Image forming apparatus

Abstract

The present application relates to an image forming apparatus including an intermediate transfer belt, a brush in contact with the intermediate transfer belt at a cleaning portion, and a controller. The controller controls to perform an image forming operation in which toner formed on the intermediate transfer belt is transferred to a recording material and an adjustment operation in which an adjustment toner image is formed on the intermediate transfer belt. The controller controls a driving portion in the image forming operation so that the brush rotates at a first circumferential speed Vr when transfer residual toner remaining in the intermediate transfer belt is removed from the intermediate transfer belt by the brush, and the brush rotates at a second circumferential speed Vp faster than the first circumferential speed Vr when the adjustment toner image is removed from the intermediate transfer belt by the brush.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus, such as a copier, printer, fax machine, or multifunction machine having multiple of these functions, using electrophotographic or electrostatic recording methods. Background Technology

[0002] Traditionally, some image forming devices using electrophotographic methods, such as printers and copiers, employ an intermediate transfer method. In this method, a toner image is formed on an image carrier member, such as a photosensitive drum; this toner image is transferred from the image carrier member to an intermediate transfer member in a primary transfer section; and then the toner image is transferred a second time from the intermediate transfer member to a recording material such as paper in a secondary transfer section. An intermediate transfer belt, often composed of a ring-shaped tape, is frequently used as the intermediate transfer member.

[0003] In the secondary transfer section, toner residue on the intermediate transfer belt that was not transferred to the recording material (transfer residue toner) is removed from the intermediate transfer belt and collected by a cleaning device in the cleaning section. As a method for cleaning the intermediate transfer belt, electrostatic cleaning is employed. Electrostatic cleaning cleans the intermediate transfer belt by applying a voltage to a conductive cleaning member arranged in contact with the intermediate transfer belt, causing the toner to be electrostatically attracted from the intermediate transfer belt to the cleaning member. As the cleaning member, a conductive brush (conductive brush roller) that rotates in contact with the intermediate transfer belt is frequently used (electrostatic brush cleaning method).

[0004] Japanese Patent No. 5153431 proposes a configuration in which the voltage applied to the brush and the number of times the brush rotates are controlled based on the detection result of the current flowing through the brush.

[0005] Incidentally, in image forming equipment using an intermediate transfer method, an image (pattern) of adjusted toner is formed on an intermediate transfer belt, and image density control and color misalignment correction control are performed by detecting the patch pattern on the intermediate transfer belt using a sensor. Furthermore, the image forming equipment may be configured such that the patch pattern passes through a secondary transfer section. In this case, the patch pattern that has already passed through the secondary transfer section must be removed from the intermediate transfer belt at a cleaning section.

[0006] Because the patch pattern is not transferred to the recording material, its toner concentration (toner dosage per unit area) is greater than the toner concentration of the residual toner from the transfer. Therefore, a relatively large number of brush rotations are required for the brush to properly remove the patch pattern from the intermediate transfer belt using an electrostatic brush cleaning method. When the number of brush rotations is insufficient when removing the patch pattern from the intermediate transfer belt, a cleaning defect may occur, resulting in the toner used for the patch pattern adhering to the subsequent printed image. However, by setting the number of brush rotations to be suitable for removing the patch pattern from the intermediate transfer belt, the number of times the brush and intermediate transfer belt rub against each other increases, which may shorten the lifespan of components including the intermediate transfer belt and brush. Summary of the Invention

[0007] Therefore, the object of the present invention is to achieve a longer lifespan for the intermediate transfer belt and the cleaning component while being able to properly remove the toner image from the intermediate transfer belt.

[0008] The above objective is achieved by the image forming apparatus according to the present invention. In short, the present invention provides the following solution:

[0009] (1) An image forming apparatus comprising: a rotatable image carrier member configured to carry a toner image; an exposure device configured to expose the image carrier member and form an electrostatic image on the image carrier member; a rotatable intermediate transfer belt for transferring the toner image from the image carrier member to the intermediate transfer belt, the intermediate transfer belt being configured to form a primary transfer portion and a secondary transfer portion, wherein the toner image is transferred from the image carrier member to the intermediate transfer belt in a primary transfer portion, and the toner image is... The toner image is transferred a second time from the intermediate transfer belt to the recording material at the secondary transfer section; a brush, whose rotational direction relative to the intermediate transfer belt is such that it contacts the intermediate transfer belt at a cleaning section downstream of the secondary transfer section and upstream of the primary transfer section, and is configured to remove toner from the intermediate transfer belt by electrostatic attraction while rotating; a drive section configured to drive the brush; and a controller configured to control the drive section, wherein the controller controls the execution of image forming operations and adjustment operations. In the image forming operation, toner formed on the intermediate transfer belt is transferred to the recording material. In the adjustment operation, an adjustment toner image is formed on the intermediate transfer belt. The drive unit is controlled such that when residual toner remaining on the intermediate transfer belt is removed by the brush, the brush rotates at a first circumferential speed Vr, and when the adjustment toner image is removed by the brush, the brush rotates at a second circumferential speed Vp, which is faster than the first circumferential speed Vr. In the case where the adjustment operation is performed during a continuous image forming operation involving multiple recording materials including a first recording material and a second recording material following the first recording material, after image forming is performed on the first recording material and before image forming is performed on the second recording material, the controller controls the drive unit to change the brush speed from the first circumferential speed Vr to the second circumferential speed Vp after the first recording material has passed through the secondary transfer unit and before the electrostatic image of the adjustment toner image begins to form.

[0010] (2) An image forming apparatus comprising: a rotatable image carrier member configured to carry a toner image; an exposure device configured to expose the image carrier member and form an electrostatic image on the image carrier member; and a rotatable intermediate transfer belt for transferring the toner image from the image carrier member to the intermediate transfer belt, the intermediate transfer belt being configured to form a primary transfer portion and a secondary transfer portion, the toner image being transferred from the image carrier member to the intermediate transfer belt at the primary transfer portion, and the toner image being transferred at the secondary transfer portion... The transfer portion is a secondary transfer from the intermediate transfer belt to the recording material; a brush, whose rotational direction relative to the intermediate transfer belt is such that it contacts the intermediate transfer belt at a cleaning portion downstream of the secondary transfer portion and upstream of the primary transfer portion, and is configured to remove toner from the intermediate transfer belt by electrostatic attraction while rotating; a drive portion configured to drive the brush; and a controller configured to control the drive portion, wherein the controller controls the execution of an image forming operation and an adjustment operation, in which the image forming operation is formed on the intermediate transfer belt. The toner on the intermediate transfer belt is transferred to the recording material. During the adjustment operation, an adjustment toner image is formed on the intermediate transfer belt. During the image formation operation, the drive section is controlled such that when residual toner remaining in the intermediate transfer belt is removed by the brush, the brush rotates at a first circumferential speed Vr, and when the adjustment toner image is removed by the brush from the intermediate transfer belt, the brush rotates at a second circumferential speed Vp, which is faster than the first circumferential speed Vr. This is further demonstrated when the toner image is removed by the brush onto a second recording material, which includes the first recording material and a subsequent second recording material. When the adjustment operation is performed during a continuous image forming operation involving multiple recording materials, including the first recording material, after image forming is performed on the first recording material and before image forming is performed on the second recording material, the controller controls the drive section to change the speed of the brush from the second circumferential speed Vp to the first circumferential speed Vr at a moment after the last part of the adjustment toner image formed in the adjustment operation along the movement direction of the surface of the intermediate transfer belt has reached the cleaning section and before the formation of an electrostatic image for the second recording material begins.

[0011] (3) An image forming apparatus comprising: a rotatable image carrier member configured to carry a toner image; an exposure device configured to expose the image carrier member and form an electrostatic image on the image carrier member; a rotatable intermediate transfer belt for transferring the toner image from the image carrier member to the intermediate transfer belt, the intermediate transfer belt being configured to form a primary transfer portion and a secondary transfer portion, the toner image being transferred from the image carrier member to the intermediate transfer belt at the primary transfer portion and the toner image being transferred a second time from the intermediate transfer belt to a recording material at the secondary transfer portion; a brush, the brush contacting the intermediate transfer belt at a cleaning portion downstream of the secondary transfer portion and upstream of the primary transfer portion relative to the rotation direction of the intermediate transfer belt, and configured to remove toner from the intermediate transfer belt by electrostatic attraction while rotating; a drive portion configured to drive the brush; and a controller. The controller is configured to control the drive section, wherein the controller controls to perform an image forming operation and an adjustment operation, in which toner formed on the intermediate transfer belt is transferred to recording material, and in the adjustment operation, an adjustment toner image is formed on the intermediate transfer belt, and controls the drive section such that when residual toner remaining on the intermediate transfer belt is removed by the brush from the intermediate transfer belt, the brush rotates at a first circumferential speed Vr, and when the adjustment toner image is removed by the brush from the intermediate transfer belt, the brush rotates at a second circumferential speed Vp, which is faster than the first circumferential speed Vr, and wherein, if the adjustment operation is performed using an image forming start signal before performing an image forming operation on the recording material of the first sheet of work, the controller controls the drive section to change the speed of the brush from the first circumferential speed Vr to the second circumferential speed Vp before the formation of an electrostatic image of the adjustment toner image begins.

[0012] (4) An image forming apparatus comprising: a rotatable image carrier member configured to carry a toner image; an exposure device configured to expose the image carrier member and form an electrostatic image on the image carrier member; a rotatable intermediate transfer belt for transferring the toner image from the image carrier member to the intermediate transfer belt, the intermediate transfer belt being configured to form a primary transfer portion and a secondary transfer portion, the toner image being transferred from the image carrier member to the intermediate transfer belt at the primary transfer portion and the toner image being transferred a second time from the intermediate transfer belt to a recording material at the secondary transfer portion; a brush, the brush contacting the intermediate transfer belt at a cleaning portion downstream of the secondary transfer portion and upstream of the primary transfer portion relative to the rotation direction of the intermediate transfer belt, and configured to remove toner from the intermediate transfer belt by electrostatic attraction while rotating; a drive portion configured to drive the brush; and a controller configured to... To control the drive section, the controller controls the execution of an image forming operation and an adjustment operation, in which toner formed on the intermediate transfer belt is transferred to recording material, and in the adjustment operation, an adjustment toner image is formed on the intermediate transfer belt. The controller also controls the drive section such that when residual toner remaining on the intermediate transfer belt is removed by the brush, the brush rotates at a first circumferential speed Vr, and when the adjustment toner image is removed by the brush, the brush rotates at a second circumferential speed Vp, which is faster than the first circumferential speed Vr. Furthermore, if the adjustment operation is performed using an image forming start signal before the image forming operation is performed on the recording material of the first sheet to be worked, the controller controls the drive section to change the speed of the brush from the second circumferential speed Vp to the first circumferential speed Vr after the adjustment operation is performed and before the formation of an electrostatic image of the recording material of the first sheet to be worked begins.

[0013] Other features of the invention will become clear from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0014] Figure 1 It is a cross-sectional schematic view of the image forming device.

[0015] Figure 2 Parts (a) and (b) include schematic diagrams of the patch pattern.

[0016] Figure 3 This is a schematic block diagram showing the control configuration of an image forming apparatus.

[0017] Figure 4 This is a schematic cross-sectional view of the secondary transfer portion during image formation.

[0018] Figure 5 This is a schematic cross-sectional view of the first mode of the secondary transfer section during the image correction operation.

[0019] Figure 6 This is a schematic cross-sectional view of the second mode of the secondary transfer section during the image correction operation.

[0020] Figure 7 It is a schematic cross-sectional view with a cleaning device during image formation.

[0021] Figure 8 This is a schematic cross-sectional view of the cleaning device during an image correction operation.

[0022] Figure 9 This is a flowchart describing the control of the cleaning drive section that accompanies the image correction operation prior to the image formation operation.

[0023] Figure 10 This is a flowchart describing the control of the cleaning drive section that accompanies an image correction operation performed midway through continuous printing. Detailed Implementation

[0024] The image forming apparatus according to the invention will be described in more detail below with reference to the accompanying drawings.

[0025] [Example 1]

[0026] <Image forming equipment>

[0027] Figure 1 This is a schematic cross-sectional view of the image forming apparatus 100 in this embodiment. The image forming apparatus 100 in this embodiment is a tandem printer of the intermediate transfer type, which is capable of forming panchromatic images using an electrophotographic method. The image forming apparatus 100 can form panchromatic images on a recording material S having a sheet shape based on image signals sent from an external device such as a host computer.

[0028] Image forming apparatus 100 includes four image forming sections (stations) 1Y, 1M, 1C, and 1K as multiple image forming sections, which respectively form toner images of yellow (Y), magenta (M), cyan (C), and black (K). The four image forming sections 1Y, 1M, 1C, and 1K are arranged in a row along the image transfer surface of an intermediate transfer belt 31 that extends approximately horizontally. For elements having the same or corresponding function or configuration for each color setting, the numerals indicating that the element is used for one of the colors Y, M, C, and K can be omitted from the description. The image forming unit 1 (1Y, 1M, 1C, 1K) is configured to include a photosensitive drum 11 (11Y, 11M, 11C, 11K), a charger 12 (12Y, 12M, 12C, 12K), an exposure unit 13 (13Y, 13M, 13C, 13K), a developing unit 14 (14Y, 14M, 14C, 14K), a drum cleaning unit 15 (15Y, 15M, 15C, 15K), etc.

[0029] The photosensitive drum 11 is a rotatable photosensitive component (electrophotographic photosensitive component) that serves as an image-carrying component. It has a drum-shaped (cylindrical) shape. Figure 1 The photosensitive drum 11 is driven to rotate in the direction of arrow R1 (counterclockwise). This is achieved by the drum drive section 131, which serves as a drive mechanism for the photosensitive components. Figure 3 The rotating photosensitive drum 11 is driven by the driving force transmitted by the drum drive motor 131a. The surface of the rotating photosensitive drum 11 is uniformly charged to a predetermined potential of predetermined polarity (negative polarity in this embodiment) by the charger 12, which serves as a charging device. During charging, the charging power supply (high-voltage power supply) 121, which is the charging voltage application part, is used to drive the drum. Figure 3 A charging bias voltage (charging voltage) is applied to the charger 12. The surface of the charged photosensitive drum 11 is scanned and exposed by the exposure device 13, which is an exposure apparatus, by irradiating it with a laser according to an image signal (image information), and an electrostatic latent image (electrostatic image) corresponding to the image signal is formed on the surface of the photosensitive drum 11. In this embodiment, the exposure device 13 is configured to include a laser scanner. Incidentally, the exposure device 13 can be configured as a single unit for exposing the photosensitive drums 11 in multiple image forming sections 1. Furthermore, the exposure device 13 is not limited to being configured to include a laser scanner using a laser light source, but can be configured to include an LED array, etc., using LEDs as a light source.

[0030] The electrostatic latent image formed on the photosensitive drum 11 is developed (visualized) by toner supplied by the developing apparatus 14, which is a developing unit, and a toner image (developer image) is formed on the photosensitive drum 11. In this embodiment, the developing apparatus 14 uses a two-component developer as the developer, which is provided with toner (non-magnetic toner particles) and a carrier (magnetic carrier particles). The developing apparatus 14 includes a developing sleeve as a developer carrying member (developing member), on which the developer is carried to transfer the developer to the opposite part between the developing sleeve and the photosensitive drum 11, and toner is supplied to the photosensitive drum 11. During development, the developing power supply (high voltage power supply) 122 (which is a developing voltage application part) is used to develop the latent image. Figure 3 A developing bias voltage (developing voltage) is applied to the developing sleeve. In this embodiment, the developing apparatus 14 causes the absolute value of the potential of the toner, which is charged to the same polarity as the photosensitive drum 11 (negative polarity in this embodiment), to be adsorbed onto the photosensitive drum 11, to be reduced by exposure after being uniformly charged (reverse developing mode). In this embodiment, the normal polarity of the toner (which is the main polarity of the toner during developing) is negative.

[0031] Opposite to the four photosensitive drums 11Y, 11M, 11C, and 11K, an intermediate transfer belt 31, consisting of an annular belt, is provided as an intermediate transfer member. The intermediate transfer belt 31 is hooked onto a drive roller 33, a tension roller 34, a secondary transfer front roller 36, and a secondary transfer inner roller 32, which are multiple tension rollers, and is stretched by a predetermined tension. On the inner circumferential surface side of the intermediate transfer belt 31, at positions opposite to the photosensitive drums 11Y, 11M, 11C, and 11K across the intermediate transfer belt 31, primary transfer rollers 35Y, 35M, 35C, and 35K, which are primary transfer members with a roller shape, are provided as primary transfer devices. The primary transfer roller 35 is pressed towards the photosensitive drum 11, forming a primary transfer portion (primary transfer clamping portion) N1 (N1Y, N1M, N1C, N1K), which is the contact portion (contact position) between the photosensitive drum 11 and the intermediate transfer belt 31. The intermediate transfer belt 31 is driven to rotate by the drive roller 33. Figure 1 The drive roller 33 rotates (circularly moves) in the direction of arrow R2 (clockwise). The drive roller 33 is driven by the belt drive section 132, which serves as a drive device for the intermediate transfer component. Figure 3The drive force transmitted from the drive motor 132a is used to rotate the belt. The tension roller 34 applies a predetermined tension to the intermediate transfer belt 31. The secondary transfer front roller 36 forms the surface of the intermediate transfer belt 31 that enters the secondary transfer section N2, which will be described below. The secondary transfer inner roller 32, together with the secondary transfer outer roller 41, which will be described below, forms the secondary transfer section N2. The tension rollers, except for the drive roller 33, and the corresponding primary transfer rollers 35 are rotated by the rotation of the intermediate transfer belt 31.

[0032] Incidentally, in this embodiment, the intermediate transfer belt 31 is composed of a belt having a three-layer structure comprising a base layer, an elastic layer, and a surface layer sequentially from the inner peripheral surface (back side) to the outer peripheral surface (front side). As the material constituting the base layer, materials in which an appropriate amount of carbon black, acting as an antistatic agent, is contained in resins such as polyimide (PI) and polycarbonate (PC), or various types of rubber, are suitable. As the elastic material constituting the elastic layer, materials in which an appropriate amount of ionic conductive agent is contained in various types of rubber, such as polyurethane rubber and silicone rubber, are suitable. As the material constituting the surface layer, resins such as fluoropolymers are suitable. In this embodiment, a belt with an elastic layer is used as the intermediate transfer belt 31; however, for example, a single-layer PI belt without an elastic layer or a PI-coated belt with a fluoropolymer or the like coated on a PI base layer may also be used.

[0033] In the primary transfer section N1, the toner image formed on the photosensitive drum 11 is transferred (primary transfer) onto the rotating intermediate transfer belt 31 by the action of the primary transfer roller 35. During the primary transfer, the primary transfer power supply (high voltage power supply) 123 (which serves as the primary transfer voltage application section)... Figure 3 A primary transfer bias voltage (primary transfer voltage) is applied to the primary transfer roller 35. This primary transfer bias voltage is a DC voltage with a polarity opposite to the normal charge polarity of the toner (positive polarity in this embodiment). For example, during the formation of a panchromatic image, toner images of corresponding colors—yellow, magenta, cyan, and black—formed on the respective photosensitive drums 11 are transferred to be superimposed on the same image forming area on the intermediate transfer belt 31. Toner that is not transferred to the intermediate transfer belt 31 and remains on the photosensitive drum 11 (primary transfer residual toner) is removed from the photosensitive drum 11 and collected by the drum cleaning device 15, which serves as a photosensitive component cleaning device.

[0034] On the outer peripheral surface side of the intermediate transfer belt 31, at a position opposite to the secondary transfer inner roller 32 across the intermediate transfer belt 31, a secondary transfer outer roller 41 is provided. The secondary transfer outer roller 41 is pressed toward the secondary transfer inner roller 32, forming a secondary transfer portion (secondary transfer clamping portion) N2, which is the contact portion between the intermediate transfer belt 31 and the secondary transfer outer roller 41. In the secondary transfer portion N2, the toner image formed on the intermediate transfer belt 31 is transferred (secondary transfer) onto the recording material S held and conveyed by the intermediate transfer belt 31 and the secondary transfer outer roller 41. During the secondary transfer, a secondary transfer power supply (high voltage power supply) 124 (which is the secondary transfer voltage application portion) is used. Figure 3 , Figure 4 A secondary transfer bias voltage (secondary transfer voltage) is applied to the secondary transfer inner roller 32. This secondary transfer bias voltage is a DC voltage with the same polarity as the normal charge polarity of the toner (negative polarity in this embodiment).

[0035] Recording materials S, such as paper and plastic sheets, are contained in cartridges 61, 62, and 63, which serve as recording material receiving sections. The recording material S is conveyed to a feed transport path 67 by the rotation of any one of the feed rollers 64, 65, and 66, which serve as feed members. The recording material S is then conveyed to the secondary transfer section N2 synchronously with the toner image on the intermediate transfer belt 31 by the registration roller 21, which serves as a transport member.

[0036] The toner that was not transferred to the recording material S and remained on the intermediate transfer belt 31 (secondary transfer residual toner) was removed from the intermediate transfer belt 31 and collected by the belt cleaning device 80, which is an intermediate transfer component cleaning device. The details of the belt cleaning device 80 will be described below.

[0037] Recording material S, with the toner image already transferred, is conveyed via conveyor belt 71 to fixing device 5, which is a fixing unit. Fixing device 5 fixes (melts, adheres) the toner image onto the surface of recording material S by heating and pressing the recording material S carrying the unfixed toner image. Recording material S with the fixed image is discharged (output) via discharge conveyor path 68 to tray 69, which is the discharge section.

[0038] Incidentally, in this embodiment, the image forming apparatus 100 is configured such that the recording material S supplied to the secondary transfer section N2... Figure 1 The material is transferred from right to left, but it is not limited to this; it can be configured to transfer the recording material S from left to right.

[0039] The image forming apparatus 100 includes a sensor unit 90, which serves as a toner image detection device, for detecting an adjusted toner image (patchy pattern) carried on and conveyed on an intermediate transfer belt 31. The sensor unit 90 is positioned downstream of the primary transfer section N1 (the most downstream primary transfer section N1K) and upstream of the secondary transfer section N2 in the rotational direction of the intermediate transfer belt 31, thereby enabling the detection of the toner image on the intermediate transfer belt 31. In this embodiment, the sensor unit 90 is positioned opposite the tension roller 34 across the intermediate transfer belt 31. The sensor unit 90 can be configured to detect the toner image at multiple locations in the width direction, substantially perpendicular to the surface of the intermediate transfer belt 31 in the direction of movement (conveyance direction). The sensor unit 90 is configured to include a reflective optical sensor.

[0040] In this embodiment, a density patch pattern for image density control and a registration patch pattern for color misalignment (registration) correction control are formed on the intermediate transfer belt 31 as patch patterns. In other words, in this embodiment, the image forming apparatus 100 performs image density control (density correction control) and color misalignment correction control as an image correction operation (adjustment operation) of forming patch patterns on the intermediate transfer belt 31. Figure 2 Parts (a) and (b) are schematic diagrams illustrating examples of concentration patch pattern 201 and registration patch pattern 202, respectively. Figure 2 As shown in part (a), in an image density control, as density patch patterns 201, multiple patch patterns with different densities are formed along the moving direction of the surface of the intermediate transfer belt 31 for each color—yellow, magenta, cyan, and black. Additionally, as... Figure 2 As shown in section (b), in a single color misalignment correction control, registration patch patterns of yellow, magenta, cyan, and black are formed along the moving direction of the surface of the intermediate transfer belt 31 as registration patch patterns 202. The registration patch patterns 202 are formed, for example, on the two end portions of the intermediate transfer belt 31 in the width direction. The patch patterns are formed on the intermediate transfer belt 31 in the same manner as the printed image transferred to the recording material S and output as a product, by forming on the photosensitive drum 11 and transferring it onto the intermediate transfer belt 31.

[0041] For example, the image forming apparatus 100 interrupts the image forming operation each time it forms a printed image on one hundred sheets of recording material S with an A4 size, and performs the formation of a density patch pattern and reads it using the sensor unit 90. Then, the image forming apparatus 100 resumes the image forming operation after performing image density control using the result. Alternatively, the image forming apparatus 100 interrupts the image forming operation, for example, when the temperature rise (ΔT) of the exposure apparatus 13 becomes ΔT>3°C, and performs the formation of a registration patch pattern and reads it using the sensor unit 90. Then, the image forming apparatus 100 resumes the image forming operation after performing color misalignment correction control using the result.

[0042] In this embodiment, the patch pattern carried on the intermediate transfer belt 31 is not removed from the intermediate transfer belt 31 at the secondary transfer section N2, but passes through the secondary transfer section N2 and is removed from the intermediate transfer belt 31 by the belt cleaning device 80. In this embodiment, the image forming apparatus 100 does not include a cleaning configuration in which the patch pattern is transferred to a component (such as a roller or belt) that contacts the outer peripheral surface of the intermediate transfer belt 31 to form the secondary transfer section N2, removed from the component, and collected.

[0043] Incidentally, in this embodiment, the image forming apparatus 100 is a color image forming apparatus capable of forming panchromatic images, but the present invention is not limited thereto. The image forming apparatus may, for example, include only an image forming portion for black as an image forming portion and be capable of forming black and white images. In this case, since color misalignment does not occur, the operation associated with color misalignment correction control becomes unnecessary.

[0044] <Control Configuration>

[0045] Figure 3This is a schematic block diagram illustrating the control configuration of the image forming apparatus 100 in this embodiment. The image forming apparatus 100 includes a control section (control circuit) 110 that controls the image forming apparatus 100. The control section 110 is configured to include a CPU 111 as an arithmetic processing means (arithmetic processing section), a memory (storage medium) 112 (such as ROM, RAM, and non-volatile memory) as a storage means (storage section), and an input / output section (not shown) for performing input / output of signals (information) between the control section 110 and external devices. The CPU 111 and the memory 112 can transfer and read data from each other. The ROM stores control programs, pre-obtained data tables, etc. The RAM (which is a rewritable memory) stores information input to the control section 110, detected information, calculation results, etc. The non-volatile memory stores various types of setting information, various types of historical information, etc. Each part of the image forming apparatus 100 is connected to the control section 110. The control unit 110 is capable of controlling the operation of each part of the image forming apparatus 100 so that the image forming apparatus 100 performs various types of operations, such as image forming operations, image density control, and color misalignment correction control.

[0046] For example, various types of power supplies (including charging power supply 121, developing power supply 122, primary transfer power supply 123, secondary transfer power supply 124, first cleaning power supply 125, second cleaning power supply 126 (described below), etc.) are connected to the control section 110. Additionally, various types of drive sections (including drum drive section 131, belt drive section 132, cleaning drive section 133 (described below), etc.) are connected to the control section 110. Furthermore, exposure devices 13 (13Y, 13M, 13C, 13K), sensor units 90, etc., are connected to the control section 110. Additionally, image reading devices (not shown) installed in or connected to the image forming apparatus 100 and / or external devices such as host computers can be connected to the control section 110.

[0047] Incidentally, their illustrations are omitted, but in this embodiment, the charging power supply 121, developing power supply 122, and primary transfer power supply 123 are each independently configured relative to each image forming section 1. Furthermore, the drum drive section 131, belt drive section 132, and cleaning drive section 133 are each configured to include a drive motor as a drive source, gears as drive transmission components, etc. The drum drive section 131 (or its drive motor) may be independently configured relative to each photosensitive drum 11, or may be shared for all or a portion of the photosensitive drums 11. Additionally, for example, among various types of drive sections (such as the drum drive section 131 and belt drive section 132), at least a portion of the configuration (drive motor, etc.) may be shared.

[0048] Image forming apparatus 100 performs a printing job, which is initiated by a start command and consists of a series of operations to form and output an image on one or more recording materials S. A printing job typically includes an image forming process (image forming operation), a pre-rotation process (pre-rotation operation), a sheet spacing process (sheet spacing operation), and a post-rotation process (post-rotation operation). The image forming process is the time period during which the formation of an electrostatic latent image (exposure), the formation of a toner image (development), the primary transfer of the toner image, and the secondary transfer are performed on the image forming area (where the printed image is to be formed) on the photosensitive drum 11 and the intermediate transfer belt 31, and the term "during image forming" refers to this time period. More specifically, the moment "during image forming" varies at the location where the formation of the electrostatic latent image, the formation of the toner image, and the primary and secondary transfers of the toner image are performed. The pre-rotation process is the time period from the input of the start command until the formation of the printed image (the start of exposure) begins, during which preparatory operations prior to the image forming process are performed. The sheet spacing process is a time period corresponding to the interval between recording materials S when image formation (continuous printing, continuous image formation) is performed on multiple recording materials S consecutively. The post-rotation process is a time period in which a preparation operation (or setup operation) is performed after the image formation process. The term "non-image formation period" refers to a time period other than "image formation period," and includes the aforementioned pre-rotation process, sheet spacing process, and post-rotation process, as well as the pre-rotation multi-rotation process (pre-rotation operation), which is a preparation operation when the image forming apparatus 100 is turned on or returns from a sleep state.

[0049] <Secondary Transfer Section>

[0050] Figure 4 This is a schematic cross-sectional view of the secondary transfer portion N2 during image formation (when a printed image is formed on the intermediate transfer belt 31), showing a section that is approximately perpendicular to the axis of rotation of the secondary transfer inner roller 32.

[0051] The surface (pre-stretching surface) L of the intermediate transfer belt 31, formed by stretching through the secondary transfer inner roller 32 and the secondary transfer front roller 36, contacts the secondary transfer outer roller 41. The secondary transfer outer roller 41 is pressed toward the secondary transfer inner roller 32 by a pressing spring 42, which acts as a pressing member. As a result, the secondary transfer portion N2 is formed.

[0052] During image formation (during the secondary transfer of the printed image), a secondary transfer bias voltage (secondary transfer voltage) having the same polarity as the toner polarity (normal polarity of the toner) constituting the toner image on the intermediate transfer belt 31 is applied to the secondary transfer inner roller 32 via the secondary transfer power supply 124. The secondary transfer outer roller 41 is grounded (electrically grounded). As a result, a transfer electric field is formed in the secondary transfer section N2. In this embodiment, since the toner constituting the toner image on the intermediate transfer belt 31 has a negative polarity (-) charge, a negative polarity (-) voltage is applied to the secondary transfer inner roller 32. On the upstream side of the secondary transfer section N2 along the conveying direction of the recording material S, a secondary transfer pre-guide 43 is provided as a recording material guiding member, which guides the recording material S toward the secondary transfer section N2. The secondary transfer pre-guide 43 is configured to include an upper guide 43a and a lower guide 43b. The upper guide 43a restricts the movement of the recording material S in the direction approaching the intermediate transfer belt 31. The lower guide 43b restricts the movement of the recording material S in the direction away from the intermediate transfer belt 31. Furthermore, in the secondary transfer section N2, the toner image Ti constituting the printed image is transferred (secondary transfer) from the intermediate transfer belt 31 to the recording material S guided and conveyed to the secondary transfer section N2 by the secondary transfer guide 43. In this embodiment, the secondary transfer device 44, which serves as a secondary transfer unit, is constructed by the secondary transfer inner roller 32 as a secondary transfer member and the secondary transfer outer roller 41 as a secondary transfer opposing member. Incidentally, a secondary transfer bias voltage with a polarity opposite to the normal polarity of the toner can be applied to the secondary transfer outer roller 41 as a secondary transfer member, and the secondary transfer inner roller 32 as a secondary transfer opposing member is grounded (electrically grounded).

[0053] On the intermediate transfer belt 31, residual toner (secondary transfer residual toner) Tr is generated that was not transferred to the recording material S in the secondary transfer section N2 and remains on the intermediate transfer belt 31. This residual toner Tr is conveyed to the downstream side of the secondary transfer section N2 in the direction of movement of the intermediate transfer belt 31 while being carried on the intermediate transfer belt 31.

[0054] In the image forming apparatus 100 of this embodiment, the rate (secondary transfer efficiency) of transferring a monochrome solid color (maximum concentration) toner image from the intermediate transfer belt 31 to the recording material S in the secondary transfer section N2 is approximately 97%. In other words, in the image forming apparatus 100 of this embodiment, approximately 3% of the toner in the monochrome solid color toner image remains on the intermediate transfer belt 31 as transfer residual toner Tr.

[0055] Figure 5This is a schematic cross-sectional view of the first mode of the secondary transfer section N2 during the image correction operation (when a patch pattern is formed on the intermediate transfer belt 31), showing a section that is generally perpendicular to the rotation axis of the secondary transfer inner roller 32.

[0056] When the patch pattern Tp is formed on the intermediate transfer belt 31, the recording material S is not transferred to the secondary transfer section N2, and the secondary transfer outer roller 41 is separated from the intermediate transfer belt 31. Therefore, it becomes possible for the patch pattern Tp to pass through the secondary transfer section N2 while still being carried on the intermediate transfer belt 31. As a result, toner adhesion to the secondary transfer outer roller 41 is suppressed, and contaminants caused by toner adhesion to the back side of the recording material S during subsequent image formation is also suppressed.

[0057] In an image correction operation where multiple patch patterns are formed on the intermediate transfer belt 31, the secondary transfer outer roller 41 typically separates from the intermediate transfer belt 31 from a predetermined time before the foremost part (front end of the first patch pattern) of the multiple patch patterns reaches the position corresponding to the secondary transfer portion N2 in the moving direction of the multiple patch patterns in the moving direction of the intermediate transfer belt 31, until a predetermined time after the last part (rear end of the last patch pattern) of the multiple patch patterns passes the position corresponding to the secondary transfer portion N2.

[0058] In this first mode, a contact and separation mechanism 140, which acts as a moving device to bring the secondary transfer outer roller 41 into contact with and separate from the intermediate transfer belt 31, is provided on the image forming apparatus 100.

[0059] Figure 6 This is a schematic cross-sectional view of the second mode of the secondary transfer section N2 during the image correction operation (when a patch pattern is formed on the intermediate transfer belt 31), showing a section that is generally perpendicular to the rotation axis of the secondary transfer inner roller 32.

[0060] When the patch pattern Tp is formed on the intermediate transfer belt 31, the recording material S is not transferred to the secondary transfer section N2, and a positive (+) voltage (a voltage with a polarity opposite to the normal charge polarity of the toner) is applied to the secondary transfer inner roller 32 by the secondary transfer power supply 124. Therefore, the patch pattern Tp with a negative (-) charge can pass through the secondary transfer section N2 while remaining carried on the intermediate transfer belt 31. This suppresses toner adhesion to the secondary transfer outer roller 41 and prevents contaminants caused by the toner from adhering to the back side of the recording material S during subsequent image formation.

[0061] In an image correction operation where multiple patch patterns are formed on the intermediate transfer belt 31, a positive voltage is typically applied to the secondary transfer inner roller 32 from a predetermined time before the foremost part (front end of the first patch pattern) of the multiple patch patterns reaches the secondary transfer section N2 in the moving direction of the intermediate transfer belt 31 until a predetermined time after the last part (rear end of the last patch pattern) of the multiple patch patterns passes through the secondary transfer section N2 in the moving direction of the intermediate transfer belt 31.

[0062] In this second mode, the secondary transfer power supply 124 is configured to apply both a negative voltage and a positive voltage to the secondary transfer inner roller 32.

[0063] In this embodiment, either the first mode or the second mode described above can be used.

[0064] <Configuration of cleaning equipment and cleaning operations during image formation>

[0065] Next, the cleaning device (hereinafter also referred to as "cleaning device") 80 in this embodiment will be described.

[0066] Figure 7 This is a schematic cross-sectional view of the cleaning device 80 during image formation in this embodiment (when a printed image is formed on the intermediate transfer belt 31), showing a section that is approximately perpendicular to the rotation axis of the secondary transfer inner roller 32.

[0067] The cleaning device 80 is disposed downstream of the secondary transfer section N2 and upstream of the primary transfer section N1 (the upstreammost primary transfer section N1Y) in the rotational direction of the intermediate transfer belt 31. In this embodiment, the cleaning device 80 is disposed at a position opposite to the drive roller 33, separated by the intermediate transfer belt 31. In this embodiment, the cleaning device 80 employs an electrostatic cleaning method, particularly an electrostatic brush cleaning method, in which the toner on the intermediate transfer belt 31 is electrostatically collected.

[0068] The cleaning device 80 includes a housing 88 disposed near the intermediate transfer belt 31. The housing 88 contains the following components: First, a first brush (cleaning brush) 81 and a second brush (cleaning brush) 82, serving as a first cleaning member and a second cleaning member. Furthermore, a first bias roller 83 and a second bias roller 84, serving as a first collection member and a second collection member (voltage application member). Additionally, a first scraper 85 and a second scraper 86, serving as a first scraping member and a second scraping member. Finally, a toner collecting screw 87, serving as a toner delivery member, is provided.

[0069] The first brush 81 and the second brush 82 are each composed of a conductive brush roller, which is a rotatable conductive cleaning component with a brush shape. The brush fibers of the first brush 81 and the second brush 82 are composed of carbon-dispersed nylon fibers, acrylic fibers, or polyester fibers, for example, with a yarn resistance value of 3 × 10⁻⁶. 5 Up to 1×10 13 The fiber thickness is 2 to 15 denier. The first brush 81 and the second brush 82 are constructed by embedding brush fibers (conductive fibers) onto a metal roller serving as a substrate (core metal, core material) at a bristle density ratio of 50,000 to 500,000 fibers / square inch. The length of the brush fibers is configured, for example, to be about 3 to 5 mm. The first brush 81 and the second brush 82 are configured to contact the intermediate transfer belt 31. In this embodiment, the first brush 81 and the second brush 82 are configured to maintain an entry amount of about 1.0 to 2.0 mm relative to the intermediate transfer belt 31. Incidentally, this entry amount is represented by a value obtained by subtracting the shortest distance between the brush substrate and the intermediate transfer belt 31 from the length of the brush fiber. Furthermore, the first brush 81 and the second brush 82 are driven by a cleaning motor 133a (which is a cleaning drive unit 133). Figure 3 The driving force transmitted in Figure 7 The first brush 81 and the second brush 82 are rotated in the direction of arrow R3 (clockwise). In other words, the first brush 81 and the second brush 82 are rotated so that they move in the opposite direction to the direction of movement of the intermediate transfer belt 31, that is, they move at the contact portion (contact position) with the intermediate transfer belt 31 in a direction opposite to the direction of movement of the intermediate transfer belt 31. As a result, the first brush 81 and the second brush 82 rub against the surface of the intermediate transfer belt 31.

[0070] In this embodiment, the first brush 81 and the second brush 82 contact the drive roller 33, which serves as a counter component, via the intermediate transfer belt 31. The drive roller 33 is grounded (electrically grounded). The rotation axis directions of the first brush 81 and the second brush 82 are substantially parallel to the width direction of the intermediate transfer belt 31 (the rotation axis direction of the secondary transfer inner roller 32). The length of the first brush 81 and the second brush 82 in their rotation axis direction is longer than the width of the area on the intermediate transfer belt 6 where the toner image is to be formed in the width direction of the intermediate transfer belt 31. The contact portion between the first brush 81 and the intermediate transfer belt 31 is a first cleaning portion CL1 that removes toner from the intermediate transfer belt 31 by the first brush 81. Similarly, the contact portion between the second brush 82 and the intermediate transfer belt 31 is a second cleaning portion CL2 that removes toner from the intermediate transfer belt 31 by the second brush 82. The first cleaning portion CL1 and the second cleaning portion CL2 are located downstream of the secondary transfer portion N2 and upstream of the primary transfer portion N1 (the upstreammost primary transfer portion N1Y) in the rotation direction of the intermediate transfer belt 31. Furthermore, in this embodiment, in the movement direction of the surface of the intermediate transfer belt 31, the first cleaning portion CL1 is located upstream of the second cleaning portion CL2, and the second cleaning portion CL2 is located downstream of the first cleaning portion CL1. In other words, in this embodiment, in the movement direction of the surface of the intermediate transfer belt 31, the first brush 81 is located upstream of the second brush 82, and the second brush 82 is located downstream of the first brush 81.

[0071] The first bias roller 83 and the second bias roller 84 are rotatable rollers (metal rollers) made of metal (e.g., aluminum). The first bias roller 83 and the second bias roller 84 are respectively configured to contact the first brush 81 and the second brush 82. In this embodiment, the first bias roller 83 and the second bias roller 84 are respectively configured to maintain an entry amount of approximately 1.5 to 2.5 mm relative to the first brush 81 and the second brush 82. Furthermore, the first bias roller 83 and the second bias roller 84 are driven by a cleaning motor 133a (which is a cleaning drive section 133, serving as a drive device). Figure 3 The driving force transmitted in Figure 7The first bias roller 83 and the second bias roller 84 are rotated in the direction of arrow R4 (counterclockwise). In other words, the first bias roller 83 and the second bias roller 84 are rotated to move in the same direction as the rotation of the first brush 81 and the second brush 82, that is, at the contact portion with the first brush 81 and the second brush 82, they move in the same forward direction as the moving direction of the first brush 81 and the second brush 82. The rotation axis direction of the first bias roller 83 and the second bias roller 84 is approximately parallel to the width direction of the intermediate transfer belt 6 (the rotation axis direction of the secondary transfer inner roller 32). The length of the first bias roller 83 and the second bias roller 84 in the direction of their rotation axis is approximately the same as the length of the first brush 81 and the second brush 82 in the direction of their rotation axis.

[0072] The first scraper 85 and the second scraper 86 are respectively configured to contact the first biasing roller 83 and the second biasing roller 84. The first scraper 85 and the second scraper 86 are formed of a rubber material (e.g., polyurethane rubber) as an elastic member. The first scraper 85 and the second scraper 86 are plate-shaped members having a predetermined length and a predetermined thickness in both the longitudinal and short-side directions. The longitudinal direction is arranged substantially parallel to the rotation axis of the first biasing roller 83 and the second biasing roller 84, and the short-side direction is substantially perpendicular to the longitudinal direction. The first scraper 85 and the second scraper 86 contact the first biasing roller 83 and the second biasing roller 84 in directions opposite to their rotation directions (corresponding directions in which their free ends face the upstream side of the rotation direction). The lengths of the first scraper 85 and the second scraper 86 in their longitudinal direction are substantially the same as the lengths of the first biasing roller 83 and the second biasing roller 84 in their rotation axis direction.

[0073] In this embodiment, a first cleaning bias voltage (first cleaning voltage) with negative polarity (-) is applied to the first brush 81 positioned upstream of the surface of the intermediate transfer belt 31 in the moving direction. This negative polarity (-) is the same as the normal polarity of the toner. In this embodiment, a DC voltage with negative polarity (-) is applied to the first bias roller 83 via the first cleaning power supply (high voltage power supply) 125. As a result, a DC voltage with negative polarity (-) is applied to the first brush 81 via the first bias roller 83. On the other hand, in this embodiment, a second cleaning bias voltage (second cleaning voltage) with positive polarity (+) is applied to the second brush 82 positioned downstream of the surface of the intermediate transfer belt 31 in the moving direction. This positive polarity (+) is the opposite to the normal polarity of the toner. In this embodiment, a DC voltage with positive polarity (+) is applied to the second bias roller 84 via the second cleaning power supply (high voltage power supply) 126. As a result, a positive (+) DC voltage is applied to the second brush 82 via the second bias roller 84.

[0074] Most of the residual toner Tr that has passed through the secondary transfer section N2 is charged to a positive polarity (+). This is because most of the residual toner Tr is a positively polarized (+) toner that remains on the intermediate transfer belt 31 without being transferred to the recording material S by the positively polarized (+) secondary transfer bias. As the intermediate transfer belt 31 rotates, the residual toner Tr is electrostatically attracted to the first brush 81, which is subjected to a negatively polarized (-) first cleaning bias, and is removed from the intermediate transfer belt 31. For example, when a voltage of -3.5 kV is applied to the first bias roller 83, the potential of the first brush 81 becomes -2.0 kV, and the positively polarized (+) residual toner Tr on the intermediate transfer belt 31 is transferred from the intermediate transfer belt 31 to the first brush 81. Due to the potential difference between the first brush 81 and the first bias roller 83, the toner transferred to the first brush 81 is transferred to the first bias roller 83. The toner transferred to the first bias roller 83 is then scraped off by the first scraper 85.

[0075] As described above, the residual toner Tr on the intermediate transfer belt 31 is removed from the intermediate transfer belt 31 by the first brush 81. However, there is a possibility that the residual toner Tr may remain on the intermediate transfer belt 31 after passing through the first cleaning section CL1. The residual toner Tr that has passed through the first cleaning section CL1 is charged to the negative polarity (-) by a first cleaning bias voltage applied to the first brush 81. This is believed to be because the toner becomes charged through charge injection or discharge.

[0076] The residual toner Tr that has passed through the first cleaning section CL1 is electrostatically attracted to the second brush 82, which is subjected to a second cleaning bias voltage with a positive polarity (+), as the intermediate transfer belt 31 rotates, and is removed from the intermediate transfer belt 31. Thus, residual toner Tr that could not be removed from the intermediate transfer belt 31 by the first brush 81 can be removed by the second brush 82. For example, when a voltage of +3.5kV is applied to the second bias roller 84, the potential of the second brush 82 becomes +2.0kV, and the residual toner Tr with a negative polarity (-) on the intermediate transfer belt 31 is transferred from the intermediate transfer belt 31 to the second brush 82. Due to the potential difference between the second brush 82 and the second bias roller 84, the toner transferred to the second brush 82 is transferred from the second brush 82 to the second bias roller 84. The toner transferred to the second bias roller 84 is scraped off by the second scraper 86.

[0077] Incidentally, the first and second cleaning bias voltages can be placed under constant voltage control or constant current control. It is sufficient to supply enough cleaning current (e.g., a current with an absolute value of 10 μA to 80 μA) to the first cleaning section CL1 and the second cleaning section CL2. Here, constant current control is a control in which the output of the power supply is adjusted such that the current supplied to the target becomes approximately constant at the target current. Similarly, constant voltage control is a control in which the output of the power supply is adjusted such that the voltage applied to the target becomes approximately constant at the target voltage.

[0078] The toner scraped off from the first bias roller 83 and the second bias roller 84 by the first scraper 85 and the second scraper 86 is contained in the housing 88. The toner contained in the housing 88 is conveyed by a toner collecting screw 87 provided in the housing 88 and discharged from the housing 88. The toner collecting screw 87 is driven by a cleaning motor 133a (which is a cleaning drive section 133) which serves as a drive unit. Figure 3 The toner discharged from the housing 88 is driven to rotate by the driving force transmitted from it. The toner discharged from the housing 88 is conveyed via a conveying path (not shown) provided in the image forming apparatus 100 to a toner collection container (not shown) provided in the image forming apparatus 100, and is collected in the toner collection container.

[0079] In this embodiment, the first brush 81, the second brush 82, the first bias roller 83, the second bias roller 84, and the toner collecting screw 87 are driven and connected via a gear system. These are all driven by a common cleaning motor 133a of the cleaning drive section 133. Figure 3 Driven by the first brush 81. Here, the circumferential speed of the first brush 81 is defined as V1, and the circumferential speed of the second brush 82 is defined as V2. Incidentally, the circumferential speeds of the first brush 81 and the second brush 82 are respectively represented by the moving speeds of the first brush 81 and the second brush 82 at the contact portions with the intermediate transfer belt 31 (at the surface position on the intermediate transfer belt where the distance between the brush substrate and the intermediate transfer belt becomes the shortest distance).

[0080] In addition, in this embodiment, the drive roller 33 that conveys (rotates) the intermediate transfer belt 31 is driven by the belt drive motor 132a of the belt drive section 132. Figure 3 The transfer speed (surface movement speed) of the intermediate transfer belt 31 is defined as V0.

[0081] In this embodiment, when the residual toner Tr is removed from the intermediate transfer belt 31 by the cleaning device 80, the circumferential speed (rotation speed) of the first brush 81 and the second brush 82 is set by the rotation speed (rpm) of the cleaning motor 133a as follows. That is, the rotation speed of the cleaning motor 133a is set to a first rotation speed Nr, such that the circumferential speed V1 of the first brush 81 and the circumferential speed V2 of the second brush 82 have the following relationship with respect to the conveying speed V0 of the intermediate transfer belt 31.

[0082] V1 = 0.25 × V0

[0083] V2 = 0.25 × V0

[0084] This is a necessary setting for sufficiently removing residual toner Tr with a assumed maximum concentration from the intermediate transfer belt 31 (essentially leaving no toner on the intermediate transfer belt 31). When the circumferential speeds V1 and V2 of the first brush 81 and the second brush 82 are set greater than these, the number of times the first brush 81 and the second brush 82 rub against the intermediate transfer belt 31 increases, making it possible for the lifespan of components such as the intermediate transfer belt 31, the first brush 81, and the second brush 82 to be shortened due to wear and other factors.

[0085] Cleaning procedures during image correction

[0086] Figure 8 This is a schematic cross-sectional view of the cleaning device 80 during the image correction operation in this embodiment (when a patch pattern is formed on the intermediate transfer belt 31), showing a section that is approximately perpendicular to the rotation axis of the secondary transfer inner roller 32.

[0087] Most of the toner in the patch pattern Tp that has passed through the secondary transfer section N2 is charged to the negative polarity (-). This is because the patch pattern Tp passes through the secondary transfer section N2 in a substantially intact state when it is transferred to the intermediate transfer belt 31. Therefore, the patch pattern Tp passes through the first cleaning section CL1 without being transferred to the first brush 81, which is subjected to a first cleaning bias with a negative polarity (-). Then, when the patch pattern Tp reaches the second cleaning section CL2, the patch pattern Tp is transferred to the second brush 82, which is subjected to a second cleaning bias with a positive polarity (+). In the same manner as the operation during image formation described above, the toner transferred to the second brush 82 is contained in the housing 88 and collected in a toner collection container (not shown).

[0088] Since the patch pattern Tp is not transferred to the recording material S, its toner concentration (toner dosage per unit area) is greater than the toner concentration of the residual toner Tr. Therefore, in order to sufficiently remove the patch pattern Tp from the intermediate transfer belt 31 (essentially leaving no patch pattern Tp on the intermediate transfer belt 31), it is necessary to increase the number of times the conductive fibers constituting the second brush 82 come into contact with and rub against the surface of the intermediate transfer belt 31. In other words, when removing the patch pattern Tp from the intermediate transfer belt 31, it is necessary to set the circumferential speed V2 of the second brush 82 to be greater than when removing the residual toner Tr from the intermediate transfer belt 31. In this embodiment, when removing the patch pattern Tp from the intermediate transfer belt 31 by the cleaning device 80, the circumferential speed of the second brush 82 is set by the revolutions of the cleaning motor 133a as follows. That is, the rotation speed of the cleaning drive motor 133a is set to the second rotation speed Np, so that the circumferential speed V2 of the second brush 82 has the following relationship with the transmission speed V0 of the intermediate transfer belt 31.

[0089] V2 = 0.5 × V0

[0090] In this way, in this embodiment, the second revolution Np of the cleaning motor 133a during the image correction operation (when removing the patch pattern Tp) is greater than the first revolution Nr of the cleaning motor 133a during the image formation operation (when removing residual toner Tr from the transfer) (Np>Nr). In other words, in this embodiment, the revolution of the cleaning motor 133a switches between the image formation operation and the image correction operation.

[0091] In this embodiment, the first brush 81, the second brush 82, the first bias roller 83, the second bias roller 84, and the toner collecting screw 87 are driven and connected via a gear system. Therefore, their rotational speeds become greater during image correction operations than during image formation. In other words, in this embodiment, during image correction operations, the circumferential speeds V1 and V2 of the first brush 81 and the second brush 82 are set by the rotational speed of the cleaning motor 133a as follows.

[0092] V1 = 0.5 × V0

[0093] V2 = 0.5 × V0

[0094] In this embodiment, the transport speed V0 of the intermediate transfer belt 31 is substantially the same during image formation (when removing residual toner Tr) and during image correction operation (when removing patch patterns Tp). Furthermore, in this embodiment, the settings for the first and second cleaning bias voltages are substantially the same during image formation (when removing residual toner Tr) and during image correction operation (when removing patch patterns Tp); however, these settings can also be different.

[0095] Incidentally, the first revolution Nr of the cleaning motor 133a is represented by the revolution of the cleaning motor 133a when removing residual toner Tr from the intermediate transfer belt 31 by the second brush 82. In other words, the first revolution Nr of the cleaning motor 133a is represented by the revolution of the cleaning motor 133a during the time period when the image forming area (the area to be printed) on the intermediate transfer belt 31 passes through the second cleaning section CL2 during image forming.

[0096] Furthermore, the second rotation number Np of the cleaning motor 133a is represented by the rotation number of the cleaning motor 133a when removing the patch pattern Tp from the intermediate transfer belt 31 by the second brush 82. In other words, the second rotation number Np of the cleaning motor 133a is represented by the rotation number of the cleaning motor 133a during the time period during which the area where the patch pattern Tp is formed on the intermediate transfer belt 31 passes through the second cleaning section CL2 in an image correction operation. In the case of forming multiple patch patterns Tp on the intermediate transfer belt 31 in an image correction operation, the time period during which the area where the patch pattern Tp is formed passes through the second cleaning section CL2 can be the time period from when the foremost part of the multiple patch patterns in the movement direction on the surface of the intermediate transfer belt 31 reaches the second cleaning section CL2 until the last part of the multiple patch patterns in the movement direction on the surface of the intermediate transfer belt 31 has completed passing through the second cleaning section CL2.

[0097] Alternatively, this can be restated as follows: During image formation (when removing residual toner Tr), the circumferential speed of the second brush 82 is defined as the first circumferential speed Vr, and during image correction operation (when removing patch pattern Tp), the circumferential speed of the second brush 82 is defined as the second circumferential speed Vp. In this case, in this embodiment, the second circumferential speed Vp is faster than the first circumferential speed Vr (Vp>Vr). In other words, in this embodiment, the circumferential speed of the second brush 82 is switched between image formation and image correction operation. Further, in this embodiment, the ratio Vp / V0 of the circumferential speed of the second brush 82 to the conveying speed V0 of the intermediate transfer belt 31 during image correction operation (when removing patch pattern Tp) is greater than the ratio Vr / V0 during image formation (when removing residual toner Tr) (Vp / V0>Vr / V0). In other words, in this embodiment, this ratio is switched between image formation and image correction operation. Typically, the circumferential speed of the second brush 82 can be changed (controlled) by altering (controlling) the rotational speed of the drive motor, as in this embodiment. However, it is not limited to this, but can be configured such that the circumferential speed of the second brush 82 can be changed (controlled) by a speed-changing mechanism provided in the drive transmission section that transmits drive from the drive motor to the second brush 82 as a speed-changing device. Furthermore, from the viewpoint of longer component life and cleaning performance, it is suitable that the first circumferential speed Vr is 20% or more and 80% or less of the second circumferential speed Vp (0.2×Vp≤Vr≤0.8×Vp). Generally, the first circumferential speed Vr is 30% or more and 70% or less of the second circumferential speed Vp (0.3×Vp≤Vr≤0.7×Vp). Incidentally, as mentioned above, in this embodiment, in conjunction with the second brush 82, the circumferential speed of the first brush 81 becomes faster during the image correction operation (when removing the patch pattern Tp) than the circumferential speed of the first brush 81 during the image formation operation (when removing the residual toner Tr from the transfer).

[0098] <Moments for switching cleaning speeds>

[0099] When switching the rotation speed of the cleaning motor 133a, the driving load on the intermediate transfer belt 31 changes due to the change in the circumferential speeds V1 and V2 of the first brush 81 and the second brush 82. This results in a potential temporary fluctuation in the transport speed V0 of the intermediate transfer belt 31 and the rotational speed of the photosensitive drum 11, which is driven by contact with the intermediate transfer belt 31. Therefore, if the rotation speed of the cleaning motor 133a is switched during image formation (during secondary transfer of the printed image, or during exposure of the printed image), image defects such as width-direction stripes (impact images) may occur.

[0100] To suppress the occurrence of such image defects, it is preferable to switch the rotation speed of the cleaning motor 133a (the circumferential speeds V1 and V2 of the first brush 81 and the second brush 82) at the following times.

[0101] That is, when switching the rotation speed of the cleaning motor 133a (the circumferential speeds V1 and V2 of the first brush 81 and the second brush 82) while the photosensitive drum 11 and the intermediate transfer belt 31 are rotating, it is preferable to perform the switching during non-image formation periods, that is, when the formation (exposure, development), primary transfer, and secondary transfer of the printed image are not performed.

[0102] For example, preferably, after the recording material S on which the last printed image immediately before the image correction operation is interrupted has passed through the secondary transfer section N2, the rotation speed of the cleaning motor 133a is switched from a first rotation speed Nr to a second rotation speed Np. In other words, preferably, after the recording material S on which the last printed image immediately before the image correction operation is interrupted has passed through the secondary transfer section N2, the circumferential speed of the second brush 82 is switched from a first circumferential speed Vr to a second circumferential speed Vp. This makes it possible to suppress image defects such as width-direction stripes caused by fluctuations in the conveying speed of the intermediate transfer belt 31 due to changes in the drive load of the intermediate transfer belt 31, as described above.

[0103] Furthermore, for example, it is preferable to switch the rotation speed of the cleaning motor 133a from the second rotation speed Np to the first rotation speed Nr before the start of exposure (image writing) associated with the printed image to be formed on the first recording material S immediately after the image correction operation is interrupted. In other words, it is preferable to switch the circumferential speed of the second brush 82 from the second circumferential speed Vp to the first circumferential speed Vr before the start of exposure (image writing) associated with the printed image to be formed on the first recording material S immediately after the image correction operation is interrupted. As a result, it becomes possible to suppress the occurrence of image defects such as width direction stripes caused by fluctuations in the conveying speed of the intermediate transfer belt 31 and fluctuations in the rotation speed of the photosensitive drum 11 due to changes in the drive load of the intermediate transfer belt 31, as described above.

[0104] use Figure 9 The switching operation of the rotational speed (drive speed) of the cleaning motor 133a associated with the image correction operation performed prior to the image formation operation will be further described. Figure 9 It is a flowchart used to describe the control of this operation.

[0105] When a print job is input to the image forming apparatus 100 (S101), the control unit 110 starts driving the photosensitive drum 11 and the intermediate transfer belt 31, and controls the cleaning motor 133a to start driving at a first revolution Nr (S102). The print job is input to the image forming apparatus 100 based on operations performed by the user via an external device such as a host computer. Thereafter, the control unit 110 acquires information about the image forming apparatus 100, such as the standby time since the previous print job (S103), and determines whether an image correction operation is needed based on this information (S104). This is because there is a possibility that, for example, the charge of the toner in the developing unit 14 changes as the standby time increases, thus the density of the printed image may exceed the appropriate density while maintaining the settings for the previous print job. The control unit 110 can obtain the standby time of the image forming apparatus 100, for example, from the end time of the previous print job stored in the memory 112 (non-volatile memory) and the start time of the current print job. Furthermore, for example, if the standby time exceeds a predetermined time, the control unit 110 determines that image density control is required.

[0106] If the control unit 110 determines in S104 that the image correction operation (image density control) is not necessary, the control unit 110 proceeds the process to the process in S110. On the other hand, if the control unit 110 determines in S104 that the image correction operation (image density control) is necessary, the control unit 110 controls the rotation speed of the cleaning motor 133a to increase from a first rotation speed Nr to a second rotation speed Np (S105). Thereafter, the control unit 110 controls the formation of the density patch pattern and the operation for image density control described above (S106). Incidentally, this moment of increasing the speed of the cleaning motor 133a is before the foremost part of the patch pattern on the intermediate transfer belt 31 reaches the second cleaning section CL2 (in this embodiment, before the exposure of the photosensitive drum 11 used to form the patch pattern).

[0107] Subsequently, after the last part of the patch pattern on the intermediate transfer belt 31 reaches the second cleaning section CL2 (S107), the control section 110 controls the rotation speed of the cleaning motor 133a to decrease from the second rotation speed Np to the first rotation speed Nr (S108). As a result, the patch pattern is properly removed from the intermediate transfer belt 31.

[0108] Then, after the rotation speed of the cleaning motor 133a is switched to the first rotation speed Nr, the control unit 110 begins to expose the printed image via the exposure device 13 (S109). In other words, the control unit 110 controls the formation of an electrostatic latent image of the printed image on the surface of the photosensitive drum 11Y, starting from the upstream image forming section 1Y along the moving direction of the surface of the intermediate transfer belt 31, by irradiating the photosensitive drum 11Y with a laser by the exposure device 13Y. Thereafter, the control unit 110 controls the secondary transfer (printing operation) of the printed image (S110).

[0109] This allows for the suppression of temporary fluctuations in the transport speed of the intermediate transfer belt 31 and the rotation speed of the photosensitive drum 11, and also suppresses image defects such as width-direction stripes in the printed image (product). Afterward, the control unit 110 terminates the printing operation.

[0110] Next, use Figure 10 The switching operation of the rotation speed (drive speed) of the cleaning motor 133a associated with the image correction operation performed midway through continuous printing will be further described. Figure 10 It is a flowchart used to describe the control of this operation.

[0111] When a print job is input to the image forming apparatus 100 (S201), the control unit 110 starts driving the photosensitive drum 11 and the intermediate transfer belt 31, and controls the cleaning motor 133a to start driving at a first revolution Nr (S202). The print job is input to the image forming apparatus 100 based on operations from the user via an external device such as a host computer. Thereafter, the control unit 110 controls the formation of the printed image and the secondary transfer of the printed image (printing operation) (S203). Thereafter, for example, the control unit 110 acquires information about the image forming apparatus 100, such as the temperature of the exposure unit 13 (S204), and determines whether an image correction operation is required based on this information (S205). The control unit 110 acquires, for example, the detection result of the temperature of the exposure unit 13 from a temperature sensor (not shown), which is a temperature detection device provided in the exposure unit 13. And, for example, if the temperature rise (ΔT) of the exposure unit 13 becomes ΔT>3°C, the control unit 110 determines that color misalignment correction control is necessary.

[0112] If the control unit 110 determines in S205 that the image correction operation (color misalignment correction control) is not necessary, the control unit 110 proceeds the process to S213. On the other hand, if the control unit 110 determines in S205 that the image correction operation (color misalignment correction control) is necessary, the control unit 110 begins the formation of the registration patch pattern for color misalignment correction control as described above (S206). Incidentally, the control unit 110 then appropriately performs operations for color misalignment correction control, such as patch pattern detection. Then, after the rear end of the recording material S on which the last printed image formed before the patch pattern formation began has been transferred twice passes through the secondary transfer section N2 (S207), the control unit 110 controls the rotation speed of the cleaning motor 133a to increase from a first rotation speed Nr to a second rotation speed Np (S208). Incidentally, the speed of the cleaning motor 133a is increased at the moment before the foremost part of the patch pattern on the intermediate transfer belt 31 reaches the second cleaning section CL2. This allows for the suppression of fluctuations in the conveying speed of the intermediate transfer belt 31 while the recording material S passes through the secondary transfer section N2, and also suppresses the occurrence of image defects such as width-direction stripes in the printed image transferred secondary to the recording material S.

[0113] Subsequently, after the foremost part of the patch pattern on the intermediate transfer belt 31 reaches the second cleaning section CL2 (S209) and further after the last part of the patch pattern on the intermediate transfer belt 31 reaches the second cleaning section CL2 (S210), the control section 110 controls the rotation speed of the cleaning motor 133a to decrease from the second rotation speed Np to the first rotation speed Nr (S211). Thus, the patch pattern is properly removed from the intermediate transfer belt 31.

[0114] Then, after the rotational speed of the cleaning motor 133a switches to the first rotational speed Nr, the control unit 110 begins (resumes) the exposure of the printed image via the exposure device 13 (S212). In other words, the control unit 110 controls the formation of an electrostatic latent image of the printed image on the surface of the photosensitive drum 11Y, starting from the upstream image forming section 1Y along the moving direction of the surface of the intermediate transfer belt 31, by irradiating the photosensitive drum 11Y with a laser by the exposure device 13Y. Thereafter, the control unit 110 controls the secondary transfer (printing operation) of the printed image (S203). As a result, temporary fluctuations in the conveying speed of the intermediate transfer belt 31 and the rotational speed of the photosensitive drum 11 can be suppressed, and image defects such as width-direction stripes in the printed image (product) can be suppressed. In addition, if the output of all printed images in the printing job is completed (S213), the control unit 110 terminates the printing job.

[0115] In this embodiment, the image forming apparatus 100 includes: an image forming section 1, which is provided with a rotatable image carrier member (photosensitive drum) 11 carrying a toner image, and forms a toner image on the image carrier member 11; a rotatable intermediate transfer belt 31, on which the toner image is transferred from the image carrier member 11 to the intermediate transfer belt 31, and the intermediate transfer belt forms a primary transfer section N1 and a secondary transfer section N2, wherein the toner image is transferred from the image carrier member 11 to the intermediate transfer belt 31 at the primary transfer section, and the toner image is transferred from the intermediate transfer belt 31 to the recording material S at the secondary transfer section; a brush (second brush) 82, which contacts the intermediate transfer belt 31 at a cleaning section (second cleaning section) CL2 on the downstream side of the secondary transfer section N2 and the upstream side of the primary transfer section N1 relative to the rotation direction of the intermediate transfer belt 31, and forms a toner image on the image carrier member 11 by rotating the brush. Simultaneously, electrostatic attraction of toner is used to remove toner from the intermediate transfer belt 31; a driving section (cleaning driving section) 133, which drives a brush 82; and a control section 110, which can control the driving section 133, wherein the control section 110 can perform control to perform image forming operation and adjustment operation. In the image forming operation, the toner image formed by the image forming section 1 is transferred to the recording material S. In the adjustment operation, the image forming section 1 forms an adjustment toner image (patchy pattern) on the intermediate transfer belt 31. The control section controls the driving section 133 in the image forming operation such that when the residual toner Tr remaining on the intermediate transfer belt 31 is removed from the intermediate transfer belt 31 by the brush 82, the brush 82 rotates at a first circumferential speed Vr, and when the adjustment toner image is removed from the intermediate transfer belt 31 by the brush 82, the brush 82 rotates at a second circumferential speed Vp, which is faster than the first circumferential speed Vr.

[0116] In this embodiment, the control unit 110 controls the drive unit 133 such that when residual toner is removed from the intermediate transfer belt 31 by the brush 82, the motor (cleaning motor) 133a provided in the drive unit 133 rotates at a first speed Nr, and when the toner image is removed from the intermediate transfer belt 31 by the brush 82, the motor 133a rotates at a second speed Np, which is greater than the first speed Nr. Here, the image forming unit 1 includes an exposure device 13 and a developing device 14. The exposure device exposes the image carrier member 11 and forms an electrostatic image on the image carrier member 11, and the developing device supplies toner to the electrostatic image formed on the image carrier member 11 and forms a toner image on the image carrier member 11. In this case, it is preferable that when performing the image forming operation after performing the adjustment operation, the control unit 110 controls the moment when changing the rotational speed of the motor 133a from the second rotational speed Np to the first rotational speed Nr, so that this moment is after the last part of the toner image formed in the adjustment operation has reached the cleaning section CL2 in the movement direction along the surface of the intermediate transfer belt 31, and before the electrostatic image begins to form through the exposure device 13 in the image forming operation. Furthermore, it is preferable that when performing the adjustment operation after performing the image forming operation, the control unit 110 controls the moment when changing the rotational speed of the motor 133a from the first rotational speed Nr to the second rotational speed Np, so that this moment is after the last recording material S in the image forming operation has passed through the secondary transfer section N2, and before the foremost part of the toner image formed in the adjustment operation has reached the cleaning section CL2 in the movement direction along the surface of the intermediate transfer belt 31. Incidentally, it can be restated to say that it is preferable that when performing the image forming operation after performing the adjustment operation, the moment when changing the circumferential speed of the brush 82 from the second circumferential speed Vp to the first circumferential speed Vr is the same as described above. Alternatively, it can be restated to mean that, preferably, when performing an adjustment operation after performing an image forming operation, the moment when the circumferential speed of brush 82 is changed from the first circumferential speed Vr to the second circumferential speed Vp is the same as described above.

[0117] Additionally, in this embodiment, the image forming apparatus 100 includes an application portion (second cleaning power supply) 126 that applies a bias voltage with a positive polarity (+) to the cleaning portion CL2, which causes the toner with a normal charge polarity (-) to move from the intermediate transfer belt 31 to the brush 82. In addition, in this embodiment, the image forming apparatus 100 includes another brush (first brush) 81 and another application portion (first cleaning power supply) 125. The other brush contacts the intermediate transfer belt 31 at another cleaning portion (first cleaning portion) CL1 on the downstream side of the secondary transfer portion N2 and the upstream side of the primary transfer portion N1 in the rotation direction of the intermediate transfer belt 31, and removes the toner from the intermediate transfer belt 31 by electrostatically attracting the toner while rotating. The other application portion applies a bias voltage with a negative polarity (-) to the other cleaning portion CL1, which causes the toner charged to a polarity (+) opposite to the normal charge polarity of the toner to move from the intermediate transfer belt 31 to the other brush 81. The drive portion 133 drives the brush 82 and the other brush 81, and when the brush 82 rotates at a first circumferential speed, the other brush 81 rotates at a third circumferential speed, and when the brush 82 rotates at a second circumferential speed, the other brush 81 rotates at a fourth circumferential speed that is faster than the third circumferential speed.

[0118] As described above, according to this embodiment, a longer lifespan can be achieved for components including the intermediate transfer belt 31 and the first and second brushes 81 and 82, while being able to properly remove the patch pattern from the intermediate transfer belt 31.

[0119] [Other embodiments]

[0120] As described above, the present invention has been described with reference to specific embodiments, but the present invention is not limited to the above embodiments.

[0121] In the above embodiment, the drive roller 33 is used as a common opposing roller for the first and second brushes 81 and 82, but it can also be configured to independently provide opposing rollers for each of the first and second brushes 81 and 82.

[0122] Furthermore, in the above embodiments, voltage is applied to the first and second bias rollers 83 and 84, but the method of supplying the cleaning current is not limited to this. For example, rollers opposite to the first and second brushes 81 and 82 across the intermediate transfer belt 31 can be provided independently, and voltage can be applied to these rollers. In this case, the first and second brushes 81 and 82 can be configured as opposing members and grounded via the first and second bias rollers 83 and 84. Additionally, in this case, a voltage with the opposite polarity to the voltage applied to the first and second bias rollers 83 and 84 in the above embodiments can be applied to each roller opposite to the first and second brushes 81 and 82. Alternatively, the voltage can be applied directly to the first and second brushes 81 and 82 (or the first and second brushes 81 and 82 can be directly grounded).

[0123] Furthermore, in the above embodiment, the cleaning device 80 includes two brushes, namely a first brush 81 and a second brush 82, but the present invention is not limited to this configuration. If residual toner Tr can be sufficiently removed from the intermediate transfer belt 31 using only one brush, then the number of brushes can be one. In this case, for example, during image formation, a cleaning bias with a negative polarity (-) is applied to the brush to remove residual toner Tr from the intermediate transfer belt 31. And, for example, during image correction operations, to remove patch patterns Tp from the intermediate transfer belt 31, it is sufficient to switch to applying a cleaning bias with a positive polarity (+) to the brush.

[0124] According to the present invention, a longer lifespan for the intermediate transfer belt and cleaning components can be achieved while being able to properly remove the toner image from the intermediate transfer belt.

[0125] While the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims should be interpreted in the broadest possible sense to include all such modifications and equivalent structures and functions.

Claims

1. An image forming apparatus, comprising: A rotatable image carrier member configured to carry a toner image; An exposure apparatus configured to expose the image carrier member and form an electrostatic image on the image carrier member; A rotatable intermediate transfer belt, wherein the toner image is transferred from the image carrier to the intermediate transfer belt, the intermediate transfer belt being configured to form a primary transfer portion and a secondary transfer portion, the toner image being transferred from the image carrier to the intermediate transfer belt at the primary transfer portion, and the toner image being transferred from the intermediate transfer belt to the recording material at the secondary transfer portion; A brush, the direction of rotation of the brush relative to the intermediate transfer belt, contacts the intermediate transfer belt at a cleaning portion on the downstream side of the secondary transfer portion and the upstream side of the primary transfer portion, and is configured to remove toner from the intermediate transfer belt by electrostatic attraction while rotating. The driving section is configured to drive the brush; as well as A controller, configured to control the drive unit, The controller controls the execution of image forming and adjustment operations. In the image forming operation, a toner image formed on the intermediate transfer belt is transferred to the recording material. In the adjustment operation, an adjustment toner image is formed on the intermediate transfer belt. In the image forming operation, the drive section is controlled such that when the brush removes residual toner from the intermediate transfer belt, the brush rotates at a first circumferential speed Vr, and when the toner image is removed from the intermediate transfer belt, the brush rotates at a second circumferential speed Vp, which is faster than the first circumferential speed Vr. In the case where the adjustment operation is performed during a continuous image forming operation that continuously forms images onto multiple recording materials, including a first recording material and a second recording material following the first recording material, the adjustment operation occurs after image forming is performed on the first recording material and before image forming is performed on the second recording material. The controller controls the drive section to change the speed of the brush from the first circumferential speed Vr to the second circumferential speed Vp after the first recording material has passed through the secondary transfer section and before the formation of the electrostatic image of the toner image begins.

2. An image forming apparatus, comprising: A rotatable image carrier member configured to carry a toner image; An exposure apparatus configured to expose the image carrier member and form an electrostatic image on the image carrier member; A rotatable intermediate transfer belt, wherein the toner image is transferred from the image carrier to the intermediate transfer belt, the intermediate transfer belt being configured to form a primary transfer portion and a secondary transfer portion, the toner image being transferred from the image carrier to the intermediate transfer belt at the primary transfer portion, and the toner image being transferred from the intermediate transfer belt to the recording material at the secondary transfer portion; A brush, the direction of rotation of the brush relative to the intermediate transfer belt, contacts the intermediate transfer belt at a cleaning portion on the downstream side of the secondary transfer portion and the upstream side of the primary transfer portion, and is configured to remove toner from the intermediate transfer belt by electrostatic attraction while rotating. The driving section is configured to drive the brush; as well as A controller, configured to control the drive unit, The controller controls the execution of image forming and adjustment operations. In the image forming operation, toner formed on the intermediate transfer belt is transferred to the recording material. In the adjustment operation, an adjustment toner image is formed on the intermediate transfer belt. In the image forming operation, the drive section is controlled such that when the brush removes residual toner from the intermediate transfer belt, the brush rotates at a first circumferential speed Vr, and when the toner image is removed from the intermediate transfer belt, the brush rotates at a second circumferential speed Vp, which is faster than the first circumferential speed Vr. In the case where the adjustment operation is performed during a continuous image forming operation that continuously forms images onto multiple recording materials, including a first recording material and a second recording material following the first recording material, the adjustment operation occurs after image forming is performed on the first recording material and before image forming is performed on the second recording material. The controller controls the drive section to change the speed of the brush from the second circumferential speed Vp to the first circumferential speed Vr at a moment after the last part of the toner image formed in the adjustment operation along the surface of the intermediate transfer belt has reached the cleaning section and before the formation of an electrostatic image for the second recording material begins.

3. An image forming apparatus, comprising: A rotatable image carrier member configured to carry a toner image; An exposure apparatus configured to expose the image carrier member and form an electrostatic image on the image carrier member; A rotatable intermediate transfer belt, wherein the toner image is transferred from the image carrier to the intermediate transfer belt, the intermediate transfer belt being configured to form a primary transfer portion and a secondary transfer portion, the toner image being transferred from the image carrier to the intermediate transfer belt at the primary transfer portion, and the toner image being transferred from the intermediate transfer belt to the recording material at the secondary transfer portion; A brush, the direction of rotation of the brush relative to the intermediate transfer belt, contacts the intermediate transfer belt at a cleaning portion on the downstream side of the secondary transfer portion and the upstream side of the primary transfer portion, and is configured to remove toner from the intermediate transfer belt by electrostatic attraction while rotating. The driving section is configured to drive the brush; as well as A controller, configured to control the drive unit, The controller controls the execution of image forming and adjustment operations. In the image forming operation, toner formed on the intermediate transfer belt is transferred to the recording material. In the adjustment operation, an adjustment toner image is formed on the intermediate transfer belt. In the image forming operation, the drive section is controlled such that when the brush removes residual toner from the intermediate transfer belt, the brush rotates at a first circumferential speed Vr, and when the toner image is removed from the intermediate transfer belt, the brush rotates at a second circumferential speed Vp, which is faster than the first circumferential speed Vr. In the case where the adjustment operation is performed using an image formation start signal before performing an image formation operation on the recording material of the first sheet of work, The controller controls the drive section to change the speed of the brush from the first circumferential speed Vr to the second circumferential speed Vp before the formation of the electrostatic image of the toner image begins.

4. An image forming apparatus, comprising: A rotatable image carrier member configured to carry a toner image; An exposure apparatus configured to expose the image carrier member and form an electrostatic image on the image carrier member; A rotatable intermediate transfer belt, wherein the toner image is transferred from the image carrier to the intermediate transfer belt, the intermediate transfer belt being configured to form a primary transfer portion and a secondary transfer portion, the toner image being transferred from the image carrier to the intermediate transfer belt at the primary transfer portion, and the toner image being transferred from the intermediate transfer belt to the recording material at the secondary transfer portion; A brush, the direction of rotation of the brush relative to the intermediate transfer belt, contacts the intermediate transfer belt at a cleaning portion on the downstream side of the secondary transfer portion and the upstream side of the primary transfer portion, and is configured to remove toner from the intermediate transfer belt by electrostatic attraction while rotating. The driving section is configured to drive the brush; as well as A controller, configured to control the drive unit, The controller controls the execution of image forming and adjustment operations. In the image forming operation, toner formed on the intermediate transfer belt is transferred to the recording material. In the adjustment operation, an adjustment toner image is formed on the intermediate transfer belt. In the image forming operation, the drive section is controlled such that when the brush removes residual toner from the intermediate transfer belt, the brush rotates at a first circumferential speed Vr, and when the toner image is removed from the intermediate transfer belt, the brush rotates at a second circumferential speed Vp, which is faster than the first circumferential speed Vr. In the case where the adjustment operation is performed using an image formation start signal before performing an image formation operation on the recording material of the first sheet of work, The controller controls the drive section to change the speed of the brush from the second circumferential speed Vp to the first circumferential speed Vr after the adjustment operation is performed and before an electrostatic image of the recording material on the first sheet for the job begins to be formed.

5. The image forming apparatus of claim 1, wherein the brush is a first brush and the cleaning portion is a first cleaning portion. The image forming apparatus includes: The second brush, which is in contact with the intermediate transfer belt at a second cleaning portion on the downstream side of the secondary transfer portion and the upstream side of the primary transfer portion, is configured to remove toner from the intermediate transfer belt by electrostatic attraction while rotating. A first application portion is configured to apply a bias voltage to a first cleaning portion, the bias voltage causing a toner charged to a polarity opposite to the normal charge polarity of the toner to move from the intermediate transfer belt to the first brush. as well as A second application portion, configured to apply a bias voltage to a second cleaning portion, causes toner charged to the same polarity as the normal charge of the toner to move from the intermediate transfer belt to the second brush. The driving component drives the first brush and the second brush.

6. The image forming apparatus of claim 5, wherein the controller controls the drive portion such that when the second brush rotates at the first circumferential speed Vr, the first brush rotates at a third circumferential speed, and when the second brush rotates at the second circumferential speed Vp, the first brush rotates at a fourth circumferential speed faster than the third circumferential speed.

Images