JP2006215117A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of reducing vibration generated by the attaching/detaching operation of a rotating body to/from an image carrier. <P>SOLUTION: The image forming apparatus includes the image carrier 1, and the rotating body 40 which is made movable between a contact position where the body 40 comes in contact with the image carrier 1 and a separating position where the body 40 is separated from the image carrier 1, and in the apparatus with the rotating body located in the contact position at the time of forming an image, regarding the relative moving velocity of the surface of the image carrier 1 to the surface of the rotating body 40 at the contact part where the image carrier 1 comes in contact with the rotating body 40, the relative moving velocity when the rotating body 40 is shifted from the separating position to the contact position is set lower than that at the time of forming the image. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more specifically, forms a recorded image by transferring an image formed on an image carrier using an electrophotographic method or an electrostatic recording method onto a transfer material. The present invention relates to an image forming apparatus such as a printer, a copier, and a facsimile.

  2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic process, for example, an electrophotographic photosensitive member (hereinafter simply referred to as “photosensitive member”) as an image carrier, and a charging unit and a developing unit that act on the photosensitive member. A plurality of image forming units provided with a process unit such as a cleaning unit are juxtaposed, and images are sequentially transferred to an intermediate transfer member or a transfer material on a transfer material transport member disposed opposite to the plurality of image forming units. There is a color image forming apparatus adopting an inline method.

  In such an in-line type color image forming apparatus, the process means such as the photosensitive member and the developing means in each image forming unit are integrally formed into a process cartridge, and the process cartridge can be attached to and detached from the image forming apparatus main body. Are arranged in a row. According to this, when the developer runs out, for example, the user can replace the process cartridge without relying on the service person to form an image again, and other consumables such as a photosensitive member can be used. Since they can be exchanged at the same time, maintenance is greatly improved.

As a developing means of a process cartridge used in such an in-line type color image forming apparatus, generally, a contact developing system that performs development in a state where the developing roller is in contact with the photosensitive member, and the developing roller and the photosensitive member. There are two known non-contact development methods in which development is performed with a predetermined gap between the two. In the contact development method, for example, the following problems may occur.
(1) When the photosensitive member rotates at a timing other than the developing operation, such as pre-rotation and post-rotation (preparation operation before and after the image forming operation to be recorded and output on the transfer material), rubbing with the developing roller As a result, the surface layer of the photoconductor is scraped, which causes a reduction in the service life.
(2) When an image forming unit of another color not involved in development is operated, such as during mono-color development, the life of the photoreceptor is greatly reduced.
(3) When no bias is applied during non-operation, pre-rotation, and post-rotation, the developer on the developing roller adheres to the photosensitive member and wastes the developer, or the developer stains paper or the like Cause.
(4) When the image forming apparatus main body is not used for a long time, the roller layer of the developing roller is permanently deformed, which causes unevenness on the image during development.

  In order to solve the above-described problem, there is a configuration in which image formation is performed in a state in which the photosensitive member and the developing roller are separated from each other in an image forming portion of a color that is not involved in image formation (see, for example, Patent Document 1). In addition, both the photosensitive member and the developing roller are withdrawn from the transfer belt, and the drive of the image carrier and the developing roller is stopped. In addition, a structure for stopping driving of an image carrier and a developing roller that are not involved in image formation has been proposed.

  In addition, as one means for obtaining an appropriate image density by the one-component development method and reducing image defects, a peripheral speed difference is provided between the image carrier and the developing roller during image formation. There is a method of setting the peripheral speed of the developing roller to a value higher than the peripheral speed of the image carrier (Patent Document 2).

  Here, for example, for an image forming unit of a color that is not involved in image formation, as a technique based on the above-described conventional technique for separating the photosensitive member and the developing roller, in the second color during the first color image forming operation, It is conceivable to extend the life of the process cartridge by adopting an “on-demand” method in which the developing roller is brought into contact with and separated from the photosensitive member (similarly to the third and fourth processes), and the image formation is highly efficient. .

However, as this adverse effect, if the developing roller is brought into contact with or separated from the photosensitive member during the image forming operation of other colors, the vibrations caused thereby cause image defects such as image blurring and shock bands. May cause adverse effects on image quality. Even when the on-demand method as described above is not adopted, it is preferable that the shock at the time of the contact / separation operation of the developing roller with respect to the photosensitive member is small from the viewpoint of the life of the process cartridge.
JP 2003-215878 A Japanese Patent No. 3275227

  An object of the present invention is to provide an image forming apparatus capable of reducing vibrations caused by a contact / separation operation of a rotating body with respect to an image carrier.

  The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention includes an image carrier, and a rotating body that is movable between a contact position that contacts the image carrier and a separated position that is separated from the image carrier. Sometimes, in the image forming apparatus in which the rotating body is in the contact position, the relative moving speed of the surface of the image carrier with respect to the surface of the rotating body at the contact portion between the image carrier and the rotating body is the rotation The image forming apparatus is characterized in that the time when the body is switched from the separated position to the contact position is smaller than that during image formation.

  According to the present invention, it is possible to reduce the vibration caused by the contact / separation operation of the rotating body with respect to the image carrier.

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

Example 1
[overall structure]
First, the overall configuration of the image forming apparatus will be described with reference to FIG. FIG. 1 is a longitudinal sectional view showing the overall configuration of the image forming apparatus A of this embodiment.

  The image forming apparatus A according to the present exemplary embodiment is configured to respond to an image information signal transmitted from an external apparatus such as a personal computer or an image reading apparatus capable of wired or wireless communication with the image forming apparatus main body (apparatus main body) B. This is a full-color laser beam printer capable of forming a full-color image on a transfer material such as a recording sheet or an OHP sheet by electrophotography. However, the present invention is not limited to this, and can be embodied in any form such as a copying machine or a facsimile.

  The image forming apparatus A includes four image forming units P (first, second, third, and fourth image forming units Pa, Pb, Pc, and Pd) that are image forming units. Since the configurations and operations of the image forming units Pa, Pb, Pc, and Pd are substantially the same except that the development colors are different, the image forming unit for any color will be described below unless otherwise required. The subscripts a, b, c, and d given to the reference numerals to indicate that they belong to the elements will be omitted and will be described generally.

  The image forming unit P includes four drum-shaped photoreceptors (photoreceptor drums) 1 arranged side by side in a substantially vertical direction as image carriers. As will be described in detail later, the photosensitive member 1 is rotationally driven counterclockwise in FIG. 1 by driving means (FIG. 9).

  The photosensitive member 1 is irradiated with a laser beam on the basis of the image information, and a charging device 2 as a charging unit (primary charging unit) for uniformly charging the surface of the photosensitive member 1 in order according to the rotation direction. A scanner unit (laser scanner) 3 as an exposure unit for forming an electrostatic latent image on the upper surface, a developing device (developing unit) 4 for developing a toner image by attaching a toner included in a developer to the electrostatic latent image, and a photosensitive member An electrostatic transfer device 5 that transfers the toner image on the transfer material S to the transfer material S, a cleaning device 6 that removes transfer residual toner remaining on the surface of the photoreceptor 1 after the transfer process, and the like are disposed.

  Different colors (yellow, magenta, cyan, black) depending on the four image forming portions Pa, Pb, Pc, Pd provided with the photoreceptor 1, the charging device 2, the scanner unit 3, the developing unit 4, the cleaning device 6, and the like. The image is formed. Here, in this embodiment, the photosensitive member 1, the charging device 2, the developing unit 4, and the cleaning device 6 are integrally formed into a cartridge to form a process cartridge 7 (first, second, third, and fourth process cartridges). 7a, 7b, 7c, 7d). The process cartridge 7 is detachably attached to the apparatus main body B through attachment means such as a guide groove 34 (FIG. 5) described later. The process cartridge is not limited to the embodiment, and the photosensitive member and at least one of a charging unit, a developing unit, and a cleaning unit as a processing unit that acts on the photosensitive unit are integrally formed into a cartridge, and the cartridge is attached to the apparatus main body. And can be removed.

  Hereinafter, each element of the image forming apparatus A will be described in detail with reference to FIG. FIG. 2 shows a longitudinal section of the process cartridge 7. Here, in the following description, the front side of the image forming apparatus A refers to the side where the process cartridge 7 is inserted into the apparatus main body B, that is, the right side in FIG. The left and right sides of the image forming apparatus A are viewed from the front side.

  The photoconductor 1 is, for example, an OPC photoconductor configured by applying an organic optical conductor layer to the outer peripheral surface of an aluminum cylinder having a diameter of 25 mm. The photoreceptor 1 is rotatably supported at both ends by support members. The photosensitive member 1 is rotationally driven in the direction of the arrow X (counterclockwise) in FIG. 2 by transmitting the driving force from the driving motor (FIG. 9) to one end.

  As the charging device 2, a contact charging type using a charging member in contact with the photoreceptor 1 can be used. In this embodiment, the charging member is a conductive roller (charging roller) 2 formed in a roller shape. The charging roller 2 is brought into contact with the surface of the photoreceptor 1 and a charging bias voltage is applied to the charging roller 2 to uniformly charge the surface of the photoreceptor 1.

  The scanner unit 3 is arranged in a substantially horizontal direction of the photosensitive member 1, and image light corresponding to an image signal is irradiated to a polygon mirror 9 rotated at high speed by a scanner motor (not shown) by a laser diode (not shown). Is done. The image light reflected by the polygon mirror 9 selectively exposes the surface of the charged photoreceptor 1 through the imaging lens 10 to form an electrostatic image (latent image). As shown in FIG. 5, the scanner unit 3 is formed shorter than the pitch between the side plates 32 (the left side plate 32A and the right side plate 32B) in the longitudinal direction (the rotation axis direction of the photosensitive member 1). Is attached to a positioned intermediate frame 35.

  Each of the developing units 4 includes a developer container 41 that stores a developer of each color of yellow, magenta, cyan, and black (in this embodiment, a negatively charged nonmagnetic one-component developer, that is, toner). The developing container 41 is provided with a developing roller 40 as a developer carrying member, a developer transport mechanism 42, a toner supply roller 43 as a developer supplying member, a developing blade 44 as a developer regulating member, and the like. The toner in the developer container 41 is sent to the toner supply roller 43 by the transport mechanism 42. The toner supply roller 43 that rotates in the arrow Z direction (clockwise) in FIG. 2 and the developing blade 44 that is pressed against the outer periphery of the developing roller 40 are used to rotate the developing roller 40 that rotates in the arrow Y direction (clockwise) in FIG. A toner is applied to the outer periphery, and a charge is applied to the toner. Then, a developing bias is applied to the developing roller 40 facing the photosensitive member 1 on which the electrostatic image is formed, thereby supplying toner onto the photosensitive member 1 according to the latent image.

A transfer belt 11 is disposed as a transfer material transport body that circulates and moves so as to face and be in contact with all the photoreceptors 1. The transfer belt 11 is formed of a film-like member having a thickness of about 110 μm and having a volume resistivity of 10 ¹¹ to 10 ¹⁴ Ω · cm. The transfer belt 11 is supported by a roller with three axes in the vertical direction. The transfer belt 11 electrostatically attracts a transfer material S as a transfer target onto which a toner image is transferred from the photosensitive member 1 to the outer peripheral surface on the left side in the drawing so that the transfer material S comes into contact with the photosensitive member 1. It moves cyclically. The transfer material S is conveyed by the transfer belt 11 to the transfer portion N that faces the photoreceptor 1. Further, transfer rollers 12 as transfer means are juxtaposed at positions facing the inside of the transfer belt 11 and facing each of the four photoreceptors 1. A positive charge is applied from the transfer roller 12 to the transfer material S via the transfer belt 11, and a negative polarity on the photoreceptor 1 is applied to the transfer material S in contact with the photoreceptor 1 by an electric field due to the charge. The toner image is transferred.

  In this embodiment, the transfer belt 11 is a belt having a circumferential length of about 560 mm and a thickness of 110 μm. The transfer belt 11 is stretched by three rollers: a driving roller 13, a driven roller 14, and a tension roller 15, and is driven by a driving source (not shown). Drive is transmitted to the roller 13 and rotates in the direction of the arrow (clockwise) in FIG. As a result, the transfer belt 11 circulates and transfers the toner image while the transfer material S is conveyed from the driven roller 14 side to the drive roller 13 side.

  In addition, the transfer material S may not be fed due to an unexpected situation, and toner may remain on the transfer belt 11. At this time, in this embodiment, a predetermined peripheral speed difference is provided between the photosensitive member 1 and the transfer belt 11, and the transfer belt 11 is rotated quickly. As a result, the toner on the transfer belt 11 is efficiently transferred to the photoreceptor 1 and collected in the process cartridge 7 to clean the transfer belt 11. In this embodiment, as described later, the peripheral speed of the photosensitive member 1 can be controlled, so that the transfer belt drive source (which is required to increase the belt peripheral speed when cleaning the transfer belt 11) ( For example, the output of the motor can be kept low. As a result, it is possible to reduce the size and cost of the apparatus related to the transfer belt 11.

  The feeding unit 16 feeds and conveys the transfer material S to the image forming unit, and a plurality of transfer materials S are stored in the feeding cassette 17. At the time of image formation, the feeding roller 18 (D-cut roller) and the registration roller pair 19 are driven and rotated according to the image forming operation. The transfer material S in the feed cassette 17 is separated and fed one by one by the feed roller 18, and the leading end of the transfer material S hits the registration roller pair 19 to form a loop. Thereafter, the transfer material S is fed to the transfer belt 11 by the registration roller pair 19 so as to be synchronized with a predetermined image writing position. In addition, an electrostatic adsorption roller 25 for electrostatically adsorbing the transfer material S to the transfer belt 11 is in contact with the transfer belt 11 at a position facing the driven roller 14.

  The fixing unit 20 as a fixing unit fixes the toner images of a plurality of colors transferred to the transfer material S. The fixing unit 20 includes a rotating heating roller 21 and a pressure roller 22 that presses against the rotating roller 21 and applies heat and pressure to the transfer material S. That is, the transfer material S on which the toner image on the photosensitive member 1 is transferred is conveyed by the fixing roller pair 21 and 22 when passing through the fixing unit 20 and is given heat and pressure by the fixing roller pair 21 and 22. It is done. As a result, the toner images of a plurality of colors are fixed on the surface of the transfer material S.

  Next, an image forming operation will be described. The process cartridge 7 is sequentially driven in accordance with the image formation timing (at the time of forming an image recorded on the transfer material S and output), and each photosensitive member 1 is driven to rotate in accordance with the drive. In response to the operation of the process cartridge 7, the scanner unit 3 is driven. First, the charging roller 2 applies a uniform charge to the peripheral surface of the photoconductor 1, and then the scanner unit 3 exposes the peripheral surface of the photoconductor 1 according to an image signal. Thereby, an electrostatic latent image is formed on the peripheral surface of the photoreceptor 1. The developing roller 40 in the developing unit 4 transfers the toner to the low potential portion of the electrostatic image. As a result, a toner image is formed (developed) on the circumferential surface of the photoreceptor 1. Next, at the timing when the leading edge of the toner image formed on the peripheral surface of the photoreceptor 1a on the most upstream side in the conveyance direction of the transfer material S is rotated and conveyed to a substantially opposite point to the transfer belt 11, the transfer is performed to the opposite point. The registration roller pair 19 feeds the transfer material S to the transfer belt 11 so that the recording start positions of the material S coincide.

  The transfer material S is pressed against the outer periphery of the transfer belt 11 so as to be sandwiched between the electrostatic adsorption roller 25 and the transfer belt 11, and a voltage is applied between the transfer belt 11 and the electrostatic adsorption roller 25. Electric charges are induced in the transfer material S that is a dielectric and the dielectric layer of the transfer belt 11, and electrostatically adsorbed on the outer periphery of the transfer belt 11. As a result, the transfer material S is stably adsorbed to the transfer belt 11 and conveyed to the transfer portion N at the most downstream side. In the process in which the transfer material S is conveyed in this way, the toner images on the photoconductors 1 are sequentially transferred to the transfer material S by an electric field formed between the photoconductors 1 and the transfer roller 12. The transfer material S onto which the four color toner images have been transferred is separated (curvature separation) from the transfer belt 11 by the curvature of the belt driving roller 13 and is carried into the fixing unit 20. After the toner image is thermally fixed by the fixing unit 20, the transfer material S is discharged out of the apparatus main body B by the discharge roller pair 23 with the image surface facing down from the discharge unit 24.

[Process cartridge]
Next, the process cartridge will be described in more detail. FIG. 2 shows a main cross section of the process cartridge 7 containing toner. The yellow, magenta, cyan, and black process cartridges 7a, 7b, 7c, and 7d have the same configuration.

  The process cartridge 7 includes a photoreceptor unit 50 including the photoreceptor 1, the charging roller 2, and the cleaning device 6, and a developing unit 4 having a developing roller 40 as a developing unit that develops an electrostatic latent image on the photoreceptor 1. , Is divided into. In the photoconductor unit 50, the photoconductor 1 is rotatably attached to a cleaning frame 51 forming a housing of the photoconductor unit 50 through bearings 31 (left bearing 31A, right bearing 31B) (FIG. 5). Yes. On the periphery of the photoreceptor 1, a charging roller 2 for uniformly charging the surface of the photoreceptor 1 and a cleaning blade as a cleaning means for removing the developer (toner) remaining on the photoreceptor 1. 60 is arranged. Further, the toner and other deposits removed from the surface of the photoreceptor 1 by the cleaning blade 60 are sequentially sent to a waste toner chamber 53 provided behind the cleaning frame 51 by a waste toner transport mechanism 52. The driving force of a driving source (driving motor) (FIG. 9) in the apparatus main body B on one end side (back side of the paper surface in FIG. 2) in the longitudinal direction of the process cartridge 7 (rotational axis direction of the photoreceptor 1) is transmitted. As a result, the photosensitive member 1 is rotationally driven in the direction of arrow X (counterclockwise) in FIG. 2 in accordance with the image forming operation.

  The developing unit 4 contacts the circumference of the photoreceptor 1 during image formation and rotates in the direction indicated by the arrow Y (clockwise) in FIG. 2, the developer container 41 containing toner, and the circumference of the developing roller 40. A toner supply roller 43 that contacts the top and rotates in the direction of arrow Z (clockwise) in FIG. 2, a developing blade 44 that contacts the periphery of the developing roller 40, and agitates the toner contained in the developer container 41. A transport mechanism 42 that transports the toner supply roller 43 and a developing device frame 45 that forms a housing of the developing unit 4 are provided. The developing roller 40 is rotatably supported by the developing frame body 45 via a bearing member. As described above, the developing frame 45 functions as a holding unit for the developing roller 40. In this embodiment, the rotation axes of the photosensitive member 1, the developing roller 40, and the toner supply roller 43 are substantially parallel.

  The developing unit 4 is configured so that the whole developing unit 4 is supported by pins 48 around a support shaft 49 provided on each of bearings 47 attached to both ends in the longitudinal direction of the developing device frame 45 (rotational axis direction of the developing roller 40). The photoconductor unit 50 is supported so as to be swingable. Thus, the developing unit 4 has a suspended structure with respect to the photoreceptor unit 50.

  The developing unit 4 is attached so that the developing roller 40 comes into contact with the photosensitive member 1 by a rotational moment about the support shaft 49 when the process cartridge 7 is in a single state (not attached to the apparatus main body B). It is always biased by a pressure spring 54 as a biasing means. Further, the developer container 41 of the developing unit 4 is integrally provided with a rib 46 as an abutting portion for abutting a separating means (described later) of the apparatus main body B when the developing roller 40 is separated from the photoreceptor 1. Is provided.

[Removal of process cartridge]
Next, the attaching / detaching operation of the process cartridge 7 will be described with reference to FIGS. In FIG. 5, a process cartridge 7 (see FIG. 2) in which the photosensitive member 1, the charging roller 2, the developing unit 4, and the cleaning device 6 are integrally formed is referred to as the photosensitive member 1 for easy understanding of the configuration. Only the bearing 31 is shown in a simplified manner.

  As described above, when the process cartridge 7 is in a single state, the developing roller 40 is always in contact with the photoreceptor 1 as shown in FIG. As shown in FIG. 5, the process cartridge 7 is provided in a guide groove 34 (left guide grooves 34A1, 34A2, 34A3, 34A4, right guide grooves 34B1, 34B2, 34B3, 34B4) as mounting means provided in the apparatus main body B. Along with this, bearings 31 (left bearing 31A and right bearing 31B) for supporting the photosensitive member 1 are inserted into the apparatus main body B by inserting them from the direction of the arrows in the figure. At this time, for example, the transfer belt 11 is retracted together with the door C (FIG. 1) on the front side of the apparatus main body B to open the insertion portion of the process cartridge 7. As shown in FIG. 6, the position of the process cartridge 7 is determined by pressing the bearing 31 against the abutting surfaces 37 and 38 as positioning means provided in the respective guide grooves 34.

  The method of pressing the process cartridge 7 in the apparatus main body B is as follows. As shown in FIGS. 7A and 7B, shafts 39 are respectively crimped to the left and right side plates 32. A pressing lever 70 as a pressing member is attached to the shaft 39 so as to be rotatable. One end of a tension spring (torsion coil spring) 30 as a pressing force generating means is fixed to the pressing lever 39. The other end of the tension spring 30 is fixed to the fixing portion 72. The fixing portion 72 is interlocked with the opening / closing of the door C of the apparatus main body B, along the guide shapes (for example, bending up) 33 provided on the left and right side plates 32 in the direction indicated by the solid line / broken line arrows in the drawing. A movable rod 71 is provided.

  As shown in FIG. 7B, when the door C is opened, the pressing lever 70 is moved by the action portion 73 provided on the rod 71 in accordance with the movement of the rod 71 in the direction indicated by the broken line arrow in the drawing. It moves in the direction indicated by the broken arrow (counterclockwise), and the process cartridge 7 insertion part is opened, so that the process cartridge 7 can be inserted and removed. At this time, the tension spring 30 is close to the natural length of the spring, and the pressing force hardly acts. Then, as shown in FIG. 7A, when the process cartridge 7 is inserted and the door C is further closed, the pressing lever 70 moves along the solid line in the drawing as the rod 71 moves in the direction indicated by the solid arrow in the drawing. By rotating in the direction indicated by the arrow (clockwise) and the tension spring 30 is pulled, the bearing 31 is pressed against the abutting portions 37 and 38 of the side plate 32 with a force of about 10 N in the direction of the solid arrow.

  As shown in FIGS. 1 and 3, a developing device frame 45 is placed against the urging force of the pressure spring 54 (FIG. 2) of the developing unit 4 on the back side of the apparatus main body B in the insertion direction of the process cartridge 7. Separation cams (plate cams) 80 (first, second, third, and fourth separation cams 80a, 80b, 80c, and 80d as separation means for swinging the development roller 40 away from the photosensitive member 1 ) Is arranged. The separation cam 80 pushes up the ribs 46 (first, second, third, and fourth ribs 46a, 46b, 46c, and 46d) provided in the developing units 4 for yellow, magenta, cyan, and black. Each process cartridge 7 is provided correspondingly.

  The contact / separation of the developing roller 40 with respect to the photoreceptor 1 by the separation cam 80 is performed as follows. As shown in FIG. 8, in this embodiment, the separation cam drive device 90 as the drive means for the separation means has a stepping motor 91 as a drive means for the separation means. Although not limited to this, in this embodiment, the driving force of one stepping motor 91 is branched by a drive transmission gear train 92 included in the separation drive device 90 and transmitted to all the separation cams 80. The Thereby, in this embodiment, each separation cam 80 rotates in the same direction with the same phase.

  The separation cam 80 is rotated by the stepping motor 91, and the separation cam 80 swings the process cartridge 7 via the rib 46 in accordance with this rotation. As a result, the position of the developing roller 40 with respect to the photosensitive member 1 is switched between a contact position where the developing roller 40 is in contact with the photosensitive member 1 and a separation position where the developing roller 40 is separated from the photosensitive member 1.

  In this embodiment, (i) the separation cam 80 contacts the rib 46 at the maximum radius in the image forming portion P of all colors of yellow, magenta, cyan, and black, and all the developing rollers 40 and the photosensitive member 1 are separated from each other. A standby state, (ii) a full-color state in which all the developing rollers 40 and the photosensitive member 1 are in contact with each other, and (iii) Monocolor in which the developing roller 40 and the photosensitive member 1 are separated from each other in the yellow, magenta, and cyan image forming portions Pa, Pb, and Pc, and the developing roller 40 is in contact with the photosensitive member 1 only in the black image forming portion Pd. Selection of the three modes of the state is possible.

  In the full color mode, in each of the image forming portions P for yellow, magenta, cyan, and black, the developing roller 40 sequentially contacts the photosensitive member 1 in this order at predetermined time intervals to form an image. Further, when the developing roller 40 is separated from the photoreceptor 1, similarly, the developing roller 40 can be separated from the photoreceptor 1 sequentially in the above order with a predetermined time interval.

  The separation unit driving device 90 is controlled by a controller 200 of an engine control unit that performs overall control of the operation of the image forming apparatus A. The controller 200 includes a calculation unit, a control unit, and a storage unit, and sequence-controls the separation unit driving device 90 according to the separation unit control program stored in the storage unit. That is, the controller 200 has a function as a control unit for the separation cam 80.

[Driver]
Next, an operation mechanism when the process cartridge 7 is mounted on the apparatus main body B will be described with reference to FIG.

  In this embodiment, the peripheral speed (surface movement speed) of the photosensitive member 1 can be changed with respect to the peripheral speed (surface movement speed) of the developing roller 40 independently at each image forming portion P. In the present embodiment, the driving source is independent for the developing roller 40 and the photosensitive member 1, and the driving source is independent for each photosensitive member 1. In this embodiment, the driving source of each photoconductor 1 can be shifted independently.

  As shown in FIG. 9, a cartridge driving device 100 as a driving means for driving the cartridge 7, in particular, the developing roller 40 and the photosensitive member 1, includes a photosensitive member driving motor 101A as a photosensitive member driving means and a photosensitive member drive transmission series 102A. Have The photoconductor drive transmission series 102A includes a gear train that transmits drive from the photoconductor drive motor 101A to the photoconductor 1. In this embodiment, one photosensitive member driving motor 101A and one photosensitive member driving transmission series 102A are provided for each color image forming portion P.

  Further, the cartridge driving device 100 includes a developing roller driving motor 101B as a developing roller driving means and a developing roller driving system 102B. The developing roller driving system 102B transmits a clutch (developing driving clutch) CL as switching means for switching driving transmission / release from the developing roller driving motor 101B, and is transmitted from the developing roller driving motor 101B via the developing driving clutch CL. A gear train for transmitting the generated drive to the developing roller 40. In other words, in this embodiment, the developing roller driving system 102B branches the driving from one developing roller driving motor 101B to the image forming unit P for each color. The developing drive clutch CL is provided for each color image forming portion P between the developing roller driving motor 101B and the rotating shaft of the developing roller 40. Thereby, the rotation / stop of each developing roller 40 can be controlled independently during rotation of the photosensitive member 1.

  The cartridge driving device 100 is controlled by a controller 200 of an engine control unit that performs overall control of the operation of the image forming apparatus A. As described above, the controller 200 includes a calculation unit, a control unit, and a storage unit, and performs sequence control of the cartridge driving device 100 in accordance with the control program for the separating means stored in the storage unit. That is, the controller 200 has a function as a control unit for the developing roller 40 and the photosensitive member 1. The controller 200 can independently control the driving of each photoreceptor driving motor 101A and the developing roller driving motor 101B. Further, the peripheral speed of the photosensitive member 1 can be independently changed by independently controlling the respective photosensitive member driving motors 101A.

  In addition, since the drive of each color photoconductor 1 can be controlled independently by the above drive configuration, it is possible to take control to reduce color misregistration that easily occurs in an inline-type full-color image forming apparatus.

[Operation]
Next, contact / separation control of the developing roller 40 with respect to the photoreceptor 1 will be described.

  When the process cartridge 7 is attached to the apparatus main body B, as shown in FIG. 3, all the separation cams 80 of the four-color image forming portions P are in contact with the ribs 46 with the maximum radius. . Accordingly, along the insertion operation of the process cartridge 7, the rib 46 provided on the developing unit 4 rides on the separation cam 80, and the developing roller 40 is separated from the photoreceptor 1 by a predetermined gap. At this time, the separation cam 80 of each image forming portion P is at the home position shown in FIG. 10A, and the ribs 46 are pushed up in all the image forming portions.

  This separated state is always maintained when the power is turned off and when development is not performed. Accordingly, even when the process cartridge 7 is mounted and not used for a long time, the developing roller 40 is always separated from the photoconductor 1, so that the developing roller 40 is brought into contact with the photoconductor 1 for a long time. Thus, permanent deformation of the roller layer that occurs can be reliably prevented.

  Hereinafter, image forming (recording and printing) operations will be described separately for full-color printing and mono-color printing.

-Full color printing-
In the case of full-color printing, when a recording operation is started by a print signal, all motors (photoconductor driving motor 101A and developing roller driving motor 101B) that drive the process cartridge 7 and a driving motor (not shown) for the transfer belt 11 are illustrated. ) Starts to rotate. At this time, all the development drive clutches CL are disengaged, and all the development rollers 40 have stopped rotating.

  Next, the developing drive clutch CL of the first image forming unit Pa is turned on, and the developing roller 40 of the first image forming unit Pa rotates. Next, when the stepping motor 91 rotates by a predetermined amount, as shown in FIG. 10B, all the separating cams 80 rotate counterclockwise in the drawing by a predetermined amount (phase θ). Immediately after that, the push-up of the rib 46 by the separation cam 80 is released in the first image forming portion Pa, and the developing device frame 45 is oscillated by the urging force of the pressure spring 54, so that the developing roller 40a and the photosensitive roller are exposed. The body 1a contacts. Thereafter, image formation is started. Hereinafter, similarly, the second image forming unit Pb (FIG. 10C) and the third image forming unit Pc are opened with a predetermined time interval (interval at which the separating cam 80 rotates by the cam phase difference θ). (FIG. 10D), in the fourth image forming portion Pd (FIG. 10E), the developing roller 40 sequentially contacts the photosensitive member 1. In this way, full color printing can be performed. Typically, after the second image forming portion Pb, the developing roller 40 abuts against the photosensitive member 1 while image formation is performed one upstream side in the conveyance direction of the transfer material S. Is done.

  After the image formation is completed, the stepping motor 91 further rotates, and accordingly, the separation cam 80 further rotates from the state shown in FIG. First, in the first image forming portion Pa, the separation cam 80 pushes up the rib 46 again against the urging force of the pressure spring 54, and the developing frame body 45 swings, whereby the developing roller 40a is moved to the photosensitive member. Separated from 1a. Subsequently, the developing drive clutch CL of the first image forming portion Pa is released, and the rotation of the developing roller 40a is stopped. Thereafter, in the second, third, and fourth image forming portions Pb, Pc, and Pd, a predetermined interval (interval at which the separating cam 80 rotates by the cam phase difference θ) is opened as in the contact. The developing roller 40 is sequentially separated from the photoreceptor 1. Thus, the image formation in the full color print mode is completed. In this embodiment, all the motors (photosensitive member driving motor 101A and developing roller driving motor 101B) that drive the process cartridge 7 after the developing roller 40 is separated from the photosensitive member 1 in all the image forming units, and the transfer The drive motor (not shown) of the belt 11 stops rotating.

-Mono color mode (black and white mode)-
In the mono-color mode, as in the full-color mode, first, when a recording operation is started by a print signal, all the motors (photosensitive member driving motor 101A and developing roller driving motor 101B) that drive the process cartridge 7; A transfer belt drive motor (not shown) starts rotating. At this time, all the development drive clutches CL are disengaged, and all the development rollers 40 have stopped rotating.

  Next, the developing drive clutch CL of the fourth image forming unit Pd is turned on, and the developing roller 40 of the fourth image forming unit Pd rotates. Then, the stepping motor 91 rotates (reverses with respect to the full color mode), and the separation cam 80 rotates clockwise (reverses with respect to the full color mode) from the home position shown in FIG. 11A by a predetermined amount (phase θ ′). Thus, as shown in FIG. 11B, the rib 46 is pushed up by the separation cam 80 only in the fourth image forming portion Pd, and the developing roller 40 and the photosensitive member 1 come into contact with each other. At this time, in the first, second, and third image forming portions Pa, Pc, and Pc, the separation cam 80 keeps pushing up the rib 46, and the developing roller 40 and the photosensitive member 1 do not come into contact with each other, and the monochromatic color Image formation in the mode becomes possible.

  At the end of the mono color mode, the developing roller 40 and the photosensitive member 1 are separated from each other in all four color image forming units by rotating in reverse by θ ′ rotated at the time of contact (forward rotation with respect to the full color mode). It becomes a state. Thereafter, all the motors (photoconductor driving motor 101A, developing roller driving motor 101B) for driving the process cartridge 7 and the driving motor (not shown) for the transfer belt 11 stop rotating.

[Circumferential speed change]
Next, the switching operation of the peripheral speed difference between the developing roller 40 and the photoreceptor 1 which is characteristic in the present embodiment will be described.

  In this embodiment, at the time of image formation, the peripheral speed (surface movement speed) of the photosensitive member 1 and the peripheral speed (surface movement speed) of the developing roller 40 are obtained so as to obtain an appropriate image density and reduce image defects. There is a speed difference (circumferential speed difference) between the two. In this embodiment, at the time of image formation, the photosensitive member 1 and the developing roller 1 move in the same direction at the contact portion, and the peripheral speed of the developing roller 40 is made higher than the peripheral speed of the photosensitive member 1.

  However, as in the present embodiment, during image formation in the upstream image forming portion P in the moving direction of the transfer belt 11, the photosensitive member 1 and the developing roller in the adjacent downstream image forming portion P. When the contact operation with 40 is performed, an image defect such as image blurring or a shock band may be caused by a shock at that time.

  Therefore, in this embodiment, the relative movement speed of the surface of the photosensitive member 1 with respect to the surface of the developing roller 40 at the contact portion between the photosensitive member 1 and the developing roller 40 is such that the position of the developing roller 40 with respect to the photosensitive member 1 is from the separated position. A configuration in which the switching to the contact position is smaller than that at the time of image formation. In particular, in this embodiment, when the position of the developing roller 40 with respect to the photosensitive member 1 is switched from the separated position to the contact position, the surface moving speed of the photosensitive member 1 and the surface moving speed of the developing roller 40 are substantially the same. That is, in this embodiment, when the position of the developing roller 40 with respect to the photosensitive member 1 is switched from the separated position to the contact position, the relative movement speed is set to substantially zero.

  Referring to FIG. 12, the full color mode will be further described as an example. In this embodiment, first, all the photoconductor drive motors 101A start rotating (step 101), and the circumference of the developing roller 40 during image formation is set. All the photoconductors 1 rotate at a speed Vr (in this embodiment, constant during image formation and when the developing roller 40 is in contact with the photoconductor 1) and a substantially constant peripheral speed Vd1. Start (step 102). At this time, the drive motor of the transfer belt 11 starts to rotate almost simultaneously, and the transfer belt 11 starts to rotate. Further, the developing drive motor 101B starts to rotate (step 103).

  Subsequently, drive transmission by the development drive clutch CL of the first image forming unit Pa is started (step 104), and the developing roller 40a of the first image forming unit Pa rotates at the peripheral speed Vr (step 105). Next, as described above, the separation cam 80 starts rotating with the rotation of the stepping motor 91 (step 106), and the developing roller 40a of the first image forming portion Pa is brought into contact with the photosensitive member 1a. (Step 107).

  After that, for image formation, the peripheral speed of the photoconductor 1 is changed from the peripheral speed Vd1 when the developing roller 40 contacts the photoconductor 1 by electrical control of the photoconductor drive motor 101A. Slowly decelerate to speed Vd2 (<Vd1) (step 108). As a result, the peripheral speed of the developing roller 40 is faster than that of the photoreceptor 1. Next, the latent image is written from the scanner unit 3 to the photosensitive member 1, and the developing process is further performed (step 109).

  Similarly, in the second image forming portion Pb, the developing roller 40b and the photosensitive member 1b are rotated in a state where the photosensitive member 1b is rotated at the peripheral speed Vr of the developing roller 40b at the time of image formation and Vd1 which is substantially constant. 1b is brought into contact, and thereafter, the peripheral speed of the photosensitive member 1b is gradually reduced to Vd2 for development. In the following, the third and fourth image forming portions Pb and Pc are sequentially set so that the circumferential speed of the photosensitive member 1 and the developing roller 40 is substantially constant when the developing roller 40 and the photosensitive member 1 are in contact with each other, as described above. After the contact, the peripheral speed of the photosensitive member 1 is reduced to the peripheral speed at the time of image formation.

  By the operation as described above, shock and vibration to the image forming system due to the contact operation of the developing roller 40 with the photoreceptor 1 are greatly reduced, and a high-quality image can be obtained.

  Further, not only when the developing roller 40 is brought into contact with the photosensitive member 1, but also when the developing roller 40 is separated from the photosensitive member 1, it is possible to reduce the shock due to load fluctuations at the time of separating the developing roller 40. it can.

  Therefore, in this embodiment, the relative movement speed of the surface of the photosensitive member 1 with respect to the surface of the developing roller 40 at the contact portion between the photosensitive member 1 and the developing roller 40 is such that the position of the developing roller 40 with respect to the photosensitive member 1 is the contact position. The configuration is such that when switching from the position to the separation position is smaller than when forming an image. In particular, in this embodiment, when the position of the developing roller 40 with respect to the photosensitive member 1 is switched from the contact position to the separated position, the surface moving speed of the photosensitive member 1 and the surface moving speed of the developing roller 40 are substantially the same. That is, in this embodiment, when the position of the developing roller 40 with respect to the photosensitive member 1 is switched from the contact position to the separation position, the relative movement speed is set to substantially zero.

  Further description will be made with reference to FIG. 13. In the developing process, as described above, the photosensitive member 1 rotates at the peripheral speed Vd2 and rotates by the developing roller Vr (Vr> Vd) (step 201). For example, in the first image forming section Pa, after the development process is completed (step 202), the peripheral speed of the photosensitive member 1a is gradually accelerated from the peripheral speed Vd2 at the time of image formation to Vd1 (> Vd2) ( Step 203). Thereafter, rotation of the separation cam 80 is started (step 204), and the developing roller 40a is separated from the photosensitive member 1a (step 205). Thereafter, the drive transmission by the developing drive clutch CL is released (step 206), and the rotation of the developing roller 40a is stopped (step 207). Thus, the image formation in the first image forming portion Pa is completed. Thereafter, the developing roller 40 and the photosensitive member 1 are sequentially used in the second, third, and fourth image forming portions Pb, Pc, and Pd in the same manner as described above when the developing roller 40 is in contact with the photosensitive member 1. At the time of separation from the photosensitive member 1, the developing roller 40 is separated from the photosensitive member 1 by setting the circumferential speed of the photosensitive member 1 and the developing roller 40 to a substantially constant speed. As described above, after the developing roller 40 is separated from the photosensitive member 1 in all the image forming portions P, the photosensitive member driving motor 101A, the developing roller driving motor 101B, and further the driving motor (not shown) for the transfer belt 11 are shown. ) Stops rotating.

  By such an operation, shocks and vibrations to the image forming system due to the separating operation of the developing roller 40 from the photoreceptor 1 are greatly reduced, and a high-quality image can be obtained.

  Here, regarding the peripheral speed of the photosensitive member 1 at the time of contact / separation switching of the developing roller 40 with respect to the photosensitive member 1, “substantially the same” and “substantially constant speed” are the same as the peripheral speed of the developing roller 40. The peripheral speed is preferably less than ± 10% with respect to the peripheral speed of the photoreceptor 1. Furthermore, when the peripheral speed of the photoreceptor 1 and the peripheral speed of the developing roller 40 are completely constant, so-called “fogging” may occur due to toner. In order to reduce this phenomenon, it is more preferable that the peripheral speed of the developing roller 40 is slightly higher than the peripheral speed of the photosensitive member 1, and the peripheral speed of the developing roller 40 is higher than the peripheral speed of the photosensitive member 1. More preferably, it is 101% or more and less than 110%. If the peripheral speed difference is smaller than this, the above-described fog may occur. On the other hand, if the peripheral speed difference is larger than this, it is difficult to obtain a shock reduction effect at the time of contact and separation.

  On the other hand, at the time of image formation, it is preferable to provide a peripheral speed difference such that the peripheral speed of the developing roller 40 is 110% to 200% with respect to the peripheral speed of the photoreceptor 1. If the peripheral speed difference is smaller than this, the density may be reduced. On the other hand, if the peripheral speed difference is larger than this, the toner may be deteriorated.

  Normally, Vr, Vd1, and Vd2 are substantially the same between the image forming portions P, but all or a part of them may be different between the image forming portions P.

−Contact / separation speed−
Next, the contact / separation speed of the developing roller 40 with respect to the photoreceptor 1 will be described.

  As described above, in the process cartridge 7, the developing device frame 45 swings by the separation cam 80 via the rib 46 provided in the process cartridge 7. When the state transitions from the state shown in FIG. 4 to FIG. 2, that is, when the developing roller 40 abuts on the photoreceptor 1, not only the impact due to the peripheral speed difference between the developing roller 40 and the photoreceptor 1 but also the shaking of the developing frame 45. A shock to the image forming system mainly including the photosensitive member 1 due to the dynamic motion itself can be considered. Therefore, by reducing the rotational speed of the separation cam 80 as much as possible and keeping the swing speed of the developing device frame 45 low, the impact can be reduced.

  On the other hand, when the state transitions from the state of FIG. 2 to FIG. 4, that is, when the developing roller 40 is separated from the photosensitive member 1, if the life of the process cartridge 7 is taken into consideration, the separation can be performed immediately after completion of image formation. Ideal. Further, it is considered that the shock when the developing roller 40 is separated from the photosensitive member 1 is smaller than that at the time of contact. Therefore, it is preferable to quickly separate the developing roller 40 from the photosensitive member 1 by changing the rotation speed of the separation cam 80, contrary to the time of development contact.

  That is, preferably, the speed at which the developing roller 40 moves between the separation position and the contact position is higher when moving from the contact position to the separation position than when moving from the separation position to the contact position. Make it bigger. In this embodiment, the developing roller 40 is held by a developing frame body 45 as a swingable holding means, and when the developing frame body 45 swings, the developing roller 40 moves between the contact position and the separation position. Move between. Accordingly, in this case, preferably, the rocking speed of the developing frame 45 is larger when the developing roller 40 moves from the contact position to the separation position than when the development roller 40 moves from the separation position to the contact position. .

  FIG. 14 shows a modification of the process cartridge 7. In the process cartridge 7, a coil spring 81, which is an elastic member, is provided as a cushioning material between the developing frame body 45 and a bearing 55 of the developing roller 40 that is movably attached thereto. The bearing 55 is engaged with a mounting portion provided on the developing device frame 45, and is urged toward the photoreceptor 1 by a coil spring 81. Thereby, when the developing roller 40 comes into contact with the photoreceptor 1, the shock applied to the photoreceptor 1 by the developing roller 40 is alleviated. Of course, an urging member such as a leaf spring is provided from a bearing made of an elastic body instead of a coil spring, and this can be realized by a system for buffering the shock.

  As described above, according to this embodiment, it is possible to reduce the vibration caused by the contact / separation operation of the developing roller 40 with respect to the photoreceptor 1. That is, it is possible to reduce additional fluctuations and shocks to the image forming drive system when the developing roller 40 abuts and separates. Thus, by suppressing the impact and blurring on the image forming system due to the contact / separation operation of the rotating body involved in image formation represented by the developing roller 40 with respect to the image carrier, among the plurality of image forming portions P Even when the image forming unit P is performing image formation, the other image forming unit P has no color shift or shock band even when the rotating member is brought into contact with or separated from the image carrier. A good quality image can be obtained.

Example 2
Next, another embodiment of the present invention will be described. In the present embodiment, a modified example relating to a change in the contact / separation speed of the developing roller 40 with respect to the photoreceptor 1 will be described. Since the basic configuration and operation of the image forming apparatus are the same as those of the first embodiment, elements having substantially the same or corresponding functions and configurations as those of the image forming apparatus of the first embodiment are denoted by the same reference numerals and detailed description thereof will be given. Omitted.

  In the first embodiment, the rotation speed of the developing frame 45 when the developing roller 40 is brought into contact with or separated from the photosensitive member 1 is changed by the rotation speed of the separating cam 80. In contrast, in this embodiment, the swinging speed of the developing device frame 45 is controlled by changing the speed of the cam with respect to the cam shape without changing the rotational speed of the separation cam 80.

  More specifically, in this embodiment, the shape of the separation cam 80 is as shown in FIG. 15, and the swing speed is changed depending on the shapes of the separation cam 80 and the rib 46. As shown in the figure, in this embodiment, the separation cam 80 has a first peripheral surface 82 and a second peripheral surface 83 with different rates of change in the circumferential direction of the distance from the rotation shaft 84 to the periphery. The first peripheral surface 82 has a smaller change rate than the second peripheral surface 83. As shown in FIG. 15A, when the developing roller 40 is brought into contact with the photosensitive member 1, the rib 46 is pushed down while being brought into contact with the first peripheral surface 82. On the other hand, as shown in FIG. 15B, when the developing roller 40 is separated from the photoreceptor 1, the rib 46 is brought into contact with the second peripheral surface 83 so as to be quickly pushed up.

  As a result, the swinging speed of the developing frame 45 (that is, the contact / separation speed of the developing roller 40 with respect to the photosensitive member 1) is changed from when the position of the developing roller 40 with respect to the photosensitive member 1 is switched from the separating position to the contacting position. In addition, the speed can be increased when the contact position is switched to the separation position.

Example 3
Next, still another embodiment of the present invention will be described.

  In the above embodiment, by changing the surface moving speed of the photoconductor 1, the relative moving speed of the surface of the photoconductor 1 with respect to the developing roller 40 at the contact portion is set to contact / separate the developing roller 40 with respect to the photoconductor 1. However, it is also possible to change the relative moving speed by changing the surface moving speed of the developing roller 40. However, the remaining toner on the transfer material transport belt and the intermediate transfer member can be quickly cleaned, so that the first printout time (the time from when the image output start instruction is input until the first image is output) Therefore, a system that changes the peripheral speed of the photoreceptor 1 is more advantageous.

  FIG. 16 shows a schematic flow when the developing roller 40 is brought into contact with the photoreceptor 1 in this embodiment, and FIG. 17 shows a schematic flow when the developing roller 40 is separated from the photoreceptor 1. The state shown in FIGS. 16 and 17 corresponds to the state described with reference to FIGS. 12 and 13 in the configuration of the first embodiment. Therefore, here, only the characteristic part when changing the peripheral speed of the developing roller 40 will be described, and the description of the above embodiment will be referred to for the others.

  In the present embodiment, a developing drive motor 101B similar to the above is provided for each developing roller 40. When the developing roller 40 is brought into contact with the photosensitive member 1, as shown in FIG. 16, the developing roller 40 is first moved to the peripheral speed Vd of the photosensitive member 1 during image formation (in this embodiment, image formation). And at the time of contact of the developing roller 40 with the photosensitive member 1) and at a substantially constant peripheral speed Vr 1 (step 303, step 304). Then, after the developing roller 40 and the photosensitive member 1 are brought into contact with each other (steps 305 and 306), the peripheral speed of the developing roller 40 is gradually accelerated to the peripheral speed Vr2 (> Vr1) at the time of image formation (step). 307). Thereafter, the process proceeds to a latent image forming process and further to a developing process (step 308). Also in this embodiment, at the time of image formation, the peripheral speed of the developing roller 40 is made faster than the peripheral speed of the photoreceptor 1 (Vd <Vr2).

  On the other hand, when the developing roller 40 is separated from the photosensitive member 1, as shown in FIG. 17, the peripheral speed of the developing roller 40 is first set from the peripheral speed Vr2 at the time of image formation, and the developing roller 40 is moved from the photosensitive member 1. Deceleration is made to the peripheral speed Vr1 (<Vr2) at the time of separation (step 403). Then, after separating the developing roller 40 from the photoreceptor 1 (step 404, step 405), the rotation of the developing roller 40 is stopped (step 406).

  As described above, according to the configuration of the present embodiment, vibration due to the contact / separation operation of the developing roller 40 with respect to the photosensitive member 1 can be reduced.

(Other)
In each of the above embodiments, the image forming apparatus A is assumed to form a recorded image by sequentially transferring toner images from a plurality of photosensitive members 1 to a transfer material S conveyed by a transfer belt 11 as a transfer material conveyance body. did. However, the present invention is not limited to an image forming apparatus using a transfer material transport body. For example, a plurality of image forming units each including a plurality of photoconductors 1 and a charging unit, a developing unit, a cleaning unit, and the like as process units that act on the photoconductor 1, face each image forming unit. A toner image is sequentially superimposed and transferred onto a moving intermediate transfer member (for example, an intermediate transfer belt), and then the toner image is secondarily transferred collectively to a transfer material conveyed by a separately provided transfer material conveyance system. There is an image forming apparatus for obtaining a recorded image. The present invention is equally applicable to such an intermediate transfer type image forming apparatus, and it is obvious that the same effects as described above can be obtained.

  In the above description, it is assumed that the rotating body that is involved in image formation and that can be switched between contact and separation with the image carrier is the developing roller. As can be understood from the above, the present invention works extremely well in a system in which the developing roller and the photosensitive member are brought into contact with and separated from each other. However, the present invention uses the rotating member for image formation as a developer carrier. However, the present invention is not limited to the developing roller. For example, it is considered that the same effect can be obtained even with an intermediate transfer drum disposed opposite to the photoreceptor 1.

  That is, for example, in the image forming apparatus 300 shown in FIG. 18, electrostatic images are sequentially formed on the photoreceptor 1 as an image carrier in accordance with the color-separated image information. This electrostatic image is successively developed as a corresponding color toner image by a plurality of developing means (developing devices) 4 provided in the rotary developing device 320, for example. The toner image formed on the photoreceptor 1 is sequentially primary-transferred sequentially onto an intermediate transfer drum 310 as an intermediate transfer body that rotates in contact with the photoreceptor 1 each time it is formed. During the primary transfer process, a primary transfer bias is applied to the intermediate transfer drum 310. As a result, by repeating the latent image forming operation and the developing operation for the development color, a multiple toner image in which a plurality of color toner images are superimposed on the intermediate transfer drum is formed. Next, the multiple toner image on the intermediate transfer drum 310 is secondarily transferred to the transfer material S by the secondary transfer unit 330. A secondary transfer bias is applied to the secondary transfer unit 330 during the secondary transfer process. As the intermediate transfer drum 310, for example, an intermediate transfer drum 310 configured by providing an elastic layer, a release layer, etc. on an aluminum cylinder is used. In FIG. 18, elements having substantially the same or corresponding functions and configurations as those of the image forming apparatus of FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the image forming apparatus 300 having such a configuration, in order to improve transferability, a circumferential speed difference between the photoreceptor 1 and the intermediate transfer drum 310 is provided during image formation (the intermediate transfer drum 310 is faster), and the photoreceptor In order to reduce unnecessary wear between the intermediate transfer drum 310 and the intermediate transfer drum 310, the intermediate transfer drum 310 may be brought into contact with or separated from the photosensitive member 1 at times other than during image formation. In such a case, by applying the present invention, an impact at the time of contact / separation between the photosensitive member 1 and the intermediate transfer drum 310 is suppressed, and an unnecessary portion between the photosensitive member 1 and the intermediate transfer drum 310 is mainly unnecessary. Abrasion can be prevented.

  An example of a basic configuration in which the intermediate transfer drum 310 is brought into contact with and separated from the photoreceptor 1 will be described. As shown in FIG. 19, the intermediate transfer drum 310 is brought into contact with the photoreceptor 1 from the state shown in FIG. 19A to the state shown in FIG. 19B by a swinging means such as a cam (not shown). The position can be switched to the separated position. At this time, the transfer roller 330 includes an elastic body (a spring in the illustrated example) in the bearing, and is movable as the intermediate transfer drum 310 moves.

FIG. 3 is a cross-sectional view illustrating a state in which the developing roller is in contact with the photosensitive member in all the process cartridges mounted on the apparatus main body in the embodiment of the image forming apparatus according to the present invention. FIG. 2 is a cross-sectional view of a process cartridge mounted on the image forming apparatus in FIG. 1. FIG. 2 is a cross-sectional view illustrating a state where a developing roller is separated from a photosensitive member in all process cartridges in the image forming apparatus of FIG. 1. FIG. 3 is a cross-sectional view illustrating a state in which a developing roller is separated from a photoreceptor in the process cartridge of FIG. 2. FIG. 4 is a perspective view showing the vicinity of the inner plate of the apparatus main body for explaining one embodiment of a method for mounting the process cartridge to the image forming apparatus. It is a fragmentary sectional view which shows the positioning part to the image forming apparatus of the process cartridge according to this invention. It is a fragmentary sectional view which shows the positioning part to the image forming apparatus of the process cartridge according to this invention. It is a schematic diagram for demonstrating the drive method of a separation cam. It is a schematic diagram of the drive device which drives a process cartridge. It is explanatory drawing for demonstrating operation | movement of the separation cam in a full color mode. It is explanatory drawing for demonstrating operation | movement of the separation cam in monochromatic mode. It is a schematic flowchart of one Example of contact | abutting operation | movement to the photoconductor of a developing roller. It is a schematic flowchart of one Example of the separation operation | movement from the photoconductor of a developing roller. It is sectional drawing of the other Example of a process cartridge. It is the schematic of the other Example of a separation cam. FIG. 10 is a schematic flowchart of another embodiment of the contact operation of the developing roller to the photosensitive member. FIG. 10 is a schematic flowchart of another example of the operation of separating the developing roller from the photosensitive member. It is a schematic sectional drawing of the other Example of the image forming apparatus which can apply this invention. FIG. 19 is a schematic diagram for explaining an example of a method for switching the positions of the photosensitive member and the intermediate transfer drum in the image forming apparatus illustrated in FIG. 18.

Explanation of symbols

1 Photoconductor (image carrier)
4 Development unit (developing device)
7 Process cartridge 11 Transfer belt (transfer material carrier)
40 Developing roller (developer carrier, rotating body)
45 Development frame (holding means)
46 Rib (contact part)
80 Separation cam (separation means)
100 Cartridge drive device

Claims (17)

An image bearing member; and a rotating body that is movable between a contact position that contacts the image bearing member and a separated position that is separated from the image bearing member. In the image forming apparatus at the position,
The relative moving speed of the surface of the image carrier relative to the surface of the rotating body at the contact portion between the image carrier and the rotating body is greater when the rotating body is switched from the separated position to the contact position. An image forming apparatus characterized by being smaller than that at the time of image formation.   When the position of the rotating body with respect to the image carrier is switched from the separated position to the contact position, the surface moving speed of the rotating body with respect to the surface moving speed of the image carrier is 101% or more and less than 110%. An image forming apparatus.   The relative moving speed of the surface of the image carrier relative to the surface of the rotating body at the contact portion between the image carrier and the rotating body is greater when the rotating body is switched from the contact position to the separated position. The image forming apparatus according to claim 1, wherein the image forming apparatus is smaller than that during image formation.   When the position of the rotating body with respect to the image carrier is switched from the contact position to the separated position, the surface moving speed of the rotating body with respect to the surface moving speed of the image carrier is 101% or more and less than 110%. The image forming apparatus according to claim 3.   By changing the surface movement speed of the image carrier, the relative movement speed is changed when the position of the rotating body with respect to the image carrier is switched between the contact position and the separation position, and during image formation. 5. The image forming apparatus according to claim 1, wherein the image forming apparatus is changed according to claim 1.   6. The image forming apparatus according to claim 1, wherein a surface moving speed of the rotating body is higher than a surface moving speed of the image carrier during image formation.   The speed at which the rotating body moves between the contact position and the separation position is higher when moving from the contact position to the separation position than when moving from the separation position to the contact position. The image forming apparatus according to claim 1, wherein the image forming apparatus is large.   The rotating body is held by a swingable holding means, and the position of the rotating body with respect to the image carrier is switched between the separation position and the contact position by swinging the holding means. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The swing speed of the holding means is larger when the rotating body moves from the contact position to the separation position than when the rotating body moves from the separation position to the contact position. Item 9. The image forming apparatus according to Item 8.   The image forming apparatus according to claim 9, wherein the holding unit is swung by rotation of a cam contacting the holding unit, and the swing speed is changed by changing a rotation speed of the cam.   The holding means swings by rotation of a cam that contacts the holding means, and the holding means moves from the contact position to the separation position when the rotating body moves from the separation position to the contact position. 10. The image forming apparatus according to claim 9, wherein the image forming apparatus is in contact with a peripheral surface of the peripheral surface of the cam in which the rate of change in the rotation direction of the distance from the rotation shaft differs.   The rotating body is supported by a bearing movably attached to the holding means, and a buffer member made of an elastic body is provided between the bearing and the holding means. The image forming apparatus according to any one of 8 to 11.   The image forming apparatus according to claim 1, wherein the rotating body is a roller that supplies a developer to an electrostatic image formed on the image carrier.   The image forming apparatus according to claim 1, wherein the image carrier and the rotating body are integrally formed into a cartridge and detachable from the main body of the image forming apparatus.   The image bearing member, the rotating member, and the holding unit are integrally formed into a cartridge that is detachable from the main body of the image forming apparatus. Image forming apparatus.   A plurality of image forming units each having the image carrier and the rotating body are provided along a moving direction of a transfer target to which an image is transferred from the image carrier, and image formation is performed in one image forming unit. The position of the rotating body with respect to the image carrier between the contact position and the separated position is switched in another image forming unit during the operation. The image forming apparatus according to any one of 15 items.   At the time of image formation, the position of the rotating body with respect to the image carrier is sequentially switched from the separated position to the contact position from the rotating body positioned upstream in the moving direction of the transfer object. The image forming apparatus according to claim 16, wherein the rotating body positioned upstream is sequentially switched from the contact position to the separated position.

Images