JP2019045649A - Image forming apparatus - Google Patents

Abstract

To solve the problem in which in a configuration where, when an image forming apparatus suspends image formation, the image forming apparatus transfers a toner image carried on an image carrier to an intermediate transfer body and subsequently recovers toner with cleaning means, a standby time until the image forming apparatus performs following image formation cannot be easily reduced.SOLUTION: An image forming apparatus applies a voltage having a negative polarity from a primary transfer power supply 207 to a primary transfer roller 206 to recover a toner carried on a photoconductor drum 301 to cleaning means 310. At this time, a toner primarily transferred from the photoconductor drum 301 to an intermediate transfer belt 205 is moved to a photoconductor drum 301 arranged downstream in the direction of movement of the intermediate transfer belt 205, and is subsequently recovered to cleaning means 310 of the downstream photoconductor drum 301.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a printer.

  Conventionally, an electrophotographic color image forming apparatus has a configuration in which a toner image is sequentially transferred from an image forming portion of each color to an intermediate transfer member, and further, the toner image is collectively transferred from the intermediate transfer member to a transfer material. It has been.

  In such an image forming apparatus, each color image forming section has a drum-shaped photosensitive member (hereinafter referred to as a photosensitive drum) as an image carrier. The toner image formed on the photosensitive drum of each image forming unit applies a voltage from a primary transfer power source to a primary transfer member provided opposite to the photosensitive drum via an intermediate transfer member such as an intermediate transfer belt. Thus, primary transfer is performed on the intermediate transfer member. Each color toner image primarily transferred from the image forming portion of each color to the intermediate transfer member is applied with a voltage from the secondary transfer power source to the secondary transfer member in the secondary transfer portion, thereby causing the paper or OHP from the intermediate transfer member. Secondary transfer is performed collectively on a transfer material such as a sheet. The toner images of the respective colors transferred to the transfer material are then fixed on the transfer material by fixing means.

  In Patent Document 1, when image formation is interrupted due to a phenomenon in which a transfer material stays in a conveyance path (hereinafter referred to as jam) or the like, toner remaining on a photosensitive drum or an intermediate transfer member can be provided on the intermediate transfer member. A configuration for collecting by a cleaning means is disclosed.

JP 2014-202772 A

  However, in the configuration of Patent Document 1, when the image formation is interrupted, the toner image carried on the photosensitive drum is transferred from the photosensitive drum to the intermediate transfer member, passed through the secondary transfer portion, and then cleaned by a cleaning unit. to recover. Since the next image formation cannot be performed during this period, it is difficult to shorten the waiting time until the next image formation.

  Accordingly, the present invention provides an image that can shorten the waiting time until the next image formation when the image formation is interrupted while the toner image is carried on the image carrier or the intermediate transfer member. An object is to provide a forming apparatus.

  The present invention relates to a first image carrier that carries a toner image, and an intermediate transfer member that is in contact with the first image carrier and to which a toner image carried on the first image carrier is primarily transferred. A first contact member provided corresponding to the first image carrier and contacting an inner peripheral surface of the intermediate transfer member; and a first power source for applying a voltage to the first contact member; A first collecting unit that contacts the first image carrier and collects toner remaining on the first image carrier; and a moving direction of the intermediate transfer member from the first image carrier. Corresponding to the second image carrier and the second image carrier disposed downstream of the intermediate transfer member and upstream of the secondary transfer portion for secondary transfer of toner from the intermediate transfer member to the transfer material. And a second contact member that contacts the inner peripheral surface of the intermediate transfer member, and a second that applies a voltage to the second contact member. A power source, a second recovery unit that contacts the second image carrier and collects toner remaining on the second image carrier, and a control unit that controls start and stop of an image forming operation. In the image forming apparatus, a toner image is primarily transferred from the first image carrier to the intermediate transfer member by applying a voltage of a predetermined polarity from the first power source to the first contact member. In the state, when the image forming operation is stopped by the control unit, the toner image carried on the first image carrier in contact with the intermediate transfer member is collected by the first collection unit. A voltage having a polarity opposite to the predetermined polarity is applied from the first power source to the first contact member, and the toner image primarily transferred from the first image carrier to the intermediate transfer member is transferred to the intermediate member. Moved from the transfer member to the second image carrier. And applying the reverse polarity voltage to the second contact member from the second power supply in order to recover in the serial second recovery means.

  According to the present invention, when the image formation is interrupted while the toner image is carried on the image carrier or the intermediate transfer member, it is possible to shorten the waiting time until the next image formation is performed. .

1 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus according to a first exemplary embodiment. FIG. 3 is a schematic diagram illustrating a configuration of an image forming unit according to the first exemplary embodiment. 3 is a schematic diagram illustrating distances between members in the image forming apparatus according to the first exemplary embodiment. FIG. 6 is a schematic diagram illustrating a range of toner that needs to be collected when the second transfer material is not fed in Embodiment 1. FIG. FIG. 6 is a schematic diagram illustrating a toner collecting operation when the second transfer material is not stored in the storage unit and the image forming operation is stopped in the first exemplary embodiment. FIG. 6 is a schematic diagram illustrating a range of toner that needs to be collected when the transport timing of the second transfer material is shifted in the first exemplary embodiment. FIG. 6 is a schematic diagram for explaining a toner collecting operation when the transport timing of the second transfer material is shifted in the first embodiment. FIG. 6 is a schematic diagram illustrating a transfer configuration of an image forming apparatus as a modified example of Embodiment 1. 6 is a schematic diagram illustrating toner collection when an image forming operation is stopped in Embodiment 2. FIG.

  The preferred embodiments of the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in the following examples should be changed as appropriate according to the configuration of the apparatus to which the invention is applied and various conditions. The present invention is not intended to be limited to the following examples.

Example 1
[Configuration of Image Forming Apparatus]
FIG. 1 is a schematic cross-sectional view illustrating the configuration of an image forming apparatus 200 according to the present embodiment. As shown in FIG. 1, an image forming apparatus 200 is an intermediate transfer type color image forming apparatus using an electrophotographic system, and is yellow (Y), magenta (M), cyan (C), and black (K). The four image forming units SY, SM, SC, and SK for forming images of the respective colors are provided. In this embodiment, the configuration and operation of the image forming units SY, SM, SC, and SK are substantially the same except that the color of the image to be formed is different. Therefore, unless otherwise distinguished, the subscripts Y, M, C, and K given to the reference numerals to indicate the elements provided for any color will be omitted.

  The image forming apparatus 200 is connected to a personal computer (not shown) that is a host device. An image formation start command and an image signal from the host device are transmitted to a controller 202 as a control unit, and the controller 202 controls various units, whereby the image forming apparatus 200 executes image formation.

  FIG. 2 is a schematic diagram illustrating the configuration of the image forming unit S. As shown in FIG. 2, the image forming unit S includes a photosensitive drum 301 as an image carrier, a charging roller 302, an exposure unit 204, a developing unit 309, and a cleaning unit 310 as a collection unit.

  When the image forming operation is started, the photosensitive drum 301 is rotationally driven in a direction indicated by an arrow B at a predetermined peripheral speed (214 mm / s in this embodiment) by a driving unit (not shown). Thereafter, the surface of the photosensitive drum 301 is uniformly charged by a charging roller 302 to which a voltage is applied from a charging power source (not shown). Next, based on the image information input to the controller 202, the exposure unit 204 irradiates the photosensitive drum 301 with a laser, whereby an electrostatic latent image is formed on the surface of the photosensitive drum 301.

  The developing unit 309 includes a developing container 306 that stores toner and a developing roller 303 that carries the toner stored in the developing container 306. The electrostatic latent image formed on the photosensitive drum 301 is developed as a toner image by the toner carried on the developing roller 303 that rotates in the direction indicated by the arrow C in response to a driving force from a driving unit (not shown). At this time, a developing voltage having the same polarity as the normal charging polarity of the toner (negative polarity in this embodiment) is applied to the developing roller 303 from a developing high-voltage power supply (not shown).

  In this embodiment, the electrostatic latent image formed on the photosensitive drum 301 is developed by a reversal development method. That is, the electrostatic latent image is developed as a toner image by adhering negatively charged toner having the same polarity as that of the photosensitive drum 301 to the exposed portion of the photosensitive drum 301 exposed by the exposure unit 204. . In this embodiment, the contact development method is used. However, the present invention is not limited to this, and a non-contact development method may be used. In this embodiment, the electrostatic latent image is developed using the reversal development method. However, the present invention is not limited to this, and the electrostatic latent image is formed with toner charged to a polarity opposite to the charged polarity of the photosensitive drum 301. The present invention can also be applied to an image forming apparatus that performs normal development.

  The cleaning unit 310 includes a cleaning blade 304 as a contact member that contacts the photosensitive drum 301 and collects toner adhering to the photosensitive drum 301, and a waste toner container 305 that stores toner collected by the cleaning blade 304. Have. In the present embodiment, a plate-like member made of urethane rubber as an elastic material is used as the cleaning blade 304 (blade member).

  As shown in FIG. 1, an endless and rotatable intermediate transfer belt 205 (intermediate transfer body) is stretched by a plurality of stretching members, and receives a driving force from a driving means (not shown) to receive a predetermined force. At a peripheral speed (214 mm / s in this embodiment). A primary transfer roller 206 as a contact member that contacts the inner peripheral surface of the intermediate transfer belt 205 is provided at a position facing the image forming unit S via the intermediate transfer belt 205, corresponding to each photosensitive drum 301. ing.

  The primary transfer roller 206 presses the intermediate transfer belt 205 toward the photosensitive drum 301 to form a primary transfer portion N1 where the photosensitive drum 301 and the intermediate transfer belt 205 come into contact with each other. Rotate. By applying a positive polarity (predetermined polarity) voltage from the primary transfer power source 207 to the primary transfer roller 206, the toner image formed on the photosensitive drum 301 is transferred from the photosensitive drum 301 to the intermediate transfer belt in the primary transfer portion N1. Primary transfer is performed to 205.

  Thereafter, along with the movement of the intermediate transfer belt 205, the toner image is sequentially transferred from the photosensitive drum 301 to the intermediate transfer belt 205 in the primary transfer unit N1 of each image forming unit S, and the target color is transferred to the intermediate transfer belt 205. A plurality of color toner images corresponding to the image are formed.

  The toner remaining on the photosensitive drum 301 without being transferred to the intermediate transfer belt 205 reaches a position where the cleaning blade 304 and the photosensitive drum 301 come into contact with the rotation of the photosensitive drum 301. Then, the toner is collected in the waste toner container 305 by the cleaning blade 304.

  The secondary transfer roller 214 is in contact with the outer peripheral surface of the intermediate transfer belt 205 at a position facing the opposing roller 215 that stretches the intermediate transfer belt 205 to form a secondary transfer portion N2. By applying a positive voltage from the secondary transfer power source 217 to the secondary transfer roller 214, the toner image primarily transferred to the intermediate transfer belt 205 is secondarily transferred to the transfer material P at the secondary transfer portion N2. The

  A pickup roller 209 serving as a feeding member is accommodated in a paper feeding cassette 208 serving as an accommodating portion in accordance with the timing at which each color toner image primarily transferred to the intermediate transfer belt 205 reaches the secondary transfer portion N2. The transfer material P is fed toward the secondary transfer portion N2. The transfer material P fed by the pickup roller 209 is separated one by one by the separation roller pair 210 and then conveyed to the conveyance roller 211, and conveyance is temporarily stopped by the conveyance roller 211.

  Thereafter, the transfer material P is transferred to the secondary transfer portion N2 via the registration sensor 212, the paper width sensor 213, and the like in accordance with a predetermined timing when the leading edge of the toner image carried on the intermediate transfer belt 205 reaches the secondary transfer portion N2. To be transported. The transfer material P on which the toner image is secondarily transferred in the secondary transfer portion N2 is heated and pressed by the fixing unit 216, whereby the toner of each color is melted and mixed and fixed on the transfer material P. The paper is discharged from the image forming apparatus 200 and stacked on a paper discharge tray 218. Here, the transfer speed of the transfer material P from the pickup roller 209 to the secondary transfer portion N2 in this embodiment is 214 mm / s.

  The toner remaining on the intermediate transfer belt 205 after the secondary transfer moves together with the intermediate transfer belt 205 and reaches a position where the charging brush 219 serving as a charging unit and the intermediate transfer belt 205 come into contact with each other. At this time, a positive voltage is applied to the charging brush 219 from the charging power source 220, and the toner remaining on the intermediate transfer belt 205 is charged to the positive polarity by the charging brush 219. Thereafter, the positively charged toner moves from the intermediate transfer belt 205 to the photosensitive drum 301Y due to a potential difference between the primary transfer roller 206Y to which the positive voltage is applied and the photosensitive drum 301Y. Then, the photosensitive drum 301Y is collected by the cleaning unit 310Y.

[Toner collection operation when image forming operation stops]
FIG. 3 is a schematic diagram illustrating the distance between each member in the image forming apparatus 200. As shown in FIG. 3, in this embodiment, the distance from the laser irradiation position on the photosensitive drum 301 </ b> Y to the secondary transfer portion N <b> 2 as compared with the distance that the transfer material P is conveyed from the pickup roller 209 to the secondary transfer portion N <b> 2. Is longer. That is, formation of an electrostatic latent image on the photosensitive drum 301Y is started before the transfer material P is fed by the pickup roller 209.

  Therefore, even if the controller 202 stops the image forming operation before the transfer material P is fed by the pickup roller 209, the toner image may already be primarily transferred from the photosensitive drum 301Y to the intermediate transfer belt 205. . When the controller 202 stops the image forming operation because the transfer material P is not properly fed, the toner that has been primarily transferred to the intermediate transfer belt 205 is collected in preparation for the next image forming operation. It is necessary to perform an action.

  Note that the case where the transfer operation of the transfer material P is not performed correctly means, for example, that the transfer material P is not stored in the paper feed cassette 208 or the type of the transfer material P stored in the paper feed cassette 208 is wrong. This is a case where the feeding timing of the transfer material P is deviated. In this embodiment, in order to form an image on the transfer material P based on the image information input from the host device to the controller 202, a series of operations performed by the controller 202 controlling the operations of various means. Is referred to as an image forming operation.

  As shown in FIG. 3, the distance from the laser irradiation position to each primary transfer portion N1 is expressed as a distance Dl1. In the configuration of this embodiment, the image forming units SY, SM, SC, and SK are arranged in the moving direction of the intermediate transfer belt 205, and the distance Dl1 is the same length in all the image forming units S. The length of the intermediate transfer belt 205 from the primary transfer portion N1Y to the primary transfer portion N1M is expressed as a distance Dym. Similarly, the length of the intermediate transfer belt 205 from the primary transfer portion N1M to the primary transfer portion N1C is Dmc, and the length of the intermediate transfer belt 205 from the primary transfer portion N1C to the primary transfer portion N1K is the distance Dck. write. The length of the intermediate transfer belt 205 from the primary transfer portion N1K to the secondary transfer portion N2 is expressed as a distance Dk2.

  The distance from the pickup roller 209 to the registration sensor 212 is represented as a distance Dpr, the distance from the registration sensor 212 to the paper width sensor 213 is represented as a distance Drw, and the distance from the paper width sensor 213 to the secondary transfer portion N2 is represented as a distance Dw2. In this embodiment, each distance defined above is set to the length shown in FIG. Further, in this embodiment, the transfer speed of the transfer material P from the pickup roller 209 to the secondary transfer portion N2, the rotational speed of the photosensitive drum 301, and the moving speed of the intermediate transfer belt 205 are substantially constant.

<When transfer material P is not fed>
When the number of transfer materials P stored in the paper feed cassette 208 is insufficient with respect to the image signal input to the controller 202 from the host device, that is, the transfer material P is supplied even though the image formation is started. A toner collecting operation when the toner is not sent will be described. FIG. 4 is a time chart in the case where an image forming operation for forming an image on two continuous transfer materials P is executed, and it is necessary to collect when the second transfer material P is not fed. FIG. 6 is a schematic diagram illustrating a toner range.

  An image signal (Y) in FIG. 4 represents an image signal of the image forming unit SY that starts the image forming operation earliest among the plurality of image forming units S. The state in which the image signal (Y) is ON is a state in which the laser is irradiated from the exposure unit 204 to the photosensitive drum 301Y, and an electrostatic latent image is formed on the photosensitive drum 301Y. The OFF state is in the photosensitive drum 301Y. The electrostatic latent image is not formed.

  Regarding the pickup roller 209, the state S0 shown in FIG. 4 is a state where the feeding of the transfer material P by the pickup roller 209 is not started. In the state S1, the transfer material P is synchronized with a predetermined timing at which the leading edge of the toner image carried on the intermediate transfer belt 205 reaches the secondary transfer portion N2 after the pickup roller 209 starts feeding the transfer material P. In this state, the transfer of the transfer material P is temporarily stopped. The state S2 is a state in which the transfer material P is fed by the rotation of the pickup roller 209. Regarding the paper width sensor 213 and the registration sensor 212, the state where the transfer material P is detected is turned ON, and the state where the transfer material P is not detected is turned OFF.

  As shown in FIG. 4, when the image forming operation is started, the pickup roller 209 rotates to start feeding the first transfer material P, whereby the electrostatic latent image is formed on the photosensitive drum 301. Before being performed, it can be determined whether the transfer material P is stored in the paper feed cassette 208. When the feeding of the first transfer material P is started by the pickup roller 209, the controller 202 controls the exposure unit 204 to start the formation of an electrostatic latent image on the photosensitive drum 301Y. At this time, the pickup roller 209 shifts from the state S0 to the state S1, and the first transfer material P is conveyed until the leading end position of the toner image primarily transferred to the intermediate transfer belt 205 reaches a predetermined position. Is paused.

  There is a distance of D11 + Dym + Dmc + Dck + Dk2 = 396.7 mm until the leading edge of the toner image formed on the photosensitive drum 301Y reaches the secondary transfer portion N2. On the other hand, the distance from the pickup roller 209 to the secondary transfer portion N2 is Dpr + Drw + Dw2 = 215.4 mm. Therefore, in order to align the leading edge of the toner image and the position of the first transfer material P at the secondary transfer portion N2, the leading edge of the toner image reaches 181.3 (396.7−) rather than reaching the secondary transfer portion N2. 215.4) As soon as mm, the pickup roller 209 is shifted from the state S01 to the state S02. Thus, the toner image primarily transferred from the photosensitive drum 301 to the intermediate transfer belt 205 can be secondarily transferred to a desired position on the first transfer material P fed by the pickup roller 209. .

  When the formation of the electrostatic latent image corresponding to the first transfer material P is completed on the photosensitive drum 301Y, the image signal (Y) is turned on again at time T1 after the image signal (Y) is turned off once. Thus, formation of an electrostatic latent image corresponding to the second transfer material P is started. At this time, the pickup roller 209 is still feeding the first transfer material P. When the feeding of the first transfer material P is completed, the next transfer material P is fed, and as shown in FIG. 4, the pickup roller 209 is in a state once from the state S2 at time T2. After S1 is reached, state S2 is entered again.

If the second transfer material P is not accommodated in the paper feed cassette 208, the state of the pickup roller 209 is changed from the state S2 to the state S0 at time T2, so that the second transfer material P is not fed. The information is transmitted to the controller 202. That is, when the second sheet of the transfer material P is determined not to be accommodated in the sheet feeding cassette 208, the photosensitive drum 301Y, toner images corresponding to a period of time Delta] t ₁₂ from the time T1 to time T2 form Then, primary transfer is performed on the intermediate transfer belt 205.

FIGS. 5A and 5B illustrate the toner collecting operation when the image forming operation is stopped because the second transfer material P is not accommodated in the sheet feeding cassette 208 in the configuration of this embodiment. It is a schematic diagram to do. In the configuration of the present embodiment, the interval between the first transfer material P and the subsequent second transfer material P (hereinafter referred to as a sheet interval) is 20 mm, and the rotational speed of the photosensitive drum 301 and the intermediate transfer are as follows. distance corresponding to the time is calculated from the moving speed of the belt 205 Delta] t ₁₂ is 161.3Mm. As shown in FIG. 5A, the distance corresponding to the time Δt ₁₂ is 161.3 mm, which is the length from the latent image start position of the photosensitive drum 301Y to between the image forming unit SM and the image forming unit SC. .

  In this embodiment, in the state of FIG. 5A, the first sheet is located downstream of the toner image (second image) corresponding to the second transfer material P in the moving direction of the intermediate transfer belt 205. A toner image (first image) corresponding to the transfer material P is primarily transferred. Since the interval between the sheets is 20 mm, the trailing edge of the first image is located downstream of the length of the intermediate transfer belt 205 by about 20 mm from the leading edge of the second image.

  Therefore, in this embodiment, after it is determined that the second transfer material P is not fed, the rear end of the first image has passed through the primary transfer portion N1K of the image forming portion SK. Later, the controller 202 stops the image forming operation. Then, a negative voltage is applied from the primary transfer power supply 207 to the primary transfer roller 206, and the toner collecting operation is started. However, when it is determined that the second transfer material P has not been fed, before the trailing edge of the first image passes through the primary transfer portion N1K of the image forming portion SK, The formation of the electrostatic latent image corresponding to the second image may be stopped.

  As shown in FIG. 5B, by applying a negative voltage from the primary transfer power source 207 to the primary transfer roller 206, the toner image primarily transferred to the intermediate transfer belt 205 is transferred from the photosensitive drum 301Y. Also electrostatically move to the photosensitive drums 301C to 301K arranged on the downstream side. Thereafter, the photosensitive drums 301C to 301K are collected by the cleaning units 310C to 310K. As a result, after the image forming operation is stopped, the toner image carried on the intermediate transfer belt 205 does not reach the secondary transfer portion N2, and the toner collecting operation is performed without soiling the secondary transfer roller 214. It becomes possible. Accordingly, it is not necessary to separately clean the secondary transfer roller 214, so that the standby time until the next image formation can be shortened.

<When the transfer timing of the transfer material P is shifted>
A toner collecting operation when the transfer material P is not conveyed at a desired timing for various reasons such as the pickup roller 209 idling with respect to an image signal input from the host device to the controller 202 will be described. FIG. 6 is a time chart in the case of executing an image forming operation for forming an image on two continuous transfer materials P, and it is necessary to collect when the transport timing of the second transfer material P is shifted. FIG. 6 is a schematic diagram illustrating a toner range.

  Whether or not the transfer material P has been conveyed at the correct timing is detected by the registration sensor 212. Therefore, a shift in the conveyance timing of the transfer material P is detected only after the transfer material P is conveyed to the position of the registration sensor 212. As described above, when the transfer material P is conveyed to the secondary transfer portion N2 by the pickup roller 209 or the conveyance roller 211, the tip of the toner image formed on the photosensitive drum 301Y is 181.3 mm from the formation start position of the electrostatic latent image. Started after progress. The distance from the pickup roller 209 to the registration sensor 212 is 126.6 mm.

Here, a time T1 in FIG. 6 is a time for forming an electrostatic latent image corresponding to the second image on the photosensitive drum 301Y, and a time T3 is a conveyance timing of the second transfer material P by the registration sensor 212. This is the time at which a deviation is detected. When the transport timing of the second transfer material P is deviated, a toner image is formed on each photosensitive drum 301 during the time Δt ₁₃ from time T1 to time T3, and from each photosensitive drum 301 to the intermediate transfer belt 205. Primary transfer is performed.

The distance corresponding to the time Δt ₁₂ calculated from the rotational speed of the photosensitive drum 301 and the moving speed of the intermediate transfer belt 205 is 307.9 (181.3 + 126.6) mm. In contrast, the distance from the electrostatic latent image formation start position in the image forming unit SY to the primary transfer unit N1K in the image forming unit SK is Dl1 + Dym + Dmc + Dck = 331.5 mm. Accordingly, as shown in FIG. 7A, the shift in the conveyance timing of the second transfer material P is caused by the registration sensor 212 before the leading edge of the second image arrives at the primary transfer portion N1K of the image forming portion SK. Detected by. FIGS. 7A and 7B are schematic diagrams for explaining the toner collection operation when the transport timing of the second transfer material P is shifted in the configuration of the present embodiment.

  In this embodiment, when a shift in the conveyance timing at the time of transfer of the second sheet P is detected, the controller 202 stops the image forming operation before the leading edge of the second image passes through the primary transfer portion N1K. Then, a toner collecting operation is performed. That is, a negative voltage is applied from the primary transfer power supply 207 to the primary transfer roller 206 before the leading edge of the second image passes through the primary transfer portion N1K.

  As a result, as shown in FIG. 7B, the toner image primarily transferred to the intermediate transfer belt 205 is electrostatically moved to the photosensitive drums 301M to 301K disposed on the downstream side of the photosensitive drum 301Y. . Thereafter, the photosensitive drums 301M to 301K are collected by the cleaning units 310M to 310K. On the other hand, the toner image carried on each photosensitive drum 301 in contact with the intermediate transfer belt 205 is collected on each cleaning means 310 of each photosensitive drum 301 without being primarily transferred to the intermediate transfer belt 205. Is done.

  As a result, after the image forming operation is stopped, the toner image carried on the intermediate transfer belt 205 does not reach the secondary transfer portion N2, and the cleaning operation can be performed without contaminating the secondary transfer roller 214. It becomes possible. Accordingly, it is not necessary to separately clean the secondary transfer roller 214, so that the standby time until the next image formation can be shortened.

<When the size of the transferred transfer material P is wrong>
Hereinafter, a toner collecting operation when the size of the transfer material P accommodated in the paper feed cassette 208 is wrong with respect to an image signal input from the host device to the controller 202 will be described. If the width of the transfer material P accommodated in the paper feed cassette 208 is narrower than the width of the image to be formed, there is a possibility that the image is formed outside the width of the transfer material P. In this case, since the toner that has not been transferred to the transfer material P adheres to the secondary transfer roller 214, in order not to soil the transfer material P during the next image formation, the image forming operation is once stopped and the secondary transfer roller P is not stained. It is necessary to clean the transfer roller 214. As a result, there is a possibility that the waiting time until the next image formation is started becomes long.

  Whether or not the size of the transfer material P is appropriate is detected by the paper width sensor 213. With respect to the transfer direction of the transfer material P, the paper width sensor 213 is arranged 18.8 mm downstream of the registration sensor 212. Accordingly, when the paper width sensor 213 detects that the size of the transfer material P fed by the pickup roller 209 is incorrect, toner image formation on each photosensitive drum 301 has already started. More specifically, a toner image is formed on each photosensitive drum 301 for a distance of 326.7 (307.9 + 18.8) mm from the electrostatic latent image formation start position on the photosensitive drum 301Y. To the intermediate transfer belt 205.

  As described above, the distance from the electrostatic latent image formation start position in the image forming unit SY to the primary transfer unit N1K in the image forming unit SK is 331.5 mm. Accordingly, an incorrect size of the transfer material P fed to the pickup roller 209 is detected by the paper width sensor 213 before the leading edge of the second image arrives at the primary transfer portion N1K of the image forming portion SK. The

  In this case, the toner carried on the intermediate transfer belt 205 and each photosensitive drum 301 is removed from the cleaning means by performing the same control as the toner collecting operation when the transfer timing of the transfer material P described above is shifted. 310 can be collected and collected. As a result, after the image forming operation is stopped by the controller 202, the toner image carried on the intermediate transfer belt 205 does not reach the secondary transfer portion N2, and the cleaning operation is performed without soiling the secondary transfer roller 214. Can be done. Accordingly, it is not necessary to separately clean the secondary transfer roller 214, so that the standby time until the next image formation can be shortened.

  In the present embodiment, the configuration in which negative voltage is applied from the four primary transfer power sources 207Y to 207K to the corresponding primary transfer rollers 206Y to 206K when performing the toner collecting operation has been described. . However, the present invention is not limited to this, and a negative voltage may be applied only to the primary transfer roller 206Y and the primary transfer roller 206K of the most downstream image forming unit SK. In such a configuration, the toner carried on the photosensitive drum 301Y is collected by the cleaning unit 310, and the toner primarily transferred to the intermediate transfer belt 205 is collected by the cleaning unit 310K. Even in this configuration, the same effect as in the present embodiment can be obtained.

  In this embodiment, four primary transfer power sources are provided for the four primary transfer rollers 206. However, the present invention is not limited to this, and some primary transfer power sources are shared. Also good. For example, a common primary transfer power source may be connected to the primary transfer rollers 5a to 5c, and one primary transfer power source may be connected to the primary transfer roller 5d. By reducing the number of primary transfer power supplies 207 that are high-voltage power supplies, the cost can be reduced and the image forming apparatus 200 can be downsized.

  In the configuration of the present embodiment, the description has been made based on the relative distance of each member in the configuration in which the rotation speed of the photosensitive drum 301, the moving speed of the intermediate transfer belt 205, and the conveyance speed of the transfer material P are substantially constant. Not limited to this. For example, even when the transfer material transport speed is not constant, when the control unit stops the image forming operation while the primary transfer of the toner image is being performed, the same control as in this embodiment is performed. Similar effects can be obtained.

  In this embodiment, the toner collection operation in the case where the transfer material P is not fed, the transfer timing of the transfer material P is shifted, or the size of the fed transfer material P is wrong is described. did. However, the present invention is not limited to this, and in other cases where the control unit stops the image forming operation in a state where the primary transfer of the toner image is being performed, the same control as in this embodiment is performed by performing the control in this embodiment. An effect can be obtained.

  FIG. 8 is a schematic diagram illustrating a transfer configuration of an image forming apparatus as a modification of the present embodiment. In the present exemplary embodiment, the configuration in which the toner remaining on the intermediate transfer belt 205 is positively charged by the charging brush 219 and then moved from the intermediate transfer belt 205 to the photosensitive drum 301 and collected by the cleaning unit 310 has been described. However, the present invention is not limited to this, and as shown in FIG. 8, a cleaning unit 503 having a blade (blade member) brought into contact with the intermediate transfer belt 205 is provided opposite to a roller that stretches the intermediate transfer belt 205 to provide an intermediate transfer. The toner remaining on the belt 205 may be collected.

(Example 2)
In the first exemplary embodiment, the configuration in which the toner carried on the photosensitive drum 301Y is collected by the cleaning unit 310 of the photosensitive drum 301Y when the image forming operation is stopped by the controller 202 has been described. On the other hand, in the second embodiment, when the image forming operation is stopped by the controller 202, the toner carried on the photosensitive drum 301Y is primarily transferred to the intermediate transfer belt 205 to clean the other photosensitive drum 301. It differs from the first embodiment in that it is collected at 310. In the present embodiment, the same reference numerals are given to the portions common to the first embodiment, and the description thereof is omitted.

  When images are continuously formed on a plurality of transfer materials P, the toner remaining on the intermediate transfer belt 205 without being transferred to the transfer material P in the secondary transfer portion N2 is charged positively by the charging brush 219. After that, it moves together with the intermediate transfer belt 205, moves from the intermediate transfer belt 205 to the photosensitive drum 301 </ b> Y, and is collected by the cleaning unit 310.

  At this time, a positive voltage is applied to the primary transfer roller 206Y, and the toner image is primarily transferred from the photosensitive drum 301Y to the intermediate transfer belt 205 in the primary transfer portion N1Y. That is, when image formation is continuously performed on a plurality of transfer materials P, in the primary transfer portion N1Y, the primary transfer of the toner image and the toner charged to the positive polarity by the charging brush 219 are simultaneously performed. Yes. Accordingly, the cleaning unit 310Y of the photosensitive drum 301Y arranged at the most upstream in the moving direction of the intermediate transfer belt 205 contains more toner than the other cleaning units 310.

  FIG. 9 is a schematic diagram illustrating toner collection when the controller 202 stops the image forming operation in this embodiment. As shown in FIG. 9, in this embodiment, when the image forming operation is stopped, a negative voltage is applied to the primary transfer rollers 206M to 206K, and a positive voltage is applied to the primary transfer roller 206Y. To do. Thereby, the toner carried on the photosensitive drum 301Y can be primarily transferred to the intermediate transfer belt 205, and the amount of toner collected by the cleaning unit 310Y can be suppressed, and the puncture of the cleaning unit 310Y can be suppressed.

  The toner carried on the photosensitive drum 301Y moves from the intermediate transfer belt 205 to the photosensitive drum 301M by applying a negative voltage to the primary transfer rollers 206M to 206K, and is collected by the cleaning unit 310M. . Also in the present embodiment, the same control as that in the first embodiment is performed in the image forming units SM to SK. That is, the toner primarily transferred to the intermediate transfer belt 205 is collected by the cleaning unit 310 after moving to the photosensitive drum 301 on the downstream side. The toner carried on the photosensitive drum 301 passes through the primary transfer portion N1 without being primary transferred to the intermediate transfer belt 205, and is collected by the cleaning unit 310 of the photosensitive drum 301.

  As described above, according to the configuration of the present exemplary embodiment, not only the same effects as those of the first exemplary embodiment can be obtained, but also the cleaning unit 310 for the photosensitive drum 301 </ b> Y disposed at the most upstream in the moving direction of the intermediate transfer belt 205. It is possible to suppress the saturation of the capacity.

202 Controller 205 Intermediate transfer belt 206 Primary transfer roller 301 Photosensitive drum 310 Cleaning means

Claims (13)

A first image carrier that carries a toner image; an intermediate transfer member that is in contact with the first image carrier and to which a toner image carried on the first image carrier is primarily transferred; and A first contact member provided corresponding to one image carrier and contacting an inner peripheral surface of the intermediate transfer member; a first power source for applying a voltage to the first contact member; A first collecting means for contacting the image carrier and collecting the toner remaining on the first image carrier;
With respect to the moving direction of the intermediate transfer member, the intermediate transfer member is disposed downstream of the first image carrier and upstream of a secondary transfer portion that secondarily transfers toner from the intermediate transfer member to a transfer material. A voltage is applied to the second image bearing member, a second contact member provided corresponding to the second image bearing member and contacting the inner peripheral surface of the intermediate transfer member, and the second contact member. A second power supply that performs contact with the second image carrier and a second collecting unit that collects toner remaining on the second image carrier, and a control that controls start and stop of an image forming operation. And an image forming apparatus comprising:
By applying a voltage of a predetermined polarity from the first power source to the first contact member, the control means in a state where a toner image is primarily transferred from the first image carrier to the intermediate transfer member. If the image forming operation is stopped,
In order to collect the toner image carried on the first image carrier in contact with the intermediate transfer member by the first collecting means, the first power source applies the first contact member to the first contact member. A voltage having a polarity opposite to a predetermined polarity is applied, and the toner image primarily transferred from the first image carrier to the intermediate transfer member is moved from the intermediate transfer member to the second image carrier to An image forming apparatus, wherein a voltage of the reverse polarity is applied from the second power source to the second contact member for recovery by a second recovery means. Before the leading edge of the toner image primarily transferred from the first image carrier to the intermediate transfer member reaches a position where the second image carrier and the intermediate transfer member abut, When the image forming operation is stopped,
In order to collect the toner image carried on the first image carrier in contact with the intermediate transfer member by the first collecting means, the first power source applies the first contact member to the first contact member. A voltage having a polarity opposite to a predetermined polarity is applied, and the toner image primarily transferred from the first image carrier to the intermediate transfer member is moved from the intermediate transfer member to the second image carrier to 2. The image forming apparatus according to claim 1, wherein the reverse polarity voltage is applied to the second contact member from the second power source for recovery by the second recovery unit. A first image carrier that carries a toner image; an intermediate transfer member that is in contact with the first image carrier and to which a toner image carried on the first image carrier is primarily transferred; and A first contact member provided corresponding to one image carrier and contacting an inner peripheral surface of the intermediate transfer member; a first power source for applying a voltage to the first contact member; A first collecting means for contacting the image carrier and collecting the toner remaining on the first image carrier;
With respect to the moving direction of the intermediate transfer member, the intermediate transfer member is disposed downstream of the first image carrier and upstream of a secondary transfer portion that secondarily transfers toner from the intermediate transfer member to a transfer material. A voltage is applied to the second image bearing member, a second contact member provided corresponding to the second image bearing member and contacting the inner peripheral surface of the intermediate transfer member, and the second contact member. A second power supply that performs contact with the second image carrier and a second collecting unit that collects toner remaining on the second image carrier, and a control that controls start and stop of an image forming operation. And an image forming apparatus comprising:
A state in which a toner image is primarily transferred from the first image carrier to the intermediate transfer member by applying a voltage of a predetermined polarity from the first power source to the first contact member; and Before the leading edge of the toner image primarily transferred from the first image carrier to the intermediate transfer member reaches a position where the second image carrier and the intermediate transfer member contact each other. If the image forming operation is stopped,
In order to move the toner image primarily transferred from the first image carrier to the intermediate transfer member to the second image carrier from the intermediate transfer member and collect the toner image by the second collecting means, An image forming apparatus, wherein a voltage having a polarity opposite to the predetermined polarity is applied from a second power source to the second contact member. In the case of continuously forming the first image and the second image formed subsequent to the first image,
Corresponding to the first image is the position where the second image carrier and the intermediate transfer member abut when the transfer material to which the toner image corresponding to the second image is secondarily transferred is not conveyed. The image forming operation is stopped by the control means after the trailing edge of the toner image to be passed,
In order to move the toner image primarily transferred from the first image carrier to the intermediate transfer member to the second image carrier from the intermediate transfer member and collect the toner image by the second collecting means, The image forming apparatus according to claim 3, wherein a voltage having a polarity opposite to the predetermined polarity is applied from a second power source to the second contact member.   After the control unit stops the image forming operation, the toner carried on the first image carrier is applied by applying a voltage of the predetermined polarity from the first power source to the first contact member. The toner moved from the first image carrier to the intermediate transfer member, and the toner moved to the intermediate transfer member by applying the reverse polarity voltage to the second contact member from the second power source is transferred to the intermediate transfer member. The image forming apparatus according to claim 4, wherein the image forming apparatus is moved from the intermediate transfer member to the second image carrier and is collected by the second collecting unit.   A distance between the feeding member and the secondary transfer unit, the feeding member feeding the transfer material toward the secondary transfer unit; and an exposure unit that exposes the first image carrier. The distance from the position where exposure is started by the exposure unit in the first image carrier to the secondary transfer unit is longer than the first transfer unit. Image forming apparatus.   The length of the intermediate transfer body from the position where the first image carrier and the intermediate transfer body abut to the secondary transfer section is longer than the distance of transferring the transfer material from the feeding member to the secondary transfer section. The image forming apparatus according to claim 6, wherein the length is long.   The conveyance speed of the transfer material conveyed from the feeding member to the secondary transfer unit, the rotation speed of the first image carrier and the second image carrier, and the movement speed of the intermediate transfer member are: The image forming apparatus according to claim 6, wherein each of the image forming apparatuses has a substantially constant speed.   A plurality of image carriers in the moving direction of the intermediate transfer member, and the second image carrier is the most downstream of the plurality of image carriers in the moving direction of the intermediate transfer member, and The image forming apparatus according to claim 1, wherein the image forming apparatus is disposed upstream of the secondary transfer unit.   The first image carrier is disposed downstream of the secondary transfer unit in the moving direction of the intermediate transfer member and is disposed at the most upstream of the plurality of image carriers. The image forming apparatus according to claim 9.   With respect to the moving direction of the intermediate transfer member, the secondary transfer unit is disposed downstream of the secondary transfer unit and upstream of the first image carrier, and is in contact with the intermediate transfer member. Charging means for charging the toner having passed through the section to the predetermined polarity, and applying the voltage of the predetermined polarity from the first power source to the first contact member, whereby the toner is charged to the predetermined polarity by the charging means. 11. The image forming apparatus according to claim 1, wherein the toner is collected by the first collecting unit after being moved from the intermediate transfer member to the first image carrier. .   With respect to the moving direction of the intermediate transfer member, the secondary transfer unit is disposed downstream of the secondary transfer unit and upstream of the first image carrier, and is in contact with the intermediate transfer member. The image forming apparatus according to claim 1, further comprising a blade member that collects toner that has passed through the section.   The first collecting means includes a blade member that contacts the first image carrier and collects toner remaining on the image carrier to the collecting means, and the second collecting means includes the first collecting means. 13. The image forming apparatus according to claim 1, further comprising a blade member that abuts against the second image carrier and collects toner remaining on the image carrier by the collecting unit.

Images