)

In this embodiment, in the operation in the adjustment mode, the luminance information of the block is acquired by reading the output map by the image reading section 80, and the recommended adjustment amount of the setting voltage of the secondary transfer voltage is presented. In particular, in this embodiment, a recommended adjustment amount of the setting voltage of the secondary transfer voltage for optimizing the real image density is presented based on the luminance information of the real block of the secondary color (blue in this embodiment). At this time, in this embodiment, by limiting the range of the adjustment amount of the setting voltage of the secondary transfer voltage based on the information on the thickness of the recording material S, it is possible to prevent the setting voltage from being adjusted to the setting voltage of the "white void" that is easily visualized in the halftone image. In addition, in this embodiment, the operator visually recognizes the outputted map in the operation in the adjustment mode, so that the adjustment amount presented as described above can also be changed. For this reason, in this embodiment, on the figure, a halftone block (halftone image block) is formed in addition to the solid block. Incidentally, in the case where a configuration in which the operator can change the adjustment amount is not adopted, the halftone block is not necessary.

When also considering confirming the output map by the operator through eye observation, the larger the block size of the map output in the adjustment mode is, the more advantageous, because it is then easier to check for image defects. However, if the blocks are large, the number of blocks that can be formed on one recording material S decreases. The block shape may be square, etc. The color of the block may be determined by the image defect to be inspected and the ease of inspection. For example, when the secondary transfer voltage is increased from a low value, the lower limit of the secondary transfer voltage may be determined from voltage values at which secondary patches such as red, green, and blue may be correctly transferred. Further, in the case where the operator observes the graph of the confirmation output by eyes, when the secondary transfer voltage is further increased, the upper limit value of the secondary transfer voltage may be determined from the voltage value at which an image failure (defect) occurs in the halftone block due to the high secondary transfer voltage.

A diagram that can be used with the adjustment mode in this embodiment will be described. In the adjustment mode in this embodiment, part (a) and part (B) of fig. 7 and two types of image data 100A and 100B shown in fig. 6 are used for the output of fig. 100. Fig. 6 shows chart image data (hereinafter also referred to as "large chart data") 100A output to a recording material S having a length in the feeding direction of 420mm to 487 mm. Fig. 7 shows the chart image data (hereinafter also referred to as "thumbnail data") output to the recording material S having a length in the feeding direction of 210mm to 419 mm. In this embodiment, as the map image data, only two types of image data shown in fig. 6 and 7 are set. Also, in the adjustment mode, a map corresponding to image data cut out from either of the two types of image data shown in fig. 6 and 7 depending on the size of the recording material S to be used is output on the recording material S. At this time, in this embodiment, image data having a size obtained by subtracting margins (margin) at the ends of the recording material S (in this embodiment, both ends in the thrust (perpendicular) direction and both ends in the feeding direction) from the image data shown in fig. 6 and 7 is cut out.

Here, in this embodiment, the maximum size (maximum sheet passing size) of the recording material S on which the image forming apparatus 1 can form an image is 13 inches × 19.2 inches (longitudinal feeding). Further, in the following description, the directions of the large drawing data 100A and the small drawing data 100B corresponding to the "feeding direction" and the "thrust direction (substantially perpendicular to the feeding direction)" of the recording material S are also referred to as the "feeding direction" and the "thrust direction", respectively.

The large map data 100A shown in fig. 6 will be further described. The large map data 100A corresponds to the maximum sheet passing size of the image forming apparatus 1 of the embodiment, and the image size is approximately 13 inches (≈ 330mm) × 19.2 inches (≈ 487mm) on the short side (thrust direction). When the size of the recording material S is 13 inches × 19.2 inches (vertical feed) or less and is larger than the a3 size (vertical feed), a portion of the large map data 100A cut according to the size of the recording material S is output. That is, when the length of the recording material S in the feeding direction is 420mm to 487mm, the large map data 100A is used. At this time, in this embodiment, the image data is cut out from the large map data 100A in accordance with the size of the recording material S based on the leading end center. That is, the leading end portion in the feeding direction of the recording material S and the leading end portion (upper end portion) in the long side direction of the large map data 100A are aligned with each other, and the center in the thrust direction of the recording material S and the center in the short side direction of the large map data 100A are aligned with each other, and the image data is cut out from the large map data 100A. Further, at this time, in this embodiment, the image data is cut out from the large map data 100A so that a margin of 2.5mm is provided at the end portions of the recording material S (in this embodiment, both ends in the thrust direction and both ends in the feeding direction). For example, in the case where the chart 110 is output to a recording material S of a3 size (vertical feed) (short side 297mm × long side 420mm), image data of a size 292mm (short side) × 415mm (long side) is cut out from the large chart data 100A. And, an image corresponding to the cut-out image data is output on the a 3-sized recording material S with a margin of 2.5mm at each end with the leading end center as a reference position.

The large map data 100A includes one blue solid block 101, one black solid block 102, and two halftone blocks 103 (gray (black halftone) in this embodiment) arranged in the thrust direction. Also, the eleven block groups 101 to 103 in the thrust direction are arranged in the feeding direction. The blue solid 101 and the black solid 102 are each 25.7mm × 25.7mm squares (one side substantially parallel to the thrust direction). Further, each of the halftone blocks 103 at both ends has a width of 25.7mm in the feeding direction, and extends to an end of the large drawing data 100A in the thrust direction. Further, the interval of the block groups 101 to 103 in the feeding direction is 9.5 mm. The secondary transfer voltage is switched at a timing at which the portion on the graph corresponding to the interval passes through the secondary transfer section N. The 11 block groups 101 and 103 in the feeding direction of the large map data 100A are in the range of 387mm in the feeding direction so that they are within 415mm in length of the recording material S in the feeding direction when the size of the recording material S is a 3. Further, in this example, the large drawing data 100A includes identification information 104 for identifying the setting of the secondary transfer voltage applied to each block group in combination with each of the 11 block groups 101 to 103 in the feeding direction. In this embodiment, the identification information 104 corresponds to an adjusted (adjustment) value described later. In this embodiment, eleven pieces of identification information 104 (in this embodiment, -5 to 0 to +5) corresponding to eleven steps of secondary transfer voltage setting are set.

When the eye view of the operator is also taken into consideration, the size of the block is required to be large enough to allow the operator to easily determine whether there is an image defect. With regard to transferability of the blue solid block 101 and the black solid block 102, if the size of the block is small, it may be difficult to distinguish a defect, and therefore, the size of the block is preferably 10mm square or more, and 25mm square or more is more preferable. The image defect due to abnormal discharge occurring when the secondary transfer voltage is increased in the halftone block 103 is generally in the form of a white dot. Such image defects tend to be easily discernible even in small-sized images, as compared with the transferability of real images. However, if the image is not too small, it is easier to observe, and therefore, in this embodiment, the width of the halftone block 103 in the feeding direction is the same as the width of the blue solid block 101 and the black solid block 102 in the feeding direction. Further, the intervals of the block groups 101 to 103 in the feeding direction may be set so that the secondary transfer voltage can be switched.

Here, it is preferable to prevent the formation of lumps near the leading end and the trailing end of the recording material S in the feeding direction (for example, in a range of about 20mm to 30mm inward from the edge). The reason for this will be described. That is, in the end portion in the feeding direction of the recording material S, there may be an image defect occurring only at the leading end or the trailing end. This is because in this case, it may be difficult to determine whether an image defect has occurred because the secondary transfer voltage changes. The real image is an image having the maximum density level. Further, in this embodiment, when the amount of applied toner of the real image is 100%, the halftone image corresponds to an image having an amount of applied toner of 10% to 80%.

With the above-described large map data 100A, when the size of the recording material S becomes smaller than 13 inches (a3 size or larger), the lengths of the halftone blocks 103 in the thrust direction at both ends in the thrust direction become smaller. Further, with the large map data 100A as described above, when the size of the recording material S becomes smaller than 13 inches (however, a3 size or larger), the margin at the trailing end in the feeding direction becomes small.

The small map data 100B shown in fig. 7 will be further described. The thumbnail data 100B corresponds to a size smaller than the a3 size, and the image size is approximately 13 inches (≈ 330mm) × 210mm on the short side (feeding direction) on the long side (thrust direction). If the size of the recording material S is a5 (short side 148mm × long side 210mm) (longitudinal feeding) or more and is smaller than A3 size (longitudinal feeding), a map corresponding to image data cut out from the small map data 100B depending on the size of the recording material S is output. That is, when the length of the recording material S in the feeding direction is 210mm to 419mm, the thumbnail data 100B is used. At this time, in this embodiment, image data is cut out from the small map data 100B in accordance with the size of the recording material S based on the leading end center. Further, at this time, in this example, as with the large image data 100A, the image data is cut out from the small image data 100B so as to be provided with a margin of 2.5mm at the end portions of the recording material S (in this embodiment, both ends in the thrust direction and both ends in the feeding direction). As will be described later, the length of the small map data 100B in the feeding direction is smaller than that of the large map data 100A, and therefore, the number of block groups that can be arranged in the feeding direction is smaller than that of the large map data 100A. Therefore, when the small map data 100B is used, two maps are output so as to increase the number of blocks.

The small map data 100B has the same blocks as those of the large map data 100A. Also, in the small drawing data, the five block groups 101 to 103 in the thrust direction are arranged in the feeding direction. The five block groups 101 to 103 in the feeding direction of the thumbnail data 100B are arranged in a range of 167mm in length in the feeding direction. Further, in this example, the thumbnail data 100B is provided with identification information 104 for identifying the setting of the secondary transfer voltage applied to each of the block groups in association with each of the five block groups 101 to 103 in the feeding direction. As described above, when the thumbnail data 100B is used, two maps are output. Also, on the first sheet, five pieces of identification information 104 (in this embodiment, -4 to 0) corresponding to the setting of the lower secondary transfer voltage in five steps are arranged based on the small map data 100B shown in part (a) of fig. 7. Further, on the second sheet, five (1 to 5 in this embodiment) pieces of identification information 104 corresponding to the higher fifth-order secondary transfer voltage settings are arranged based on the small map data 100B shown in part (B) of fig. 7.

Using the above-described small map data 100B, when the size of the recording material S becomes small (however, smaller than the A3 size and larger than the a5 size), the lengths of the halftone patches 103 in the thrust direction at both ends in the thrust direction become small. Further, with the thumbnail data 100B as described above, when the size of the recording material S becomes small (however, smaller than the A3 size and larger than the a5 size), the margin at the trailing end in the feeding direction becomes small.

Here, in this embodiment, by the operator' S input and designation on the operation section 70 or the external apparatus 200, not only the recording material S of the standard size but also the recording material S of an arbitrary size (a5 size or more, 13 inches × 19.2 inches or less) can be used.

5. Operation in adjustment mode

Fig. 8 is a flowchart showing an outline of the processing of the adjustment mode in this embodiment. Fig. 9 is a schematic diagram of an example of the setting screen. Here, as an example, a case where the operator performs the adjustment mode operation using the operation portion 70 of the image forming apparatus 1 will be described.

First, the operator selects the type and size of the recording material S using the adjustment mode (S1). At this time, the controller 30 (adjustment processing section 31d) causes the operation section 70 to display a setting screen (not shown) of the type and size of the recording material S. The controller 30 (adjustment processing section 31d) acquires information on the type and size of the recording material S specified by the operator in the operation section 70. Here, as for the information on the type and size of the recording material S, which is set in advance in association with the cassette, for example, the information may be acquired by selecting the cassette containing the feeding portion of the recording material S.

Next, the operator sets the center voltage value of the secondary transfer voltage applied at the time of image output, and whether to output the image to one side or both sides of the recording material S (S2). In this embodiment, in order to be able to adjust the secondary transfer voltage during secondary transfer to the front surface (first surface) and the back surface (second surface) in the duplex printing, the chart may also be output on both sides of the recording material S in the adjustment mode. Therefore, in this example, whether the image is to be output to one side or both sides of the recording material S can be selected, and the center voltage value of the secondary transfer voltage can also be set for each of the front and back sides of the recording material S. At this time, the controller 30 (adjustment processing section 31d) causes the operation section 70 to display an adjustment mode setting screen 90 as shown in fig. 9. The setting screen 90 includes a voltage setting unit 91, and the voltage setting unit 91 sets the center voltage value of the secondary transfer voltage for the front surface and the back surface of the recording material S. The setting screen 90 also includes an output surface selection unit 92, and the output surface selection unit 92 selects whether to output the image to one surface or both surfaces of the recording material S. Further, the setting screen 90 includes an output instructing section (test sheet output button) 93 for instructing output of a map, a confirming section 94(OK button 94a or application button 94b) for confirming a setting, and a cancel button 95 for canceling a setting change. When the adjustment value 0 is selected in the voltage setting portion 91, a preset voltage (more specifically, a recording material portion voltage Vp) set in advance for the currently selected recording material S is selected. Also, a case will be considered where the adjustment value 0 is selected, in which case 11 block groups from-5 to 0 to +5 when large picture data is used and 10 block groups from-4 to 0 to +5 when small picture data is used are switched and applied as secondary transfer voltages. In this embodiment, description will be made on the assumption that large map data is used and a map including 11 block groups is output. In this embodiment, the difference between the secondary transfer voltages for one level is 150V. The controller 30 (adjustment processing section 31d) acquires information related to the setting such as the center voltage value set through the setting screen 90 in the operation section 70.

Next, when the output instructing portion 93 on the setting screen 90 is selected by the operator, the controller 30 (the adjustment processing portion 31d) acquires information on the resistance of the secondary transfer portion N when the recording material S is not present in the secondary transfer portion N (S3). In this embodiment, the controller 30 (adjustment processing section 31d) acquires a polynomial (a quadratic expression in this embodiment) of two or more terms (terms of second order or more) regarding the voltage-current relationship depending on the resistance of the secondary transfer section N by an operation similar to that in the above-described ATVC. The controller 30 (adjustment processing section 31d) writes information on the voltage-current relationship into the RAM33 (or the adjustment processing section 31 d).

Then, the controller 30 (adjustment processing section 31d) causes the image forming apparatus to output the map (S4). At this time, the controller 30 (adjustment processing section 31d) cuts out the chart data as described above based on the size information of the recording material S acquired in S1, and causes the image forming apparatus to output the chart transferred with 11 block groups while changing the secondary transfer voltage every 150V. For example, it is assumed that the recording material portion voltage is 2500V in the current environment, and the secondary transfer portion voltage Vb obtained from the result of ATVC is 1000V. In this case, from 2650V to 4250V, the graph transferred with 11 block groups was output while changing the secondary transfer voltage every 150V. At this time, the controller 30 (adjustment processing section 31d) causes the current detection sensor 76b to detect the values of the currents flowing during the application of the voltages of the respective voltage levels, and acquires information on the recording material S when the recording material S is present in the secondary transfer section N and the resistance of the secondary transfer section N (S5). In this embodiment, the controller 30 (adjustment processing section 31d) acquires a polynomial (secondary expression in this embodiment) of two or more terms regarding the voltage-current relationship depending on the resistances of the secondary transfer section N and the recording material S from the detection results of the currents for the voltages of 11 levels. The controller 30 (adjustment processing section 31d) writes information on the voltage-current relationship in the RAM33 (or the adjustment processing section 31 d). Incidentally, the current when the recording material S is present in the secondary transfer portion N may be detected generally during transfer of the patch, but may also be detected at portions of the recording material S before and after the patch without toner for each voltage level.

Then, the controller 30 (adjustment processing section 31d) acquires the recording material partial voltage vp (N) at each voltage level from the relationship (secondary expression) between the voltage and the current when the recording material S is present in the secondary transfer section N acquired in S5 and from the relationship (secondary expression) between the voltage and the current when the recording material S is not present in the secondary transfer section N acquired in S3 (S6). Here, n denotes each voltage level, and in this embodiment, n ranges from 1 to 11, corresponding to 11 levels (11 block groups). In addition, the voltage value of each voltage level is denoted by vtr (n). In addition, a voltage value calculated by applying each level to the relationship (secondary expression) between the voltage and the current when the recording material S is not present in the secondary transfer portion N acquired in S3 is represented by vb (N). At this time, the recording material partial voltage vp (n) at each voltage level is represented by the following equation: vp (n) ═ vtr (n) -vb (n).

Then, the output chart is supplied to the image reading section 80 by using, for example, the automatic original feeding device 81, so that the image reading section 80 reads the chart (S7). At this time, the image reading section 80 is controlled by the controller 30 (adjustment processing section 31d), and in this embodiment, RGB luminance data (8 bits) of each real blue block on the drawing is acquired. Incidentally, when outputting the map, the controller 30 (adjustment processing section 31d) can cause the operation section 70 to display a message prompting the operator to supply the output map to the image reading section 80. Next, the controller 30 (adjustment processing section 31d) acquires an average value of the luminance values of the respective blocks by using the luminance data (density data) acquired in S7 (S8). By way of example, with this processing of S8, the average value of the luminance values of the blocks corresponding to the respective voltage levels is as shown in fig. 10. In fig. 10, the abscissa represents (adjustment) values (-5 to 0 and 0 to +5) showing adjustment of respective voltage levels, and the ordinate represents the average value of luminance values of real blue patches. Incidentally, as for the real blue patch, luminance data of B is used.

Then, the controller 30 (adjustment processing section 31d) acquires an adjustment value of the recommended adjustment amount Δ V showing the setting voltage of the secondary transfer voltage based on the recording material partial voltage vp (n) acquired in S6 and the average value of the luminance acquired in S8 (S9).

Here, the process of acquiring the adjustment value in S9 will be specifically described. Fig. 11 is a graph showing an outline of the thickness of the recording material S, the recording material partial voltage of the secondary transfer voltage, and the tendency of occurrence of "white voids". As shown in fig. 11, the result is that the absolute value of the recording material partial voltage at which "white voids" occur becomes larger as the thickness of the recording material S becomes thicker. According to the study of the present inventors, the partial voltage of the recording material at which "white voids" are liable to occur well agrees with the discharge start voltage obtained from the Paschen curve in the case where the thickness of the recording material S is considered to be air (gap). That is, the relationship shown in fig. 11 coincides with the cause of occurrence of the "white void", so that the recording material S is discharged during the secondary transfer, and the charge polarity of the toner at the discharged portion is reversed and thus is not transferred onto the recording material S. Therefore, in this embodiment, by utilizing the above-described correlation, the upper limit of the recording material partial voltage is set depending on the information on the thickness of the recording material S. Therefore, it becomes possible to select the adjustment value of the set voltage of the secondary transfer voltage within a range in which the occurrence of the "white void" can be suppressed.

Specifically, in this embodiment, the controller 30 (adjustment processing section 31d) extracts a value not exceeding the upper limit set depending on the information on the thickness of the recording material S from the recording material partial voltage vp (n) acquired in S6. In this embodiment, the relationship between the kind (paper type) of each recording material S such as "thin paper, plain paper, thick paper 1, thick paper 2.." the information on the thickness of the recording material S (basis weight in this embodiment) and the upper limit of the recording material portion voltage vp (n) is acquired in advance. The relationship between the kind of the recording material S and the recording material partial voltage vp (n) is stored in the ROM32 as table data as shown in fig. 12. The controller 30 (adjustment processing section 31d) refers to the table data of fig. 12 and acquires the upper limit of the recording material partial voltage vp (n) corresponding to the type of the recording material S acquired in S1.

Fig. 13 is a diagram for illustrating the process of acquiring the adjustment value in S9. Part (a) of fig. 13 shows the relationship between the adjustment values (-5 to 0 and 9 to +5) indicating each voltage level and the recording material partial voltage vp (n) acquired in S6. Part (b) of fig. 13 shows the relationship between the adjustment values (-5 to 0 and 0 to +5) indicating each voltage level and the average value of the luminance of the real blue patch acquired in S8. For example, in the example of part (a) of fig. 13, in the case where the upper limit of the recording material partial voltage vp (n) is 2200V, the controller 30 (adjustment processing section 31d) extracts-5 to 0 as the adjustment value. Incidentally, the term "extraction" includes not only adopting one applicable to the predetermined condition as an option but also excluding one not applicable to the predetermined condition from the options. In addition, the controller 30 determines, as the adjustment value of the recommended adjustment amount Δ V indicating the set value of the secondary transfer voltage, an adjustment value at which the average value of the luminance of the corresponding block is minimum (i.e., the image density is maximum) among the adjustment values judged that the recording material portion voltage vp (n) does not exceed the upper limit. For example, in the example of part (b) of fig. 13, the controller 30 (adjustment processing section 31d) determines-1, which is the minimum average value of the luminances of the corresponding blocks out of-5 to 0 extracted as described above, as the adjustment value indicating the recommended adjustment amount Δ V. Incidentally, the case where the average value of the luminance is minimum corresponds to the case where the average value of the density is maximum.

Here, in the case where the adjustment value for setting the secondary transfer voltage is determined based only on the block luminance data as in the conventional configuration, the luminance data becomes minimum at a value not less than the upper limit of the recording material portion voltage in some cases, so that there is a tendency that: the adjustment amount for which there is a possibility of occurrence of "white holes" is determined. On the other hand, according to this embodiment, the adjustment amount in which there is a possibility of occurrence of "white holes" is avoided, so that an appropriate adjustment amount can be determined.

Next, the controller 30 (adjustment processing section 31d) causes the operation section 70 to display the adjustment value acquired in S9 on the setting screen 90 (voltage setting section 91) as shown in fig. 9 (S10). The operator can determine whether or not the displayed adjustment value is appropriate based on the output map and the display content of the setting screen 90. If the displayed adjustment value is not changed, the operator selects the completion unit 94(OK button 94a, application button 94b) of the setting screen 90 as it is. On the other hand, when the operator desires to change the adjustment value from the displayed adjustment value, the operator inputs the desired value to the voltage setting portion 91 of the setting screen 90, and then selects the completion portion 94(OK button 94a, application button 94 b). In a case where the adjustment value is not changed and the completion section 94 is selected (S11), the controller 30 (adjustment processing section 31d) causes the RAM33 (or the secondary transfer voltage storing/operating section 31f) to store the adjustment value determined in S9 (S12). On the other hand, when the adjustment value is changed (S11), the controller 30 (adjustment processing section 31d) causes the RAM33 (or the secondary transfer voltage storage/operation section 31f) to store the adjustment value input by the operator (S13). The operation in the adjustment mode is thus ended.

During execution of the subsequent job, the controller 30 calculates the adjustment amount Δ V as the adjustment value × 150V depending on the adjustment value stored in the operation in the adjustment mode until the operation in the adjustment mode is subsequently executed, and uses the calculated value in the calculation of the secondary transfer voltage Vtr during normal image formation.

Incidentally, the information on the upper limit of the recording material partial voltage vp (n) used in the above-described S9 is not limited to be used in the setting as the table data as in this embodiment. For example, a relational expression showing a relationship between information on the thickness of the recording material S and the recording material portion voltage vp (n) at which "white voids" are liable to occur is acquired in advance, and may be stored in the ROM 32. In this case, information on the thickness is acquired, and the upper limit of the recording material partial voltage vp (n) may be acquired from the above-described relational expression.

In addition, the information on the thickness of the recording material S is not limited to the classification by the kind of the recording material S. For example, in the above-described S1, the operator can directly input a value relating to the thickness of the recording material S, such as the thickness or the basis weight. In addition, in the step corresponding to S1, a value relating to the thickness of the recording material S, such as the thickness or the basis weight, may also be acquired by the measuring means for measuring a value relating to the thickness of the recording material S. As the measuring means, for example, a known thickness sensor using ultrasonic waves may be provided on the upstream side of the secondary transfer portion N with respect to the feeding direction of the recording material S.

In this embodiment, a real blue block is used as a block for acquiring luminance data, but is not limited thereto. For example, instead of solid blue patches, solid patches of red or green as a secondary color may be used, and solid patches of a single color of yellow, magenta, cyan, or black may be used.

In this embodiment, as an example, a case where an operation by the operator is performed through the operation section 70 of the image forming apparatus 1 and thus an operation in the adjustment mode is performed is described, but an operation in the adjustment mode may also be performed through an operation through the external device 20 such as a personal computer. In this case, a setting similar to the above-described setting may be performed by a driver for the image forming apparatus 1 installed in the external device 200 through a setting screen displayed at the display portion of the external device 200.

In this embodiment, information on the resistance of the secondary transfer portion N from the start of the operation in the adjustment mode when the recording material S is not present in the secondary transfer portion N is acquired. Therefore, information on the resistance of the secondary transfer portion N that coincides with the case when the adjustment amount for setting the secondary transfer voltage is acquired can be acquired. However, if allowed from the viewpoint of accuracy or the like, as the information on the resistance of the secondary transfer portion N, for example, the result of ATVC at the start of the last job of performing the operation in the adjustment mode may also be used.

In this embodiment, in the operation in the adjustment mode, the control of the display using the adjustment value corresponding to the adjustment amount Δ V is performed, but the control of the display using the adjustment value Δ V more directly may be performed.

In this embodiment, when the voltage-current relationship is acquired, the value of the current flowing during the supply of the predetermined voltage is detected, but the value of the voltage generated during the supply of the predetermined current value may also be detected. In this embodiment, the constant voltage control is described as an example, but the present invention can also be applied to a configuration using the constant current control.

As described above, the image forming apparatus 1 of this embodiment includes the detecting means 76a and 76b for detecting the current value or the voltage value when the voltage is applied from the voltage source 76 to the transfer member 45b, and includes the acquiring means 80 for acquiring the information on the density of the image on the recording material S. In addition, the image forming apparatus 1 includes a controller 30, and the controller 30 is capable of performing operations in: the test image output thereon is transferred to the chart 100 on the recording material S by applying a plurality of different test voltages from the voltage source 76 to the transfer member 45 and the transfer voltage applied to the transfer member 45b when the recording material S passes through the transfer section N during image formation is set based on the detection result of the chart 100 by the acquisition means 80. During the operation in the above-described mode, the controller 30 sets the transfer voltage based on the detection results of the detecting members 76a and 76b when a plurality of test voltages are applied to the transfer member 45b when the chart 100 is present in the transfer section N. In this embodiment, in the operation in the above-described adjustment mode, the controller 30 sets the transfer voltage based on the first detection results of the detecting members 76a and 76b in the case where the voltage is applied to the transfer member 45b when the recording material S is not present in the transfer portion N, and the second detection results of the detecting members 76a and 76b in the case where a plurality of voltages are applied to the transfer member 45b when the recording material S is present in the transfer portion N.

In this embodiment, during the operation in this mode, the controller 30 sets the transfer voltage based on the information on the thickness of the recording material S for outputting the chart 100. Specifically, the controller 30 sets the transfer voltage in the following manner. That is, the information on the voltage-current characteristics is acquired based on the detection results of the detecting members 76a and 76b acquired in the case where voltages of a plurality of levels are applied from the power source 76 to the transfer member 45b when the recording material S is not present in the transfer portion N. In addition, the transfer portion voltage corresponding to each of the plurality of test voltages is acquired based on each of the plurality of current values detected by the detecting members 76a and 76b corresponding to the associated one of the plurality of test voltages applied to the transfer member 45b when the recording material S is present in the transfer portion N during the output of the graph 100 and the voltage-current characteristic. Then, among the plurality of test voltages, a single or a plurality of voltages that can be reflected in the transfer voltage are extracted based on the information on the thickness of the recording material S for outputting the graph 100 and the information (fig. 12) showing the relationship between the information on the thickness of the recording material S and the upper limit on the difference between the plurality of test voltages and the transfer portion voltage corresponding to the plurality of test voltages. Then, from the extracted voltages, transfer voltages are set based on information on densities acquired from the associated test images 101. In this embodiment, among the extracted set values, the controller 30 sets the transfer voltage based on the voltage value when the acquired density of the associated test image is maximum.

In this embodiment, the second detection result is the detection result of the detecting members 76a and 76b acquired when the test image 101 is transferred onto the recording material S. In addition, in this embodiment, the first detection result is the detection results of the detection members 76a and 76b acquired when the recording material S is not present in the transfer portion N in the period from the instruction input to the controller of the output chart 100 until the output chart. During the operation in the above-described mode, the controller 30 can perform a process of notifying the operator of information about the set transfer voltage. In addition, during operation in this mode, the controller 30 can receive an instruction to change the transfer voltage set by the controller 30. Further, the information on the thickness may also be information on the thickness of the recording material S, the basis weight of the recording material S, or information on the kind of the recording material S based on the thickness or the basis weight.

As described above, according to this embodiment, in the configuration in which the operation in the adjustment mode is performed so that the map in which the blocks are formed is output and then the setting of the secondary transfer voltage is adjusted, it becomes possible to adjust the setting of the secondary transfer voltage more appropriately.

[ example 2]

Next, another embodiment of the present invention will be described.

The basic structure and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of embodiment 1. Therefore, with the image forming apparatus of this embodiment, elements including functions or structures identical to or corresponding to those of the image forming apparatus of embodiment 1 are denoted by the same reference numerals or symbols as those of embodiment 1, and detailed description thereof is omitted for the sake of simplicity.

In embodiment 1, the acquisition means for acquiring the block luminance information (density information) is an image reading portion 80, and the image discharged from the image forming apparatus 1 is supplied to the image reading portion 80 by the operator. On the other hand, in this embodiment, the acquisition means acquires the block luminance information (density information) when the chart is discharged from the image forming apparatus 1.

Fig. 14 is a schematic sectional view of the image forming apparatus 1 according to this embodiment. The image forming apparatus 1 of this embodiment includes an in-line image sensor 12 serving as a reading portion for reading an image on a recording material S, the in-line image sensor 12 being disposed downstream of a fixing portion 46 in a feeding direction of the recording material S. In this embodiment, the structure is such that the image sensor 12 can read the image density of an image on the recording material S, particularly the image density (luminance) of a block on the figure, at 1200dpi (i.e., it can convert optically acquired information into an electric signal).

The operation in the adjustment mode in this embodiment is similar to that in embodiment 1 except that instead of supplying the chart to the image reading section 80 after the chart is discharged from the image forming apparatus 1, the chart is read by the image sensor 12. The image sensor 12 may also be a spectral sensor, and the image density may also be calculated from spectral data of the image.

According to this embodiment, the same effects as those of embodiment 1 can be provided, and the operation burden on the operator can be reduced more than that of embodiment 1.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.