JP5309493B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain a stable image quality over a long period, while preventing the image quality from being deteriorated caused by the discharge product by removing a discharge product deposited onto a surface of an image holding body with a simple constitution. <P>SOLUTION: This image forming apparatus is provided with the rotatable image conveying body 2 arranged opposedly to the plurality of image holding bodies 1, and for conveying a toner image on the image holding bodies 1 directly or via a recording material S, a speed variable means 3 capable of varying independently speeds of the plurality of image holding bodies 1 in one unit or units of the number smaller than the number of the image holding bodies 1, a judging means 4 for judging the propriety of contribution to image formation out of the plurality of image holding bodies 1, and a speed control means 5 having a first speed mode for setting the speed of the image holding body 1 contributing to the image formation, as a first speed, and a second speed mode for setting the speed of the image holding body 1 not contributing to the image formation, as a second speed with a speed difference getting large with respect to the image conveying body 2, compared with the first speed, and for controlling the speed variable means 3 to select any of the speed modes in respective image holding bodies 1, based on a judged result by the judging means 4. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus.

Conventionally, the surface of a photoreceptor used in an electrophotographic image forming apparatus such as a copying machine or a printer is discharged by, for example, a charging electric field for charging the photoreceptor, resulting in active substances such as ozone and nitrogen oxides and The discharge products such as those reaction products come to adhere.
If such a discharge product adheres to the surface of the photoconductor, the surface of the photoconductor will not be properly charged. In particular, if the discharge product absorbs moisture, the resistance will be lowered at that site, and image formation (image creation) will occur. Image defects such as image flow and white spots occur.

  As a method for removing the discharge product on the surface of the photoconductor, for example, an adsorption member that adsorbs the discharge product is provided facing the photoconductor, and a relative speed difference is set between the adsorption member and the photoconductor. Thus, a method is disclosed in which the discharge product on the photosensitive member is peeled off to be adsorbed (see Patent Document 1). Further, a method in which the discharge product on the photosensitive member is removed by increasing the speed of the rotating brush provided facing the photosensitive member (see Patent Document 2), or between the photosensitive member and the intermediate transfer belt. In order to increase the frictional force between them, a method is also known in which the intermediate transfer belt is pressed against the photosensitive member side via a transfer member to remove discharge products on the photosensitive member (Patent Document 3). reference).

  On the other hand, there is also known a method in which a polishing portion is provided across a width direction in a part of the conveyance direction of the intermediate transfer belt, and this polishing portion comes into contact with the photoconductor to remove deposits on the photoconductor. (See Patent Document 4). In addition, a relative speed difference is provided between the photosensitive member and the transfer belt during non-transfer operation so that the deposit on the photosensitive member is removed by sliding the transfer belt (recording material conveying belt) against the photosensitive member. There is also a known method (see Patent Document 5). Furthermore, for the purpose of reducing the wear of the photoconductor while suppressing the occurrence of transfer failure, the photoconductor and the intermediate transfer belt have speed modes that are substantially the same as the speed modes that are different from each other, A system is also disclosed in which the former is performed when the image region passes through the opposite part and the latter is performed when the non-image region passes (see Patent Document 6).

JP 2002-149024 A (Embodiment 1, FIG. 1) Japanese Patent Laying-Open No. 2005-266448 ([0039], FIG. 3) Japanese Patent Laying-Open No. 2005-266353 ([0092], FIG. 11) JP 2004-117463 A (Embodiment of the Invention, FIG. 2) Japanese Patent Laid-Open No. 1-222579 (page 3, lower right column, FIG. 1) JP 2006-189614 A (Claim 4, FIGS. 3 to 5)

  The technical problem of the present invention is that image formation capable of maintaining stable image quality over a long period of time while removing the discharge products adhering to the surface of the image carrier with a simple configuration and preventing image quality deterioration caused by the discharge products. To provide an apparatus.

According to a first aspect of the present invention, there are provided a plurality of rotatable image holders that are charged with discharge and that form and hold toner images on the surface thereof, and are arranged in contact with the plurality of image holders so as to face each other. A rotatable image carrier that conveys a toner image on the image carrier directly or via a recording material, and the speed of the plurality of image carriers can be varied independently by one or a few units less than the number of image carriers. Possible speed variable means, judgment means for judging whether or not each of the plurality of image holding bodies contributes to image formation, and at least humidity information around the image holding body when performing image forming processing Environmental condition detection means for detecting environmental conditions including the first speed mode for setting the speed of the image carrier that contributes to image formation to the first speed and the speed of the image carrier that does not contribute to image formation to the first speed the speed of the image carrier by slower than It has a second speed mode for setting a second speed which is increased, in carrying out the imaging process, based on the determination result by the determination unit, to have been an image carrier and image formation determined to contribute to the image forming and a speed control means for controlling the variable speed means such that the first speed mode or the second speed mode cut with been image carrier determines that do not contribute is selected, the speed control means is created upon selecting the second speed mode to have been image carrier determines that do not contribute to the image, when the environmental conditions sensed environmental conditions at the detection means is intended to increase the moisture absorption of the electric discharge product, otherwise Compared with the case of the above, either the speed difference due to the second speed in the second speed mode is set larger or the duration of the second speed mode is set longer or selectively or in combination. An image forming apparatus.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the speed control means can select either the first speed mode or the second speed mode for each image carrier in the same time zone. An image forming apparatus.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the speed control means is configured so that the second speed of the image carrier for which the second speed mode is selected is slower than the speed of the image carrier. An image forming apparatus that controls the speed varying unit.
According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, the toner is further supplied to the image carrier for which the second speed mode is selected, and between the image carrier and the image carrier. An image forming apparatus includes a toner supply control unit that interposes toner.
According to a fifth aspect of the present invention, in the image forming apparatus according to the first aspect, when the speed control unit switches and selects the first speed mode to the second speed mode, the image carrier selected in the first speed mode. The image forming apparatus performs switching from the first speed mode to the second speed mode for the image carrier after the transfer of the upper toner image.

According to a sixth aspect of the present invention, in the image forming apparatus according to the first aspect, a history determination unit that determines a use history of the image holding member, and an image holding during charging processing based on a determination result by the history determination unit. comprising a discharge degree of influence determining means for determining the degree of influence due to the discharge of the body, wherein the speed control means, when has been discharged impact determined by the discharge impact judgment means is high, otherwise Compared with the second speed mode, the image forming apparatus is configured to set a large speed difference due to the second speed .
According to a seventh aspect of the present invention, in the image forming apparatus according to the first aspect, a history determination unit that determines a use history of the image holding member, and an image holding during charging processing based on a determination result by the history determination unit. comprising a discharge degree of influence determining means for determining the degree of influence due to the discharge of the body, wherein the speed control means, when has been discharged impact determined by the discharge impact judgment means is high, otherwise In comparison, the image forming apparatus sets the duration of the second speed mode longer .

According to an eighth aspect of the present invention, in the image forming apparatus according to the first aspect, a history determination unit that determines a use history of the image carrier, and an image holding during charging processing based on a determination result by the history determination unit. Discharge influence degree judging means for judging the influence degree due to the discharge to the body, and provided on a different surface side of the image carrier from the image carrier, and the pressure contact force can be varied to the image carrier via the image carrier. The pressure contact force varying means to be applied and the pressure contact with respect to the image carrier for which the second speed mode is selected when the discharge influence degree determined by the discharge influence degree judgment means is high compared to other cases. a pressure control means for controlling the pressing force varying means such that a force is large, an image forming apparatus comprising a.
The invention according to claim 9, in the image forming apparatus according to claim 1, further a pressing force to the image carrier via the provided and the image carrier to the image carrier different side of the image carrier When the environmental condition detected by the variable contact pressure variable means and the environmental condition detection means enhances the moisture absorption of the discharge product, the second speed mode is compared to the other cases. a pressure control means for controlling the pressing force varying means so that the pressure contact force to selected the image carrier is increased, an image forming apparatus comprising a.
According to a tenth aspect of the present invention, in the image forming apparatus according to the second aspect, the difference in speed between the image carrier and the image carrier in the second speed mode when the first speed mode coexists is ΔVa, and all image carriers are provided. Is the speed difference between the image carrier in the second speed mode and the image carrier during the cycle up period before the start of the image forming operation, and ΔVb, and all the image carriers are in the cycle down period after the completion of the image forming operation. the speed difference between the image carrier and the image carrier of the two-speed mode when the [Delta] Vc, the speed control means, the speed of the image carrier is .DELTA.Va <said speed changing means so as to satisfy the relation .DELTA.Vb ≦ [Delta] Vc The image forming apparatus for controlling the image.

According to the first aspect of the present invention, the discharge product adhering to the surface of the image carrier is removed with a simple configuration, and image quality deterioration caused by the discharge product is prevented, and stable image quality is maintained over a long period of time. be able to.
In particular, according to the present invention, when the image forming process is performed, it is possible to efficiently remove discharge products according to environmental conditions for an image carrier that does not contribute to image forming .
According to the second aspect of the present invention, the first speed mode and the second speed mode can be selected in parallel, and the deposits on the image holding member can be efficiently removed.
According to the third aspect of the present invention, the speed of the image carrier is lower than that of the image carrier as compared with the case without this configuration, so that the image with respect to the image carrier is not changed without giving a speed fluctuation to the image carrier. It becomes possible to further increase the sliding force ( sliding frictional force) of the carrier, and to improve the discharge product removal performance on the surface of the image carrier.
According to the fourth aspect of the present invention, as compared to the case without this configuration, the toner is supplied to increase the rubbing force on the surface of the image carrier and increase the polishing effect. The discharge product can be removed more satisfactorily.
According to the fifth aspect of the present invention, it is possible to change the speed of the image carrier that performs the second speed mode at an early stage, and to improve the discharge product removal efficiency, as compared with the apparatus that does not have this configuration. it can.

According to the invention which concerns on Claim 6 or 7 , compared with what does not have this structure, the removal of the discharge product according to a use log | history is attained efficiently .
According to the invention which concerns on Claim 8 , compared with what does not have this structure, the removal of the discharge product more efficiently according to a use history is attained.
According to the invention which concerns on Claim 9 , compared with what does not have this structure, the removal of the discharge product more efficiently according to environmental conditions is attained.
According to the tenth aspect of the present invention, the discharge effect on the image carrier can be efficiently removed at an early stage after use by increasing the cleaning effect during cycle down.

First, an outline of an embodiment model to which the present invention is applied will be described.
Outline of Embodiment Model FIG. 1 shows an outline of an image forming apparatus according to an embodiment model embodying the present invention. In the figure, the image forming apparatus has a plurality of rotatable image holders 1 that are charged with discharge and form and hold toner images on the surface (in this example, the number is four, but this quantity is not limited). A rotatable image carrier 2 that is disposed in contact with the plurality of image carriers 1 and conveys a toner image on the image carrier 1 directly or via the recording material S, and a plurality of image carriers. a variably speed changing means 3 independently 1 speed one or a small number units than the image carrier number, carrying out the image forming process, contribute to the image formation for each of the plurality of each of the image carrier 1 The first speed mode for setting the speed of the image carrier 1 that contributes to image formation to the first speed and the speed of the image carrier 1 that does not contribute to image creation. the speed difference between the image carrier 2 increases by slower than It has a second speed mode to set the speed, carrying out the image forming process, determining that based on the determination result by the determination means 4, do not contribute to been the image carrier 1 and the imaging determined to contribute to the image forming A speed control means 5 is provided for controlling the speed variable means 3 so that the first speed mode or the second speed mode is selected by being separated from the image holding body 1 .

  Here, the number of the image carriers 1 is not particularly limited. For example, four image carriers 1 are usually used to form a color image. In addition, “the speed of the plurality of image carriers 1 is one or a few units smaller than the number of image carriers” means that the image carriers 1 may be independent from each other, for example, an image for K color The speed setting may be performed independently for each of the two groups of the body 1 and the color-color image holding body 1. Further, “does not contribute to image formation” means that, for example, only one set of image carriers 1 contributes to image formation and the other image carriers 1 do not contribute to image formation. All image holders 1 may be in a condition that contributes to image formation, or may not be in a condition that contributes to image formation, that is, even if any image carrier 1 is in the process of image formation, All the image carriers 1 may be, for example, before the start of the image forming operation (cycle up period) or after the end of the image forming operation (cycle down period).

The reason why “the charging process accompanied by the discharge is performed” is that the object of the present invention uses, for example, a method in which a discharge occurs when the image carrier 1 is charged, that is, a corona discharge by a corona charger. Or a method in which partial discharge occurs due to contact charging by a charging roll or the like, and there is a possibility that a discharge product is generated on the image carrier 1 by such discharge. It means that there is.
The image carrier 2 may be an intermediate transfer member that directly holds and conveys the toner image on the image carrier 1, or the recording material S is applied to the toner image on the image carrier 1. However, from the viewpoint of improving the degree of freedom in selecting the image carrier 1 that performs the second speed mode, an intermediate transfer member may be used as the image carrier 2. preferable.
Further, from the viewpoint of ensuring the speed stability of the image carrier 2 with respect to the speed change of the image carrier 1, the speed control means 5 is configured such that the second speed of the image carrier 1 for which the second speed mode is selected is the image. It is preferable to control the speed variable means 3 so as to be slower than the speed of the carrier 2.

From the viewpoint of efficiently removing the discharge products on the image carrier 1, the speed control unit 5 uses the same one of the first speed mode and the second speed mode for each image carrier 1. It is preferable that it can be selected in a time zone.
Further, from the viewpoint of quickly changing the speed of the image carrier 1 for which the second speed mode is selected, the speed control unit 5 switches the first speed mode from the first speed mode to the second speed mode. It is preferable that the image carrier 1 is switched from the first speed mode to the second speed mode after the transfer of the toner image on the image carrier 1 selected for the mode. Here, in the case of “switching to the second speed mode after completion of transfer”, it is preferable that the time until switching is short, and it is better to perform immediately after completion of transfer. After the speed control means 5 recognizes the completion of the transfer of the image carrier 1, it is determined including the time elapsed until the speed variable means 3 starts to be controlled so as to change the speed of the target image carrier 1. .

Here, the effect | action with respect to the speed difference of the image holding body 1 and the image carrier 2, and the removal effect of a discharge product is demonstrated. FIGS. 2A to 2C schematically show the operation. As shown in FIG. 2A, the speed of the image carrier 1 is _VA, and the speed of the image carrier 2 is V _B. The speed difference ΔV between the two is obtained by ΔV = | V _B −V _A |. If the discharge product adheres on the image carrier 1 and the speed difference ΔV is close to zero, the speed of the image carrier 1 and the image carrier 2 with respect to the discharge product is as shown in FIG. Because of the approximation, the mechanical frictional force from the image carrier 2 is not effectively applied to the discharge product, and it becomes difficult to remove the discharge product. On the other hand, when the speed difference ΔV is increased, for example, when the speed of the image carrier 2 is larger than that of the image carrier 1, the image carrier is conveyed to the discharge product on the image carrier 1 as shown in FIG. A pulling force is exerted on the downstream side on the body 2 side. As a result, a shear stress (displacement stress) is exerted on the discharge product itself in the direction of the arrow between the image carrier 1 side and the image carrier 2 side. ) Comes to work. For this reason, the discharge product itself is transferred from the image carrier 1 side to the image carrier 2 side, or the adhesion between the image carrier 1 and the discharge product is reduced, and the discharge generation on the image carrier 1 is generated. Things can be easily removed.

  Then, from the viewpoint of improving the discharge product removal performance in the second speed mode, the toner is further supplied to the image carrier 1 for which the second speed mode is selected, and the image carrier 1 and the image carrier 2 It is preferable to include a toner supply control means for interposing the toner between the toner and the toner supplied to the surface of the image carrier 1, and the rubbing force is increased, so that the discharge product removal performance on the surface of the image carrier 1 is further improved. It becomes like this.

Further, from the viewpoint of efficiently removing discharge products from the image carrier 1, the history determination unit 6 that determines the usage history of the image carrier 1 and the determination result by the history determination unit 6 are further used. And a discharge influence degree determination means 7 for determining the influence degree of the discharge on the image carrier 1 during the charging process. The speed control means 5 has a high discharge influence degree determined by the discharge influence degree determination means 7. It is preferable to set a larger speed difference due to the second speed in the second speed mode. For example, the speed difference may be changed by changing the value of the second speed in accordance with the usage history such as the elapsed time of the image carrier 1, the number of prints, and past image forming conditions.
On the other hand, from the viewpoint of efficiently removing the discharge products with respect to the environmental conditions, an environmental condition detecting means 8 for detecting environmental conditions including at least humidity information around the image carrier 1 is further provided. When the environmental condition detected by the environmental condition detection means 8 enhances the moisture absorption of the discharge product, the speed control means 5 is a speed based on the second speed in the second speed mode as compared with other cases. It is preferable to set the difference large.

Further, efficient discharge product removal may be performed as follows. That is, the history determination unit 6 that determines the usage history of the image carrier 1 and the discharge influence that determines the degree of influence due to the discharge to the image carrier 1 during the charging process based on the determination result by the history determination unit 6. Degree control means 7, and the speed control means 5 sets the duration of the second speed mode longer when the discharge influence degree determined by the discharge influence degree judgment means 7 is higher than in other cases. Or an environmental condition detecting means 8 for detecting an environmental condition including at least humidity information around the image carrier 1, and the speed control means 5 is detected by the environmental condition detecting means 8. When the environmental condition is to increase the moisture absorption of the discharge product, the duration of the second speed mode may be set longer than in other cases .

  From another point of view, efficient discharge product removal is performed as follows. That is, the history determination unit 6 that determines the usage history of the image carrier 1 and the discharge influence that determines the degree of influence due to the discharge to the image carrier 1 during the charging process based on the determination result by the history determination unit 6. Degree judging means 7 and pressure contact force varying means 9 provided on a different surface side of the image carrier 2 from the image carrier 1 and applying a pressure contact force to the image carrier 1 through the image carrier 2 variably. The pressure contact control for controlling the pressure contact force varying means 9 so that the pressure contact force increases with respect to the image carrier 1 for which the second speed mode is selected as the discharge influence degree judged by the discharge influence degree judgment means 7 is higher. Or an environmental condition detection means 8 for detecting an environmental condition around the image carrier 1 and a surface of the image carrier 2 that is different from the image carrier 1. In addition, a pressure contact force can be applied to the image carrier 1 through the image carrier 2. For the image carrier 1 in which the second speed mode is selected as the environmental condition detected by the pressing force varying means 9 and the environmental condition detecting means 8 that can be applied increases the moisture absorption of the discharge product. What is necessary is just to provide the press-contact control means which controls the press-contact force variable means 9 so that a press-contact force may become large.

  From the viewpoint of effectively preventing the discharge product from adhering to the image carrier 1, the speed difference between the image carrier 1 and the image carrier 2 in the second speed mode when the first speed mode coexists is determined. ΔVa, and the speed difference between the image carrier 1 and the image carrier 2 in the second speed mode during the cycle-up period before all image carriers 1 start the image forming operation is ΔVb, and all the image carriers 1 are When the speed difference between the image carrier 1 and the image carrier 2 in the second speed mode during the cycle down period after the end of the image forming operation is ΔVc, the speed controller 5 determines that the speed of the image carrier 1 is ΔVa. It is preferable to control the speed variable means 3 so as to satisfy the relationship <ΔVb ≦ ΔVc. In this case, by increasing the speed difference during the cycle-up period and the cycle-down period, the discharge product of the image carrier 1 can be effectively removed without considering the influence on the image formation. At the same time, in particular, the discharge product on the image carrier 1 can be more effectively removed just after the discharge product is deposited by use during the cycle down period.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Embodiment 1
FIG. 3 shows a first embodiment of an image forming apparatus to which the above-described embodiment model is applied. In the figure, the image forming apparatus of the present embodiment is a so-called tandem type color image forming apparatus, and each color component (for example, yellow (Y), magenta (M)) is formed in the apparatus housing 10 by, for example, electrophotography. , Cyan (C) and black (K) toner image detachable bodies (hereinafter referred to as process cartridges) 20 (20a to 20d) are arranged in parallel facing the intermediate transfer belt 40. .

  On the other hand, the intermediate transfer belt 40 is stretched around three tension rolls 41 to 43, and is circulated and rotated in the direction of the arrow in the figure using the tension roll 42 as a drive roll. A belt cleaning member 44 that cleans residual toner and the like on the intermediate transfer belt 40 is provided at a position facing the stretching roll 42 so as to be able to contact and separate from the intermediate transfer belt 40.

In the present embodiment, a recording material supply unit 11 that can supply the recording material S to the lower side of the apparatus housing 10 is provided so as to be freely drawn out from the apparatus housing 10. In addition, a pickup roll 12 for feeding the recording material S from the recording material supply unit 11 and a pickup roll provided in a pair on the downstream side of the pickup roll 12 are provided in the vicinity of the recording material supply unit 11. 12 is provided with a separating mechanism 13 (13a, 13b) for conveying the recording material S conveyed from 12 to a predetermined recording material conveyance path (path indicated by a two-dot chain line in the figure). ing.
Further, a registration roll 15 is provided in the recording material conveyance path on the downstream side of the whirling mechanism 13 so as to temporarily position the recording material S that has been wound and conveyed and then convey the recording material S to the downstream side at a predetermined timing. Further, on the downstream side thereof, a secondary transfer roll for collectively transferring onto the recording material S a multiple toner image in which each color toner image formed by each color process cartridge 20 is multiplexed on the intermediate transfer belt 40, and the like. The secondary transfer device 16 is provided with a stretching roll 41 as a backup roll. A secondary transfer bias for transferring the multiple toner images on the intermediate transfer belt 40 to the recording material S side is applied between the secondary transfer device 16 and the stretching roll 41 by a bias power source (not shown). It has become so.

  Further, on the downstream side of the secondary transfer device 16, a fixing device 17 for fixing the multiple toner images collectively transferred onto the recording material S is provided. The fixing device 17 includes, for example, a heating roll 17a and a pressure roll 17b. The transfer toner image is sufficiently heated and pressed. At the end of the apparatus housing 10 on the downstream side of the fixing device 17, a discharge roll 18 that discharges the recording material S that has been fixed to a recording material accommodation portion 19 that is configured as a part of the apparatus housing 10. Is provided.

Further, a developer cartridge 48 (48a to 48d) for supplying the developer of each color to the process cartridge 20 of each color is provided above the apparatus housing 10, and in this example, a developer cartridge of K color is provided. 48 d has a larger capacity than the other developer cartridges 48. Note that the developer used in the present embodiment is a two-component developer including toner and carrier, and the developer discharged from the process cartridge 20 includes a carrier that has deteriorated. The developer in 48 is a component containing toner and carrier.
In addition, a control device 60 is provided below the apparatus housing 10 so as to perform various conveyance controls and image forming controls of the recording material S and to control the rotational drive of the process cartridge 20 and the intermediate transfer belt 40. Yes.

The process cartridge 20 in the present embodiment is as shown in FIG. 4 (in FIG. 4, a Y-color process cartridge 20a is representatively shown). In the process cartridge 20, a photosensitive member 22 having a photosensitive layer such as an organic photosensitive member is disposed facing the opening of the cartridge case 21 at a position facing the intermediate transfer belt 40.
Around the photosensitive member 22, a charger 23 for charging the surface of the photosensitive member 22 (in this example, a charging roll is used), an exposure including an LED array for forming an electrostatic latent image on the charged photosensitive member 22, and the like. A vessel 24 is provided. Further, a developing roll 31 for developing and developing the electrostatic latent image on the photoconductor 22 and a position opposite to the photoconductor 22 across the intermediate transfer belt 40 are provided, and the toner image on the photoconductor 22 is intermediated. A primary transfer device 25 such as a transfer roll for transferring onto the transfer belt 40 is provided. Further, a photosensitive member cleaning member 26 for cleaning residual toner on the photosensitive member 22 and a charger cleaning member 27 for cleaning dirt on the charger 23 are also provided at predetermined positions. In the present embodiment, a transfer bias is applied between the photosensitive member 22 and the primary transfer unit 25 from a bias power source (not shown), and the toner image on the photosensitive member 22 is effective on the intermediate transfer belt 40 side. It is supposed to be transferred to.

The developing roll 31 of the present embodiment is constituted by a so-called mag roll that includes a nonmagnetic developing sleeve that can rotate on the surface and includes a magnet body in which a plurality of magnetic poles are fixedly arranged inside the developing sleeve. Therefore, the developer on the developing roller 31 is developed by a developing bias (not shown) applied between the photosensitive member 22 and the developing roller 31 in the developing region which is a region facing the photosensitive member 22. The toner inside the toner flies from the developing roll 31 side to the photosensitive member 22 side for development.
A pair of stirring and conveying members 33 and 34 for stirring and charging the developer and supplying the developer to the developing roll 31 are provided behind the developing roll 31. Further, on the upstream side of the developing area of the developing roll 31, there is provided a layer thickness regulating member 32 that is disposed with a predetermined gap from the developing roll 31 and regulates the layer thickness of the developer on the developing roll 31. Yes.

  Further, in the present embodiment, a supply port 35 for supplying the developer to the stirring and conveying member 34 is provided further behind the stirring and conveying member 34 on the rear side of the developing roll 31. For example, the developer from the developer cartridge 48 is dispensed. Furthermore, in the present embodiment, a part of the agitating / conveying member 34 is provided with a mechanism for collecting and discharging excess developer, and the developer overflowed from a predetermined portion is discharged (not shown). The cartridge is discharged from the process cartridge 20 to the outside. Therefore, the carrier deteriorated in the process cartridge 20 can be effectively discharged, and the development characteristics can be stabilized for a long time.

Next, the drive system in the present embodiment will be described.
As shown in FIG. 5, in the present embodiment, among the four process cartridges 20, the K-color photosensitive member 22d of the K-color process cartridge 20d (here, the photosensitive member corresponding to the process cartridge 20 of each color is identified. The other three-color photoconductors 22a to 22c are configured to rotate by being driven by independent drive motors M1 and M2, respectively, and to perform intermediate transfer. The tension roll 42 that is a drive roll of the belt 40 is driven by a drive motor M3 so that the intermediate transfer belt 40 rotates. These drive motors M <b> 1 to M <b> 3 are controlled to be turned ON / OFF and controlled by the control device 60. In addition, an image signal is input to the control device 60, and various image forming controls are performed based on the image signal, and the speed control of each of the photoconductors 22a to 22d and the speed control of the intermediate transfer belt 40 are performed. .

  In particular, in the present embodiment, the respective photoconductors 22a to 22d and the intermediate transfer belt 40 are controlled by the control device 60 so as to change the speed as shown in FIG. That is, the Y color photoconductor 22a, the M color photoconductor 22b, and the C color photoconductor 22c perform the same speed change, and the first speed V1 is selected as the first speed V1 when contributing to image formation. Switching between the mode and the second speed mode in which the second speed V2 decelerated from the first speed V1 is selected is performed. Similarly, the K-color photoconductor 22d is switched between the first speed mode of the first speed V1 and the second speed mode of the second speed V2. On the other hand, the intermediate transfer belt 40 is set to the same speed as the first speed V1 so that the speed difference from the photoconductor 22 becomes substantially zero in both the first speed mode and the second speed mode. At this time, the K-color photoconductor 22d and the other photoconductors 22a to 22c can be switched independently.

  Here, the number of the photoconductors 22 is four, and the driving of the K and other color photoconductors 22 is shown separately. However, the number of the photoconductors 22 is not limited to this, and the photoconductors 22 are also not limited thereto. You may make it provide a drive motor independently for every, and you may make it provide a drive motor with another combination. Furthermore, the order of colors is not limited to this arrangement order. In the first speed mode, a speed difference may be provided between the photoconductor 22 and the intermediate transfer belt 40. In this case, in the second speed mode, a larger speed difference may be provided. That's fine.

And in this Embodiment, control by the flow as shown in FIG. 7 is performed by the control apparatus 60. FIG.
First, the usage history of the image forming apparatus is confirmed, and from this usage history, the degree of influence of the discharge product formed on the photoconductor 22 is determined to determine whether the discharge product needs to be removed. (Steps S01 to S02). Here, if it is determined that removal is necessary, it is determined whether any of the Y, M, and C photoconductors 22a to 22c contributes to image formation (step S03). If these photoconductors 22a to 22c contribute to image formation, it is next determined whether or not the K color photoconductor 22d contributes to image formation (step S04). If it contributes to the image, the first speed mode is selected for all the photoconductors 22 (step S06). If the K-color photoconductor 22d does not contribute to image formation in step S04, the second speed mode is selected for the K-color photoconductor 22d, and the first speed is set for the other photoconductors 22. A mode is selected (step S07). Further, if the K-color photoconductor 22d contributes to image formation in step S05, the first speed mode is selected for the K-color photoconductor 22d and the second speed is set for the other photoconductors 22. A mode is selected (step S08). Furthermore, if the K-color photoconductor 22d does not contribute to image formation in this step, the second speed mode is selected for all the photoconductors 22 (step S09). If it is determined in step S02 that it is not necessary to remove the discharge product, the first speed mode is selected according to the image formation.

  Next, the operation of the image forming apparatus having such a configuration will be described with reference to FIGS. For example, when a full color image is formed, the recording material S supplied from the recording material supply unit 11 is transferred to the secondary transfer portion (secondary transfer device 16 and the tensioner) via the resist roll 15 by a signal from the control device 60. (Corresponding to the part facing the rack roll 41).

  On the other hand, in the process cartridge 20 (20a to 20d), the speed (rotational speed) of the four-color photoconductors 22 (22a to 22d) is substantially the same (in this example, the first speed V1) by a signal from the control device 60. Also, the speed of the intermediate transfer belt 40 is set to be approximately the same as the speed of the photosensitive member 22, and each rotates. Therefore, the four photoconductors 22a to 22d and the intermediate transfer belt 40 rotate in the first speed mode in which the speed difference at the contact portion is substantially zero. Under this first speed mode, the process cartridge 20 forms a toner image of each color according to the image signal, and is primarily transferred onto the intermediate transfer belt 40 in order from the Y color by the primary transfer unit 25. On the intermediate transfer belt 40 that has passed through the four process cartridges 20, a multiple toner image in which toner images of four colors are overlapped is obtained.

  Then, the multiple toner images on the intermediate transfer belt 40 are collectively transferred (secondary transfer) onto the recording material S at the secondary transfer portion. The recording material S on which the multiple toner images have been collectively transferred is discharged from the discharge roll 18 to the recording material storage portion 19 and stored after the multiple toner images are fixed by the fixing device 17.

In such an image forming process, since a high voltage is applied as a charging bias between the charging device 23 and the photosensitive member 22, discharge is particularly generated before and after the portion where the charging device 23 and the photosensitive member 22 are in contact with each other. It is easy to generate. Such discharge promotes generation of active substances such as ozone and nitrogen oxide, and discharge products such as these active substances and reaction products thereof adhere to the surface of the photoreceptor 22. In addition, when a corona charger is used as the charger 23, the adhesion of discharge products further increases.
When such a discharge product adheres to the surface of the photoconductor 22, the surface of the photoconductor is not properly charged. In particular, when the adhering discharge product absorbs moisture, the resistance is lowered at that portion, and image flow and white Image defects such as omission occur. Therefore, if the image formation is continued with the discharge product left as it is, it is directly affected by the discharge product adhering to the surface of the photoreceptor.

  For this reason, in this embodiment, for example, when the usage history such as the cumulative number of image formations is determined and the influence level due to the discharge is determined during the charging process based on the usage history, the influence level is determined to be high. Removes discharge products on the photosensitive member 22. Specifically, for example, when a monochrome image is formed, the discharge products are removed by appropriately cleaning the surfaces of the Y-color photoreceptor 22a, the M-color photoreceptor 22b, and the C-color photoreceptor 22c. I have to. That is, when a monochrome image is formed, the control device 60 selects the first speed mode because it contributes to the image formation for the K-color photoconductor 22d, and applies it to the other photoconductors 22a to 22c. On the other hand, it is determined that it does not contribute to image formation, and the second speed mode is selected.

  For example, when a full-color image is formed and a monochrome image is formed, the three-color photoconductors 22a to 22c do not contribute to image formation, and these three-color photoconductors 22a to 22c The first speed mode is switched to the second speed mode. Since the three color photoconductors 22a to 22c share the drive motor M2, the rotation speed changes at the same timing. That is, in the first speed mode, all the four photoconductors 22a to 22d rotate at substantially the same rotational speed, while the intermediate transfer belt 40 also rotates at substantially the same speed, thereby forming a monochrome image. In this case, the second speed mode is selected for the Y color photoreceptor 22a, the M color photoreceptor 22b, and the C color photoreceptor 22c, and the first speed in the first speed mode is changed to the second speed in the second speed mode. The speed is reduced, and the surface of the three-color photoconductor 22 is cleaned.

  Thus, by reducing the speed of the photoconductor 22, the speed difference between the photoconductor 22 and the intermediate transfer belt 40 acts clearly, and the rubbing force of the intermediate transfer belt 40 on the surface of the photoconductor is reduced. As a result, there is an effect of mechanically polishing the discharge product adhering to the surface of the photoconductor 22, and the discharge product adheres to the intermediate transfer belt 40 side or on the photoconductor 22. The adhesion strength is reduced. At this time, since the discharge product adhering to the intermediate transfer belt 40 is thinly spread, the image that is primarily transferred from the K-color photosensitive member 22d onto the intermediate transfer belt 40 is hardly affected, and a new There is no fear of image defects. The discharge product adhering to the intermediate transfer belt 40 is removed by the belt cleaning member 44 (see FIG. 3) after the toner image is collectively transferred (secondary transfer). On the other hand, the discharge product having reduced adhesion strength on the photoconductor 22 is removed from the photoconductor surface by the photoconductor cleaning member 26 (see FIG. 4).

  Even if it is assumed that the discharge product is also formed on the intermediate transfer belt 40, the discharge product on the intermediate transfer belt 40 is caused by the mutual rubbing action between the intermediate transfer belt 40 and the photosensitive member 22. Needless to say, the adhesion strength of the belt becomes lower and can be easily removed by the belt cleaning member 44.

  Further, in this embodiment, the speed of the photosensitive member 22 in the second speed mode is decelerated from the intermediate transfer belt 40, so that the load on the intermediate transfer belt 40 during image formation is reduced, and the intermediate transfer belt is reduced. 40 itself is not slackened, and the meandering and uneven transfer of the intermediate transfer belt 40 hardly occur. In addition, since the second speed mode can be performed during the imaging period, the discharge product can be efficiently removed. If a cleaning member that rotates so as to be in contact with the photosensitive member 22 is provided and a speed difference is provided between the photosensitive member 22 and the cleaning member, a dedicated drive mechanism that rotationally changes the cleaning member is required. In addition, if a speed difference is provided during image formation on the photoconductor 22, a slight speed change of the photoconductor 22 itself occurs, so-called banding (band-like density unevenness appearing in the halftone portion of the image), or the like. This leads to the occurrence of image defects.

  In the second speed mode, for example, when process black is used and K color is not used, it is possible to set only the K-color photosensitive member 22d to the second speed mode. In this case, after the three-color multiple toner image is formed on the intermediate transfer belt 40, it passes through the portion of the K-color photosensitive member 22d, but between the K-color photosensitive member 22d and the intermediate transfer belt 40. By applying a transfer bias (bias in the direction of attracting toner to the intermediate transfer belt 40 side), it is possible to prevent image distortion as well as the cleaning effect of the K-color photosensitive member 22d.

Further, such second speed mode may be performed not only during the image forming period, but also during the cycle up period before the start of the image forming operation or during the cycle down period after the completion of the image forming operation. Needless to say, none of the photoconductors 22 contributes to image formation during this period.
In such a case, the difference in speed between the photosensitive member 22 in which the second speed mode is selected and the intermediate transfer belt 40 when the first speed mode coexists is ΔVa, and the photosensitivity during the cycle-up period is set. If the speed difference between the photosensitive member 22 and the intermediate transfer belt 40 is ΔVb, and the speed difference between the photosensitive member 22 and the intermediate transfer belt 40 during the cycle down period is ΔVc, ΔVa <ΔVb ≦ ΔVc may be satisfied. According to this, the polishing effect can be further improved without affecting the image formation even if the speed difference during the cycle up period or the cycle down period when the image formation is not performed is increased. become. In particular, during the cycle down period, since the discharge product is generated immediately after image formation, the adhesion strength of the discharge product is small, and the timing is suitable before moisture absorption. Can be removed. The speed difference is preferably set within a range of about 0.3% to 10%, and if it is set to 2% or more, the rubbing effect becomes remarkable, but the cycle up is 2% or less during the image forming period. What is necessary is just to set so that it may become 2 to 10% as a standard during a period or a cycle down period.

Further, when switching from the first speed mode to the second speed mode, the toner image on the photoconductor 22 that is executing the first speed mode is transferred to the intermediate transfer belt 40 and then switched to the second speed mode. In this case, if switching is performed immediately after transfer, efficient cleaning becomes possible.
For example, in order to ensure transferability of the toner image from the photoconductor 22 to the intermediate transfer belt 40, a speed difference from the intermediate transfer belt 40 is provided with respect to the speed of the photoconductor 22 set in the first speed mode. In this case, the speed difference in the second speed mode may be made larger, and this also ensures the effect of removing the discharge products on the photoconductor 22 in the second speed mode. .

Further, as a modification of the present embodiment, the toner is supplied to the photosensitive member 22 set to the second speed mode, and the toner is interposed between the photosensitive member 22 and the intermediate transfer belt 40 that are rubbed to provide a polishing effect. It is also possible to increase the value. By controlling the toner 22 to intervene when the photosensitive member 22 and the intermediate transfer belt 40 are rubbed in this way, the toner itself can also serve as an abrasive and increase the polishing effect. Therefore, the discharge product can be more easily removed.
FIG. 8 shows an example. The surface of the photoconductor 22 is divided into an image area where a normal image is formed and a non-image area (non-image area). This is a schematic image arrangement. For example, an image area is arranged on the downstream side in the rotation direction of the photosensitive member 22 and a non-image area is arranged on the upstream side, and a toner band TB in which toner is formed in a substantially rectangular shape is provided in the non-image area. ing.

  When such a toner band TB is provided, the primary transfer bias for transferring the toner image from the photoconductor 22 to the intermediate transfer belt 40 is between the photoconductors 22a to 22c and the primary transfer device 25. When the non-image area passes through, a reverse bias is applied. Therefore, the toner in the toner band TB is not transferred to the intermediate transfer belt 40 side, and the photosensitive member 22, the intermediate transfer belt 40, and the like. The polishing effect can be increased and the discharge products can be easily removed.

  In this example, as shown in FIG. 8, only the toner band TB of each color is formed on the Y color photoreceptor 22a, the M color photoreceptor 22b, and the C color photoreceptor 22c that do not contribute to image formation, while the K color photoreceptor 22d. Then, in addition to the toner band TB, a toner image is formed also in the image forming area. When such a toner image from the photosensitive member 22 is primarily transferred onto the intermediate transfer belt 40, the toner band TB of each color is held as it is on the photosensitive member 22 side, and only the K color toner image is on the intermediate transfer belt 40 side. Will be transferred to. Further, such a toner band TB is cleaned and removed by the photosensitive member cleaning member 26, but the discharge product is also removed accordingly. By using the toner band TB, the lubricity between the photosensitive member 22 and the photosensitive member cleaning member 26 is ensured, and the cleaning characteristic of the photosensitive member cleaning member 26 can be continuously maintained for a long time. Become.

  FIG. 9 is a timing chart showing various operations when the second speed mode is performed immediately after the end of the secondary transfer. The second speed mode can also be performed in such a state. In the drawing, the photosensitive member 22 is shown as one, but after the secondary transfer (collective transfer), all the photosensitive members 22 are set to perform the second speed mode in such a state. That's fine.

That is, when the rotation operation of the photoconductor 22 and the intermediate transfer belt 40 is started, the photoconductor 22 is charged, exposed, and developed in order to form a toner image, and then the primary transfer is performed on the photoconductor 22. The toner image is transferred to the intermediate transfer belt 40. As a result, a multiplexed toner image is formed on the intermediate transfer belt 40, and this multiplexed toner image is secondarily transferred onto the recording material S. In the secondary transfer, in the first speed mode, an electric field in a direction for attracting the toner to the recording material S side is applied by the secondary transfer bias in accordance with the polarity of the toner. In this example, when negative polarity toner is used, a secondary transfer bias is applied so that a positive polarity is imparted to the secondary transfer device 16.
Immediately after the completion of the secondary transfer, the mode shifts to the second speed mode. At this time, by applying a bias having a polarity opposite to the secondary transfer bias from the secondary transfer unit 16, the photosensitive member 22 and the intermediate transfer are transferred. The discharge product adhering to the intermediate transfer belt 40 due to the rubbing with the belt 40 can be prevented from being transferred to the secondary transfer device 16 side, and subsequent recording of the back surface of the recording material S is generated. Can be suppressed. Furthermore, by performing the second speed mode immediately after the secondary transfer in this way, the operating rate of the image forming apparatus can be improved, and the discharge product can be easily removed before the adhesion force increases. Become.

Next, a modified example in the second speed mode will be described.
In the second speed mode described above, the speed difference between the photosensitive member 22 and the intermediate transfer belt 40 is constant. However, when the influence due to the discharge during the charging process is large, the second speed mode The speed difference may be set large, or the duration of the second speed mode may be set long.
In addition, when a sensor for detecting environmental conditions is provided and the environmental condition detection result by this sensor is determined to increase the moisture absorption of the discharge product, the speed difference in the second speed mode is set to be large, or The duration of the second speed mode may be set longer.

FIG. 10 shows a flow according to the degree of influence of discharge, (a) shows the speed difference in the second speed mode, and (b) shows the duration in the second speed mode.
That is, (a) confirms the usage history, determines the discharge influence level from the determination result, and if it is determined that the influence level is high, it is larger than the initial speed difference ΔV in the second speed mode. On the other hand, (b) confirms the usage history, determines the discharge influence level from the determination result, and if it is determined that the influence level is high, the second speed mode is set. The initial duration T is switched to a longer duration (T + β).

FIG. 11 shows a flow according to environmental conditions. (A) shows the speed difference in the second speed mode, and (b) shows the duration in the second speed mode.
That is, (a) confirms the environmental conditions, determines whether or not the environmental conditions increase the moisture absorption of the discharge product from the determination result, and if determined to increase, the initial speed of the second speed mode The difference ΔV is switched to a larger speed difference (ΔV + α). On the other hand, (b) confirms the environmental conditions and determines whether the environmental conditions increase the moisture absorption of the discharge product from the determination result. However, if it is determined to be increased, the initial duration T of the second speed mode is switched to a longer duration (T + β).
As the environmental condition, temperature and humidity may be detected. For example, only humidity may be detected.

  FIG. 12 is a table summarizing specific examples of determining the degree of influence due to discharge during the charging process from the usage history and specific examples of determining from the environmental conditions. Examples of the usage history include the elapsed time of the photosensitive member 22, The charging time in the primary transfer unit 25, the dispensing time from the developer cartridge 48, the resting time of the apparatus, and the like are listed. The influence levels are as shown in the figure.

In other words, as a result of changes in the shape of the surface of the photoreceptor, when the elapsed time is short and it is close to a new product, the discharge product is likely to adhere, and the degree of influence increases. Since the adhesion of the product is reduced, the influence is reduced.
Further, if the charging time is longer, the discharge product is generated and the influence is increased. However, if the charging time is shorter, the generation amount of the discharge product is reduced and the influence is also decreased.
Furthermore, if the dispensing time is long, the amount of discharge products is large and the influence is large because the image is formed accordingly. On the other hand, if the dispensing time is short, the amount of discharge products is small and the amount of discharge products is small. Therefore, the degree of influence is small.
Furthermore, if the pause time is increased, the adhesion strength of the discharge product attached to the photoreceptor 22 is increased and the influence is increased. However, if the pause time is short, it can be removed before the adhesion strength is increased. Therefore, the degree of influence is small.
Under environmental conditions, if the temperature and humidity are high, the discharge product adhering to the photoconductor 22 is likely to absorb moisture and adversely affect the image. However, if the humidity is low, the moisture absorption of the discharge product should be considered. Also disappear.

Therefore, the speed difference can be changed or the duration can be changed in consideration of the influence of such discharge products. That is, when it is determined that the degree of influence on the discharge product is large, the speed difference in the second speed mode is increased (specifically, the photoreceptor 22 is further decelerated), or the duration of the second speed mode. You can make it longer. By doing so, the rubbing force between the photosensitive member 22 and the intermediate transfer belt 40 is increased, and the polishing effect on the surface of the photosensitive member can be increased.
In addition, this may be determined by combining the items described above in the usage history, for example, and may be further combined with environmental conditions. The speed difference and the duration time may be appropriately combined.

The method of increasing the rubbing force between the photosensitive member 22 and the intermediate transfer belt 40 in the second speed mode is not limited to the above-described method, and may be as follows.
FIG. 13 shows an example of a pressure contact force varying mechanism 50 that changes the pressure contact force of the primary transfer device 25 with respect to the intermediate transfer belt 40. The width of the intermediate transfer belt 40 is at both ends of the rotation shaft 25 a of the primary transfer device 25. A substantially cylindrical movable member 51 having a hole portion 51a in the direction away from the back surface of the intermediate transfer belt 40 is provided in the vicinity of the portion exceeding the intermediate transfer belt 40. The movable member 51 is supported by the apparatus housing 10 in the drawing. The outer restricting member is configured to move in a linear direction connecting the center points of the primary transfer device 25 and the photosensitive member 22. In the figure, only one side of the rotation shaft 25a of the primary transfer unit 25 is shown, so only one member is shown.
Further, a biasing member 52 such as a spring is inserted into the hole 51 a of the movable member 51, and one of the biasing members 52 is fixed to the rotating shaft 25 a of the primary transfer device 25 and the other is fixed to the movable member 51. ing. Further, an eccentric cam 53 having a rotation shaft 53a at an eccentric position is provided on the surface of the movable member 51 opposite to the hole 51a. The rotation shaft 53a is rotated at an appropriate angle by a drive motor M4. Has been made.

For this reason, the eccentric cam 53 rotates by driving the drive motor M4. At this time, since the rotation shaft 53a is in an eccentric position, the movable member 51 is moved along with the rotation operation of the eccentric cam 53. It moves forward and backward in the direction of the arrow. As a result, the rotation shaft 25a of the primary transfer device 25 is pressed toward the intermediate transfer belt 40, or is relaxed on the contrary, and the pressure contact force between the primary transfer device 25 and the intermediate transfer belt 40, and consequently The pressure contact force from the intermediate transfer belt 40 to the photosensitive member 22 can be changed.
Such a pressure contact variable mechanism 50 may be provided for each primary transfer device 25 of each color, or may be divided between the K color and the other colors. Correspondingly, in order to provide the pressure contact force varying mechanism 50, a member for supporting the rotation shafts 25a of the primary transfer device 25 may be provided, and the above-described urging member 52 may be fixed to this member.

If the pressure contact force is increased by the pressure contact force varying mechanism 50, for example, when it is determined that the influence of the discharge product due to the use history is large, the rubbing force between the photosensitive member 22 and the intermediate transfer belt 40 is increased. Can be effectively increased, and discharge products can be removed. Further, when it is determined that the moisture absorption is increased according to the environmental conditions, the same effect can be obtained even if the pressure contact force is increased.
In this example, the variable pressure contact mechanism 50 using the eccentric cam 53 is shown, but the present invention is not limited to this. For example, the primary transfer device 25 may be pressed against the intermediate transfer belt 40 by a solenoid. .

Embodiment 2
FIG. 14 is a schematic diagram showing an outline of the image forming apparatus according to the second embodiment. Unlike the image forming apparatus according to the first embodiment, the image forming apparatus according to the present embodiment conveys a recording material instead of the intermediate transfer belt. The belt is used. Components similar to those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted here.

  The image forming apparatus according to the present embodiment has four photosensitive members 22 (on the recording material conveyance belt 70 that is stretched around a plurality of stretching rolls 71 to 73 and circulates and rotates and can convey the recording material S by suction. 22a to 22d) are arranged along the rotation direction of the recording material conveyance belt 70. A primary transfer unit 25 that transfers the toner image on the photosensitive member 22 onto the recording material S conveyed by the recording material conveyance belt 70 is located at a position facing the photosensitive member 22 with the recording material conveyance belt 70 interposed therebetween. The multiple toner images that are provided and transferred from the photoreceptors 22 a to 22 d on the recording material S and multiplexed are fixed by the fixing device 17 provided on the downstream side of the stretching roll 72. Yes. The fixing device 17 includes, for example, a heating roll 17a and a pressure roll 17b. Reference numeral 74 in the figure denotes a belt cleaning member that cleans deposits on the recording material conveyance belt 70.

  The drive system of the present embodiment is rotationally driven by drive motors M1 to M3 different from the K-color photoconductor 22d and the other three-color photoconductors 22a to 22c, like the drive system of the first embodiment. The K-color photoconductor 22d is rotated by the drive motor M1, and the other photoconductors 22a to 22c are rotated by the drive motor M2. Further, the recording material conveyance belt 70 is driven to rotate by a driving motor M3 with respect to a tension roll 71 which is a driving roll. Further, the drive motors M <b> 1 to M <b> 3 are controlled by the control device 80.

Next, the operation of the image forming apparatus according to the present embodiment will be described.
When a full-color image is formed on the recording material S, the first speed mode is instructed by the control device 80 to each of the drive motors M1 to M3, and the speed of all the photosensitive members 22 and the speed of the recording material conveyance belt 70 are obtained. Is substantially the same. Here, the recording material S supplied to the recording material conveyance belt 70 is electrostatically attracted to the surface of the recording material conveyance belt 70 by a charging member (not shown) and is conveyed as it is as the recording material conveyance belt 70 rotates. . To the recording material S conveyed along with the rotation of the recording material conveying belt 70, the respective color toner images are sequentially transferred from the photosensitive member 22 by the primary transfer unit 25, and the multiplexed toner images of four colors are recorded on the recording material S. Formed on top. Then, the recording material S peeled off from the recording material transport belt 70 by a peeling member (not shown) at the portion of the stretching roll 72 is fixed by being sufficiently heated and pressurized by the fixing device 17.

On the other hand, when a monochrome image is formed, the second speed mode is selected by the control device 80, and the rotational speed of the drive motor M2 is reduced, so that the three-color photoconductors 22a to 22c and the recording material are conveyed. A speed difference is provided between the belt 70 and the belt 70. Therefore, a rubbing effect acts between the photoconductors 22a to 22c and the recording material conveyance belt 70 or the recording material S, and discharge products on the photoconductors 22a to 22c are removed. Thereafter, the adhering matter on the photoconductor 22 is removed from the photoconductor 22 by a photoconductor cleaning member (not shown) arranged to face the photoconductor 22 as it is. On the other hand, deposits on the recording material conveyance belt 70 side are removed from the recording material conveyance belt 70 by the belt cleaning member 74. Incidentally, a slight amount of a residue of the discharge product may be deposited on the recording material S side by rubbing between the recording material S and the photosensitive members 22a to 22c. There is almost no influence on the transfer from 22d.
That is, also in the present embodiment, the same effect as in the first embodiment is achieved.

  In the present embodiment, the configuration in which the K-color photoconductor 22d is arranged on the most downstream side is shown, but it goes without saying that the K-color photoconductor 22d may be arranged on the most upstream side. The other three-color photoconductors 22a to 22d can remove the discharge product due to the speed difference from the recording material conveyance belt 70 without using the recording material S, and the discharge product to the recording material S can be removed. Adhesion can be further suppressed.

  In this embodiment, the drive motors M1 and M2 for the K-color photoconductor 22d and the other three-color photoconductors 22a to 22c are driven independently, but all the photoconductors 22 are independent of each other. Needless to say, they may be driven or separated into other combinations.

Example 1
In this embodiment, a blank sheet that forms the amount of discharge products remaining on a photoconductor when a speed difference is changed in a combination of a single photoconductor and an intermediate transfer belt in an image area of a specified size. It is measured in relation to the ratio of the area. Other conditions were as follows. The speed difference is expressed as a ratio of the speed of the photoconductor to the speed of the intermediate transfer belt.
The photoreceptor was φ30 mm, and the intermediate transfer belt was made of a polyimide material. The amount of the blank paper portion was a value obtained by dividing the ratio of the image density per A4 size from 100. The speed of the intermediate transfer belt was fixed at 100 mm / sec, and the speed of the photoreceptor was increased or decreased. In addition, the measurement was carried out by measuring the adhering matter adhering to the surface of the photoconductor at the portion where the photoconductor and the intermediate transfer belt were in contact with each other after performing five A4 size prints. It was carried out in terms of adhesion amount (unit: ng / cm ² ). In addition, the photoconductor which completed the measurement was cleaned with alcohol or the like and subjected to the next measurement.

  As a result, as shown in FIG. 15, it is understood that if the speed difference is increased, the amount of remaining discharge products is reduced, and the speed difference is reduced even if the photosensitive member is accelerated from the intermediate transfer belt. It has been found that a similar effect can be obtained. Further, the amount of the blank paper portion was confirmed to be in the range of 100 to 80%, but at any speed difference, the amount of the discharge product decreases as the amount of the blank paper portion decreases, that is, as the image density increases. There was a trend. In addition, since the influence of the discharge product was not seen when the amount of the blank paper portion was 70% or less, in this example, the amount of the blank paper portion was measured up to 80%.

As described above, from the amount of the discharge product, the amount of the generated discharge product is small if the speed difference is ± 0.3% or more. It was found that it can be suppressed to 0 ng / cm ² or less.
Therefore, when the surface roughness Rz of the surface of the photoreceptor after removing the discharge product was measured (based on JIS B0601: 1994), the result shown in FIG. 15 was obtained. As a result, the surface roughness is particularly large when the speed difference is 20%, and the image quality at that time is adversely affected. Therefore, the speed difference is within a range of ± (0.3 to 10.0)%. If it is in the range of ± (2.0 to 10.0)%, a result such as comprehensive judgment was obtained in which the amount of discharge products was small and there was little possibility of deteriorating the surface of the photoreceptor.

  Furthermore, since the amount of the discharge product varies depending on the amount of the blank paper portion, the discharge product increases when the blank paper portion, that is, the undeveloped area increases, so the discharge product is removed without depending on the amount of the blank paper portion. It was understood that it is effective to have a speed difference. In addition, it was determined that when the amount of blank paper portion was large (80% or more), the smaller the area where the surface of the photoreceptor after charging was covered with toner, the more susceptible to the influence of discharge products.

Example 2
In this example, the relationship between the photoreceptor usage history (number of photoreceptor cycles) and the duration of the second speed mode for the discharge product removal is confirmed.
Here, in the same manner as in Example 1, the effect of the discharge product depends on the duration when the photosensitive member is decelerated and the speed difference is 0.6% by the combination of one photosensitive member and the intermediate transfer belt. The amount of white paper used was 95%.
The evaluation was performed in the same manner as in Example 1 by calculating the time for which the surface ammonium ion was 3.0 or less by ion chromatography.

  As a result, as shown in FIG. 16, it was found that if the usage history of the photoreceptor increases, the discharge product is removed in a short time, and if the usage history is small, it is necessary to continue for a long time. This is judged to be due to the fact that the use of the photoconductor also causes the surface of the photoconductor to be worn and smoothed, and as a result, discharge products are difficult to deposit. Therefore, it is effective to change the duration of the second speed mode in accordance with the usage history of the photoreceptor.

Example 3
This example was carried out in the same manner as Example 2, and the relationship between the usage history of the photoreceptor and the speed difference was confirmed. Here, the evaluation was made assuming that the duration was constant at 5 seconds.
As a result, as shown in FIG. 17, when the usage history of the photoconductor increases, the speed difference can be reduced, which means that the use of the discharge product on the photoconductor surface decreases with use. Yes. If the photosensitive member usage history is small, that is, it is greatly affected by the speed difference at a stage of 2000 cycles or less, it is more effective to change the speed difference in such a state where the usage history is small. Was understood.

Example 4
In this embodiment, in order to confirm the influence of the environment, the relationship between the duration of the second speed mode and the atmospheric humidity is confirmed.
In this embodiment, the speed difference is 2% (the photosensitive member is decelerated), the amount of blank paper is 95%, and image defects such as image flow occur in the image while forming an image in the atmosphere. Whether or not an image defect does not occur was measured while visually judging whether or not the duration time of the second speed mode was measured.

As a result, as shown in FIG. 18, if the humidity is 50% RH or less, the duration of the second speed mode is almost unnecessary, and it was determined that there is almost no influence by moisture absorption of the discharge product. It has been found that when the humidity is 60% RH or more, a duration is required, and particularly when the humidity is 70% RH or more, a duration of 20 seconds or more is required.
Therefore, it was understood that the influence of the discharge product greatly varies depending on the environment, and therefore, it was understood that it is effective to change the second speed mode depending on the environmental conditions.

Example 5
In this example, as in Example 4, the relationship between the speed difference and the atmospheric humidity in the second speed mode was confirmed in order to confirm the influence of the environment. The evaluation method was the same as in Example 4.
As a result, as shown in FIG. 19, when the humidity is 50% RH or less, the speed difference is almost unnecessary, and it was determined that there is almost no influence by moisture absorption of the discharge product. When the humidity is 60% RH or more, a speed difference of about 3% is required. Particularly, when the humidity is 70% RH, the speed difference is 10%, and when the humidity is 80% RH or more, a speed difference of 20% or more is required. There was found.

This is because when the humidity exceeds 70% RH, a speed difference exceeding 10% is required. Therefore, from Example 1 as well, when such a speed difference is given, the surface roughness of the photoreceptor deteriorates, and the image quality becomes low. It becomes impossible to realize because it affects Therefore, as shown in Example 4, it is understood that a certain amount of duration is required in addition to the speed difference.
However, simply increasing the duration is not efficient, so a toner band or the like is used to increase the polishing effect on the surface of the photoreceptor and efficiently remove discharge products on the photoreceptor. It was understood that it was preferable.

1 is an explanatory diagram showing an overview of an image forming apparatus according to an embodiment model embodying the present invention. (A)-(c) is explanatory drawing which shows the removal effect | action of a discharge product. 1 is an explanatory diagram illustrating an image forming apparatus according to Embodiment 1. FIG. FIG. 2 is an explanatory diagram illustrating a developing device according to the first embodiment. FIG. 3 is an explanatory diagram illustrating a drive system according to the first embodiment. FIG. 3 is an explanatory diagram showing a first speed mode and a second speed mode according to the first embodiment. 3 is a flowchart illustrating speed mode selection according to the first embodiment. FIG. 6 is an explanatory diagram illustrating a toner band. 6 is a timing chart illustrating timings in a second speed mode according to a modification of the first embodiment. (A) (b) shows the flow which changes the speed difference or duration in the 2nd speed mode with respect to a use log | history. (A) (b) shows the flow which changes the speed difference or duration in the 2nd speed mode with respect to environmental conditions. It is explanatory drawing which shows the influence degree in a use history and an environmental condition. It is explanatory drawing which shows a press-contact force variable mechanism. FIG. 6 is an explanatory diagram illustrating an overview of an image forming apparatus according to a second embodiment. 2 is a table showing the results of Example 1. 10 is a graph showing the results of Example 2. 10 is a graph showing the results of Example 3. It is a graph which shows the result of Example 4. 10 is a graph showing the results of Example 5.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image holding body, 2 ... Image carrier, 3 ... Speed variable means, 4 ... Judgment means, 5 ... Speed control means, 6 ... History judgment means, 7 ... Discharge influence degree judgment means, 8 ... Environmental condition detection means, 9: Pressure contact variable means, S: Recording material

Claims (10)

A plurality of rotatable image carriers that are charged with discharge and that form and retain toner images on the surface;
A rotatable image carrier that is disposed in contact with the plurality of image carriers and that conveys a toner image on the image carrier directly or via a recording material;
Speed variable means capable of independently varying the speed of the plurality of image carriers in one or a few units smaller than the number of image carriers;
A determination means for determining whether or not each of the plurality of image carriers contributes to the image formation in performing the image formation process ;
Environmental condition detection means for detecting an environmental condition including at least humidity information around the image carrier;
The first speed mode that sets the speed of the image carrier that contributes to image formation to the first speed, and the speed of the image carrier that does not contribute to image creation is slower than the first speed , so that the speed difference from the image carrier is It has a second speed mode that is set to a second speed that increases, and when performing image forming processing , it contributes to the image carrier and the image forming determined to contribute to image forming based on the determination result by the determining means. A speed control means for controlling the speed variable means so as to select the first speed mode or the second speed mode by separating with the image carrier determined not to include ,
When the speed control means selects the second speed mode for the image carrier determined not to contribute to image formation , the environmental condition detected by the environmental condition detection means increases moisture absorption of the discharge product. If it is, select whether to set a larger speed difference due to the second speed in the second speed mode or to set a longer duration of the second speed mode than in other cases An image forming apparatus characterized by being implemented in combination or in combination. The image forming apparatus according to claim 1.
The image forming apparatus according to claim 1, wherein the speed control unit can select either the first speed mode or the second speed mode for each image carrier in the same time zone. The image forming apparatus according to claim 1.
The image forming apparatus according to claim 1, wherein the speed control unit controls the speed varying unit so that a second speed of the image holding body for which the second speed mode is selected is slower than a speed of the image carrier. The image forming apparatus according to claim 1.
The image forming apparatus further comprises toner supply control means for supplying toner to the image holding body for which the second speed mode is selected and for interposing the toner between the image holding body and the image carrying body. . The image forming apparatus according to claim 1.
When the speed control means switches from the first speed mode to the second speed mode, the first speed mode is applied to the image carrier after the toner image on the image carrier selected in the first speed mode is transferred. An image forming apparatus that switches from a mode to a second speed mode. The image forming apparatus according to claim 1.
Furthermore, history determination means for determining the use history of the image carrier,
And a discharge degree of influence determining means for determining the degree of impact of discharge to the image carrier during a charging process based on the determination result by the history determining means,
The speed control means sets the speed difference due to the second speed in the second speed mode larger when the discharge influence degree judged by the discharge influence degree judgment means is higher than in other cases. An image forming apparatus. The image forming apparatus according to claim 1.
Furthermore, history determination means for determining the use history of the image carrier,
And a discharge degree of influence determining means for determining the degree of impact of discharge to the image carrier during a charging process based on the determination result by the history determining means,
The speed control means sets the duration of the second speed mode longer when the discharge influence degree judged by the discharge influence degree judgment means is higher than in other cases. Forming equipment. The image forming apparatus according to claim 1.
Furthermore, history determination means for determining the use history of the image carrier,
A discharge influence determination means for determining an influence degree due to the discharge to the image carrier during the charging process based on the determination result by the history determination means;
A pressure contact force varying means provided on a different surface side of the image carrier from the image carrier and applying a pressure force to the image carrier via the image carrier so as to be variable;
When the discharge influence degree determined by the discharge influence degree determination means is high , the pressure contact is increased so that the pressure contact force is greater with respect to the image carrier for which the second speed mode is selected than in other cases. an image forming apparatus comprising: a pressure control means for controlling the variable force means. The image forming apparatus according to claim 1.
Furthermore, the pressing force varying means for variably impart the pressing force to the image carrier via and the image carrier provided on the image carrier with different side of the image carrier,
When the environmental condition detected by the environmental condition detection means enhances the moisture absorption of the discharge product, the pressure contact force against the image carrier in which the second speed mode is selected as compared with other cases. an image forming apparatus comprising: a, a pressure control means for controlling the pressing force varying means so increases. The image forming apparatus according to claim 2.
The difference in speed between the image carrier and the image carrier in the second speed mode when the first speed mode coexists is ΔVa, and all the image carriers are in the second speed mode during the cycle-up period before the image forming operation starts. The difference in speed between the holder and the image carrier is ΔVb, and the difference in speed between the image carrier and the image carrier in the second speed mode during the cycle down period after the image forming operation of all the image carriers is ΔVc. When
It said speed control means, an image forming apparatus wherein the speed of the image carrier to control said speed changing means so as to satisfy the relation ΔVa <ΔVb ≦ ΔVc.

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