JP2005107033A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus with less color misregistration and less defects such as transfer omission and poor cleaning.
An image carrier that holds toner, and is wound and stretched around a plurality of rollers, and runs endlessly in a direction perpendicular to the width direction by rotation of the roller, and an outer peripheral surface is in contact with the image carrier. An intermediate transfer belt and one of the plurality of rollers, contacting the intermediate transfer belt from an inner peripheral surface opposite to the outer peripheral surface, and applying a voltage to transfer the toner to the intermediate transfer belt by electrostatic force A transfer roller to be moved and the axial direction of at least one of the plurality of rollers arranged close to both ends or one end of the roller, and in contact with the side surface of the intermediate transfer belt in the width direction of the intermediate transfer belt A low-volume electric efficiency of the intermediate transfer belt is 1 × 10 ⁹ [Ω · cm] or more and 1 × 10 ¹⁰ [Ω · cm] or less, and the hardness of the transfer roller is 2 It is 8 [Asuka C] or more and 70 [Asuka C] or less.
[Selection] Figure 1

Description

  The present invention relates to an image forming apparatus.

  In recent years, there have been many opportunities to handle color images even in offices, and color image forming apparatuses based on electrophotography, particularly color printers and color MFPs, have been installed in offices. At present, in some large offices, there are many places where one black and white copier is used in combination with one color printer. However, as color printers penetrate into smaller offices, they are replaced with black and white copiers. A color MFP is desired. In this case, it is desirable that the black-and-white copying performance is equivalent to that of the black-and-white copying machine and color printing is possible. Currently, the most widely used color image forming apparatus uses an intermediate transfer device, develops an image for each color on one photoconductor, sequentially transfers the image onto the intermediate transfer device, and then transfers the image onto the intermediate transfer device. In this method, the four colors are superimposed and transferred onto paper (transfer material) at once. This method is smaller in size than the method using four photoconductors. In such an apparatus, an intermediate transfer belt is often used for the intermediate transfer apparatus. The intermediate transfer belt is wound around a driving roller and a driven roller and stretched, and travels endlessly by the rotation of the driving roller.

  In general, the intermediate transfer belt of the above-described intermediate transfer device is uneven in thickness, and the lengths of both ends along the running direction are slightly different. For this reason, it is known that the intermediate transfer belt is shifted toward the width direction (the direction crossing the traveling direction), that is, one end side in the axial direction of each roller during traveling. The direction in which the intermediate transfer belt is offset (front side or rear side) varies depending on the intermediate transfer belt, and also differs depending on the direction in which the intermediate transfer belt is stretched between the rollers. In any case, when the intermediate transfer belt is shifted toward one end in the axial direction, it is one of the causes of color misregistration when the degree of deviation is large. Therefore, a regulating member is provided on the outer side in the width direction of the belt, and the side surface of the belt is slidably contacted with the regulating member (see, for example, Patent Document 1), or a protrusion (rib, bead) is provided on the back of the belt. The belt travel is stabilized by pressing against the regulating surface of the roller (see, for example, Patent Document 2).

In the above method, the side surface of the belt is in sliding contact with the regulating member, stress due to sliding contact is transmitted to a position slightly away from the side surface of the intermediate transfer belt, and a depression or undulation is generated at this position, thereby causing color misregistration. Is also known to occur. Therefore, the position of the restriction member is devised, and the restriction member is provided at a position where the side surface of the intermediate transfer belt and the restriction member are in sliding contact with the downstream side of the intermediate position along the traveling direction of the region where the intermediate transfer belt contacts the drive roller. Thus, a method for reducing depressions and undulations has been proposed (see Patent Document 1).
JP 2001-97522 A ([0047] to [0055]) Japanese Patent Laid-Open No. 11-79458 (FIG. 3)

  However, the present inventor considered that a sufficiently high-quality image could not be obtained even by the method in which the movement of the intermediate transfer belt is regulated by providing the regulating members and protrusions as described above. That is, in the above-described regulation method, the large displacement and wavy of the intermediate transfer belt are prevented, and the color misregistration is reduced. However, when the belt offset force is large, it becomes difficult to completely prevent the belt from wavy. This undulation causes problems such as transfer failure and belt cleaning failure (blade turning). Because of these problems, it was thought that a sufficiently good image was not obtained.

  The present invention is based on the recognition of such a problem, and an object thereof is to provide an image forming apparatus with less color misregistration and less defects such as transfer omission and poor cleaning.

An image forming apparatus according to an embodiment of the present invention includes an image carrier that holds toner, and is wound and stretched around a plurality of rollers, and runs endlessly in a direction perpendicular to the width direction by rotation of the rollers. An intermediate transfer belt whose surface is in contact with the image carrier and one of the plurality of rollers, the intermediate transfer belt from the inner peripheral surface opposite to the outer peripheral surface in contact with the image carrier to the intermediate transfer belt A transfer roller to which a voltage is applied and the toner is transferred to the intermediate transfer belt by electrostatic force, and is disposed close to both ends or one end side in the axial direction of at least one of the plurality of rollers, and a regulating member for regulating movement of the said width direction of the intermediate transfer belt by contacting the side surface of the intermediate transfer belt, the volume electric low efficiency of the intermediate transfer belt 1 × 10 9 ^[Ω · c ] More than ^{1 × 10 10 [Ω · cm} ] or less, and wherein the hardness of the transfer roller 28 'is Asker C] to 70 [Asker C] or less.

  An image forming apparatus according to an embodiment of the present invention includes a photoconductor region, an image carrier that holds a toner image in the photoconductor region, and a plurality of rollers wound around the roller. The outer peripheral surface and the inner peripheral surface, the inner peripheral surface is in contact with the plurality of rollers, and one or both of the side end portions of the outer peripheral surface is the photosensitive region of the image carrier. And an intermediate transfer belt whose outer peripheral surface is a surface opposite to a sag generation surface generated when the intermediate transfer belt is cut.

  The image forming apparatus according to the embodiment of the present invention includes an image carrier that holds toner and a plurality of rollers that are wound around and stretched, and the rollers rotate endlessly in a direction perpendicular to the width direction. An intermediate transfer belt in which an outer peripheral surface is in contact with the image carrier and protrusions are provided in the vicinity of both ends in the width direction of the inner peripheral surface opposite to the outer peripheral surface; and the outer peripheral surface of the intermediate transfer belt is cleaned A belt cleaner that regulates movement of the intermediate transfer belt in the width direction by contact with an inner surface of the protrusion, and the width of the belt cleaner is at one end side. The width of the protrusion is narrower than the width from the inner surface of the protrusion to the inner surface of the protrusion on the other end, and the end surface of the belt cleaner enters the inner side of the inner surface of the protrusion in the width direction. Arranged as It is characterized in that is.

  The image forming apparatus according to the embodiment of the present invention includes an image carrier that holds toner and a plurality of rollers that are wound around and stretched, and the rollers rotate endlessly in a direction perpendicular to the width direction. And an intermediate transfer belt whose outer peripheral surface is in contact with the image carrier and at least one end of the plurality of rollers in the axial direction. A contact member that restricts the movement of the intermediate transfer belt in the axial direction by contact; and the outer peripheral surface of the intermediate transfer belt is cleaned, and an end surface is located inward of the restriction surface of the restriction member in the width direction. And a belt cleaner arranged to enter.

  The image forming apparatus according to the embodiment of the present invention includes an image carrier that holds toner and a plurality of rollers that are wound around and stretched, and the rollers rotate endlessly in a direction perpendicular to the width direction. An intermediate transfer belt in which an outer peripheral surface is in contact with the image carrier, a protrusion is provided on an inner peripheral surface opposite to the outer peripheral surface, and the position of the inner surface of the protrusion is from 10 mm to 15 mm from the side surface; A restricting member that is disposed adjacent to both end sides or one end side in the axial direction of at least one of the rollers, and restricts movement of the intermediate transfer belt in the width direction by contacting a side surface of the intermediate transfer belt And.

  According to the present invention, in the image forming apparatus having the intermediate transfer belt, in addition to providing the regulating member for preventing the lateral displacement of the intermediate transfer belt, the volume electrical resistivity of the intermediate transfer belt and the hardness of the transfer roller are set to predetermined values. Therefore, color misregistration can be reduced and transfer omission can be reduced. Further, since the intermediate transfer belt is provided with protrusions (beads) for preventing lateral displacement and the width of the belt cleaner is narrowed, color misregistration can be reduced and poor cleaning can be prevented. Further, since the regulating member for preventing the lateral displacement of the intermediate transfer belt is provided and the width of the belt cleaner is narrowed, it is possible to prevent the cleaning failure. Further, since the regulating member for preventing the lateral displacement of the intermediate transfer belt is provided and the protrusion is provided at a position slightly away from the end of the intermediate transfer belt, it is possible to reduce transfer omission.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following, six embodiments will be described.

First Embodiment FIG. 1 is a diagram showing an image forming apparatus according to a first embodiment of the present invention. This image forming apparatus is a color image forming apparatus using an electrophotographic process. The image forming apparatus includes a photosensitive drum (image carrier) 1 having a photosensitive layer formed of a photosensitive member on the surface, a developing device 10, an intermediate transfer device 20, a paper feed cassette 30, and a paper path 40. And a fixing device 50. In addition, a charger 2, an exposure device 3, and a static eliminator 4 are disposed around the photosensitive drum 1.

  In the apparatus of FIG. 1, the charger 2 uniformly charges the photosensitive member on the surface of the rotating photosensitive drum 1. The exposure device 3 forms an electrostatic latent image on the surface of the photosensitive drum 1 by scanning exposure based on the image information. Here, the image information to be exposed is single-color image information obtained by decomposing a desired full-color image into color information of yellow, magenta, cyan, and black. The electrostatic latent image formed on the photosensitive drum 1 is developed with predetermined yellow, magenta, cyan, and black toners by the developing device 10, respectively. The developing device 10 is a revolver type developing device, and includes a black developing device BK (hereinafter referred to as BK developing device), a cyan developing device C (hereinafter referred to as C developing device), a magenta developing device M (hereinafter referred to as M developing device), and a yellow developing device. A developing unit Y (hereinafter referred to as Y developing unit), a developing unit holder 11 that holds these units, and a revolver rotation drive unit (not shown) that rotates the developing unit holder. The developing units BK, C, M, and Y have developing rollers (developing sleeves) that rotate while contacting the developer with the surface of the photosensitive drum 1 in order to develop the electrostatic latent image. In the standby state, the revolver developing device 10 waits in a non-contact manner at a position where development is performed by the BK developing device. When the operation is started, optical writing / latent image formation by laser light from the exposure apparatus 3 starts based on the image signal (hereinafter, an electrostatic latent image by the BK image signal is referred to as a BK latent image). In order to develop from the leading edge of the BK latent image, the developing roller starts rotating before the leading edge of the latent image reaches the developing position of the BK developing device, and the BK latent image is developed with the BK toner. After the latent image is formed, when the end portion passes the BK latent image position, the revolver developing device is driven and rotated immediately from the developing position by the BK developing device to the developing position by the next color developing device, Similarly, the next color is developed. As the intermediate transfer belt 21 rotates, the BK toner image, the C toner image, the M toner image, and the Y toner image are sequentially transferred onto the intermediate transfer belt 21, and finally, in the order of BK, C, M, and Y. A full-color toner image is formed on the intermediate transfer belt 21 in an overlapping manner.

  In the image forming apparatus of FIG. 1, as described above, images of the respective colors are formed on the photosensitive drum 1, and a toner image is formed. The toner image formed on the photosensitive drum 1 is sequentially superimposed on the intermediate transfer belt 21 of the intermediate transfer device 20 that rotates in synchronization with the photosensitive drum 1 in the order of yellow, magenta, cyan, and black. Transcribed. The toner image superimposed on the intermediate transfer belt 21 is secondarily transferred onto the transfer paper (transfer material) conveyed from the paper feed cassette 30 to the transfer portion T on the secondary transfer roller 29 in the secondary transfer region T. Is done. Thereafter, the transfer paper is conveyed to the fixing device 50 through the paper path 40, and the fixing device 50 fixes the toner to the transfer paper.

  The image forming apparatus according to the present embodiment is characterized by the structure of the intermediate transfer device 20. This will be described below.

  As can be seen from FIG. 1, the intermediate transfer device 20 secondarily transfers the toner image primarily transferred from the photosensitive drum 1 in the primary transfer region S to the transfer material in the secondary transfer region T. The intermediate transfer device 20 has an intermediate transfer belt 21. The intermediate transfer belt 21 includes a primary transfer roller (transfer roller) 22, a drive roller 23, a backup roller 24, a tension roller 25, and a driven roller 26 that are disposed substantially parallel to each other at a predetermined distance. It is wound around and stretched. Then, the drive roller 23 rotates to endlessly travel in the direction perpendicular to the width direction (the direction of the arrow in the figure). The intermediate transfer belt 21 has an outer peripheral surface (front surface) and an inner peripheral surface (back surface), the inner peripheral surface is in contact with the plurality of rollers 22 to 26, and the outer peripheral surface is a primary transfer region S. Touch drum 1. In this primary transfer region S, the primary transfer roller 22, which is one of the plurality of rollers 22 to 26, contacts the intermediate transfer belt 21 from the inner peripheral surface opposite to the outer peripheral surface that contacts the photoreceptor 1. Yes. In the primary transfer region S, a bias is applied to the primary transfer roller 22, and the toner is transferred to the intermediate transfer belt 21 by electrostatic force. The primary transfer roller 22 can be made of, for example, foamed polyurethane blended with a conductive material.

  FIG. 2 is a top view of the intermediate transfer device 20 described above. The intermediate transfer belt 21 moves from the upper side to the lower running direction in the figure. The intermediate transfer device 20 includes a front side regulating member 60F and a rear side regulating member 60R in the vicinity of both ends of the rotation shaft of the drive roller 23. The interval between the restricting members 60F and 60R is set slightly wider than the width of the intermediate transfer belt 21. Thus, by providing the regulating members 60F and 60R close to both ends of the drive roller 23, even if the intermediate transfer belt 21 starts to shift to one side in the axial direction during traveling, the inner surfaces of the regulating members 60F and 60R. And the side surfaces 21F and 21R of the intermediate transfer belt 21 come into contact with each other, and the travel position in the width direction (axial direction) of the intermediate transfer belt 21 is regulated.

  Further, the restricting surfaces 62F and 62R of the restricting members 60F and 60R are located on the downstream side of the intermediate position along the traveling direction of the region where the intermediate transfer belt 21 contacts the outer peripheral surface of the drive roller 23. It is provided at a position in sliding contact with both side surfaces 21F and 21R. That is, the restricting surfaces of the restricting members 60F and 60R are in sliding contact with the side surfaces 21F and 21R of the intermediate transfer belt 21 at positions where the restricting surfaces run from the driving roller 23 toward the driven roller 26. By setting the positions of the regulating members 60F and 60R in this way, large depressions and undulations are prevented from occurring on the surface of the intermediate transfer belt 21.

  In the present embodiment, since the hardness of the primary transfer roller 22 and the resistance of the intermediate transfer belt 21 are set to predetermined values, transfer omission is prevented and a good image can be obtained. Hereinafter, a description will be given with reference to FIG.

  FIG. 3 is a diagram illustrating a state in which the intermediate transfer device 20 is in operation. In the present embodiment, the intermediate transfer belt 21 runs away from the rear side (right side in the figure) due to uneven thickness or the like. For this reason, during operation, the intermediate transfer belt 21 travels in a state where the rear side surface 21R of the intermediate transfer belt 21 and the rear side regulation surface 62R are in sliding contact. Here, it is known that when the regulating member is brought into sliding contact with the side surface 21R, the stress is transmitted to a position away from the side surface 21R, and a dent or undulation W is generated at this position. However, the waviness W is reduced to a certain extent by a method such as devising the positions of the restricting members 60F and 60R as described above.

  However, the present inventor has thought that when the deviation of the belt is large, the waviness W cannot be reduced sufficiently, and image defects such as transfer omission increase. Therefore, the present inventor conducted various experiments in order to reduce image defects such as transfer omission. As a result, it was independently found that this image defect tends to depend on the hardness of the primary transfer roller 22 and the electric resistance (belt resistance) of the intermediate transfer belt 21.

That is, in FIG. 3, when the deviation of the belt becomes large, it becomes difficult to completely eliminate the waviness W. However, the waviness W can be reduced by setting the hardness of the primary transfer roller 23 within a certain range. Further, by setting the volumetric electrical resistivity (belt resistance) of the intermediate transfer belt 21 within a certain range, even if a certain level of undulation W occurs, transfer omission is less likely to occur. Therefore, the present inventor has a low volume electric efficiency (belt resistance) [Ω · cm] of the intermediate transfer belt 21, a hardness (roller hardness) of the primary transfer roller 23 [Asuka C], and the above-described transfer omission. I investigated the relationship. The volume resistivity of the primary transfer roller was 1 × 10 ⁸ [Ω · cm]. The results are shown in the table below.

Roller hardness 24 25 38 52 75
Belt resistance 1E8 × × × × ×
1E9 × ○ ○ ○ ×
1E10 × ○ ○ ○ ×
1E11 × × × × ×
1E12 × × × × ×

In the above table, the case where transfer omission occurs is indicated by x, and the case where omission does not occur is indicated by o. In this experiment, it was confirmed that the undulation W itself was generated in all cases shown in the table. However, even if the waviness W occurs, the primary transfer roller 22 has a volume electric low efficiency (belt resistance) of the intermediate transfer belt 21 of 1 × 10 ⁹ [Ω · cm] or more and 1 × 10 ¹⁰ [Ω · cm] or less. When the hardness (roller hardness) is 25 [Asuka C] or more and 52 [Asuka C] or less, it was found that transfer loss hardly occurred. Further, it was found that when the hardness of the primary transfer roller 22 is 25 [Asuka C] or more and 70 [Asuka C] or less, transfer omission hardly occurs in a normal use environment. The present inventor considers the reason why the transfer omission does not occur as follows.

  That is, if the hardness of the primary transfer roller 22 is too hard, the elasticity of the roller 22 is lost and it becomes difficult to absorb the wavy W. For this reason, when the hardness of the roller 22 becomes harder than 52 [Asuka C], the wavy W becomes slightly larger, and when the hardness of the roller 22 becomes harder than 70 [Asuka C], the wavy W becomes larger. If the hardness of the roller 22 is too low, the deformed primary transfer roller 22 is difficult to return to its original shape. For this reason, even when the hardness of the roller 22 becomes softer than 25 [Asuka C], the waviness W increases. For these reasons, in order to reduce the waviness W, the hardness of the primary transfer roller 22 is 25 [Asuka C] or more and 70 [Asuka C] or less, preferably 25 [Asuka C] or more and 52 [Asuka C] or less. Good.

Further, if the volumetric electric low efficiency of the intermediate transfer belt 21 is too high, even if a slight undulation W occurs, a discharge due to the gap of the undulation W tends to occur, and a transfer omission due to a discharge root or the like tends to occur. For this reason, when the volumetric electric low efficiency of the intermediate transfer belt 21 is greater than 1 × 10 ¹⁰ [Ω · cm], transfer omission is likely to occur even with a small waviness W. Also, if the volumetric electric efficiency of the intermediate transfer belt 21 is too low, the transfer charge applied to the intermediate transfer belt 21 tends to spread in the lateral direction. Therefore, when a high voltage is applied to the primary transfer roller 22, the toner is laterally moved. It spreads out to cause image defects. To avoid this, the voltage range that can be applied to the primary transfer roller 22 becomes extremely narrow. For this reason, if the volumetric electric low efficiency of the intermediate transfer belt 21 is smaller than 1 × 10 ⁹ [Ω · cm], it becomes difficult to form a good image. For these reasons, in order to make it easy to obtain a good image even when undulation W occurs, the volumetric electrical efficiency (belt resistance) of the intermediate transfer belt 21 is 1 × 10 ⁹ [Ω · cm] or more 1 × 10 ¹⁰ [Ω · cm] or less is preferable.

As described above, the volumetric electric low efficiency of the intermediate transfer belt 21 is set to 1 × 10 ⁹ [Ω · cm] or more and 1 × 10 ¹⁰ [Ω · cm] or less, and the hardness of the primary transfer roller is 25 [Asuka C]. If it is 70 [Asuka C] or less, preferably 25 [Asuka C] or more and 52 [Asuka C] or less, the effect of reducing the undulation W and the effect of making it difficult for transfer omission to occur even if the undulation W occurs. As a result, it is thought that transfer loss is less likely to occur.

As the material of the intermediate transfer belt 21 described above, for example, polyimide can be used. That is, as described above, the intermediate transfer belt 21 preferably has a low volume electric efficiency of 1 × 10 ⁹ [Ω · cm] to 1 × 10 ¹⁰ [Ω · cm]. The intermediate transfer belt 21 preferably has high bending fatigue strength and is excellent in durability. As such a material, polyimide can be used.

  Further, in the first embodiment described above, the regulating members 60F and 60R are arranged close to both end sides in the axial direction of the drive roller 23. However, when the intermediate transfer belt 21 is shifted to one side of the rear side or the front side, a restricting member can be disposed close to one end side. Further, the restricting member can be disposed in proximity to a roller other than the drive roller 23.

Second Embodiment One of the features of the image forming apparatus of the second embodiment is that the hardness of the end 22B of the primary transfer roller 22 is lower than the hardness of the central portion 22A, as can be seen from FIG. It is the point which it was made to become. As a result, excessive transfer at the end 22B can be reduced, and an even better image can be obtained.

FIG. 4 is a top view of the intermediate transfer device 20 of the image forming apparatus according to the second embodiment of the present invention. The structure of the main part of the image forming apparatus and the intermediate transfer apparatus 20 is the same as that of the first embodiment (FIG. 1), and detailed description thereof is omitted. Moreover, the same code | symbol was shown to the component same as 1st Embodiment. The low volume efficiency (belt resistance) of the intermediate transfer belt 21 is set to 1 × 10 ⁹ [Ω · cm] or more and 1 × 10 ¹⁰ [Ω · cm] or less as discussed in the first embodiment.

  The intermediate transfer device 20 in FIG. 4 differs from the first embodiment (FIG. 2) in that the hardness of the primary transfer roller 22 is uniform in the first embodiment, whereas in FIG. This is that the hardness of the transfer roller 22 is such that the end 22B is lower than the center 22A. This prevents excessive transfer at the end 22B. This will be described below.

According to the experiment by the present inventor, in the transfer from the photosensitive drum 1 to the intermediate transfer belt 21 in the primary transfer region S, both end portions 22B are excessively transferred with respect to the central portion 22A of the primary transfer roller 22. I know it tends to be. This inventor examined this cause. As a result, the excessive transfer at the end portion 22B described above is mainly due to the strength of the contact force between the transfer belt 21 and the primary transfer roller 22 (around) compared to the central portion 22A of the primary transfer roller 22. It was thought that this may be due to the fact that the end 22B tends to become strong. Therefore, the present inventor conducted experiments by changing the hardness of the end 22B and the center 22A of the primary transfer roller 22 in order to prevent excessive transfer at the end 22B. Specifically, the experiment was performed by dividing the roller width into four equal parts and changing the hardness of the blocks at both ends and the central two blocks. In the experiment, the roller resistance (volume resistivity) of the primary transfer roller 22 was changed between 1 × 10 ⁶ [Ω · cm] and 1 × 10 ⁸ [Ω · cm]. In this experiment, the difference between the solid transfer remaining amount (ratio) at the central portion 22A and the solid transfer remaining amount (ratio) at the end 22B was examined under the condition that the transfer at the central portion 22A was optimal. The results are shown in the table below. The unit of hardness is [Asuka C].

When the roller resistance is 1 × 10 ⁶ [Ω · cm]
Central hardness Hardness at both ends Difference in residual transfer amount
28 28 0.08
45 28 0.01
45 45 0.11
70 45 0.03
70 70 0.13
When the roller resistance is 1 × 10 ⁸ [Ω · cm]
Central hardness Hardness at both ends Difference in residual transfer amount
28 28 0.05
45 28 0.01
45 45 0.08
70 45 0.02
70 70 0.10

  In the above table, if the difference in the remaining amount of solid transfer is large, it means that the solid transfer remaining at the end 22B is smaller than the solid transfer remaining at the central portion 22A, and the end 22B is excessively transferred. . On the contrary, if the difference in the remaining amount of solid transfer is small, it means that excessive transfer at the end portion is reduced and a good image can be obtained.

  As can be seen from the above table, by making the hardness of the end portion 22B of the primary transfer roller 22 lower than the hardness of the central portion 22A, the difference in the remaining amount of transfer is reduced and the transfer at the end portion 22B is performed. Excessiveness can be prevented. Thereby, uniform transfer can be performed and a good image can be obtained.

Further, as can be seen from the above table, the remaining transfer is lower when the roller resistance is as low as 1 × 10 ⁶ [Ω · cm] than when the roller resistance is as high as 1 × 10 ⁸ [Ω · cm]. The amount tends to increase. However, according to the present embodiment, by making the hardness of the end 22B of the primary transfer roller 22 lower than the hardness of the central portion 22A, even if the roller resistance is low, the solid transfer remaining amount is reduced. Uniform transfer can be performed. If the roller resistance is lowered, the transfer voltage can be lowered, and problems due to the voltage becoming too high can be prevented. Thus, in this embodiment, uniform transfer can be performed while lowering the roller resistance and lowering the transfer voltage.

Third Embodiment An image forming apparatus according to a third embodiment focuses on a method for manufacturing the intermediate transfer belt 21 (FIG. 1).

  As shown in FIG. 1, the intermediate transfer belt 21 includes a primary transfer roller 22, a drive roller 23, a secondary transfer backup roller 24, a tension roller 25, a driven roller 26, and a substantially parallel distance apart from each other. It is wound around and stretched. The intermediate transfer belt 21 is in contact with the photosensitive drum 1 at the outer peripheral surface in the primary transfer region S. Further, it is pressed against the photosensitive drum 1 by the primary transfer roller 22 from the inner peripheral surface. The transfer nip in the primary transfer region S is 1 to 2 mm, and the pressing force is 400 g to 500 gf. As the main component of the intermediate transfer belt 21, as described above, polyimide can be preferably used from the viewpoint of low volumetric electric efficiency, bending fatigue strength, and durability.

  Further, the surface of the photosensitive drum 1 has a photosensitive region composed of a photosensitive layer formed on the aluminum base tube at the center portion, and a region where the aluminum base tube is exposed at both ends. ing. In order to avoid contact between the exposed area of the aluminum base tube and the intermediate transfer belt 21, the width of the intermediate transfer belt 21 is usually narrower than the width of the photosensitive layer of the photosensitive drum 1. . In other words, the intermediate transfer belt 21 is disposed so that both side end portions of the outer peripheral surface thereof are in contact with the photosensitive region of the photosensitive drum 1.

  However, the present inventor has thought that if the width of the intermediate transfer belt 21 is narrower than the width of the photosensitive layer of the photosensitive drum 1 as described above, an image defect due to leakage or the like may occur easily. In particular, according to experiments by the present inventors, when the intermediate transfer belt 21 is made of polyimide, this image defect may occur easily. Therefore, the inventor investigated and investigated the cause of this image defect. As a result, in the above arrangement, both end portions of the intermediate transfer belt 21 are in contact with the photosensitive region of the photosensitive drum 1, so that the end portion of the intermediate transfer belt 21 is convex toward the photosensitive drum 1, thereby causing the photosensitive member. It has been found that the photosensitive layer in the region may be scraped off. Therefore, the present inventor paid attention to the last cutting stage when manufacturing the intermediate transfer belt 21. Hereinafter, a description will be given with reference to FIG.

  FIG. 5 is a diagram illustrating a method for manufacturing the intermediate transfer belt 21 of the present embodiment. The intermediate transfer belt 21 is cut by a cutter (blade) and processed into a predetermined shape (FIG. 5A). When the intermediate transfer belt 21 is cut, there are a surface into which the blade is inserted into the belt 21 (upper surface in the drawing) and a surface from which the inserted blade is removed (lower surface in the drawing) (FIG. 5B). ). Then, on the surface from which the inserted blade comes off, sagging that occurs when it is cut appears as a protrusion (FIG. 5C). This sagging easily damages the photoreceptor because the intermediate transfer belt 21 is made of a material having excellent bending fatigue strength and durability. In particular, when the intermediate transfer belt 21 is made of polyimide, the photosensitive member is easily damaged due to the characteristics of the material.

  Specifically, the present inventor made the intermediate transfer belt 21 from polyimide, and arranged the surface with the sagging in FIG. 5 and the surface without the sagging on the opposite side with respect to the photosensitive drum 1 respectively. As a surface to be contacted, a test for peeling of the photosensitive member in the photosensitive drum 1 was performed. As a result, when the non-sag surface of the intermediate transfer belt 21 is brought into contact with the photosensitive layer of the photosensitive drum 1, the intermediate transfer can be performed even if the A4 size 150 k sheet printing is rotated by the traveling distance of the photosensitive drum 1. The portion of the photoreceptor layer corresponding to the end portion of the belt 21 was not peeled off. On the other hand, when the sagging surface of the intermediate transfer belt 21 is brought into contact with the photosensitive drum 1, the intermediate transfer belt 21 is rotated at the travel distance of the photosensitive drum 1 corresponding to printing of A4 size 30 k sheets. A portion corresponding to the end portion was streaked, and the photoreceptor layer was peeled off when contact rotation was performed for printing 60 k sheets.

  From the above results, the surface of the intermediate transfer belt 21 that is in contact with the photosensitive drum 1 is the surface opposite to the sag generation surface that occurs when the intermediate transfer belt 21 is cut, so that the surface of the photosensitive drum 1 is damaged. It was found that the measures were effective. This effect is increased when the intermediate transfer belt 21 is made of polyimide.

  As described above, according to the present embodiment, the surface of the intermediate transfer belt 21 in contact with the photosensitive drum 1 is the surface opposite to the sag generation surface that occurs when the intermediate transfer belt 21 is cut. The scratches on the photosensitive drum 1 can be reduced and the life of the photosensitive drum 1 can be extended.

Fourth Embodiment An image forming apparatus according to a fourth embodiment includes a protrusion (bead) in the intermediate transfer device 20 instead of the regulating members 60F and 60R (FIG. 2) as shown in FIG. ) F and R are provided. In addition, in the image forming apparatus of the present embodiment, the length of the cleaning blade 27 is shorter than the length of the drive roller 23 as shown in FIG. As a result, color misregistration and cleaning failure can be prevented.

  FIG. 6 is a view showing a part of the intermediate transfer device 20 of the image forming apparatus according to the fourth embodiment of the present invention, and FIG. 6A corresponds to a sectional view taken along the dotted line AA in FIG. FIG. 6B is a cross-sectional view of the intermediate transfer belt 21, and FIG. 6C is a cross-sectional view of the drive roller 23.

  As shown in FIG. 6B, the intermediate transfer belt 21 is provided with a rear-side bead R and a front-side bead F on both end sides of the inner peripheral surface opposite to the outer peripheral surface in contact with the photosensitive drum 1. ing. In the present embodiment, the beads F and R are made of urethane rubber and have a width of 5 mm and a height of 1 mm.

  As shown in FIG. 6C, the driving roller 23 is provided with a front collar 26F and a rear collar 26R having diameters smaller than the diameter of the driving roller 23 at both ends of the rotating shaft. In addition, portions of the end surface of the drive roller 23 where the collars 26F and 26R are not attached become the front side regulation surface 23F and the rear side regulation surface 23R.

  Further, as shown in FIG. 6A, the intermediate transfer device 20 includes the intermediate transfer belt 21 (FIG. 6B) and the driving roller 23 (FIG. 6C) of the collars 26R and 26F. It arrange | positions so that the beads F and R may be located beside. The beads F and R are caught by the restriction surfaces 23F and 23R, and the movement of the intermediate transfer belt 21 in the axial direction is suppressed. Here, the distance between the inner side surface of the front bead F and the inner side surface of the rear bead R is designed to be slightly wider than the distance between the rear side regulating surface 23R and the front side regulating surface 23F.

  In the apparatus of FIG. 6A, the beads F, R of the intermediate transfer belt 21 are brought into sliding contact with the regulating surfaces 23F, 23R, the movement of the intermediate transfer belt 21 in the axial direction is restricted, and the intermediate transfer belt 21 travels. The position is stabilized. Specifically, in the present embodiment, the running position of the intermediate transfer belt 21 is stabilized by running the intermediate transfer belt 21 while being offset toward the front side.

  However, according to the experiments of the present inventors, the method of providing the beads F and R as described above tends to cause a cleaning failure. Therefore, in the present embodiment, as shown in FIG. 6A, the width of the belt cleaner 27 is made narrower than the width from the inner surface of the front bead F to the inner surface of the rear bead R. . The front-side end surface 27F and the rear-side end surface 27R of the belt cleaner 27 are arranged so as to enter further inside than the inner side surfaces of the beads F, R of the intermediate transfer belt 21. Thereby, defective cleaning can be prevented. Hereinafter, a description will be given with reference to FIG.

  FIG. 7 is a cross-sectional view for explaining the operation of the intermediate transfer device 20 of the image forming apparatus of this embodiment and the intermediate transfer device 20 of the comparative example. 7A shows the operation of the comparative apparatus 20 in which the rear side end face 27R of the cleaning blade 27 and the rear side regulating face 23R of the drive roller 23 are arranged in parallel, and FIG. 7B shows the operation of the cleaning blade 27. The operation of the apparatus 20 in which the rear side end face 27R is disposed on the inner side by a distance x than the rear side regulating face 23R of the driving roller 23 is shown.

  As described above, in the present embodiment, the intermediate transfer belt 21 is run while being offset toward the front side (left side in the figure). However, according to the experiment of the present inventor, as shown in FIG. 7A, when the shifting force of the belt 21 toward the front side becomes strong, the rear bead R is formed on the step between the driving roller 23 and the rear collar 26R. May run up diagonally. This state is canceled when a biasing force toward the rear side (right side in the figure) is applied, but the belt end portion temporarily rises, so that the cleaning condition of the belt cleaner 27 changes and the rear of the cleaning blade 27 changes. A phenomenon occurs in which the side turns (FIG. 7A). This may cause a cleaning failure on the rear side.

  The above blade turning phenomenon depends on the relationship between the position of the rear side regulating surface 23R and the position of the rear side end surface 23R of the belt cleaner 27. Therefore, as shown in FIG. 7B, the inventor changes the distance x from the rear side end surface 27R of the belt cleaner 27 to the rear side regulating surface 23R of the drive roller 23 to determine whether or not the blade is turned up. Examined. In the experiment, the width of the intermediate transfer belt 21 was about 350 mm, and the intermediate transfer belt 21 was mainly composed of polyimide. The results are shown in the table below.

Distance x [mm] Presence or absence of blade turnover If the blade is on the inside, + ○ None × Existence
-5 ×
-3 ×
0 ×
+3 ○
+5 ○

  As shown in the above table, it was found that when the distance x is 3 mm or more, the occurrence frequency of blade turning decreases, and when it exceeds 5 mm, the blade turning is almost eliminated. In other words, it was found that when the width of the belt cleaner was made 6 mm or more shorter than the width of the intermediate transfer belt 21, the frequency of blade turning was reduced, and when the width was made 10 mm or more, the blade turning was almost eliminated. As a result, even if the belt deviation control method using the beads 21R is used, if the end surface 27R of the belt cleaner 27 is placed on the inner side of the inner surface of the bead 21R of the intermediate transfer belt 21, the blade turns up. It was found that can be suppressed. This relationship is substantially the same when the width of the intermediate transfer belt 21 is changed.

  6, the intermediate transfer belt 21 is provided with the beads F and R, and the end surfaces 27F and 27R of the belt cleaner 27 are located on the inner side of the inner surfaces of the beads F and R of the intermediate transfer belt 21. Since the belt cleaner 27 is disposed so as to enter, color misregistration and cleaning failure can be prevented.

Fifth Embodiment One of the features of the image forming apparatus of the fifth embodiment is that, in the intermediate transfer apparatus 20, as shown in FIG. 8, the apparatus of the first embodiment (FIGS. 1 and 2). In addition to the provision of the regulating members 60R and 60F (FIG. 8 (a)), the end surfaces 27F and 27R of the belt cleaner 27 are arranged so as to be inside the inner side surfaces of the regulating members 60R and 60F (see FIG. 8A). 8 (b)). Thereby, in addition to preventing color misregistration and transfer loss, it is possible to prevent defective cleaning. The structure other than the intermediate transfer device 20 is the same as that of the first embodiment (FIG. 1).

  FIG. 8 is a diagram showing an intermediate transfer device 20 of an image forming apparatus according to a fifth embodiment of the present invention. FIG. 8A is a diagram corresponding to a sectional view taken along the dotted line BB in FIG. FIG. 8B is a view corresponding to a cross-sectional view taken along the dotted line AA in FIG. The apparatus 20 according to the present embodiment includes an intermediate transfer belt 21, a driving roller 23, restriction members 60 </ b> F and 60 </ b> R disposed on both outer sides in the width direction of the intermediate transfer belt, and a belt cleaner 27 that cleans the intermediate transfer belt 21. And have. The restricting members 60 </ b> F and 60 </ b> R restrict the travel position in the width direction of the intermediate transfer belt 21 by contact between the inner surface thereof and the end face of the intermediate transfer belt 21. Specifically, in the present embodiment, the running position of the intermediate transfer belt 21 is stabilized by running the intermediate transfer belt 21 while being offset toward the rear side.

  In the apparatus 20 of FIG. 8, the end surfaces 27F and 27R of the belt cleaner 27 are disposed so as to be inside the inner surfaces of the regulating members 60F and 60R. Thereby, defective cleaning can be prevented. Hereinafter, a description will be given with reference to FIG.

  FIG. 9 is a cross-sectional view of the intermediate transfer device 20 during the copying operation. FIG. 9A is a cross-sectional view similar to that of FIG. 8A, and FIG. 9B is the cross-sectional view of FIG. It is a figure in the cross section similar to a cross section.

  As described above, in the present embodiment, the intermediate transfer belt 21 is run while being offset toward the rear side (right side in the drawing). However, according to the experiment of the present inventor, as shown in FIG. 9A, when the shifting force of the belt 21 toward the rear side becomes strong, the rear side end portion of the belt 21 rises, and the intermediate transfer belt 21 is raised. The stress is transmitted to a position away from the side surface of the, and a dent is formed at this position. This depression causes undulations, and the state of the intermediate transfer belt 21 changes due to the undulations in the cross section of FIG. 9B, the cleaning condition of the belt cleaner 27 changes, the phenomenon that the blades turn up occurs, and defective cleaning occurs.

  The above blade turning phenomenon depends on the relationship between the position of the inner side surface of the rear side regulating member 60R and the position of the rear side end surface 27R of the belt cleaner 27. Therefore, as shown in FIG. 9B, the inventor changes the distance y from the inner side surface of the rear side regulating member 60R to the rear side end surface 27R of the belt cleaner 27 to examine whether or not the blade is turned up. It was. In the experiment, the width of the intermediate transfer belt 21 was about 350 mm, and the intermediate transfer belt 21 was mainly composed of polyimide. The results are shown in the table below.

Distance y [mm] Presence or absence of blade turnover If the blade is inside + ○ None × Existence
0 ×
+5 ×
+10 ○
+15 ○

  As can be seen from the above table, it was found that when the distance y is 10 mm or more, the frequency of blade turning decreases, and when the distance y exceeds 15 mm, the blade turning is almost eliminated. Thus, in the belt deviation regulating method using the regulating members 60R and 60F, if the end surfaces 27F and 27R of the belt cleaner 27 are placed inside the inner side surfaces of the regulating members 60R and 60F, the blade turns up. It was found that can be suppressed. This relationship is substantially the same when the width of the intermediate transfer belt 21 is changed.

  As described above, in the apparatus of FIG. 8, the restriction members 60F and 60R are provided, and the end faces 27F and 27R of the belt cleaner 27 are arranged so as to be inside the inner side surfaces of the restriction members 60F and 60R. And poor cleaning can be prevented.

Sixth Embodiment One of the features of the image forming apparatus of the sixth embodiment is that the intermediate transfer device 20 is provided with regulating members 60R and 60F outside the belt 21, as shown in FIG. In addition, beads F and R are provided at positions slightly away from the end face of the belt 21. As a result, the waviness of the belt can be prevented and transfer omission can be prevented. The structure other than the intermediate transfer device 20 is the same as that of the first embodiment (FIG. 1), and detailed description thereof is omitted.

  FIG. 10 is a view showing the intermediate transfer device 20 of the image forming apparatus according to the sixth embodiment of the present invention, and corresponds to a cross-sectional view taken along the dotted line BB in FIG. In the vicinity of both ends of the rotation shaft of the driving roller 23, restriction members 60F and 60R for restricting the movement of the intermediate transfer belt 21 in the axial direction are provided. The intermediate transfer belt 21 is provided with beads F and R. The beads F and R are made of urethane rubber and have a width of 5 mm and a height of 1 mm. The distance from the inner surface of the beads F and R to the side surface of the belt 21 is set to 10 mm or more and 15 mm or less. The width of the intermediate transfer belt 21 is about 350 mm, and the intermediate transfer belt 21 is mainly composed of polyimide. Collars 26F and 26R having a diameter 2 mm smaller than the diameter of the driving roller 23 are attached to the driving roller 23 in contact with the intermediate transfer belt 21. The beads F and R are caught by a step between the collars 26F and 26R and the driving roller 23, and suppress the movement of the intermediate transfer belt 21 in the axial direction.

  As described above, when the regulating members 60F and 60R are brought into sliding contact with the side surface of the intermediate transfer belt 21, the stress is transmitted to a position away from the side surface of the intermediate transfer belt 21, and a depression is formed at this position. Rippling occurs, causing transfer loss. Therefore, in this embodiment, in order to prevent the stress from being transmitted to a position away from the side surface, beads F and R are provided at positions separated from both side surfaces of the back surface of the intermediate transfer belt 21 by 10 mm or more and 15 mm or less. ing. As described above, since the beads F and R are pasted to a position away from the side surface of the intermediate transfer belt 21 to some extent (10 mm or more), the stress from the side surface is not transmitted to the inside of the beads F and R, and the beads F and R It is possible to prevent undulation that causes transfer omission on the inner side. In addition, if the distance between the inner side surface of the beads F and R and the side surface of the belt 21 is not too large (15 mm or less), there is no problem in operation. This relationship is substantially the same when the width of the intermediate transfer belt 21 is changed.

  Further, in this embodiment, since the deviation of the intermediate transfer belt 21 is suppressed by both the regulating members 60F and 60R and the beads F and R, the force applied to the side surface of the intermediate transfer belt 21 can be weakened. . Therefore, also from this viewpoint, it is possible to prevent undulations that cause transfer omission.

1 is a schematic diagram of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a top view of the intermediate transfer device 20 of the image forming apparatus according to the first embodiment of the present invention. FIG. 3 is a top view showing an operation of the intermediate transfer device 20 of the image forming apparatus according to the first embodiment of the present invention. FIG. 6 is a top view of an intermediate transfer device 20 of an image forming apparatus according to a second embodiment of the present invention. FIG. 6 is a diagram for explaining an image forming apparatus according to a third embodiment of the present invention. FIG. 6A is a cross-sectional view of the intermediate transfer device 20 and FIG. 6B is an intermediate transfer belt 21 for explaining an intermediate transfer device 20 of an image forming apparatus according to a fourth embodiment of the present invention. FIG. 6C is a cross-sectional view of the drive roller 23. Sectional drawing for demonstrating operation | movement of the intermediate transfer apparatus 20 of the image forming apparatus of the 4th Embodiment of this invention, and the intermediate transfer apparatus 20 of a comparative example. FIG. 8A is a cross-sectional view of an intermediate transfer device 20 of an image forming apparatus according to a fifth embodiment of the present invention. FIG. 8A corresponds to a cross-sectional view taken along a dotted line BB in FIG. 1, and FIG. The figure equivalent to sectional drawing in dotted line AA in 1. FIG. FIG. 9A is a sectional view showing the operation of the intermediate transfer device 20 of the image forming apparatus according to the fifth embodiment of the present invention, and FIG. 9A is a diagram corresponding to the sectional view taken along the dotted line BB in FIG. ) Is a view corresponding to a cross-sectional view taken along a dotted line AA in FIG. Sectional drawing of the intermediate transfer apparatus 20 of the image forming apparatus of the 6th Embodiment of this invention.

Explanation of symbols

1 Photosensitive drum (image carrier)
20 Intermediate transfer device 21 Intermediate transfer belt 21F Front end surface 21R of intermediate transfer belt Rear end surface of intermediate transfer belt
F Front side bead R Rear side bead 22 Primary transfer roller 23 Driving roller 23F Driving roller front side regulating surface 23R Driving roller rear side regulating surface 27 Belt cleaner 60F Front side regulating member 60R Rear side regulating member 62F Front side regulating Front side regulating surface 62R of member Rear side regulating surface of rear side regulating member

Claims (8)

An image carrier for holding toner;
An intermediate transfer belt wound around a plurality of rollers, stretched endlessly in a direction perpendicular to the width direction by rotation of the rollers, and an outer peripheral surface thereof in contact with the image carrier;
One of the plurality of rollers, the intermediate transfer belt is in contact with the intermediate transfer belt from the inner peripheral surface opposite to the outer peripheral surface in contact with the image carrier, a voltage is applied, and the toner is removed by electrostatic force. A transfer roller for transferring to the intermediate transfer belt;
The at least one roller of the plurality of rollers is disposed close to both ends or one end in the axial direction, and restricts movement of the intermediate transfer belt in the width direction by contacting a side surface of the intermediate transfer belt. A regulating member;
With
The volumetric electric low efficiency of the intermediate transfer belt is 1 × 10 ⁹ [Ω · cm] or more and 1 × 10 ¹⁰ [Ω · cm] or less, and the hardness of the transfer roller is 28 [Asuka C] or more and 70 [Asuka C] or less. An image forming apparatus.   2. The image forming apparatus according to claim 1, wherein the hardness of the transfer roller is 28 [Asuka C] or more and 52 [Asuka C] or less.   3. The image forming apparatus according to claim 1, wherein the end portion of the transfer roller has a lower hardness than the center portion. 4. An image carrier having a photoreceptor area and holding a toner image in the photoreceptor area;
A plurality of rollers are wound and stretched, run endlessly by rotation of the roller, have an outer peripheral surface and an inner peripheral surface, the inner peripheral surface is in contact with the plurality of rollers, and a side end portion of the outer peripheral surface One or both of the intermediate transfer belt is in contact with the photosensitive region of the image carrier, and the outer peripheral surface is a surface opposite to a sag generation surface generated when the intermediate transfer belt is cut;
An image forming apparatus comprising: An image carrier for holding toner;
A plurality of rollers are wound and stretched, and run endlessly in a direction perpendicular to the width direction by the rotation of the rollers, the outer peripheral surface is in contact with the image carrier, and the inner peripheral surface on the opposite side to the outer peripheral surface An intermediate transfer belt provided with protrusions near both ends in the width direction;
A belt cleaner for cleaning the outer peripheral surface of the intermediate transfer belt;
With
At least one of the plurality of rollers regulates movement of the intermediate transfer belt in the width direction by contact with an inner surface of the protrusion;
The width of the belt cleaner is narrower than the width from the inner side surface of the projection on one end side to the inner side surface of the projection on the other end side, and the end surface of the belt cleaner has the projection in the width direction. An image forming apparatus, wherein the image forming apparatus is disposed so as to enter the inside of the inner side surface of the image forming apparatus. An image carrier for holding toner;
An intermediate transfer belt wound around a plurality of rollers, stretched endlessly in a direction perpendicular to the width direction by rotation of the rollers, and an outer peripheral surface thereof in contact with the image carrier;
The intermediate transfer belt is moved in the axial direction by being arranged close to both end sides or one end side in the axial direction of at least one of the plurality of rollers, and a regulating surface contacting a side surface of the intermediate transfer belt. A regulating member that regulates,
A belt cleaner that cleans the outer peripheral surface of the intermediate transfer belt, and is arranged so that an end surface thereof is inside the width direction with respect to the restriction surface of the restriction member;
An image forming apparatus comprising: An image carrier for holding toner;
It is wound around a plurality of rollers and stretched, and travels endlessly in a direction perpendicular to the width direction by the rotation of the rollers, the outer peripheral surface is in contact with the image carrier, and is projected on the inner peripheral surface opposite to the outer peripheral surface An intermediate transfer belt in which the position of the inner surface of the protrusion is 10 mm or more and 15 mm or less from the side surface;
The at least one roller of the plurality of rollers is disposed close to both ends or one end in the axial direction, and restricts movement of the intermediate transfer belt in the width direction by contacting a side surface of the intermediate transfer belt. A regulating member;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein a main component of the intermediate transfer belt is polyimide.

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