Process unit and image forming apparatus

Abstract

To provide a process unit that allows contact and separation of an electrifying roller relative to a photoreceptor drum with a simple configuration.SOLUTION: A process unit 60 comprises a photoreceptor drum 36, an electrifying roller, and a cam member 80. The cam member includes an attachment part that is externally fitted to a shank 68a of the electrifying roller, and a contact part 84 that projects outward beyond an outer surface of the attachment part. The process unit brings the contact part of the cam member into contact with an outer surface of a drum body 36a to maintain a separation state of the electrifying roller, and causes the cam member to rotate following the regular rotation of the photoreceptor drum to release the contact of the contact part with the drum body, thereby changing the electrifying roller into a contact state.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus, and more particularly to a process unit and an image forming apparatus that include, for example, a photosensitive drum and a charging roller that charges the photosensitive drum. [Background technology]

[0002] An example of a conventional process unit (photosensitive unit) is disclosed in Patent Document 1. The process unit in Patent Document 1 includes a photosensitive member (photosensitive drum), a charging roller for charging the photosensitive member, and a first biasing means for biasing the charging roller in a direction toward the photosensitive member, and is detachably mounted on the image forming apparatus main body. The process unit also includes a rotating member that rotates by a driving force input from the image forming apparatus main body, a spacing member, a support member that presses and supports the spacing member when the spacing member is in the spacing position, and a second biasing means that biases the support member in a direction toward the rotation axis of the spacing member. The spacing member has an engaging portion that engages with the rotating member and receives a driving force from the rotating member, and is rotatable between a spacing position where the engaging portion engages with the rotating member to maintain a spacing state between the photosensitive member and the charge roller, and a release position where the spacing state between the photosensitive member and the charge roller is released and the photosensitive member and the charge roller can come into contact with each other, and when the separation state is released, the spacing member moves toward the photosensitive member as the first biasing means moves the charge roller toward the photosensitive member. The spacing member is shaped so that the linear distance between the rotation axis and the support member that is biased by the second biasing means and presses the spacing member increases while the spacing member rotates from the spacing position to the release position upon receiving the driving force from the rotating member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-133776 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology of Patent Document 1, the photosensitive drum and the charging roller are separated from each other using gears (gear teeth) provided on both the photosensitive drum shaft and the spacing member attached to the charging roller shaft, which makes the structure complicated and increases costs.In addition, since it is necessary to secure space for providing gears on both sides of the drum body of the photosensitive drum, the process unit becomes larger in the longitudinal direction.

[0005] SUMMARY OF THE INVENTION Therefore, a primary object of the present invention is to provide a novel process unit and image forming apparatus.

[0006] Another object of the present invention is to provide a process unit and an image forming apparatus that can move a charging roller in contact with and away from a photosensitive drum with a simple structure. [Means for solving the problem]

[0007] A first invention is a process unit including a photosensitive drum and a charging roller for charging the photosensitive drum, the process unit including cam members rotatably provided on both ends of a shaft portion of the charging roller at positions within a longitudinal range of a drum body of the photosensitive drum, the charging roller being switchable between a spaced state in which it is spaced from the photosensitive drum and a contact state in which it is in contact with the photosensitive drum, the cam members comprising an annular mounting portion fitted onto the shaft portion of the charging roller, It is formed integrally with the mounting part, a contact portion that protrudes outward from the outer surface of the attachment portion; the contact portion has a leaf spring shape that is elastically deformable in the direction of contact and separation of the charge roller, and includes a protruding portion that protrudes from the outer surface of the mounting portion and an arm portion that extends in the circumferential direction of the mounting portion so as to follow the outer surface of the mounting portion with a gap between the tip of the protruding portion and the outer surface of the mounting portion, and urges the drum body in the direction away from the charge roller when the charge roller is in the separated state; This process unit maintains the charging roller in a spaced-apart state by bringing the contact portion of the cam member into contact with the outer surface of the drum body, and as the photosensitive drum rotates forward, the frictional force between the drum body and the contact portion causes the cam member to rotate in the forward direction, thereby releasing the contact portion from the drum body and switching the charging roller from a spaced-apart state to a contact state.

[0008] According to the first aspect of the present invention, the charging roller can be appropriately moved toward and away from the photosensitive drum with a simple configuration in which a cam member is provided on the shaft of the charging roller. In addition, since the cam member is provided at a position that fits within the longitudinal range of the drum body of the photosensitive drum, it is possible to prevent the process unit from becoming large in size in the longitudinal direction. Furthermore, even if vibrations or shocks are applied to the process unit, the elasticity of the cam member can absorb the vibrations, etc. Therefore, when the charging roller is in the separated state, the contact portion of the cam member can be appropriately maintained in contact with the drum main body.

[0009] A second invention is dependent on the first invention, and the abutment surface of the abutment portion that abuts against the drum main body has a larger coefficient of friction than other portions of the cam member.

[0010] According to the second aspect of the present invention, when the charging roller is in the separated state, the cam member can be rotated more reliably in conjunction with the rotation of the photosensitive drum.

[0011] A third invention is according to the second invention, and the contact surface of the contact portion is formed by an elastic member.

[0012] A fourth invention is dependent on any one of the first to third inventions, and further comprises: a contact portion The arm portion is formed so as to extend from the tip of the protrusion toward the upstream side in the forward rotation direction of the charging roller. .

[0014] A fifth invention is dependent on any one of the first to fourth inventions, and the cam member has a grip portion for manually rotating the cam member. The gripping portion protrudes from the outer surface of the contact portion and functions as a restricting portion that restricts the reverse rotation of the cam member when the charging roller is in the separated state.

[0015] According to the fifth aspect of the present invention, the cam member can be easily rotated manually, and the charging roller can be easily switched between the separated state and the contact state.

[0016] The sixth invention is 5 dependent on the invention of The gripping portion protrudes from the outer surface of the base end of the abutting portion in a direction opposite to the extension direction of the arm portion, The forward rotation of the cam member is restricted when the charging roller is in contact with the cam member. It also functions as a regulator.

[0017] The seventh invention is 5th or 6th The cam member is In addition to the grip portion that functions as a restricting portion that restricts the rotation of the cam member, The charging roller has a second restricting portion that restricts the reverse rotation of the cam member when the charging roller is in contact with the cam member.

[0018] The eighth invention is dependent on any one of the first to seventh inventions and includes a cleaning roller that is detachably attached to the charging roller, and the cam member is formed to protrude outward from the outer surface of the mounting part at a position opposite to the abutment portion, and has a second abutment portion that can detachably attach the charging roller and the cleaning roller.

[0019] According to the eighth aspect of the present invention, the cleaning roller can be moved into and out of contact with the charging roller at the same time that the charging roller is moved into and out of contact with the photosensitive drum.

[0020] A ninth invention is according to any one of the first to eighth inventions, and when the charging roller rotates forward, the rotation of the charging roller is not transmitted to the cam member, and when the charging roller rotates reversely, the rotation of the charging roller is transmitted to the cam member. do The device is equipped with a one-way clutch, and when the charging roller is in a contact state, the charging roller and the cam member are rotated in the reverse direction by rotating the photosensitive drum in the reverse direction, thereby bringing the contact portion of the cam member into contact with the outer surface of the drum body, thereby switching the charging roller from a contact state to a separated state.

[0021] According to the ninth aspect of the present invention, the charging roller can be automatically switched from the contact state to the separated state by rotating the photosensitive drum in the reverse direction.

[0022] A tenth aspect of the present invention is an image forming apparatus including a process unit according to any one of the first to ninth aspects of the present invention. [Effects of the Invention]

[0023] According to this invention, the charging roller can be appropriately moved toward and away from the photosensitive drum with a simple configuration in which a cam member is provided on the shaft of the charging roller. In addition, since the cam member is provided at a position that fits within the longitudinal range of the drum body of the photosensitive drum, it is possible to prevent the process unit from becoming large in size in the longitudinal direction.

[0024] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments, which proceeds with reference to the accompanying drawings. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a diagram schematically illustrating the internal structure of an image forming apparatus including a process unit according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a side view showing the process unit. [Figure 3] FIG. 2 is a bottom view showing the process unit. [Figure 4] FIG. 2 is a cross-sectional view showing a process unit. [Figure 5] FIG. 4 is a view showing the periphery of a cam member of the process unit. [Figure 6] FIG. [Figure 7] FIG. [Figure 8] FIG. [Figure 9] FIG. 4 is a cross-sectional view showing the periphery of the cam member when the charging roller is in a separated state. [Figure 10] FIG. 4 is a cross-sectional view showing the periphery of the cam member when the charging roller is in contact with the cam member. [Figure 11] FIG. 6 is a cross-sectional view showing the periphery of a cam member of a process unit according to a second embodiment of the present invention. [Figure 12] FIG. 10 is a cross-sectional view showing the periphery of a cam member of a process unit according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] [First Example] 1, process unit 60 according to the first embodiment of the present invention integrates photosensitive drum 36, cleaning unit 38, charging unit 40, etc., and is detachably mounted on apparatus body 12 of image forming apparatus 10. As will be described in detail later, process unit 60 includes cam member 80, and charging roller 68 of charging unit 40 can be maintained in a spaced state away from photosensitive drum 36 by cam member 80.

[0027] In this specification, the front-to-rear direction (depth direction) of image forming apparatus 10 and its components is defined with the surface facing the position of a user who operates image forming apparatus 10, i.e., the surface on which an operation unit (not shown) is provided, as the front (front). The operation unit is provided on the near side of the paper in Fig. 1. The left-to-right direction (horizontal direction) of image forming apparatus 10 and its components is defined with reference to the state when image forming apparatus 10 is viewed from the front side.

[0028] First, we will briefly explain the configuration of image forming apparatus 10. As shown in Figure 1, image forming apparatus 10 is a monochrome multifunction machine that has functions such as copying, printing, scanning, and facsimile, and forms monochrome images on paper (recording media) using an electrophotographic method. Image forming apparatus 10 includes a device main body 12 and an image reading device 14 disposed above it.

[0029] The image reading device 14 includes a document table 16 made of a transparent material. A document retaining cover 18 is attached above the document table 16 via a hinge or the like so that it can be opened and closed freely. This document retaining cover 18 is provided with an ADF 24 (automatic document feeder) that automatically feeds documents placed on a document tray 20 one by one to an image reading position 22. In addition, an operation unit is provided on the front side of the document table 16 for receiving input operations such as a print start command from the user. The operation unit is provided with a touch panel display, various operation buttons, etc.

[0030] The image reading device 14 also includes an image reading unit 26 equipped with a light source, multiple mirrors, an imaging lens, a line sensor, etc. The image reading unit 26 exposes the surface of the document to light, and guides the light reflected from the document surface to the imaging lens via multiple mirrors. The imaging lens then forms an image of the reflected light on the light-receiving elements of the line sensor. The line sensor detects the luminance and chromaticity of the reflected light that forms an image on the light-receiving elements, and generates image data based on the image of the document surface. A CCD (Charge Coupled Device) or a CIS (Contact Image Sensor) is used as the line sensor.

[0031] A control unit (not shown) including a CPU and memory, etc., and an image forming unit 30, etc. are provided within the device main body 12. The control unit transmits control signals to each part of the image forming device 10 in response to input operations to the operation unit, etc., and causes the image forming device 10 to perform various operations.

[0032] The image forming section 30 includes an exposure unit 32, a developing unit 34, a photosensitive drum 36, a cleaning unit 38, a charging unit 40, a transfer roller 42, a fixing unit 44, a toner supply device 46, etc., and forms an image on paper transported from a paper feed tray 48, etc., and discharges the paper with the image formed on it to a paper discharge tray 50. Image data used to form an image on paper is image data read by the image reading section 26 or image data sent from an external computer, etc.

[0033] The photosensitive drum 36 is an image carrier having a drum main body 36a (see FIG. 2) with a photosensitive layer formed on its surface, and is provided so as to extend in the front-to-rear direction. The charging unit 40 includes a charging roller 68 and a cleaning roller 70 (see FIG. 4), and charges the surface of the photosensitive drum 36 (drum main body 36a) to a predetermined potential. The cleaning unit 38 removes toner remaining on the surface of the photosensitive drum 36 after development and image transfer. The photosensitive drum 36, cleaning unit 38, and charging unit 40 are integrated (formed into a cartridge), and together they constitute a process unit 60. The process unit 60 can be attached and detached from the front side of the apparatus main body 12. The specific configuration of the process unit 60 will be described later.

[0034] The exposure unit 32 is configured as a laser scanning unit (LSU) equipped with a laser diode, a polygon mirror, etc., and is disposed a predetermined distance to the left of the photosensitive drum 36. The exposure unit 32 exposes the charged surface of the photosensitive drum 36 to light, thereby forming an electrostatic latent image on the surface of the photosensitive drum 36 according to image data. The development unit 34 is equipped with a developer tank, a development roller, etc., and is disposed below the photosensitive drum 36. The development unit 34 supplies toner to the surface of the photosensitive drum 36 and visualizes the electrostatic latent image formed on the surface of the photosensitive drum 36 with the toner (forming a toner image).

[0035] The transfer roller 42 is a member for transferring the toner image formed on the surface of the photosensitive drum 36 onto paper, and is provided so as to press against the photosensitive drum 36. During image formation, a predetermined voltage is applied to the transfer roller 42, thereby forming a transfer electric field between the photosensitive drum 36 and the transfer roller 42. Then, due to the action of this transfer electric field, the toner image formed on the outer peripheral surface of the photosensitive drum 36 is transferred onto the paper as the paper passes through the nip region (transfer nip portion) between the photosensitive drum 36 and the transfer roller 42.

[0036] The fixing unit 44 includes a heating roller, a pressure roller, etc., and is disposed above the process unit 60 and the transfer roller 42. The heating roller is heated to a predetermined fixing temperature by an internal heat source. When a sheet of paper passes through the nip region (fixing nip) between the heating roller and the pressure roller, the toner image transferred to the sheet of paper is melted, mixed, and pressed against the sheet, thereby thermally fixing the toner image to the sheet of paper.

[0037] Also formed within the device body 12 is a first paper transport path L1 for sending paper transported from the paper feed tray 48 or the like to a paper output tray 50 (paper output section) via registration rollers 52, a transfer nip section, and a fixing nip section. Also formed is a second paper transport path L2 for returning paper that has been printed on one side and passed through the fixing unit 44 to the first paper transport path L1 upstream of the transfer nip section in the paper transport direction when double-sided printing is performed on the paper. A plurality of transport rollers 54 for applying auxiliary propulsion force to the paper are appropriately provided on the first paper transport path L1 and the second paper transport path L2.

[0038] Next, a specific description will be given of the configuration of the process unit 60. As shown in Figures 2 to 4, the process unit 60 includes a photosensitive drum 36, a cleaning unit 38, a charging unit 40, etc., which are integrally held in a predetermined arrangement by a process frame 62.

[0039] The photosensitive drum 36 includes a drum body 36a, which is a cylindrical conductive substrate with a photosensitive layer formed on its surface. Flanges are fixedly fitted to both ends of the substrate, and a metal drum shaft 36b is provided to pass through the center of the flange. Both ends of the drum shaft 36b are rotatably supported by bearings provided in the process frame 62. Although not shown, a drive motor is connected to the rear end of the drum shaft 36b via a coupling, a gear train, and the like. The drum body 36a rotates in conjunction with the rotation of the drum shaft 36b. In other words, the photosensitive drum 36 is rotatably supported around the drum shaft 36b by the process frame 62 and rotates due to the driving force transmitted from the drive motor.

[0040] The cleaning unit 38 includes a cleaning blade 64 and a conveying member 66. The cleaning unit 38 removes foreign matter such as toner remaining on the surface of the photosensitive drum 36 with the cleaning blade 64, and sends the removed foreign matter to a waste toner box with the conveying member 66.

[0041] The charging unit 40 includes a charging roller 68, a cleaning roller 70, and the like. The charging roller 68 includes a shaft portion 68a, which is a cylindrical (round rod-shaped) conductive support made of a metal such as iron. A roller portion 68b, including an elastic layer and a resistive layer, is formed on the outer circumferential surface of the shaft portion 68a, excluding both ends. The elastic layer is made of a material with appropriate conductivity and elasticity to supply power to the photoreceptor drum 36, which is a non-charged body, and to ensure good, uniform adhesion with the photoreceptor drum 36. The resistive layer is provided to prevent bleed-out of softening oil, plasticizer, and the like contained in the elastic layer and to adjust the electrical resistance of the entire charging roller 68. It is made of a conductive or semi-conductive material.

[0042] The roller portion 68b of the charging roller 68 has an axial length that is slightly smaller than that of the drum main body 36a of the photosensitive drum 36. The shaft portion 68a of the charging roller 68 is disposed parallel to the drum shaft 36b of the photosensitive drum 36. The charging roller 68 charges the surface of the photosensitive drum 36 (drum main body 36a) to a predetermined potential while rotating in accordance with the rotation of the photosensitive drum 36, with the outer surface of the roller portion 68b abutting (contacting) the outer surface of the drum main body 36a with a predetermined pressure.

[0043] Although not shown, both ends of the shaft portion 68a of the charging roller 68 are rotatably supported by bearings. These bearings are attached to the frame in a state in which they are movable in the radial direction of the photosensitive drum 36. That is, the charging roller 68 supported by these bearings is movable (separable) in the radial direction of the photosensitive drum 36 and is provided so as to be switchable between a spaced state in which it is spaced from the photosensitive drum 36 and a contact state in which it is in contact with the photosensitive drum 36. Furthermore, a biasing member such as a compression coil spring is provided on the bearing. This biasing member is a member for bringing the charging roller 68 into contact with the photosensitive drum 36 with a predetermined pressure, and biases the charging roller 68 toward the photosensitive drum 36 via the bearing.

[0044] The cleaning roller 70 is disposed on the opposite side of the photosensitive drum 36 so as to contact the outer circumferential surface of the charging roller 68 (roller portion 68b). The cleaning roller 70 comprises a cylindrical metal shaft and an elastic foam (sponge layer) covering the outer circumferential surface of the metal shaft, and removes foreign matter such as toner adhering to the outer circumferential surface of the charging roller 68. The cleaning roller 70 is disposed so as to be able to come into contact with and separate from the charging roller 68, and is brought into contact with the charging roller 68 at a predetermined pressure by a biasing member (not shown).

[0045] In such a process unit 60, it may take a long time from the time the image forming apparatus 10 or process unit 60 is shipped until it can be put into use. If the photosensitive drum 36 and the charging roller 68 remain in contact during this period, there is a concern that poor image quality may occur due to bleeding or deformation of the charging roller 68. For this reason, it is conceivable to provide the process unit 60 with a mechanism that separates the photosensitive drum 36 and the charging roller 68 when the image forming apparatus 10 or process unit 60 is shipped and then brings the photosensitive drum 36 and the charging roller 68 into contact when use begins. However, it is preferable that such a mechanism be realized with as simple a structure as possible.

[0046] Therefore, in this first embodiment, by providing the process unit 60 with a cam member 80 described below, it is possible to keep the charging roller 68 separated from the photosensitive drum 36 with a simple structure, and also to automatically bring the charging roller 68 into contact with the photosensitive drum 36 when use begins. This will be explained in detail below.

[0047] 3 and 5, cam members 80 are rotatably provided on both ends of shaft portion 68a of charging roller 68 (i.e., on both sides of roller portion 68b, which is the photosensitive drum charging area). Cam members 80 are provided at positions that fit within the longitudinal range of drum main body 36a of photosensitive drum 36.

[0048] 6 to 8, the cam member 80 is a member used as a spacer for keeping the charging roller 68 spaced apart from the photosensitive drum 36, and includes an attachment portion 82 and an abutment portion 84. The material from which the cam member 80 is made is not particularly limited, but it is preferably made of a soft material such as synthetic resin or rubber in order to elastically deform the abutment portion 84 and to prevent damage to the photosensitive drum 36.

[0049] The mounting portion 82 is formed in an annular (ring-like) shape and is fitted onto the shaft portion 68a of the charging roller 68. The thickness of the mounting portion 82 is set to be smaller than the thickness of the roller portion 68b of the charging roller 68.

[0050] The contact portion 84 is a portion that holds the charge roller 68 in a spaced-apart state by contacting the outer surface of the drum main body 36a (specifically, the photosensitive layer) of the photosensitive drum 36, and is formed to protrude outward from the outer surface of the mounting portion 82. The contact portion 84 has a leaf spring shape that is elastically deformable in the direction in which the charge roller 68 is contacted or separated, and is able to urge the drum main body 36a in a direction away from the charge roller 68. Specifically, the contact portion 84 has a protruding portion 84a that protrudes from the outer surface of the mounting portion 82, and a curved plate-like arm portion 84b that bends from the tip of the protruding portion 84a and extends along the outer surface of the mounting portion 82. The arm portion 84b is displaceable in the direction in which the charge roller 68 is contacted or separated, with its base end as a fulcrum, and the outer surface of the tip of the arm portion 84b forms a contact surface 84c with the drum main body 36a. By forming the contact portion 84 to be elastically deformable in this manner, even if vibrations or impacts are applied to the process unit 60, the elasticity can absorb the vibrations, etc. Therefore, unintentional rotation of the cam member 80 can be prevented, and the contact portion 84 can be appropriately maintained in contact with the drum main body 36a (i.e., in a separated state).

[0051] The thickness of the arm portion 84b of the contact portion 84 is set so that the thickness thereof, when added to the thickness of the mounting portion 82, is greater than the thickness of the roller portion 68b of the charging roller 68. This makes it possible to maintain the charging roller 68 in a separated state even if the contact portion 84 is completely crushed (i.e., the arm portion 84b is in contact with the mounting portion 82) due to changes over time caused by long-term pressure contact or elastic deformation caused by the application of vibration or impact.

[0052] The cam member 80 also has a rectangular plate-shaped grip portion 86 for manually rotating the cam member 80. The grip portion 86 is formed to protrude from the outer surface of the base end of the abutment portion 84. A user can easily switch the charge roller 68 between the separated state and the abutment state by gripping this grip portion 86 and rotating the cam member 80. The grip portion 86 also functions as a first regulating portion that regulates the reverse rotation of the cam member 80 when the charge roller 68 is in the separated state and the forward rotation of the cam member 80 when the charge roller 68 is in the abutment state.

[0053] Furthermore, the cam member 80 has a second restricting portion 88 that restricts reverse rotation of the cam member 80 when the charging roller 68 is in a contacting state. The second restricting portion 88 has a leaf spring shape that is elastically deformable in the radial direction of the mounting portion 82, and has a protruding portion 88a that protrudes from the outer surface of the mounting portion 82, and a curved rod-shaped arm portion 88b that bends from the tip of the protruding portion 88a and extends along the outer surface of the mounting portion 82. In addition, a notch 90 is formed in the mounting portion 82 and the contact portion 84 at a position corresponding to the arm portion 88b. This notch 90 allows the second restricting portion 88 to enter when it elastically deforms radially inward.

[0054] Furthermore, although not shown, the contact surface 84c of the contact portion 84 can be formed to have a greater coefficient of friction (grip force) than other portions of the cam member 80. For example, the coefficient of friction of the contact surface 84c can be increased by forming the contact surface 84c from an elastic material such as urethane rubber (i.e., by attaching an elastic material to the outer surface of the tip of the arm portion 84b). Alternatively, the coefficient of friction of the contact surface 84c can be increased by forming the contact surface 84c into a rough surface. This allows the cam member 80 to rotate more reliably in conjunction with the rotation of the photosensitive drum 36 when the contact surface 84c is in contact with the drum main body 36a.

[0055] Next, the operation of the process unit 60 including such a cam member 80 will be described with reference to Figures 9 and 10. As shown in Figure 9, at the time of shipment or the like, the cam member 80 is held in a rotational position (separately held position) in which the contact portion 84 contacts the drum main body 36a (specifically, the photosensitive layer) of the photosensitive drum 36. In this state, the contact portion 84 presses the drum main body 36a, so that the charging roller 68 is held in a spaced state away from the photosensitive drum 36 against the biasing force of the biasing member. In addition, in this spaced state, the tip end of the grip portion 86 (first restricting portion) contacts the drum main body 36a, so that rotation of the cam member 80 in the reverse direction (counterclockwise in Figures 9 and 10) is restricted.

[0056] Furthermore, when the image forming apparatus 10 is started to be used and the photosensitive drum 36 rotates in the forward direction (counterclockwise in FIGS. 9 and 10), the cam member 80 is driven to rotate in the forward direction (clockwise in FIGS. 9 and 10) due to the frictional force between the contact surface 84c of the contact portion 84 and the drum main body 36a. Then, as shown in FIG. 10, the contact portion 84 is released from contact with the drum main body 36a, and the charging roller 68 is brought into contact with the photosensitive drum 36 by the biasing force of the biasing member. In other words, the charging roller 68 is switched from the separated state to the contact state. In this contact state, the outer surface of the mounting portion 82 of the cam member 80 (the portion where the contact portion 84 and the like are not formed) is positioned opposite the photosensitive drum 36, so the cam member 80 does not contact the photosensitive drum 36. Therefore, even when the photosensitive drum 36 rotates, the cam member 80 does not rotate.

[0057] Furthermore, in this contact state, the tip of the grip portion 86 (first restricting portion) is locked by a first locking portion 94 formed on the frame side, thereby restricting forward rotation of the cam member 80. Furthermore, the tip of the second restricting portion 88 of the cam member 80 is locked by a second locking portion 96 formed on the frame side, thereby restricting reverse rotation of the cam member 80. In other words, when the charging roller 68 is in the contact state, the forward and reverse rotation of the cam member 80 is restricted so that the cam member 80 remains in a rotation position (non-contact position) where it does not contact the photosensitive drum 36, and therefore the contact state of the charging roller 68 is appropriately maintained.

[0058] When it is desired to switch the charging roller 68 from the contact state to the separated state, it is advisable to grip the grip portion 86 of the cam member 80 and manually rotate the cam member 80 in the reverse direction.

[0059] As described above, according to the first embodiment, the charging roller 68 can be appropriately moved toward and away from the photosensitive drum 36 with a simple configuration in which the cam member 80 is provided on the shaft portion 68a of the charging roller 68. Furthermore, since the cam member 80 is provided at a position that fits within the longitudinal range of the drum main body 36a of the photosensitive drum 36, it is possible to prevent the process unit 60 from becoming large in size in the longitudinal direction.

[0060] [Second Example] Next, a process unit 60 according to a second embodiment of the present invention will be described with reference to Figure 11. This second embodiment differs from the first embodiment in that the process unit 60 includes a one-way clutch 100. Since the other parts are similar, the same reference numerals are used for parts common to the first embodiment, and redundant explanations will be omitted or simplified.

[0061] As shown in FIG. 11 , in the second embodiment, the process unit 60 is provided with a one-way clutch 100 that does not transmit the rotation of the charging roller 68 to the cam member 80 when the charging roller 68 rotates forward (clockwise in FIG. 11 ), and that does not transmit the rotation of the charging roller 68 to the cam member 80 when the charging roller 68 rotates reversely (counterclockwise in FIG. 11 ). Simply put, in this second embodiment, a ratchet-type one-way clutch 100 is used. This one-way clutch 100 is composed of a gear member attached to the shaft portion 68a of the charging roller 68 and a pawl member attached to the cam member 80. However, the one-way clutch 100 is not limited to the ratchet type, and other types, such as a sprag type, can also be used.

[0062] In the process unit 60 equipped with such a one-way clutch 100, the charging roller 68 can be switched from a contact state to a separated state by rotating the photosensitive drum 36 in the reverse direction. That is, when the charging roller 68 is in the contact state, the charging roller 68 and the cam member 80 are rotated in the reverse direction by rotating the photosensitive drum 36 in the reverse direction (clockwise in FIG. 11). Then, the contact portion 84 of the cam member 80 is brought into contact with the outer surface of the drum main body 36a, thereby switching the charging roller 68 to the separated state.

[0063] In the second embodiment, similarly to the first embodiment, the charging roller 68 can be appropriately brought into contact with and separated from the photosensitive drum 36 with a simple configuration.

[0064] Furthermore, according to the second embodiment, the charging roller 68 can be automatically switched from the contact state to the separated state by rotating the photosensitive drum 36 in the reverse direction.

[0065] [Third Example] Next, a process unit 60 according to a third embodiment of the present invention will be described with reference to Figure 12. In this third embodiment, the configuration of the cam member 80 differs from that of the first embodiment. Since the other parts are similar, the same reference numerals are used for parts common to the first embodiment, and redundant explanations will be omitted or simplified.

[0066] As shown in FIG. 11, in the second embodiment, when the charging roller 68 rotates forward (clockwise in FIG. 11), the process unit 60 does not transmit the rotation of the charging roller 68 to the cam member 80, and when the charging roller 68 rotates backward (counterclockwise in FIG. 11), the process unit 60 transmits the rotation of the charging roller 68 to the cam member 80. doThe second embodiment is provided with a one-way clutch 100. Simply put, in this second embodiment, a ratchet-type one-way clutch 100 is used. This one-way clutch 100 is made up of a gear member attached to the shaft portion 68a of the charging roller 68 and a pawl member attached to the cam member 80. However, the one-way clutch 100 is not limited to the ratchet-type, and other types such as a sprag-type can also be used.

[0067] In the third embodiment, similarly to the first embodiment, the charging roller 68 can be appropriately brought into contact with and separated from the photosensitive drum 36 with a simple configuration.

[0068] Furthermore, according to the third embodiment, the cleaning roller 70 can be moved into and out of contact with the charging roller 68 at the same time that the charging roller 68 is moved into and out of contact with the photosensitive drum 36 .

[0069] Note that the specific configurations of the image forming apparatus 10 described in this specification are merely examples and can be changed as appropriate depending on the specifications of the actual product. For example, the image forming apparatus does not necessarily have to be a multifunction machine, but may be any of a copier, facsimile, printer, etc., or a multifunction machine that combines at least two of these. Furthermore, the image forming apparatus is not limited to a monochrome machine, but may be a color machine capable of forming multicolor images.

[0070] Furthermore, the specific part shapes and dimensions given above are merely examples and can be changed as appropriate according to the needs of the product specifications, etc. [Explanation of symbols]

[0071] 10...Image forming device 12...Device body 14...Image reading device 30...Image forming unit 36...Photosensitive drum 38...Cleaning unit 40...Charging unit 60...Process unit 68...Charging roller 70...Cleaning roller 80...Cam member 82 ...Attachment part 84...Abutting part 86...Gripping part (first regulating part) 88...Second Regulatory Department 98...Second contact part

Claims

1. A process unit including a photosensitive drum and a charging roller that charges the photosensitive drum, a cam member rotatably provided on each end of the shaft of the charging roller at a position within a longitudinal range of the drum body of the photosensitive drum, the charging roller is provided so as to be switchable between a spaced state in which it is spaced from the photosensitive drum and a contact state in which it is in contact with the photosensitive drum, The cam member is a ring-shaped mounting portion fitted onto the shaft portion of the charging roller; and a contact portion formed integrally with the mounting portion and protruding outward from an outer surface of the mounting portion; the abutment portion has a leaf spring shape that is elastically deformable in the contact / separation direction of the charge roller, and includes a protruding portion that protrudes from the outer surface of the mounting portion, and an arm portion that extends in the circumferential direction of the mounting portion so as to follow the outer surface of the mounting portion with a gap between the tip of the protruding portion and the outer surface of the mounting portion, and urges the drum main body in a direction away from the charge roller when the charge roller is in the separated state, a process unit that holds the charging roller in the separated state by bringing the contact portion of the cam member into contact with the outer surface of the drum body, and that, in conjunction with the forward rotation of the photosensitive drum, causes the cam member to rotate in the forward direction due to friction between the drum body and the contact portion, thereby releasing the contact portion from contact with the drum body and switching the charging roller from the separated state to the contact state.

2. 2. The process unit according to claim 1, wherein a contact surface of said contact portion against said drum body has a coefficient of friction greater than that of other portions of said cam member.

3. 3. The process unit according to claim 2, wherein the contact surface of the contact portion is formed of an elastic material.

4. A process unit described in any one of claims 1 to 3, wherein the arm portion of the abutment portion is formed to extend from the tip of the protrusion toward the upstream side in the forward rotation direction of the charging roller.

5. the cam member has a grip portion for manually rotating the cam member, 5. The process unit according to claim 1, wherein the gripping portion protrudes from an outer surface of the contact portion and functions as a regulating portion that regulates reverse rotation of the cam member when the charging roller is in the separated state.

6. A process unit as described in claim 5, wherein the gripping portion protrudes from the outer surface of the base end of the abutment portion in a direction opposite to the direction in which the arm portion extends, and also functions as a regulating portion that regulates the forward rotation of the cam member when the charging roller is in the abutment state.

7. 7. The process unit according to claim 5, wherein the cam member has, in addition to the gripping portion that functions as a regulating portion that regulates rotation of the cam member, a second regulating portion that regulates reverse rotation of the cam member when the charging roller is in the contact state.

8. a cleaning roller provided so as to be movable toward and away from the charging roller; 8. The process unit according to claim 1, wherein the cam member has a second contact portion formed to protrude outward from the outer surface of the mounting portion at a position opposite the contact portion, and capable of contacting and separating the charging roller and the cleaning roller.

9. a one-way clutch that does not transmit the rotation of the charging roller to the cam member when the charging roller rotates forward, and transmits the rotation of the charging roller to the cam member when the charging roller rotates backward, 9. The process unit according to claim 1, wherein when the charging roller is in the contact state, the charging roller can be switched from the contact state to the separated state by rotating the photosensitive drum in the reverse direction, thereby rotating the charging roller and the cam member in the reverse direction and bringing the contact portion of the cam member into contact with the outer surface of the drum body.

10. An image forming apparatus comprising the process unit according to any one of claims 1 to 9.

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