阅读说明：本技术 电子照相带和电子照相图像形成设备
(Electrophotographic belt and electrophotographic image forming apparatus
) 是由 松尾康弘
内田光一
丰则祐嗣 于 2020-04-24 设计创作，主要内容包括：电子照相带和电子照相图像形成设备。提供一种即使长期使用也不容易发生由清洁刮板引起的宽度方向上的清洁不均匀的电子照相带。所述电子照相带具有环形形状并且在外周面上具有槽,所述槽均在所述电子照相带的周向上延伸,其中,当沿与所述电子照相带的周向正交的方向将所述外周面的形成有所述槽的区域等分为三个区域时,并且分别计算三个区域中包含的所述槽的深度的平均值以获得Dm、De1和De2时,其中Dm是中央区域中的所述槽的深度的平均值,De1和De2分别是两端区域中包含的所述槽的深度的平均值,Dm、De1和De2满足表达式1)和表达式2)：Dm<De1 表达式1);Dm<De2 表达式2)。(An electrophotographic belt and an electrophotographic image forming apparatus. Provided is an electrophotographic belt which is less likely to cause uneven cleaning in the width direction by a cleaning blade even when used for a long period of time. The electrophotographic belt has an annular shape and has grooves on an outer circumferential surface, the grooves each extending in a circumferential direction of the electrophotographic belt, wherein, when a region of the outer circumferential surface where the grooves are formed is equally divided into three regions in a direction orthogonal to the circumferential direction of the electrophotographic belt, and an average value of depths of the grooves contained in the three regions is calculated to obtain Dm, De1, and De2, respectively, where Dm is an average value of depths of the grooves in a central region, De1, and De2 are average values of depths of the grooves contained in two end regions, respectively, Dm, De1, and De2 satisfy expression 1) and expression 2): dm < De1 expression 1); Dm < De2 expression 2).)
1. An electrophotographic belt having an annular shape, the electrophotographic belt having a groove on an outer peripheral surface,
the grooves each extend in the circumferential direction of the electrophotographic belt,
wherein the region of the outer peripheral surface where the grooves are formed is equally divided into three regions in a width direction which is a direction orthogonal to a circumferential direction of the electrophotographic belt, and
calculating the average of the depths of the grooves contained in the three regions to obtain Dm, De1, and De2, respectively, where Dm is the average of the depths of the grooves in the central region, De1, and De2 are the average of the depths of the grooves contained in the two end regions, respectively,
Dm, De1, and De2 satisfy expression 1) and expression 2):
dm < De1 expression 1)
Dm < De2 expression 2).
2. The electrophotographic belt according to claim 1, wherein the depth of the groove becomes deeper as it is closer to an end of the electrophotographic belt in a direction orthogonal to a circumferential direction.
3. The electrophotographic belt according to claim 1 or 2, wherein a pitch of the grooves in a width direction of the electrophotographic belt is in a range of 1 μm or more and 50 μm or less.
4. The electrophotographic belt according to claim 1 or 2, wherein a pitch of the grooves in a width direction of the electrophotographic belt is constant.
5. The electrophotographic belt according to claim 1 or 2, wherein a shape of the groove in a cross section in a width direction of the electrophotographic belt is a V-shape.
6. The electrophotographic belt according to claim 1 or 2, wherein the depth of the groove is in a range of 0.2 μm or more and 3.0 μm or less.
7. The electrophotographic belt according to claim 1 or 2, wherein when an average value of widths of the grooves in the both end regions is defined as We1 and We2, respectively, and an average value of widths of the grooves in the central region is defined as Wm,
Wm, We1, and We2 satisfy expression 3) and expression 4):
wm < We1 expression 3)
Wm < We2 expression 4).
8. The electrophotographic belt according to claim 1 or 2, wherein the electrophotographic belt is an intermediate transfer belt.
9. An electrophotographic image forming apparatus comprising the electrophotographic belt according to any one of claims 1 to 8 and a cleaning member arranged to contact an outer peripheral surface of the electrophotographic belt.
Technical Field
The present disclosure relates to an electrophotographic belt such as a conveying transfer belt or an intermediate transfer belt used in an electrophotographic image forming apparatus such as a copying machine or a printer, and relates to an electrophotographic image forming apparatus.
Background
In an electrophotographic image forming apparatus, an electrophotographic belt having an endless shape is used as a conveying transfer belt that conveys a transfer material or as an intermediate transfer belt that temporarily transfers and holds a toner image.
The toner remaining on the outer surface of the electrophotographic belt even after the secondary transfer is generally cleaned using a cleaning member such as a cleaning blade.
As an intermediate transfer body for an image forming apparatus capable of improving efficiency of transferring toner from the intermediate transfer body to a transfer material while suppressing abrasion of a cleaning member, japanese patent laid-open No. 2015-125187 discloses an intermediate transfer body whose surface is formed with grooves along a moving direction of the intermediate transfer belt.
Disclosure of Invention
An embodiment of the present disclosure is directed to providing an electrophotographic belt in which cleaning unevenness in a width direction due to a cleaning blade is not likely to occur even if the electrophotographic belt is used for a long period of time.
Further, another embodiment of the present disclosure is directed to providing an electrophotographic image forming apparatus capable of stably forming high-quality electrophotographic images for a long period of time.
An embodiment of the present disclosure provides an electrophotographic belt having an annular shape, the electrophotographic belt having a groove on an outer circumferential surface,
The grooves each extend in the circumferential direction of the electrophotographic belt,
wherein when a region of the outer peripheral surface where the grooves are formed is equally divided into three regions in a width direction, which is a direction orthogonal to a circumferential direction of the electrophotographic belt, and
calculating the average of the depths of the grooves contained in the three regions to obtain Dm, De1, and De2, respectively, where Dm is the average of the depths of the grooves in the central region, De1, and De2 are the average of the depths of the grooves contained in the two end regions, respectively,
dm, De1, and De2 satisfy expression 1) and expression 2):
dm < De1 expression 1)
Dm < De2 expression 2).
Another embodiment of the present disclosure provides an electrophotographic image forming apparatus having the above-described electrophotographic belt and a cleaning member arranged to contact an outer peripheral surface of the electrophotographic belt.
Other features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Drawings
Fig. 1 is a schematic sectional view illustrating an example of an electrophotographic image forming apparatus according to another embodiment of the present disclosure.
Fig. 2 is a schematic sectional view showing the vicinity of the belt cleaning device.
Fig. 3 is a schematic cross-sectional view illustrating an example of an electrophotographic belt having an annular shape according to an embodiment of the present disclosure.
Fig. 4 is a schematic cross-sectional view illustrating an example of an electrophotographic belt having an annular shape according to an embodiment of the present disclosure.
Fig. 5 is a schematic cross-sectional view illustrating an example of an electrophotographic belt having an annular shape according to an embodiment of the present disclosure.
Fig. 6A is a schematic view showing an example of a method of manufacturing an intermediate transfer belt base layer using a stretch blow molding machine, and is a view showing a preform heating process.
Fig. 6B is a schematic view showing an example of a method of manufacturing the intermediate transfer belt base layer using a stretch blow molding machine, and is a diagram showing a preform stretching process.
Fig. 7 is a schematic diagram showing the configuration of an imprint processing apparatus that forms a groove on the surface of an intermediate transfer belt.
Fig. 8 is a schematic cross-sectional view of an intermediate transfer belt according to a comparative example.
Fig. 9 is an explanatory view showing a state where the cleaning blade is in contact with the surface of the conventional intermediate transfer belt.
Detailed Description
The inventors studied the cleaning performance of the outer surface of the intermediate transfer belt according to japanese patent laid-open publication No. 2015-125187 using a cleaning blade. As a result of the study, cleaning unevenness at the middle portion and both ends in the direction orthogonal to the circumferential direction of the intermediate transfer belt (hereinafter sometimes referred to as "width direction") is observed due to long-term use.
Therefore, the inventors studied the cause of unevenness in cleaning at the middle portion and both ends in the width direction of the intermediate transfer belt according to japanese patent laid-open No. 2015-125187 due to long-term use.
As a result, it was found that the surface grooves became shallow due to abrasion of the surfaces at both ends in the width direction of the intermediate transfer belt with long-term use, so that the frictional force between the surface of the intermediate transfer belt and the cleaning blade was increased. That is, as shown in fig. 9, in the electrophotographic image forming apparatus, the cleaning blade 21 is pressed against the surface of the intermediate transfer belt 8 by two springs 18 arranged at both ends in the width direction thereof. Therefore, the pressing force of the cleaning blade on the surface of the intermediate transfer belt 8 is higher at both ends than at the middle portion in the width direction. Therefore, with long-term use, the surfaces at both ends of the intermediate transfer belt wear relatively faster than the surfaces of the intermediate portion. Therefore, the depth of the grooves at both ends becomes shallower than the depth of the grooves at the middle portion, and therefore, the frictional force at both ends is higher, and it can be considered as a cause of a difference in cleaning performance between both ends and the middle portion in the width direction.
Therefore, in the electrophotographic belt according to an embodiment of the present disclosure, the groove forming region of the outer circumferential surface is equally divided into three regions such that each region has an equal width in a direction orthogonal to the circumferential direction of the electrophotographic belt. Hereinafter, a direction orthogonal to the circumferential direction of the electrophotographic belt may be referred to as a "width direction". In addition, when the average value of the depths of the grooves contained in the central area of the three areas is defined as Dm and the average values of the depths of the grooves contained in the both end areas of the three areas are defined as De1 and De2, respectively, Dm, De1, and De2 satisfy expressions (1) and (2):
Dm<De1 (1)
Dm<De2 (2)。
by adopting such a configuration, even if used for a long period of time, the grooves at both ends can be prevented from being worn out earlier than the grooves in the middle portion, and the generation of cleaning unevenness can be suppressed.
An example of an intermediate transfer belt constituting an embodiment of an electrophotographic belt according to the present disclosure, a method of manufacturing the intermediate transfer belt, and an electrophotographic image forming apparatus according to another embodiment of the present disclosure will be described in further detail below with reference to the drawings. However, the present disclosure is not limited to one example explained below.
1. Intermediate transfer belt
The configuration and manufacturing method of the intermediate transfer belt 8 constituting an example of an electrophotographic belt having an endless shape according to an embodiment of the present disclosure will be explained. Fig. 3 is a partially enlarged view of a cut surface of the intermediate transfer belt 8 in a direction substantially orthogonal to the circumferential direction. The intermediate transfer belt 8 is an endless belt member including two layers (i.e., a base layer 81 and a surface layer 82). The thickness of the base layer 81 is preferably 10 μm or more and 500 μm or less, and particularly preferably 30 μm or more and 150 μm or less. The thickness of the surface layer 82 is preferably 0.5 μm or more and 5 μm or less, and particularly preferably 1 μm or more and 3 μm or less.
Materials that can be used for the base layer 81 include, for example, thermoplastic resins such as polycarbonate, polyvinylidene fluoride (PVDF), polyethylene, polypropylene, polymethylpentene-1, polystyrene, polyamide, polysulfone, polyarylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyphenylene sulfide, polyether sulfone, polyether nitrile, thermoplastic polyimide, polyether ether ketone, thermotropic liquid crystal polymer, and polyamic acid. Mixtures of two or more of the foregoing resin types may also be used.
As a manufacturing method of the base layer 81, a conductive material or the like can be melted and kneaded into these thermoplastic resins, and then a molding method such as inflation molding, cylinder extrusion molding, blow molding, or the like can be appropriately selected to obtain the base layer 81.
As the material of the surface layer 82, a curable material that is cured by heat or irradiation of an energy beam such as an electron beam or light (ultraviolet rays or the like) may be suitably used from the viewpoint of increasing the surface hardness of the intermediate transfer belt 8 to improve durability (abrasion resistance). In particular, a curable material which is highly curable and is cured by irradiation with ultraviolet rays or electron beams or the like is preferable. Among the curable materials, usable organic materials include curable resins such as melamine resins, urethane resins, alkyd resins, acrylic resins, and fluorine-based curable resins (fluorinated curable resins).
Methods that may be used to form the surface layer 82 atop the base layer 81 include, for example, dip coating, spray coating, roll coating, spin coating, and ring coating, among others. By appropriately selecting and adopting the method from these methods, the surface layer 82 having a desired film thickness can be obtained.
The intermediate transfer belt 8 has grooves 84 on the outer circumferential surface, and the grooves 84 each extend in the circumferential direction of the intermediate transfer belt. That is, the groove 84 extending in the circumferential direction of the intermediate transfer belt is constituted by the outer surface of the surface layer 82. For example, the pitch of the grooves 84 extending in the circumferential direction of the intermediate transfer belt and in the outer surface of the intermediate transfer belt 8 (hereinafter also referred to as "groove pitch") is preferably constant in the width direction.
Further, the shape of the groove 84 is appropriately set for the combination of the cleaning blade 21 and the toner, but when the groove pitch is the pitch I, the pitch I is preferably in the range of 1 μm or more and 50 μm or less.
Further, when the length of the opening of the groove 84 in the width direction of the intermediate transfer belt is a width W, the width W is preferably 0.10 μm or more and 3.0 μm or less, and the depth D is preferably 0.2 μm or more and 3.0 μm or less.
The cleaning blade 21 is in contact with the outer peripheral surface of the intermediate transfer belt 8, and the outer peripheral surface is cleaned by the cleaning blade 21. The pressing force of the cleaning blade 21 acting on the outer peripheral surface of the intermediate transfer belt 8 tends to be higher at the end portion where the pressure spring 18 is arranged than at the middle portion in the length direction (the width direction of the intermediate transfer belt 8). Therefore, according to the tendency that the pressing force is higher at the end portions, the depth of the groove constituted in the outer surface of the intermediate transfer belt 8 is preferably deeper at the end portions than at the intermediate portion in the length direction, and the wear resistance is preferably improved. Alternatively, it is also preferable to make the depth of the groove deep only at the end of the cleaning blade 21 where the pressing force is high.
Means that can be used to make the depth of the groove 84 deep at the end of the intermediate transfer belt 8 include, for example, centrifugal molding, casting, and stamping in which the shape of the mold surface is transferred by, for example, contact with a mold. Among these methods, imprinting is particularly desirable for imparting a desired shape to a mold surface or obtaining a desired shape of the groove 84 by transferring the shape using elastic deformation or thermal expansion.
The depth D of the groove 84 is preferably deeper than the groove 84 near the end portion in the direction orthogonal to the circumferential direction of the intermediate transfer belt 8. That is, the groove depth becomes deeper as it gets closer to both ends of the electrophotographic belt. The depth of the groove 84 is preferably in the range of 0.2 μm or more and 3.0 μm or less.
Further, when the average values of the widths of the grooves in the both end regions are defined as We1 and We2, respectively, and the average value of the widths of the grooves in the central region is defined as Wm, We1, and We2 preferably satisfy expressions (3) and (4):
Wm<We1(3)
Wm<We2(4)。
that is, the average value of the widths of the grooves 84 in the both end regions is preferably larger than the average value of the widths of the grooves 84 in the central region. In particular, as for the groove 84 near the end in the width direction of the intermediate transfer belt 8, the width W of the groove 84 is preferably larger.
The slot 84 is preferably formed to include an area WcIn the region W of the cleaning blade 21cAnd is in contact with the intermediate transfer belt 8.
It is desirable that the sliding characteristics of the sliding between the intermediate transfer belt 8 and the cleaning blade 21 be uniform over the entire contact width. Therefore, the cross-sectional shape of the groove 84 in the width direction of the intermediate transfer belt 8 is more preferably V-shaped. Since the groove 84 has a V-shaped cross-sectional shape in the width direction, the deeper the groove depth, the wider the groove width. That is, at the end portion of the intermediate transfer belt 8 having a deep groove depth, the contact area with the cleaning blade 21 becomes small. Therefore, the frictional force at the end portion can be reduced, so that uniform sliding characteristics can be achieved, which cancel out the pressing characteristics of the cleaning blade 21, which is particularly preferable. With respect to the cross-sectional shape of the V-shape, the groove 84 may have a width that narrows toward the bottom, and the cross-sectional shape of the groove 84 may be triangular or trapezoidal.
2. General configuration and operation of electrophotographic image forming apparatus
Fig. 1 is a schematic sectional view showing an overall configuration of an electrophotographic image forming apparatus 100 constituting an example of an electrophotographic image forming apparatus according to another embodiment of the present disclosure. The electrophotographic image forming apparatus 100 is a tandem-type (distance-type) laser beam printer that utilizes an intermediate transfer system so that a full-color image can be formed using an electrophotographic system.
The electrophotographic image forming apparatus 100 has four image forming units Y, M, C and K arranged in a line at fixed intervals. The image forming units Y, M, C and K form images in yellow (Y), magenta (M), cyan (C), and black (K), respectively. Note that in the electrophotographic image forming apparatus 100, the configurations and operations of the respective image forming units Y, M, C and K are substantially the same except that the toner colors used are different.
The image forming units Y, M, C and K have photosensitive drums 1Y, 1M, 1C, and 1K of drum-shaped (cylindrical) electrophotographic photoreceptors (photoreceptors) constituting image carriers. The photosensitive drums 1Y, 1M, 1C, and 1K are OPC photosensitive drums, and are rotationally driven in the direction of an arrow R1 in fig. 1. The following units are arranged in order in the rotational direction around the photosensitive drums 1Y, 1M, 1C, and 1K. First, charging rollers 2Y, 2M, 2C, and 2K, which are roller-shaped charging rollers constituting a charging unit (electrical charging unit), are arranged. Next, exposure devices 3Y, 3M, 3C, and 3K constituting an exposure unit are configured. Then, the developing devices 4Y, 4M, 4C, and 4K constituting the developing units are arranged. After that, primary transfer rollers 5Y, 5M, 5C, and 5K as roller-shaped primary transfer members constituting the primary transfer unit are arranged. Next, drum cleaning devices 6Y, 6M, 6C, and 6K constituting the image carrier cleaning unit are configured.
The developing devices 4Y, 4M, 4C, and 4K contain non-magnetic one-component developers as the developers, and have developing sleeves 41Y, 41M, 41C, and 41K constituting developer carriers, and developer coating blades and the like constituting developer regulating units, respectively. The photosensitive drums 1Y, 1M, 1C, and 1K, the charging rollers 2Y, 2M, 2C, and 2K, the developing devices 4Y, 4M, 4C, and 4K, and the drum cleaning devices 6Y, 6M, 6C, and 6K integrally constitute process cartridges 7Y, 7M, 7C, and 7K. The process cartridges 7Y, 7M, 7C, and 7K are detachably mounted to the apparatus main body of the electrophotographic image forming apparatus 100. Further, the exposure devices 3Y, 3M, 3C, and 3K are constituted by scanner units that scan laser beams by means of a polygon mirror, and project scanning beams modulated based on image signals onto the photosensitive drums 1Y, 1M, 1C, and 1K.
Further, the electrophotographic image forming apparatus 100 includes an intermediate transfer belt 8, and the intermediate transfer belt 8 is an example of an electrophotographic belt having an endless shape according to an embodiment of the present disclosure described previously.
The intermediate transfer belt 8 is arranged in contact with the photosensitive drums 1Y, 1M, 1C, and 1K of the respective image forming units Y, M, C and K. The intermediate transfer belt 8 is supported by three rollers (tension rollers), i.e., a drive roller 9, a tension roller 10, and a secondary transfer counter roller 11, so as to maintain a predetermined tension. Since the drive roller 9 is rotationally driven, the intermediate transfer belt 8 moves (rotates) in the direction of an arrow R2 in fig. 1 (in the belt conveying direction).
In the electrophotographic image forming apparatus 100, the intermediate transfer belt 8 is moved forward relative to the photosensitive drums 1Y, 1M, 1C, and 1K at substantially the same speed in the portion opposed to the photosensitive drums 1Y, 1M, 1C, and 1K. On the inner peripheral surface side of the intermediate transfer belt 8, the above-described primary transfer rollers 5Y, 5M, 5C, and 5K are arranged at positions opposed to the respective photosensitive drums 1Y, 1M, 1C, and 1K, respectively.
The primary transfer rollers 5Y, 5M, 5C, and 5K are urged (pressurized) against the photosensitive drums 1Y, 1M, 1C, and 1K at a predetermined pressure across the intermediate transfer belt 8. Further, the primary transfer rollers 5Y, 5M, 5C, and 5K form primary transfer sections (primary transfer nips) N1Y, N1M, N1C, and N1K in which the photosensitive drums 1Y, 1M, 1C, and 1K are in contact with the intermediate transfer belt 8, respectively, in the primary transfer sections N1Y, N1M, N1C, and N1K.
Further, on the outer peripheral surface side of the intermediate transfer belt 8, a secondary transfer roller 15 as a roller-shaped secondary transfer member constituting a secondary transfer unit is disposed at a position opposing the secondary transfer opposing roller 11. The secondary transfer roller 15 is urged (pressed) against the secondary transfer counter roller 11 with a predetermined pressure across the intermediate transfer belt 8, and a secondary transfer portion (secondary transfer nip portion) N2 is formed where the secondary transfer roller 15 contacts the intermediate transfer belt 8. Further, on the outer peripheral surface side of the intermediate transfer belt 8, a belt cleaning device 12 constituting an intermediate transfer body cleaning unit is disposed at a position opposing the secondary transfer counter roller 11. An intermediate transfer belt unit 13 detachably mounted to the apparatus main body of the electrophotographic image forming apparatus 100 is constituted by the intermediate transfer belt 8 supported by the aforementioned three rollers 9, 10, and 11 and a belt cleaning device 12.
When the image forming operation is started, the respective photosensitive drums 1Y, 1M, 1C, and 1K and the intermediate transfer belt 8 start to rotate in the directions of arrows R1 and R2 in fig. 1 at predetermined process speeds (peripheral speeds), respectively. The surfaces of the rotating photosensitive drums 1Y, 1M, 1C, and 1K are substantially uniformly charged by the charging rollers 2Y, 2M, 2C, and 2K with a predetermined polarity (negative polarity in the electrophotographic image forming apparatus 100). At this time, a predetermined charging bias is applied to the charging rollers 2Y, 2M, 2C, and 2K from a charging power supply constituting a charging bias applying unit (not shown).
Thereafter, the charged surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K are exposed by scanning light beams from the exposure devices 3Y, 3M, 3C, and 3K, respectively, in accordance with image information corresponding to the respective image forming units Y, M, C and K. Accordingly, an electrostatic image (electrostatic latent image) corresponding to the image information is formed on the surface of each of the photosensitive drums 1Y, 1M, 1C, and 1K.
Subsequently, the electrostatic images formed on the photosensitive drums 1Y, 1M, 1C, and 1K are developed as toner images by the developing devices 4Y, 4M, 4C, and 4K by means of color toners corresponding to the respective image forming units Y, M, C and K.
Here, the toners in the developing devices 4Y, 4M, 4C, and 4K are charged in the negative polarity by a developer coating blade (not shown), and are coated to the developing sleeves 41Y, 41M, 41C, and 41K. Further, a predetermined developing bias is applied to the developing sleeves 41Y, 41M, 41C, and 41K by a developing power source constituting a developing bias applying unit (not shown). Then, the electrostatic images formed on the photosensitive drums 1Y, 1M, 1C, and 1K reach portions (developing portions) opposing the photosensitive drums 1Y, 1M, 1C, and 1K and the developing sleeves 41Y, 41M, 41C, and 41K. Here, the electrostatic images on the photosensitive drums 1Y, 1M, 1C, and 1K are made visible by the negative polarity toner, and the toner images are formed on the photosensitive drums 1Y, 1M, 1C, and 1K.
Thereafter, the toner images formed on the photosensitive drums 1Y, 1M, 1C, and 1K are transferred (primary transfer) to the intermediate transfer belt 8, and the intermediate transfer belt 8 is rotationally driven by the action of the primary transfer rollers 5Y, 5M, 5C, and 5K in the primary transfer portions N1Y, N1M, N1C, and N1K, respectively. At this time, primary transfer biases are applied to the primary transfer rollers 5Y, 5M, 5C, and 5K from the respective primary transfer power sources E1Y, E1M, E1C, and E1K constituting the primary transfer bias applying unit. The primary transfer bias is a DC voltage of a polarity (positive polarity in the electrophotographic image forming apparatus 100) opposite to the polarity used for charging the toner during development. For example, when a full-color image is formed, electrostatic images are formed on the photosensitive drums 1Y, 1M, 1C, and 1K with a certain time lag according to the distances between the primary transfer portions N1Y, N1M, N1C, and N1K for the respective colors, and the electrostatic images are developed, thereby producing toner images. Further, the toner images of each color formed on the photosensitive drums 1Y, 1M, 1C, and 1K of the respective image forming units Y, M, C and K are sequentially superimposed on the intermediate transfer belt 8 in the respective primary transfer portions N1Y, N1M, N1C, and N1K. Thereby forming a plurality of toner images of four colors on the intermediate transfer belt 8.
In addition, according to the electrostatic image formed by exposure, a transfer material P such as recording paper or the like loaded in a transfer material storage cassette (not shown) is picked up by a transfer material supply roller (not shown) and conveyed to the registration roller 14 by a conveying roller (not shown). The transfer material P is conveyed by the registration roller 14 to a secondary transfer portion N2 formed by the intermediate transfer belt 8 and the secondary transfer roller 15 in synchronization with the toner image on the intermediate transfer belt 8.
Then, for example, the plurality of toner images of four colors carried on the intermediate transfer belt 8 as described above are transferred (secondary transfer) together onto the transfer material P by the action of the secondary transfer roller 15 in the secondary transfer portion N2. At this time, a secondary transfer bias, which is a DC voltage of a polarity (positive polarity in the electrophotographic image forming apparatus 100) opposite to the polarity for charging the toner during development, is applied to the secondary transfer roller 15 from the secondary transfer power source E2 constituting the secondary transfer bias applying unit.
Thereafter, the transfer material P to which the toner image has been transferred is conveyed to a fixing device 16 constituting a fixing unit. Then, the transfer material P is sandwiched between a pressure roller and a fixing roller of the fixing device 16, and is pressurized and heated during being conveyed, thereby fixing the toner image on the transfer material P. The transfer material P as an image formation product to which the toner image is fixed is discharged from the apparatus main body of the electrophotographic image forming apparatus 100.
Further, in the primary transfer portions N1Y, N1M, N1C, and N1K, the toner remaining on the photosensitive drums 1Y, 1M, 1C, and 1K is removed and recovered by the drum cleaning devices 6Y, 6M, 6C, and 6K, instead of being transferred onto the intermediate transfer belt 8 (primary transfer residual toner). Likewise, the toner remaining on the intermediate transfer belt 8 is removed and recovered from the intermediate transfer belt 8 by the belt cleaning device 12, instead of being transferred onto the transfer material P (secondary transfer residual toner) in the secondary transfer portion N2.
3. Belt cleaning device
Fig. 2 is a main sectional view showing the vicinity of the belt cleaning device 12.
The belt cleaning device 12 has a cleaning tank 17 and a cleaning action part 20 provided in the cleaning tank 17. The cleaning container 17 is constituted as a part of a frame main body (not shown) of the intermediate transfer belt unit 13. The cleaning action part 20 includes a cleaning blade 21 constituting a cleaning member and a supporting member 22 supporting the cleaning blade 21. The cleaning blade 21 is, for example, an elastic blade (rubber portion) using urethane rubber (polyurethane) as an elastic material as a material thereof. Further, the support member 22 is formed of, for example, a metal plate (metal plate portion) using a plated steel plate as a material. The cleaning blade 21 is fastened to the support member 22 to constitute the cleaning action portion 20.
The cleaning blade 21 is a plate-like member long in one direction by a predetermined thickness. The cleaning blade 21 has two substantially orthogonal sides, the lengthwise side extending in a direction substantially orthogonal to the belt conveying direction (hereinafter referred to as "thrust direction"), and one end side of the short side contacting the intermediate transfer belt 8.
The cleaning action portion 20 is configured to be pivotable. That is, the support member 22 is pivotably supported via a pivot shaft 19 fixed to the cleaning container 17. As a biasing unit provided in the cleaning container 17, the supporting member 22 is pressurized by the pressure spring 18, so that the cleaning action part 20 rotates about the pivot shaft 19, and the cleaning blade 21 is biased (pressurized) against the intermediate transfer belt 8.
Pressure springs 18 are arranged at both end portions in the longitudinal direction of the supporting member 22, and the cleaning blade 21 is pressed against the intermediate transfer belt 8. The secondary transfer opposing roller 11 is disposed opposite to the cleaning blade 21 inside the intermediate transfer belt 8. The cleaning blade 21 is in contact with the intermediate transfer belt 8 in one direction opposite to the belt conveying direction. In other words, the cleaning blade 21 is in contact with the surface of the intermediate transfer belt 8 in such a manner that the distal end of the free end side in the short side direction faces the upstream side in the belt conveying direction. Thus, a blade nip portion 23 is formed between the cleaning blade 21 and the intermediate transfer belt 8. The cleaning blade 21 collects toner remaining on the outer peripheral surface of the moving intermediate transfer belt 8 in the blade nip portion 23.
For example, the mounting position of the cleaning blade 21 is set as follows. The angle θ was set at 24 °, the penetration amount was set at 1.5mm, and the pressing force was set at 0.6N/cm. Here, the set angle θ is an angle formed between the intermediate transfer belt 8 and the cleaning blade 21.
Further, the amount of intrusion is the length in the normal direction of the overlap between the free end of the cleaning blade 21 and the intermediate transfer belt 8. For example, the thickness of the cleaning blade 21 is 2mm, the length in the thrust direction is 245mm, and the hardness of the cleaning blade 21 is 77 degrees according to JIS K6253 standard. When the thrust-direction length of the intermediate transfer belt 8 is 250mm, the cleaning blade 21 is arranged in contact with the outer peripheral surface of the intermediate transfer belt 8 over the entire width thereof. Further, the pressing force from the cleaning blade 21 in the blade nip 23 is defined by a linear load in the length direction, and is measured, for example, using a film pressure measuring system (product name: PINCH, manufactured by Nitta). By setting the mounting position of the cleaning blade 21 as described above, burrs and sliding noise of the cleaning blade 21 in a high-temperature, high-humidity environment (30 ℃/80%) can be suppressed, and good cleaning performance can be obtained. In addition, by the above arrangement, poor cleaning in a low-temperature, low-humidity environment (15 ℃/10%) can be suppressed, and good cleaning performance can be obtained.
Further, the frictional resistance due to the sliding of the urethane rubber against the synthetic resin is generally large, and the initial burr of the cleaning blade 21 is easily generated. Therefore, the tip of the free end side of the cleaning blade 21 can be coated with an initial lubricant such as graphite fluoride in advance.
According to an embodiment of the present disclosure, it is possible to obtain an electrophotographic belt that is not easily cleaned unevenly in the width direction by a cleaning blade even if used for a long period of time. Further, according to another embodiment of the present disclosure, an electrophotographic image forming apparatus capable of stably forming a high-quality electrophotographic image for a long period of time can be obtained.
