JP3754923B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine or a printer using an electrophotographic system, and in particular, develops a plurality of image carriers and a latent image formed on the image carrier in contact with the image carriers. And an image forming apparatus capable of forming a color image.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic process, each of them is an electrophotographic photosensitive member (photosensitive member) such as a photosensitive drum, and process means such as a charging unit, a developing unit, and a cleaning unit that act on the photosensitive unit. A plurality of image forming units provided with a plurality of image forming units are juxtaposed, and images are sequentially transferred onto a transfer belt (intermediate transfer belt) or a transfer material on a transfer belt (transfer material transport belt) disposed opposite to the plurality of image forming units. There is a color image forming apparatus adopting an inline method.
[0003]
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 this process cartridge is detachably attached to the apparatus main body. There are things arranged in 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, the maintainability is greatly improved.
[0004]
As a developing means of a process cartridge used in such an in-line type color image forming apparatus, a contact developing method in which development is generally performed in a state where the developing roller is in contact with the photosensitive member, and the developing roller and the photosensitive member are used. There are two known non-contact development methods in which development is performed with a predetermined gap between them. However, the contact development method may cause the following adverse effects.
(1) When the photoconductor rotates at a timing other than during the developing operation such as pre-rotation and post-rotation, the surface of the photoconductor is scraped by rubbing with the developing roller, which becomes a factor of reducing the service life.
(2) If other color cartridges that are not involved in development are 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) The roller layer of the developing roller is permanently deformed when it is not used for a long time while attached to the main body of the image forming apparatus, causing unevenness on the image during development.
[0005]
In order to solve the above-mentioned problems, a structure in which both the photosensitive drum and the developing roller of a color not involved in image formation are retracted from the transfer belt and the driving of the photosensitive member and the developing roller is stopped, and the travel path of the transfer belt is set. For example, a structure in which the driving of the photosensitive member and the developing roller that are not involved in image formation is stopped by changing the contact with the photosensitive member of a necessary color has been adopted.
[0006]
[Problems to be solved by the invention]
However, in the case of the above-described conventional technique, the structure is complicated, or there is a possibility that a negative effect is caused by moving the position of the photosensitive drum or the traveling path of the transfer belt which is important for the image forming accuracy.
[0007]
Accordingly, the object of the present invention is to reduce deterioration of the surface layer of the photoreceptor, deformation of the developing means, waste of the developer, and avoid paper contamination without deteriorating the image forming accuracy and transfer material conveyance accuracy. An in-line type image forming apparatus capable of doing so is provided.
[0008]
Another object of the present invention is to provide an inline-type image forming apparatus that can achieve the above object with a simple configuration and at low cost.
[0009]
[Means for Solving the Problems]
  The above object is achieved by the image forming apparatus according to the present invention. In summary,The present invention relates to an image forming apparatus for forming a color image on a recording medium.
A first process cartridge for forming a black color image, comprising: an electrophotographic photosensitive drum; a developing roller for developing an electrostatic latent image formed on the electrophotographic photosensitive drum; and the electrophotographic photosensitive member. A drum unit that rotatably supports the drum, and a developing unit that rotatably supports the developing roller, wherein the developing roller is movably coupled to the drum unit and contacts the developing roller with the electrophotographic photosensitive drum. A first mounting means for detachably mounting a first process cartridge having a position and a developing unit that can take a position at which the developing roller is separated from the electrophotographic photosensitive drum;
A plurality of second process cartridges for forming an image other than black; an electrophotographic photosensitive drum; a developing roller for developing an electrostatic latent image formed on the electrophotographic photosensitive drum; and A drum unit for rotatably supporting an electrophotographic photosensitive drum, and a developing unit for rotatably supporting the developing roller, wherein the developing roller is movably coupled to the drum unit, and the developing roller is attached to the electrophotographic photosensitive drum. A second mounting means for detachably mounting a second process cartridge having a contact position for contacting and a developing unit capable of taking a developing position for separating the developing roller from the electrophotographic photosensitive drum;
A drive motor;
A driving state in which the driving force of the driving motor is transmitted to the developing roller of the first process cartridge; and a non-driving state in which the driving force of the driving motor is not transmitted to the developing roller of the first process cartridge. A first clutch that can take
A driving state in which the driving force of the driving motor is transmitted to the developing roller included in the second process cartridge; and a non-driving state in which the driving force of the driving motor is not transmitted to the developing roller included in the second process cartridge; A second clutch that can take
A first separation member movably provided, wherein the first separation member engages with the development unit included in the first process cartridge and moves the development unit from the contact position to the separation position; ,
A second separation member movably provided, wherein the second separation member engages with the development unit of the second process cartridge and moves the development unit from the contact position to the separation position; ,
A first switching member that is movably provided and engages with the first clutch and the second clutch, wherein both the first clutch and the second clutch are in the non-driving state. And a first state in which both the first clutch and the second clutch are changed from the standby state to the driving state, and a second state in which only the first clutch is changed from the standby state to the driving state. A possible first switching member;
A second switching member movably provided in conjunction with the first switching member, wherein the first separation member and the first switching member when the first switching member moves to the first state; By engaging the second spacing member and moving the first spacing member and the second spacing member, the developing unit included in the first process cartridge and the developing unit included in the second process cartridge are By moving from the separation position to the contact position, and when the first switching member is moved to the second state, the first separation member is engaged with the first separation member to move the first separation member. A second switching member that moves only the developing unit of the first process cartridge from the separated position to the contact position;
HaveAn image forming apparatus characterized by the above.
[0010]
  According to an embodiment of the present invention, the image forming apparatus is a stepping motor for moving the first switching member, and rotates the first switching member in a predetermined direction so that the first switching member is moved to the first switching member. A stepping motor for moving the first switching member in the direction of the second state by moving in the direction of the first state and rotating in a direction opposite to the predetermined direction;
[0011]
  According to another embodiment of the present invention, the second switching member includes a first cam that engages with the first separation member and a second cam that engages with the second separation member. The first cam and the second cam rotate in conjunction with the first switching member.
[0012]
  According to another embodiment of the present invention, each of the first clutch and the second clutch has a lever that engages with the first switching member, and when the lever moves, The clutch and the second clutch can be in the driving state or the non-driving state.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.
[0019]
Example 1
[overall structure]
First, the overall configuration of the image forming apparatus of this embodiment will be described with reference to FIG. In the present exemplary embodiment, the image forming apparatus uses a transfer material such as a recording sheet or an OHP sheet by an electrophotographic method in accordance with an image information signal from an external host device such as a personal computer that is communicably connected to the apparatus body. It is a full color laser beam printer capable of forming a full color image. However, the present invention is not limited to this, and can be embodied in any form such as a copying machine or a facsimile machine. FIG. 1 is a longitudinal sectional view showing the overall configuration of the image forming apparatus 100 of this embodiment.
[0020]
An image forming apparatus 100 shown in FIG. 1 has four drum-shaped electrophotographic photosensitive members arranged in a substantially vertical direction, that is, photosensitive drums 1 (1a, 1b, 1c, 1d) as image carriers. I have. The photosensitive drum 1 is driven to rotate counterclockwise in FIG. 1 by a driving means (described later) shown in FIG. A photosensitive device 1 (2a, 2b, 2c, 2d) that uniformly charges the surface of the photosensitive drum 1 in order according to the rotation direction, and a laser beam is irradiated around the photosensitive drum 1 based on image information. A scanner unit 3 (3a, 3b, 3c, 3d) that forms an electrostatic latent image on the body drum 1, and a developing device 4 (4a, 4a, 4d) that develops a toner image by attaching toner included in the developer to the electrostatic latent image 4b, 4c, 4d), an electrostatic transfer device 5 that transfers the toner image on the photosensitive drum 1 to the transfer material S, and a cleaning device 6 that removes transfer residual toner remaining on the surface of the photosensitive drum 1 after transfer. 6a, 6b, 6c, 6d) and the like are arranged.
[0021]
In this embodiment, the image forming units Pa, Pb, Pc, and Pd, which are image forming units each including the photosensitive drum 1, the charging device 2, the scanner unit 3, the developing device 4, the cleaning device 5, and the like, are different. Color (yellow, magenta, cyan, black) images are formed.
[0022]
The photosensitive drum 1 and the charging device 2, the developing device 4, and the cleaning device 6 as process means acting on the photosensitive drum 1 are integrally formed into a cartridge, and a process cartridge 7 ( 7a, 7b, 7c, 7d). FIG. 2 shows a longitudinal section of the process cartridge 7.
[0023]
Here, in the following description, the front side of the image forming apparatus 100 refers to the side where the process cartridge 7 is inserted into the apparatus main body 110, that is, the right side in FIG. The left and right sides of the image forming apparatus 100 are viewed from the front side of the apparatus.
[0024]
Hereinafter, each element will be described in more detail starting with the photosensitive drum 1.
[0025]
The photoconductor drum 1 is configured by applying an organic photoconductive layer (OPC photoconductor) to the outer peripheral surface of an aluminum cylinder having a diameter of 30 mm, for example. Both ends of the photosensitive drum 1 are rotatably supported by a support member, and a driving force from a driving motor (described later) is transmitted to one end, thereby rotating counterclockwise in FIG. Driven.
[0026]
As the charging device 2, a contact charging type charging member can be used. The charging member is a conductive roller formed in the shape of a roller. The roller is brought into contact with the surface of the photosensitive drum 1 and a charging bias voltage is applied to the roller so that the surface of the photosensitive drum 1 is made. Charge uniformly.
[0027]
  The scanner unit 3 is photosensitivebodyImage light corresponding to an image signal is arranged in a substantially horizontal direction of the drum 1 and is rotated at a high speed by a scanner motor (not shown) to a polygon mirror 9 (9a, 9b, 9c, 9d) by a laser diode (not shown). Irradiated. The image light reflected by the polygon mirror 9 selectively exposes the surface of the charged photosensitive drum 1 through the imaging lens 10 (10a, 10b, 10c, 10d) to form an electrostatic latent image. 4 and 5, the scanner unit 3 is formed longer than the pitch between the left and right side plates 32 in the longitudinal direction, and the opening holes 35 (35a, 35b, 35c, 35d, 35e, 35f, 35g, 35h) so that the projection 33 protrudes outward. At this time, the scanner unit 3 is pressed by the compression spring 36 with a force of about 1 kgf (≈9.8 N) downward by about 45 ° with respect to the horizontal as indicated by an arrow G in FIG. Thus, the scanner unit 3 is reliably pressed against the abutments 35A and 35B for positioning.
[0028]
  The developing device 4 includes a toner container 41 (41a, 41b, 41c, 41d) that stores toners of yellow, magenta, cyan, and black, respectively, as a developer. Referring to FIG. The toner inside is fed into the toner supply roller 42 by the toner transport mechanism 42. The toner is applied to the outer periphery of the developing roller 40 rotating in the clockwise direction in FIG. 2 by the toner supply roller 43 rotating in the clockwise direction in FIG. 2 and the developing blade 44 pressed against the outer periphery of the developing roller 40. Add charge. Then, the photosensitive with the latent image formedbodyBy applying a developing bias in which an AC voltage and a DC voltage are superimposed on the developing roller 40 facing the drum 1, the photosensitive roller is exposed in accordance with the latent image.bodyToner is supplied onto the drum 1.
[0029]
An electrostatic transfer belt (transfer belt) 11 that circulates as a transfer material transport unit is disposed so as to face and contact all the photosensitive drums 1. The transfer belt 11 is 10¹¹-10¹⁴It is composed of a film-like member having a volume resistivity of Ω · cm and a thickness of about 150 μm. The transfer belt 11 is supported by rollers in four directions in the vertical direction, and circulates and moves so that the transfer material S is electrostatically attracted to the outer peripheral surface on the left side in FIG. . As a result, the transfer material S is conveyed to the transfer position by the transfer belt 11, and the toner image on the photosensitive drum 1 is transferred.
[0030]
Transfer rollers 12 (12a, 12b, 12c, and 12d) are arranged in parallel at positions (transfer positions) that are in contact with the inside of the transfer belt 11 and face each of the four photosensitive drums 1 (transfer positions). A positive charge is applied from the transfer roller 12 to the transfer material S via the transfer belt 11, and the electric field due to the charge causes the transfer material S in contact with the photosensitive drum 1 to be negatively charged on the photosensitive drum 1. The toner image is transferred. The transfer belt 11 constitutes an image carrier that carries and conveys a transfer material S onto which a toner image formed on each photosensitive drum 1 is transferred.
[0031]
In this embodiment, the transfer belt 11 is a belt having a circumferential length of about 700 mm and a thickness of 150 μm. The transfer belt 11 is stretched around four rollers, a driving roller 13, driven rollers 14 a and 14 b, and a tension roller 15. It is rotated in the direction of the arrow in FIG. 1 by being driven to rotate by a drive motor (not shown) which is a carrier driving means. While the transfer belt 11 circulates and moves the transfer material S from the driven roller 14a side to the drive roller 13 side, the toner image is transferred to the transfer material S.
[0032]
The paper feed 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 paper feed cassette 17. At the time of image formation, the paper feed roller 18 (half-moon roller) and the registration roller pair 19 are rotationally driven according to the image forming operation to separate and feed the transfer material S in the paper feed cassette 17 one by one. The leading edge of the roller contacts the registration roller pair 19 and temporarily stops. After a loop is formed, the rotation of the transfer belt 11 and the image writing position are synchronized, and the sheet is fed to the transfer belt 11 by the registration roller pair 19. .
[0033]
The fixing unit 20 fixes a plurality of color toner images transferred to the transfer material S, and includes a heating roller 21a that rotates, and a pressure roller 21b that presses and applies heat and pressure to the transfer material S. Consists of. That is, the transfer material S to which the toner image on the photosensitive drum 1 is transferred is conveyed by the fixing roller pair 21a and 21b when passing through the fixing unit 20, and is given heat and pressure by the fixing roller pair 21a and 21b. It is done. As a result, toner images of a plurality of colors are fixed on the surface of the transfer material S.
[0034]
Next, the operation of the image forming apparatus 100 configured as described above will be described.
[0035]
  Each process cartridge 7 is sequentially driven in accordance with the image formation timing, and each photosensitive drum 1 is driven to rotate counterclockwise in FIG. Then, the scanner units 3 corresponding to the respective process cartridges 7 are sequentially driven. By this driving, the charging roller 2 applies a uniform charge to the peripheral surface of the photosensitive drum 1, and the scanner unit 3 is connected to the photosensitive drum 1.ofThe peripheral surface is exposed in accordance with the image signal to form an electrostatic latent image on the peripheral surface of the photosensitive drum 1. The developing roller 40 in the developing device 4 forms (develops) a toner image on the peripheral surface of the photosensitive drum 1 by transferring toner to a low potential portion of the electrostatic latent image.
[0036]
At the timing when the leading edge of the toner image formed on the peripheral surface of the most upstream photosensitive drum 1 is rotated and conveyed to a point facing the transfer belt 11 (transfer position), the image of the transfer material S is transferred to that point. The registration roller pair 19 starts rotating and feeds the transfer material S to the transfer belt 11 so that the formation start positions coincide.
[0037]
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 22 and the transfer belt 11. Further, by applying a voltage between the transfer belt 11 and the electrostatic attraction roller 22, charges are induced in the transfer material S that is a dielectric and the dielectric layer of the transfer belt 11, and the transfer material S is transferred. The belt 11 is electrostatically attracted to the outer periphery of the belt 11. As a result, the transfer material S is stably adsorbed to the transfer belt 11 and conveyed to the most downstream transfer position.
[0038]
In this way, while being transferred on the transfer belt 11, the toner images on the photosensitive drums 1 are sequentially transferred onto the transfer material S by the electric field formed between the photosensitive drums 1 and the transfer rollers 12.
[0039]
The transfer material S to which the four color toner images are transferred is separated from the transfer belt 11 by the curvature of the 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 110 by the paper discharge roller pair 23 with the image surface facing down from the paper discharge unit 24.
[0040]
[Process cartridge]
Next, the process cartridge will be described in more detail with reference to FIGS. 2 and 3 are a main sectional view and a perspective view of the process cartridge 7, respectively. The yellow, magenta, cyan, and black process cartridges 7 (7a, 7b, 7c, and 7d) have the same configuration.
[0041]
  The process cartridge 7 is a drum-shaped electrophotographic photosensitive member as an image carrier, that is, a photosensitive drum 1, a primary charging unit (charging device) 2, and a cleaning unit (cleaning device) 6.bodyDrum unit 50 and photosensitivebodyThe developing unit 4 is composed of developing means (developing device) for developing the electrostatic latent image on the drum 1.
[0042]
  In the photosensitive drum unit 50, the photosensitive drum 1 is rotatably attached to the cleaning frame 51 via bearings 31 (31a, 31b) (bearings). On the circumference of the photosensitive drum 1, a charging device 2 for uniformly charging the surface of the photosensitive drum 1, and a photosensitive memberbodyA cleaning blade 60 of the cleaning device 6 for removing the toner remaining on the drum is disposed. Further, residual toner removed from the surface of the photosensitive drum 1 by the cleaning blade 60 is sequentially sent to a waste toner chamber 53 provided behind the cleaning frame 51 by the toner feeding mechanism 52. Then, by transmitting a driving force of a driving motor (described later) disposed in the apparatus main body 110 on one end side of the process cartridge 7 on the front side in FIG. According to the image forming operation, it is rotationally driven in the arrow X direction (counterclockwise) in FIG.
[0043]
The developing unit 4 includes a developing roller 40 that contacts the photosensitive drum 1 and rotates in the direction of arrow Y (clockwise) in FIG. 2, a toner container 41 that contains toner, and a developing frame 45. The developing roller 40 is rotatably supported by the developing frame 45 via bearing members 47 and 48. Further, on the circumference of the developing roller 40, a toner supply roller 43 that rotates in the direction of arrow Z (clockwise) in FIG. 2 in contact with the developing roller 40, and developing as developer layer thickness regulating means on the developing roller 40 Each of the blades 44 is disposed. Further, in the toner container 41, a toner transport mechanism (developer stirring transport blade) 42 for stirring the stored toner and transporting it to the toner supply roller 43 is provided.
[0044]
  The developing unit 4 is configured so that the whole developing unit 4 is supported by pins 49a around support shafts 49 provided on bearing members 47 and 48 attached to both ends of the developing unit 4, respectively.PhotoconductorThe suspension unit is supported in a swingable manner with respect to the drum unit 50. When the process cartridge 7 is a single unit (not attached to the apparatus main body 110), the developing roller 40 is exposed to light by a rotational moment about the support shaft 49.bodyThe developing unit 4 is always urged by the pressure spring 53 so as to come into contact with the drum 1. Further, when the developing roller 40 is separated from the photosensitive drum 1, the separation / contact switching means 8 (described later) of the apparatus main body 110 abuts and functionally connects to the toner container 41 of the developing unit 4. A rib 46 as a receiving portion is integrally provided.
[0045]
[Drive configuration]
Next, the operation mechanism when the process cartridge 7 is mounted on the apparatus main body 110 will be described in detail with reference to FIGS. In FIG. 4, only the photosensitive drum 1 and the bearing 31 are shown for the process cartridge 7 in order to explain the configuration of the present invention in an easy-to-understand manner, but actually, the process cartridge 7 is as described above. Further, the charging device 2, the developing device 4, the cleaning device 6 and the like are integrally formed (FIG. 2).
[0046]
  As described above, when the process cartridge 7 is a single unit, the developing roller 40 is always in contact with the photosensitive drum 1 as shown in FIG. As shown in FIG. 4, the process cartridge 7 has guide grooves 34 (34a, 34b, 34c, 34d, 34e, 34f, 34g, 34h) as mounting means provided on the left and right side plates 32 from the arrow direction (the front side of the apparatus). )bodyThe bearing 31 that supports the drum 1 is inserted into the apparatus main body 110 by insertion. At this time, the transfer belt 11 is, for example, together with the front door of the apparatus main body 110.EvacuationThus, the insertion part of the process cartridge 7 is opened. 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 of the guide groove 34.
[0047]
The method for pressing the process cartridge 7 in the apparatus main body 110 is as follows. As shown in FIG. 5, a shaft 39 is crimped to the left and right side plates 32, a torsion coil spring 30 is supported on the shaft 39, and an end portion 30a thereof is fitted into a hole 32a of the left and right side plates and fixed. . In a state where the process cartridge 7 is not present, the torsion coil spring 30 is restricted in the rotational direction by a bending raising 32 b from the left and right side plates 32. When the process cartridge 7 is inserted, the torsion coil spring 30 rotates in the counterclockwise direction in FIG. 5 against the force, and is positioned as shown in FIG. The bearing 31 is pressed against the abutting surfaces 37 and 38 of the guide groove 34 with a force of about 1 kgf (≈9.8 N).
[0048]
  At this time, the back side of the apparatus main body 110 in the insertion direction of the process cartridge 7 is against the urging force of the developing unit 4 by the pressure spring 53 (FIG. 2), as shown in FIGS. The developing roller 40 is exposed to light.bodySeparation / contact switching means 8 for separating the drum 1 is disposed.
[0049]
The separation / contact switching means 8 is a separation plate for pushing up the ribs 46 (46 a, 46 b, 46 c, 46 d) provided in the developing units 4 (4 a, 4 b, 4 c, 4 d) of yellow, magenta, cyan, and black. 80 (80a, 80b, 80c, 80d) are provided. In this embodiment, the separation plate 80 is in a state where the cam 93 is rotated by the driving means shown in FIG. 9, that is, a stepping motor 90 (described later), and the separation plate 80 is pushed up by the cam 93. Are separated from the photosensitive drum 1 and are moved to a developing position where the developing roller 40 is brought into contact with the photosensitive drum 1 in a state where the push-up of the separation plate 80 by the cam 93 is released. As a result, the push-up of the separation plate 80 is released only during the development operation, and the development unit 4 is moved to the development position, that is, the position where the development roller 40 contacts the photosensitive drum 1.
[0050]
Here, although not limited thereto, the structure can be made relatively simple by limiting the operation modes of pushing up and releasing the spacing plate 80. In this embodiment, all the color separation plates 80 (80a, 80b, 80c, 80d) of yellow, magenta, cyan, and black are pushed up, and all the developing rollers 40 and the photosensitive drums 1 are separated from each other (see FIG. 1) The full-color state in which all the developing rollers 40 and the photosensitive drum 1 are in contact with each other when the separation plates 80 (80a, 80b, 80c, 80d) of all colors of yellow, magenta, cyan, and black are released. 7) and the three-color state (FIG. 8) in which only the three colors of yellow, magenta, and cyan are pushed up by the separation plates 80 (80a, 80b, 80c) and only the black developing roller 40 is in contact with the photosensitive drum 1. Allows you to select one state.
[0051]
In other words, in this embodiment, the separation / contact switching means 8 includes the black separation / contact switching means 8y formed with the black separation plate 80d and the yellow, magenta, and cyan separation plates 80a as shown in FIG. , 80b, 80c are integrated into two types of color separation / contact switching means 8z. The above-mentioned mode switching is possible by providing the cam 93 for moving the black and color separation / contact switching means 8y and 8z with two types of profiles corresponding to the respective separation / contact switching means 8y and 8z. It becomes.
[0052]
In this embodiment, the unit for driving the process cartridge 7 drives the photosensitive drum 1 from a driving motor 70 (70a, 70b, 70c, 70d) as driving means provided for each color as shown in FIG. It is branched into a series 71 (71a, 71b, 71c, 71d) to be driven and a series 72 (72a, 72b, 72c, 72d) to drive the developing roller 40. A clutch 92 (92a, 92b, 92c, 92d) as drive switching means is provided on the drive side of the developing roller 40 so that the rotation / stop of the developing roller 40 can be switched when the photosensitive drum 1 is rotating. Yes. Thus, in this embodiment, the photosensitive member driving means for driving the photosensitive drums 1 and the developing driving means for driving the developing rollers 40 are a common motor for each process cartridge. The driving force from the apparatus main body 110 side is generated by the photosensitive member drive transmission means and the development drive transmission means that are functionally connected to the drive unit on the apparatus main body 110 side when the process cartridge 7 is mounted on the apparatus main body 110, respectively. It is transmitted to the photosensitive drum 1 and the developing roller 40.
[0053]
With such a driving configuration, the driving of the photosensitive drums 1 of the respective colors can be controlled independently. Therefore, it is possible to take control to always reduce the color misregistration that is a problem in the in-line type full-color image forming apparatus. The driving of the developing roller 40 can be stopped while the drum 1 is driven. Naturally, it is much cheaper to provide the clutch as described above than to provide another motor for driving the developing roller 40.
[0054]
In this embodiment, the clutch 92 is connected and disconnected by moving the lever up and down, but in the standby state where the lever position is the center, all the clutches 92 are disconnected and the developing roller 40 does not rotate. When the lever is raised, the clutches 92 for all colors are connected and the developing rollers 40 for all colors are rotated. When the lever is lowered, the clutch is connected only for black and the developing rollers are rotated, and the other clutches remain disconnected. The operation is different for black and color.
[0055]
A cam 93 for moving each spacing plate 80 and a clutch 92 for the driving system of the developing roller 40 are performed by moving the switching member 91 up and down by one stepping motor 90. In the standby state, all the spacing plates 80 are lifted. And all the clutches 92 are set to be disengaged.
[0056]
  [Operation]
  When the process cartridge 7 is attached to the apparatus main body 110, the yellow, magenta, cyan, and black color separation plates 80 are pushed up as shown in FIG. Accordingly, the rib 46 provided in the developing unit 4 rides on the separation plate 80 in accordance with the insertion operation of the process cartridge 7, and the developing roller 40 is separated from the photosensitive drum 1 by a predetermined gap. 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 photosensitive drum 1, so that the developing roller 40 is exposed for a long time.bodyIt is possible to reliably prevent permanent deformation of the roller layer generated by contacting the drum 1.
[0057]
The image forming operation is as follows.
[0058]
In the case of full-color printing, when an image forming operation is started by a print signal, all the drive motors 70 that drive all the process cartridges 7 and the drive motor (not shown) of the transfer belt 11 rotate. At this time, since all the clutches 92 are disengaged, the developing roller 40 does not rotate.
[0059]
Next, the stepping motor 90 rotates clockwise in FIG. 9 to the first stage and raises the switching member 91 to the first stage in the upward direction, whereby the clutches 92 of the drive systems of all the developing rollers 40 are connected, All the developing rollers 40 rotate. Here, the drive motor 70 of the process cartridge 7 may be rotated after the stepping motor 90 is rotated to the first stage.
[0060]
  Next, when the stepping motor 90 rotates clockwise in FIG. 9 to the second stage, the switching member 91 rises to the second stage in the upward direction, the developing roller 40 remains rotated, and the cam 93 rotates to cause the color. The release of the separation / contact switching means 8z and 8y for black and black is released, and all the developing rollers 40 are exposed to light.bodyAn image can be formed by contacting the drum 1.
[0061]
After image formation is completed, the developing roller 40 is separated from the photosensitive drum 1 by returning the stepping motor 90 to the first stage, and then the developing roller 40 is rotated by rotating the stepping motor 90 to the initial state. The driving motor 70 of the process cartridge 7 and the driving roller of the transfer belt 11 are stopped. Here, the rotation for returning the stepping motor 90 from the first stage to the initial state may be performed after the drive motor 70 of the process cartridge 7 and the drive roller of the transfer belt 11 are stopped.
[0062]
Next, in the case of mono-color printing, when an image forming operation is started by a print signal, all the drive motors 70 that drive the process cartridge 7 and the drive motors of the transfer belt 11 are rotated. At this time, since all the clutches 92 are disengaged, the developing roller 40 does not rotate.
[0063]
Next, the stepping motor 90 rotates counterclockwise in FIG. 9 to the first stage and lowers the switching member 91 to the first stage in the downward direction, so that only the clutch 92d of the drive system of the black developing roller 40 is connected. Thus, only the black developing roller 40 rotates. Here, the drive motor 70 of the process cartridge 7 may be rotated after the stepping motor 90 is rotated to the first stage.
[0064]
Next, when the stepping motor 90 rotates counterclockwise in FIG. 9 to the second stage, the black developing roller 40 remains rotating, and the cam 93 rotates to release the push-up / switching means 8y for black. Then, the black developing roller 40 comes into contact with the photosensitive drum 1 and an image can be formed.
[0065]
After image formation is completed, the developing roller 40 is separated from the photosensitive drum 1 by returning the stepping motor 90 to the first stage, and then the developing roller 40 is rotated by rotating the stepping motor 90 to the initial state. The driving motor 70 of the process cartridge 7 and the driving roller of the transfer belt 11 are stopped. Here, the rotation for returning the stepping motor 90 from the first stage to the initial state may be performed after the drive motor 70 of the process cartridge 7 and the drive roller of the transfer belt 11 are stopped.
[0066]
In this way, in the process of forming an image, before the electrostatic latent image is formed by the scanner unit 3, the front rotation for applying a uniform charge to the peripheral surface of the photosensitive drum 1 and the electrostatic latent image are performed. After the image is developed as a toner image, processes such as post-rotation for neutralizing the potential of the peripheral surface of the photosensitive drum 1 are performed, and the photosensitive drum 1 rotates during these processes.
[0067]
As described above, in the present invention, since the separation is released in accordance with the developing operation timing, the developing roller 40 is separated during the pre-rotation and the post-rotation. Therefore, even during the image forming operation, the surface layer of the photosensitive drum 1 due to sliding with the developing roller 40 during the pre-rotation and post-rotation can be reduced.
[0068]
In addition, the photosensitive drum 1 and the transfer belt 11 are always fixed at fixed positions, and both are rotationally driven during development, and the photosensitive drum 1 serves as a transport roller. The conveyance accuracy of the transfer belt 11 or the transfer material S is not impaired.
[0069]
That is, according to the present embodiment, the conventional problems in the contact development method described above,
(1) When the photosensitive drum 1 rotates at a timing other than during the developing operation such as pre-rotation and post-rotation, the surface layer of the photosensitive drum 1 is scraped by sliding with the developing roller 40, thereby reducing the life. turn into.
(2) If the process cartridges 7 of other colors not involved in the development are also operated, such as during mono-color development, the life of the photosensitive drum 1 is greatly reduced.
(3) When a bias is not applied during non-operation, pre-rotation, and post-rotation, the developer on the developing roller 40 adheres to the photosensitive drum 1, and the developer is wasted or the developer is paper It may cause dirt.
(4) The roller layer of the developing roller 40 may be permanently deformed when it is not used for a long time while being attached to the apparatus main body 110, and this may cause unevenness on the image during development.
In addition, since the structure is simple and the position of the photosensitive drum 1 and the travel path of the transfer belt 11 that are important for the image formation accuracy are not moved, the image formation accuracy and the transfer can be reduced. The conveyance accuracy of the belt 11 or the transfer material S is not impaired.
[0070]
In each of the above embodiments, the image forming apparatus 100 is an image forming apparatus that forms a recorded image by sequentially transferring toner images from the plurality of photosensitive drums 1 to the transfer material S conveyed by the transfer belt 11. Although described, the present invention is not limited to this. For example, from a plurality of image forming units each including a plurality of photosensitive drums and a charging unit, a developing unit, a cleaning unit, and the like as process units that act on the photosensitive drums, each of the image forming units is opposed to each image forming unit. The toner images are sequentially superimposed and transferred onto an intermediate transfer belt as an intermediate transfer body that moves, and then the toner images are secondarily transferred and recorded collectively on a transfer material conveyed by a separately provided transfer material conveyance system. The present invention is equally applicable to a so-called intermediate transfer type image forming apparatus known to those skilled in the art, such as an image forming apparatus for obtaining an image, and the same effects as described above can be obtained. The intermediate transfer member constitutes an image carrier that conveys the toner image transferred from each photosensitive drum.
[0071]
In such an image forming apparatus, the drive control of the photosensitive drum, the developing roller, and the intermediate transfer belt, and the separation / contact control of the developing roller with respect to the photosensitive drum are performed in the above-described embodiment except that the transfer belt is an intermediate transfer belt. You can do the same. Here, the description of the transfer belt is replaced with the intermediate transfer belt, and the entire description of the above-described embodiment is incorporated.
[0072]
【The invention's effect】
  As explained above, according to the present invention,, PaintingRotate the developing roller when necessary without deteriorating image formation accuracy or transfer material conveyance accuracy,Electrophotographic photosensitive drumSince it is possible to realize the function to contactElectrophotographic photosensitive drumDeterioration such as scraping of the surface layer, developmentroller, Reduce developer waste,recoding mediaDirt can be avoided. Further, according to the present invention, the above-described effects can be obtained with a simple configuration and at a low cost.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an embodiment of an image forming apparatus according to the present invention, and shows a state in which a developing roller is separated from a photosensitive drum in all process cartridges mounted on the apparatus main body.
FIG. 2 is a cross-sectional view of a process cartridge mounted on the image forming apparatus of FIG.
FIG. 3 is an assembled perspective view of 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 an embodiment of a method for mounting the process cartridge to the image forming apparatus according to the present invention.
FIG. 5 is a partial cross-sectional view showing a positioning portion of the process cartridge according to the present invention to the image forming apparatus.
FIG. 6 is a partial cross-sectional view showing a positioning portion of the process cartridge according to the present invention to the image forming apparatus.
FIG. 7 is a view similar to FIG. 1 and shows a state in which the separation between the developing roller and the photosensitive drum is released in all process cartridges.
FIG. 8 is a view similar to FIG. 1 and shows a state in which the separation between the developing roller and the photosensitive drum is released in the black process cartridge and the developing roller is separated from the photosensitive drum in the other color process cartridges. is there.
FIG. 9 is a perspective view showing an operation switching mechanism according to the present invention.
FIG. 10 is a perspective view of a drive unit of a process cartridge according to the present invention.
[Explanation of symbols]
  1 (1a, 1b, 1c, 1d) Photosensitive drum
  2 (2a, 2b, 2c, 2d) Charging device
  3 (3a, 3b, 3c, 3d) Scanner unit
  4 (4a, 4b, 4c, 4d) Development device, development unit
  5 Electrostatic transfer means
  6 (6a, 6b, 6c, 6d) Cleaning device
  7 (7a, 7b, 7c, 7d) Process cartridge
  8 Separation / contact switching means
  8yTheSeparation / detachment switching means for rack
  Separation / disconnection switching means for 8z color
  11 Electrostatic transfer belt (transfer belt, image carrier)
  20 Fixing part
  40 (40a, 40b, 40c, 40d) Developing roller
  46 (46a, 46b, 46c, 46d) Rib (receiving part)
  50 photosensitivitybodyDrum unit
  53 Pressure spring
  70 (70a, 70b, 70c, 70d) Process cartridge drive motor
  71 (71a, 71b, 71c, 71d) Photosensitive drum drive system
  72 (72a, 72b, 72c, 72d) Development roller drive system
  80 (80a, 80b, 80c, 80d) separationBoard
  90 Stepping motor
  91 Switching member
  92 (92a, 92b, 92c, 92d) Clutch (drive switching means)
  93 cams

Claims (4)

In an image forming apparatus for forming a color image on a recording medium,
  A first process cartridge for forming a black color image, comprising: an electrophotographic photosensitive drum; a developing roller for developing an electrostatic latent image formed on the electrophotographic photosensitive drum; and the electrophotographic photosensitive member. A drum unit for rotatably supporting a drum, and a developing unit for rotatably supporting the developing roller, wherein the developing roller is movably coupled to the drum unit and contacts the developing roller with the electrophotographic photosensitive drum. A first mounting means for detachably mounting a first process cartridge having a position and a developing unit that can take a position at which the developing roller is separated from the electrophotographic photosensitive drum;
  A plurality of second process cartridges for forming an image other than black; an electrophotographic photosensitive drum; a developing roller for developing an electrostatic latent image formed on the electrophotographic photosensitive drum; and A drum unit for rotatably supporting an electrophotographic photosensitive drum, and a developing unit for rotatably supporting the developing roller, wherein the developing roller is movably coupled to the drum unit, and the developing roller is attached to the electrophotographic photosensitive drum. A second mounting means for detachably mounting a second process cartridge having a contact position for contacting and a developing unit capable of taking a developing position for separating the developing roller from the electrophotographic photosensitive drum;
  A drive motor;
  A driving state in which the driving force of the driving motor is transmitted to the developing roller of the first process cartridge; and a non-driving state in which the driving force of the driving motor is not transmitted to the developing roller of the first process cartridge. A first clutch that can take
  A driving state in which the driving force of the driving motor is transmitted to the developing roller included in the second process cartridge; and a non-driving state in which the driving force of the driving motor is not transmitted to the developing roller included in the second process cartridge; A second clutch that can take
  A first separation member movably provided, wherein the first separation member engages with the development unit included in the first process cartridge and moves the development unit from the contact position to the separation position; ,
  A second separation member movably provided, wherein the second separation member engages with the development unit of the second process cartridge and moves the development unit from the contact position to the separation position; ,
  A first switching member that is movably provided and engages with the first clutch and the second clutch, wherein both the first clutch and the second clutch are in the non-driving state. And a first state in which both the first clutch and the second clutch are changed from the standby state to the driving state, and a second state in which only the first clutch is changed from the standby state to the driving state. A possible first switching member;
  A second switching member movably provided in conjunction with the first switching member, wherein when the first switching member is moved to the first state, the first separation member and the first switching member; By engaging the second spacing member and moving the first spacing member and the second spacing member, the developing unit included in the first process cartridge and the developing unit included in the second process cartridge are By moving from the separation position to the contact position, and when the first switching member is moved to the second state, the first separation member is engaged to move the first separation member. A second switching member that moves only the developing unit of the first process cartridge from the separated position to the contact position;
An image forming apparatus comprising: Furthermore, the image forming apparatus includes:
  A stepping motor for moving the first switching member, wherein the first switching member is moved in the direction of the first state by rotating in a predetermined direction, and is opposite to the predetermined direction. The image forming apparatus according to claim 1, further comprising a stepping motor that moves the first switching member in the direction of the second state by rotating in the direction. The second switching member includes a first cam that engages with the first separation member, and a second cam that engages with the second separation member, and the first cam and the first cam The image forming apparatus according to claim 1, wherein the second cam rotates in conjunction with the first switching member. Each of the first clutch and the second clutch has a lever that engages with the first switching member, and when the lever moves, the first clutch and the second clutch are The image forming apparatus according to claim 1, wherein the driving state or the non-driving state can be taken.

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