JP2016224418A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a configuration capable of bringing a plurality of developing rollers into contact and separating from each other independently.SOLUTION: An image forming apparatus includes a first gear train which transmits a driving force to a developing roller possessed by a first image forming part, a second gear train which transmits the driving force to the developing roller possessed by a second image forming part forming a color image different from that of the first image forming part and is different from the first gear train, a first development moving mechanism which moves the developing roller possessed by the first image forming part with respect to a photoreceptor, and a second development moving mechanism which moves the developing roller possessed by the second image forming part with respect to the photoreceptor and is independent from the first development moving mechanism.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an image forming apparatus in which a process cartridge is detachable and employs an electrophotographic system for forming an image on a recording medium.

  Here, the electrophotographic image forming apparatus forms an image on a recording medium using an electrophotographic system. Examples of the electrophotographic image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (for example, a laser beam printer, an LED printer, etc.), a facsimile machine, a word processor, and the like.

  In addition, the process cartridge is a cartridge in which an electrophotographic photosensitive member and process means such as a charging unit and a developing unit that act on the electrophotographic photosensitive member are integrated, and the cartridge can be attached to and detached from the image forming apparatus main body. It is what.

  An electrophotographic image forming apparatus such as a printer using an electrophotographic process uniformly charges an electrophotographic photosensitive member, which is an image carrier, and forms a latent image by selective exposure to the electrophotographic photosensitive member. The latent image is developed as a developer image by developing the developer with a developing roller. Then, the developer image is transferred to a recording medium. By applying heat or pressure to the transferred developer image, the developer image is fixed on a recording medium to record an image.

  2. Description of the Related Art Conventionally, a contact / separation mechanism that separates a photosensitive member and a developing roller except during image formation is known in order to prevent wear and deterioration of the photosensitive member and the developing roller. For example, Patent Documents 1 and 2 disclose a configuration in which development contact and separation of each color is performed in a predetermined order using a development separation motor.

JP 2006-292868 A JP 2009-282126 A

  However, the configuration in which the photosensitive member and the developing roller are brought into contact with and separated from each other by using a dedicated motor increases the cost of the motor itself, and requires a space for arranging the motor, which increases the size of the apparatus. It was.

  In addition, for example, in an apparatus capable of forming color and monochrome images using yellow (Y), magenta (M), cyan (C), and black (B) toners, the above-described contact / separation order is specified. If so, there were the following problems. For example, full contact (color) for contacting all the photosensitive members and the developing roller, color separation (monochrome) for separating the Y, M, and C photosensitive members and the developing roller, and mono separation for separating the B photosensitive member and the developing roller. The case where the order of (total separation) is designated is illustrated. In this order, it is necessary that the black photosensitive member and the developing roller are in contact with each other even when the color is being printed and the black is not being printed, and the contact time of black becomes longer than necessary. In this case, there is a problem that the wear of the black photosensitive member and the developing roller is advanced, and the life of the cartridge is shortened.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a configuration capable of abutting and separating a plurality of developing rollers independently.

  In order to achieve the above object, the present invention is different from at least a first image forming unit that forms an image of a developer on a photosensitive member by a developing roller and a first image forming unit that is formed on the photosensitive member by a developing roller. And a second image forming unit that forms an image using a color developer. A driving force is transmitted to at least one of the developing roller and the photoconductor provided in the first image forming unit. And a second gear different from the first gear train that transmits a driving force to at least one of the developing roller and the photoconductor provided in the second image forming unit. A first developing roller moving member that moves the developing roller included in the first image forming unit with respect to the photosensitive member, and a driving force from the first gear row is applied to the first developing roller. Transmitted to the moving member A first developing movement mechanism including a first driving force switching unit that switches between a transmission state of moving the developing roller of the image forming unit and a blocking state of blocking the transmission; and the second image formation. A second developing roller moving member that moves the developing roller included in the section with respect to the photosensitive member, and a driving force from the second gear train to the second developing roller moving member to transmit the second developing roller moving member. And a second driving force switching means for switching between a transmission state for moving the developing roller of the image forming unit and a blocking state for blocking the transmission. To do.

  According to the present invention, it is possible to provide a configuration in which a plurality of developing rollers can be contacted and separated independently.

1 is a perspective view showing an electrophotographic image forming apparatus according to the present invention. Schematic cross-sectional view showing an electrophotographic image forming apparatus according to the present invention Sectional drawing which shows the removal | desorption operation | movement of the cartridge of the electrophotographic image forming apparatus which concerns on this invention The perspective view which shows the attachment state of the main drive unit in Example 1. FIG. Schematic side view of the development contact / separation mechanism in Embodiment 1 The perspective view which shows the main drive unit in Example 1. FIG. FIG. 3 is a top view showing a developing gear train in Embodiment 1.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in the following embodiments should be appropriately changed according to the configuration of the apparatus to which the present invention is applied and various conditions. Therefore, unless specifically stated otherwise, the scope of the present invention is not intended to be limited thereto.

[Example 1]
Hereinafter, an image forming apparatus according to Embodiment 1 of the present invention will be described with reference to FIGS.

  In the following embodiments, as the electrophotographic image forming apparatus, a full-color electrophotographic image forming apparatus in which four process cartridges are detachable is illustrated. However, the number of process cartridges attached to the electrophotographic image forming apparatus (hereinafter referred to as image forming apparatus) is not limited to this. It is appropriately set as necessary. For example, in the case of an image forming apparatus that forms a monochrome image, the number of process cartridges attached to the image forming apparatus is one.

  Further, according to the embodiment described below, a printer is exemplified as one aspect of the image forming apparatus. However, the present invention is not limited to this. For example, the present invention can also be applied to other image forming apparatuses such as a copying machine and a facsimile machine, or other image forming apparatuses such as a multi-function machine combining these functions.

<< Schematic Configuration of Image Forming Apparatus >>
First, a schematic configuration of the image forming apparatus will be described. FIG. 1 is an external perspective view of the image forming apparatus of this embodiment, and FIG. 2 is a schematic cross-sectional view of the image forming apparatus of this embodiment.

  The image forming apparatus 1 is a four-color full-color laser printer using an electrophotographic process, and forms a color image on a recording medium S. The image forming apparatus 1 is a process cartridge type, and a process cartridge P (hereinafter referred to as a cartridge) is detachably mounted on the apparatus main body 2 to form a color image on a recording medium S.

  Here, regarding the image forming apparatus 1, the side on which the apparatus opening / closing door 3 is provided is defined as a front surface (front surface), and the surface opposite to the front surface is defined as a back surface (rear surface). Further, when the image forming apparatus 1 is viewed from the front, the right side is referred to as a driving side, and the left side is referred to as a non-driving side.

  In the apparatus main body 2 of the image forming apparatus 1, four cartridges P (PY, PM, PC, and PK) of the first cartridge PY, the second cartridge PM, the third cartridge PC, and the fourth cartridge PK are horizontal. Arranged in the direction. A rotational driving force is transmitted to the first to fourth cartridges P (PY, PM, PC, PK) from a drive output unit (not shown) of the apparatus main body 2. A bias voltage (charging bias, developing bias, etc.) is supplied from the apparatus main body 2 to each of the first to fourth cartridges P (PY, PM, PC, PK) (not shown).

  Each of the first to fourth cartridges P (PY, PM, PC, PK) has the same electrophotographic process mechanism, and the color of the developer (hereinafter referred to as toner) is different. The first cartridge PY contains yellow (Y) toner and forms a yellow toner image on the surface of the photosensitive drum 40. The second cartridge PM contains magenta (M) toner and forms a magenta toner image on the surface of the photosensitive drum 40. The third cartridge PC contains cyan (C) toner, and forms a cyan toner image on the surface of the photosensitive drum 40. The fourth cartridge PK contains black (K) toner and forms a black toner image on the surface of the photosensitive drum 40.

  Above the first to fourth cartridges P (PY / PM / PC / PK), a laser scanner unit LS as exposure means is provided. The laser scanner unit LS outputs a laser beam Z corresponding to the image information. The laser beam Z passes through the exposure window portion of the cartridge P and scans and exposes the surface of the photosensitive drum 40.

  An intermediate transfer unit 11 as a transfer member is provided below the first to fourth cartridges P (PY, PM, PC, PK). The intermediate transfer unit 11 includes a driving roller 13, a turn roller 17, a tension roller 15, and a flexible transfer belt 12, and the transfer belt 12 is moved by the three rollers 13, 17, and 15. I'm hanging over.

  The photosensitive drums 40 of the first to fourth cartridges P (PY, PM, PC, PK) are in contact with the upper surface of the transfer belt 12. The contact portion is a primary transfer portion. A primary transfer roller 16 is provided inside the transfer belt 12 so as to face the photosensitive drum 40.

  The secondary transfer roller 14 is brought into contact with the turn roller 17 via the transfer belt 12. A contact portion between the transfer belt 12 and the secondary transfer roller 14 is a secondary transfer portion.

  A feeding unit 18 is provided below the intermediate transfer unit 11. The feeding unit 18 includes a feeding tray 19 on which the recording medium S is stacked and accommodated, and a feeding roller 20 that feeds the recording medium S from the feeding tray 19.

  A fixing unit 21 and a discharge unit 22 are provided on the upper left side in the apparatus main body 2 in FIG. The upper surface of the apparatus body 2 is a discharge tray 23. The recording medium S is fixed with a toner image by fixing means provided in the fixing unit 21, and is discharged to the discharge tray 23 by the discharge unit 22.

<Image forming operation>
An operation for forming a full-color image in the image forming apparatus having the above configuration will be described.

  The photosensitive drum 40 of each of the first to fourth cartridges P (PY, PM, PC, PK) is rotationally driven at a predetermined speed (the arrow direction in FIG. 2, the counterclockwise direction). The transfer belt 12 is also rotationally driven at a speed corresponding to the speed of the photosensitive drum 40 in the forward direction (direction of arrow C in FIG. 2) with respect to the rotation of the photosensitive drum.

  The laser scanner unit LS scans and exposes the surface of each photosensitive drum 40 with a laser beam Z according to the image signal of each color. Thereby, an electrostatic latent image corresponding to the image signal of the corresponding color is formed on the surface of each photosensitive drum 40. The electrostatic latent image formed on the surface of each photosensitive drum 40 is in the developing device 41 and is developed by a developing roller 42 that is rotationally driven at a predetermined speed.

  By the electrophotographic image forming process operation as described above, a yellow toner image corresponding to the yellow component of the full color image is formed on the photosensitive drum 40 of the first cartridge PY. Then, the toner image is primarily transferred onto the transfer belt 12.

  Similarly, a magenta toner image corresponding to the magenta component of the full color image is formed on the photosensitive drum 40 of the second cartridge PM. Then, the toner image is primary-transferred superimposed on the yellow toner image already transferred onto the transfer belt 12.

  Similarly, a cyan toner image corresponding to the cyan component of the full color image is formed on the photosensitive drum 40 of the third cartridge PC. Then, the toner image is primary-transferred superimposed on the yellow and magenta toner images already transferred onto the transfer belt 12.

  Similarly, a black toner image corresponding to the black component of the full color image is formed on the photosensitive drum 40 of the fourth cartridge PK. Then, the toner image is primary-transferred superimposed on the yellow, magenta, and cyan toner images already transferred onto the transfer belt 12.

  In this manner, a full-color unfixed toner image of four colors of yellow, magenta, cyan, and black is formed on the transfer belt 12.

  On the other hand, the recording medium S is separated and fed one by one at a predetermined control timing. The recording medium S accommodated in the feeding tray 19 is separated and fed one by one by the feeding roller 20. The recording medium S is introduced into a secondary transfer portion which is a contact portion between the secondary transfer roller 14 and the transfer belt 12 at a predetermined control timing.

  As a result, the four color superimposed toner images on the transfer belt 12 are sequentially transferred onto the surface of the recording medium S in sequence while the recording medium S is conveyed to the secondary transfer unit.

<Cartridge attachment / detachment configuration>
Next, the attaching / detaching operation of the cartridge P (PY / PM / PC / PK) to the apparatus main body 2 will be described with reference to FIGS. 3 (a) and 3 (b). FIG. 3A is a schematic cross-sectional view showing a state in which the cartridge tray 24 is pulled out from the apparatus main body 2 and the cartridge P is detachable. FIG. 3B is a schematic cross-sectional view showing the operation of attaching / detaching the cartridge P to / from the cartridge tray 24.

  A cartridge tray 24 in which the cartridge P can be mounted is provided in the apparatus main body 2. As shown in FIG. 3A, the cartridge tray 24 is configured to be linearly movable (push / pull out) in the directions of arrows G1 and G2 that are substantially horizontal with respect to the apparatus main body 2. The cartridge tray 24 can take a mounting position in the apparatus main body 2 and a drawing position pulled out from the mounting position.

  First, the mounting operation of the cartridge P (PY / PM / PC / PK) to the apparatus main body 2 will be described.

  The apparatus opening / closing door 3 is opened and the cartridge tray 24 is moved in the direction of arrow G1 in FIG. In this state, the cartridge P is mounted and held on the cartridge tray 24 from the direction of the arrow H1 in FIG.

  The cartridge tray 24 holding the cartridge P is moved in the direction of arrow G 2 in FIG. 3A, and the cartridge tray 24 is moved to the mounting position in the apparatus main body 2. Then, by closing the device opening / closing door 3, the mounting operation of the cartridge P to the device body 2 is completed.

  On the other hand, the removal of the cartridge P (PY / PM / PC / PK) from the apparatus main body 2 will be described.

  The cartridge tray 24 is moved to the drawer position in the same manner as the mounting operation of the cartridge P to the apparatus main body 2 described above. In this state, the cartridge P is removed in the direction of the arrow H2 in FIG. 3B, and the removal operation of the cartridge P from the apparatus main body 2 is completed.

  With the above operation, the cartridge P can be attached to and detached from the apparatus main body 2.

<Overview of drive unit>
Next, the configuration of the main drive unit 70 in the first embodiment will be described.

  4 is a perspective view of the main drive unit 70 attached to the apparatus main body 2 as viewed from the outside of the main body. In FIG. 4, for simplification, only the main body frame of the apparatus main body 2 and the main drive unit 70 attached to the apparatus main body 2 are displayed. The drum motor 71 is driven by a gear train inside the main drive unit 70, and transmits the drive to the photosensitive drum 40 and the drive roller 13 of the intermediate transfer unit 11. On the other hand, the development motor (drive source) 72 is similarly driven by a gear train inside the main drive unit 70 and transmits the drive to the development roller 42 and a development contact / separation mechanism (development movement mechanism) 60 described later. Yes. The fixing motor 73 transmits driving to the fixing unit 21 (see FIG. 2).

<Development contact / separation mechanism>
Next, the configuration of the developing contact / separation mechanism 60 according to the first embodiment will be described with reference to FIGS. 5 (a) and 5 (b). FIGS. 5A and 5B are schematic side views illustrating the development contact / separation mechanism 60.

  In each cartridge P that is mounted on the mounting portion of the apparatus body 2 in a predetermined manner, the developing device 41 is brought into contact with and separated from the photosensitive drum 40 by the developing contact / separation mechanism 60 provided in the intermediate transfer unit 11. It is swung like That is, the developing device 41 is configured to be movable with respect to the photosensitive drum 40, and has a contact position (FIG. 5A) where the developing roller 42 contacts the photosensitive drum 40 and the developing roller 42. It is possible to move to a separation position (FIG. 5B) that is separated from the drum 40.

  That is, the developing device 41 is swung in the contact direction with respect to the photosensitive drum 40 immediately before the development of each color in the image forming operation of the image forming apparatus 1, so that the developing roller 42 is as shown in FIG. It abuts against the photosensitive drum 40. Then, after the development is completed, the developing device 41 is swung away from the photosensitive drum 40, whereby the developing roller 42 is separated from the photosensitive drum 40 as shown in FIG. At the standby time when there is no print job, the developing device 41 is held in the separated state shown in FIG.

  Here, as the first image forming unit, cartridges PY, PM, and PC that form an image with toners of yellow (Y), magenta (M), and cyan (C) are illustrated. A cartridge PK that forms an image using black (K) toner is illustrated as the second image forming unit that forms an image using toner having a different color from that of the first image forming unit.

  The life of the developing device 41 is extended by the contact and separation operation of the developing device 41 (developing roller 42) with respect to the photosensitive drum 40 described above. That is, when the developing roller 42 is separated from the photosensitive drum 40, the load applied to the developing roller 42 is reduced, and the developing roller 42 can be used for a long time. Further, it is possible to prevent the toner from moving from the developing roller 42 to the photosensitive drum 40 when an image is not formed. Of course, the shorter the time in which the developing roller 42 contacts the photosensitive drum 40, the higher the effect of extending the life. Therefore, a sequence in which the developing roller 42 contacts immediately before development and separates immediately after development is desirable.

  The developing contact / separation mechanism 60 in this embodiment will be described. In each cartridge P, the photosensitive drum 40 is rotatably supported by the frame of the cartridge P. The developing device 41 is supported so as to be rotatable (swingable) with respect to the frame of the cartridge P around the developing rotation fulcrum 411. That is, the developing device 41 is supported so as to be in contact with and separated from the photosensitive drum 40.

  Then, in a state where the cartridge P is mounted on the mounting portion of the apparatus main body 2 in a predetermined manner, the drum bearing portion 61 of the frame body of the cartridge P is pressed against the apparatus main body 2 by a pressing mechanism (not shown) and positioned and fixed. Has been.

  The developing device 41 is swung by the developing contact / separation mechanism 60 around the fulcrum 411 with respect to the frame body of the cartridge P that is positioned and fixed, and the developing roller 42 is in contact with the photosensitive drum 40 And the state separated from the photosensitive drum 40.

  The developing device 41 and the development contact / separation mechanism 60 are engaged with a separation lever 63 provided in the development device 41 and a separation hook 64 provided in the development contact / separation mechanism 60 to perform a development contact / separation operation. . Each separation hook 64 is an engaging member that engages with the developing device 41 (separation lever 63) of the corresponding cartridge P.

  Next, a specific developing contact / separation operation will be described with reference to FIGS. 5 (a) and 5 (b). The development contact / separation mechanism 60 includes a first development movement mechanism and a second development movement mechanism. The second development movement mechanism includes a second separation mechanism 60b that separates or abuts the black-side development roller with respect to the photosensitive drum, and second driving force switching means. The first development movement mechanism includes a first separation mechanism 60a that separates or contacts the color-side development roller with respect to the photosensitive drum, and first driving force switching means. The second separation mechanism 60b receives a driving force from a development gear train 78b, which is a second gear train, which will be described later, and causes the development roller of the cartridge PK to separate or contact with the photosensitive drum. Move to the contact position. As will be described later, the second driving force switching means transmits the driving force from the developing gear train 78b to the developing cam 65b of the second separating mechanism 60b to move the black developing roller and the transmission state. Switch between blocked states. The first separation mechanism 60a receives a driving force from a developing gear train 78a, which is a first gear train described later, and separates the developing rollers of the cartridges PY, PM, and PC from the photosensitive drum. Or it moves to the contact position to contact. As will be described later, the first driving force switching means transmits the driving force from the developing gear train 78a to the developing cam 65a of the first separating mechanism 60a to move the developing rollers of the cartridges PY, PM, and PC. The state is switched between a state where the transmission is blocked and a state where the transmission is blocked. The second separation mechanism 60b is an independent development contact / separation mechanism that is different from the first separation mechanism 60a.

  The developing contact / separation mechanism 60 is driven to rotate by inputting driving forces to the developing cams 65a and 65b from two locations of the main drive unit 70 of the apparatus main body 2, respectively. The configuration of the driving force input will be described later. A developing cam (first developing roller moving member) 65a controls the developing contact / separation operation of the developing device 41 on the color side (cartridges PY, PM, PC). The developing cam (second developing roller moving member) 65b controls the developing contact and separation of the developing device 41 on the black side (cartridge PK).

  First, the development contact / separation operation on the color side will be described. The developing cam 65a includes a first position where the developing roller 42 of the developing device 41 contacts the photosensitive drum 40 as shown in FIG. 5A, and a developing roller 42 of the developing device 41 as shown in FIG. 5B. Has a second position away from the photosensitive drum 40. By rotating the developing cam 65a to switch to the first position or the second position, the position of the developing device 41 with respect to the photosensitive drum 40 is changed to a contact position (corresponding to the first position) or a separation position (second position). Switch to).

  The contact / separation rod 66a is driven in a linear direction by the developing cam 65a. The first position (FIG. 5A) of the development contact / separation mechanism 60 is a position that allows the developing device 41 to be in the contact position. The second position (FIG. 5B) of the development contact / separation mechanism 60 is a position where the development contact / separation mechanism 60 holds the developing device 41 in the separation position. The developing rollers provided in each of the plurality of color-side image forming units (second image forming units) are brought into the contact position or the separation position with respect to the photosensitive drum by the development contact / separation mechanism 60. Move at the same time.

  The contact / separation rod 66a is driven in such a direction that the separation hook 64 provided on the contact / separation rod 66a escapes from the separation lever 63 provided in the developing device 41. In this case, as shown in FIG. 5A, the developing roller 42 in each cartridge P is converted into a state of being in contact with the photosensitive drum 40.

  Further, the contact / separation rod 66a is driven in a direction in which the separation hook 64 contacts the separation lever 63 provided in the developing device 41. In this case, as shown in FIG. 5B, in each cartridge P, the developing roller 42 is converted to a state of being separated from the photosensitive drum 40.

  Note that the development contact / separation operation on the black side is substantially the same as the development contact / separation operation on the color side described above except that the developing device of the cartridge to be operated is different, and the description thereof will be omitted.

<Development gear train configuration>
FIG. 6 is a perspective view of the main drive unit 70. In the main drive unit 70, a drum gear train 76 is mainly disposed between the first drive frame 74 and the second drive frame 75, and a developing gear train 78 is disposed between the second drive frame 75 and the main body frame 77. . Since the development gear train 78 is involved in the development contact / separation operation, a detailed description of the drum gear train 76 is omitted here.

  Next, details of the developing gear train 78 will be described with reference to FIG. The development gear train 78 includes a development gear train 78a that is a color-side image creation gear train and a development gear train 78b that is a black-side image creation gear train. The developing gear train 78a is a first gear train that transmits driving force to the developing rollers provided in the cartridges PY, PM, and PC constituting the first image forming unit. The developing gear train 78b is a second gear train that is independent of the first gear train and transmits the driving force to the developing roller provided in the cartridge PK constituting the second image forming unit. Here, as the first image forming unit, a plurality of image forming units, such as cartridges PY, PM, and PC, are illustrated, but the number of first image forming units is not limited to this.

  In the developing gear train 78, the developing motor 72 meshes with the step gears 79a and 79b of the developing gear trains 78a and 78b, and branches to the color developing gear train 78a and the black developing gear train 78b to transmit the driving force. ing. As described above, the developing motor 72 as one driving source is a driving source for driving the developing roller of each cartridge, and also serves as a driving source for driving a developing contact / separation mechanism 60 described later.

  The development idler gear 80b receiving the driving force from the step gear 79b transmits the driving force to the developing gear 81b and the developing contact / separation gear train 82b. On the other hand, the developing idler gear 80a receiving the driving force from the step gear 79a transmits the driving force to the developing contact / separation gear train 82a and transmits the driving force to the three developing gears 81a and the developing idler gear 80c via the gear train. Yes. Here, the developing gear 81a (81b) is a drive transmission member that transmits a driving force to the developing roller of each cartridge P.

  In this manner, the color-side development contact / separation gear train 82a branches on the development gear train 78a that is the color-side image formation gear train, and the black-side development belt train 78b that is the black-side image creation gear train. The developing contact / separation gear train 82b is branched.

  Next, the configuration and operation of the development contact / separation gear trains 82a and 82b will be described. Since the development contact / separation gear trains 82a and 82b have a common configuration on the color side and the black side, the color contact side will be described here using the development contact / separation gear train 82a which is the development contact / separation gear train. . The driving force is received from the developing motor 72, and the driving force is transmitted from the developing idler gear 80a to the W chipped gear 84a via the first developing contact / separation idler gear 831a and the second development contact / separation idler gear 832a.

  A configuration around the W chipped gear (first chipped gear) 84a will be described. In a normal state, the missing tooth portion of the W missing tooth gear 84a faces the second developing contact / separation idler gear 832a, and the second developing contact / separation idler gear 832a and the W missing tooth gear 84a are not meshed with each other. The development contact / separation idler gear 832a is idling. That is, the driving force from the second developing contact / separation idler gear 832a to the W chipped gear 84a is cut off. The solenoid (first moving member) 85a is engaged with the W chipped gear 84a by a signal input from the control unit 100 to stop the rotation of the W chipped gear 84a, and retracted from the W chipped gear 84a. Then, the engagement is released, and the W chipped gear 84a moves between the retracted position allowing the rotation. At the time of the development contact / separation position transition, the solenoid 85a is energized by the first signal S1 from the control unit 100 to engage the W chipped gear 84a and stop the rotation of the solenoid 85a from the engagement position. Move to the retreat position. As a result, the W chipped gear 84a starts rotating, and the gear portion of the W chipped gear 84a meshes with the second developing contact / separation idler gear 832a. As a result, the W chipped tooth gear 84a rotates by receiving a driving force from the second developing contact / separation idler gear 832a, and the engagement with the lever 88a is released. The driving force is transmitted to the developing contact / separation gear 86a engaged with the W chipped gear 84a and the development contact / separation shaft 87a engaged with the developing cam 65a by the rotation of the W chipped gear 84a. Before the W chipped tooth gear 84a rotates once, the energization of the solenoid 85a is released by the signal S1 from the control unit 100, and the solenoid 85a moves from the retracted position to the engaged position by the biasing force of the spring. Then, the W chipped tooth gear 84a is engaged with the solenoid 85a and the lever 88a, so that the rotation stops at the position where the second developing contact / separation idler gear 832a, which is in a normal state, idles. Thereby, the position transition of the development contact / separation is completed. Note that the side portion of the development contact / separation gear 86a has a cam shape, and the development contact / separation position is detected by detecting the phase of the cam with the micro switch 89a.

  Further, the meshing portion of the W chipped gear 84a and the developing contact / separation gear 86a has a gear ratio of 1: 2. Accordingly, when the W chipped tooth gear 84a rotates once, the developing contact / separation gear 86a rotates approximately ½, the contact / separation position is switched, and when the W chipped gear 84a rotates twice, the development contact / separation gear 86a changes to one. Rotates and returns to the original position. For example, when the developing roller is in contact with the photosensitive drum, when the W chipped gear 84a rotates once, the developing contact / separation gear 86a rotates approximately ½ and switches from the contact position to the separation position. Further, when the W chipped gear 84a makes another rotation, the development contact / separation gear 86a rotates once and returns from the separation position to the contact position.

  The configuration and operation of the development contact / separation gear train 82b are the same as the operation of the development contact / separation gear train 82a. However, the solenoids (moving members) 85a and 85b are controlled by separate first and second signals S1 and S2 respectively input from the control unit 100, and are engaged with the W chipped gears 84a and 84b. Move between the retracted position and the retracted position. Note that the power supply state (energized state / non-energized state) to the coil of the solenoid 85a is switched based on the first signal S1, and the power supply state to the coil of the solenoid 85b (based on the second signal S2). The energized state / non-energized state is switched. That is, the timing at which each of the solenoids 85a and 85b moves from the engagement position to the retracted position is independently controlled regardless of the position of each other. That is, the switching between the state in which the driving force from the second developing contact / separation idler gear 832a is transmitted to the developing cam 65a as the first developing roller moving member and the state in which the transmission is blocked is the first driving force. The switching is performed by a solenoid 85a and a W chip gear 84a. Further, switching between the state in which the driving force from the second developing contact / separation idler gear 832b is transmitted to the developing cam 65b as the second developing roller moving member and the state in which the transmission is interrupted is the second driving force. This is performed by a solenoid (second moving member) 85b and a W chipped gear (second chipped gear) 84b as switching means. Then, the first driving force switching means moves the solenoid 85a in accordance with the first signal S1 input from the control unit 100 to switch between the transmission state and the cutoff state, and the second driving force switching means is the control unit 100. Can be switched between the transmission state and the cutoff state by moving the solenoid 85b by a second signal S2 that is different from the first signal S1 input from. Therefore, the first driving force switching unit and the second driving force switching unit can be controlled independently at a necessary timing. That is, it is possible to switch between the transmission state and the blocking state to the developing cam 65b when in the transmission state to the developing cam 65a, and to switch the transmission state and the blocking state to the developing cam 65b when in the blocking state to the development cam 65a. Is possible. In addition, the transmission state to the developing cam 65a can be switched to the blocking state when the developing cam 65b is in the transmitting state, and the transmitting state and the blocking state can be switched to the developing cam 65a when the developing cam 65b is in the blocking state. Is possible. For this reason, the contact time between the photosensitive drum 40 and the developing roller 42 can be minimized, the wear of the cartridge P can be reduced, and the life can be extended. In particular, since black, which is frequently used, can be brought into contact immediately before development and separated immediately after development, the effect of extending the life can be maximized.

  By the way, during the development contact / separation operation, for example, an impact due to a load variation or the like may be applied to the development contact / separation gear 86a, and the impact may be transmitted to the upstream gear train to cause uneven rotation of the development gear 81a. If rotation unevenness occurs in the developing gear 81a during image formation, it causes image defects such as blurred images and density unevenness. However, in the case of the configuration of the present embodiment, since the development gear train 78a of the development contact / separation gear train 82a is the same drive train, an image is not formed at the timing of the development contact / separation, which causes image defects. There is no. Furthermore, since the color side and black side gear trains branch directly from the developing motor 72, the impact of each other does not affect the image formation on the other side. For example, the impact of the black-side development contact / separation gear 86b is transmitted to the development motor 72 before being transmitted to the color-side development gear 81a, but the development motor 72 as a drive source is not subjected to such rotational fluctuation. For this reason, the impact on the black side is not transmitted to the developing gear on the color side. Therefore, the image quality is not affected even if the contact / separation operation is performed independently regardless of the mutual position.

  Further, by using one developing motor 72 that rotates the developing roller, the developing roller of the first image forming unit is brought into contact with or separated from the photosensitive drum, and the developing roller of the second image forming unit and the photosensitive drum are Contact and separation can be performed independently. Therefore, it is less expensive than a configuration in which the photosensitive drum and the developing roller are brought into contact with and separated from each other using a dedicated motor, and a space for arranging the dedicated motor is unnecessary, and the apparatus can be downsized.

[Other Examples]
In the above-described embodiment, the image forming gear train, the development contact / separation gear train, and the development contact / separation mechanism are arranged in the two systems of the color side and the black side. However, the present invention is not limited to this. . For example, it may be divided into two systems such as yellow, magenta and cyan / black, or may be divided into three systems or four systems. Even if comprised in this way, the effect similar to the effect mentioned above is acquired.

  In the above-described embodiment, the color side and the black side are driven by one drive source (motor), but a configuration in which a drive source is provided for each system may be used.

  Further, a development gear train (development drive train) 78 that transmits driving force to the developing roller driven by the development motor 72 and a drum gear train (drum drive train) that transmits driving force to the photosensitive drum driven by the drum motor 71. The structure which divided | segmented and 76 was shown. However, it is not limited to this. The developing contact / separation gear trains 82a and 82b and the drum gear train (drum drive train) 76 may be driven by one motor, and the development gear train (development drive train) may be driven by another motor. That is, a driving force is transmitted from one motor to at least one of the color-side developing roller and the photosensitive drum and the color-side developing contact / separation gear train, and at least one of the black-side developing roller and the photosensitive drum. In other words, the driving force may be transmitted to the developing contact / separation gear train on the black side.

  In the above-described embodiment, a configuration in which four cartridges constituting the image forming unit are used is exemplified. However, the number used is not limited, and may be set as necessary. In addition, the first image forming unit that forms an image with a developer having a color different from that of the second image forming unit is exemplified by a configuration using three cartridges as a configuration including a plurality of image forming units. The number used is not limited, and may be set as necessary.

  In the above-described embodiments, the printer is exemplified as the image forming apparatus. However, the present invention is not limited to this, and other image forming apparatuses such as a copying machine and a facsimile apparatus, or their functions are provided. Another image forming apparatus such as a combined multifunction peripheral may be used. In this embodiment, an intermediate transfer member is used, toner images of each color are sequentially transferred onto the intermediate transfer member, and the toner images carried on the intermediate transfer member are collectively transferred to a recording medium. The forming apparatus is illustrated. However, the present invention is not limited to this, and an image forming apparatus that uses a recording medium carrier and sequentially superimposes and transfers the toner images of the respective colors onto the recording medium carried on the recording medium carrier. The same effect can be obtained by applying the present invention to the contact-separation configuration between the photosensitive drum and the developing device in these image forming apparatuses.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 2 ... Apparatus main body 40 ... Photosensitive drum 41 ... Developing apparatus 42 ... Developing roller 60, 60a, 60b ... Development contact separation mechanism 63 ... Separation lever 64 ... Separation hook 65a, 65b ... Development cam 66a, 66b ... contact and separation rod 70 ... drive unit 72 ... development motor 76 ... drum gear trains 78, 78a, 78b ... development gear trains 79a, 79b ... step gears 80a, 80b, 80c ... development idler gears 81a, 81b ... development gears 82a, 82b ... Development contact / separation gear train

Claims (6)

At least a first image forming unit that forms an image of the developer on the photosensitive member by the developing roller, and a second image that forms an image of the developer different in color from the first image forming unit by the developing roller on the photosensitive member. And an image forming apparatus including:
A first gear train for transmitting a driving force to at least one of the developing roller and the photoconductor provided in the first image forming unit;
A second gear train different from the first gear train for transmitting a driving force to at least one of the developing roller and the photoconductor provided in the second image forming unit;
A first developing roller moving member that moves the developing roller included in the first image forming unit with respect to the photosensitive member, and a driving force from the first gear train to the first developing roller moving member. A first developing movement mechanism including a first driving force switching means for switching between a transmission state for transmitting and moving the developing roller of the first image forming unit and a blocking state for blocking the transmission;
A second developing roller moving member that moves the developing roller included in the second image forming unit with respect to the photoconductor, and a driving force from the second gear train to the second developing roller moving member. A second development moving mechanism including a second driving force switching means for switching between a transmission state of transmitting and moving the developing roller of the second image forming unit and a blocking state of blocking the transmission;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein a driving force is transmitted from one driving source to the first gear train and the second gear train. The first image forming unit includes a plurality of image forming units that form images of different color developers on a photosensitive member by a developing roller;
The first gear train transmits a driving force to the plurality of image forming units,
The first developing roller moving member moves a developing roller provided in each of the plurality of image forming units simultaneously to a separation position or a contact position with respect to the photosensitive member. The image forming apparatus according to 2.   The first driving force switching means is a gear that meshes with the gear of the first gear train and has a missing tooth portion that does not mesh with the gear of the first gear train; And a first moving member that moves the first chipped gear to a position that meshes with or does not mesh with the gear of the first gear train by moving according to the signal of the second drive. The force switching means is a gear that meshes with the gear of the second gear train and has a missing tooth portion that does not mesh with the gear of the second gear train, and is moved by the second signal. And a second moving member that moves the second chipped gear to a position that engages or disengages with the gear of the second gear train. Item 4. The image forming apparatus according to any one of Items 3 to 3. A controller that outputs the first signal and the second signal;
The first driving force switching means switches between the transmission state and the cutoff state based on a first signal, and the second driving force switching means changes to a second signal different from the first signal. The image forming apparatus according to claim 1, wherein the transmission state and the cutoff state are switched based on the switching state.   Switching between the transmission state and the cutoff state by the first driving force switching means and switching between the transmission state and the cutoff state by the second driving force switching means can be performed independently. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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