JP2004078243A - Drum unit and grounding plate used for drum unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reliably connect a drum unit and a device main body electrically without impairing the circularity of a drum pipe stock. <P>SOLUTION: This drum unit is provided with: a drum pipe stock 31 having apertures at both ends; flange members 32 press-fit into the aperture 33 of the drum pipe stock 31; and a conductive grounding plate 37. The grounding plate has: a disk base material 38 which has a fitting hole in the center and has a diameter smaller than the internal diameter of the drum pipe stock 31; a 1st pawl member 42 which is formed of an elastic member projected from the outer circumference of the disk base material; and a folded part 48 which is formed by bending the outer circumferential part of the fitting hole of the disk base material inward and to the opposite side from a fitting surface for a flange member and whose tip part reaches a position corresponding to the fitting hole. The tip of the 1st pawl member is fitted to the inner surface of the flange member while positioned outside the aperture inner diameter of the drum pipe stock. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a drum unit used in an image forming apparatus such as a copying machine, a laser printer, and a facsimile, and an earth plate used in the drum unit.

In an image forming apparatus such as a copying machine, an original is generally read by an exposure unit to form an electrostatic latent image on a photosensitive drum. A developing device for forming a toner image is provided around the photosensitive drum. The developing device charges the toner supplied from the toner hopper with a polarity opposite to that of the electrostatic latent image on the photosensitive drum, and attaches the toner to the surface of the photosensitive drum via a developing sleeve to visualize the image. I have.

The photosensitive drum has a drum tube made of conductive metal in a cylindrical shape, and a flange member which is press-fitted into both ends of the drum tube to form a bearing. A through-hole is provided in the center of the flange member, and a spindle supporting the drum unit is inserted into the through-hole. In order to achieve conduction between the drum tube and the main body of the apparatus, it is conceivable to attach a ground plate to the flange member, whose outer end abuts on the inner surface of the drum tube and whose inner end abuts on the support shaft. Can be However, since the drum tube is made of aluminum or the like whose surface is coated with an oxide insulating film to prevent corrosion, the outer peripheral edge of the ground plate should be in contact with the ground plate in order to establish conduction with the ground plate. It is necessary to remove the oxide insulating film.

In order to simplify this work, an earth plate whose outer peripheral end is located outside the inner diameter of the drum tube is attached to the inner surface of the flange member. There is a configuration in which an end portion is configured to be press-fitted while damaging the inner peripheral surface of a drum tube (for example, Patent Documents 1 and 2).
JP-A-4-356090 JP-A-6-130874

In the drum unit described above, when the flange member provided with the ground plate is press-fitted into the drum tube, the drum tube may be deformed and the roundness may be reduced. In particular, when the thickness of the drum tube is reduced, the roundness of the drum unit is significantly reduced. For this reason, it is difficult to reduce the cost by reducing the thickness of the drum tube, and there is a limit to the weight reduction of the apparatus.

An object of the present invention is to provide a drum unit and a ground plate used for the drum unit, which enable reliable conduction between the drum unit and the apparatus body without impairing the roundness of the drum tube.

The drum unit according to claim 1 includes a drum base tube having openings at both ends, a flange member pressed into the opening of the drum base tube, and a conductive ground plate. The ground plate has a mounting hole in the center, a disk base member having a diameter smaller than the inner diameter of the drum base, a first claw member formed of an elastic member protruding from the outer periphery of the disk base member, and a circle. A bent portion formed by bending an outer peripheral portion of the mounting hole of the plate base material on the opposite side to the mounting surface to the flange member and inwardly, and a tip end reaches a position corresponding to the mounting hole, The first claw member is attached to the inner surface of the flange member such that the tip of the first claw member is located outside the inner diameter of the opening of the drum tube.

In this case, when the flange member is pressed into the opening of the drum tube, the tip of the first claw member of the ground plate is inserted while damaging the inner surface of the drum tube, and is inserted into the inner surface of the drum tube. By peeling off the formed oxide insulating film, conduction between the ground plate and the drum tube is achieved. At this time, the first claw member is elastically deformed in the opening of the drum tube, so that no extra force is applied to the drum tube, and the roundness is reduced even if the drum tube has a small thickness. Damage can be prevented.

According to a second aspect of the present invention, in the drum unit of the first aspect, the ground plate has a recess formed on both sides of the first claw member in a plan view, the recess being formed inward from the outer diameter of the disk base material. I have.

According to a third aspect of the present invention, in the drum unit according to the first or second aspect, the flange member has a projection for attaching an earth plate on the inner surface side, and the earth plate has an attachment hole corresponding to the projection of the flange member. A second claw member protruding in the inner circumferential direction is formed in the mounting hole.

An earth plate used in the drum unit according to claim 4, wherein the drum unit includes: a drum base tube having openings at both ends; and a flange member pressed into the opening of the drum base tube. It is for conducting with the base tube, and is formed of a disk base material having a mounting hole in the center and having a diameter smaller than the inner diameter of the drum base tube, and an elastic member protruding from the outer periphery of the disk base material. A first claw member and a fold formed by bending an outer peripheral portion of the mounting hole of the disc base material inward on a side opposite to a mounting surface to the flange member and reaching a position corresponding to the mounting hole at the tip end. The first claw member is attached to the inner surface of the flange member such that the tip of the first claw member is located outside the inner diameter of the opening of the drum tube.

The earth plate used in the drum unit according to claim 5 is the earth plate according to claim 4, wherein recesses are formed on both sides of the first claw member in a plan view so as to be recessed inward from the outer diameter of the disk base material. Have been.

The earth plate used in the drum unit according to claim 6 is the earth plate according to claim 4 or 5, wherein the flange member has a projection for attaching the earth plate on the inner surface side, and is provided corresponding to the projection of the flange member. The mounting hole further includes a second claw member protruding in the inner circumferential direction.

ド ラ ム The drum unit according to the present invention can ensure electrical conduction of the drum unit.

FIG. 1 is a longitudinal sectional view of a copying machine to which an embodiment of the present invention is applied. As shown in FIG. 1, the copying machine 1 is provided with an exposure section 5 for reading a document at an upper portion thereof. The exposure unit 5 includes a light source, a mirror, a lens unit, and the like. Further, an image forming unit 6 for forming a toner image of the read original is provided in the center of the copying machine 1. The image forming section 6 has a photosensitive drum 7 on the surface of which an electrostatic latent image is formed. Around the photosensitive drum 7, a charging device 8, a developing device 9, a transfer separation device 10, and a cleaning device 11 are arranged.

給 紙 A paper supply unit 12 is provided below the copying machine 1. The paper supply unit 12 includes a bypass table 13 provided on the right side of FIG. 1 of the copying machine 1, three paper supply cassettes 14, 15, 16 and a large paper supply cassette 17 arranged vertically below the copier 1. And a sheet feeding device 18 for conveying the sheets stored in the bypass table 13 or the sheet cassettes 14 to 17 to the image forming unit 6. Downstream of the image forming unit 6 in the sheet conveyance direction, a sheet discharge conveyance path 19 for conveying the sheet to the left side of the apparatus in FIG. 1, a fixing device 20 for fusing and fixing the toner image on the sheet, and a sheet for fixing. A discharge roller 21 for discharging paper and a paper discharge tray 22 for receiving paper are provided. A toner hopper 23 for supplying toner is attached to the developing device 9. A toner cartridge 24 is detachably mounted on the toner hopper 23.

(2) The photosensitive drum 7 has a drum tube 31 and a pair of flange members 32 as shown in FIG. The drum tube 31 is formed by forming a conductive metal into a cylindrical shape, and for example, a drum in which a photosensitive layer of an organic photoreceptor (OPC) is formed on an outer peripheral surface of an aluminum base material is employed. Openings 33 are formed at both ends of the drum tube 31, and a flange fitting portion 34 having a predetermined thickness and a small thickness is formed at the opening end.

The flange member 32 is formed in a substantially disc shape by ABS resin, and has an outer diameter substantially equal to the inner diameter of the flange fitting portion 34 of the drum tube 31. On the inner surface side (seven places) of the flange member 32, a projection 36 for attaching an earth plate is protruded. Further, a through hole 35 is formed in the protrusion 36 protruding from the center of the flange member 32 so as to be fitted to a support shaft provided on the apparatus main body for supporting the drum unit. Further, the outer peripheral surface of the flange member 32 constitutes a contact portion 46 to be inserted into the flange fitting portion 34 of the drum tube 31, and the inner surface side is chamfered corresponding to a concave portion of an earth plate described later. A chamfered portion 47 is formed.

ア ー ス An earth plate 37 made of stainless steel is attached to the inner surface of the flange member 32. The ground plate 37 has a disk base material 38 having an outer diameter smaller than the inner diameter of the flange fitting portion 34 of the drum tube 31. In addition, mounting holes 39 and 40 and a groove 41 are provided on the ground plate 37 so as to correspond to the protrusions 36 of the flange member 32. The attachment holes 39 and 40 are provided with second claw members 44 and 45 protruding in the inner circumferential direction.

ア ー ス Further, the ground plate 37 is provided with a plurality of first claw members 42 whose tips project from the outer periphery of the disk base material 38. The first claw member 42 is configured so that its tip is located outside the inner diameter of the flange fitting portion 34 of the drum tube 31, and can be elastically deformed by recesses 43 provided on both sides in plan view. I have.

The base material above the mounting hole 39 at the center of the ground plate 37 has a bent portion 48 bent to the side opposite to the mounting surface to the flange member 32, and the tip of the bent portion 48 is located at the center. Has reached the position corresponding to the mounting hole 39. The support shaft comes into contact with the distal end of the bent portion 48 to make electrical contact.

The ground plate 37 is attached to the inner surface of the flange member 32 by fitting the mounting holes 39 and 40 into the projections 36 of the flange member 32. At this time, since the second claw members 44 and 45 provided in the mounting holes 39 and 40 are engaged with the protrusions 36 of the flange member 32 while being elastically deformed, the ground plate 37 is stably mounted on the inner surface of the flange member 32. Fixed.

The flange member 32 to which the earth plate 37 is attached is press-fitted into the opening 33 of the drum tube 31. At this time, the first claw member 42 of the ground plate 37 is pressed in while damaging the inner surface of the drum tube 31. Therefore, the oxide insulating film on the inner surface of the drum tube 31 is peeled off by the first claw member 42, and the first claw member 42 abuts on the inner peripheral surface of the flange fitting portion 34 of the drum tube 31, and is elastically deformed. Electrical conduction between the plate 37 and the drum tube 31 is achieved.

後 After the flange members 32 are attached to both ends of the drum tube 31, the through holes 35 are fitted to the support shafts provided in the apparatus main body. At this time, since the support shaft comes into contact with the tip of the bent portion 48 provided on the ground plate 37, electrical conduction between the ground plate 37 and the support shaft is obtained. The electrical connection between the drum unit and the apparatus main body can be performed by electrically connecting the drum unit to the apparatus main body through the support shaft.

The thickness of the drum tube 31 is set to 0.8 mm, and the thickness of the earth plate 37 is set to 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, and 0.5 mm. Assuming that the margins are 0.1 mm, 0.2 mm, and 0.3 mm, respectively, the results of measuring the presence / absence of a decrease in the roundness of the drum, the electrical continuity between the flange and the drum, the number of locations where the tip of the claw hangs, and the number of scratches on the drum inner diameter are shown It is shown in Table 1.

In this experiment, the number of spots where the tip of the claw occurred, the number of scratches on the inner diameter of the drum, and the state of the scratches on the inner diameter of the drum were evaluated as parameters to secure the safety factor during actual use. Includes parameters that depend on drum specifications.

Table 2 shows the measurement results of only the deterioration of the accuracy of the drum and the conduction state between the flange and the drum.

As a result, the relationship between the thickness of the ground plate and the press-fitting allowance, which does not decrease the accuracy of the drum and provides good conduction between the flange and the drum, is as shown in FIG. Assuming that the thickness of the earth plate is X and the press-in allowance is Y, an earth plate having a range of 0.2 mm ≦ X ≦ 0.4 mm and a range of 0.1 mm ≦ Y ≦ −2.5X + 1.2 mm was used. Occasionally, a decrease in drum accuracy can be prevented, and a ground plate with good conduction between the flange and the drum can be obtained.

Although the photoconductor drum used in the copying machine has been described above, the invention can be similarly applied to a photoconductor drum used in a laser printer, a facsimile machine, or the like. Further, the present invention can be applied to various types such as a drum base tube made of stainless steel as a base material, and a photosensitive layer formed of an inorganic photosensitive material on the outer peripheral surface.

銅 If copper or copper alloy is used as the ground plate, the accuracy of the drum tube can be further prevented from lowering.

FIG. 1 is a longitudinal sectional view of a copying machine to which an embodiment of the present invention is applied. FIG. 1 is an exploded perspective view of one embodiment of the present invention. The front view of a flange member. FIG. The front view of a ground plate. FIG. 4 is a characteristic diagram of the thickness of the ground plate and the press-fitting allowance.

Explanation of reference numerals

7 Photoreceptor drum 31 Drum tube 32 Flange member 33 Opening 37 Ground plate 38 Disc base material 39 Insertion hole 42 Claw member 43 Depression

Claims (6)

A drum tube having openings at both ends,
A flange member pressed into the opening of the drum tube,
A disc base having a mounting hole in the center and having a diameter smaller than the inner diameter of the drum base, a first claw member formed of an elastic member protruding from the outer periphery of the disc base, and the disc A bent portion formed by bending an outer peripheral side portion of the mounting hole of the base material inward on a side opposite to a mounting surface to the flange member, and having a tip portion reaching a position corresponding to the mounting hole. A conductive ground plate attached to the inner surface of the flange member such that the tip of the first claw member is located outside the inner diameter of the opening of the drum tube;
Drum unit with 2. The drum unit according to claim 1, wherein the ground plate has a recess formed on both sides of the first claw member as viewed in a plan view, the recess being recessed inward from the outer diameter of the disc base material. The flange member has a projection for attaching the ground plate on the inner surface side,
The ground plate has a mounting hole corresponding to the protrusion of the flange member, and the mounting hole is formed with a second claw member projecting in an inner circumferential direction.
The drum unit according to claim 1. In a drum unit including a drum base having openings at both ends and a flange member press-fitted into the opening of the drum base, a ground plate attached to the inner surface of the flange member and conducting to the drum base. So,
A disk substrate having a mounting hole in the center and having a diameter smaller than the inner diameter of the drum tube,
A first claw member formed of an elastic member protruding from an outer periphery of the disc base material;
A bent portion formed by bending an outer peripheral side portion of the mounting hole of the disc base material inward and on a side opposite to a mounting surface to the flange member, and a leading end portion reaches a position corresponding to the mounting hole. And having
Attached to the inner surface of the flange member such that the tip of the first claw member is located outside the inner diameter of the opening of the drum tube,
Ground plate used for drum unit. 5. The ground plate used in the drum unit according to claim 4, wherein recesses are formed on both sides of the first claw member in a plan view, the recesses being recessed inward from the outer diameter of the disk base material. The flange member has a projection for attaching the ground plate on the inner surface side,
It further has a mounting hole provided corresponding to the projection of the flange member,
A second claw member projecting in an inner circumferential direction is formed in the mounting hole;
An earth plate used for the drum unit according to claim 4.

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