Pressure mechanism, process cartridge, and image forming apparatus

Abstract

To make appropriate the pressure applied to a pressing body against an object relatively easily even after the lapse of time.SOLUTION: A pressure mechanism applies pressure to a developing device 5 (pressing body) against a photoreceptor drum 1 (object), and is provided with a compression spring 33 that is in direct or indirect contact with the developing device 5 at one end and urges the developing device 5 toward the photoreceptor drum 1 in a predetermined urging direction. The pressure mechanism is further provided with a support member 32 that supports the other end of the compression spring 33, and a holding member 31 that holds the support member 32. The holding member 31 has a plurality of holding parts 31b-31d arranged at different positions around the support member 32 for holding the support member 32 at positions in different urging directions.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a pressure mechanism that pressurizes a pressure body such as a developing device against a target body such as a photosensitive drum, and to a process cartridge and an image forming apparatus that are provided with the pressure mechanism. [Background technology]

[0002] Conventionally, image forming devices such as copiers, printers, and facsimiles have been known to be equipped with a pressure mechanism (biasing mechanism) that applies pressure to a developing device (pressure body) toward a photosensitive drum (target body) (see, for example, Patent Document 1).

[0003] On the other hand, Patent Document 1 discloses a technology for controlling a cam mechanism that urges the developing roller against the photosensitive drum based on information stored in a memory element, with the aim of optimizing the operating conditions of the photosensitive drum and the developing roller regardless of the usage time of the process cartridge. Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional pressure mechanisms, it has been difficult to constantly apply an appropriate amount of pressure to a pressing body, such as a developing device, which becomes lighter over time as toner is consumed, against a target body, such as a photosensitive drum. In response to this, it is possible to automatically control the pressure applied by the pressure mechanism by applying the technology of Patent Document 1. However, in this case, the configuration and control of the pressure mechanism become complicated, and the pressure mechanism becomes expensive and large in size.

[0005] The present invention has been made to solve the above-mentioned problems, and aims to provide a pressure mechanism, a process cartridge, and an image forming apparatus that can relatively easily optimize the pressure of a pressure body against a target body even over time. [Means for solving the problem]

[0006] The pressure applying mechanism of the present invention is a pressure applying mechanism for applying pressure to a target body, and comprises a compression spring having one end that directly or indirectly contacts the pressure applying body and applies pressure to the pressure applying body in a predetermined applying direction toward the target body, a support member that supports the other end of the compression spring, and a holding member that holds the support member, wherein the holding member has a plurality of holding portions for holding the support member at positions in different applying directions, the holding member being arranged at different positions around the support member. Effect of the Invention

[0007] According to the present invention, it is possible to provide a pressure mechanism, a process cartridge, and an image forming apparatus that can relatively easily optimize the pressure of a pressure member applied to a target body even over time. [Brief description of the drawings]

[0008] [Figure 1] 1 is an overall configuration diagram showing an image forming apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a schematic view illustrating a process cartridge. [Diagram 3] FIG. 2 is a perspective view showing the vicinity of a pressure mechanism in the process cartridge. [Figure 4] FIG. 4 is a perspective view showing a state in which a compression spring is attached to a support member. [Diagram 5] 1A is a perspective view of the support member as viewed obliquely from above, and FIG. 1B is a perspective view of the support member as viewed obliquely from below. [Figure 6] 4 is a perspective view showing a portion of the case member that functions as a holding member. FIG. [Figure 7] FIG. [Figure 8] 1A is a perspective view showing an operation in which a support member is moved to and held by a first holding portion, and FIG. 1B is a perspective view showing an operation in which a support member is moved to and held by a second holding portion. [Figure 9] FIG. 11 is a top view showing a holding member as a first modified example. [Figure 10]10A is a top view of the holding member in FIG. 9 showing a state in which the support member is held by a first holding portion, and FIG. 10B is a top view of the holding member in FIG. 9 showing a state in which the support member is held by a second holding portion. [Figure 11] FIG. 11 is a top view showing a holding member as a second modified example. [Figure 12] 12A, 12B, and 12C are a top view, a front view, and a side view, respectively, showing a support member held by the holding member in FIG. 11. [Figure 13] 12A and 12B are a top view and a side view, respectively, showing an operation in which a supporting member is set in a first holding portion of the holding member in FIG. 11. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and the duplicated description will be appropriately simplified or omitted.

[0010] First, the overall configuration and operation of an image forming apparatus 100 will be described with reference to FIG. In FIG. 1, reference numeral 100 denotes a printer as an image forming apparatus, 1 denotes a photosensitive drum (image carrier) as an object on whose surface a toner image is formed, and 7 denotes an exposure section (writing section) that irradiates exposure light L onto the photosensitive drum 1 based on image information input from an input device such as a personal computer. Also, reference numeral 9 denotes a transfer roller that transfers the toner image carried on the surface of the photosensitive drum 1 onto a sheet P transported to a transfer nip portion (transfer position), reference numeral 10 denotes a process cartridge in which the photosensitive drum 1, charging roller 4, developing device 5 (pressure body), and cleaning device 2 are integrated, and reference numeral 12 denotes a paper feed device (paper feed cassette) in which sheets P such as paper are stored. In addition, reference numeral 16 denotes a registration roller (timing roller) that transports sheet P toward the transfer nip portion where the photosensitive drum 1 and transfer roller 9 abut, reference numeral 20 denotes a fixing device that fixes an unfixed image on sheet P, reference numeral 21 denotes a fixing roller installed in fixing device 20, and reference numeral 22 denotes a pressure roller installed in fixing device 20.

[0011] Here, a charging roller 4, a developing device 5, a cleaning device 2, etc. are arranged around the photosensitive drum 1. These members (the photosensitive drum 1, the charging roller 4, the developing device 5, and the cleaning device 2) are integrated as a process cartridge 10, and are installed in a detachable (replaceable) manner with respect to the image forming apparatus main body 100. The process cartridge 10 is replaced with a new one at a fixed replacement cycle. More specifically, the developing device 5 contains toner (new toner) as a developer. When the toner contained inside the developing device 5 eventually runs out due to consumption of the toner in the developing device 5 accompanying the printing operation, the process cartridge 10 is replaced with a new one.

[0012] 1 and 2, the operation of the image forming apparatus 100 during normal image formation will be described. Referring to FIG. 1, first, when image information is sent from an input device such as a personal computer to an exposure unit 7 of an image forming apparatus 100, exposure light L (laser light) based on the image information is emitted from the exposure unit 7 toward the surface of a photosensitive drum 1. Meanwhile, the photoconductor drum 1 rotates in the direction of the arrow (clockwise). First, the surface of the photoconductor drum 1 is uniformly charged at the portion facing the charging roller 4 (charging process). In this way, a charging potential (about -900V) is formed on the photoconductor drum 1. Thereafter, the charged surface of the photoconductor drum 1 reaches the irradiation position of the exposure light L. Then, the potential of the portion irradiated with the exposure light L becomes a latent image potential (about 0 to -100V), and an electrostatic latent image is formed on the surface of the photoconductor drum 1 (exposure process).

[0013] Thereafter, the surface of the photoconductor drum 1 on which the electrostatic latent image has been formed reaches a position facing the developing device 5. Then, toner is supplied from the developing device 5 onto the photoconductor drum 1, and the latent image on the photoconductor drum 1 is developed to form a toner image (this is the developing process).

[0014] 2, the developing device 5 is of a contact type one-component developing system, and is composed of a developing roller 5a, a doctor blade 5b, a supply roller 5c, a first toner transport screw 5d, a second toner transport screw 5e, etc. The developing device 5 contains toner (one-component developer). The toner in the developing device 5 is stirred and transported by the first and second toner transport screws 5d and 5e. The toner in the developing device 5 is pumped up by the supply roller 5c and supplied to the developing roller 5a while being triboelectrically charged by the sliding contact between the supply roller 5c and the developing roller 5a. The toner supplied to the developing roller 5a is adjusted to an appropriate amount by the doctor blade 5b and then reaches a contact position (developing area) with the photosensitive drum 1. At this time, the toner on the developing roller 5a is triboelectrically charged by the sliding contact with the doctor blade 5b. In the developing area, the adjusted amount of toner adheres to the electrostatic latent image on the photosensitive drum 1, and a toner image is formed on the photosensitive drum 1. The developing roller 5a, the supply roller 5c, and the two toner transport screws 5d and 5e are driven by a drive motor installed in the image forming apparatus main body 100, and are each rotated in the direction of the arrow in FIG. 2.

[0015] Thereafter, the surface of the photoconductor drum 1 after the development process reaches a transfer nip portion (transfer position) with the transfer roller 9. Then, at the transfer nip portion with the transfer roller 9, a transfer bias (a bias with a polarity different from that of the toner) is applied from a power supply unit to the transfer roller 9, so that the toner image formed on the photoconductor drum 1 is transferred onto the sheet P conveyed by the registration roller 16 (this is the transfer process).

[0016] Then, after the transfer process, the surface of the photoreceptor drum 1 reaches a position facing the cleaning device 2. At this position, the untransferred toner remaining on the photoreceptor drum 1 is mechanically removed by the cleaning blade 2a and collected in the cleaning device 2 (cleaning process). Thus, a series of image forming processes on the photosensitive drum 1 is completed. The untransferred toner collected inside the cleaning device 2 is smoothed by a collection screw 2b provided inside the cleaning device 2.

[0017] On the other hand, the sheet P conveyed to the transfer nip portion (transfer position) between the photosensitive drum 1 and the transfer roller 9 behaves as follows. First, the uppermost sheet of the sheets P stored in the sheet feeder 12 is fed by the sheet feed roller 15 toward the conveyance path. Thereafter, the sheet P reaches the position of the registration rollers 16. Then, the sheet P that has reached the position of the registration rollers 16 is transported toward the transfer nip portion (the contact position between the transfer roller 9 and the photosensitive drum 1) in time for alignment with the image formed on the photosensitive drum 1.

[0018] After the transfer process, the sheet P passes through the transfer nip portion (transfer roller 9) and then travels through a transport path to reach the fixing device 20. The sheet P that has reached the fixing device 20 is fed between the fixing roller 21 and the pressure roller 22, and the image is fixed by the heat received from the fixing roller 21 and the pressure received from both members 21 and 22. The sheet P with the fixed image is sent out from between the fixing roller 21 and the pressure roller 22 (the fixing nip portion), and then discharged from the image forming apparatus main body 100 and placed on the paper discharge tray. In this way, a series of image forming processes is completed.

[0019] The pressure mechanisms 31 to 33, which are characteristic of the process cartridge 10 (image forming apparatus 100) in this embodiment, will be described in detail below. 2, 3, etc., pressure mechanisms 31 to 33 in this embodiment are for applying pressure (biasing) to photosensitive drum 1 as a target body, developing device 5 (developing roller 5a) as a pressure body. The pressure mechanism is composed of a compression spring 33, a support member 32, a holding member 31, and the like.

[0020] One end of the compression spring 33 directly (or indirectly via another member) contacts the developing device 5 (pressurizing body), and urges the developing device 5 in a predetermined urging direction (pressurizing direction) toward the photosensitive drum 1 (target body). In detail, the developing device 5 is held by a case member 30 (housing) of the process cartridge 10 so as to be swingable (rotatable) about a support shaft 30a provided in the case member 30 (housing).

[0021] As shown in FIGS. 3 and 4, the support member 32 supports the other end of the compression spring 33. In detail, the support member 32 is provided with a cylindrical portion 32a and a plurality of protruding portions 32b (seat portions). The cylindrical portion 32a is formed with a recess 32a1 into which the other end of the compression spring 33 is inserted, and an operating portion 32a2 (cross-shaped hole) for inserting a jig such as a screwdriver to rotate the support member 32 when assembling the support member 32 to the holding member 31. The operating portion 32a2 is formed on the surface of the cylindrical portion 32a opposite to the recess 32a1 (the lower surface in the assembled state). Moreover, the multiple protrusions 32b (at least two protrusions 32b) protrude from the circumference of the cylindrical portion 32a in a generally fan-like shape in the radial direction and are arranged at equal intervals in the circumferential direction. Specifically, in this embodiment, the two protrusions 32b are arranged at equal intervals with a phase shift of 180° in the circumferential direction so as to protrude horizontally from the outer circumferential surface of the cylindrical portion 32a.

[0022] 3 and other figures, the holding member 31 holds the support member 32 and functions as a part of the case member 30 of the process cartridge 10. The case member 30 holds the photosensitive drum 1 (target body) and also holds the developing device 5 (pressure body) so that it can swing about a support shaft 30a, and the holding members 31 are integrally formed at both ends in the longitudinal direction of the case member 30. The holding member 31 is formed with a hole 31a and a plurality of pairs of holding portions 31b to 31d, which will be described in detail later with reference to Figs.

[0023] The pressure mechanisms 31-33 thus configured urge the developing device 5 in the process cartridge 10 toward the photosensitive drum 1 (rotating counterclockwise around the support shaft 30a in FIG. 2), so that the developing roller 5a comes into contact with the photosensitive drum 1 with a predetermined contact pressure. In this embodiment, the pressure mechanisms 31 to 33 are provided independently at both ends in the longitudinal direction (the direction perpendicular to the paper surface of FIG. 2) of the process cartridge 10. This allows the developing roller 5a (developing device 5) to be pressed against the photosensitive drum 1 in a well-balanced manner over the longitudinal direction.

[0024] Here, in the pressure application mechanism in this embodiment, the holding member 31 (case member 30) has a plurality of holding portions (in this embodiment, three pairs of holding portions 31b to 31d) for holding the support member 32 at positions in different force directions, which are arranged at different positions around the support member 32. In detail, referring to Figs. 6 to 8 etc., holding member 31 (case member 30) is provided with hole 31a and a plurality of holding portions 31b to 31d. The hole 31a is a portion into which the cylindrical portion 32a of the support member 32 is inserted (fitted), and penetrates the case member 30 in the biasing direction (up and down direction). The three pairs of retaining portions 31b to 31d are arranged in steps so that their positions in the biasing direction are different, and are arranged circumferentially around the hole portion 31a with a phase shift, and are configured to be able to retain a plurality of protrusions 32b (at least two protrusions).

[0025] More specifically, of the three holding portions 31b to 31d, the first holding portion 31b is formed on the most upstream side (lowest position) in the biasing direction. The first holding portions 31b are formed to extend radially from the periphery of the hole portion 31a in a substantially fan-like shape, and are disposed at equal intervals in the circumferential direction. Specifically, in this embodiment, a pair of first holding portions 31b are disposed at equal intervals with a phase difference of 180° in the circumferential direction. Moreover, the first holding portions 31b are formed in the same plane as the plane in which the hole portion 31a opens.

[0026] The second retaining portion 31c is disposed adjacent to the first retaining portion 31b in the circumferential direction. The second retaining portion 31c is located downstream (higher) in the biasing direction than the first retaining portion 31b. The second retaining portions 31c are also formed to extend radially from the periphery of the hole portion 31a in a substantially fan-like shape, and are disposed at equal intervals in the circumferential direction. Specifically, in this embodiment, a pair of second retaining portions 31c are disposed at equal intervals with a phase shift of 180° in the circumferential direction.

[0027] The third retaining portion 31d is disposed adjacent to the second retaining portion 31c in the circumferential direction (the "opposite direction" described below, which is the clockwise direction in FIG. 7). The third retaining portion 31d is located downstream (at a higher position) in the biasing direction than the second retaining portion 31c. The third retaining portions 31d are also formed to extend radially from the periphery of the hole portion 31a in a substantially fan-like shape, and are disposed at equal intervals in the circumferential direction. Specifically, in this embodiment, a pair of third retaining portions 31d are disposed at equal intervals with a phase shift of 180° in the circumferential direction.

[0028] In this manner, the first to third retaining portions 31b to 31d are sequentially arranged in the clockwise direction in FIG. 7, and are formed so that the height in the biasing direction increases as they are arranged clockwise with the first retaining portion 31b as the reference. Therefore, when the support member 32 is held by the holding member 31 (case member 30) with the protruding portion 32b placed on the first holding portion 31b among the first to third holding portions 31b to 31d, assuming that other conditions are the same, the usable length of the compression spring 33 becomes the longest, and the pressure of the developing device 5 (developing roller 5a) against the photosensitive drum 1 becomes the smallest. In contrast, when the support member 32 is held by the holding member 31 (case member 30) with the protruding portion 32b placed on the second holding portion 31c, the usable length of the compression spring 33 becomes shorter, and the pressure of the developing device 5 (developing roller 5a) against the photosensitive drum 1 becomes larger. Furthermore, when the support member 32 is held by the holding member 31 (case member 30) with the protruding portion 32b placed on the third holding portion 31d, the usable length of the compression spring 33 becomes even shorter, and the pressure of the developing device 5 (developing roller 5a) against the photosensitive drum 1 becomes even larger.

[0029] In this manner, the pressure mechanisms 31-33 in this embodiment are capable of adjusting the pressure of the developing device 5 (developing roller 5a) against the photosensitive drum 1 by changing the holding portion on which the protrusion 32b is held (placed) among the first to third holding portions 31b-31d. In particular, in this embodiment, a plurality of pressure mechanisms 31-33 are provided at intervals in the longitudinal direction of the developing device 5 (pressurizing body) (in this embodiment, they are provided at both longitudinal ends). This makes it possible to adjust the pressure of the developing device 5 (developing roller 5a) against the photosensitive drum 1 separately and independently depending on the longitudinal position. For example, in a case where image omissions, which will be described later, occur only at one longitudinal end and not at the other longitudinal end, only the pressure mechanisms 31-33 at one longitudinal end are adjusted in pressure. The pressure mechanisms 31-33 are adjusted to reduce the weight of the developing device 5 as the toner is consumed over time, and unless the contact pressure of the developing roller 5a against the photosensitive drum 1 is set high, the developing device 5 flutters and causes defects such as missing images. Therefore, the pressure can be adjusted based on the image quality of the printed image (presence or absence of missing images) (for example, adjusted when missing images occur), or based on the operating time of the developing device 5 (for example, adjusted when a toner near-end message is displayed).

[0030] Here, referring to Figures 6 to 8, etc., the second retaining portion 31c has a space A formed upstream (at a lower position) in the biasing direction, which space A communicates with the hole portion 31a and opens toward the first retaining portion 31b side (the counterclockwise side in Figure 7). That is, the second holding portion 31c is not formed as a solid structure with respect to the surface on which the first holding portion 31b is formed, but has a hollow structure space A connected to the hole portion 31a. Also, the space A has an opening B (slit) that leads to the first holding portion 31b on the counterclockwise side in Fig. 7. This space A is formed in a substantially sector shape following the shape of the second holding portion 31c.

[0031] 8(A), the support member 32 is inserted into the space A from the upstream side of the biasing direction (from below the case member 30) with the protruding portion 32b and the cylindrical portion 32a inserted into the hole portion 31a, and then rotated around the hole portion 31a with the rotation direction toward the first holding portion 31b being the forward direction (counterclockwise), so that the protruding portion 32b is held by the first holding portion 31b (as shown in FIG. 8(A)). Note that, for simplicity, the compression spring 33 is omitted from the illustration in FIGS. 8(A) and (B). In contrast, referring to Figure 8(B), the support member 32 is rotated around the hole portion 31a from a state in which the protrusion 32b is held by the first holding portion 31b (the state in Figure 8(A)) in the reverse direction (clockwise) toward the second holding portion 31c, so that the protrusion 32b is held by the second holding portion 31c (the state in Figure 8(B)). Furthermore, although not shown, when the support member 32 is rotated in the reverse direction (clockwise) around the hole portion 31a from a state in which the protrusion portion 32b is held by the second holding portion 31c (the state in Figure 8 (B)), the protrusion portion 32b is held by the third holding portion 31d. In addition, when the holding position of the support member 32 is changed from the second holding portion 31c to the first holding portion 31b, or from the third holding portion 31d to the second holding portion 31c, the support member 32 is rotated in the forward direction (counterclockwise).

[0032] The following provides a further supplementary explanation of the attachment of the support member 32 to the holding member 31 (case member 30) and the adjustment of the pressure. When assembling the support member 32 to the holding member 31 (case member 30), first, the support member 32 is inserted from below the holding member 31 so that the columnar portion 32a enters the hole portion 31a and the protruding portion 32b enters the space A of the second holding portion 31c. At this time, the compression spring 33 is inserted into the recess 32a1 of the columnar portion 32a. Then, a Phillips head screwdriver is inserted from below into the operating portion 32a2 (cross-shaped hole portion) and the support member 32 is rotated in the forward direction (counterclockwise direction) while receiving the urging force of the compression spring 33. As a result, the protruding portion 32b passes through the opening B and is held on the first holding portion 31b. The state in which the protruding portion 32b is held on the first holding portion 31b is the basic setting (initial setting) in the manufacturing process of the process cartridge 10 at the manufacturing factory. On the other hand, when a serviceman or other worker changes the state of the support member 32 (projection portion 32b) held by the first holding portion 31b to the state of the support member 32 held by the second holding portion 31c (when adjusting to increase the pressure force) for a process cartridge 10 or the like used on the market, the worker inserts a Phillips screwdriver into the operating portion 32a2 (cross-shaped hole portion) from below again and rotates the screwdriver to rotate the support member 32 in the reverse direction (clockwise). At this time, the screwdriver is pushed upward to push up the support member 32 so that the projecting portion 32b overcomes the step (the step between the first holding portion 31b and the second holding portion 31c). Similarly, when changing the state in which the support member 32 (protrusion 32b) is held by the second holding portion 31c to a state in which it is held by the third holding portion 31d (when adjusting to further increase the pressure force), the screwdriver is rotated to rotate the support member 32 in the reverse direction (clockwise), and the support member 32 is pushed up while pressing the screwdriver upward.

[0033] In this way, by making the rotation direction (forward direction) of the support member 32 when assembling the support member 32 to the holding member 31 different from the rotation direction (reverse direction) when the pressure force is subsequently adjusted to a larger value, it is possible to reduce the inconvenience of an operator accidentally assembling the support member 32 so that the protrusion 32b (support member 32) is held by holding portions 31c, 31d other than the first holding portion 31b during assembly during manufacturing.

[0034] 6 to 8, etc., in this embodiment, the retaining member 31 (case member 30) is formed with a partition portion 31e that stands up toward the downstream side (higher position) in the biasing direction on the positive (clockwise) side relative to the first retaining portion 31b. Specifically, a partition portion 31e is provided between the first holding portion 31b and the third holding portion 31d, and has the same radial width as the third holding portion 31d so as to extend to a position higher than the third holding portion 31d. Providing the partition 31e in this manner can ensure the rigidity of the hollow second and third holding parts 31c and 31d. Providing the partition 31e can also limit the forward rotation of the support member 32 beyond the first holding part 31b during assembly. Furthermore, it can also prevent the protrusion 32b (support member 32) held by the third holding part 31d from falling off to the position of the first holding part 31b due to vibration or the like.

[0035] In this manner, in the pressure mechanisms 31-33 of this embodiment, the holding member 31 (case member 30) is configured so that a plurality of holding portions 31b-31d for holding the support member 32 at positions in different force directions are arranged at different positions around the support member 32. As a result, even if the developing device 5 becomes lighter over time as toner is consumed, the pressure applied by the developing device 5 (developing roller 5a) to the photosensitive drum 1 can be adjusted relatively easily without complicating the configuration of the pressure mechanism or automatically controlling the pressure mechanism. This reduces the problem of the pressure applied by the developing roller 5a to the photosensitive drum 1 becoming insufficient over time, causing abnormalities such as missing images in the image formed on the photosensitive drum 1. Furthermore, by using such pressure mechanisms 31-33, which allow easy adjustment of the pressure, the pressure can be easily adjusted even when the desired pressure cannot be obtained due to dimensional errors or assembly errors of components during the manufacturing process of the process cartridge 10. Furthermore, even when a worker such as a serviceman performs maintenance on a process cartridge 10 in use on the market to correct a sudden occurrence of image omissions or the like, the pressure can be easily adjusted.

[0036] <Variation 1> 9 and 10, in the holding member 31 (case member 30) in the first modification, a protrusion 31b1 is formed on the first holding portion 31b to limit the rotation of the support member 32 toward the second holding portion 31c. The protrusion 31b1 is formed to protrude in the biasing direction (upward) from the surface portion on which the first holding portion 31b is formed, and engages with the protrusion 32b of the support member 32 to limit the rotation of the support member 32. Further, the second holding portion 31c is formed with a protrusion 31c1 that limits the rotation of the support member 32 toward the first holding portion 31b. The protrusion 31c1 is formed so as to protrude in the biasing direction (upward) from the surface portion on which the second holding portion 31c is formed, and engages with the protrusion 32b of the support member 32 to limit the rotation of the support member 32. The third holding portion 31d also has a protrusion 31d1 formed thereon to limit the rotation of the support member 32 toward the second holding portion 31c. The protrusion 31d1 is formed to protrude in the biasing direction (upward) from the surface portion on which the third holding portion 31d is formed, and engages with the protrusion 32b of the support member 32 to limit the rotation of the support member 32. By setting the size of the central angle of the sector of the first to third holding portions 31b to 31d to be larger than the size of the central angle of the sector of the protrusion 32b of the support member 32, it becomes easier to ensure space for providing the convex portions 31b1 to 31d1 in the first to third holding portions 31b to 31d. By providing the protrusions 31b1 to 31d1, when the support member 32 (protrusion 32b) is rotated toward the first to third holding portions 31b to 31d, the protrusion 32b needs to climb over the protrusions 31b1 to 31d1. Therefore, it is preferable to set the height (height in the biasing direction) of the protrusions 31b1 to 31d1 to be equal to or less than the plate thickness of the protrusion 32b.

[0037] <Variation 2> As shown in FIGS. 12 and 13, in the second modification, the protruding portion 32b of the support member 32 is formed with a first inclined surface 32b1 and a second inclined surface 32b2. The first inclined surface 32b1 of the protrusion 32b is formed on the upstream side of the biasing direction (the lower surface of the protrusion 32b) on the positive (counterclockwise) side, and is an inclined surface that inclines toward the upstream side (downward) of the biasing direction as it approaches the reverse direction (clockwise). In contrast, the second inclined surface 32b2 of the protrusion 32b is formed on the downstream side of the urging direction (the upper surface of the protrusion 32b) in the reverse direction (clockwise), and is an inclined surface that inclines toward the downstream side (upward) of the urging direction as it approaches the forward direction (counterclockwise). Also, as shown in Figures 11 and 13, in variant example 2, the first retaining portion 31b has a tapered portion 31b10 formed at the end on the second retaining portion 31c side that is connected to the opening B, which is inclined toward the upstream side (downward) of the biasing direction as it moves in the reverse direction (clockwise). In contrast, the second retaining portion 31c has a tapered portion 31c10 formed at the end on the side of the first retaining portion 31b that contacts space A, which slopes downstream (upward) in the biasing direction as it moves in the positive direction (counterclockwise). By configuring in this manner, even if the step (offset amount) between first holding portion 31b and second holding portion 31c is set small in order to finely adjust the amount of pressure applied by pressure mechanisms 31-33, the assembly work of support member 32 (the work of rotating protruding portion 32b in the forward direction toward first holding portion 31b through opening B) can be performed smoothly without reducing the thickness of protruding portion 32b to reduce its rigidity.

[0038] As described above, the pressure mechanisms 31-33 in this embodiment are pressure mechanisms that pressurize the developing device 5 (pressurizing body) against the photosensitive drum 1 (target body), and are provided with the compression spring 33, one end of which directly or indirectly contacts the developing device 5 and presses the developing device 5 toward the photosensitive drum 1 in a predetermined pressing direction. Also provided are a support member 32 that supports the other end of the compression spring 33, and a holding member 31 that holds the support member 32. The holding member 31 has a plurality of holding portions 31b-31d that are arranged at different positions around the support member 32 to hold the support member 32 at positions in different pressing directions. This makes it possible to relatively easily optimize the pressure of the developing device 5 against the photosensitive drum 1 even over time.

[0039] In this embodiment, the present invention is applied to pressure mechanisms 31-33 that are installed in a process cartridge 10 in which a photosensitive drum 1 (image carrier), a charging roller 4 (charging device), a developing device 5, and a cleaning device 2 are integrated, and pressurize the developing device 5 (pressurizing body) against the photosensitive drum 1 (target body). However, the application of the present invention is not limited to this, and the present invention can be applied to any other pressure mechanisms that pressurize a pressure body against a target body. Even in such a case, the same effect as that of this embodiment can be obtained. In this application, a "process cartridge" is defined as a unit in which at least one of a charging device for charging an image carrier, a developing device for developing a latent image formed on the image carrier, and a cleaning device for cleaning the image carrier is integrated with an image carrier, and the unit is detachably installed in the main body of an image forming apparatus.

[0040] In addition, in this embodiment, the holding member 31 is formed with three holding portions 31b to 31d, but the number of holding portions may be two or four or more. In addition, in this embodiment, two protrusions 32b are formed on the support member 32, but the number of protrusions 32b is not limited to this and may be three or more. In that case, it is preferable that the multiple protrusions are arranged equally in the circumferential direction from the viewpoint of load balance. Furthermore, in the holding member, holding portions at the same height position are formed according to the number and positions of the protrusions. In addition, in this embodiment, the pressure mechanisms 31 to 33 are installed at both ends in the longitudinal direction, but it is also possible to install one pressure mechanism 31 to 33 in the longitudinal center, or to install three or more pressure mechanisms at intervals in the longitudinal direction. Even in these cases, the same effects as those of this embodiment can be obtained.

[0041] It is clear that the present invention is not limited to the present embodiment, and that the present embodiment may be modified as appropriate within the scope of the technical concept of the present invention in addition to the modifications suggested in the present embodiment. Furthermore, the number, position, shape, etc. of the components are not limited to the present embodiment, and may be any number, position, shape, etc. suitable for implementing the present invention. [Explanation of symbols]

[0042] 1 Photoconductor drum (target body), 5 developing device (pressure body), 10 Process cartridge, 30 Case member, 30a spindle, 31 holding member, 31a hole, 31b first holding part, 31b1 convex part, 31b10 Tapered portion, 31c second holding part, 31c1 convex part, 31c10 Tapered section, 31d third holding part, 31d1 convex part, 31e Partition, 32 Support member, 32a Cylindrical part, 32a1 recess, 32a2 operation unit, 32b Projection part (held part), 32b1 1st slope, 32b2 2nd slope, 33 Compression spring, 100 Image forming apparatus, A space, B aperture.

[0043] The present invention can also be embodied in the following combinations of Supplementary Notes 1 to 15. (Appendix 1) A pressurizing mechanism for pressurizing a pressurizing body to a target body, A compression spring whose one end side directly or indirectly contacts the pressure body and biases the pressure body toward the target body in a predetermined biasing direction; a support member for supporting the other end of the compression spring; A holding member for holding the support member; Equipped with The pressure mechanism is characterized in that the holding member has a plurality of holding portions arranged at different positions around the support member for holding the support member at different positions in the biasing direction. (Appendix 2) The support member is a cylindrical portion having a recess into which the other end of the compression spring is inserted; At least two protrusions protruding radially from the periphery of the cylindrical portion and arranged at equal intervals in the circumferential direction; Equipped with The holding member is a hole into which the cylindrical portion is inserted; the plurality of holding portions are arranged in a stepped manner so that positions in the biasing direction are different, and are arranged around the hole portion with a phase difference in a circumferential direction, and are capable of holding the at least two protrusions; 2. The pressure mechanism according to claim 1, comprising: (Appendix 3) The plurality of holding portions include A first holding portion located most upstream in the biasing direction; a second retaining portion disposed adjacent to the first retaining portion in the circumferential direction and located downstream of the first retaining portion in the biasing direction; 3. The pressure mechanism according to claim 1 or 2, comprising: (Appendix 4) The second holding portion has a space that communicates with the hole portion and opens toward the first holding portion, the space being formed on the upstream side of the biasing direction, The pressure mechanism described in Appendix 3, characterized in that the support member is rotated around the hole with the rotation direction toward the first retaining portion as the positive direction after the protrusion is inserted into the space from the upstream side of the biasing direction and the cylindrical portion is inserted into the hole, thereby holding the protrusion in the first retaining portion. (Appendix 5) The pressure mechanism described in Appendix 3 or Appendix 4, characterized in that the support member is rotated around the hole from a state in which the protrusion is held by the first holding portion to a state in which the rotation direction is reversed toward the second holding portion, thereby holding the protrusion by the second holding portion. (Appendix 6) The pressure application mechanism according to any one of Supplementary Note 3 to Supplementary Note 5, characterized in that the plurality of retaining portions are arranged adjacent to the second retaining portion in the opposite circumferential direction and include a third retaining portion located downstream of the second retaining portion in the biasing direction. (Appendix 7) The pressure mechanism according to any one of Supplementary Notes 3 to 6, wherein the holding member is formed with a partition portion that stands up toward the downstream side of the biasing direction on the positive side relative to the first holding portion. (Appendix 8) The pressure mechanism according to any one of claims 3 to 7, wherein the first holding portion is formed with a convex portion that limits rotation of the support member toward the second holding portion. (Appendix 9) The pressure mechanism according to any one of Supplementary Note 3 to Supplementary Note 8, wherein the second holding portion is formed with a convex portion that limits rotation of the support member toward the first holding portion. (Appendix 10) The protrusion of the support member is a first inclined surface that is formed on the upstream side of the biasing direction and on the forward direction side and that inclines toward the upstream side of the biasing direction as it approaches the reverse direction; a second inclined surface formed on the downstream side of the biasing direction and on the side of the reverse direction, the second inclined surface inclining toward the downstream side of the biasing direction as it approaches the forward direction; 6. The pressure mechanism according to claim 5, comprising: (Appendix 11) The first holding portion has an end portion on the second holding portion side, the end portion being connected to the opening, the end portion being tapered toward the upstream side in the biasing direction as the end portion moves in the reverse direction, The pressurizing mechanism described in Appendix 10, wherein the second retaining portion has a tapered portion formed at an end portion on the side of the first retaining portion and in contact with the space, the tapered portion being inclined toward the downstream side of the biasing direction as it approaches the positive direction. (Appendix 12) 12. The pressure mechanism according to any one of claims 1 to 11, wherein a plurality of the pressure mechanisms are provided at intervals in the longitudinal direction of the pressure body. (Appendix 13) 13. The pressure mechanism according to any one of claims 1 to 12, wherein the holding member is a case member that holds the target body and also holds the pressure body so that it can swing about a support shaft. (Appendix 14) A process cartridge that is detachably installed in a main body of an image forming apparatus, A process cartridge comprising: a pressure mechanism according to any one of claims 1 to 13; a photosensitive drum as the pressure target; and a developing device as the pressure target. (Appendix 15) An image forming apparatus comprising the pressure mechanism according to any one of claims 1 to 13. [Prior art documents] [Patent documents]

[0044] [Patent Document 1] Japanese Patent Application Publication No. 9-190058

Claims

1. A pressurizing mechanism for pressurizing a pressurizing body to a target body, A compression spring whose one end side directly or indirectly contacts the pressure body and biases the pressure body toward the target body in a predetermined biasing direction; a support member for supporting the other end of the compression spring; A holding member for holding the support member; Equipped with The pressure mechanism is characterized in that the holding member has a plurality of holding portions arranged at different positions around the support member for holding the support member at different positions in the biasing direction.

2. The support member is a cylindrical portion having a recess into which the other end of the compression spring is inserted; At least two protrusions protruding radially from the periphery of the cylindrical portion and arranged at equal intervals in the circumferential direction; Equipped with The holding member is a hole into which the cylindrical portion is inserted; the plurality of holding portions being arranged in a stepped manner so as to be different in position in the biasing direction and being arranged around the hole portion with a phase shift in a circumferential direction, and capable of holding the at least two protrusions; 2. The pressure mechanism according to claim 1, further comprising:

3. The plurality of holding portions include A first holding portion located most upstream in the biasing direction; a second retaining portion disposed adjacent to the first retaining portion in a circumferential direction and located downstream of the first retaining portion in the biasing direction; 3. The pressure mechanism according to claim 2, further comprising:

4. The second holding portion has a space that communicates with the hole portion and opens toward the first holding portion, the space being formed on the upstream side of the biasing direction, The pressure mechanism according to claim 3, characterized in that the support member is rotated around the hole with the rotation direction toward the first retaining portion as the positive direction after the protrusion is inserted into the space from the upstream side of the biasing direction and the cylindrical portion is inserted into the hole, thereby holding the protrusion in the first retaining portion.

5. The pressure mechanism according to claim 4, characterized in that the support member is rotated around the hole in a direction reversed from a state in which the protrusion is held by the first holding portion to a state in which the protrusion is held by the second holding portion, toward the second holding portion.

6. The pressure application mechanism according to claim 5, characterized in that the plurality of retaining portions include a third retaining portion arranged adjacent to the second retaining portion in the opposite circumferential direction and located downstream of the second retaining portion in the biasing direction.

7. 6. The pressure mechanism according to claim 4, wherein the holding member is formed with a partition portion that stands up toward a downstream side in the biasing direction on the side of the positive direction with respect to the first holding portion.

8. 6. The pressure mechanism according to claim 4, wherein the first holding portion is formed with a protrusion for restricting rotation of the support member toward the second holding portion.

9. 6. The pressure mechanism according to claim 4, wherein the second holding portion is formed with a protrusion for restricting rotation of the support member toward the first holding portion.

10. The protrusion of the support member is a first inclined surface that is formed on the upstream side of the biasing direction and on the forward direction side and that inclines toward the upstream side of the biasing direction as it approaches the reverse direction; a second inclined surface formed on the downstream side of the biasing direction and on the side of the reverse direction, the second inclined surface inclining toward the downstream side of the biasing direction as it approaches the forward direction; 6. The pressure mechanism according to claim 5, further comprising:

11. The first holding portion has an end portion on the second holding portion side, the end portion being connected to the opening, the end portion being inclined toward the upstream side in the biasing direction as the end portion extends in the reverse direction, The pressure mechanism according to claim 10, characterized in that the second retaining portion has a tapered portion formed at an end portion on the side of the first retaining portion and in contact with the space, the tapered portion being inclined toward the downstream side of the biasing direction as it approaches the positive direction.

12. 3. The pressure mechanism according to claim 1, wherein a plurality of the pressure mechanisms are provided at intervals in the longitudinal direction of the pressure body.

13. 3. The pressure mechanism according to claim 1, wherein the holding member is a case member that holds the target body and also holds the pressure body so that it can swing about a support shaft.

14. A process cartridge that is detachably installed in a main body of an image forming apparatus, 3. A process cartridge comprising: the pressure mechanism according to claim 1; a photosensitive drum as the target body; and a developing device as the pressure body.

15. 3. An image forming apparatus comprising the pressure mechanism according to claim 1.

Images