JP2023026985A - Image forming apparatus - Google Patents

Abstract

To obtain stable cleaning property with a simple configuration when a cleaning device of an intermediate transfer body has three contact members.SOLUTION: First and second position regulation parts 38, 37 provided on a second support 34 for supporting three contact members are engaged with bearing members 251, 251 of two counter rollers 241, 242 of three counter rollers 241, 242, 243 with which the three contact members 311, 312, 313 are in contact with an intermediate transfer body 20 therebetween, thereby determining the position of the second support 34 with respect to a first support 26 for supporting the first, second, and third counter rollers 241, 242, 243.SELECTED DRAWING: Figure 5

Description

The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine using an electrophotographic system or an electrostatic recording system, or a multifunction machine having a plurality of these functions.

Conventionally, as an image forming apparatus using, for example, an electrophotographic system, an intermediate transfer system in which a toner image formed on a plurality of photoreceptors is primarily transferred onto an intermediate transfer body and then secondarily transferred onto a recording material such as paper. There is As the intermediate transfer member, an intermediate transfer belt composed of an endless belt is often used.

Attached matter such as toner remaining on the intermediate transfer belt without being transferred to the recording material (secondary transfer residual toner) is removed from the intermediate transfer belt by a cleaning device and collected. This cleaning device removes unnecessary toner images from the intermediate transfer belt, such as test toner images formed on the intermediate transfer belt for image density control, and toner images remaining on the intermediate transfer belt after jamming. Also used to remove from above. As such a cleaning device, an electrostatic cleaning device (electrostatic cleaning device) is known that employs an electrostatic cleaning method for electrostatically collecting adherents such as secondary transfer residual toner on the intermediate transfer belt. The electrostatic cleaning device has a cleaning member (electrostatic cleaning member) such as a brush roller as a contact member that contacts the surface of the intermediate transfer belt. Then, a voltage is applied to the cleaning member or the opposing member that contacts the cleaning member via the intermediate transfer belt, and a current flows between the cleaning member and the opposing member. As a result, adherents such as secondary transfer residual toner are electrostatically moved from the intermediate transfer belt to the cleaning member and removed from the intermediate transfer belt. Electrostatic cleaning devices are conventionally generally configured with two cleaning members to remove positively charged toner and negatively charged toner on the intermediate transfer belt.

In recent years, as image forming apparatuses have become faster and have higher image quality, electrostatic cleaning devices are required to have higher cleaning performance. Therefore, in order to improve the cleaning performance of the electrostatic cleaning device, it has been proposed to increase the number of cleaning members. Patent Documents 1 and 2 propose an electrostatic cleaning device having three cleaning members. Patent Document 2 proposes a configuration in which a cleaning member and a collection roller for electrostatically collecting toner collected by the cleaning member are combined into subunits, and the subunits are arranged in a casing. .

Japanese Patent No. 5939473 Japanese Patent No. 6264650

In order for the electrostatic cleaning device to properly perform cleaning, it is important that the amount of penetration of the cleaning member into the surface of the intermediate transfer belt is as set. If this intrusion amount becomes smaller than the set value, chances of contact between the cleaning member and the surface of the intermediate transfer belt decrease, or the electrostatic force for moving the toner decreases. Therefore, there is a possibility that the cleanability will be lower than expected. Conversely, if the amount of penetration exceeds the set value, the force acting between the cleaning member and the intermediate transfer belt will increase, and there is a possibility that the intermediate transfer belt and the cleaning member will deteriorate due to wear and the like. be. One of the reasons why the amount of intrusion does not conform to the set value is the variation in the size of the parts.

Here, as described above, in the configuration of Patent Document 2, a plurality of cleaning members are arranged in the casing as subunits. In this configuration, the number of parts that determine the positional relationship between the cleaning member and the surface of the intermediate transfer belt is large, and there is a possibility that the amount of penetration of the cleaning member into the intermediate transfer belt will vary greatly. In order to suppress this and obtain stable cleanability, it is necessary to improve the accuracy of the parts, which may lead to an increase in cost. Moreover, it is considered that this configuration tends to increase the cost due to the complication of the device configuration and the increase in the number of components.

Therefore, it is desirable to have a structure that can suppress variation in the amount of penetration of the cleaning member into the intermediate transfer belt by determining the positional relationship between the cleaning member and the intermediate transfer belt with as few parts as possible, and that can obtain stable cleaning performance. be

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to obtain stable cleaning performance with a simple structure when a cleaning device for an intermediate transfer member has three contact members.

The above object is achieved by an image forming apparatus according to the present invention. In summary, a representative configuration of the present invention includes an image carrier that carries a toner image, and a secondary transfer unit that secondarily transfers the toner image that has been primarily transferred from the image carrier in the primary transfer unit onto a recording material. a rotatable intermediate transfer member that is conveyed to transfer the intermediate transfer member, and a rotatable intermediate transfer member disposed downstream of the secondary transfer portion and upstream of the primary transfer portion with respect to the rotation direction of the intermediate transfer member, on the inner peripheral surface side of the intermediate transfer member; , first, second and third rollers in contact with the inner peripheral surface of the intermediate transfer body along the width direction substantially perpendicular to the moving direction of the surface of the intermediate transfer body, and at least one end in the width direction a first support that rotatably supports the first, second, and third rollers on the side of the intermediate transfer member; first, second, and third contact members that are in contact with the outer peripheral surface and contact the first, second, and third rollers via the intermediate transfer member; and at least the one end in the width direction. a second support that supports the first, second and third contact members on the side of the part; the first, second and third contact members and the first, second and third rollers; and a current supply means for supplying a current between each of the first, second and third contact members, wherein the third contact member causes the secondary transfer portion during an image forming operation. The absolute value of the current flowing when in contact with the image area on the intermediate transfer member immediately after passing through is the largest, and the first roller and the second roller are arranged in at least one of the width directions. The first supporting member is supported by the first supporting member on the end side via a first bearing member and a second bearing member, respectively. and a second position regulating portion that engages with the second bearing member, and the first and second position regulating portions engage the first and second bearings, respectively. The image forming apparatus is characterized in that the position of the second support relative to the first support is determined by engaging a member.

Another typical configuration of the present invention includes an image carrier that carries a toner image, and a secondary transfer portion that secondarily transfers the toner image that has been primarily transferred from the image carrier in the primary transfer portion onto a recording material. a rotatable intermediate transfer member to be conveyed to the intermediate transfer member, which is arranged downstream of the secondary transfer portion and upstream of the primary transfer portion with respect to the rotation direction of the intermediate transfer member, on the inner peripheral surface side of the intermediate transfer member; First and second rollers in contact with the inner peripheral surface of the intermediate transfer body along the width direction substantially perpendicular to the movement direction of the surface of the intermediate transfer body, and the first roller at least on one end side in the width direction. A first support that rotatably supports the first and second rollers; second and third contact members, one of the first, second and third contact members contacting the first roller via the intermediate transfer member and the other two contacting members first, second and third contact members respectively contacting the second roller via the intermediate transfer member; and a second support that supports the contact member, wherein the first roller and the second roller are respectively supported at least on the one end side in the width direction by a first bearing member and a second It is supported by the first support via two bearing members, and the second support includes a first position regulating portion that engages with the first bearing member, and the second bearing member. and a second position regulating portion that engages with the second support by engaging the first and second position regulating portions with the first and second bearing members, respectively. An image forming apparatus, wherein a position of a body relative to said first support is determined.

According to the present invention, when the intermediate transfer body cleaning device has three contact members, it is possible to obtain stable cleaning performance with a simple configuration.

1 is a schematic cross-sectional view of an image forming apparatus; FIG. 2 is a schematic cross-sectional view of the periphery of the cleaning device of Example 1. FIG. 4 is a schematic diagram for explaining a power supply mode of the cleaning device of Example 1. FIG. 3 is a schematic block diagram showing a control mode of the image forming apparatus; FIG. 2 is a schematic perspective view of the periphery of one end of the cleaning device of Example 1. FIG. It is the schematic side view seen in the arrow A direction in FIG.5(c). FIG. 10 is a schematic side view of the periphery of one end of a cleaning device of a modified example of Embodiment 1; FIG. 10 is a schematic cross-sectional view of the periphery of the cleaning device of Example 2; FIG. 11 is a schematic perspective view of the periphery of one end portion of the cleaning device of Example 2; FIG. 11 is a schematic cross-sectional view of the periphery of a cleaning device of a modified example of Embodiment 2; FIG. 11 is a schematic diagram for explaining another modification of the positioning configuration;

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

[Example 1]
1. Overall Configuration and Operation of Image Forming Apparatus FIG. 1 is a schematic cross-sectional view of an image forming apparatus 100 of this embodiment. The image forming apparatus 100 of this embodiment is a tandem printer that employs an intermediate transfer method.

Image forming apparatus 100 has four image forming units 1Y, 1M, 1C, and 1K that form yellow (Y), magenta (M), cyan (C), and black (K) images, respectively. The four image forming units 1Y, 1M, 1C, and 1K are arranged in a row along the movement direction of the flat portion of the intermediate transfer belt 20, which will be described later, which is arranged substantially horizontally. The image forming apparatus 100 can form a full-color image on the recording material S by electrophotography in accordance with an image signal transmitted from an external device such as a personal computer. For elements having the same or corresponding functions or configurations in the image forming units 1Y, 1M, 1C, and 1K, the suffixes Y, M, C, and K are omitted from the symbols indicating that they are elements for one of the colors. may be described in a comprehensive manner. In this embodiment, the image forming unit 1 includes photosensitive drums 11 (11Y, 11M, 11C, 11K), chargers 12 (12Y, 12M, 12C, 12K), exposure devices 13 (13Y, 13M, 13C, 13K), which will be described later. ), developing device 14 (14Y, 14M, 14C, 14K), primary transfer roller 21 (21Y, 21M, 21C, 21K), drum cleaning device 15 (15Y, 15M, 15C, 15K), etc. . The order (position) of the image forming units for each color is not limited to that of this embodiment. Also, the number of image forming units and the colors of images to be formed are not limited to those of this embodiment.

A photosensitive drum 11, which is a rotatable drum-shaped (cylindrical) photosensitive member (electrophotographic photosensitive member) as an image bearing member, moves in the direction of arrow R1 (counterclockwise direction) in FIG. process speed). The surface of the rotating photosensitive drum 11 is uniformly charged to a predetermined potential with a predetermined polarity (negative polarity in this embodiment) by a charger 12 as charging means. During the charging process, a predetermined charging bias (charging voltage) is applied to the charger 12 by a charging power source (not shown). The charged surface of the photosensitive drum 11 is scanned and exposed by an exposure device (laser scanner) 13 as an exposure means, and an electrostatic image (electrostatic latent image) is formed on the photosensitive drum 11 . The exposure device 13 irradiates the surface of the photosensitive drum 11 with laser light (image light) modulated based on image information from an external device. The electrostatic image formed on the photosensitive drum 11 is developed (visualized) by supplying toner as developer by the developing device 14 as developing means, and a toner image is formed on the photosensitive drum 11 . In the present embodiment, an exposure portion (image portion) on the photosensitive drum 11, in which the absolute value of the potential is lowered by being exposed based on image information after being uniformly charged, is charged with the charging polarity of the photosensitive drum 11. Toner charged to the same polarity (negative polarity in this embodiment) adheres (reversal development method). In this embodiment, the normal charge polarity of the toner, which is the charge polarity of the toner during development, is negative. During the developing process, a developing power supply (not shown) applies a predetermined developing bias (developing voltage) to a developing roller as a developer carrier (developing member) provided in the developing device 14 .

An intermediate transfer belt 20 formed of an endless belt is arranged to face the four photosensitive drums 11 . The intermediate transfer belt 20 is stretched over a plurality of stretching rollers 241 to 247 with a predetermined tension. A drive roller (for example, the tension roller 243 or the tension roller 246), which is one of the plurality of tension rollers, is rotationally driven. As a result, the intermediate transfer belt 20 rotates (rotates) in the direction of arrow R2 (clockwise direction) in FIG. 1 at a predetermined peripheral speed (process speed) corresponding to the peripheral speed of the photosensitive drum 11 . Further, the inner secondary transfer roller 247, which is another one of the plurality of tension rollers, functions as a member (counter electrode) facing the secondary transfer outer roller 23, which will be described later. The secondary transfer inner roller 247 is electrically grounded (connected to the ground). Primary transfer rollers 21Y, 21M, 21C, and 21K, which are roller-type primary transfer members as primary transfer means, are provided on the inner peripheral surface side of the intermediate transfer belt 20 corresponding to the respective photosensitive drums 11Y, 11M, 11C, and 11K. are placed. In this embodiment, the primary transfer roller 21 is arranged at a position where it contacts the photosensitive drum 11 via the intermediate transfer belt 20 . The primary transfer roller 21 is pressed toward the photosensitive drum 11 and comes into contact with the photosensitive drum 11 via the intermediate transfer belt 20. A primary transfer portion (primary transfer nip) T1 where the photosensitive drum 11 and the intermediate transfer belt 20 are in contact with each other. to form Among the plurality of tension rollers, the tension rollers other than the driving roller are driven to rotate as the intermediate transfer belt 20 rotates. The toner image formed on the photosensitive drum 11 is transferred (primarily transferred) onto the rotating intermediate transfer belt 20 by the action of the primary transfer roller 21 in the primary transfer portion T1. During the primary transfer process, the primary transfer roller 21 is supplied with a primary transfer power source (high voltage power source) E1 (FIG. 4), which is a DC voltage having a polarity opposite to the normal charging polarity of the toner (positive polarity in this embodiment). A transfer bias (primary transfer voltage) is applied. Thereby, the primary transfer current is supplied to the primary transfer portion T1. For example, during the primary transfer process, a primary transfer bias controlled at a constant voltage of about +1 to +3 KV is applied to the core metal of each primary transfer roller 21, and +20 when viewed from the primary transfer power supply E1 side to each primary transfer portion T1. A current of about +100 μA flows. For example, when forming a full-color image, the yellow, magenta, cyan, and black toner images formed on the photosensitive drums 11 are superimposed on the same image position (image area) on the intermediate transfer belt 20 . primary transfer sequentially. A plurality of tension rollers 241 to 247 and primary transfer rollers 21Y, 21M, 21C, and 21K are rotatably supported by a belt frame 26 (FIG. 5) as a first support, which will be described later.

A secondary transfer outer roller 23 that is a roller-type secondary transfer member as a secondary transfer means is arranged at a position facing the secondary transfer inner roller 247 on the outer peripheral surface side of the intermediate transfer belt 20 . The secondary transfer outer roller 23 is pressed toward the secondary transfer inner roller 247 and comes into contact with the secondary transfer inner roller 247 via the intermediate transfer belt 20, so that the intermediate transfer belt 20 and the secondary transfer outer roller 23 are brought into contact with each other. A contacting secondary transfer portion (secondary transfer nip) T2 is formed. The toner image formed on the intermediate transfer belt 20 is nipped and conveyed between the intermediate transfer belt 20 and the secondary transfer outer roller 23 by the action of the secondary transfer outer roller 23 at the secondary transfer portion T2. It is transferred (secondary transfer) onto a recording material (transfer material, recording medium, sheet) S. During the secondary transfer process, a secondary transfer power source (high voltage power source) E2 (FIG. 4) is applied to the secondary transfer outer roller 23 to direct current having a polarity opposite to the normal charging polarity of the toner (positive polarity in this embodiment). A secondary transfer bias (secondary transfer voltage), which is a voltage, is applied. Thereby, the secondary transfer current is supplied to the secondary transfer portion T2. For example, during the secondary transfer process, a constant-voltage-controlled secondary transfer bias of about +1 to +7 kV is applied to the core metal of the secondary transfer outer roller 23, and the secondary transfer power source E2 side is applied to the secondary transfer portion T2. A current of about +40 to +120 μA flows when viewed from the side. Recording materials S such as paper and plastic sheets are stored in cassettes 61 and 62 as recording material storage units. The recording material S is fed one by one from one of the cassettes 61 and 62 to the feeding and conveying path 81 by rotating one of the feeding rollers 71 and 72 as a feeding member. After that, the recording material S is conveyed to the secondary transfer portion T2 by a registration roller 74 as a conveying member in time with the toner image on the intermediate transfer belt 20 . Note that the positions and number of the recording material storage units are not limited to those of this embodiment. Further, a roller corresponding to the inner secondary transfer roller 247 in this embodiment is used as a secondary transfer member, and a secondary transfer bias having a polarity opposite to that of this embodiment (the same polarity as the normal charge polarity of the toner) is applied thereto. may be applied. In this case, a roller corresponding to the secondary transfer outer roller 23 in this embodiment may be used as a counter member (counter electrode) and electrically grounded.

The recording material S onto which the toner image has been transferred is conveyed to a fixing device (thermal fixing device) 5 as fixing means. The fixing device 5 heats and presses (heats and presses) the recording material S carrying the unfixed toner image, thereby fixing (melting and fixing) the toner image onto the recording material S. As shown in FIG. The recording material S on which the toner image has been fixed is discharged (output) through a discharge conveying path 82 to a discharge tray 64 provided outside the main body of the image forming apparatus 100 .

Attached matter such as toner remaining on the photosensitive drum 11 without being transferred to the intermediate transfer belt 20 (residual toner after primary transfer) is removed from the photosensitive drum 11 by a drum cleaning device 15 as photosensitive member cleaning means. be recovered. Adhered matter such as toner remaining on the intermediate transfer belt 20 without being transferred to the recording material S (secondary transfer residual toner) is cleaned by a cleaning device (belt cleaning device) 30 as intermediate transfer body cleaning means. It is removed from the belt 20 and collected. The cleaning device 30 will be described in more detail later.

In this embodiment, the intermediate transfer belt 20 is a multi-layered belt having a base layer (back layer), an elastic layer (intermediate layer), and a surface layer. The base layer is made of a resin such as polyimide or polycarbonate or various rubbers containing an appropriate amount of carbon black as an antistatic agent. The elastic layer is made of a material obtained by adding an appropriate amount of an ionic conductive agent to various rubbers such as CR rubber, urethane rubber, and silicone rubber. As the ion conducting agent, for example, an aliphatic sulfonate or the like is used. The surface layer is made of resin such as urethane resin and fluorine resin. The volume resistivity of the intermediate transfer belt 20 is, for example, 5×10 ⁸ to 1×10 ¹⁴ Ω·cm (23° C., 50% RH, 100 V applied). The surface resistivity of the intermediate transfer belt 20 is, for example, 5×10 ⁸ to 1×10 ¹⁴ Ω/□ (23° C., 50% RH, 100 V applied). In this embodiment, the intermediate transfer belt 20, the tension rollers 241 to 247, the primary transfer rollers 21Y, 21M, 21C, and 21K, and the cleaning device 30 are integrally attached to and detached from the apparatus body of the image forming apparatus 100. A possible intermediate transfer unit 22 is constructed.

2. Cleaning Device FIG. 2 is a schematic cross-sectional view of the vicinity of the cleaning device (belt cleaning device) 30 in this embodiment. The cleaning device 30 is arranged downstream of the secondary transfer portion T2 and upstream of the primary transfer portion T1 (most upstream primary transfer portion T1Y) with respect to the moving direction (rotating direction, conveying direction) of the surface of the intermediate transfer belt 20. It is Here, the positions such as upstream (most upstream), downstream (most downstream), and center in relation to the cleaning device 30 and its elements are positions in relation to the moving direction of the surface of the intermediate transfer belt 20, even if not specified. be.

In this embodiment, the cleaning device 30 is an electrostatic cleaning device (electrostatic cleaning device) that electrostatically collects adhering matter such as toner on the intermediate transfer belt 20 . In particular, in this embodiment, the cleaning device 30 is an electrostatic brush cleaning device using a rotatable roller-shaped conductive fur brush (conductive fur brush roller). The cleaning device 30 removes adherents such as secondary transfer residual toner remaining on the intermediate transfer belt 20 after the secondary transfer from the intermediate transfer belt 20 . The cleaning device 30 is also used to remove unnecessary toner images from the intermediate transfer belt 20, such as test toner images and toner images remaining after jam processing.

In this embodiment, the cleaning device 30 includes first, second and third cleaning members (electrostatic cleaning members, conductive members) as first, second and third contact members. , and third brushes 311 , 312 , 313 . The cleaning device 30 also has first, second and third recovery rollers 321, 322 and 323 as first, second and third recovery members. The cleaning device 30 also has first, second and third blades 331, 332 and 333 as first, second and third scraping members. The cleaning device 30 holds the brushes 311, 312, 313, the recovery rollers 321, 322, 323, and the blades 331, 332, 333, and stores the toner removed from the intermediate transfer belt 20. It has a housing 35 . The housing 35 is configured by a cleaning frame 34 and the like, which will be described later. Further, the cleaning device 30 has a conveying member 36 such as a screw. A first cleaning unit 301 is configured by the first brush 311, the first collection roller 321, the first blade 331, and the like. A second cleaning unit 302 is configured by the second brush 312, the second collecting roller 322, the second blade 332, and the like. A third cleaning unit 303 is configured by the third brush 313, the third collection roller 323, the third blade 333, and the like.

The first, second, and third brushes 311, 312, and 313 are composed of rotatable roller-shaped conductive fur brushes (conductive fur brush rollers). The first, second, and third brushes 311, 312, and 313 have an outer diameter of, for example, 21 mm when the brush fibers are not deformed by an external force. The brush fibers of the first, second, and third brushes 311, 312, and 313 have an electrical resistance value of, for example, 3×10 ⁵ to 1×10 ¹³ Ω/cm, and a fiber thickness of, for example, 2 to 15 Ω/cm. Constructed of denier, carbon-dispersed nylon fiber, acrylic fiber, polyester fiber, or the like. The first, second, and third brushes 311, 312, and 313 are made of metal rollers (metal rollers) as base materials at a density of, for example, 50,000 to 500,000/inch ² . It is configured by flocking hair on the rotating shaft material). In this embodiment, first, second, and second rollers, which are tension rollers of the intermediate transfer belt 20 , are provided at positions facing the first, second, and third brushes 311 , 312 , and 313 with the intermediate transfer belt 20 interposed therebetween. 3 opposing rollers 241, 242 and 243 are arranged respectively. The first, second and third brushes 311, 312 and 313 are brought into contact with the first, second and third facing rollers 241, 242 and 243 via the intermediate transfer belt 20, respectively. In this embodiment, the first, second, and third opposing rollers 241, 242, and 243 are composed of rotatable metal (in this embodiment, aluminum) rollers (metal rollers). At least one of the first, second, and third opposing rollers 241, 242, and 243 is a roller having an elastic layer formed of a conductive elastic body around a metal core (rotating shaft made of metal). (elastic roller) may be used. The first, second and third brushes 311, 312 and 313 are, for example, about 1.0 relative to the intermediate transfer belt 20 backed up by the first, second and third opposing rollers 241, 242 and 243 respectively. Arranged while maintaining an intrusion amount of ~2.0 mm. The penetration amount is the difference between the distance between the base material on which the brush fibers are implanted and the surface of the intermediate transfer belt 20, and the length of the brush fibers in the axial direction when the brush fibers are not deformed by an external force. be. In this embodiment, the amount of penetration is the sum of the radius of the brush roller and the radius of the opposing roller when the brush fibers are not deformed by an external force in a cross section substantially perpendicular to the direction of the axis of rotation of the brush roller. It is represented by a value obtained by subtracting the distance between the axes (the distance between the rotation centers) between the brush roller and the opposing roller from the thickness.

The first, second, and third brushes 311, 312, and 313 are rotationally driven in the arrow R3 direction (clockwise direction) in FIG. 2 by a driving motor (not shown) as driving means. That is, the first, second, and third brushes 311, 312, and 313 rotate so as to move in a direction opposite to the moving direction of the intermediate transfer belt 20 at the contact portion with the intermediate transfer belt 20, Rub the surface of 20. The first, second, and third brushes 311, 312, and 313 are rotationally driven at a peripheral speed of, for example, 20 to 80% of the peripheral speed of the intermediate transfer belt 20 (surface moving speed). Note that the first, second, and third facing rollers 241 , 242 , and 243 are driven to rotate as the intermediate transfer belt 20 rotates. The first, second, and third brushes 311 , 312 , and 313 are arranged such that the direction of the axis of rotation thereof is substantially orthogonal to the moving direction of the surface of the intermediate transfer belt 20 (here, also referred to as the “width direction”). arranged in parallel. In this embodiment, the lengths of the first, second, and third brushes 311 , 312 , and 313 in the rotation axis direction are shorter than the length (width) of the intermediate transfer belt 20 in the width direction. The lengths of the first, second, and third brushes 311 , 312 , and 313 in the rotation axis direction may be longer than the maximum image forming width on the intermediate transfer belt 20 in the width direction of the intermediate transfer belt 20 . The first, second, and third facing rollers 241 , 242 , and 243 are arranged so that their rotational axis directions are substantially parallel to the width direction of the intermediate transfer belt 20 . In this embodiment, the lengths of the first, second and third facing rollers 241, 242 and 243 in the direction of the rotation axis are the lengths of the first, second and third brushes 311, 312 and 313 in the direction of the rotation axis. equivalent to length. Here, when the facing roller is a driving roller for the intermediate transfer belt 20, the length of the facing roller in the direction of the rotation axis may be longer than the length of the brush facing the facing roller in the direction of the rotation axis. The length of the drive roller of the intermediate transfer belt 20 in the rotation axis direction is longer than the length (width) of the intermediate transfer belt 20 in the width direction. When the facing roller is an idler roller, the length of the facing roller in the direction of the rotation axis may be equal to the length of the brush facing the facing roller in the direction of the rotation axis.

A contact portion between the first brush 311 and the intermediate transfer belt 20 is a first contact portion CL1. A contact portion between the second brush 312 and the intermediate transfer belt 20 is a second contact portion CL2. A contact portion between the third brush 313 and the intermediate transfer belt 20 is a third contact portion CL3. The first contact portion CL<b>1 is a cleaning portion where toner is collected from the intermediate transfer belt 20 by the first brush 311 . Also, the second contact portion CL2 is a cleaning portion where toner is collected from the intermediate transfer belt 20 by the second brush 312 . Further, the third contact portion CL3 supplies a current to the intermediate transfer belt 20 by the third brush 313, as will be described later, to even out the bias of the ions in the intermediate transfer belt 20 (here, "discharge"). ) is performed. The third contact portion CL3 is also a cleaning portion where at least part of the toner from the intermediate transfer belt 20 is collected by the third brush 313. FIG. The first, second, and third contact portions CL1, CL2, and CL3 are located downstream of the secondary transfer portion T2 with respect to the moving direction of the surface of the intermediate transfer belt 20 and at the primary transfer portion T1 (most upstream primary transfer portion T1Y). ) is located upstream. In this embodiment, the first contact portion CL1 is located upstream of the second contact portion CL2 with respect to the movement direction of the surface of the intermediate transfer belt 20, and the second contact portion CL2 is positioned upstream of the third contact portion CL2. It is located upstream of the part CL3.

The first, second, and third collection rollers 321, 322, and 323 are composed of rotatable metal (in this embodiment, aluminum) rollers (metal rollers). The first, second, and third collection rollers 321, 322, and 323 each have an intrusion amount of about 1.5 to 2.5 mm with respect to the first, second, and third brushes 311, 312, and 313, respectively. kept and placed. Also, the first, second, and third collecting rollers 321, 322, and 323 are rotationally driven in the direction of arrow R4 (counterclockwise direction) in FIG. 2 by a driving motor (not shown) as driving means. be. That is, the first, second, and third collection rollers 321, 322, and 323 are in contact with the first, second, and third brushes 311, 312, and 313, respectively. 311, 312, and 313 are rotated so as to move in the forward direction. The first, second and third collecting rollers 321, 322 and 323 are rotationally driven at the same speed (peripheral speed) as the first, second and third brushes 311, 312 and 313, for example. The first, second, and third recovery rollers 321 , 322 , and 323 are arranged such that their rotational axis directions are substantially parallel to the width direction of the intermediate transfer belt 20 . In this embodiment, the lengths of the first, second, and third recovery rollers 321, 322, and 323 in the direction of the rotation axis are equal to the lengths of the first, second, and third brushes 311, 312, and 313 in the direction of the rotation axis. Longer than length.

The first, second and third blades 331, 332 and 333 are arranged in contact with the first, second and third recovery rollers 321, 322 and 323, respectively. The first, second, and third blades 331, 332, and 333 are plate-shaped members made of a rubber material such as urethane rubber as elastic members. The first, second, and third blades 331, 332, and 333 have a longitudinal direction arranged substantially parallel to the rotation axis direction of the first, second, and third recovery rollers 321, 322, and 323, and It has a predetermined length and a predetermined thickness in the transverse direction substantially perpendicular to the direction. The first, second, and third blades 331, 332, and 333 have an intrusion amount of, for example, about 0.5 to 2.0 mm with respect to the first, second, and third collection rollers 321, 322, and 323, respectively. kept and placed. The first, second, and third blades 331, 332, and 333 are arranged counter to the direction of rotation of the first, second, and third recovery rollers 321, 322, and 323 (the free ends are upstream in the direction of rotation). side)). In this embodiment, the longitudinal lengths of the first, second, and third blades 331, 332, and 333 are equal to the lengths of the first, second, and third collection rollers 321, 322, and 323 in the rotational axis direction. shorter than

The relationship between the lengths of the intermediate transfer belt 20, the brushes 311 to 313, the collection rollers 321 to 323, the blades 331 to 333, and the opposed rollers (idler rollers and drive rollers) in the width direction of the intermediate transfer belt 20 is as follows. It's okay to be Brush<blade<opposed roller (idler roller)<intermediate transfer belt<recovery roller<drive roller.

In this embodiment, during the image forming operation (more specifically, when cleaning the secondary transfer residual toner during the image forming operation), the first and second brushes 311 and 312 are mainly used to remove the secondary transfer residual toner. Recovery is performed and discharge is performed by the third brush 313 . That is, electric fields suitable for cleaning are formed between the first brush 311 and the first opposed roller 241 and between the second brush 312 and the second opposed roller 242 . Also, an electric field suitable for discharging is formed between the third brush 313 and the third opposed roller 243 . As a result, the secondary transfer residual toner on the intermediate transfer belt 20 is mainly attracted to the first and second brushes 311 and 312 and removed from the intermediate transfer belt 20, and the third brush 313 discharges the residual toner. done. At least part of the secondary transfer residual toner on the intermediate transfer belt 20 may be removed from the intermediate transfer belt 20 by the third brush 313 . In other words, the third brush 313 discharges the intermediate transfer belt 20 by injecting or discharging electric charges, and current flows in the same direction as the third brush 313 among the first and second brushes 311 and 312. Collects less toner than brushes. The toner attracted to the first, second, and third brushes 311, 312, and 313 is further transferred to the first, second, and third collection rollers 321, 322, and 323 by an electric field, and the first and second brushes 311, 312, and 313 , is scraped off by the third blades 331 , 332 , 333 . The toner scraped off from the first, second, and third collection rollers 321 , 322 , 323 is stored in the housing 35 and further transported by the conveying member 36 to a collection container (not shown) provided in the image forming apparatus 100 . ) are transported.

FIG. 3 is a schematic diagram for explaining a method of supplying power to the first, second and third brushes 311, 312 and 313 in this embodiment. In this embodiment, the first brush power supply (high-voltage power supply) E11, which is a DC power supply, applies a positive DC voltage, which is opposite in polarity to the normal charging polarity of the toner, to the first opposing roller 241 under constant current control. is applied with Also, in this embodiment, the first brush 311 is electrically floated, and the first recovery roller 321 is electrically grounded. In this embodiment, when cleaning the secondary transfer residual toner during the image forming operation, as an example, a current of +73 μA viewed from the first brush power supply E11 side (−73 μA viewed from the first brush 311 side) is applied. A current is supplied to the first brush 311 to flow through the first brush 311 . The current flowing through the first brush 311 as seen from the first brush power source E11 side, for example, is defined as the positive current flowing from the first brush power source E11 toward the first brush 311 (the same applies to the others). be.). Accordingly, in this embodiment, when the current flowing in the direction from the inner peripheral surface side to the outer peripheral surface side of the intermediate transfer belt 20 is represented by a positive value, as an example, +73 μA of toner on the intermediate transfer belt 20 is collected. is supplied to the first contact CL1.

Further, in this embodiment, the second brush power supply (high voltage power supply) E12, which is a DC power supply, applies a constant positive DC voltage, which is opposite in polarity to the normal charge polarity of the toner, to the second collection roller 322. Applied with current control. Also, in this embodiment, the second brush 312 is electrically floated, and the second opposing roller 242 is electrically grounded. In this embodiment, when cleaning the secondary transfer residual toner during the image forming operation, the second brush 312 is operated so that a current of +73 μA flows through the second brush 312 when viewed from the second brush power supply E12 side. 312 is supplied with current. Accordingly, in this embodiment, when the current flowing in the direction from the inner peripheral surface side to the outer peripheral surface side of the intermediate transfer belt 20 is represented by a positive value, as an example, −73 μA of toner on the intermediate transfer belt 20 is collected. A cleaning current for cleaning is supplied to the second contact portion CL2.

Further, in this embodiment, a DC voltage of positive polarity, which is opposite in polarity to the normal charging polarity of the toner, is applied to the third recovery roller 323 by the third brush power supply (high voltage power supply) E13, which is a DC power supply. Applied with current control. Also, in this embodiment, the third brush 313 is electrically floated, and the third opposing roller 243 is electrically grounded. In this embodiment, when cleaning the secondary transfer residual toner during the image forming operation, the third brush 313 is operated so that a current of +220 μA flows through the third brush 313 as viewed from the third brush power supply E13 side, for example. 313 is supplied with current. As a result, in this embodiment, when the current flowing in the direction from the inner peripheral surface side to the outer peripheral surface side of the intermediate transfer belt 20 is represented by a positive value, the bias of the ions in the intermediate transfer belt 20 is −220 μA as an example. is supplied to the third contact portion CL3. The discharge current will be explained in more detail later.

The constant current control is performed so that the currents flowing through the first, second and third brush power sources E11, E12 and E13 are substantially constant (approaching target values). This control adjusts the outputs of the brush power sources E11, E12, and E13. The following method is used as a method for constant current control of the output of a high-voltage power supply. That is, a current detection section (current detection circuit) is provided between the voltage output section of the high voltage power supply and the voltage application target, and the current generated from the high voltage power supply is detected by this current detection section. Then, based on the detection result of the current detection unit, the output of the high voltage power supply is adjusted so that the current generated by the high voltage power supply is substantially constant (approaching the target value). The first, second and third brush power sources E11, E12 and E13 are connected to the first, second and third brushes 311, 312 and 313 and the first, second and third opposed rollers 241, 242 and 243. constitute a current supply means for supplying a current between and respectively.

By supplying current to the first and second brushes 311 and 312 as described above, the toner on the intermediate transfer belt 20 is transferred between the first and second brushes 311 and 312 and the intermediate transfer belt 20. An electric field suitable for collection (cleaning field) is created. As a result, the secondary transfer residual toner on the intermediate transfer belt 20 is electrostatically attracted to the first and second brushes 311 and 312 and removed from the intermediate transfer belt 20 . On the first brush 311, among the secondary transfer residual toner on the intermediate transfer belt 20, mainly the positively charged toner (here, “reverse polarity toner”) that is opposite in polarity to the regular charging polarity of the toner is applied. Also called.) adheres. Further, on the second brush 312, among the secondary transfer residual toner on the intermediate transfer belt 20, mainly negatively charged toner (here, also referred to as “regular polarity toner”), which is the regular charging polarity of the toner. ) adheres. Further, the toner is removed from the first and second brushes 311 and 312 by an electric field formed between the first and second collection rollers 321 and 322 and the first and second brushes 311 and 312 . 2, transferred to the third collection rollers 321 and 322; Furthermore, the toner transferred to the first and second collection rollers 321 and 322 is scraped off from the first and second collection rollers 321 and 322 by the first and second blades 331 and 332 .

Here, most of the secondary transfer residual toner is removed from the intermediate transfer belt 20 by the first and second brushes 311 and 312 when cleaning the secondary transfer residual toner during the image forming operation. However, among the relatively small amount of secondary transfer residual toner that has passed through the first and second contact portions CL1 and CL2, the negatively charged normal polarity toner is removed from the intermediate transfer belt 20 by the third brush 313. be done. Further, at least part of the normal polarity toner is once collected by the third brush 313 and then reversed in polarity by discharge in the third brush 311 to become reversely charged toner and re-applied to the intermediate transfer belt 20 . It may adhere. Further, of the relatively small amount of secondary transfer residual toner that has passed through the first and second contact portions CL1 and CL2, the positively charged oppositely charged toner passes through the third contact portion CL3. The oppositely charged toner reattached from the third brush 313 and the oppositely charged toner passing through the third contact portion CL3 are transferred to the photosensitive drum 1 simultaneously with the primary transfer at the primary transfer portion T1 (for example, the most upstream primary transfer portion T1Y). and collected by the drum cleaning device 15 .

A power supply method in which a high-voltage power supply is arranged on the brush side, like the power supply method for the second and third brushes 312 and 313 in this embodiment, is called "external power supply." A power supply method in which a high-voltage power supply is arranged on the opposing roller side, like the power supply method for the first brush 311 in this embodiment, is called "internal power supply." The power feeding method (arrangement of power sources) for the first, second, and third brushes 311, 312, and 313 is not limited to that of the present embodiment. In view of the characteristics of various members such as the intermediate transfer belt 20, or the layout of the apparatus, the power supply method (arrangement of power sources) for the first, second, and third brushes 311, 312, and 313 can be arbitrarily selected. . At this time, for example, the polarity of the voltage output from the power supply is appropriately set so that the directions of currents supplied to the first, second, and third contact portions CL1, CL2, and CL3 are the same as in the present embodiment. be able to.

The positioning structure of the cleaning device 30 in this embodiment will be described later in detail.

3. Discharge Current In an intermediate transfer type image forming apparatus, electrical resistance of the intermediate transfer belt may increase due to energization during image forming operation. This phenomenon becomes remarkable when an ion conductive belt is used as the intermediate transfer belt. This is the case when the intermediate transfer belt has a plurality of layers, for example, a base material, an elastic layer and a surface layer, and an ion-conducting conductive agent is used to adjust the electric resistance of the elastic layer. In other words, when an ion-conductive belt is used as the intermediate transfer belt, positive ions and negative ions responsible for ion-conductivity receive force from an electric field generated in the belt by the flow of current. Positively charged cations move in the direction of the electric field, and negatively charged anions move in the direction opposite to the electric field. For example, consider a case where the normal charging polarity of toner is negative. In this case, for primary transfer, a positive voltage is applied to the primary transfer member in contact with the inner peripheral surface of the intermediate transfer belt, and the primary transfer portion is directed from the inner peripheral surface side to the outer peripheral surface side of the intermediate transfer belt. Current is supplied in a direction (herein also referred to as "outward direction"). Therefore, cations move toward the outer peripheral surface of the intermediate transfer belt, and negative ions move toward the inner peripheral surface of the intermediate transfer belt. For the secondary transfer, a positive voltage is applied to the secondary transfer member in contact with the outer peripheral surface of the intermediate transfer belt, and the secondary transfer portion moves from the outer peripheral surface side to the inner peripheral surface side of the intermediate transfer belt. A current is supplied in the direction toward (here, also referred to as “inward direction”). Therefore, ions in the intermediate transfer belt move in a direction opposite to that during the primary transfer (positive ions toward the inner peripheral surface, negative ions toward the outer peripheral surface). If the balance between the total amount of charge supplied to the intermediate transfer belt in the outward and inward directions is greatly disturbed, the ions in the intermediate transfer belt are biased, and the electrical resistance of the intermediate transfer belt increases. As the amount of repeated use of the intermediate transfer belt increases, the electrical resistance of the intermediate transfer belt increases. Image defects tend to occur due to discharge at the transfer portion and the secondary transfer portion.

In order to suppress the increase in the electric resistance of the intermediate transfer belt as described above and extend the life of the intermediate transfer belt, the intermediate transfer belt is arranged so as to even out the bias of the ions in the intermediate transfer belt due to the image forming operation. It is useful to supply current to the belt. A cleaning member (electrostatic cleaning member) of an electrostatic cleaning device can be used as a discharging member for supplying (“discharging”) a current so as to equalize the bias of ions in the intermediate transfer belt. The discharge member does not have to have a cleaning function, but for the sake of convenience, both the contact member mainly used for cleaning and the contact member mainly used for discharge are referred to as cleaning members. Sometimes. The contact member may be used for both cleaning and discharging purposes.

The current required to sufficiently even out the bias of the ions in the intermediate transfer belt during the image forming operation is typically the current suitable for collecting the secondary transfer residual toner on the intermediate transfer belt ( Here, it is also referred to as “optimal cleaning current”). For example, in a tandem-type full-color image forming apparatus, an outward current flows in four primary transfer portions and an inward current flows in one secondary transfer portion. current is likely to be greater than that of Therefore, if an inward current is supplied by the cleaning member to even out the ion bias in the intermediate transfer belt, the current required to be supplied to the intermediate transfer belt by the cleaning member is typically optimal. greater than the cleaning current.

Table 1 shows the relationship between currents supplied to the intermediate transfer belt 20 at each portion (primary transfer portion T1, secondary transfer portion T2, first and second contact portions CL1, CL2) during image forming operation in this embodiment. shows an example of

In Table 1, the value of the current in the direction from the inner peripheral surface of the intermediate transfer belt 20 to the outer peripheral surface (outward direction) is a positive value, and the current value from the outer peripheral surface to the inner peripheral surface of the intermediate transfer belt 20 The value of the current in the facing direction (inward direction) is represented by a negative (minus) value. In the example shown in Table 1, when the sum of the currents supplied by the primary transfer portion T1, the secondary transfer portion T2, the first and second contact portions CL1 and CL2 during the image forming operation is calculated, the outward current is 172 to 252 μA in absolute value. Therefore, there is a possibility that the ions in the intermediate transfer belt 20 are biased and the electrical resistance of the intermediate transfer belt 20 increases.

Here, the sum of current values supplied to the primary transfer portion T1, the secondary transfer portion T2, and the first, second, and third contact portions CL1, CL2, and CL3 during the image forming operation is It is assumed that "current balance" in which the intermediary transfer belt 20 is energized at the beginning of the period. At this time, in this embodiment, an inward current of 220 μA, for example, is supplied to the third contact portion CL3 during the image forming operation so as to make this current balance substantially zero. This discharge current is −220 μA when the current flowing in the direction from the inner peripheral surface side to the outer peripheral surface side (inward direction) of the intermediate transfer belt 20 is represented by a positive value. In this embodiment, by supplying such a discharge current to the third brush 311 during the image forming operation, the bias of the ions in the intermediate transfer belt 20 can be evened out. As a result, an increase in electrical resistance of the intermediate transfer belt 20 can be suppressed, and the service life of the intermediate transfer belt 20 can be extended. The control unit 50 can set the value of the discharge current for each print job, for example, by referring to a data table or the like set in advance and stored in the ROM 53 . The setting of the discharge current may vary depending on the type of recording material S used for image formation and the environment (at least one of the temperature and humidity inside or outside the image forming apparatus 100). For example, in this embodiment, the absolute value of the discharge current can be changed within the range of 210 to 240 μA depending on the environment.

On the other hand, in the configuration of the present embodiment, the current supplied to the first brush 311 during the image forming operation is around −60 to −90 μA (typically −73 μA) when viewed from the first brush 311 side, that is, It is known that good cleaning performance can be obtained by setting the current to about +60 to +90 μA (typically +73 μA) when viewed from the first brush power source E11 side. In addition, in the configuration of the present embodiment, the current supplied to the second brush 312 during the image forming operation is set to about +60 to +90 μA (typically +73 μA) when viewed from the second brush 312 side, so that good It has been found to provide cleanability. That is, in the configuration of this embodiment, the absolute value of the optimum cleaning current is around 60 to 90 μA, typically 73 μA. If the absolute value of the cleaning current is smaller than the absolute value of the optimum cleaning current, it may not be possible to attract enough toner to the brush roller for collection. Also, if the absolute value of the cleaning current is greater than the absolute value of the optimum cleaning current, there is a possibility that the toner that has once adhered to the brush roller will readily adhere to the intermediate transfer belt again.

As described above, the absolute value of the current flowing through the third brush 313, which mainly plays the role of discharging during the image forming operation, is the same as that of the first brush 313, which mainly plays the role of cleaning the toner during the image forming operation. It is larger than the absolute value of the current flowing through each of the second brushes 311 and 312 . The absolute value of the current flowing through the third brush 313, which mainly plays the role of discharging during this image forming operation, is the current suitable for collecting the secondary transfer residual toner on the intermediate transfer belt 20 (optimal cleaning). current).

Note that the set value of the discharge current is not limited to that of this embodiment. The discharge current is a current in a direction (inward direction in the present embodiment) to even out the bias of ions in the intermediate transfer belt 20 during image forming operation. The discharge current is typically within a range of ±50%, preferably within a range of ±30%, more preferably within a range of ±30% with respect to a value where the balance of the current applied to the intermediate transfer belt 20 during the image forming operation is 0. is approximately 0. It should be noted that the current having a value that makes the current balance approximately 0 means that the current has a value within a range of ±5% with respect to the value that makes the current balance 0. With such a set value, the effect of sufficiently suppressing an increase in the electrical resistance of the intermediate transfer belt 20 and sufficiently extending the life of the intermediate transfer belt 20 can be obtained. If this current is less than −50% of the value where the current balance is 0, the effect of suppressing the increase in the electrical resistance of the intermediate transfer belt 20 is insufficient, and the intermediate transfer belt 20 is sufficiently lowered. Life cannot be extended. On the other hand, if this current is more than +50% of the value at which the current balance is 0, ions may be biased in the opposite direction to the above. Of the primary transfer current, secondary transfer current, cleaning current, and discharge current, the target current value of the constant current control can be used to obtain the aforementioned current balance. In addition, among these, when the applied bias is subjected to constant voltage control, the average value of the current flowing due to the application of the bias and the target current value used for setting the target voltage value for the constant voltage control are set as described above. can be used to determine the current balance of

In more detail, the value of the optimum cleaning current can be represented by the following value when one brush is used alone. That is, the cleaning current that can minimize the amount of toner remaining on the intermediate transfer belt 20 after the untransferred toner of the toner image with the maximum toner amount on the intermediate transfer belt 20 passes through the cleaning portion of the brush. value. The maximum amount of toner borne on the intermediate transfer belt 20 is the amount (mg/cm ² ) of the toner image that can be formed on the intermediate transfer belt 20 in the image forming apparatus 100, which is the mass of toner per unit area. is the maximum amount of toner image applied.

Further, the value of the current supplied to the primary transfer portion T1, the secondary transfer portion T2, the first, second and third contact portions CL1, CL2 and CL3 during the image forming operation varies depending on the image on the intermediate transfer belt 20. It is represented by the value of the current when the region is passing through each of the above portions. Here, the image area on the photosensitive drum 1 and the intermediate transfer belt 20 is an area in which an image can be formed by being transferred to the recording material S and output from the image forming apparatus 100, and the non-image area is other than the image area. is the area of

Further, for example, during execution of an adjustment operation or the like other than during an image forming operation, among the absolute values of the currents supplied to the first, second and third contact portions CL, CL2 and CL3, the third contact portion CL3 There may be a period during which the absolute value of the current supplied to is not the maximum.

4. Control Mode FIG. 4 is a schematic block diagram showing a control mode of the main part of the image forming apparatus 100 of this embodiment. The image forming apparatus 100 has a control section (controller, control circuit) 50 . The control unit 50 includes a CPU 51 as arithmetic control means which is a central element for arithmetic processing, a memory (storage medium) such as a RAM 52 and a ROM 53 as storage means, and a signal input/output circuit (not shown). consists of A RAM 52, which is a rewritable memory, stores information input to the control unit 50, detected information, calculation results, etc., and a ROM 53 stores a control program, a data table obtained in advance, and the like. Data can be transferred and read between the CPU 51 and memories such as the RAM 52 and the ROM 53 .

The control unit 50 is connected to an operation unit and an image reading unit of the image forming apparatus 100 and an external device such as a personal computer. The control unit 50 controls each unit of the image forming apparatus 100 based on an instruction from the operation unit of the image forming apparatus 100, image data from the image reading unit, or an image forming signal (image data, control command) from an external device. image forming operation. FIG. 4 shows a primary transfer power source E1, a secondary transfer power source E2, and first, second and third brush power sources E11, E12 and E13 as representatives of each section of the image forming apparatus 100. FIG.

5. Positioning of the cleaning device The cleaning performance of a cleaning device that uses an electrostatic cleaning method is affected by the voltage applied to the cleaning member (contact member), the electrical resistance of the cleaning member, and the amount of penetration of the cleaning member into the intermediate transfer belt. be. If the penetration amount is too small, there are concerns that the cleaning member will not come into contact with the intermediate transfer belt, deteriorating the cleaning performance, and that the electric resistance of the cleaning member will decrease and the high voltage output will become too large. If the amount of penetration is too large, leakage may occur, the brush fibers of the brush roller as the cleaning member may fall down too much, causing the cleaning member to come out of contact with the intermediate transfer belt, and wear of the intermediate transfer belt and cleaning member. Acceleration of deterioration is a concern. In order to properly exhibit the cleaning performance of the cleaning device, the amount of penetration into the intermediate transfer belt of the cleaning member, which mainly plays the role of cleaning the toner during the image forming operation, should be the set value. This is very important. As for the cleaning member that mainly plays the role of discharging during the image forming operation, the accuracy required for the penetration amount to the intermediate transfer belt is lower than that of the cleaning member that mainly plays the role of cleaning the toner. .

As described above, in the configuration of Patent Document 2, the subunit having the cleaning member is positioned with respect to the casing, and this casing is positioned with respect to the belt unit holding the intermediate transfer belt. In this configuration, the amount of penetration of the cleaning member into the intermediate transfer belt is determined by the position of the casing with respect to the belt unit and the position of the opposing roller with respect to the belt unit. Therefore, there is a possibility that a comparatively large tolerance is imposed on the target amount of penetration, resulting in a large variation in the amount of penetration and a decrease in the stability of the cleaning performance.

Therefore, by determining the positional relationship between the cleaning member, particularly the cleaning member that mainly plays the role of cleaning the toner and the intermediate transfer belt, with as few parts as possible, variations in the penetration amount of the cleaning member are suppressed. is desired. In order to suppress variations in the amount of penetration of the brush roller as a cleaning member into the intermediate transfer belt, it is desirable to determine the axial distance between the brush roller and the opposing roller with as few parts as possible.

Therefore, in the present embodiment, the distance between the axes of the two brush rollers having high cleaning performance among the three brush rollers and the opposing roller (stretching roller of the intermediate transfer belt) disposed at the opposing position is regulated. to position the cleaning device. In this embodiment, the two brush rollers having high cleaning performance among the three brush rollers are the first and second brush rollers which mainly play the role of cleaning the toner during the image forming operation. These are brushes 311 and 312 . In this embodiment, the other one of the three brush rollers is the third brush 313 which mainly plays the role of discharging during the image forming operation. At this time, in this embodiment, the distance between the shafts of the two brush rollers and the opposing roller is determined with as few parts as possible. That is, in this embodiment, two position regulating portions are provided on at least one of the frames (supports) that rotatably support both ends of the three brush rollers in the rotation axis direction. Then, the two position regulating portions are engaged with the bearing members of the two opposing rollers arranged at positions facing the two brush rollers. As a result, it is possible to suppress variation in the amount of penetration of the brush roller, particularly the brush roller which mainly plays the role of cleaning the toner, with respect to the intermediate transfer belt, and improve the stability of the cleaning performance.

6. Details of Positioning Structure of Cleaning Device in this Embodiment Next, the positioning structure of the cleaning device 30 in this embodiment will be described in more detail. In this embodiment, regarding the image forming apparatus 100 and its elements, the front side of FIG. 1 is the front side, and the back side of FIG. 1 is the rear side. In this embodiment, the front-rear direction connecting the front side and the rear side of the image forming apparatus 100 is the direction of the rotation axis of the tension roller of the photosensitive drum 11 and the intermediate transfer belt 20 (the direction of the surface of the photosensitive drum 11 and the intermediate transfer belt 20). substantially parallel to the moving direction). Further, with respect to the image forming apparatus 100 and its elements, the up-down direction refers to up and down in the gravitational direction (vertical direction), but it does not mean just above or just below, but above the horizontal plane passing through the position or element of interest. , including the lower side.

FIG. 5A is a schematic perspective view showing the periphery of the front end of the cleaning device 30 in this embodiment. 5B and 5C are schematic perspective views showing the surroundings of the cleaning device 30 and the mounting portion of the cleaning device 30 in the intermediate transfer unit 22, respectively. 6 is a schematic side view (illustration of the intermediate transfer belt 20 is omitted) viewed in the direction of arrow A in FIG. 5(c). Although FIG. 5 shows only the configuration on the front side of the cleaning device 30 regarding the positioning configuration of the cleaning device 30, in this embodiment, the configuration on the rear side of the cleaning device 30 is the same (in the width direction of the intermediate transfer belt 20). approximately symmetrical with respect to a plane passing through approximately the center).

As described above, the cleaning device 30 has the housing 35 that holds the first, second and third cleaning units 301 , 302 and 303 and stores the toner removed from the intermediate transfer belt 20 . In this embodiment, the housing 35 of the cleaning device 30 serves as a second support body that rotatably supports both ends of the first, second, and third brushes 311, 312, and 313 in the rotation axis direction. It is configured with a frame 34 . In this embodiment, both ends of the first, second, and third collection rollers 321 , 322 , and 323 in the rotation axis direction are also rotatably supported by the cleaning frame 34 . The first, second, and third brushes 311, 312, and 313 are attached to the cleaning frame via first, second, and third brush bearing members 311a, 311b, and 311c, respectively, at both ends in the rotation axis direction. 34 is supported. Further, the first, second, and third collection rollers 321, 322, and 323 are provided with first, second, and third collection roller bearing members 321a, 322a, and 323a at both ends in the latitudinal direction of the rotation axis. is supported by the cleaning frame 34. In this embodiment, the cleaning frame 34 is composed of a plate-like member arranged along a plane substantially perpendicular to the rotation axis direction of the first, second and third brushes 311 , 312 and 313 . The cleaning frame 34 may be constructed of any suitable material, such as metal or metal.

In the present embodiment, the first, second, and third brushes 311 , 312 , and 313 , which are tension rollers of the intermediate transfer belt 20 , are provided at positions facing (contacting) with the intermediate transfer belt 20 interposed therebetween. First, second and third opposed rollers 241, 242 and 243 are arranged, respectively. In this embodiment, the first, second, and third opposed rollers 241, 242, and 243 are provided with first, second, and third bearing members 251, 252, and 253 at both ends in the rotation axis direction. are supported by the belt frame 26. Of the first, second, and third bearing members 251, 252, and 253, at least the first and second bearing members 251 and 252 have at least A part protrudes outside the belt frame 26 . In this embodiment, the first and second bearing members 251 and 252 each have a substantially cylindrical outer peripheral surface 251a that is substantially circular when viewed in the rotation axis direction of the first and second opposing rollers 241 and 242. 252 a protrudes outside the belt frame 26 . In this embodiment, the outer peripheral surfaces 251a and 252a of the first and second bearing members 251 and 252 can be engaged with a rotation stopping long hole 38 and a positioning hole 37 of the cleaning frame 34, which will be described later. Note that the first and second bearing members 251 and 252 may be appropriately arbitrary, such as ball bearings, roller bearings, and slide bearings. The outer peripheral surfaces 251a, 252a of the first and second bearing members 251, 252 are configured by the outer peripheral surfaces of outer rings of ball bearings or roller bearings, or the outer peripheral surfaces of slide bearings. The outer peripheral surfaces 251a and 252a of the first and second bearing members 251 and 252 may be made of any appropriate material such as metal.

In this embodiment, the cleaning frame 34 has a positioning hole 37 as one of the first and second position regulating portions and a rotation stopper as the other of the first and second position regulating portions. A long hole 38 is provided. In this embodiment, the positioning hole 37 regulates the inter-axis distance between the second brush 312 and the second opposing roller 242 arranged at the opposite position. Further, in this embodiment, the rotation-stopping long hole 38 regulates the inter-axis distance between the first brush 311 and the first opposing roller 241 arranged at the opposite position. As a result, the positioning hole 37 and the rotation stopping elongated hole 38 determine the position of the cleaning device 30 with respect to the belt frame 26 . In other words, in this embodiment, the cleaning frame 34 constitutes a position regulating member that determines the position of the cleaning device 30 with respect to the belt frame 26 . That is, the cleaning frame 34 regulates the axial distance between the first brush 311 and the first opposing roller 241 and the axial distance between the second brush 312 and the second opposing roller 242, thereby cleaning the cleaning device. 30 relative to the belt frame 26 is determined.

In this embodiment, the positioning hole 37 of the cleaning frame 34 is fitted with the second bearing member 252 . More specifically, in this embodiment, the positioning hole 37 has a substantially cylindrical inner peripheral surface 37a that is substantially circular when viewed in the rotational axis direction of the second opposing roller 242 . That is, in this embodiment, the positioning hole 37 is a round hole (through hole) that is substantially circular in plan view. The inner peripheral surface 37 a of the positioning hole 37 is fitted with the outer peripheral surface 252 a of the second bearing member 252 . That is, the positioning hole 37 and the second bearing member 252 are engaged so as to be rotatable about the rotation axis of the second opposing roller 242 . Thereby, the positioning hole 37 regulates the position of the second brush 312 in the direction between the axes of the second brush 312 and the second opposing roller 242 .

Further, in this embodiment, the rotation stopping elongated hole 38 of the cleaning frame 34 is provided with a first bearing member so as to be movable in a direction crossing the rotation direction about the rotation axis of the second opposed roller 242. 251. More specifically, in this embodiment, the rotation-stopping long hole 38 extends along the axial direction between the first opposed roller 241 and the second opposed roller 242 when viewed in the rotational axis direction of the first opposed roller 241. It has a substantially elongated cylindrical inner peripheral surface 38a that is elongated in the direction. In other words, in this embodiment, the rotation-stopping elongated hole 38 is an oblong hole (through hole) that is substantially oval in plan view. A surface of the inner peripheral surface 38 a of the rotation stopping elongated hole 38 extending along the direction between the axes of the first opposed roller 241 and the second opposed roller 242 corresponds to the outer peripheral surface of the first bearing member 251 . 251a. As a result, the rotation stop elongated hole 38 absorbs component tolerances in the direction along the axial direction of the first opposing roller 241 and the second opposing roller 242, and rotates around the rotational axis of the second opposing roller 242. The position of the first brush 311 in the rotating direction is regulated. That is, the rotation-stopping long hole 38 substantially regulates the position of the first brush 311 in the direction between the axes of the first brush 311 and the first opposed roller 241 .

After the cleaning device 30 is positioned as described above, it may be fixed to the belt frame 26 by any appropriate fixing means such as screws. For example, the cleaning frame 34 and the belt frame 26 may be fixed using screws between the positioning hole 37 and the rotation stopping slot 38 .

As described above, in this embodiment, the positioning hole 37 and the rotation stopping elongated hole 38 are engaged with the second bearing member 252 and the first bearing member 251, respectively, so that the cleaning device 30 can be positioned with respect to the belt frame 26. Determined. Thereby, the distance between the axes of the first brush 311 and the first opposed roller 241 and the distance between the axes of the second brush 312 and the second opposed roller 242 can be determined with high accuracy.

As described above, in this embodiment, the first and second brushes 311 and 312 mainly play the role of cleaning toner on the intermediate transfer belt 20 . Therefore, in this embodiment, the accuracy of the distance between the shafts of the first and second brushes 311 and 312 and the first and second opposing rollers 241 and 242 arranged at opposing positions thereof is increased. As a result, it is possible to suppress variations in the amounts of penetration of the first and second brushes 311 and 312 into the intermediate transfer belt 20 and stabilize the cleaning performance.

In this embodiment, the position regulating portion that engages with the second bearing member 252 is a positioning portion formed of a circular hole, and the position regulating portion that engages with the first bearing member 251 is formed of an oblong hole. It was used as a rotation stopper. In this embodiment, the second facing roller 242 is arranged above the first facing roller 241 in the direction of gravity. Example configurations are preferred. However, the present invention is not limited to such an aspect, and it is possible to appropriately set which bearing member of which opposed roller is used for positioning or for stopping rotation. Contrary to the present embodiment, the position regulating portion that engages with the first bearing member 251 is a positioning portion formed of a round hole, and the position regulating portion that engages with the second bearing member 252 is formed of an oblong hole. It is good also as a detent|rotation stop part.

7. MODIFIED EXAMPLE In this embodiment, the first and second bearing members 251 and 252 of the first and second opposed rollers 241 and 242 arranged at positions opposed to the first and second brushes 311 and 312 are A cleaning frame 34 was positioned. In other words, in this embodiment, the position of the cleaning frame 34 is controlled by engaging the first and second bearing members 251 and 252 with the rotation-stopping long hole 38 and the positioning hole 37 provided in the cleaning frame 34, respectively. decided. However, the present invention is not limited to such aspects.

As described above, by positioning the cleaning frame 34 with respect to the bearing member of the facing roller arranged at the position facing the two cleaning members mainly responsible for cleaning the toner on the intermediate transfer belt 20, The stability of cleaning performance can be enhanced. Therefore, for example, when the cleaning members mainly responsible for cleaning the toner on the intermediate transfer belt 20 are the second and third brushes 312 and 313, the following should be done. That is, the cleaning frame 34 is positioned with respect to the second and third bearing members 252 and 253 of the second and third opposed rollers 242 and 243 arranged at positions opposed to the second and third brushes 312 and 313. do it. For example, as shown in FIG. 7(a), the second and third bearing members 252 and 253 are engaged with the rotation stopping long hole 38 and the positioning hole 37 provided in the cleaning frame 34, respectively. The position of the cleaning frame 34 may be determined. When the second and third brushes 312 and 313 are the cleaning members that mainly clean the toner on the intermediate transfer belt 20, for example, the following is the case. That is, when cleaning the secondary transfer residual toner during the image forming operation, the second and third brushes 312 and 313 mainly collect the secondary transfer residual toner, and the first brush 313 discharges the secondary transfer residual toner. This is the case for configuration. In this configuration, electric fields suitable for cleaning are formed between the second brush 312 and the second opposing roller 242 and between the third brush 313 and the third opposing roller 243 . Also, in this configuration, an electric field suitable for discharging is formed between the first brush 311 and the first opposing roller 241 .

Further, for example, when the cleaning members mainly responsible for cleaning the toner on the intermediate transfer belt 20 are the first and third brushes 311 and 313, the following may be done. That is, the cleaning frame 34 is positioned with respect to the first and third bearing members 251 and 253 of the first and third opposed rollers 241 and 243 arranged at positions opposed to the first and third brushes 311 and 313. do it. For example, as shown in FIG. 7(b), the first and third bearing members 251 and 253 are engaged with the rotation-preventing oblong hole 38 and the positioning hole 37 provided in the cleaning frame 34, respectively. The position of the cleaning frame 34 may be determined. When the first and third brushes 311 and 313 are the cleaning members that mainly clean the toner on the intermediate transfer belt 20, for example, the following is the case. That is, when cleaning the secondary transfer residual toner during the image forming operation, the secondary transfer residual toner is mainly collected by the first and third brushes 311 and 313 and discharged by the second brush 312 . This is the case for configuration. In this configuration, electric fields suitable for cleaning are formed between the first brush 311 and the first opposed roller 241 and between the third brush 313 and the third opposed roller 243 . Also, in this configuration, an electric field suitable for discharging is formed between the second brush 312 and the second opposing roller 242 .

Here, in general, the longer the distance between the positioning location and the rotation stop location, the smaller the positional variation during attachment. Therefore, for example, as shown in FIG. 7B, positioning the cleaning frame 34 with respect to the first bearing member 251 and the third bearing member 253 may be preferable from the following point of view. . In other words, by adopting such a configuration, it is possible to suppress positional variations between the cleaning device 30 and the belt frame 26, and stabilize the amount of penetration of the three cleaning members into the intermediate transfer belt 20 on average.

7(a) and 7(b), similarly to the above, of the two position regulating portions respectively engaged with the two bearing members, which one is the positioning portion and which one is the rotation stopping portion. can be set as appropriate. Further, similarly to the above, the power supply method (arrangement of power supply) for each of the first, second, and third brushes 311, 312, and 313 may be internal power supply or external power supply.

Further, in this embodiment, regarding the positioning structure of the cleaning device 30, the structure of the front side of the cleaning device 30 and the structure of the rear side of the cleaning device 30 are the same (substantially symmetrical), but the present invention is not limited to such an aspect. do not have. For example, of the front and rear cleaning frames 34, only the front cleaning frame 34 shown in FIG. At least one end of the first and second opposing rollers 241 and 242 in the direction of the rotation axis is pivotally supported by bearing members 251 and 252 that can be engaged with the rotation stop elongated hole 38 and the positioning hole 37, respectively. and supported by the belt frame 26 via the bearing member. In this case, for example, as shown in FIG. 12(a), at the rear end, the convex portion or the like as the engaging portion 39 provided on the cleaning frame 34 on the end side may interfere with the belt on the end side. It may be fitted into a hole or recess as the engaged portion 27 provided in the frame 26 . The engaged portion 27 provided on the belt frame 26 has a circular hole on one side and an elongated hole on the other side, similar to the positioning hole and rotation-stopping elongated hole provided on the cleaning frame 34 in this embodiment. good. As a result, for example, the cleaning device 30 can be easily attached to and detached from the belt frame 26 by pulling it toward the front side of the image forming apparatus 100 and removing it.

Also, in this embodiment, the first and second position restricting portions are formed of holes provided in the cleaning frame 34 so as to surround the entire periphery of the bearing member with which they are engaged. is not limited to this. For example, as shown in FIG. 12(b), at least one of the first and second position regulating portions exposes at least part of the periphery of the bearing member with which it engages to the outside of the cleaning frame 34. It may be a groove shape or the like that is notched in the direction of the groove. The first and second position regulating portions only need to exhibit functions corresponding to the functions of the positioning portion and the rotation stopping portion by the positioning hole 37 and the rotation stopping elongated hole 38 in this embodiment. In FIG. 12(b), a portion of the position restricting portion 37 corresponding to the positioning hole 37 in this embodiment is notched in the circumferential direction. 38 illustrates a mode in which a part of the circumferential direction of the 38 is notched.

Further, in this embodiment, the first and second position regulating portions are engaged with the bearing member outside the belt frame 26 in the width direction of the intermediate transfer belt 20 (direction of the rotation axis of the opposing roller). is not limited to such an aspect. The first and second position regulating portions may be configured to engage with bearing members inside the belt frame 26 in the width direction of the intermediate transfer belt 20 .

8. Effect As described above, in the present embodiment, the image forming apparatus 100 transfers the toner image primarily transferred from the image carrier 11 at the primary transfer portion T1 to the secondary transfer portion T2. and a rotatable intermediate transfer member 20 conveyed for secondary transfer onto the recording material S, and an intermediate transfer member downstream of the secondary transfer portion T2 and upstream of the primary transfer portion T1 with respect to the rotation direction of the intermediate transfer member 20. First, second and third rollers 241 arranged on the inner peripheral surface side of the intermediate transfer member 20 and in contact with the inner peripheral surface of the intermediate transfer member 20 along the width direction substantially orthogonal to the moving direction of the surface of the intermediate transfer member 20 . , 242 and 243, a first support member 26 that rotatably supports the first, second and third rollers 241, 242 and 243 at least on one end side in the width direction, and an intermediate transfer member 20. , contact the outer peripheral surface of the intermediate transfer member 20 along the width direction, and contact the first, second, and third rollers 241, 242, and 243 via the intermediate transfer member 20, respectively. The first, second and third contact members 311, 312 and 313 are in contact with each other, and the first, second and third contact members 311, 312 and 313 are supported at least at one end side in the width direction. A current that supplies current between the second support 34, the first, second and third contact members 311, 312, 313 and the first, second and third rollers 241, 242, 243, respectively supply means E11, E12, E13; In this embodiment, among the first, second, and third contact members 311, 312, and 313, the third contact member 313 is used for intermediate transfer immediately after passing through the secondary transfer portion T2 during the image forming operation. The absolute value of the current flowing when in contact with the image area on the body is the largest, and the first roller 241 and the second roller 242 each have the first roller 241 and the second roller 242 at least on the one end side in the width direction. The first support member 26 supports the bearing member 251 and the second bearing member 252 , and the second support member 34 has a first position restricting portion 38 that engages with the first bearing member 251 . and a second position regulating portion 37 that engages with the second bearing member 252 are provided, and the first and second position regulating portions 38 and 37 are connected to the first and second bearing members 251, respectively. , 252 position the second support 34 relative to the first support 26 .

In this embodiment, the third contact member 311 is the most downstream of the first, second, and third contact members 311 , 312 , and 313 with respect to the moving direction of the surface of the intermediate transfer member 20 . In this embodiment, the intermediate transfer body 20 is formed of an endless belt, and the first, second and third rollers 241, 242 and 243 are rollers for stretching the intermediate transfer body 20. be. Further, in this embodiment, one of the first and second position restricting portions is supported by the bearing member with which it engages among the first and second bearing members 251 and 252 and the bearing member. The other of the first and second position regulating portions is fitted so as to allow the rotation of the second support 34 about the rotation axis of the roller that is attached to the first and second bearing members. It engages with the bearing member 251 or 252 with which it engages so as to restrict the rotation of the second support 34 and allow movement in a direction intersecting the direction of rotation. In this embodiment, the second support member 34 has a substantially circular hole 37 in plan view that constitutes one of the first and second position regulating portions, and A hole 38 having a substantially oval shape in plan view is provided to constitute the other side. Also, in this embodiment, the first, second and third contact members 311, 312, 313 are rotatable brush rollers, respectively.

As described above, among the first, second, and third contact members, the one arranged most upstream with respect to the moving direction of the surface of the intermediate transfer body 20 is called the first contact member 311, and the most downstream. The first roller 241 and the second roller 243 are arranged at least on the one end side in the width direction with the first bearing member 251 and the second contact member 313, respectively. The second support 34 is supported by the first support 26 via the second bearing member 253. The second support 34 includes a first position regulating portion 38 that engages with the first bearing member 251, a second A second position regulating portion 37 that engages with the bearing member 253 is provided, and the first and second position regulating portions 38 and 37 engage with the first and second bearing members 251 and 253, respectively. By doing so, the position of the second support 34 relative to the first support 26 may be determined.

Further, according to this embodiment, when the cleaning device 30 has three contact members, it is possible to suppress variations in the amount of penetration of the contact members into the intermediate transfer belt 20 with a simple configuration, thereby achieving stable cleaning performance. can be obtained.

[Example 2]
Another embodiment of the present invention will now be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of the first embodiment. Accordingly, in the image forming apparatus of the present embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof is omitted. do.

FIG. 8 is a schematic cross-sectional view of the vicinity of the cleaning device 30 in this embodiment. FIG. 9A is a schematic perspective view showing the periphery of the front end of the cleaning device 30 in this embodiment. 9B and 9C are schematic perspective views showing the surroundings of the cleaning device 30 and the mounting portion of the cleaning device 30 in the intermediate transfer unit 22, respectively. Although FIG. 9 shows only the configuration of the front side of the cleaning device 30 regarding the positioning configuration of the cleaning device 30, in the present embodiment, the configuration of the rear side of the cleaning device 30 is the same (in the width direction of the intermediate transfer belt 20). approximately symmetrical with respect to a plane passing through approximately the center).

In this embodiment, a first opposing roller 241 that is a tension roller for the intermediate transfer belt 20 is arranged at a position that faces (contacts) the first brush 311 with the intermediate transfer belt 20 interposed therebetween. In this embodiment, a second facing roller 242, which is a tension roller for the intermediate transfer belt 20, is placed at a position facing (abutting) the second and third brushes 312 and 313 with the intermediate transfer belt 20 therebetween. are placed. In this embodiment, the first and second opposed rollers 241 and 242 are supported by the belt frame 26 via first and second bearing members 251 and 252 at both ends in the rotation axis direction. At least a part of the first and second bearing members 251 and 252 protrudes outside the belt frame 26 with respect to the rotation axis direction of the first and second opposed rollers 241 and 242, respectively. Note that the first and second bearing members 251 and 252 may have the same configuration as described in the first embodiment.

As described above, in this embodiment, one of the three brush rollers is in contact with the opposing roller arranged at the opposite position through the intermediate transfer belt, and the other two are in contact with the opposing roller through the intermediate transfer belt. It abuts a common opposing roller placed in position. In this embodiment, the distance between the shafts of the one brush roller and the opposite roller arranged opposite thereto, and the distance between the other two brush rollers and the common opposite roller arranged opposite the other two brush rollers. The cleaning device is positioned by regulating the distance between the axes. In this embodiment, the positions of all the three brush rollers are regulated with respect to the facing rollers (two facing rollers) arranged at the facing positions. Therefore, any one of the three brush rollers may be a brush roller with high cleaning performance (mainly responsible for cleaning toner). Also, in this embodiment, as in the first embodiment, the distance between the shafts of the three brush rollers and the opposing roller is determined with as few parts as possible. That is, in this embodiment, two position regulating portions are provided on at least one of the frames (supports) that rotatably support both ends of the three brush rollers in the rotation axis direction. Then, the two position regulating portions are engaged with the bearing members of the two facing rollers. As a result, it is possible to suppress variations in the penetration amounts of the three brush rollers with respect to the intermediate transfer belt, thereby enhancing the stability of the cleaning performance. A more detailed description will be given below.

In this embodiment, the cleaning frame 34 has a positioning hole 37 as one of the first and second position regulating portions, and a rotation stop long hole as the other of the first and second position regulating portions. 38 and are provided. In this embodiment, the positioning holes 37 regulate the distance between the axes of the second and third brushes 312 and 313 and the second opposing roller 242 arranged at the opposite position. Further, in this embodiment, the rotation-stopping long hole 38 regulates the inter-axis distance between the first brush 311 and the first opposing roller 241 arranged at the opposite position. As a result, the positioning hole 37 and the rotation stopping elongated hole 38 determine the position of the cleaning device 30 with respect to the belt frame 26 . In other words, in this embodiment, the cleaning frame 34 constitutes a position regulating member that determines the position of the cleaning device 30 with respect to the belt frame 26 . That is, the cleaning frame 34 regulates the axial distance between the first brush 311 and the first opposing roller 241 and the axial distance between the second and third brushes 312 and 313 and the second opposing roller 242. Then, the position of the cleaning device 30 with respect to the belt frame 26 is determined. The configurations of the positioning hole 37 and the rotation-preventing elongated hole 38 in this embodiment are the same as the configurations of the positioning hole 37 and the rotation-preventing elongated hole 38 in the first embodiment, respectively.

In this embodiment, the positioning hole 37 of the cleaning frame 34 is fitted with the second bearing member 252 so as to be rotatable about the rotation axis of the second opposing roller 242 . Further, in this embodiment, the rotation stopping elongated hole 38 of the cleaning frame 34 is provided with a first bearing member so as to be movable in a direction crossing the rotation direction about the rotation axis of the second opposed roller 242. 251.

As described above, in this embodiment, the positioning hole 37 and the rotation stopping elongated hole 38 are engaged with the second bearing member 252 and the first bearing member 251, respectively, so that the cleaning device 30 can be positioned with respect to the belt frame 26. Determined. As a result, the distance between the axes of the first brush 311 and the first opposed roller 241 and the distance between the axes of the second and third brushes 312 and 313 and the second opposed roller 242 can be accurately determined. can be done.

Here, as described above, in this embodiment, any of the first, second, and third brushes 311, 312, and 313 may be the brush mainly responsible for cleaning the toner. . In this embodiment, as an example, the first, second, and third brushes 311, 312, and 313 have functions corresponding to the first, second, and third brushes 311, 312, and 313 in the first embodiment, respectively. shall have However, the first, second, and third brushes 311, 312, and 313 may each have functions corresponding to those described in the modified example of the first embodiment.

In this embodiment, the position regulating portion that engages with the second bearing member 252 is a positioning portion formed of a circular hole, and the position regulating portion that engages with the first bearing member 251 is formed of an oblong hole. It was used as a rotation stopper. In this embodiment, the second facing roller 242 is arranged above the first facing roller 241 in the direction of gravity. Example configurations are preferred. However, as explained in the embodiment, the present invention is not limited to such an aspect, and it is possible to appropriately set the bearing member of which opposed roller to be used for positioning or for stopping rotation. can. Contrary to the present embodiment, the position regulating portion that engages with the first bearing member 251 is a positioning portion formed of a round hole, and the position regulating portion that engages with the second bearing member 252 is formed of an oblong hole. It is good also as a detent|rotation stop part.

Further, as shown in FIG. 10, the second brush 312 is arranged at a position facing (abutting) not the second facing roller 242 but the first facing roller 241 with the intermediate transfer belt 20 interposed therebetween. may

Further, as in the first embodiment, only the front cleaning frame 34 shown in FIG. 9 of the front and rear cleaning frames 34 may have the first and second position regulating portions.

Also, as in the first embodiment, at least one of the first and second position regulating portions is designed to expose at least a portion of the circumference of the bearing member with which it engages to the outside of the cleaning frame 34. It may be a groove shape or the like that is notched in the direction of the groove.

As described above, in the present embodiment, the image forming apparatus 100 rotates the intermediate transfer member 20 downstream from the secondary transfer portion T2 and upstream from the primary transfer portion T1 with respect to the rotation direction of the intermediate transfer member 20. and in contact with the inner peripheral surface of the intermediate transfer body 20 along the width direction substantially orthogonal to the movement direction of the surface of the intermediate transfer body 20; A first support member 26 that rotatably supports the first and second rollers 241 and 242 on one end side, and an intermediate transfer member disposed on the outer peripheral surface side of the intermediate transfer member 20 along the width direction. First, second and third contact members 311, 312, 313 contacting the outer peripheral surface of the body 20, one of the first, second and third contact members 311, 312, 313 first, second and third contact members 311 contacting the first roller 241 via the intermediate transfer body 20 and the other two contacting the second roller 242 via the intermediate transfer body 20; 312, 313, and a second support 34 that supports the first, second and third contact members 311, 312, 313 at least on the one end side in the width direction. In this embodiment, the first roller 241 and the second roller 242 are arranged at least on the one end side in the width direction via the first bearing member 251 and the second bearing member 252, respectively. The second support 34 has a first position regulating portion 38 that engages with the first bearing member 251 and a second position regulating portion 38 that engages with the second bearing member 252 . A position regulating portion 37 is provided, and the first and second position regulating portions 38, 37 are engaged with the first and second bearing members 251, 252, respectively, so that the second support 34 is A position relative to the first support 26 is determined. In this embodiment, among the first, second and third contact members 311, 312 and 313, the first contact member 311 is arranged most upstream with respect to the moving direction of the surface of the intermediate transfer body 20, and the third The contact member 313 is arranged on the most downstream side with respect to the moving direction of the surface of the intermediate transfer body 20. The first contact member 311 contacts the first roller 241 via the intermediate transfer body 20, and the second and third contact members 313 and 313 contact members 312 and 313 contact the second roller 242 via the intermediate transfer member 20 . However, as described above, the first and second contact members 311 and 312 contact the first roller 241 via the intermediate transfer body 20, and the third contact member 313 contacts the third roller 241 via the intermediate transfer body 20. 2 rollers 242 may be used. Further, in this embodiment, the intermediate transfer body 20 is formed of an endless belt, and the first and second rollers 241 and 242 are rollers for stretching the intermediate transfer body 20 .

Further, according to this embodiment, the same effects as those of the first embodiment can be obtained, and further simplification of the apparatus configuration can be achieved.

[others]
Although the present invention has been described with reference to specific examples, the present invention is not limited to the above-described examples.

In the above-described embodiment, all the outputs of the power supplies that supply currents to the three contact members are under constant current control, but the output of at least one power supply may be under constant voltage control. Constant current control is control that adjusts the output of the power supply so that the voltage output by the power supply is substantially constant (approaching the target value).

In the above-described embodiments, the contact member was a brush roller having a rotatably supported metal rotary shaft member and a plurality of raised bristles provided on the peripheral surface of the rotating shaft member. A brush roller can be preferably used as the contact member from the viewpoint of good cleaning properties, but the contact member is not limited to this. Depending on other conditions such as the amount of toner to be removed, the contact member may be an elastic roller such as a rubber roller or a sponge roller in which conductive rubber or sponge is arranged on the peripheral surface of the rotating shaft member. Alternatively, a brush-like member that rubs against the intermediate transfer member without rotating may be used. Also, in the above-described embodiments, the recovery member was a metal roller. A metal roller can be preferably used as the recovery member from the standpoint of being simple in structure and relatively inexpensive, but it is not limited to this, and a conductive elastic roller similar to that described above may also be used. . In addition, in the above-described embodiment, the scraping member is made of a rubber blade, but the scraping member is not limited to this, and is made of an elastic material such as a rubber sheet or a PET sheet (resin sheet). A blade member that has been shaped can be preferably used.

Further, the cleaning device may not be provided with a collecting member, and the scraping member may directly scrape the surface of the contact member. Further, the contact member does not need to be moved electrostatically when moving the toner on the intermediate transfer member, and may be moved physically. In this way, when the contact member mainly physically moves and collects the toner, the contact member arranged most downstream of the two contact members with respect to the moving direction of the surface of the intermediate transfer member. It can be said that the cleaning performance of is the lowest. In other words, in such a case, it can be said that the two contact members on the upstream side of the three contact members are the contact members with high cleaning performance (mainly responsible for cleaning the toner).

1 image forming unit 11 photosensitive drum 20 intermediate transfer belt 26 belt frame 30 cleaning device 34 cleaning frame 241, 242, 243 opposed roller 251, 252, 253 bearing member 311, 312, 313 cleaning member (contact member)

Claims (12)

an image carrier that carries a toner image;
a rotatable intermediate transfer member that conveys a toner image that has been primarily transferred from the image bearing member at the primary transfer portion so as to be secondarily transferred onto a recording material at the secondary transfer portion;
It is arranged downstream of the secondary transfer portion and upstream of the primary transfer portion with respect to the rotation direction of the intermediate transfer member and on the inner peripheral surface side of the intermediate transfer member, and substantially perpendicular to the moving direction of the surface of the intermediate transfer member. first, second and third rollers in contact with the inner peripheral surface of the intermediate transfer member along the width direction;
a first support that rotatably supports the first, second, and third rollers on at least one end side in the width direction;
The rollers are arranged on the outer peripheral surface side of the intermediate transfer body, contact the outer peripheral surface of the intermediate transfer body along the width direction, and contact the first, second and third rollers via the intermediate transfer body. contacting first, second and third contact members;
a second support that supports the first, second and third contact members at least on the one end side in the width direction;
current supply means for supplying current between the first, second and third contact members and the first, second and third rollers, respectively;
has
Of the first, second and third contact members, the third contact member is in contact with the image area on the intermediate transfer member immediately after passing through the secondary transfer portion during image forming operation. When the absolute value of the current flowing is the largest,
The first roller and the second roller are supported by the first support via a first bearing member and a second bearing member, respectively, at least on the one end side in the width direction,
The second support is provided with a first position regulating portion that engages with the first bearing member and a second position regulating portion that engages with the second bearing member. , wherein the position of the second support relative to the first support is determined by engagement of the first and second position regulating portions with the first and second bearing members, respectively. Image forming device. 2. The method according to claim 1, wherein the third contact member is arranged most downstream of the first, second and third contact members with respect to the moving direction of the surface of the intermediate transfer member. Image forming device. an image carrier that carries a toner image;
a rotatable intermediate transfer member that conveys a toner image that has been primarily transferred from the image bearing member at the primary transfer portion so as to be secondarily transferred onto a recording material at the secondary transfer portion;
It is arranged downstream of the secondary transfer portion and upstream of the primary transfer portion with respect to the rotation direction of the intermediate transfer member and on the inner peripheral surface side of the intermediate transfer member, and substantially perpendicular to the moving direction of the surface of the intermediate transfer member. first, second and third rollers in contact with the inner peripheral surface of the intermediate transfer member along the width direction;
a first support that rotatably supports the first, second, and third rollers on at least one end side in the width direction;
The rollers are arranged on the outer peripheral surface side of the intermediate transfer body, contact the outer peripheral surface of the intermediate transfer body along the width direction, and contact the first, second and third rollers via the intermediate transfer body. contacting first, second and third contact members;
a second support that supports the first, second and third contact members at least on the one end side in the width direction;
has
Of the first, second, and third contact members, the third contact member is arranged most downstream with respect to the moving direction of the surface of the intermediate transfer body,
The first roller and the second roller are supported by the first support via a first bearing member and a second bearing member, respectively, at least on the one end side in the width direction,
The second support is provided with a first position regulating portion that engages with the first bearing member and a second position regulating portion that engages with the second bearing member. , wherein the position of the second support relative to the first support is determined by engagement of the first and second position regulating portions with the first and second bearing members, respectively. Image forming device. an image carrier that carries a toner image;
a rotatable intermediate transfer member that conveys a toner image that has been primarily transferred from the image bearing member at the primary transfer portion so as to be secondarily transferred onto a recording material at the secondary transfer portion;
It is arranged downstream of the secondary transfer portion and upstream of the primary transfer portion with respect to the rotation direction of the intermediate transfer member and on the inner peripheral surface side of the intermediate transfer member, and substantially perpendicular to the moving direction of the surface of the intermediate transfer member. first, second and third rollers in contact with the inner peripheral surface of the intermediate transfer member along the width direction;
a first support that rotatably supports the first, second, and third rollers on at least one end side in the width direction;
The rollers are arranged on the outer peripheral surface side of the intermediate transfer body, contact the outer peripheral surface of the intermediate transfer body along the width direction, and contact the first, second and third rollers via the intermediate transfer body. contacting first, second and third contact members;
a second support that supports the first, second and third contact members at least on the one end side in the width direction;
has
Of the first, second, and third contact members, the first contact member is arranged most upstream with respect to the moving direction of the surface of the intermediate transfer body, and the second contact member is located near the surface of the intermediate transfer body. is located furthest downstream with respect to the direction of movement of the surface,
The first roller and the second roller are supported by the first support via a first bearing member and a second bearing member, respectively, at least on the one end side in the width direction,
The second support is provided with a first position regulating portion that engages with the first bearing member and a second position regulating portion that engages with the second bearing member. , wherein the position of the second support relative to the first support is determined by engagement of the first and second position regulating portions with the first and second bearing members, respectively. Image forming device. 5. The intermediate transfer member comprises an endless belt, and the first, second and third rollers are rollers for stretching the intermediate transfer member. The image forming apparatus according to any one of . an image carrier that carries a toner image;
a rotatable intermediate transfer member that conveys a toner image that has been primarily transferred from the image bearing member at the primary transfer portion so as to be secondarily transferred onto a recording material at the secondary transfer portion;
It is arranged downstream of the secondary transfer portion and upstream of the primary transfer portion with respect to the rotation direction of the intermediate transfer member and on the inner peripheral surface side of the intermediate transfer member, and substantially perpendicular to the moving direction of the surface of the intermediate transfer member. first and second rollers in contact with the inner peripheral surface of the intermediate transfer body along the width direction;
a first support that rotatably supports the first and second rollers on at least one end side in the width direction;
First, second and third contact members arranged on the outer peripheral surface side of the intermediate transfer member and in contact with the outer peripheral surface of the intermediate transfer member along the width direction, the first, second and third contact members One of the third contact members is in contact with the first roller via the intermediate transfer member, and the other two are in contact with the second roller via the intermediate transfer member. second and third contact members;
a second support that supports the first, second and third contact members at least on the one end side in the width direction;
has
The first roller and the second roller are supported by the first support via a first bearing member and a second bearing member, respectively, at least on the one end side in the width direction,
The second support is provided with a first position regulating portion that engages with the first bearing member and a second position regulating portion that engages with the second bearing member. , wherein the position of the second support relative to the first support is determined by engagement of the first and second position regulating portions with the first and second bearing members, respectively. Image forming device. Among the first, second, and third contact members, the first contact member is arranged most upstream with respect to the moving direction of the surface of the intermediate transfer body, and the third contact member is located near the surface of the intermediate transfer body. The first contact member contacts the first roller through the intermediate transfer member, and the second and third contact members contact the intermediate transfer member. 7. The image forming apparatus according to claim 6, wherein the second roller is brought into contact with the second roller through a contact. Among the first, second, and third contact members, the first contact member is arranged most upstream with respect to the moving direction of the surface of the intermediate transfer body, and the third contact member is located near the surface of the intermediate transfer body. The first and second contact members contact the first roller through the intermediate transfer member, and the third contact member contacts the intermediate transfer member. 7. The image forming apparatus according to claim 6, wherein the second roller is brought into contact with the second roller through a contact. 9. The intermediate transfer member according to claim 6, wherein the intermediate transfer member comprises an endless belt, and the first and second rollers are rollers for stretching the intermediate transfer member. 2. The image forming apparatus according to item 1. One of the first and second position regulating portions is centered about the bearing member with which it engages and the rotation axis of the roller supported by the bearing member. and the other of the first and second position regulating portions is engaged with the first and second bearing members. 10. The bearing member is engaged with the bearing member on the one side to restrict the rotation of the second support and permit the movement in the direction intersecting the direction of rotation. The image forming apparatus according to any one of . In the second support, a substantially circular hole in plan view that constitutes one of the first and second position regulating portions and the other of the first and second position regulating portions are formed. 11. The image forming apparatus according to claim 10, wherein a substantially oval hole is provided in plan view. 12. The image forming apparatus according to claim 1, wherein each of said first, second and third contact members is a rotatable brush roller.

Images