阅读说明：本技术 图像形成装置 (Image forming apparatus with a toner supply device ) 是由 西田聪 冈野信彦 山口洋 石田雄二郎 于 2021-05-31 设计创作，主要内容包括：在本发明的图像形成装置中,通过抑制进行压接的两个旋转部件的表面速度差,从而抑制加工质量的劣化。图像形成装置的控制部获取二次转印带相对于转印了调色剂像的中间转印带分离时和压接时的二次转印带的速度变化,并基于获取的速度变化,设定二次转印带的目标速度。(In the image forming apparatus of the present invention, deterioration of processing quality is suppressed by suppressing a difference in surface speeds of two rotating members which are brought into pressure contact with each other. A control unit of the image forming apparatus acquires a change in speed of the secondary transfer belt between a separation state and a contact state of the secondary transfer belt with respect to the intermediate transfer belt to which the toner image has been transferred, and sets a target speed of the secondary transfer belt based on the acquired change in speed.)

1. An image forming apparatus includes:

a first rotating member; and

a second rotating member which is capable of being pressed against and separated from the first rotating member,

wherein the image forming apparatus includes:

and a control unit that sets a target speed of the second rotating member based on a speed change of the second rotating member when the second rotating member is separated from the first rotating member and when the second rotating member is pressed against the first rotating member.

2. The image forming apparatus as claimed in claim 1,

the control unit acquires speed information of the second rotating member at the time of separation from the first rotating member and at the time of pressure contact, and determines a speed of the second rotating member having a surface speed that matches the first rotating member based on the acquired speed information and sets the speed as the target speed.

3. The image forming apparatus according to claim 1 or 2,

the control unit is capable of performing constant speed control for rotationally driving the second rotating member at a constant speed and constant torque control for rotationally driving the second rotating member at a constant torque, the constant speed control being performed in a state where the second rotating member is separated from the first rotating member, and the constant torque control being performed in a state where the second rotating member is pressed against the first rotating member based on the constant speed drive torque detected at that time.

4. The image forming apparatus according to any one of claims 1 to 3,

the control part

Rotating the first rotating member at a constant speed;

the first speed is changed and the following actions are performed a plurality of times: an operation of driving the second rotating member at the first speed in a state where the second rotating member is separated from the first rotating member, then crimping the second rotating member to the first rotating member, and acquiring a speed of the second rotating member in a crimped state;

setting a target speed of the second rotating member based on the first speed and the acquired speed.

5. The image forming apparatus according to claim 4,

the control unit drives the second rotating member at least two speeds, which are faster than the first rotating member and slower than the first rotating member, acquires the speeds of the second rotating member at the time of separation and at the time of pressure contact, respectively, and sets a target speed of the second rotating member based on the acquired speeds.

6. The image forming apparatus according to claim 4,

the control unit sets the speed of the second rotating member acquired at the time of pressure welding to the next first speed, and performs the operation a plurality of times.

7. The image forming apparatus according to claim 6,

the control unit repeats the operation until a speed difference between the first speed and a speed of the second rotating member obtained at the time of pressure contact when the second rotating member is driven at the first speed is smaller than a predetermined threshold value.

8. The image forming apparatus according to any one of claims 1 to 7,

the first rotating member is a photosensitive body,

the second rotating member is a transfer member.

9. The image forming apparatus according to any one of claims 1 to 7,

the first rotating member is a photosensitive body,

the second rotating member is an intermediate transfer body.

10. The image forming apparatus according to any one of claims 1 to 7,

the first rotating member is an intermediate transfer body,

the second rotating member is a secondary transfer member.

11. The image forming apparatus according to any one of claims 1 to 7,

the first rotating member is a fixing upper member,

the second rotating member is a fixing lower member.

Technical Field

The present invention relates to an image forming apparatus.

Background

In recent years, image forming apparatuses having a plurality of functions such as a printer, a facsimile machine, a copier, and a multifunction machine have been widely used. In the image forming apparatus, a latent image is formed on a photoconductor based on image data, and the latent image is developed with a developing material and then transferred onto a sheet of paper directly or via an intermediate transfer belt. In image transfer, a transfer member including a transfer roller and a transfer belt is pressed against an image carrier including a photoreceptor and an intermediate transfer belt, and a sheet is inserted into a pressing portion (also referred to as a transfer nip portion) to transfer a toner image onto the sheet.

Although the transfer member can be driven to the image bearing member by being pressed against the rotationally driven image bearing member, when a load is applied to the transfer member, the driving becomes difficult, and a transfer section driving section for rotationally driving the transfer member may be required. For example, when a cleaning portion is provided to remove a toner image adhering to a transfer member, a blade or the like is pressed against the surface of the transfer member such as a transfer roller or a transfer belt, and thus a load is applied to the transfer member due to the pressing. Therefore, the image forming apparatus described above is provided with a transfer section driving section for driving the transfer member.

In the case where the image carrier and the transfer member are separately rotationally driven in this manner, it is necessary to avoid the influence of the rotation of the transfer member on the rotation of the image carrier from impairing the image forming accuracy.

Therefore, for example, in patent document 1, by controlling the driving force applied to the transfer member based on at least one of the usage history of the cleaning member and the amount of moisture in the air, the variation in the load applied to the image carrier by the rotation of the transfer member is reduced. Further, in patent document 1, a torque limiter is provided in a drive system of a transfer member, and while setting a limiter value as a load of the transfer member (mainly from a cleaning member) + α, the transfer member is set to rotate slightly faster than the image carrier, and the transfer member is slightly (+ α torque: a value in a range in which fluctuation due to periodic speed fluctuation or the like is not reversed) pressed against the image carrier in a pressure contact state of the transfer member, and the torque limiter is operated in this state, whereby the torque applied to the image carrier is made constant regardless of the presence or absence of a sheet on the transfer member.

However, when the transfer member is pressed against the image carrier (here, the intermediate transfer belt) and rotationally driven, the rotational diameter of the transfer member changes only by the thickness of the paper when the paper is passed through the press-contact portion. Thus, there are problems as follows: when the constant speed control is performed so that the transfer member rotates at a constant speed, the torque applied to the image carrier varies at the passing cycle of the paper, with the result that the image carrier varies in speed, thereby causing deterioration such as color difference (deterioration in color-register) performance, etc., to impair the image forming accuracy. Further, in the method using the torque limiter, there is a problem that the limiter value cannot be set when the variation (time/environment) of the load (mainly from the cleaning member) on the transfer member side is large.

To cope with such a torque variation of the transfer member or the like, for example, patent document 2 proposes an image forming apparatus in which, when the transfer member and the image bearing member are separated from each other, the transfer member and the image bearing member are subjected to constant speed control so that the rotational speeds of the transfer member and the image bearing member become constant speeds by feedback control, and when the transfer member and the image bearing member are pressed against each other, the transfer member is subjected to constant torque control by a constant speed drive torque at the time of constant speed control detected when the transfer member is separated from each other.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2008-304552

Patent document 2: japanese patent No. 5585770

Disclosure of Invention

Problems to be solved by the invention

However, there is a case where a difference in surface speed occurs between the image bearing member and the transfer member due to variations in the outer diameter of the driving roller of the image bearing member or the transfer member, or in the thickness of the image bearing member or the transfer member. In view of this speed difference, there is no technique for matching the surface speeds of the image carrier and the transfer member. Therefore, a difference in surface speed between the image bearing member and the transfer member may occur, and image deviation may occur at the time of transfer. As a result, a difference in surface speed between the two rotating bodies that are brought into pressure contact with each other due to component deviation or the like causes deterioration in processing quality, and the phenomenon occurs not only between the image bearing member and the transfer member but also between the photoreceptor and the transfer member, between the photoreceptor and the intermediate transfer belt, between the intermediate transfer belt and the secondary transfer member, and between the fixing upper member and the fixing lower member.

The invention aims to suppress deterioration of processing quality by suppressing a difference in surface speeds of two rotating members which are brought into pressure contact in an image forming apparatus.

Means for solving the problems

In order to solve the above problem, the invention according to claim 1 is an image forming apparatus including: a first rotating member; and a second rotating member which can be pressed against and separated from the first rotating member,

wherein the image forming apparatus includes:

and a control unit that sets a target speed of the second rotating member based on a speed change of the second rotating member when the second rotating member is separated from the first rotating member and when the second rotating member is pressed against the first rotating member.

The invention described in claim 2 is the invention described in claim 1, wherein,

the control unit acquires speed information of the second rotating member at the time of separation from the first rotating member and at the time of pressure contact, and determines a speed of the second rotating member having a surface speed that matches the first rotating member based on the acquired speed information and sets the speed as the target speed.

The invention described in claim 3 is the invention described in claim 1 or 2,

the control unit is capable of performing constant speed control for rotationally driving the second rotating member at a constant speed and constant torque control for rotationally driving the second rotating member at a constant torque, the constant speed control being performed in a state where the second rotating member is separated from the first rotating member, and the constant torque control being performed in a state where the second rotating member is pressed against the first rotating member based on the constant speed drive torque detected at that time.

The invention described in claim 4 is the invention described in any one of claims 1 to 3,

the control unit rotates the first rotating member at a constant speed; the first speed is changed and the following actions are performed a plurality of times: an operation of driving the second rotating member at the first speed in a state where the second rotating member is separated from the first rotating member, then crimping the second rotating member to the first rotating member, and acquiring a speed of the second rotating member in a crimped state; setting a target speed of the second rotating member based on the first speed and the acquired speed.

The invention described in claim 5 is the invention described in claim 4,

the control unit drives the second rotating member at least two speeds, which are faster than the first rotating member and slower than the first rotating member, acquires the speeds of the second rotating member at the time of separation and at the time of pressure contact, respectively, and sets a target speed of the second rotating member based on the acquired speeds.

The invention described in claim 6 is the invention described in claim 4, wherein,

the control unit sets the speed of the second rotating member acquired at the time of pressure welding to the next first speed, and performs the operation a plurality of times.

The invention described in claim 7 is the invention described in claim 6,

the control unit repeats the operation until a speed difference between the first speed and a speed of the second rotating member obtained at the time of pressure contact when the second rotating member is driven at the first speed is less than a predetermined threshold value.

The invention described in claim 8 is the invention described in any one of claims 1 to 7,

the first rotating member is a photoreceptor, and the second rotating member is a transfer member.

The invention described in claim 9 is the invention described in any one of claims 1 to 7,

the first rotating member is a photoreceptor, and the second rotating member is an intermediate transfer member.

The invention described in claim 10 is the invention described in any one of claims 1 to 7,

the first rotating member is an intermediate transfer member, and the second rotating member is a secondary transfer member.

The invention described in claim 11 is the invention described in any one of claims 1 to 7,

the first rotating member is an upper fixing member, and the second rotating member is a lower fixing member.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, in the image forming apparatus, since a difference in surface speed between the two rotating members that are brought into pressure contact with each other can be suppressed, deterioration in processing quality can be suppressed.

Drawings

Fig. 1 is a diagram showing a schematic configuration of an image forming apparatus to which an embodiment of the present invention is applied.

Fig. 2 is a block diagram showing a main functional configuration of the image forming apparatus.

Fig. 3(a) and 3(b) are diagrams showing the configuration of the periphery of the intermediate transfer belt and the secondary transfer belt.

Fig. 4 is a circuit block diagram relating to control of the intermediate transfer belt and the secondary transfer belt.

Fig. 5 is a flowchart showing a control process of the intermediate transfer belt and the secondary transfer belt by the control section.

Fig. 6 is a flowchart showing the flow of the target speed setting process a.

Fig. 7(a) is a graph showing a temporal change in the rotation speed of the secondary transfer drive motor in steps S11 to S15 of fig. 6, fig. 7(b) is a graph showing a temporal change in the rotation speed of the secondary transfer drive motor in steps S17 to S21 of fig. 6, and fig. 7(c) is a graph showing the graphs of fig. 7(a) and 7(b) superimposed.

Fig. 8 is a flowchart showing the flow of the target speed setting process B.

Description of the reference numerals

1 image forming apparatus

10 control part

11 storage section

12 operating part

13 display part

14 interface

15 scanner

16 image processing unit

17 image forming part

174 intermediate transfer belt

41 intermediate transfer drive roller

41a intermediate transfer drive motor

41b intermediate transfer drive transmission mechanism

42 intermediate transfer driven roller

61 Secondary transfer drive roller

61a Secondary transfer drive Motor

61b Secondary transfer drive Transmission mechanism

62 Secondary transfer follower roller

63 Secondary transfer printing belt

64 Secondary transfer cleaning part

64a cleaning blade

65 crimping/separating mechanism

65a press-fit/separation motor

65b press-contact/separation transfer mechanism

176 secondary transfer roller

18 fixing part

181 fixing upper member

182 fusing lower member

19 conveying part

21 bus

S paper

Detailed Description

An embodiment of an image forming apparatus according to the present invention will be described below with reference to the drawings. In addition, although the embodiments of the present invention have been described with reference to a color image forming apparatus as an example, the present invention is not limited to this, and can be applied to a monochrome image forming apparatus, for example.

< first embodiment >

(Structure of image Forming apparatus)

Fig. 1 is a diagram showing a schematic configuration of an image forming apparatus 1 according to a first embodiment of the present invention. Fig. 2 is a block diagram showing a main functional configuration of the image forming apparatus 1.

The image forming apparatus 1 includes: a control Unit 10 having a CPU101(Central Processing Unit), a RAM102(Random Access Memory), and a ROM103(Read Only Memory); a storage unit 11; an operation section 12; a display unit 13; an interface 14; a scanner 15; an image processing unit 16; an image forming unit 17; a fixing section 18, a conveying section 19, and the like.

The control unit 10 as a control means is connected to the storage unit 11, the operation unit 12, the display unit 13, the interface 14, the scanner 15, the image processing unit 16, the image forming unit 17, the fixing unit 18, and the conveying unit 19 via a bus 21.

The CPU101 reads and executes a control program stored in the ROM103 or the storage unit 11, and performs various arithmetic processes.

The RAM102 provides the CPU101 with a memory space for a job, and stores temporary data.

The ROM103 stores various control programs, setting data, and the like executed by the CPU 101. In addition, a rewritable nonvolatile Memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash Memory may be used instead of the ROM 103.

The control unit 10 including the CPU101, RAM102, and ROM103 collectively controls each unit of the image forming apparatus 1 in accordance with the various control programs described above. For example, the control unit 10 causes the image processing unit 16 to perform predetermined image processing on the image data and store the image data in the storage unit 11. The control unit 10 causes the transport unit 19 to transport the sheet, and forms an image on the sheet by the image forming unit 17 based on the image data stored in the storage unit 11.

The storage unit 11 is configured by a storage unit such as a DRAM (Dynamic Random Access Memory) or an HDD (Hard Disk Drive) as a semiconductor Memory, and stores image data acquired by the scanner 15, image data input from the outside via the interface 14, various setting information, and the like. These image data and the like may be stored in the RAM 102.

The operation unit 12 includes input devices such as operation keys and a touch panel arranged to overlap on the screen of the display unit 13, converts input operations to the input devices into operation signals, and outputs the operation signals to the control unit 10.

The display unit 13 includes a display device such as an LCD (Liquid crystal display), and displays an operation screen indicating the state of the image forming apparatus 1 and the contents of an input operation to the touch panel.

The interface 14 is a unit for transmitting and receiving data to and from an external computer, another image forming apparatus, or the like, and is configured by any of various serial interfaces, for example.

The scanner 15 reads an image formed on a sheet, generates image data including monochrome image data of each color component of R (red), G (green), and B (blue), and stores the image data in the storage unit 11.

The image processing unit 16 includes, for example, a rasterization processing unit, a color conversion unit, a gradation correction unit, and a halftone processing unit, and performs various image processing on the image data stored in the storage unit 11 and stores the image data in the storage unit 11.

The image forming unit 17 forms an image on a sheet based on the image data stored in the storage unit 11. The image forming unit 17 includes four sets of an exposure unit 171, a photoreceptor 172, and a developing unit 173, which correspond to color components of C (cyan), M (magenta), Y (yellow), and K (black), respectively. The image forming unit 17 includes an intermediate transfer belt (intermediate transfer body) 174 as an image carrier, a primary transfer roller 175, and a secondary transfer roller 176.

The exposure section 171 includes an LD (Laser Diode) as a light emitting element. The exposure section 171 drives the LD based on image data, irradiates laser light onto the charged photoreceptor 172, and exposes the laser light, thereby forming an electrostatic latent image on the photoreceptor 172. The developing unit 173 supplies toner (coloring material) of a predetermined color (any of C, M, Y and K) to the exposed photosensitive member 172 by means of the charged developing roller, and develops the electrostatic latent image formed on the photosensitive member 172.

The images (monochrome images) formed on the four photosensitive bodies 172 corresponding to C, M, Y and K by the toners of C, M, Y and K are sequentially superimposed on each photosensitive body 172 and transferred onto the intermediate transfer belt 174.

The intermediate transfer belt 174 (corresponding to a first rotating member) is a semiconductive endless belt suspended and rotatably supported by a plurality of rollers, such as the intermediate transfer drive roller 41, and is rotationally driven in accordance with the rotation of the rollers. The intermediate transfer belt 174 rotates with the rotation of each roller at the time of transfer of the toner image.

The intermediate transfer belt 174 is pressed against the photosensitive bodies 172 by the primary transfer roller 175. Transfer currents corresponding to the applied voltages flow through the primary transfer rollers 175. Thus, the toner images developed on the surfaces of the photosensitive bodies 172 are sequentially transferred (primary transfer) to the intermediate transfer belt 174 by the primary transfer rollers 175.

The secondary transfer roller 176 rotates while being pressed against the intermediate transfer belt 174 via the secondary transfer belt 63, and transfers (secondary transfer) the toner images of the YMCK colors formed by being transferred to the intermediate transfer belt 174 onto the paper conveyed from the paper feed unit. The residual toner of the intermediate transfer belt 174 is removed by a cleaning unit not shown.

In addition, the configuration of the periphery of the intermediate transfer belt 174 and the secondary transfer roller 176 (secondary transfer belt 63) will be described in detail later.

The fixing unit 18 includes a fixing upper member 181 and a fixing lower member 182 each including a heating unit, and performs a fixing process of fixing toner to a sheet by applying heat and pressure to the sheet to which the toner has been transferred.

The fixing lower member 182 is urged in a direction approaching the fixing upper member 181 by an unillustrated elastic member, and the fixing upper member 181 and the fixing lower member 182 are rotated in a state where the fixing lower member 182 is pressed against the fixing upper member 181, thereby constituting a fixing nip portion for nipping and conveying paper.

The fixing upper member 181 may be configured by extending and erecting a fixing belt, not shown, on the outer periphery of a roller having a heating unit.

As shown in fig. 1, the conveying unit 19 includes a plurality of paper conveying rollers that rotate while pinching the paper to convey the paper, and conveys the paper in a predetermined conveying path.

Next, the configuration of the periphery of the intermediate transfer belt 174 and the secondary transfer belt 63 will be described in detail.

Fig. 3(a) and (b) are views showing the configuration of the periphery of the intermediate transfer belt 174 and the secondary transfer belt 63 in the image forming apparatus 1.

As shown in fig. 3(a) and (b), the intermediate transfer belt 174 is stretched over the intermediate transfer driving roller 41, the intermediate transfer driven roller 42, and the like.

Further, a secondary transfer roller 176 is disposed near the intermediate transfer belt 174. A secondary transfer belt 63 (corresponding to a second rotating member) as a secondary transfer member is mounted on a secondary transfer roller 176 via a secondary transfer driving roller 61 and a secondary transfer driven roller 62. Further, the cleaning blade 64a of the secondary transfer cleaning portion 64 is brought into contact with the secondary transfer belt 63, and the surface of the secondary transfer belt 63 can be cleaned.

Further, a pressure contact/separation mechanism 65 is provided for integrally moving the secondary transfer roller 176, the secondary transfer driving roller 61, the secondary transfer driven roller 62, the secondary transfer belt 63, and the secondary transfer cleaning unit 64, so that the secondary transfer belt 63 (secondary transfer roller 176) is pressed against and separated from the intermediate transfer belt 174. The crimping/separating mechanism 65 may have a known structure, and the structure thereof is not particularly limited as the present invention.

Fig. 3(a) shows a state in which the secondary transfer belt 63 (secondary transfer roller 176) is separated from the intermediate transfer belt 174, and fig. 3(b) shows a state in which the secondary transfer belt 63 (secondary transfer roller 176) is pressed against the intermediate transfer belt 174.

Fig. 4 is a circuit block diagram related to control of the intermediate transfer belt 174 and the secondary transfer belt 63 in the image forming apparatus 1.

The control section 10 controls the drive motors and the like that drive the intermediate transfer belt 174, the secondary transfer belt 63, and the pressure contact/separation mechanism 65.

As shown in fig. 4, the intermediate transfer drive motor 41a is connected to the control section 10 so as to be controllable, and rotationally drives the intermediate transfer drive roller 41 that rotates the intermediate transfer belt 174. The intermediate transfer drive roller 41 is connected to a drive shaft of an intermediate transfer drive motor 41a via an intermediate transfer drive transmission mechanism 41 b.

The intermediate transfer drive motor 41a is constituted by a DC brushless motor. The control unit 10 transmits a PWM (Pulse Width Modulation) signal for controlling the speed and torque of the intermediate transfer drive motor 41a to the intermediate transfer drive motor 41a as a torque command value. The intermediate transfer drive motor 41a is driven based on a torque command value sent from the control unit 10, and rotates the intermediate transfer drive roller 41 by the driving.

A rotation sensor, not shown, is mounted on the intermediate transfer drive motor 41 a. The rotation sensor detects the rotation speed (rotation speed per unit time, i.e., rotation speed) of the intermediate transfer drive motor 41a, and feeds back the detection result to the control section 10 as speed information of the intermediate transfer belt 174. In addition, a known rotation sensor such as a hall element may be used as the rotation sensor, and the present invention is not limited to a specific rotation sensor.

The secondary transfer drive motor 61a is connected to the control section 10 so as to be controllable, and rotationally drives the secondary transfer drive roller 61 that rotates the secondary transfer belt 63. The secondary transfer driving roller 61 is connected to a driving shaft of a secondary transfer driving motor 61a via a secondary transfer drive transmission mechanism 61 b.

The secondary transfer drive motor 61a is constituted by a DC brushless motor. The control unit 10 transmits a PWM signal for controlling the speed and torque of the secondary transfer drive motor 61a to the secondary transfer drive motor 61a as a torque command value. The secondary transfer drive motor 61a is driven based on a torque command value sent from the control unit 10, and rotates the secondary transfer drive roller 61 by this driving, thereby rotating the secondary transfer belt 63.

A rotation sensor, not shown, is attached to the secondary transfer drive motor 61 a. The rotation sensor detects the rotation speed (rotation speed per unit time, i.e., rotation speed) of the secondary transfer drive motor 61a, and feeds back the detection result to the control section 10 as speed information of the secondary transfer belt 63. In addition, a known rotation sensor such as a hall element may be used as the rotation sensor, and the present invention is not limited to a specific rotation sensor.

Further, the press-contact/separation motor 65a can be controllably connected to the control section 10. The pressure/separation mechanism 65 is connected to a drive shaft of a pressure/separation motor 65a via a pressure/separation transmission mechanism 65 b. The secondary transfer belt 63 is moved to be pressed against and separated from the intermediate transfer belt 174 by a pressing/separating motor 65a, a pressing/separating transfer mechanism 65b, and a pressing/separating mechanism 65.

A position sensor that detects the position of the secondary transfer roller 176 and the like is mounted on the pressure/separation mechanism 65. The position sensor detects the position of the secondary transfer roller 176 and the like, and sends the detection result as pressure contact/separation information to the control section 10.

The control unit 10 transmits an operation command value for controlling the pressure contact/separation operation by the pressure contact/separation mechanism 65 to the pressure contact/separation motor 65 a.

Next, the control operation of the intermediate transfer belt 174 and the secondary transfer belt 63 by the control unit 10 will be described.

The control unit 10 rotates the intermediate transfer belt 174 at a constant speed (target speed) in accordance with the image forming operation of the image forming apparatus 1. For speed control of the intermediate transfer belt 174, a torque command value including a PWM signal is sent to the intermediate transfer drive motor 41a to obtain a target speed, and the intermediate transfer drive roller 41 is rotated at a constant speed. Information on the PWM signal for obtaining the target speed is stored in the storage unit 11 in advance, and the control unit 10 reads the information from the storage unit 11 to generate the PWM signal.

The rotation speed of the intermediate transfer drive motor 41a is detected by a rotation sensor, not shown, and the detection result is fed back to the control section 10 as speed information of the intermediate transfer belt 174. The control unit 10 determines whether or not the fed-back speed information falls within a set range, and if the speed information falls within the set range, the torque command value is kept unchanged. If the torque command value is lower than the set range, a PWM signal corresponding to the increased torque command value is generated to drive and control the intermediate transfer drive motor 41a, and if the torque command value is higher than the set range, a PWM signal corresponding to the decreased torque command value is generated to drive and control the intermediate transfer drive motor 41a so that the speed of the motor 41a becomes a speed within the set range. Thereby, constant speed control is performed so that the intermediate transfer belt 174 rotates at a constant speed.

On the other hand, different rotation controls are performed between the case where the secondary transfer belt 63 is pressed against the intermediate transfer belt 174 and the case where the secondary transfer belt is separated from the intermediate transfer belt.

When detecting that the secondary transfer belt 63 is separated from the intermediate transfer belt 174, the control unit 1 rotates the secondary transfer belt 63 at a constant speed (target speed). That is, a torque command value including a PWM signal is sent to the secondary transfer drive motor 61a to obtain a target speed, and the secondary transfer drive roller 61 is rotated at a constant speed. Information on the PWM signal for obtaining the target speed is stored in advance in the storage unit 11, and the control unit 10 reads the information from the storage unit 11 to generate the PWM signal.

Whether or not the secondary transfer belt 63 is in the separated or pressed state with respect to the intermediate transfer belt 174 can be determined based on the detection result of a position sensor that detects the position of the secondary transfer belt 63, a secondary transfer roller 176 that moves together with the secondary transfer belt 63 in association with the pressing/separating operation, or other members.

The rotation of the secondary transfer drive motor 61a is detected by a rotation sensor, not shown, and the detection result is fed back to the control section 10 as speed information of the secondary transfer belt 63. The control unit 10 determines whether the fed-back speed information falls within a preset speed range, and if the fed-back speed information falls within the preset speed range, the torque command value is kept unchanged. If the torque command value is lower than the set range, a PWM signal corresponding to the increased torque command value is generated to drive and control the secondary transfer drive motor 61a, and if the torque command value is higher than the set range, a PWM signal corresponding to the decreased torque command value is generated to drive and control the secondary transfer drive motor 61a so that the speed of the motor 61a becomes a speed within the set range. Thereby, constant speed control is performed so that the secondary transfer belt 63 rotates at a constant speed.

When the constant speed control is performed on the secondary transfer belt 63, the drive torque of the secondary transfer drive motor 61a is detected as the constant speed drive torque. In order to perform detection of the driving torque in the secondary transfer drive motor 61a, a torque detector may be connected to the secondary transfer drive motor 61a and the measurement result of the torque detector may be used. As the torque detector, there is also a torque detector which interposes a torque detector between the secondary transfer drive motor 61a and the secondary transfer drive roller 61 and detects a drive torque based on a torsion amount or the like thereof. In the device using the PWM signal as described above, the control unit 10 can analyze the PWM signal itself that is the torque command value at the time of the constant speed control to detect the torque. In the detection of the constant-speed drive torque, it is desirable to use a value with a small fluctuation deviation, for example, an average value of torque values detected within a predetermined time. Further, if the detection time of the drive torque at the constant speed falls within the detectable time, it can be set arbitrarily, and it is not necessary to detect the drive torque over the entire detectable time.

The above description has been made on the drive control in the state where the secondary transfer belt 63 is separated from the intermediate transfer belt 174, and the following description is made on the drive control in the state where the secondary transfer belt 63 is in pressure contact with the intermediate transfer belt 174.

In a state where the secondary transfer belt 63 is in pressure contact with the intermediate transfer belt 174, the control section 10 performs constant torque control so that the drive torque of the secondary transfer drive motor 61a becomes constant, based on the constant speed drive torque of the secondary transfer drive motor 61a detected at the time of constant speed control of the secondary transfer belt 63. That is, in the constant torque control, the control unit 10 generates a PWM signal corresponding to the constant-speed drive torque based on the relationship between the PWM signal and the torque command value, and drives the secondary transfer drive motor 61 a. In the constant torque control, even when paper is fed to the contact portion between the secondary transfer belt 63 and the intermediate transfer belt 174, the secondary transfer drive motor 61a is controlled to have a constant torque, and therefore, image formation can be performed satisfactorily without applying torque fluctuation to the intermediate transfer belt 174 side.

Next, a control procedure of the intermediate transfer belt 174 and the secondary transfer belt 63 by the control section 10 will be described based on the flowchart of fig. 5.

First, in a state where the secondary transfer belt 63 is separated from the intermediate transfer belt 174, the control section 10 performs constant speed control of the intermediate transfer drive motor 41a and the secondary transfer drive motor 61a based on feedback so that the intermediate transfer belt 174 and the secondary transfer belt 63 are at a constant speed, as described above (step S1).

The control unit 10 rotates the intermediate transfer drive motor 41a based on the information on the PWM signal corresponding to the target speed of the intermediate transfer belt 174 (set) stored in the storage unit 11. Further, the secondary transfer drive motor 61a is rotated based on information on the PWM signal corresponding to the target speed of the secondary transfer belt 63 (set) stored in the storage section 11.

While the constant speed control is being performed on the secondary transfer drive motor 61a, the control unit 10 detects the drive torque of the secondary transfer drive motor 61a based on the PWM signal. An average torque value of the detected drive torques is calculated as a constant-speed drive torque. The determination of the constant-speed drive torque may be determined by other appropriate methods such as an intermediate value, and the present invention is not limited to a specific method.

Next, the control section 10 starts the pressure contact/separation motor 65a for pressure contacting the secondary transfer belt 63 to the intermediate transfer belt 174 (step S2).

When the pressure contact is completed (YES in step S3), the control section 10 continues the constant-speed control of the intermediate transfer drive motor 41a, and performs the constant-torque control of the secondary transfer drive motor 61a based on the detected constant-speed-time drive torque (step S4).

Further, although not shown, when separating the secondary transfer belt 63 from the intermediate transfer belt 174, the control section 10 switches the secondary transfer drive motor 61a from the constant torque control to the constant speed control based on the constant speed described above.

The switching from the separation to the pressure bonding may be performed, for example, in association with the start of image formation. The switching from pressure contact to separation may be performed in association with the completion of the job and the reserved job. Therefore, the detection of the constant-speed drive torque of the secondary transfer drive motor 61a and the constant-torque control of the secondary transfer drive motor 61a in accordance with the constant-speed drive torque can be performed, for example, each time from the end to the start of a series of operations, and the rotation control can be performed at an appropriate torque value while adjusting the torque value in the constant-torque control. For example, even when the load torque of the secondary transfer drive motor 61a fluctuates due to wear of the cleaning blade 64a of the secondary transfer cleaning section 64 or the like, torque adjustment according to the fluctuation can be performed.

In the above description, although the detection of the constant-speed drive torque and the constant-torque control of the secondary transfer drive motor 61a according to the constant-speed drive torque have been described as the completion and the start of the series of operations, the secondary transfer belt 63 may be temporarily separated from the intermediate transfer belt 174 during the operation or the like, and after the constant-speed control of the secondary transfer drive motor 61a that drives the secondary transfer belt 63 and the detection of the constant-speed drive torque are performed, the secondary transfer belt 63 may be brought into pressure contact with the intermediate transfer belt 174 again, and the constant-torque control of the secondary transfer drive motor 61a may be performed using the corrected torque, since the risk of variation in the load torque is considered when the duration of the series of operations is long (for example, ten hours or more). This enables the secondary transfer belt 63 to be appropriately controlled in accordance with the variation in the load torque even when the work is continuously performed.

Here, for example, the intermediate transfer driving roller 41 and the secondary transfer driving roller 61 shown in fig. 3(a) have an outer shape tolerance. When the outer shape of the intermediate transfer drive roller 41 is increased by 0.1% when the rotation speed (rotation speed) of the intermediate transfer drive motor 41a as the drive source of the intermediate transfer drive roller 41 is made constant, the surface speed of the intermediate transfer belt 174 is increased by 0.1%. Similarly, when the outer shape of the secondary transfer driving roller 61 is increased by 0.1% while the rotation speed of the secondary transfer driving motor 61a as the driving source of the secondary transfer driving roller 61 is constant, the surface speed of the secondary transfer belt 63 is increased by 0.1%. The shape tolerance of the roller occurs as a deviation, and therefore occurs at the time of part replacement or due to machine variation.

On the other hand, as shown in fig. 3(b), when the intermediate transfer belt 174 and the secondary transfer belt 63 are pressed against each other, the pressure contact must be performed in a state where the surface speed difference between the intermediate transfer belt 174 and the secondary transfer belt 63 is as small as possible. However, as described above, if there is a difference in surface speed between the intermediate transfer belt 174 and the secondary transfer belt 63 due to the outer shape tolerance, a difference occurs in the driving force of the intermediate transfer belt 174 and the driving force of the secondary transfer belt 63, and when an image is transferred to a sheet, a transfer deviation occurs, resulting in deterioration of the process quality.

Therefore, in the present embodiment, for example, at the time of shipment from the factory or at the time of component replacement (replacement of components such as the intermediate transfer drive roller 41, the secondary transfer drive roller 61, the intermediate transfer belt 174, the secondary transfer belt 63, and the secondary transfer roller 176, which affect the surface speed of the intermediate transfer belt 174 and the secondary transfer belt 63), the control section 10 executes the target speed setting process a shown in fig. 6, and sets the driving speed of the secondary transfer belt 63 at which the surface speed of the secondary transfer belt 63 coincides with the surface speed of the intermediate transfer belt 174 as the target speed of the secondary transfer belt 63.

In the target speed setting process a, first, the control section 10 drives the secondary transfer drive motor 61a at the target speed 1 (corresponding to the first speed) at which the surface speed of the secondary transfer belt 63 is slower than the surface speed of the intermediate transfer belt 174 in a state where the secondary transfer belt 63 is separated from the intermediate transfer belt 174, and performs constant speed control (step S11).

Next, the control section 10 acquires, as the speed information of the secondary transfer belt 63 at the time of separation, the rotational speed of the secondary transfer drive motor 61a (for example, the average value of the rotational speeds per unit time detected in the constant speed control process, which is referred to as speed 1) during the constant speed control of the secondary transfer drive motor 61a in the separated state. Further, the constant-speed-time drive torque of the secondary transfer drive motor 61a during the constant-speed control of the secondary transfer drive motor 61a is acquired (step S12).

Next, the control section 10 causes the secondary transfer belt 63 to press-contact the intermediate transfer belt 174 by the press-contact/separation mechanism 65 (step S13), performs constant torque control on the secondary transfer drive motor 61a based on the constant speed drive torque acquired in step S12 (step S14), and acquires the rotational speed of the secondary transfer drive motor 61a during the constant torque control (for example, the average value of the rotational speeds per unit time detected in the constant torque control process, which is set to speed 2.) as the speed information of the secondary transfer belt 63 at the time of press-contact (step S15).

Fig. 7(a) is a graph showing the temporal change in the rotation speed of the secondary transfer drive motor 61a in steps S11 through S15. Since the target speed 1 in the constant speed control is a speed at which the surface speed of the secondary transfer belt 63 is slower than the surface speed of the intermediate transfer belt 174, when the secondary transfer belt 63 is pressed against the intermediate transfer belt 174, the surface speed of the secondary transfer belt 63 increases with the surface speed of the intermediate transfer belt 174, and the rotation speed of the secondary transfer drive motor 61a increases. That is, the rotation speed of the secondary transfer drive motor 61a increases.

Next, the control section 10 separates the secondary transfer belt 63 from the intermediate transfer belt 174 by the pressure contact/separation mechanism 65 (step S16), and drives the secondary transfer drive motor 61a at the target speed 2 (corresponding to the first speed) at which the surface speed of the secondary transfer belt 63 is faster than the surface speed of the intermediate transfer belt 174, thereby performing constant speed control (step S17).

The control section 10 acquires, as the speed information of the secondary transfer belt 63 at the time of separation, the rotational speed of the secondary transfer drive motor 61a (for example, the average value of the rotational speeds per unit time detected during the constant speed control, which is set to 3.) during the constant speed control of the secondary transfer drive motor 61a in the separated state. Further, the constant-speed-time drive torque of the secondary transfer drive motor 61a during the period in which the constant-speed control is performed on the secondary transfer drive motor 61a is acquired (step S18).

Next, the control section 10 causes the secondary transfer belt 63 to press-contact the intermediate transfer belt 174 by the press-contact/separation mechanism 65 (step S19), performs constant torque control on the secondary transfer drive motor 61a based on the constant speed drive torque acquired in step S18 (step S20), and acquires the rotation speed of the secondary transfer drive motor 61a during the constant torque control (for example, the average value of the rotation speeds per unit time detected in the constant torque control process, which is set as the speed 4.) (step S21).

Fig. 7(b) is a graph showing the temporal change in the rotation speed of the secondary transfer drive motor 61a in steps S17 through S21. Since the target speed 2 in the constant speed control is a speed at which the surface speed of the secondary transfer belt 63 is faster than the surface speed of the intermediate transfer belt 174, when the secondary transfer belt 63 is pressed against the intermediate transfer belt 174, the surface speed of the secondary transfer belt 63 is reduced in accordance with the surface speed of the intermediate transfer belt 174, and the rotation speed of the secondary transfer drive motor 61a is reduced. That is, the rotation speed of the secondary transfer drive motor 61a decreases.

Then, the control section 10 determines the driving speed of the secondary transfer belt 63 (the rotation speed of the secondary transfer drive motor 61 a) at which the surface speed of the secondary transfer belt 63 coincides with the surface speed of the intermediate transfer belt 174 based on the acquired speeds 1 to 4, stores (sets) information on the PWM signal corresponding to the determined driving speed in the storage section 11 as setting information of the target speed at the time of constant speed control of the secondary transfer belt 63 (step S23), and ends the rotation speed setting process a.

In step S23, the control unit 10 calculates a target speed of the secondary transfer belt 63 according to the following linear interpolation equation (equation 1).

Target speed 2- | speed 2-speed 1| × (speed 2-speed 4)/((speed 4-speed 3) - (speed 2-speed 1)) … … (formula 1)

Fig. 7(c) is a view showing the graphs of fig. 7(a) and 7(b) superimposed on each other. For example, when (speed 2-speed 1) in (equation 1) is a, (speed 3-speed 4) is B, and (speed 4-speed 2) is C, a value obtained by adding D to C × a/(a + B) is calculated as the target speed.

Thus, according to the target speed setting process a, the surface speed difference between the intermediate transfer belt 174 and the secondary transfer belt 63 which are brought into pressure contact with each other can be suppressed, and therefore, deterioration of the processing quality in the image forming apparatus, such as transfer deviation, can be suppressed.

In the above-described target speed setting process a, since only the speed change of the secondary transfer belt 63 at the time of separation and at the time of pressure contact needs to be acquired, it is possible to calculate the target speed with high accuracy with a small number of measurements of the speed information of the secondary transfer belt 63. Further, by calculating the target speed using both the speed at which the secondary transfer belt 63 is faster and the speed at which the intermediate transfer belt 174 is slower, it is possible to calculate the target speed in consideration of the amount of slip between the intermediate transfer belt 174 and the secondary transfer belt 63 occurring at the time of pressure contact.

< second embodiment >

Next, a second embodiment of the present invention will be explained.

The configuration of the image forming apparatus 1 in the second embodiment, and the control procedures of the intermediate transfer belt 174 and the secondary transfer roller 176 are the same as those described in the first embodiment, and therefore the description is cited. In the second embodiment, the process for setting the target speed of the secondary transfer belt 63 is different from that of the first embodiment. In the second embodiment, the control unit 10 executes the target speed processing B shown in fig. 8 at the time of shipment or component replacement. Next, the target speed processing B will be described with reference to fig. 8.

In the target speed setting process B, first, the control section 10 sets the first speed (the number of rotations per unit time of the secondary transfer drive motor 61 a) n (n) as the drive speed of the secondary transfer belt 63 (step S31). N (n) may be set to an arbitrary speed.

Next, in a state where the secondary transfer belt 63 is separated from the intermediate transfer belt 174, the control unit 10 performs constant speed control of the secondary transfer drive motor 61a with n (n) as a target value (step S32).

Next, the control section 10 acquires the constant-speed drive torque of the secondary transfer drive motor 61a during the constant-speed control of the secondary transfer drive motor 61a (step S33).

Next, the control section 10 presses the secondary transfer belt 63 against the intermediate transfer belt 174 by the press-contact/separation mechanism 65 (step S34), performs constant torque control on the secondary transfer drive motor 61a based on the constant speed drive torque acquired in step S33 (step S35), acquires the rotational speed of the secondary transfer drive motor 61a during the constant torque control (for example, the average value of the rotational speeds per unit time detected in the constant torque control process) as the speed information of the secondary transfer belt 63 at the time of press-contact, and sets the rotational speed as N (N +1) (step S36).

Next, the control unit 10 determines whether or not the velocity difference (|1-N (N) |) between N (N) and N (N +1) is less than a predetermined threshold value (here, 0.1) (step S37).

If it is determined that the speed difference between N (N) and N (N +1) is not less than the predetermined threshold value (NO in step S37), controller 10 sets N (N +1) to N (N) (step S38), returns to step S32, and repeatedly executes steps S32 to S37.

By repeatedly executing steps S32 to S37, the surface speed of the secondary transfer belt 63 can be made substantially equal to the surface speed of the intermediate transfer belt 174.

When determining that the speed difference between N (N) and N (N +1) is smaller than the predetermined threshold value (YES in step S37), the control unit 10 stores (sets) information on the PWM signal corresponding to N (N +1) in the storage unit 11 as setting information of the target speed in the constant speed control of the secondary transfer belt 63 (step S39), and ends the target speed setting process B.

Thus, according to the target speed setting process B, the surface speed difference between the intermediate transfer belt 174 and the secondary transfer belt 63 which are brought into pressure contact with each other can be suppressed, and therefore, deterioration of the processing quality in the image forming apparatus, such as transfer deviation, can be suppressed.

According to the target speed setting process B, there is an advantage that the calculation accuracy of the target speed is not deteriorated even if the speed is varied during the process.

In addition, a speed variation due to a load variation or noise may occur during the processing, and reliability of the detection speed may be lowered. In the first embodiment, when the speed variation occurs, a large error occurs when calculation is performed based on linear interpolation, but a large error is not easily generated in the present embodiment.

The present invention has been described above based on the above embodiments, but the description of the above embodiments is a preferable example of the image forming apparatus of the present invention, and is not limited thereto.

For example, in the first and second embodiments, the description has been given by taking an example in which the first rotating member of the present invention is the intermediate transfer belt 174 and the second rotating member is the secondary transfer belt 63, but the present invention can be applied to setting of a target speed of the second rotating member in a case where the surface speed of the second rotating member is made to coincide with the surface speed of the first rotating member, among other first and second rotating members that are rotated in pressure contact in the image forming apparatus. For example, the present invention can be applied to a case where the first rotating member is the photosensitive member 172 and the second rotating member is the intermediate transfer belt 174, and the surface speed of the intermediate transfer belt 174 is made to coincide with the surface speed of the photosensitive member 172. The present invention can also be applied to a case where the first rotating member is the fixing upper member 181 and the fixing lower member 182, and the surface speed of the fixing lower member 182 is made to coincide with the surface speed of the fixing upper member 181. Further, the present invention can be applied to a case where a photoreceptor in an image forming apparatus that does not perform intermediate transfer is a first rotating member, and a transfer body (transfer roller or the like) pressed against the photoreceptor is a second rotating member, and the surface speed of the transfer body and the surface speed of the photoreceptor are made to coincide with each other. Further, the present invention can be applied to a case where the intermediate transfer belt in an image forming apparatus in which the secondary transfer roller is directly pressed against the intermediate transfer belt without passing through the secondary transfer belt is a first rotating member and the secondary transfer roller is a second rotating member, and the surface speed of the secondary transfer roller is made to coincide with the surface speed of the intermediate transfer belt.

Further, the specific details such as the structure, control content, and order shown in the above embodiments can be appropriately changed without departing from the scope of the present invention.