JP5522993B2 - Process cartridge - Google Patents

Description

  The present invention relates to a process cartridge having a function of forming an image on a recording material such as a sheet, which is detachably provided in an image forming apparatus such as a copying machine or a printer.

  2. Description of the Related Art Conventionally, in a developing device of an electrophotographic image forming apparatus using an electrophotographic image forming process, a configuration in which a developer carrier is rotatably supported on a developing frame is known. The following is known as the configuration of the developer carrying member in the developing device using magnetic toner. It includes a developing roller rotatably supported by the developing frame, a magnet member enclosed in the developing roller and fixed at a predetermined phase, and a predetermined amount between the photosensitive drum as the image carrier and the developing roller. It consists of a spacer member for maintaining the gap.

  The magnet member includes a portion for carrying the magnetic toner on the surface of the developing roller and a support portion for fixing at a predetermined phase. The magnetic toner bearing part maintains a certain amount of gap so that it does not come into contact with the inner peripheral surface of the developing roller. However, in order to effectively apply magnetic force to the surface of the developing roller, at least gaps in each magnetic phase are possible It is often set as small as possible. Further, the support portion for fixing is often smaller in diameter than the portion for supporting the magnetic toner due to the support structure.

  As an example in which a shape having another function is provided on the magnet member, an example in which a protrusion is provided on the magnet member for the purpose of improving the assemblability of the developer carrier is known (see Patent Document 1). In addition, there is known an example in which a notch portion is provided in a magnet member for the purpose of improving the toner sealability at the end of the developer carrying member (see Patent Document 2). In addition, in a configuration in which a predetermined amount of gap is maintained between the photosensitive drum and the developing roller, the following is applied to prevent the photosensitive drum and the developing roller from coming into contact with each other due to an impact caused by dropping or the like before use. The composition is known. That is, a sheet-like protective member is disposed between the photosensitive drum and the developing roller (see Patent Document 3). Further, in the configuration in which a predetermined amount of gap is maintained between the photosensitive drum and the process means, the following is applied for the purpose of preventing the photosensitive drum and the process means from coming into contact with each other due to an impact caused by dropping or the like before use. It is known what has been configured. That is, the photosensitive drum is separated from the process means by the photosensitive drum protection member (see Patent Document 4).

JP 2004-157433 A JP 2007-47396 A Japanese Patent Laid-Open No. 2000-19800 JP 2002-182541 A

However, in the above configuration, for example, in the case where a sheet-like protective member is disposed between the photosensitive drum and the developing roller, the user needs to remove the sheet-like protective member. Further, in the example in which the photosensitive drum and the process unit are separated by the photosensitive drum protection member, a configuration for separating the photosensitive drum from the process unit necessary for image formation is required.

  The present invention has been made in view of the above circumstances, and in a configuration having a predetermined amount of gap between the image carrier and the developing roller, no extra work is required, and a simple configuration such as dropping before use. An object of the present invention is to suppress the contact between the image carrier and the developing roller due to the impact caused by the above.

In order to achieve the above object, the present invention provides:
A process cartridge detachably attached to the image forming apparatus,
An image carrier on which an electrostatic latent image is formed;
A developing roller provided on the image bearing member via a gap; and a magnet member provided on the inner circumferential side of the developing roller and provided on the inner circumferential surface of the developing roller via the gap. A developer carrier;
A support portion for supporting the magnet member;
With
The magnet member is
A magnet body,
Wherein provided on both end sides in the axial direction of the rotation axis of the developing roller with respect to the magnet main body, and the supported portion supported by the supporting portion,
Protruding portions provided on both end sides of the magnet member in the axial direction, projecting from the magnet main body toward the inner peripheral surface of the developing roller, and spaced from the inner peripheral surface;
Have
The size of the gap between the inner peripheral surface of the developing roller and the protruding portion is smaller than the size of the gap between the inner peripheral surface of the developing roller and the magnet body portion ,
The support portion supports the supported portion inside the developing roller and inside the end portion in the axial direction of the developing roller,
The protruding portion is located further inward in the axial direction than the supported portion, and can contact the inner peripheral surface of the developing roller when the magnet member is bent .

  According to the present invention, in a configuration having a predetermined amount of gap between the image carrier and the developing roller, an extra work is not required, and an impact due to dropping or the like is applied before use with a simple configuration. And the developing roller can be prevented from coming into contact with each other.

FIG. 2 is a cross-sectional view illustrating a schematic configuration of the image forming apparatus according to the first exemplary embodiment. FIG. 3 is a cross-sectional view illustrating a schematic configuration of a process cartridge according to the first embodiment. FIG. 3 is a perspective view illustrating a schematic configuration of a developing unit according to the first exemplary embodiment. FIG. 3 is a perspective view illustrating a schematic configuration in a state where a developer carrier is removed from a developing unit according to the first exemplary embodiment. FIG. 3 is a cross-sectional view illustrating a configuration of a developer carrying member of Example 1 and a method for supporting the developing frame. FIG. 3 is a cross-sectional view illustrating a configuration for supporting one end of the developer carrying member of Example 1. FIG. 3 is a cross-sectional view illustrating a configuration for supporting one end of the developer carrying member of Example 1. FIG. 3 is a cross-sectional view showing a support structure on the other end side of the developer carrying member of Example 1. FIG. 3 is a cross-sectional view illustrating a schematic configuration of a developer carrier of Example 1. FIG. 3 is a cut perspective view of the developer carrying member illustrating a schematic configuration of the end of the magnet member according to the first embodiment. FIG. 7 is a cut perspective view of a developer carrying member showing another example of the end of the magnet member according to the first embodiment. The figure explaining the case where a magnet member bends by impacts, such as dropping. The figure explaining the case where a magnet member bends by impacts, such as dropping. The figure which shows schematic structure of the developer carrier of a reference example .

  DETAILED DESCRIPTION Exemplary embodiments for carrying out the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments. The present invention relates to an electrophotographic image forming apparatus, and more particularly to a developing device and a process cartridge used in an electrophotographic image forming apparatus. Here, the electrophotographic image forming apparatus is an apparatus that forms an image on a recording material (sheet material, recording paper, OHP sheet, cloth, etc.) using an electrophotographic image forming process. This includes, for example, an electrophotographic copying machine, an electrophotographic printer, a laser beam printer, an electrophotographic facsimile, and the like. The process cartridge (process unit) refers to a cartridge in which at least the developing means and the electrophotographic photosensitive member are integrated into a cartridge and detachably provided on the main body of the image forming apparatus.

  The image forming apparatus A to which the present invention is applicable will be described in detail below. In this embodiment, a process cartridge having a photosensitive drum is shown as an example of a process unit. In the following description, the longitudinal direction is a direction intersecting (substantially orthogonal to) a direction in which the process cartridge is mounted on the image forming apparatus main body, and is an axial direction of the rotation axis (rotation axis) of the photosensitive drum and the developing roller. (Axial direction). The longitudinal direction is also substantially parallel to the surface of the recording material to be conveyed and is also a direction intersecting (substantially orthogonal) to the recording material conveyance direction. The upper and lower sides mean the upper and lower sides in a state where the process cartridge is mounted on the image forming apparatus main body. First, a process cartridge and an image forming apparatus main body provided with the process cartridge in a detachable manner will be specifically described with reference to FIGS. FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus main body in which a process cartridge is mounted. FIG. 2 is a cross-sectional view showing a schematic configuration of the process cartridge.

(overall structure)
As shown in FIG. 1, the image forming apparatus A transfers information based on image information from an optical system 1 as an optical means to a drum-shaped electrophotographic photosensitive member (image carrier, hereinafter referred to as “photosensitive drum”) 7. Light is irradiated. As a result, an electrostatic latent image is formed on the photosensitive drum 7, and this electrostatic latent image is developed with a developer (hereinafter referred to as “toner”) t to form a toner image. In synchronism with the formation of the toner image, the recording material 2 is separated and fed one by one from the feeding section (cassette) 3a by the pickup roller 3b and the pressure contact member 3c in pressure contact therewith. A toner image formed on the photosensitive drum 7 of the process cartridge B is transferred to the recording material 2 conveyed along the conveyance guide 3f1 by applying a voltage to a transfer roller 4 as a transfer unit. Further, the recording material 2 onto which the toner image has been transferred is conveyed to the fixing unit 5 along the conveyance guide 3f2. The fixing unit 5 includes a driving roller 5a, a heater 5b, a support 5c, and a fixing rotating body 5d composed of a cylindrical sheet rotatably supported by the support 5c. And a pressure is applied to fix the transferred toner image. The recording material 2 on which the transferred toner image has been fixed is conveyed by the discharge roller 3d and discharged to the discharge unit 6 through the reverse conveyance path. In the present embodiment, the conveying means 3 is constituted by the pickup roller 3b, the press contact member 3c, the discharge roller 3d, etc., but this is not restrictive.

(Process cartridge configuration)
The process cartridge B includes the photosensitive drum 7 and at least one process means. Examples of the process means include a charging means for charging the photosensitive drum 7, a developing means for developing the electrostatic latent image formed on the photosensitive drum 7, and a cleaning means for cleaning the toner t remaining on the photosensitive drum 7. Etc. In the process cartridge B of the present embodiment, as shown in FIG. 2, a photosensitive drum 7 as an electrophotographic photosensitive member having a photosensitive layer is rotationally driven, and a voltage is applied to a charging roller 8 as a charging unit to apply the photosensitive member. The surface of the drum 7 is uniformly charged. Information light (light image) based on image information from the optical system 1 is exposed to the charged photosensitive drum 7 through the exposure opening 9b to form an electrostatic latent image on the surface of the photosensitive drum 7. The electrostatic latent image is developed by the developing unit 10 as developing means.

  The developing unit 10 has a developing frame 10f, and the toner t in the toner container 10a as a developer container provided in the developing frame 10f is sent out by a rotatable stirring member 10b as a toner feeding unit. It is. In the developer carrier 10g disposed in the developing frame 10f in the developing unit 10, a rotatable developing roller 10d and a magnet member 15 disposed on the inner side (inner peripheral side) of the developing roller 10d are provided. Have. Here, the developing roller 10d is rotatably supported by the developing frame 10f, and the magnet member 15 is fixed (supported) to the developing frame 10f (process cartridge main body side). A toner layer to which triboelectric charge is imparted is formed on the surface of the developing roller 10d by the developing blade 10e, and a toner image is formed by transferring the toner to the photosensitive drum 7 in accordance with the electrostatic latent image. Imaged. In other words, the developing roller 10 d has a function of carrying the toner t and transporting it to the area facing the photosensitive drum 7.

  Then, the toner image is transferred to the recording material 2 by applying a voltage having a polarity opposite to that of the toner image to the transfer roller 4. After the transfer, the toner remaining on the photosensitive drum 7 is scraped off by a cleaning blade 11a provided in a cleaning unit 11 as a cleaning unit, and leakage from the removed toner storage unit 11c is prevented by a squeeze sheet 11b. . The cleaning unit 11 includes a cleaning frame 11f, and the photosensitive drum 7, the charging roller 8, and the cleaning blade 11a are supported by the cleaning frame 11f. The developing unit 10 and the cleaning unit 11 are coupled so as to be rotatable at a swing center 11g. The developing roller 10 d is pressed against the photosensitive drum 7 by an elastic member 19 provided between the developing unit 10 and the cleaning unit 11.

(Explanation about development part)
FIG. 3 is a perspective view illustrating a schematic configuration of the developing unit 10. FIG. 4 is a perspective view showing a schematic configuration in a state where the developer carrying member 10g is removed from the developing unit 10. As shown in FIG. 4, the developing frame 10f has an opening 10h for exposing a part of the developing roller 10d. The opening 10 h is for transporting (supplying) the toner t from the inside of the developing frame 10 f to the photosensitive drum 7 and is substantially rectangular. Seal members 10i and 10j are attached to one end and the other end in the longitudinal direction of the opening 10h. The seal members 10i and 10j restrict the toner t from leaking between the developing frame 10f and the developing roller 10d along the longitudinal direction of the developing roller 10d. Here, as the seal members 10i and 10j, a magnetic seal member that is not in contact with the developing roller 10d may be used, or an elastic seal member that is in contact with the developing roller may be used.

  A mounting portion 10k is provided on the lower side portion along the longitudinal direction of the opening 10h. A flexible sheet member 10n is attached to the attachment portion 10k via a double-sided tape 10m (a broken line portion in FIGS. 3 and 4). The flexible sheet member 10n restricts the toner t from leaking between the lower side portion of the developing roller 10d and the attached portion 10k. Here, in the flexible sheet member 10n, one end side in the short direction perpendicular to the longitudinal direction is attached to the attached portion 10k, and the other end side in the short side is in contact with the developing roller 10d. The direction from one end side to the other end side of the flexible sheet member 10n is configured to be a forward direction with respect to the rotation direction of the developing roller 10d.

  The developing blade 10e is provided on the opposite side of the attached portion 10k over the longitudinal direction of the opening 10h. That is, it is provided at the downstream end of the developing frame 10f in the rotation direction of the developing roller 10d. The developing blade 10e has a restricting portion 10p formed of an elastic body, and the length of the restricting portion 10p in the longitudinal direction is substantially the same as the length of the opening 10h in the longitudinal direction. The developer carrier 10g is rotatably supported with respect to the developing frame 10f via one end side holder 24 and the other end side holder 25 that are attached to the side surface in the longitudinal direction of the developing frame 10f.

(Explanation about developer carrier)
FIG. 5 is a schematic cross-sectional view showing the configuration of the developer carrier 10g and a method for supporting the developer frame 10f. The developing roller 10d constituting the developer carrier 10g has a flange portion 12 on one end side in the longitudinal direction. As a material, an aluminum alloy or the like including the flange portion 12 is used. The flange portion 12 has an attachment portion 12 a for integrally attaching a developing roller gear 13 that receives drive transmission from a drum gear 7 a provided on one end side in the longitudinal direction of the photosensitive drum 7. The longitudinal end shaft portion 13 a of the developing roller gear 13 is rotatably supported by a bearing portion 14 formed integrally with the one end side holder 24. The other end side in the longitudinal direction of the developing roller 10d has a support portion 17 rotatably supported by a bearing portion 16 integrally formed with the other end side holder 25 on the inner peripheral surface side.

Magnet member 15 includes a main magnet portion 15a of the magnet main body portion for carrying the toner t on the surface of the developing roller 10d, the support for fixing the developing frame 10f of the magnet member 15 with a predetermined phase It consists of the one end side shaft portion 15b and the other end side shaft portion 15c as parts. The one end side shaft portion 15b and the other end side shaft portion 15c are provided on both ends in the longitudinal direction with respect to the main magnet portion 15a. As the material, ferrite-containing nylon resin or the like is used. For example, when the outer diameter of the developing roller 10d is φ10 mm to φ14 mm, the outer diameter of the main magnet portion 15a of the magnet member 15 is φ7.6 mm to φ11.6 mm, and the main magnet portion 15a and the inner peripheral surface of the developing roller 10d. The gap (gap) is about 0.4 mm. The one end side shaft portion 15b of the magnet member 15 is rotatably supported by a support portion 12b provided on the flange portion 12 on one end side in the longitudinal direction of the developing roller 10d. The other end side shaft portion 15c of the magnet member 15 is supported by a bearing portion (support portion) 16 that is integrally formed with the developing device frame 10f.

  Spacer members 18 are attached to both ends of the developing roller 10d in the longitudinal direction. The spacer member 18 has a cap shape and is attached to cover both ends of the developing roller 10d in the longitudinal direction. As shown in FIG. 2, the spacer member 18 is pressed so as to come into contact with the photosensitive drum 7 by an elastic member 19 provided between the developing unit 10 and the cleaning unit 11. As a result, a gap of about 0.2 mm to 0.5 mm is formed between the photosensitive drum 7 and the developing roller 10d at the nearest portion.

  6 and 7 are schematic cross-sectional views showing a support structure on one end side in the longitudinal direction of the developer carrier 10g. FIG. 8 is a schematic cross-sectional view showing a support configuration on the other end side in the longitudinal direction of the developer carrier 10g. As a supporting configuration of the developing roller 10d and the magnet member 15, one end side in the longitudinal direction may be configured as shown in FIG. 6, for example. That is, the longitudinal tip shaft portion 12c of the flange portion 12 provided on one end side in the longitudinal direction of the developing roller 10d extends from the developing roller gear 13 and rotates to the bearing portion 14a configured integrally with the one end side holder 24. It may be supported freely. Further, as shown in FIG. 7, the one end side shaft portion 15 d of the magnet member 15 passes through the hole 12 d provided in the flange portion 12, and the one end side shaft portion tip 15 e is configured integrally with the one end side holder 24. The rotational direction phase may be regulated and supported by the bearing portion 14b.

On the other hand, at the other end in the longitudinal direction, as shown in FIG. 8, the flange member 22 is integrally attached to the other end in the longitudinal direction of the developing roller 10d, and the longitudinal end shaft portion 22a of the flange member 22 is connected to the other end. You may be rotatably supported by the bearing part 16a provided in the side holder 25. FIG. At this time, the other end side shaft portion 15c of the magnet member 15 is supported by the bearing portion 16a with its rotational direction phase regulated.

(Description of magnet member)
FIG. 9 is a cross-sectional view showing a schematic configuration of the developer carrier 10g. FIG. 10 is a diagram for explaining a schematic configuration of the end portion of the magnet member 15, and is a perspective view of a cut surface of the developer carrier 10g. FIG. 11 is a perspective view of a cut surface of the developer carrier 10g showing another configuration of the end of the magnet member 15. FIG. A pair of convex portions 20 are provided as projecting portions on both ends in the longitudinal direction of the main magnet portion 15a constituting the magnet member 15. As shown in FIG. 10, at least in the short direction perpendicular to the longitudinal direction, the convex portion 20 includes a region including a portion where the developer carrying member 10g and the photosensitive drum 7 are closest to each other (the main magnet portion 15a and the photosensitive drum 7). Are arranged in a region facing each other via the developing roller 10d. And the convex part 20 is provided in the main magnet part 15a so that it may protrude in a transversal direction. A gap is provided between the convex portion 20 and the inner peripheral surface of the developing roller 10d, and the gap amount x is set smaller than the gap amount y near the center in the longitudinal direction of the main magnet portion 15a. For example, as described above, when the gap between the main magnet portion 15a and the inner peripheral surface of the developing roller 10d is set to 0.4 mm, the gap amount between the convex portion 20 and the inner peripheral surface of the developing roller 10d is 0.2 mm. Set to degree. Moreover, this convex part 20 may be provided in the outer peripheral whole region of the main magnet part 15a, as shown in FIG.

  Next, the longitudinal position of the magnet member 15 will be described with reference to FIG. The length b of the main magnet portion 15a is longer than the longitudinal width e of the opening 10h provided in the developing device frame 10f (see FIGS. 4 and 9). That is, the longitudinal end 15f of the main magnet portion 15a is located on the outer side in the longitudinal direction from the longitudinal end 21 of the opening 10h. The convex portion 20 is desirably provided closer to the center in the longitudinal direction in the main magnet portion 15a. On the other hand, in the range where the opening 10h is provided, the toner t is carried on the surface of the developing roller 10d, and the main magnet part 15a also acts on the carrying of the toner t. It is desirable to provide the outer side in the longitudinal direction from the end 21. Here, providing the convex portion 20 on the outer side in the longitudinal direction from the longitudinal end portion 21 of the opening 10 h means that the convex portion 20 is between the two virtual regions including the convex portion 20 and orthogonal to the longitudinal direction. That is, 10h is provided. However, if the material of the convex portion 20 is non-magnetic, it can be provided on the inner side in the longitudinal direction from the longitudinal end portion 21 of the opening 10h within a range that does not affect the image.

(Action when an impact is applied to the developer carrier)
12 and 13 are schematic cross-sectional views of the developer carrier 10g, and are diagrams for explaining the case where the magnet member 15 is bent due to an impact such as dropping, and FIG. FIG. 13 shows a state in which the convex portion 20 is provided. For example, when the process cartridge B including the developer carrier 10g receives an impact due to dropping in the course of physical distribution or the like, an impact of about 100 G (980 m / s2) may be applied even if the process cartridge B is in a packaged state. is there. In such a case, due to its own weight, the magnet member 15 bends in the main magnet portion 15a with the shaft portions 15b and 15c at both ends in the longitudinal direction as fulcrums. Then, when the deflection amount z at the central portion in the longitudinal direction shown in FIG. 12 reaches the gap amount y between the inner peripheral surface of the developing roller 10d and the main magnet portion 15a, the main magnet portion 15a contacts the inner peripheral surface of the developing roller 10d. You will be in touch. At this time, the central portion of the developing roller 10d is bent with the contact position between the spacer member 18 provided at both ends in the longitudinal direction of the developing roller 10d and the photosensitive drum 7 as a fulcrum.

When subjected to an impact due to a drop in the T direction shown in FIG. 12, the direction of bending passes through the rotation axis of the developing roller 10d and the rotation axis of the photosensitive drum 7, and is orthogonal to the rotation axis of the developing roller 10d (photosensitive drum 7). The direction is a linear direction and the developing roller 10 d approaches the photosensitive drum 7.
In this case, the gap provided between the developing roller 10d and the photosensitive drum 7 is eliminated, and the developing roller 10d and the photosensitive drum 7 come into contact with each other. This causes scratches on the surfaces of the photosensitive drum 7 and the developing roller 10d (developer carrier 10g).

  On the other hand, when a pair of convex parts 20 are provided at both ends in the longitudinal direction of the main magnet part 15a as in the present embodiment, when the magnet member 15 is bent due to the same impact as shown above, it is shown in FIG. Thus, the convex part 20 contacts the inner peripheral surface of the developing roller 10d before the main magnet part 15a. At this time, the fulcrum of bending of the main magnet portion 15a at the center portion in the longitudinal direction of the main magnet portion 15a is located on the center side in the longitudinal direction from the shaft portions 15b and 15c. The distance between the fulcrums is shortened, and the amount of deflection when the same amount of load is applied to the main magnet portion 15a is reduced. As a result, the contact between the main magnet portion 15a and the inner peripheral surface of the developing roller 10d at the center in the longitudinal direction of the main magnet portion 15a is reduced or eliminated. As a result, in the central portion in the longitudinal direction of the developing roller 10d, bending with the contact position between the spacer member 18 provided at both ends in the longitudinal direction and the photosensitive drum 7 as a fulcrum is reduced, and the developing roller 10d and the photosensitive roller 10d are exposed to light. The contact of the body drum 7 is also reduced or eliminated.

  As described above, according to the present embodiment, the gap between the magnet member 15 and the inner peripheral surface of the developing roller 10d is narrowed at both ends in the longitudinal direction of the main magnet portion 15a. The bent magnet member 15 and the inner peripheral surface of the developing roller 10d are in contact with each other at the narrowed portion. As a result, it is possible to reduce or prevent the inner peripheral surface of the developing roller 10d from coming into contact with the main magnet portion 15a at the central portion in the longitudinal direction of the main magnet portion 15a. The deflection of the central portion can be reduced. Therefore, even when the bending direction of the central portion in the longitudinal direction of the developing roller 10d is the photosensitive drum direction (image carrier side), the contact between the developing roller 10d and the photosensitive drum 7 can be prevented or reduced.

[Reference example]
A reference example will be described below. FIG. 14 is a diagram illustrating a schematic configuration of a developer carrier 10g according to the present reference example . In addition, the same code | symbol is attached | subjected about the structure similar to Example 1, and the description is abbreviate | omitted. In this reference example , in the developer carrier 10g, an elastic body (elastic member) 23 as shown in FIG. 14 is disposed between the main magnet portion 15a of the magnet member 15 and the inner peripheral surface of the developing roller 10d. Yes. The elastic member 23 is disposed in a region including a portion where the developer carrying member 10g and the photosensitive drum 7 are closest to each other at least in the short direction. Moreover, the elastic body 23 may be arrange | positioned only in the longitudinal direction center part vicinity (central area | region). The elastic body 23 may be a foam such as a foamable polyurethane foam.

(Action when an impact is applied to the developer carrier)
As in the first embodiment, the process cartridge B may receive an impact due to dropping in the course of physical distribution or the like. In such a case, due to its own weight, the magnet member 15 bends in the main magnet portion 15a with the shaft portions 15b and 15c at both ends in the longitudinal direction as fulcrums. At this time, the bending of the main magnet portion 15a can be reduced (the amount of bending is restricted) by the elastic body 23 arranged in the gap between the inner peripheral surface of the developing roller 10d and the main magnet portion 15a. Thereby, the bending of the central portion in the longitudinal direction of the developing roller 10d due to the main magnet portion 15a coming into contact with the inner peripheral surface of the developing roller 10d is reduced. As a result, in the central portion in the longitudinal direction of the developing roller 10d, the bending with the contact position between the spacer member 18 provided at both ends in the longitudinal direction and the photosensitive drum 7 as a fulcrum is reduced, and the developing roller 10d is bent. The contact with the photosensitive drum 7 due to is reduced or eliminated.

In this reference example , the elastic body 23 is disposed between the magnet member 15 and the inner peripheral surface of the developing roller 10d. Thus, when an impact such as dropping is applied, the bending of the main magnet portion 15a at the center in the longitudinal direction can be reduced by the elastic body 23, and the main magnet portion 15a at the center in the longitudinal direction of the main magnet portion 15a. And the contact between the inner peripheral surface of the developing roller 10d can be prevented. As a result, the main magnet portion 15a
The bending of the central portion in the longitudinal direction of the developing roller 10d due to the bending of the developing roller 10d can be reduced, and even if the bending direction of the central portion in the longitudinal direction of the developing roller 10d is the photosensitive drum direction, the developing roller 10d and the photosensitive drum 7 Contact can be prevented or reduced.

In the above-described first and reference examples , it is not necessary to arrange a conventional sheet-like protective member as a means for avoiding contact between the developing roller 10d and the photosensitive drum 7, so that the cost increase due to the increase in parts can be reduced. It is possible to avoid an increase in cost due to an increase in assembly man-hours.

7 Photosensitive drum 10d Developing roller 10g Developer carrier 15 Magnet member 15a Main magnet portion 15b One end side shaft portion 15c Other end side shaft portion B Process cartridge

Claims (2)

A process cartridge detachably attached to the image forming apparatus,
An image carrier on which an electrostatic latent image is formed;
A developing roller provided on the image bearing member via a gap; and a magnet member provided on the inner circumferential side of the developing roller and provided on the inner circumferential surface of the developing roller via the gap. A developer carrier;
A support portion for supporting the magnet member;
With
The magnet member is
A magnet body,
Wherein provided on both end sides in the axial direction of the rotation axis of the developing roller with respect to the magnet main body, and the supported portion supported by the supporting portion,
Protruding portions provided on both end sides of the magnet member in the axial direction, projecting from the magnet main body toward the inner peripheral surface of the developing roller, and spaced from the inner peripheral surface;
Have
The size of the gap between the inner peripheral surface of the developing roller and the protruding portion is smaller than the size of the gap between the inner peripheral surface of the developing roller and the magnet body portion ,
The support portion supports the supported portion inside the developing roller and inside the end portion in the axial direction of the developing roller,
The process cartridge according to claim 1, wherein the projecting portion is located further inward in the axial direction than the supported portion, and can contact the inner peripheral surface of the developing roller when the magnet member is bent . A developing frame having the developer carrying member disposed therein, the developer containing unit containing the developer, and the developer contained in the developer containing unit being supplied to the developer carrying member. A developing frame having a plurality of openings,
The protrusion A process according to claim 1, characterized in that the opening between the two virtual area which is perpendicular to the axial direction of the rotating shaft includes the protruded portion is provided so as to be located cartridge.

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