Image carrier unit and image forming apparatus equipped with same

Abstract

To provide an image carrier unit that prevents deformation of an image carrier, can stably maintain the grounding state of the image carrier to the ground, and prevents an increase in manufacturing cost.SOLUTION: An image carrier unit of the present invention comprises: an image carrier, a flange member, a shaft member, and a ground member. The ground member has a first bottom plate part that is fixed to the flange member, and a pair of leaf spring parts that erect from the first bottom plate part in an insertion direction. The first bottom plate part has a first projection that extends to approach the shaft member and is electrically connected with the shaft member. The leaf spring parts each have a first spring piece that extends in the insertion direction and a second spring piece that is folded to the outside in a radial direction of the image carrier from a leading end of the first spring piece via a second bent part and extends in a direction opposite to the insertion direction to approach the first bottom plate part. The interval between the second bent parts of the leaf spring parts before being inserted into the image carrier is smaller than the inner diameter of the image carrier, and the interval between the leading ends of the second spring pieces is larger than the inner diameter of the image carrier.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile, and more particularly to an image carrier unit including an image carrier that carries an electrostatic latent image, and an image forming apparatus equipped with the same. [Background technology]

[0002] In a conventional image forming apparatus using an electrophotographic process, an electrostatic latent image is formed on a uniformly charged image carrier, and this electrostatic latent image is developed into a toner image to form an image on paper (recording medium).

[0003] Such image forming devices are equipped with an image carrier unit having a structure for dissipating charge accumulated in the image carrier body to the main body of the image forming device in order to maintain a predetermined amount of charge on the surface of the image carrier (Patent Document 1, Patent Document 2).

[0004] The image carrier unit of Patent Document 1 comprises an image carrier, a flange member that is fitted into openings at both ends of the image carrier, a shaft member that passes through the flange member, and an earth member that is arranged between the image carrier and the shaft member.

[0005] The earth member has a bottom plate portion fixed to a portion of the flange member located inside the image carrier, a pair of claw portions extending from the bottom plate portion toward the inner circumferential surface of the image carrier, and a pair of contact pieces extending toward the shaft member toward the downstream side in the fitting direction of the flange member. The pair of claw portions face each other in the radial direction of the image carrier, and the tips of each claw portion are in contact with the inner circumferential surface of the image carrier. The tips of the pair of contact pieces are in contact with the shaft member.

[0006] The ground member and the shaft member are made of a conductive material such as metal. Therefore, the image carrier is electrically connected to the shaft member via the ground member. The shaft member is connected to a ground mechanism provided in the image forming apparatus main body, and the image carrier is grounded to the ground via the ground member and the shaft member.

[0007] Here, before the flange member is fitted into the image carrier, the distance between the tips of the claws is greater than the inner diameter of the image carrier. When fitting the flange member into the image carrier, the flange member is pressed into the opening of the image carrier with the claws in contact with the inner peripheral surface of the image carrier. At this time, the inner peripheral surface of the image carrier is pressed with a relatively strong force by the claws. Then, the flange member is fitted into the inside of the image carrier while the claws are deforming.

[0008] The grounding member of the image carrier unit of Patent Document 2 has a pair of leaf spring parts extending from a bottom plate part in a fitting direction of the flange member. The pair of leaf spring parts face each other in a radial direction of the image carrier. The leaf spring parts are folded back in the radial direction via a bent part between the bottom plate part and the leaf spring parts, and have elasticity in the radial direction. The tip of the leaf spring parts is in contact with the inner peripheral surface of the image carrier. As a result, like the image carrier unit of Patent Document 1, the image carrier is grounded to the ground via the earthing member and the shaft member.

[0009] Before the flange member is fixed to the image carrier, the distance between the tips of the leaf spring portions is larger than the inner diameter of the image carrier (Fig. 1 of Patent Document 2). When fitting the flange member into the image carrier, first, the pair of leaf spring portions of the earth member are elastically deformed in the radial direction of the image carrier. In a state in which the leaf spring portions are elastically deformed until the distance between the tips of the leaf spring portions becomes smaller than the inner diameter of the image carrier, the earth member is inserted into the image carrier and the insertion portion is press-fitted into the opening of the image carrier. This causes the flange member to be fitted into the image carrier. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2011-197541 A [Patent Document 2] JP 2007-298909 A Summary of the Invention [Problem to be solved by the invention]

[0011] Incidentally, in the image carrier unit of Patent Document 1, as described above, when the flange member is fitted into the image carrier, the inner peripheral surface of the image carrier is pressed by the claws with a relatively strong force. This pressing force may cause the image carrier to deform. If the photosensitive layer of the image carrier is deformed, it may affect the image output onto the output paper, and may cause deterioration in image quality.

[0012] In addition, as described above, in the image carrier unit of Patent Document 2, when the flange member is fitted into the image carrier, the pair of leaf springs are elastically deformed in the radial direction of the image carrier, and the flange is fitted into the image carrier. When assembling such an image carrier unit, it is necessary to insert the earth member into the opening of the image carrier while keeping the leaf springs in the elastically deformed state, and therefore special tools and devices must be prepared. Therefore, the image carrier unit of Patent Document 2 is difficult to assemble and expensive to manufacture.

[0013] In addition, the earth member of Patent Document 2 is inserted into the image carrier while elastically deforming the leaf spring portion, so that the pressing force that the image carrier receives from the earth member when the flange portion is fitted is relatively weak. This makes it possible to suppress the above-mentioned deformation of the image carrier. However, since the leaf spring portion elastically deforms with the bending portion located between the leaf spring portion and the bottom plate portion as a fulcrum, there is a risk that the bottom plate portion will bend due to the elastic deformation of the leaf spring portion. This may cause the position of the contact piece extending from the bottom plate portion to shift, cutting off the electrical connection between the shaft member and the earth member, and causing the image carrier to not be grounded to the ground. For this reason, the image carrier unit of Patent Document 2 has an unstable grounding state of the image carrier to the ground.

[0014] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide an image carrier unit that can suppress deformation of an image carrier, stably maintain the contact state of the image carrier with the ground, and suppress an increase in manufacturing costs. [Means for solving the problem]

[0015] In order to achieve the above object, the image carrier unit of the present invention includes an image carrier, a flange member, a shaft member, and an earth member. The image carrier is cylindrical with a photosensitive layer formed on its outer circumferential surface and openings at both ends. The flange member is non-conductive, has an insertion portion that is fitted into the opening of the image carrier and a through hole along the rotation center of the image carrier, and is fixed to both ends of the image carrier. The shaft member is inserted into the through hole of the flange member. The earth member is fixed to the flange member and electrically connects the image carrier and the shaft member. The earth member has a first bottom plate portion that is fixed to the tip of the insertion portion in the insertion direction, and a pair of leaf spring portions that rise from the first bottom plate portion in the insertion direction via a first bent portion and face each other in the radial direction of the image carrier perpendicular to the insertion direction. The first bottom plate portion has a first protrusion portion that extends toward the through hole so as to approach the shaft member and is electrically connected to the shaft member. The leaf spring portion has a first spring piece extending from the first bent portion in the fitting direction, and a second spring piece that is folded back from a tip of the first spring piece via a second bent portion toward the outside in the radial direction of the image carrier and extends in the opposite direction to the fitting direction so as to approach the first bottom plate portion. The distance between the second bent portions of each leaf spring portion before being inserted into the image carrier is smaller than the inner diameter of the image carrier, and the distance between the tip portions of the second spring pieces is larger than the inner diameter of the image carrier. Effect of the Invention

[0016] According to the first configuration of the present invention, the flange member contacts the inner peripheral surface of the image carrier via the leaf spring portion. The leaf spring portion is folded back at a first bent portion and a second bent portion, and is elastically deformable with the first bent portion and the second bent portion as fulcrums. In this way, the earth member and the inner peripheral surface of the image carrier contact each other via the elastically deformable leaf spring portion, so that when the flange member is fitted into the image carrier, the pressing force that the inner peripheral surface of the image carrier receives from the leaf spring portion of the earth member is relatively weak, making it possible to suppress deformation of the image carrier.

[0017] In addition, since the distance between the second bent portions of each leaf spring before being inserted into the image carrier is smaller than the inner diameter of the image carrier, when fitting the flange member into the image carrier, the earth member can be inserted into the image carrier without using a special tool, etc. This makes it possible to prevent deterioration of assembly and increase in manufacturing costs.

[0018] Furthermore, the leaf spring portion has a first spring piece that is folded back at a first bent portion and a second spring piece that is folded back at a second bent portion, so that the effect of the elastic deformation of the leaf spring portion can be dispersed to two locations, the first bent portion and the second bent portion. As a result, the first bottom plate portion is less susceptible to the effect of the elastic deformation of the leaf spring portion and is less likely to bend. This makes it possible to stably maintain the grounding state of the image carrier to the ground.

[0019] Therefore, it is possible to provide an image carrier unit that can suppress deformation of the image carrier, stably maintain the grounded state of the image carrier, and suppress an increase in manufacturing costs. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus 100 according to a first embodiment of the present invention. [Diagram 2] An enlarged view of the image forming section Pa in FIG. [Diagram 3] FIG. 1 is a perspective view showing a drum unit 40a. [Figure 4] FIG. 4 is a perspective view showing a cross section of one end of the drum unit 40a taken along the center of the shaft member 53a. [Diagram 5] FIG. 5(a) is a cross-sectional view of the drum unit 40a taken along shaft members 53a and 53b, and FIG. 5(b) is a cross-sectional view of the drum unit 40a taken along the line AA in FIG. 5(a). [Figure 6] An enlarged cross-sectional view showing the vicinity of the engagement portion 64 [Figure 7]FIG. 7(a) is a cross-sectional view showing a state before the flange member 51a is fitted into the drum body 50, and FIG. 7(b) is a cross-sectional view showing a state after the flange member 51a has been fitted into the drum body 50. [Figure 8] FIG. 11 is a cross-sectional view showing the other end portion of the drum main body 50 of the drum unit 40a according to the second embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, a drum unit according to the first embodiment will be described with reference to Figs. 1 to 7. Fig. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus 100 according to the first embodiment of the present invention, and Fig. 2 is an enlarged view of the vicinity of an image forming section Pa in Fig. 1. In this embodiment, the image forming apparatus 100 is configured as a four-tandem color printer that forms images by arranging four photoconductor drums 1a, 1b, 1c, and 1d corresponding to four different colors (magenta, cyan, yellow, and black) in parallel.

[0022] Four image forming units Pa, Pb, Pc, and Pd are arranged in order from the left side in Fig. 1 within the main body of the image forming apparatus 100. These image forming units Pa to Pd are provided corresponding to images of four different colors (magenta, cyan, yellow, and black), and sequentially form images of magenta, cyan, yellow, and black through the processes of charging, exposing, developing, and transferring, respectively.

[0023] Photoconductor drums 1a to 1d carrying visible images (toner images) of each color are provided in these image forming stations Pa to Pd, respectively. Furthermore, an intermediate transfer belt 8 rotating counterclockwise in FIG. 1 is provided adjacent to each of the image forming stations Pa to Pd.

[0024] The paper P onto which the toner image is transferred is stored in a paper cassette 16 disposed at the bottom of the image forming apparatus 100. The paper P is transported to the secondary transfer roller 9 via a paper feed roller 12a and a pair of registration rollers 12b. The intermediate transfer belt 8 is made of a sheet of dielectric resin, and is generally a seamless belt. The intermediate transfer belt 8 and the secondary transfer roller 9 are driven to rotate at the same linear speed as the photosensitive drums 1a to 1d by a belt drive motor (not shown). In addition, a blade-shaped belt cleaner 19 is disposed downstream of the secondary transfer roller 9 to remove toner and the like remaining on the surface of the intermediate transfer belt 8.

[0025] Next, the image forming units Pa to Pd will be described. The image forming unit Pa will be described in detail below, but the image forming units Pb to Pd will not be described because they have basically the same configuration. As shown in Fig. 2, a charging device 2a, a developing device 3a, and a cleaning device 7a are arranged around the photosensitive drum 1a in the drum rotation direction (clockwise direction in Fig. 2), and a primary transfer roller 6a is arranged with an intermediate transfer belt 8 sandwiched therebetween.

[0026] The charging device 2a has a charging roller 21 that contacts the photosensitive drum 1a and applies a charging bias to the drum surface, and a charging cleaning roller 23 that cleans the charging roller 21. The developing device 3a has two stirring and conveying members 25 consisting of a stirring and conveying screw and a supply and conveying screw, and a magnetic roller 27 (developing roller) that is disposed opposite the photosensitive drum 1a and supplies toner to the photosensitive layer on the surface of the photosensitive drum 1a, and develops the electrostatic latent image into a toner image by bringing a two-component developer (magnetic brush) carried on the surface of the magnetic roller 27 into contact with the surface of the photosensitive drum 1a.

[0027] The cleaning device 7a has a rubbing roller 30, a cleaning blade 31, and a recovery spiral 33. The rubbing roller 30 is pressed against the photosensitive drum 1a with a predetermined pressure, and is driven to rotate in the same direction as the photosensitive drum 1a at the contact surface with the photosensitive drum 1a by a drum cleaning motor (not shown), and its linear speed is controlled to be faster (here, 1.2 times) than the linear speed of the photosensitive drum 1a.

[0028] The photoconductor drum 1a, the charging device 2a, and the cleaning device 7a are unitized. In each of the image forming stations Pa to Pd, the unit consisting of the photoconductor drums 1a to 1d, the charging devices 2a to 2d, and the cleaning devices 7a to 7d will be referred to as drum units 40a to 40d below.

[0029] Next, the image forming procedure in the image forming apparatus 100 will be described. When image data is input from a higher-level device such as a personal computer, first, the surfaces of the photoconductor drums 1a-1d are uniformly charged by the charging devices 2a-2d. Next, the exposure unit 5 irradiates light based on the image data, and an electrostatic latent image corresponding to the image data is formed on each of the photoconductor drums 1a-1d. The developing devices 3a-3d are filled with a predetermined amount of two-component developer containing toner of each color, magenta, cyan, yellow, and black.

[0030] When the ratio of toner in the two-component developer filled in each of the developing devices 3a to 3d falls below a specified value due to the formation of a toner image described later, the developer is replenished from the containers 4a to 4d to each of the developing devices 3a to 3d. The toner in the developer is supplied onto the photoconductor drums 1a to 1d by the developing devices 3a to 3d, and electrostatically adheres to the photoconductor drums 1a to 1d, forming a toner image corresponding to the electrostatic latent image formed by exposure of the exposure unit 5.

[0031] Then, a predetermined transfer voltage is applied between the primary transfer rollers 6a-6d and the photoconductor drums 1a-1d by the primary transfer rollers 6a-6d. As a result, the magenta, cyan, yellow, and black toner images on the photoconductor drums 1a-1d are primarily transferred onto the intermediate transfer belt 8. Thereafter, in preparation for the subsequent formation of a new electrostatic latent image, the toner remaining on the surfaces of the photoconductor drums 1a-1d is removed by the cleaning devices 7a-7d.

[0032] When the intermediate transfer belt 8 starts to rotate counterclockwise in accordance with the rotation of the drive roller 11 by a belt drive motor (not shown), the paper P stored in the paper cassette 16 at the bottom of the main body of the image forming apparatus 100 is transported at a predetermined timing from the registration roller pair 12b to a nip portion (secondary transfer nip portion) between the intermediate transfer belt 8 and a secondary transfer roller 9 provided adjacent to the intermediate transfer belt 8. Then, a full-color image is secondarily transferred onto the paper P at the nip portion. The paper P to which the toner image has been transferred is transported to the fixing device 13.

[0033] The paper P conveyed to the fixing device 13 is heated and pressurized as it passes through the nip portion (fixing nip portion) of the pair of fixing rollers 13a, so that the toner image is fixed onto the surface of the paper P, and a predetermined full-color image is formed. The paper P on which the full-color image has been formed is discharged onto the discharge tray 17 by the pair of discharge rollers 15 as is (or after being diverted to the reversing conveying path 18 by the branching portion 14 and images are formed on both sides).

[0034] The layout inside the main body of the image forming apparatus 100 can be changed as appropriate as long as the rotation directions of the photosensitive drums 1a-1d and the intermediate transfer belt 8 and the transport path of the paper P can be appropriately set. For example, it is of course possible to reverse the rotation directions of the photosensitive drums 1a-1d and the intermediate transfer belt 8 from this embodiment, and to reverse the positional relationship between the drum units 40a-40d and the developing devices 3a-3d from this embodiment, and to set the transport path of the paper P accordingly.

[0035] Next, the drum unit 40a will be described in detail. Fig. 3 is a perspective view showing the drum unit 40a. The drum units 40b to 40d are basically configured similarly to the drum unit 40a, and therefore their description will be omitted. As shown in Fig. 3, the drum unit 40a has a unit housing 41 that holds the photosensitive drum 1a, the charging device 2a, and the cleaning device 7a. A shaft member 53a that serves as the axis of the rotation center of the photosensitive drum 1a protrudes from one end side of the drum unit 40a (the front right side in Fig. 3).

[0036] Furthermore, a toner discharge portion 43 of the cleaning device 7a protrudes from one end side (the front right side in FIG. 3) of the drum unit 40a. Waste toner collected from the surface of the photosensitive drum 1a by the cleaning device 7a is discharged from the toner discharge portion 43 by the rotation of the collection spiral 33 (see FIG. 2) and transported to a developer collection container (not shown).

[0037] FIG. 4 is a perspective view showing a cross section of one end of the drum unit 40a cut along the center of the shaft member 53a. FIG. 5(a) is a cross section of the drum unit 40a according to the first embodiment of the present invention cut along the shaft members 53a and 53b. FIG. 5(b) is a cross section of the drum unit 40a cut along the AA cross section line in FIG. 5(a). FIG. 6 is an enlarged cross section showing the vicinity of the engagement portion 64 provided on the earth member 58. Note that the basic structure of one end side and the other end side of the drum unit 40a are the same, so only the one end side will be described for the common parts, and the other end side will not be described. Regarding the other end side, only the parts different from the one end side will be described.

[0038] As shown in FIG. 4, FIG. 5(a), and FIG. 5(b), the photosensitive drum 1a has a cylindrical drum main body 50 (image carrier), flange members 51a, 51b attached to both ends of the drum main body 50, and shaft members 53a, 53b that rotatably support the flange members 51a, 51b. The drum main body 50 is a hollow cylinder with openings 52 formed at both ends. The drum main body 50 is formed by laminating a photosensitive layer on the outer circumferential surface of an aluminum drum tube. The photosensitive layer may be, for example, an organic photosensitive layer (OPC) using an organic photoconductor, or an inorganic photosensitive layer such as an amorphous silicon photosensitive layer formed by deposition of silane gas or the like.

[0039] The flange members 51a and 51b are cylindrical members made of a non-conductive material such as resin. The flange members 51a and 51b are arranged on both ends of the drum body 50 in the axial direction, one at a time. Specifically, the flange member 51a is arranged on one end side (the right side in the figure), and the flange member 51b is arranged on the other end side (the left side in the figure). The flange members 51a and 51b have insertion parts 54 that are inserted into openings 52 formed on both ends of the drum body 50, and a through hole 49 is formed that penetrates along the central axis of the drum body 50. The outer diameter of the insertion part 54 is slightly larger than the inner diameter of the drum body 50. The flange members 51a and 51b are fixed to the drum body 50 by press-fitting the insertion part 54 into the opening 52. The insertion part 54 has a rib 55 that rises from the opening edge of the through hole 49. A plurality of fixing protrusions 56 that protrude in the insertion direction are provided on the end of the insertion part 54 in the insertion direction.

[0040] The shaft members 53a and 53b are made of a metal material. The shaft members 53a and 53b are rotatably supported by bearings 73 provided in the unit housing 41 (see Figs. 5(a) and 5(b)). The shaft members 53a and 53b are disposed at both ends of the drum main body 50. Specifically, the shaft member 53a is disposed at one end (the right side in the figure), and the shaft member 53b is disposed at the other end (the left side in the figure).

[0041] The outer diameter of the shaft members 53a, 53b is equal to or slightly larger than the inner diameter of the through hole 49 of the flange members 51a, 51b. The shaft members 53a, 53b are press-fitted into the through hole 49 of the flange members 51a, 51b, and thereby fixed to the flange members 51a, 51b.

[0042] A shaft member 53b provided on the other end side of the drum main body 50 is connected to a grounding mechanism (such as a metal frame (not shown)) provided in the main body of the image forming apparatus 100, and is grounded to the ground.

[0043] 5(b), a substrate portion 74 is provided near the shaft member 53a on one end side of the drum main body 50. The substrate portion 74 is disposed inside the unit housing 41, and controls the rotation speed, etc. of the photosensitive drum 1a.

[0044] An earth member 58 made of a conductive material such as metal is disposed between the drum body 50 and the flange members 51a and 51b. The earth member 58 has a first bottom plate portion 59 and a pair of leaf spring portions 60.

[0045] The first bottom plate portion 59 is disk-shaped and abuts against an end portion in the fitting direction of the insertion portion 54. The first bottom plate portion 59 has a pair of engagement portions 64 and a pair of first protrusions 61. An engagement hole 57a that penetrates the first bottom plate portion 59 along the central axis of the drum body 50 is formed in the center of the first bottom plate portion 59.

[0046] The pair of engaging portions 64 face each other in the radial direction with the engaging hole 57a therebetween (the other engaging portion 64 is not shown). As shown in Fig. 6, the engaging portion 64 has a rectangular through hole 65 penetrating the first bottom plate portion 59, and a pair of engaging pieces 66 that rise from the edge of the through hole 65 and face each other in the circumferential direction of the engaging hole 57a. Each engaging piece 66 is a rectangular plate-like body. The engaging pieces 66 extend from the edge of the through hole 65 in the fitting direction (upward in Fig. 6) while being inclined.

[0047] The broken line portion in FIG. 6 shows the engagement pieces 66 in a state before the earth member 58 is fixed to the insertion portion 54. Before the earth member 58 is fixed to the insertion portion 54, the distance between the tips of the engagement pieces 66 is smaller than the outer diameter of the fixing protrusions 56. When fixing the earth member 58 to the insertion portion 54, the fixing protrusions 56 are inserted into the through holes 65 of the engagement portions 64. At this time, the fixing protrusions 56 are inserted between the pair of engagement pieces 66 so as to push the pair of engagement pieces 66 apart. The pair of engagement pieces 66 are in contact with the outer peripheral surfaces of the fixing protrusions 56 and press the fixing protrusions 56 so as to sandwich them by their restoring force. Therefore, the fixing protrusions 56 are prevented from coming off.

[0048] Returning to Fig. 5(a) and Fig. 5(b), the pair of first protrusions 61 face each other in the radial direction with the engagement hole 57a therebetween. The first protrusions 61 have a rectangular plate-shaped standing wall portion 62 that rises from the opening edge of the engagement hole 57a in the fitting direction, and a rectangular plate-shaped folded-back portion 63 that is folded back from the tip of the standing wall portion 62 toward the center of the engagement hole 57a. The standing wall portion 62 faces the outer circumferential surface of the rib 55 of the insertion portion 54 in the radial direction. The folded-back portion 63 faces the end face of the rib 55 in the fitting direction.

[0049] As shown in FIG. 5(b), the tip of the folded portion 63 of the ground member 58 disposed on the other end side (left side in the figure) of the drum unit 40a is in contact with the outer circumferential surface of the shaft member 53b.

[0050] On the other hand, the tip of the folded portion 63 of the grounding member 58 arranged on one end side (the right side in the figure) of the drum body 50 is spaced a predetermined distance from the outer circumferential surface of the shaft member 53a. The distance L1 at the point where the tip of the folded portion 63 and the shaft member 53a are closest to each other is smaller than the distance L2 at the point where the base portion 74 and the shaft member 53a are closest to each other.

[0051] 5(a) and 5(b), the leaf spring portion 60 rises from the outer circumferential edge of the first bottom plate portion 59 in the fitting direction (the axial inner side of the drum body 50). The pair of leaf spring portions 60 face each other in the radial direction. The leaf spring portion 60 has a first spring piece 67 and a second spring piece 68.

[0052] The first spring piece 67 is a rectangular plate-like body connected to the outer periphery of the first bottom plate portion 59 via a first bent portion 69. The first spring piece 67 is folded back from the first bottom plate portion 59 toward the inside in the radial direction via the first bent portion 69. In other words, the first spring piece 67 extends closer to the inside in the radial direction as it moves from the first bent portion 69 toward the insertion direction. The first spring piece 67 is a plate spring that is elastically deformable in the radial direction with the first bent portion 69 as a fulcrum.

[0053] The second spring piece 68 is a rectangular plate-like body connected to the tip of the first spring piece 67 via the second bent portion 70. The second spring piece 68 is folded back radially outward via the second bent portion 70. In other words, the second spring piece 68 extends so as to approach the radially outward as it moves from the second bent portion 70 in the direction opposite to the insertion direction (as it approaches the first bottom plate portion 59). The second spring piece 68 is a plate spring that can elastically deform in the radial direction with the second bent portion 70 as a fulcrum. A first contact piece 71 is provided at the tip of the second spring piece 68, which extends radially outward as it approaches the first bottom plate portion 59.

[0054] 5(a) shows the grounding member 58 in a state before the flange member 51b is fitted into the drum body 50. In this state, the distance L3 between the second bent portions 70 is smaller than the inner diameter L4 of the drum body 50. In addition, in this state, the distance L5 between the tip ends (first contact pieces 71) of the second spring pieces 68 is larger than the inner diameter L4 of the drum body 50.

[0055] 4 and 5(b), the leaf spring portion 60 has a slit 72 formed therein, which extends from the tip of the leaf spring portion 60 in the insertion direction toward the first bottom plate portion 59. The slit 72 is formed by cutting out the leaf spring portion 60 from the tip of the leaf spring portion 60, i.e., near the tip of the second spring piece 68 located at the boundary between the first spring piece 67 and the second spring piece 68, passing through the second bent portion 70, the second spring piece 68, and the first spring piece 67, and approaching the first bottom plate portion 59.

[0056] Next, with reference to Figures 7(a) and 7(b), the operation of each part when the flange member 51a is fitted into the drum body 50 will be described in detail. Figure 7(a) is a cross-sectional view showing the state before the flange member 51a is fitted into the drum body 50. Figure 7(b) is a cross-sectional view showing the state after the flange member 51a has been fitted into the drum body 50. The two-dot chain line portion in Figure 7(b) shows the earth member 58 in the state of Figure 7(a) superimposed on the earth member 58 after the flange member 51a has been fitted into it.

[0057] When the flange member 51a is fitted into the opening 52 of the drum body 50, the ground member 58 is first inserted into the drum body 50. When the ground member 58 is inserted to a predetermined position inside the drum body 50, the end of the drum body 50 in the fitting direction comes into contact with the second spring piece 68. When the ground member 58 is further inserted from this state, the pair of leaf spring pieces 60 are elastically deformed toward the inside in the radial direction. That is, the second spring piece 68 is elastically deformed in the radial direction with the second bent portion 70 as a fulcrum. The first spring piece 67 is also elastically deformed in the radial direction with the first bent portion 69 as a fulcrum. When the ground member 58 is further inserted from this state and the insertion portion 54 of the flange member 51a is press-fitted into the opening 52 of the drum body 50, the flange member 51a is fixed to the end of the drum body 50. When the flange member 51a is fixed to the end of the drum body 50, the second spring piece 68 is elastically deformed to a greater extent than the first spring piece 67.

[0058] In this way, when the flange members 51a, 51b are fitted into the opening 52 of the drum body 50, the leaf spring portion 60 elastically deforms radially inward, while the first contact piece 71 comes into contact with the inner peripheral surface of the drum body 50. Therefore, the pressing force from the earth member 58 received by the drum body 50 becomes relatively weak, and deformation of the drum body 50 can be suppressed. This makes it possible to suppress image degradation.

[0059] As described above, before the flange members 51a, 51b are fitted into the drum body 50, the distance L3 between the second bent portions 70 of the leaf spring portion 60 is smaller than the inner diameter L4 of the drum body 50. Furthermore, since the first spring piece 67 and the second spring piece 68 are elastically deformed by contacting the ends of the opening 52 of the drum body 50, there is no need to use a special tool or the like when inserting the ground member 58 into the drum body 50. This makes it possible to prevent deterioration in the ease of assembly of the drum unit 40a.

[0060] Moreover, the leaf spring portion 60 is elastically deformed at two locations, the first bent portion 69 and the second bent portion 70. Therefore, the influence of the deformation of the leaf spring portion 60 is distributed to two locations, the first bent portion 69 and the second bent portion 70, and the first bottom plate portion 59 adjacent to the first bent portion 69 is less affected by the deformation of the leaf spring portion 60. Furthermore, as described above, when the flange member 51a is fixed to the end portion of the drum main body 50, the second spring piece 68 is elastically deformed more than the first spring piece 67. Therefore, the first bottom plate portion 59 is less affected by the elastic deformation of the first spring piece 67, and the deformation of the first bottom plate portion 59 near the first bent portion 69 can be effectively suppressed. Therefore, the shaft members 53a, 53b and the earth member 58 can maintain a stable conductive state.

[0061] Generally, drum units 40a to 40d may be unintentionally charged by static electricity or the like when a user touches them during maintenance work on image forming apparatus 100. If this static electricity flows through substrate 74 provided on drum units 40a to 40d, it may lead to damage to substrate 74.

[0062] To solve such problems, some conventional drum units have a needle-shaped conductive member (lightning rod) disposed opposite the drum body as a means for removing the electric charge. The needle-shaped conductive member is connected to an earthing mechanism provided in the image forming apparatus and is grounded to the ground. Static electricity remaining in the drum unit is discharged to the needle-shaped conductive member, so damage to the substrate can be suppressed. However, such conventional drum units require a separate structure for providing the needle-shaped conductive member, which leads to increased manufacturing costs.

[0063] Here, in the drum unit 40a of the present invention, as described above, the first contact piece 71 of the ground member 58 is in contact with the inner circumferential surface of the drum main body 50. Also, at the other end side of the drum unit 40a, the tip of the folded portion 63 of the first protrusion 61 of the ground member 58 is in contact with the shaft member 53b. Both the ground member 58 and the shaft member 53b are made of a conductive material, and the drum main body 50 is electrically connected to the shaft member 53b on the other end side via the ground member 58. Therefore, the drum main body 50 is grounded to the ground via the ground member 58 and the shaft member 53b on the other end side.

[0064] In addition, the distance L1 at the closest point between the tip of the folded portion 63 and the shaft member 53a on one end is smaller than the distance L2 at the closest point between the board portion 74 and the shaft member 53a. Therefore, if the shaft member 53a is charged, the charge is preferentially discharged toward the folded portion 63 rather than the board portion 74. As described above, the drum main body 50 is grounded. Therefore, the charge discharged from the shaft member 53a to the folded portion 63 is released to the ground from the drum main body 50 via the shaft member 53b on the other end. Therefore, it is possible to prevent the current from flowing from the shaft member 53b on the other end to the board portion 74, causing the board portion 74 to be damaged.

[0065] Next, a drum unit 40a according to a second embodiment of the present invention will be described with reference to Fig. 8. Fig. 8 is a cross-sectional view showing the periphery of one end portion of the drum main body 50 of the drum unit 40a according to the second embodiment.

[0066] 8, the magnetic roller 27 faces the drum body 50. An annular gap forming member 75 is provided on both ends of the magnetic roller 27. The outer peripheral surface of the gap forming member 75 abuts against a non-image forming area 77 located outside the photosensitive layer 76 on the outer peripheral surface of the drum body 50. The gap forming member 75 separates the magnetic roller 27 from the drum body 50 so that a predetermined gap (gap) is formed between the drum body 50 and the magnetic roller 27.

[0067] An earth plate 78 made of a conductive material such as metal is disposed between the drum body 50 and the shaft member 53a on one end side. The earth plate 78 has a second bottom plate portion 79, a pair of second contact pieces 80, and a pair of second protrusions 81.

[0068] The second bottom plate portion 79 abuts against an end portion of the flange member 51a in the fitting direction. An engagement hole 57b is formed in the center of the second bottom plate portion 79, into which the shaft member 53a and the rib 55 of the flange member 51a are inserted.

[0069] The second protrusions 81 face each other in the radial direction with the engagement hole 57b therebetween. The second protrusions 81 rise from the second bottom plate portion 79 in the fitting direction and extend toward the shaft member 53a. A distance L6 between the tip of the second protrusion 81 and the shaft member 53a at a position closest to the tip is closer than a distance L2 (see FIG. 5(b)) between the base plate portion 74 and the shaft member 53a at a position closest to the tip.

[0070] The second contact pieces 80 extend from the outer circumferential edge of the second bottom plate portion 79 toward the inner circumferential surface of the drum body 50. The second contact pieces 80 are lined up in the radial direction with the engagement hole 57b between them. The tip of the second contact piece 80 is in contact with the inner circumferential surface of the drum body 50 at a position that overlaps the non-image forming area 77 in the axial direction of the drum body 50 but does not overlap the gap forming member 75.

[0071] The distance between the tips of the second contact pieces 80 is larger than the inner diameter of the drum body 50 before the earth plate 78 is inserted into the drum body 50. Therefore, when the flange member 51a of the second embodiment is fitted into the drum body 50, the drum body 50 is pressed by a relatively strong force from the second contact piece 80. Here, as described above, the contact point between the inner circumferential surface of the drum body 50 and the second contact piece 80 is located in a position that overlaps with the non-image forming area 77 in the axial direction and does not overlap with the gap forming member 75. Therefore, even if the drum body 50 is deformed at this contact point by the pressing force received from the second contact piece 80, it is unlikely to affect the photosensitive layer 76. In addition, since it is located in a position that does not overlap with the gap forming member 75, it is unlikely to affect the rotation of the drum body 50. Therefore, it is possible to suppress image deterioration.

[0072] The present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present invention. For example, the present invention is not limited to the color printer as shown in Fig. 1, but can also be applied to other image forming apparatuses such as monochrome printers, monochrome and color copiers, and digital multifunction machines (which have various functions such as copying, facsimile, and scanning, and are also called MFPs (Multi Function Peripherals)).

[0073] Furthermore, although the board portion 74 is disposed near the shaft member 53a, the location where it is disposed does not have to be on the unit housing 41, and may be, for example, in the main body of the image forming apparatus 100. Even in this case, the distance L2 at the closest point between the shaft member 53a and the board portion 74 is greater than the distance L1 at the closest point between the shaft member 53a and the earth member 58, or the distance L6 at the closest point between the shaft member 53a and the earth plate 78.

[0074] In addition, a configuration can be adopted in which the outer diameter of shaft members 53a, 53b is equal to or slightly smaller than the inner diameter of through hole 49 in flange members 51a, 51b, and adhesive is applied between the outer peripheral surfaces of shaft members 53a, 53b and the inner peripheral surfaces of through hole 49 to fix shaft members 53a, 53b to flange members 51a, 51b.

[0075] Furthermore, instead of adopting a configuration in which the flange portions 51a, 51b are fixed to the shaft members 53a, 53b as described above, it is possible to adopt a configuration in which the flange portions 51a, 51b are rotatably provided around the shaft members 53a, 53b inserted into the through holes 49 as support axes. In this case, the shaft members 53a, 53b are fixed to the unit housing 41. [Industrial Applicability]

[0076] The present invention can be applied to an image carrier unit to be mounted in an image forming apparatus, and can provide an image carrier unit that suppresses image deterioration and suppresses increases in manufacturing costs. [Explanation of symbols]

[0077] 27 Magnetic roller (developing roller) 40a to 40d Drum unit (image carrier unit) 41 Unit Housing 43 Toner discharge section 49 Through hole 50 Drum body (image carrier) 51a, 51b Flange members 52 Opening 53a, 53b Shaft members 54 Insertion part 58 Earthing member 59 1st bottom plate part 60 Leaf spring part 61 1st protrusion 67 First spring piece 68 Second spring piece 69 1st bending part 70 Second bending part 71 1st contact piece 72 Slit 74 Circuit Board 75 Gap forming member 76 Photosensitive layer 77 Non-image forming area 78 Earth plate 79 2nd bottom plate part 80 Second contact piece 81 2nd protrusion 100 Image forming device

Claims

1. a cylindrical image carrier having a photosensitive layer formed on its outer circumferential surface and openings at both ends; a pair of non-conductive flange members each having an insertion portion that is fitted into the opening of the image carrier and a through hole that is aligned with a rotation center of the image carrier, the flange members being fixed to both ends of the image carrier, a first shaft member that is inserted into the through hole of the flange member that is fixed to one end side of the image carrier; a second shaft member that is separate from the first shaft member, is inserted into the through hole of the flange member that is fixed to the other end side of the image carrier, and is connected to ground; a pair of conductive ground members each fixed to each of the flange members and electrically connected to the image carrier; Equipped with Each of the earth members is A first bottom plate portion fixed to a tip end portion of the insertion portion in a fitting direction; a pair of leaf spring portions that rise from the first bottom plate portion in the insertion direction via a first bent portion and contact an inner circumferential surface of the image carrier, the pair of leaf spring portions facing each other in a radial direction of the image carrier perpendicular to the insertion direction; having the first bottom plate portion has a first protrusion portion extending toward the through hole, The leaf spring portion is a first spring piece extending from the first bent portion in the fitting direction; a second spring piece that is folded back from a tip of the first spring piece toward the outside in the radial direction of the image carrier via a second bent portion and extends in a direction opposite to the insertion direction so as to approach the first bottom plate portion; having a distance between the second bent portions of the leaf spring portions before being inserted into the image carrier is smaller than an inner diameter of the image carrier, and a distance between the tip ends of the second spring pieces is larger than an inner diameter of the image carrier; a substrate portion for controlling the image carrier is disposed at a position closer to the one end than the center of the image carrier, with a first distance being provided between the closest points between the substrate portion and the first shaft member; the first protrusion of the ground member fixed to the flange member on the other end side and the second shaft member are arranged in contact with or in close proximity to each other so as to be electrically connected to each other; a second gap smaller than the first gap is provided between the first protrusion of the ground member fixed to the flange member on the one end side and the first shaft member; An image carrier unit characterized in that the second gap is a gap that allows, when the first shaft member is charged, electrical conductivity between the earth member on the one end side and the first shaft member via the first protrusion portion, thereby allowing a discharge current to flow from the first shaft member to the earth member on the one end side.

2. 2 . The image carrier unit according to claim 1 , wherein the leaf spring portion has a slit that extends from near the tip of the second spring piece, through the second bent portion and the first spring piece, and reaches the first bottom plate portion.

3. 3. The image carrier unit according to claim 1, wherein the leaf spring portion has a first contact piece that extends from a tip end of the second spring piece and contacts an inner circumferential surface of the image carrier.

4. 4. An image forming apparatus comprising the image carrier unit according to claim 1.

5. a cylindrical image carrier having a photosensitive layer formed on its outer circumferential surface and openings at both ends; a pair of non-conductive flange members each having an insertion portion that is fitted into the opening of the image carrier and a through hole that is aligned with a rotation center of the image carrier, the flange members being fixed to both ends of the image carrier, a first shaft member that is inserted into the through hole of the flange member that is fixed to one end side of the image carrier; a second shaft member that is separate from the first shaft member, is inserted into the through hole of the flange member that is fixed to the other end side of the image carrier, and is connected to ground; a conductive earth plate fixed to the flange member fixed to the one end side and electrically connected to the image carrier; a conductive earth member fixed to the flange member fixed to the other end side, and electrically connecting the second shaft member and the image carrier; Equipped with a substrate portion for controlling the image carrier is disposed at a position closer to the one end than the center of the image carrier, with a first distance being provided between the closest points between the substrate portion and the first shaft member; The earth member is A first bottom plate portion fixed to a tip end portion of the insertion portion in a fitting direction; a pair of leaf spring portions that rise from the first bottom plate portion in the insertion direction via a first bent portion and contact an inner circumferential surface of the image carrier, the pair of leaf spring portions facing each other in a radial direction of the image carrier perpendicular to the insertion direction; having the first bottom plate portion has a first protrusion portion that extends toward the through hole and approaches the first shaft member, and that contacts or is in close proximity to the first shaft member so that the first bottom plate portion and the first shaft member are electrically connected; The leaf spring portion is a first spring piece extending from the first bent portion in the fitting direction; a second spring piece that is folded back from a tip of the first spring piece toward the outside in the radial direction of the image carrier via a second bent portion and extends in a direction opposite to the insertion direction so as to approach the first bottom plate portion; having a distance between the second bent portions of the leaf spring portions before being inserted into the image carrier is smaller than an inner diameter of the image carrier, and a distance between the tip ends of the second spring pieces is larger than an inner diameter of the image carrier; The earth plate is a second bottom plate portion fixed to an end portion of the insertion portion in the insertion direction; a second contact piece that extends from the second bottom plate portion toward an inner peripheral surface of the image carrier and contacts the inner peripheral surface of the image carrier at a position that overlaps a non-image area that is located axially outside the photosensitive layer of the image carrier; a second protrusion extending from the second bottom plate portion toward the first shaft member and opposed to the first shaft member with a second gap therebetween that is smaller than the first gap; having An image carrier unit characterized in that the second gap is a gap that allows electrical conduction between the earth plate and the first shaft member via the second protrusion portion when the first shaft member becomes charged, thereby allowing a discharge current to flow from the first shaft member to the earth plate.

6. An image forming apparatus comprising the image carrier unit according to claim 5 .

7. a developing roller disposed opposite the image carrier and having a developing area for supplying toner to the photosensitive layer; a gap forming member provided at each end of the developing roller in the axial direction and in contact with a non-image area of ​​the image carrier; Equipped with 7. The image forming apparatus according to claim 6, wherein the ground plate contacts the inner peripheral surface of the image carrier at a position not overlapping with the gap forming member in the axial direction.

Images