JP2012189896A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which can keep a positional relationship of a plurality of photosensitive drums to a body casing constant while reducing the material cost and the weight.SOLUTION: In the color laser printer 1 which includes a body casing 2, a photosensitive drum 12 provided with a flange member 42, a drum unit 24 provided with a frame body 31 to which the flange member 42 is rotatably supported, an advancing/retracting member 50 which is provided on the body casing 2, can move to an advanced position and a retracted position, and is provided with a positioning shaft 55, the advancing/retracting member 50 is positioned at the advanced position in a state in which the drum unit 24 is mounted on the body casing 2, and thereby the flange member 42 of the photosensitive drum 12 supported to the frame body 31 and the positioning shaft 55 of the advancing/retracting member 50 are engaged with each other and the photosensitive drum 12 is positioned with respect to the body casing 2.

Description

  The present invention relates to an image forming apparatus employing an electrophotographic system.

  As an electrophotographic color printer, a tandem type color laser printer having a plurality of photoconductors arranged in parallel corresponding to toners of yellow, magenta, cyan, and black is known.

  For example, a color laser printer is known that includes a drum unit that integrally holds four photosensitive drums in a detachable manner with respect to a main body casing (see, for example, Patent Document 1). This drum unit includes a resin-made drum subunit that holds each photosensitive drum, and a pair of metal side plates that sandwich the drum subunit from both sides in the axial direction of the photosensitive drum.

  Each photosensitive drum is positioned in the main body casing by the side plate when the drum unit is mounted on the main body casing.

JP 2007-72422 A

  The side plate included in the color laser printer described in Patent Document 1 has accuracy and rigidity capable of keeping the relative positional relationship of each photosensitive drum constant. For this reason, such a side plate is expensive in terms of material cost and increases its weight, which makes it difficult to attach and detach the drum unit.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can keep the positional relationship of a plurality of photosensitive drums with respect to a main body casing constant while reducing material cost and weight.

  In order to achieve the above object, an image forming apparatus of the present invention includes an apparatus main body, a photosensitive drum provided with an element tube and supported members provided at both ends in the axial direction of the element tube, and the supported member is rotatable. And a support member attached to the apparatus main body so as to be capable of being pulled out, and provided in the apparatus main body, and disposed opposite to the photosensitive drum in the axial direction of the photosensitive drum, on the photosensitive drum side. A moving member that is movable to an advancing position that advances and a retreating position that is separated from the photosensitive drum, and the moving member includes the supported member on one end side in the axial direction of the photosensitive drum at the advanced position. A first positioning portion for engaging and positioning the photosensitive drum with respect to the apparatus main body is provided.

  In the image forming apparatus of the present invention, the moving member includes a first positioning portion for engaging the supported member at one end in the axial direction of the photosensitive drum at the advanced position and positioning the photosensitive drum with respect to the apparatus main body. ing.

  Therefore, the photosensitive drum attached to the support member is positioned with respect to the apparatus main body by the first positioning unit.

  As a result, the photosensitive drum can be positioned by the first positioning portion without positioning the photosensitive drum by the side plate. Therefore, the positional relationship (drum pitch) of the photosensitive drum with respect to the apparatus main body can be kept constant.

  Therefore, while the weight of the support member can be reduced and the material cost can be reduced, the positional relationship of the photosensitive drum with respect to the apparatus main body can be kept constant, and color misregistration can be prevented.

1 is a side sectional view showing a first embodiment of a color laser printer as an embodiment of an image forming apparatus of the present invention. It is the perspective view seen from the upper right side which shows the drum unit shown in FIG. It is the perspective view seen from the upper left side which shows the drum unit shown in FIG. It is a perspective view which shows the fitting member shown in FIG. FIG. 4 is a perspective view showing a fitting member and a left flange member shown in FIG. 3. FIG. 4 is a plan sectional view for explaining a retracted position of the advance / retreat member in the drum unit shown in FIGS. 2 and 3. FIG. 4 is a cross-sectional plan view for explaining an advanced position of the advance / retreat member in the drum unit shown in FIGS. 2 and 3. It is a side view which shows the mounting state with respect to the apparatus main body of the drum unit shown in FIG. It is a side view which shows the mounting state with respect to the apparatus main body of the drum unit in 2nd Embodiment of this invention. It is a side view which shows the mounting state with respect to the apparatus main body of the drum unit in the other form (The aspect with which one drum exposure hole is provided with a horizontal straight part and a vertical straight part) of 2nd Embodiment of this invention. It is sectional drawing for demonstrating the retraction | saving position of the advance / retreat member in 3rd Embodiment of this invention. It is sectional drawing for demonstrating the advance position of the advance / retreat member in 3rd Embodiment of this invention.

1. Overall Configuration of Color Laser Printer As shown in FIG. 1, a color laser printer 1 as an example of an image forming apparatus is a horizontal type direct tandem type color laser printer. The color laser printer 1 includes a paper feeding unit 3 for feeding paper P and an image forming unit 4 for forming an image on the fed paper P in a main body casing 2 as an example of an apparatus main body. It has.
(1) Main Body Casing The main body casing 2 is formed in a box shape having a substantially rectangular shape in side view that accommodates the paper feeding unit 3 and the image forming unit 4, and an inner space of the main body casing 2 is opened on one side wall thereof. A front cover 5 is formed. The front cover 5 is swingably provided with respect to the main body casing 2 with the lower end portion as a fulcrum.

In the following description, the side on which the front cover 5 is provided (the left side in FIG. 1) is the front side, and the opposite side (the right side in FIG. 1) is the rear side. In addition, when the color laser printer 1 is viewed from the front side, the left and right reference is used. That is, the front side in FIG. 1 is the right side and the back side is the left side.
(2) Paper Feed Unit The paper feed unit 3 includes a paper feed tray 6 that accommodates the paper P at the bottom in the main body casing 2.

The sheets P stored in the sheet feed tray 6 are fed one by one toward the pair of registration rollers 7 arranged on the upper side of the front end of the sheet feed tray 6, and at a predetermined timing, the image forming unit 4 (between a photosensitive drum 12 (described later) and a conveyor belt 18 (described later)).
(3) Image Forming Unit The image forming unit 4 includes a scanner unit 8, a process unit 9, a transfer unit 10, and a fixing unit 11.
(3-1) Scanner Unit The scanner unit 8 is disposed in the upper part of the main body casing 2. As indicated by solid lines, the scanner unit 8 emits laser beams toward four photosensitive drums 12 (described later) based on the image data to expose the photosensitive drums 12 (described later).
(3-2) Process Unit (3-2-1) Configuration of Process Unit The process unit 9 is disposed below the scanner unit 8 and above the transfer unit 10, and includes the drum unit 24 and the developing unit 14. It has.

  The drum unit 24 includes a photosensitive drum 12 and a scorotron charger 13.

  The photosensitive drums 12 are formed in a substantially cylindrical shape extending in the left-right direction, are provided along the left-right direction, and are arranged in parallel at four intervals in the front-rear direction. Each photosensitive drum 12 corresponds to black, yellow, magenta, and cyan, respectively.

  The scorotron charger 13 is disposed on the rear upper side of the photosensitive drum 12 so as to correspond to the photosensitive drums 12 so as to face the photosensitive drums 12 with an interval.

  The developing unit 14 is disposed above the photosensitive drum 12 so as to correspond to each photosensitive drum 12. Each developing unit 14 includes a developing roller 15.

  The developing roller 15 is rotatably supported at the lower end of the developing unit 14 so as to be exposed from the rear side, and is opposed to and contacts the photosensitive drum 12 from the front upper side.

The developing unit 14 contains toner corresponding to each color in the space above the developing roller 15.
(3-2-2) Developing Operation in Process Unit The toner in the developing unit 14 is carried on the surface of the developing roller 15 as the developing roller 15 rotates.

  On the other hand, the surface of the photosensitive drum 12 is uniformly charged by the scorotron charger 13 as the photosensitive drum 12 rotates, and then is scanned at high speed by a laser beam (see the broken line in FIG. 1) from the scanner unit 8. Exposed. As a result, an electrostatic latent image corresponding to the image to be formed on the paper P is formed on the surface of the photosensitive drum 12.

When the photosensitive drum 12 further rotates, the toner carried on the surface of the developing roller 15 is supplied to the electrostatic latent image formed on the surface of the photosensitive drum 12. As a result, the electrostatic latent image on the photosensitive drum 12 is visualized, and a toner image by reversal development is carried on the surface of the photosensitive drum 12.
(3-3) Transfer Unit The transfer unit 10 is arranged along the front-rear direction in the main body casing 2 above the paper feed unit 3 and below the process unit 9. The transfer unit 10 includes a driving roller 16 and a driven roller 17, a conveyance belt 18, and four transfer rollers 19.

  The driving roller 16 and the driven roller 17 are arranged to face each other with a space in the front-rear direction.

  The conveyor belt 18 is opposed to each photosensitive drum 12 from the lower side, and is stretched around the driving roller 16 and the driven roller 17 so that the upper portion thereof is in contact with each photosensitive drum 12. Further, the transport belt 18 is rotated by the drive roller 16 so that the upper part of the transport belt 18 that contacts each photosensitive drum 12 moves from the front side toward the rear side.

  Each transfer roller 19 is provided to face each photosensitive drum 12 with the upper portion of the transport belt 18 interposed therebetween.

Then, the paper P fed from the paper feeding unit 3 is transported by the transport belt 18 from the front side to the rear side so as to sequentially pass through the transfer positions where the photosensitive drums 12 and the transfer rollers 19 face each other. Is done. During the conveyance, the color toner images carried on the respective photosensitive drums 12 are sequentially transferred onto the paper P to form a color image.
(3-4) Fixing Unit The fixing unit 11 includes a heating roller 20 and a pressure roller 21 that is in pressure contact with the heating roller 20.

The color image transferred to the paper P in the transfer unit 10 is thermally fixed to the paper P by being heated and pressed when the paper P passes between the heating roller 20 and the pressure roller 21.
(4) Paper Discharge The paper P on which the toner image is fixed is conveyed by each paper discharge roller 22 so as to pass through the U-turn path, and is discharged onto a paper discharge tray 23 formed on the upper side of the scanner unit 8. .
2. Details of Drum Unit As shown in FIGS. 2 and 3, the drum unit 24 includes a frame 31 as an example of a support member, four photosensitive drums 12, and four drum subunits 30.

The drum unit 24 is mounted so that it can be pulled out in the front-rear direction with respect to the inside of the main casing 2 (see FIG. 1).
(1) Frame The frame 31 is made of resin and includes a pair of side plates 33, a front beam 34, and a rear beam 35.

  Both side plates 33 are formed in a substantially rectangular shape in a side view extending in the front-rear direction, and a notch 38 is formed in a rear end edge thereof, which is cut out in a substantially V shape in a side view toward the front side. The notch 38 is opened toward the rear side, and receives a main body reference shaft 104 (described later) in a state where the drum unit 24 is attached to the main body casing 2 as shown in FIGS. 1 and 8. The main body reference shaft 104 comes into contact with the upper and lower front sides.

  Further, as shown in FIGS. 6 and 7, the both side plates 33 are each integrally provided with four bearing portions 40.

  The bearing portion 40 is formed in a substantially cylindrical shape, one end face is joined to the inner face of the side plate 33, and the other end face is opened. And four are arrange | positioned at equal intervals in the front-back direction.

  Further, the inner diameter of the bearing portion 40 is slightly larger than the outer diameter of the bearing fitting portion 44 (described later).

  Further, as shown in FIG. 2, a shaft insertion hole 37 is formed in the right side plate 33 (hereinafter referred to as the right side plate 33R).

  Specifically, the shaft insertion hole 37 is formed in a substantially circular shape when viewed from the side, and the axis of the bearing portion 40 (hereinafter referred to as the right bearing portion 40R) provided in the right side plate 33R and the center of the shaft insertion hole 37 are left and right. It communicates with the internal space of the right bearing 40R so as to match in the direction.

  Further, the shaft insertion hole 37 has a smaller diameter than the right bearing portion 40R and a larger diameter than a positioning hole 51 (described later) and a sword portion 52 (described later) of the photosensitive drum 12 (see FIG. 5).

  Further, as shown in FIG. 3, a drum exposure hole 39 as an example of a through hole is formed in the left side plate 33 (hereinafter referred to as the left side plate 33L).

  Specifically, the drum exposure hole 39 is formed in a substantially circular shape when viewed from the side, and the axis of the bearing portion 40 (hereinafter referred to as the left bearing portion 40L) included in the left side plate 33L and the center of the drum exposure hole 39 are left and right. It communicates with the internal space of the left bearing portion 40L so as to match in the direction.

  Further, the drum exposure hole 39 has substantially the same diameter as the inner diameter of the left bearing portion 40L, and is slightly larger than the outer diameter of the bearing fitting portion 44 (described later).

  The right side plate 33R and the left side plate 33L are opposed to each other with the bearing portions 40, and when projected in the left-right direction, the center of each shaft insertion hole 37 of the right side plate 33R and each drum of the left side plate 33L. The exposure holes 39 are opposed to each other so that the centers of the exposure holes 39 coincide with each other.

  The front beam 34 is installed between the front end portions of the side plates 33.

  Further, the front beam 34 holds the support shaft 29.

  The support shaft 29 penetrates the front beam 34 in the left-right direction, further penetrates the right side plate 33R and the left side plate 33L, and protrudes outward in the left-right direction from the right side plate 33R and the left side plate 33L. As shown in FIG. 8, the lower end and the upper front side of the support shaft 29 are sandwiched by the sandwiching portion 105 (described later) with the drum unit 24 attached to the main casing 2, as shown in FIG. 8. Is done.

The rear beam 35 is installed between the rear ends of the side plates 33.
(2) Photosensitive drum As shown in FIGS. 6 and 7, the photosensitive drum 12 includes a raw tube 41 and a pair of flange members 42 as an example of a supported member.

  The raw tube 41 is made of metal and has a substantially cylindrical shape extending in the left-right direction. The outer peripheral surface of the base tube 41 is covered with a photosensitive layer.

  Both flange members 42 are made of resin, and a drum fitting portion 43 that is inserted into the raw tube 41 so as not to be relatively rotatable, and a bearing fitting portion 44 that is rotatably supported by the bearing portions 40 of the side plates 33. Is integrated.

  Specifically, the drum fitting portion 43 of the flange member 42 is formed in a substantially cylindrical shape having substantially the same diameter as the inner diameter of the raw tube 41.

  The bearing fitting portion 44 of the flange member 42 is formed in a substantially cylindrical shape having a smaller diameter than the outer diameter of the drum fitting portion 43, and the drum fitting portion 43 has its center axis shared with the drum fitting portion 43. It is formed so as to protrude in a convex section in the axial direction.

  Further, the end surface of the bearing fitting portion 44 opposite to the drum fitting portion 43 is sealed with a sealing portion 48 as shown in FIG.

  A positioning hole 51 and a sword portion 52 are formed in the sealing portion 48.

  The positioning hole 51 is formed in a substantially circular shape when viewed from the side, and is formed such that the axis of the bearing fitting portion 44 and the center of the positioning hole 51 coincide in the left-right direction, and the inner diameter thereof is that of a positioning shaft 55 (described later). The outer diameter is substantially the same.

  The sword portion 52 is formed by chamfering the peripheral edge of the positioning hole 51 in the sealing portion 48, and gradually widens from the peripheral edge of the positioning hole 51 toward the outside in the axial direction of the bearing fitting portion 44. It is formed to become.

  Then, as shown in FIGS. 6 and 7, both the flange member 42 and the raw pipe 41 are respectively press-fitted into the left and right ends of the raw pipe 41 by the drum fitting portions 43 of the both flange members 42. Fitted so that relative rotation is impossible.

  That is, the bearing fitting portion 44 of the right flange member 42 (hereinafter, referred to as the right flange member 42R) is formed so as to protrude from the drum fitting portion 43 to the right side in a convex section.

  Further, the bearing fitting portion 44 of the left flange member 42 (hereinafter referred to as the left flange member 42L) is formed so as to protrude from the drum fitting portion 43 to the left side in a convex section.

Further, as shown in FIGS. 4 and 5, a fitting protrusion 62 (described later) of a coupling male member 60 (described later) of the advance / retreat member 50 (described later) is fitted to the left end surface of the left flange member 42L. Four coupling fitting holes 61 are formed. The four coupling fitting holes 61 are formed in a substantially U shape in a side view, and are formed so as to be displaced by about 90 ° from each other at equal intervals in the circumferential direction at the peripheral end portion of the bearing fitting portion 44. ing.
(3) Drum Sub Unit As shown in FIGS. 2 and 3, the drum subunit 30 is disposed between the side plates 33 and between the front beam 34 and the rear beam 35 on the rear side of each photosensitive drum 12. Thus, four are arranged in parallel at equal intervals in the front-rear direction.

Each drum subunit 30 is formed in a substantially triangular prism shape extending left and right. Each drum subunit 30 holds a scorotron charger 13 along the left-right direction.
(4) Assembly of drum unit Next, the assembly of the drum unit 24 will be described.

  In order to assemble the drum unit 24, first, the four drum subunits 30, the front beam 34 and the rear beam 35 are disposed between the side plates 33.

  Each drum subunit 30 is disposed between the side plates 33 at a predetermined position.

  Next, the front beam 34 is disposed between the side plates 33, and the rear beam 35 is disposed between the side plates 33.

  Next, the four photosensitive drums 12 are assembled to the right side plate 33R.

  In order to assemble each photosensitive drum 12 to the right side plate 33R, a bearing fitting portion 44 (hereinafter, referred to as a right bearing fitting portion 44R) of the right flange member 42R is disposed on the left side of the right bearing portion 40R. Then, the photosensitive drum 12 is positioned on the left side of the right side plate 33R, and the photosensitive drum 12 is attached to the right side plate 33R from the left side so that the right bearing fitting portion 44R is inserted into the internal space of the right bearing portion 40R.

  Then, the sealing portion 48 of the right flange member 42R is adjacent to the shaft insertion hole 37 formed in the right end surface of the right bearing portion 40R in the left-right direction. At this time, the positioning hole 51 and the sword portion 52 formed in the sealing portion 48 of the right flange member 42 </ b> R are exposed from the shaft insertion hole 37.

  Accordingly, the right end portion of each photosensitive drum 12 is supported by the right side plate 33R so as to be relatively rotatable by the right flange member 42R being supported by the right bearing portion 40R so as to be relatively rotatable.

  Next, each photosensitive drum 12 is assembled to the left side plate 33L.

  In order to assemble each photosensitive drum 12 to the left side plate 33L, a bearing fitting portion 44 of the left flange member 42L (hereinafter, referred to as a left bearing fitting portion 44L) is disposed on the right side of the left bearing portion 40L. The photosensitive drum 12 is positioned on the right side of the left side plate 33L, and the photosensitive drum 12 is attached to the left side plate 33L from the right side so that the left bearing fitting portion 44L is inserted into the inner space of the left bearing portion 40L.

  Then, as shown in FIG. 8, the sealing portion 48 of the left flange member 42L is adjacent to the drum exposure hole 39 formed in the left end surface of the left bearing portion 40L in the left-right direction. At this time, since the sealing portion 48 of the left flange member 42 </ b> L is exposed from the drum exposure hole 39, the positioning hole 51 and the pitching portion 52 formed in the sealing portion 48 are also exposed from the drum exposure hole 39.

  Accordingly, the left end portion of the photosensitive drum 12 is supported by the left plate 33L so as to be relatively rotatable by the left flange member 42L being supported by the left bearing portion 40L so as to be relatively rotatable.

  As described above, as shown in FIGS. 6 and 7, the photosensitive drums 12 are supported between the side plates 33.

  At this time, since the outer diameter of the right bearing fitting portion 44R of the right flange member 42R is slightly smaller than the inner diameter of the right bearing portion 40R, the right bearing fitting portion 44R is free from the right bearing portion 40R. It is fitted.

  Further, since the outer diameter of the left bearing fitting portion 44L of the left flange member 42L is slightly smaller than the diameters of the left bearing portion 40L and the drum exposure hole 39, the left bearing fitting portion 44L has the left bearing portion 40L. And it is loosely fitted with respect to the drum exposure hole 39 (refer FIG. 8).

  Specifically, the two flange members 42 are arranged in the front-rear direction (the mounting direction and the drawing direction of the drum unit 24) as an example of the first direction, and the vertical direction (the first direction and the axis of the photosensitive drum 12) as an example of the second direction. It is loosely fitted so as to be movable in a direction perpendicular to both directions.

  Then, the drum subunit 30, the front beam 34, and the rear beam 35 are screwed so as to sandwich the both side plates 33.

Thereby, the assembly of the drum unit 24 is completed.
3. Details of Main Body Casing As shown in FIGS. 1 and 6 to 8, the main body casing 2 includes a main body reference shaft 104 and a sandwiching portion 105 as an example of a positioning member, an advance / retreat member 50 as an example of a moving member, and a fixing member. As an example, a fixed plate 101 is provided.
(1) Main Body Reference Axis and Holding Portion As shown in FIGS. 1 and 8, the main body reference shaft 104 is installed on the rear side in the main body casing 2 in the left-right direction.

  The main body reference shaft 104 has a notch 38 formed on both side plates 33 of the drum unit 24 and the upper and lower front sides of the main body reference shaft 104 when the drum unit 24 is attached to the main body casing 2. Abut.

  As shown in FIG. 8, two sandwiching portions 105 are provided on the left and right sides of the front side in the main body casing 2, and each includes a pressing portion 106 and a regulating wall 107.

  The pressing portion 106 is formed in a substantially trapezoidal flat plate shape in a side view that is cut obliquely from the corner of the front lower end in a rectangular shape in a side view toward the upper rear side, and the cut out portion forms an inclined surface 108. Yes.

  The pressing portion 106 is urged downward by an urging member (not shown).

  The restriction wall 107 is disposed below the pressing portion 106 with a space therebetween and is formed to extend along the front-rear direction.

  And the regulation wall 107 and the press part 106 are arrange | positioned so that the upper surface of the regulation wall 107 and the inclined surface 108 of the press part 106 may oppose in an up-down direction.

As a result, in the state where the drum unit 24 is mounted on the main body casing 2, the clamping unit 105 connects the both ends of the support shaft 29 supported by the front beam 34 of the drum unit 24 to the upper surface of the regulating wall 107 and the pressing unit 106. It is clamped between the inclined surfaces 108.
(2) Advance / Retreat Member The advance / retreat member 50 includes a left drum positioning member 53 and a right drum positioning member 54.
(2-1) Left Drum Positioning Member The left drum positioning member 53 is arranged so that the left drum positioning member 53 faces the four left bearing fitting portions 44L from the left in a state where the drum unit 24 is mounted on the main casing 2. On the left side, four are provided at intervals in the front-rear direction.

The left drum positioning member 53 includes a reference member 71, a driving member 66, an air-core coiled spring member 56, a fitting member 59, and a positioning shaft 55 as an example of a first positioning portion.
(2-1-1) Reference Member In the reference member 71, a proximal end shaft 72, a midway shaft 73, and a distal end shaft 74 are integrally formed.

  The proximal shaft 72, the intermediate shaft 73, and the distal shaft 74 each have a substantially cylindrical shape.

  The intermediate shaft 73 has a length in the axial direction that is substantially the same as a length in the thickness direction of a gear portion 67 (described later), and has an outer diameter smaller than the outer diameter of the base end shaft 72.

  The outer diameter of the tip shaft 74 is smaller than the outer diameter of the intermediate shaft 73.

  The base end shaft 72 and the intermediate shaft 73 are formed so as to protrude from the base end shaft 72 in a convex shape in the axial direction so as to share the central axis. The intermediate shaft 73 and the tip shaft 74 are formed so as to protrude from the intermediate shaft 73 in a convex shape in the axial direction so as to share the central axis.

That is, the proximal end shaft 72, the intermediate shaft 73, and the distal end shaft 74 are formed so as to share the central axis.
(2-1-2) Drive Member The drive member 66 is formed integrally with an outer cylinder portion 68 and a gear portion 67 as an example of a drive rotator.

  The outer cylinder portion 68 is formed in a substantially cylindrical shape, and the inner diameter thereof is substantially the same as the outer diameter of the intermediate shaft 73, and the outer diameter thereof is substantially the same as the outer diameter of the proximal end shaft 72.

  Further, the axial length of the outer cylinder portion 68 is formed slightly longer than the sum of the axial lengths of the tip shaft 74 and the intermediate shaft 73.

  Further, the outer cylinder portion 68 is formed with two slits (not shown) that engage with two protrusions 64 (described later) provided in the inner cylinder portion 63 (described later) over the entire axial direction.

The gear portion 67 is formed in an annular plate shape that extends radially outward from the outer peripheral surface of the outer end portion in the axial direction of the outer cylinder portion 68. That is, the gear part 67 and the outer cylinder part 68 are formed so that the rotation axis of the gear part 67 and the axis of the outer cylinder part 68 coincide. Engaging teeth (not shown) for receiving a driving force transmitted from a driving source (not shown) such as a motor provided in the main body casing 2 are formed on the peripheral end surface of the gear portion 67.
(2-1-3) Fitting Member and Positioning Shaft As shown in FIG. 4 and FIG. 5, the fitting member 59 is formed integrally with an inner cylindrical portion 63 and a coupling male member 60.

  The inner cylinder part 63 is formed in a substantially cylindrical shape, and the inner diameter thereof is substantially the same as the outer diameter of the tip shaft 74, and the outer diameter thereof is substantially the same as the outer diameter of the intermediate shaft 73.

  In addition, two protrusions 64 are provided on the outer peripheral surface of the inner cylindrical portion 63.

  The two ridges 64 are formed to have a substantially rectangular cross section, and are formed so as to face the radial direction over the entire axial direction of the inner cylindrical portion 63.

  The coupling male member 60 is provided in a cylindrical portion 77 formed in a substantially cylindrical shape, a fitting wall 80 that seals the inner end surface in the axial direction of the cylindrical portion 77, and a central portion of the fitting wall 80. A shaft holding portion 83 (see FIGS. 6 and 7) formed in the inner space of the cylindrical portion 77 so as to be concentric with the cylindrical portion 77, and on the outer peripheral surface of the cylindrical portion 77, the cylindrical portion An annular plate-shaped flange portion 78 that extends radially outward from the middle portion of the axial direction of 77 is integrally provided.

  The cylindrical portion 77 has an inner diameter that is larger than the outer diameter of the outer cylindrical portion 68.

  Two fitting protrusions 62 and a shaft through hole 82 are formed on the fitting wall 80.

  The two fitting protrusions 62 are provided so as to face each other in the radial direction at the peripheral end portion of the right side surface of the fitting wall 80. Each fitting protrusion 62 is formed so as to protrude rightward from the right side surface of the fitting wall 80. The tip of the fitting protrusion 62 is formed in a substantially arc shape.

  The shaft through hole 82 is provided in the central portion of the fitting wall 80 so as to penetrate in the thickness direction of the fitting wall 80 and communicate with the internal space of the shaft holding portion 83.

  The flange portion 78 has an extension 79 that is larger in diameter than the outer diameter of the spring member 56 and extends to the left from the peripheral edge.

  The coupling male member 60 is provided with a rod-like positioning shaft 55 so as not to be relatively rotatable along the central axis of the shaft holding portion 83 (tubular portion 77). One end portion of the positioning shaft 55 is inserted into the shaft holding portion 83 and held by the coupling male member 60. Further, the other end portion of the positioning shaft 55 protrudes from the fitting wall 80, and the tip thereof is formed in a tapered shape.

And the inner cylinder part 63 and the coupling male member 60 are couple | bonded so that the shaft holding part 83 and the inner cylinder part 63 of the coupling male member 60 may share a central axis. That is, the inner cylinder part 63 and the positioning shaft 55 are formed so as to share the central axis.
(2-1-4) Assembly of left positioning member Next, the assembly of the left drum positioning member 53 will be described.

  To assemble the left drum positioning member 53, first, the drive member 66 is attached to the reference member 71. Specifically, the tip shaft 74 of the reference member 71 is inserted into the inner space of the outer cylinder portion 68 from the end surface on the gear portion 67 side of the outer cylinder portion 68. Then, the reference member 71 is advanced until the end of the outer cylinder portion 68 on the side of the gear portion 67 contacts the base end shaft 72.

  As a result, the outer cylindrical portion 68 of the drive member 66 is fitted onto the distal end shaft 74 and the intermediate shaft 73 of the reference member 71, and the drive member 66 is attached to the reference member 71 so as to be relatively rotatable. At this time, since the inner diameter of the outer cylinder part 68 and the outer diameter of the intermediate shaft 73 are substantially the same diameter, the radial shaking of the outer cylinder part 68 is restricted. Further, since the outer diameter of the tip shaft 74 is smaller than the inner diameter of the outer cylinder portion 68, a space is formed between the outer peripheral surface of the tip shaft 74 and the inner peripheral surface of the outer cylinder portion 68.

  Next, after the spring member 56 is inserted into the outer side of the outer cylindrical portion 68 of the drive member 66, the fitting member 59 is mounted. Specifically, two protrusions 64 formed on the outer peripheral surface of the inner cylindrical portion 63 of the fitting member 59 and two slits (not shown) formed in the outer cylindrical portion 68 of the driving member 66 are provided. The fitting members 59 are positioned so as to face each other in the axial direction of the cylindrical portion 63. Then, the inner cylindrical portion 63 of the fitting member 59 is connected to the outer peripheral surface of the tip shaft 74 and the inner peripheral surface of the outer cylindrical portion 68 so that the protrusion 64 and the slit (not shown) are slidably engaged. Insert into the space formed between.

  As a result, the inner cylindrical portion 63 of the fitting member 59 is externally fitted to the outer cylindrical portion 68 of the driving member 66, and the fitting member 59 is attached to the reference member 71, the driving member 66 and the spring member 56. At this time, since the inner diameter of the inner cylinder portion 63 and the outer diameter of the distal end shaft 74 are substantially the same diameter, the radial play of the inner cylinder portion 63 is restricted. Further, since the slit (not shown) of the outer cylindrical portion 68 and the protrusion 64 of the inner cylindrical portion 63 are engaged, the drive member 66 and the fitting member 59 are slidable along the axial direction, and , Engaged so as not to rotate relative to each other. The spring member 56 is sandwiched between the outer cylinder portion 68 side of the gear portion 67 and the inner cylinder portion 63 side of the flange portion 78, and is covered and fixed by an extension portion 79 formed in the flange portion 78.

  Thus, the left drum positioning member 53 is assembled.

In the left drum positioning member 53, since the rattling of the outer cylinder portion 68 and the inner cylinder portion 63 is restricted, the axis of the positioning shaft 55 held by the fitting member 59, the reference member 71, and the outer cylinder portion 68 and the axis of the inner cylinder part 63 are formed to coincide with each other.
(2-2) Right Drum Positioning Member The right drum positioning member 54 is configured so that the right drum positioning member 54 faces the four right bearing fitting portions 44R from the right side when the drum unit 24 is attached to the main body casing 2. On the right side, four are provided at intervals in the front-rear direction.

As shown in FIGS. 6 and 7, the right drum positioning member 54 includes a reference member 91, an air-core coiled spring member 95, a shaft holding member 90, and a positioning shaft 98 as an example of a second positioning portion. Yes.
(2-2-1) Reference Member In the reference member 91, a base end shaft 92 and a front end shaft 93 are integrally formed.

  The proximal end shaft 92 is formed in a substantially cylindrical shape.

  The distal shaft 93 is formed in a substantially cylindrical shape, and the outer diameter thereof is smaller than the outer diameter of the proximal shaft 92.

The proximal shaft 92 and the distal shaft 93 are formed so as to protrude from the proximal shaft 92 in a convex shape in the axial direction so as to share the central axis.
(2-2-2) Shaft Holding Member The shaft holding member 90 is integrally provided with a cylindrical member 96, a flange portion 97, and a shaft holding portion 100.

  The cylindrical member 96 has an inner diameter that is substantially the same as the outer diameter of the distal end shaft 93, and an outer diameter that is substantially the same as the outer diameter of the proximal end shaft 92.

  The flange portion 97 is formed in a substantially annular plate shape, and is formed so as to spread outward in the radial direction from one circumferential end portion of the cylindrical member 96. The flange 97 has an extension 99 that has a diameter larger than the outer diameter of the spring member 95 and extends to the right from the peripheral edge.

  The shaft holding portion 100 is formed in a substantially cylindrical shape concentric with the cylindrical member 96, and an inner peripheral surface on one end side (the flange 97 side) of the cylindrical member 96 and an outer peripheral surface on one end side of the shaft holding portion 100 are shafts. The holding unit 100 is coupled over the entire circumferential direction.

  Further, the shaft holding portion 100 is formed so that its inner diameter is substantially the same as the outer diameter of a positioning shaft 98 (described later).

A shaft-like positioning shaft 98 is provided on the shaft holding member 90 so as not to rotate relatively along the central axis of the shaft holding portion 100 (cylindrical member 96). One end portion of the positioning shaft 98 is inserted and held in the shaft holding portion 100. Further, the other end portion of the positioning shaft 98 has a tapered tip.
(2-2-3) Assembly of Right Positioning Member Next, assembly of the right drum positioning member 54 will be described.

  To assemble the right drum positioning member 54, first, the shaft holding member 90 is attached to the reference member 71. Specifically, the tip shaft 93 of the reference member 91 is inserted into the internal space of the cylindrical member 96 from the free end side of the cylindrical member 96. Then, the reference member 91 is advanced until the free end portion of the cylindrical member 96 comes into contact with the proximal end shaft 92.

  As a result, the cylindrical member 96 of the shaft holding member 90 is fitted on the distal end shaft 93 of the reference member 91, and the shaft holding member 90 is attached to the reference member 91. At this time, since the inner diameter of the cylindrical member 96 and the outer diameter of the tip shaft 93 are substantially the same diameter, the radial shaking of the cylindrical member 96 is restricted.

  Next, the spring member 95 is inserted into the outer peripheral surface of the base end shaft 92 of the reference member 91 and the cylindrical member 96 of the shaft holding member 90.

  Thus, the spring member 95 is mounted on the reference member 71 and the shaft holding member 90, and the right drum positioning member 54 is assembled.

In the right drum positioning member 54, since the rattling of the cylindrical member 96 is restricted, the axis of the positioning shaft 98 held by the shaft holding member 90 and the axes of the reference member 91 and the cylindrical member 96 are matched. Is formed.
(3) Positioning of Advance / Retreat Member with respect to Main Body Casing The fixed plates 101 are formed in a substantially flat plate shape and are provided as a pair so as to face each other with a gap in the left-right direction. Each fixing plate 101 is fixed to a frame (not shown) of the main casing 2.

  Each advance / retreat member 50 is fixed to the fixing plate 101 by the screw member 102 and positioned with respect to the main body casing 2.

  Specifically, as shown in FIG. 7, each left drum positioning member 53 corresponds to a state where the drum unit 24 is mounted on the main casing 2 and each left drum positioning member 53 is in an advanced position (described later). The positioning shaft 55 held by each left drum positioning member 53 is arranged so as to enter the positioning hole 51 of the photosensitive drum 12 from the left side. Then, the free end surface of the base end shaft 72 of the reference member 71 of each left drum positioning member 53 and the fixing plate 101 are screwed by the screw member 102.

  Thus, the four left drum positioning members 53 are positioned with respect to the main casing 2. The four left drum positioning members 53 are fixed to one fixed plate 101 at equal intervals in the front-rear direction.

  Each right drum positioning member 54 is positioned in the corresponding positioning hole 51 of the photosensitive drum 12 when the drum unit 24 is mounted on the main casing 2 and each right drum positioning member 54 is in the advanced position (described later). The positioning shaft 98 held by each right drum positioning member 54 is arranged so as to enter from the right side. Then, the free end surface of the base end shaft 92 of the reference member 91 of each right drum positioning member 54 and the fixing plate 101 are screwed by the screw member 102. At this time, the spring member 95 is sandwiched between the fixing plate 101 and the cylindrical member 96 side of the flange 97, and is covered and fixed by the extension 99 formed on the flange 97.

  Thus, the four right drum positioning members 54 are positioned with respect to the main casing 2. The four right drum positioning members 54 are fixed to one fixed plate 101 at equal intervals in the front-rear direction.

Each left drum positioning member 53 and each right drum positioning member 54 are arranged to face each other with an interval in the left-right direction so as to share a central axis.
(4) Mounting of Drum Unit to Main Body Casing As shown in FIG. 8, in order to mount the drum unit 24 to the main body casing 2, first, the front cover 5 of the main body casing 2 is opened (see FIG. 1). Then, the drum unit 24 is guided to the main casing 2 by moving the drum unit 24 rearward. When the cutout portions 38 of the right side plate 33R and the left side plate 33L are in contact with the upper side and the front lower side of the main body reference shaft 104, further pressing of the drum unit 24 is restricted. At this time, the left and right end portions of the support shaft 29 supported by the front beam 34 are respectively positioned between the inclined surface 108 of the pressing portion 106 of the clamping portion 105 and the upper surface of the regulating wall 107, and are pressed by the pressing portion 106. The lower side and the front side upper side are sandwiched. Thereby, the movement of the drum unit 24 in the front-rear direction and the up-down direction is restricted, and the drum unit 24 is positioned with respect to the main casing 2.

  Thus, the mounting of the drum unit 24 on the main casing 2 is completed.

When the drum unit 24 is pulled out from the main casing 2, the inclined surface 108 of the pressing portion 106 moves away from the regulation wall 107 by moving both ends of the support shaft 29 forward as the drum unit 24 is moved forward. Pressing in the direction of separating, the pressing portion 106 moves upward, and the clamping of both ends of the support shaft 29 of the clamping portion 105 is released. And it can pull out by the reverse procedure of said procedure.
(5) Positioning of Photosensitive Drum with respect to Main Body Casing As shown in FIGS. 6 and 7, the four advancing / retracting members 50 are moved to a retracted position and an advanced position by a known interlocking mechanism as the front cover 5 is opened and closed.

  Specifically, when the front cover 5 is opened, each advance / retreat member 50 moves from the advanced position to the retracted position, and when the front cover 5 is closed, each advance / retreat member 50 moves from the retracted position to the advanced position. Moving.

  In the retracted position, as shown in FIG. 6, when the drum unit 24 is mounted on the main casing 2, the flange members 42 of the photosensitive drum 12 and the advance / retreat members 50 are separated from each other in the left-right direction. .

  Specifically, on the left side in the main casing 2, the shaft insertion hole 37 formed in each left flange member 42 </ b> L of the photosensitive drum 12 and the tip of the positioning shaft 55 held by each left drum positioning member 53 are in the left-right direction. Are opposed to each other with an interval.

  Further, on the right side in the main casing 2, the shaft insertion holes 37 formed in the respective right flange members 42 </ b> R of the photosensitive drum 12 and the tip end portions of the positioning shafts 98 held by the respective right drum positioning members 54 extend in the left-right direction. Opposing to each other with an interval.

  At the advanced position, as shown in FIG. 7, in the state where the drum unit 24 is mounted on the main body casing 2, each advance / retreat member 50 has advanced from the retracted position to each flange member 42 side of the photosensitive drum 12. .

  Specifically, in each left drum positioning member 53, the fitting member 59 of each left drum positioning member 53 is urged by the urging force of the spring member 56 and advances to the right. At this time, first, the distal end portion of the positioning shaft 55 held by the fitting member 59 comes into contact with the sword portion 52 formed in the sealing portion 48 of the left flange member 42L and enters the internal space of the positioning hole 51. The positioning shaft 55 enters the positioning hole 51 by being guided. Further, as the positioning hole 51 of the positioning shaft 55 enters, the fitting member 59 advances to the right, and the fitting protrusion 62 formed on the fitting wall 80 of the coupling male member 60 of the fitting member 59. To the coupling fitting hole 61 formed in the sealing portion 48 of the left flange member 42L. Thereby, the left flange member 42L and the fitting member 59 are fitted so as not to be relatively rotatable.

  On the other hand, in each right drum positioning member 54, the shaft holding member 90 of each right drum positioning member 54 is urged by the urging force of the spring member 95 and advances to the left. At this time, the distal end portion of the positioning shaft 98 held by the shaft holding portion 100 comes into contact with the sword portion 52 formed in the sealing portion 48 of the right flange member 42 </ b> R, so that the positioning shaft 98 is inside the positioning hole 51. Guided by the space, the positioning shaft 98 enters the positioning hole 51.

  In addition, after the fitting protrusion 62 of the fitting member 59 of each left drum positioning member 53 is coupled to the coupling fitting hole 61 of each left flange member 42L, each left drum positioning member 53 is further moved to the right. Advance. Thereby, the drum unit 24 is moved rightward as a whole via each left flange member 42L. Thereby, the positioning of the drum unit 24 in the left-right direction is achieved. That is, the left and right positioning of each photosensitive drum 12 with respect to the main casing 2 is achieved.

  As described above, the four photosensitive drums 12 are positioned in the front-rear direction and the vertical direction with respect to the main body casing 2 by the four left drum positioning members 53, the four right drum positioning members 54, and the two fixing plates 101. .

Therefore, when the front cover 5 is opened, the respective advancing and retracting members 50 are located at the retracted position, and the drum unit 24 can be mounted on the main body casing 2. The drum unit 24 is attached to the main body casing 2 by the main body reference shaft 104 and the sandwiching portion 105. Is positioned. When the front cover 5 is closed, each advance / retreat member 50 is positioned at the advanced position, and each photosensitive drum 12 supported by the drum unit 24 is positioned with respect to the main body casing 2.
(6) Input of driving force to photosensitive drum When the positioning of each photosensitive drum 12 with respect to the main casing 2 is achieved, the driving force transmitted from a driving source (not shown) such as a motor of the main casing 2 is changed to each driving. It is transmitted to each drive member 66 via engagement teeth (not shown) formed on the peripheral end surface of the gear portion 67 of the member 66.

  The drive member 66 is externally fitted to the reference member 71 so as to be relatively rotatable, and is engaged with the fitting member 59 so as not to be relatively rotatable. Therefore, each driving member 66 and each fitting member 59 are rotationally driven as a unit by the driving force transmitted to each driving member 66.

  Since each fitting member 59 is fitted to each left flange member 42L so as not to be relatively rotatable, a driving force can be transmitted from each drive member 66 to each left flange member 42L.

  In the left flange member 42L, the drum fitting portion 43 is fitted to the base tube 41 so as not to be relatively rotatable, and the left bearing fitting portion 44L is loosely fitted to the left bearing portion 40L of the left side plate 33L so as to be relatively rotatable. Further, the right flange member 42R is fitted with the drum fitting portion 43 so as to be relatively non-rotatable with the drum fitting portion 43, and the right bearing fitting portion 44R is loosely fitted with the right bearing portion 40R of the right side plate 33R so as to be relatively rotatable. Yes. Therefore, each photosensitive drum 12 is rotationally driven while being supported by the both side plates 33 by the driving force transmitted to each left flange member 42L.

Thus, the driving force transmitted from a driving source (not shown) such as a motor of the main casing 2 is applied to each left flange member 42L via each driving member 66 and each fitting member 59 of the left drum positioning member 53. Then, each photosensitive drum 12 can be driven to rotate.
4). Effect (1)
The color laser printer 1 includes a forward / backward member 50 including a left drum positioning member 53 and a right drum positioning member 54, and the photosensitive drum 12 supported by the drum unit 24.

  Specifically, the left drum positioning member 53 is provided on the left side in the main body casing 2 and includes a positioning shaft 55. The right drum positioning member 54 is provided on the right side in the main casing 2 and includes a positioning shaft 98.

  The photosensitive drum 12 includes a left flange member 42L at the left end portion and a right flange member 42R at the right end portion. A positioning hole 51 is formed in the sealing portion 48 of the left flange member 42L, and a shaft insertion hole 37 is formed in the sealing portion 48 of the right flange member 42R.

  The advancing / retracting member 50 has an advancing position in which the positioning shaft 55 enters the internal space of the positioning hole 51 of the left flange member 42L, and the positioning shaft 98 enters the internal space of the shaft insertion hole 37 of the right flange member 42R. The shaft 55 is separated from the positioning hole 51, and the positioning shaft 98 can be moved back and forth to a retracted position where it is separated from the shaft insertion hole 37.

  Therefore, in the advanced position, the positioning shaft 55 of the left drum positioning member 53 enters the positioning hole 51 of the left flange member 42L, and the positioning shaft 98 of the right drum positioning member 54 enters the shaft insertion hole 37 of the right flange member 42R. By entering, the photosensitive drum 12 can be positioned with respect to the main casing 2. Therefore, the positional relationship (drum pitch) of the photosensitive drum 12 with respect to the main body casing 2 can be kept constant.

  In other words, the left drum positioning member 53 and the right drum positioning member 54 can be used to mount the photosensitive drum 12 without providing the drum unit 24 with a side plate having accuracy and rigidity capable of keeping the relative positional relationship of the photosensitive drum 12 constant. Positioning with respect to the main body casing 2 is possible.

Therefore, while the weight of the drum unit 24 can be reduced and the material cost can be reduced, the positional relationship of the photosensitive drum 12 with respect to the main body casing 2 can be kept constant, and color misregistration can be prevented.
(2)
In the color laser printer 1, four photosensitive drums 12 are provided corresponding to black, yellow, magenta, and cyan, respectively, and are arranged in parallel at intervals in the front-rear direction. Further, four left drum positioning members 53 are provided so as to face the left flange members 42L of the four photosensitive drums 12 in the left-right direction.

Therefore, the color laser printer 1 can improve the positioning accuracy of each photosensitive drum 12 with respect to the main body casing 2, and can form a color image with high accuracy.
(3) The color laser printer 1 includes a pair of fixing plates 101 that are fixed to a frame (not shown) of the main body casing 2 and face each other with a gap in the left-right direction. The left drum positioning members 53 and the right drum positioning members 54 are fixed to the single fixing plate 101 at equal intervals in the front-rear direction.

  That is, since each left drum positioning member 53 and each right drum positioning member 54 are integrally fixed to the main body casing 2, each left drum positioning member 53 and each right drum positioning member 54 in the main body casing 2. The relative positional relationship of can be kept constant.

Therefore, it is possible to further improve the positioning accuracy of each photosensitive drum 12 with respect to the main body casing 2.
(4) The left drum positioning member 53 includes a gear portion 67 in which the axis line of the positioning shaft 55 and the rotation axis line coincide with each other.

  In detail, the gear part 67 forms the drive member 66 integrally with the outer cylinder part 68, and the drive member 66 is engaged with the fitting member 59 so that relative rotation is impossible.

  In the left drum positioning member 53, the positioning shaft 55 is inserted into the positioning hole 51 at the advanced position, and the fitting member 59 and the left flange member 42L are fitted so as not to be relatively rotatable.

Therefore, a deviation between the rotation center of the fitting member 59 (the axis of the positioning shaft 55) and the rotation center of the left flange member 42L (the center of the positioning hole 51) can be reduced, and the driving accuracy of the photosensitive drum 12 is improved. Can be achieved.
(5) Further, the color laser printer 1 includes a main body reference shaft 104 and a sandwiching portion 105 in the main body casing 2.

  When the drum unit 24 is attached to the main casing 2, the right side plate 33 </ b> R and the notch 38 of the left side plate 33 </ b> L of the drum unit 24 come into contact with the main body reference shaft 104. Further, both left and right end portions of the support shaft 29 supported by the front beam 34 of the drum unit 24 are sandwiched by the sandwiching portion 105.

  Therefore, the movement of the drum unit 24 in the front-rear direction and the up-down direction is restricted, and the drum unit 24 is positioned with respect to the main body casing 2.

Therefore, the positioning accuracy of the drum unit 24 with respect to the main body casing 2 can be improved.
(6) Specifically, the main body reference shaft 104 is provided on the rear side in the main body casing 2 (downstream in the mounting direction of the drum unit 24), and the clamping unit 105 is positioned on the front side in the main body casing 2 (mounting of the drum unit 24). (Upstream in the direction).

  Therefore, the front end portion and the rear end portion of the drum unit 24 are positioned with respect to the main body casing 2.

Therefore, the positioning accuracy of the drum unit 24 with respect to the main body casing 2 can be further improved.
(7) In the color laser printer 1, the drum exposure hole 39 is formed in the left side plate 33 </ b> L of the drum unit 24. The left flange member 42L of the photosensitive drum 12 is loosely fitted in the drum exposure hole 39 so as to be movable in the front-rear direction and the vertical direction.

  Therefore, when the positioning shaft 55 enters the positioning hole 51 of the left flange member 42L at the advance position of the left drum positioning member 53, the left flange member 42L appropriately moves to the play portion of the drum exposure hole 39. Can do.

Accordingly, it is possible to achieve a good entry of the positioning shaft 55 into the positioning hole 51.
(8) In the color laser printer 1, the frame 31 of the drum unit 24 is made of resin.

Therefore, it is possible to reduce the weight of the drum unit 24 and reduce the material cost.
5. Second Embodiment Next, a second embodiment of the present invention will be described.

  FIG. 9 is a side view showing a mounting state of the drum unit in the apparatus main body according to the second embodiment of the present invention.

9, parts corresponding to those shown in FIGS. 1 to 8 are denoted by the same reference numerals as those of the parts, and description thereof is omitted.
(1) Drum Exposed Hole In the first embodiment, as shown in FIG. 8, all the left bearing fitting portions 44L of the left flange member 42L in the four photosensitive drums 12 supported by the drum unit 24 correspond. The four drum exposure holes 39 are loosely fitted so as to be movable in the front-rear direction and the vertical direction.

  On the other hand, in the second embodiment of the present invention, as shown in FIG. 9, among the four photosensitive drums 12 supported by the drum unit 24, the rearmost photosensitive drum 12 (downstream side in the mounting direction of the drum unit 24). The left bearing fitting portion 44L is fitted to the corresponding drum exposure hole 39 so that the movement in the front-rear direction and the vertical direction is restricted. Further, the left bearing fitting portion 44L on the foremost side (the most upstream side in the mounting direction of the drum unit 24) is fitted to the corresponding drum exposure hole 39 so that the movement in the vertical direction is restricted.

  Specifically, of the four drum exposure holes 39, the rearmost drum exposure hole 39 is formed to have substantially the same diameter as the outer diameter of the left bearing fitting portion 44L.

  Therefore, among the four photosensitive drums supported by the drum unit 24, the left bearing fitting portion 44 </ b> L of the rearmost photosensitive drum 12 has a play in the corresponding drum exposure hole 39 (the rearmost drum exposure hole 39). These parts are fitted and the movement in the front-rear direction and the vertical direction is restricted.

  Of the four drum exposure holes 39, the frontmost drum exposure hole 39 is formed with a pair of horizontal straight portions 112 opposed in the vertical direction.

  The length of the pair of horizontal straight portions 112 is approximately ½ of the outer diameter of the left bearing fitting portion 44L of the left flange member 42L, and the distance between them is the left bearing fitting portion 44L. Is approximately the same length as the outer diameter of

For this reason, of the four photosensitive drums supported by the drum unit 24, the left bearing fitting portion 44L of the frontmost photosensitive drum 12 has a pair of sideways in the corresponding drum exposure hole 39 (frontmost drum exposure hole 39). Since the straight portion 112 is formed, there is a play portion in the front-rear direction, and there is no play portion in the vertical direction. Therefore, movement in the vertical direction is restricted.
(2) Main Body Reference Axis In the first embodiment, as shown in FIG. 8, the main body reference shaft 104 provided on the rear side in the main body casing 2 and the clamping parts provided on both the front left and right sides in the main body casing 2 105.

On the other hand, in the second embodiment of the present invention, the clamping portion 105 is not provided, and only the main body reference shaft 104 is provided on the rear side in the main body casing 2. The main body reference shaft 104 is formed as an example of a restricting member.
(3) Mounting of Drum Unit to Main Body Casing As shown in FIG. 9, in order to mount the drum unit 24 to the main body casing 2, first, the front cover 5 of the main body casing 2 is opened, and the drum unit 24 is attached to the main body casing 2. Guided. When the cutout portions 38 of the right side plate 33R and the left side plate 33L are in contact with the upper side and the front lower side of the main body reference shaft 104, further pressing of the drum unit 24 is restricted. Thus, the mounting of the drum unit 24 on the main casing 2 is completed.
(4) Positioning of photosensitive drum with respect to main body casing As described above in the first embodiment, the left drum positioning member 53 can be moved to the retracted position and the advanced position by opening and closing the front cover 5 and using a known interlocking mechanism. is there.

  When the front cover 5 is closed in a state where the drum unit 24 is mounted on the main casing 2, each left drum positioning member 53 moves from the retracted position to the advanced position. Then, each left drum positioning member 53 moves to the advance position and advances to the right, whereby each positioning shaft 98 of the left drum positioning member 53 is formed in the left bearing fitting portion 44L of the left flange member 42L. Then, it enters the internal space of each positioning hole 51.

  Specifically, the positioning shaft 98 of the left drum positioning member 53 is formed on the rearmost left bearing fitting portion 44L, the frontmost left bearing fitting portion 44L, and the other two left bearing fitting portions 44L, respectively. It enters the internal space of the positioning hole 51 made.

Therefore, the photosensitive drum 12 is positioned with respect to the main body casing 2 and the movement of the drum unit 24 in the front-rear direction is restricted by the left drum positioning member 53 corresponding to the rearmost left bearing fitting portion 44L. Further, the movement of the drum unit 24 in the vertical direction is restricted by the left drum positioning member 53 corresponding to the frontmost and rearmost left bearing fitting portion 44L. As described above, the four photosensitive drums 12 are positioned with respect to the main body casing 2, and the drum unit 24 is positioned with respect to the main body casing 2 while being restricted from moving in the front-rear direction and the vertical direction.
(5) Operational effect (5-1) In the second embodiment of the present invention, of the left bearing fitting portions 44L of the left flange member 42L of the four photosensitive drums 12, the rear left bearing fitting portion 44L corresponds. The drum exposure hole 39 is fitted so that movement in the front-rear direction and the vertical direction is restricted.

  Therefore, when the drum unit 24 is mounted on the main casing 2 and the left drum positioning member 53 is in the advanced position, the photosensitive drum 12 is positioned relative to the main casing 2 and the rear left bearing is fitted. The movement of the drum unit 24 in the front-rear direction is restricted by the left drum positioning member 53 corresponding to the portion 44L.

  Further, the front left bearing fitting portion 44L is loosely fitted to the corresponding drum exposure hole 39 so that the movement in the vertical direction is restricted by the pair of horizontal straight portions 112. That is, of the four left bearing fitting portions 44L, the front and rear left bearing fitting portions 44L are restricted from moving in the vertical direction with respect to the corresponding drum exposure holes 39.

  Therefore, when the drum unit 24 is attached to the main body casing 2 and the left drum positioning member 53 is in the advanced position, the photosensitive drum 12 is positioned with respect to the main body casing 2 and the front and rear left bearings are positioned. The movement of the drum unit 24 in the vertical direction is restricted by the left drum positioning members 53 respectively corresponding to the fitting portions 44L.

  Therefore, the movement of the drum unit 24 in the front-rear direction and the up-down direction is restricted, and the drum unit 24 is positioned with respect to the main body casing 2.

Therefore, as compared with the configuration in which the holding portion 105 is provided on the front side of the main casing 2 as in the first embodiment, the number of parts can be reduced, but the positioning accuracy of the drum unit 24 with respect to the main casing 2 is improved. Improvements can be made.
(5-2) Specifically, the left bearing fitting portion 44L that is restricted from moving in the front-rear direction and the up-down direction is located on the rearmost side of the four bearing fitting portions, and a pair of horizontal The left bearing fitting portion 44 </ b> L whose movement in the vertical direction is restricted by the straight portion 112 is located on the foremost side.

  Therefore, the movement of the main casing 2 in the vertical direction is restricted on the front side and the rear side of the drum unit 24, respectively.

Therefore, the positioning accuracy of the drum unit 24 with respect to the main body casing 2 can be further improved.
(5-3) In the second embodiment of the present invention, the main body reference shaft 104 is provided in the main body casing 2.

  When the drum unit 24 is attached to the main casing 2, the right side plate 33 </ b> R and the notch 38 of the left side plate 33 </ b> L of the drum unit 24 come into contact with the main body reference shaft 104.

  Therefore, when the drum unit 24 is attached to the main casing 2, it is possible to prevent the drum unit 24 from being pushed more than necessary.

Therefore, the positioning accuracy of the drum unit 24 with respect to the main body casing 2 can be improved.
(5-4) In the second embodiment of the present invention, in the state where the drum unit 24 is mounted on the main body casing 2, the main body reference shaft 104 and the left bearing fitting in which movement in the front-rear direction and the up-down direction is restricted. The positional relationship with the joining portion 44L can be kept constant.

  Accordingly, the interval between the four photosensitive drums 12 can be set based on the positional relationship.

  Although the second embodiment of the present invention has been described above, the present invention can be implemented in other forms.

  For example, in the second embodiment described above, of the four drum exposure holes 39, the rearmost drum exposure hole 39 is formed to have substantially the same diameter as the outer diameter of the left bearing fitting portion 44L. As shown in FIG. 10, a pair of horizontal straight portions 112 and vertical straight portions 113 can be formed in the rearmost drum exposure hole 39, respectively.

  Specifically, the length of the pair of horizontal straight portions 112 is approximately ½ of the outer diameter of the left bearing fitting portion 44L of the left flange member 42L, and the interval between the pair of horizontal straight portions 112 is the left bearing fitting. The length is substantially the same as the outer diameter of the joining portion 44L.

  Further, the length of the pair of vertical straight portions 113 is approximately ½ of the outer diameter of the left bearing fitting portion 44L of the left flange member 42L, and the interval between them is the left bearing fitting. The length is substantially the same as the outer diameter of the portion 44L.

This also moves the left bearing fitting portion 44L of the rearmost photosensitive drum 12 among the four photosensitive drums 12 in the front-rear direction and the vertical direction with respect to the corresponding rearmost drum exposure hole 39. It can be fitted to be regulated.
6). Third Embodiment Next, a third embodiment of the present invention will be described.

  FIG. 11 is a cross-sectional view for explaining the retracted position of the advance / retreat member in the third embodiment of the present invention. FIG. 12 is a cross-sectional view for explaining the advance position of the advance / retreat member in the third embodiment of the present invention.

11 and 12, portions corresponding to the respective portions shown in FIGS. 1 to 8 are denoted by the same reference numerals as those of the respective portions, and the description thereof is omitted.
(1) Positioning shaft In the first embodiment, as shown in FIGS. 6 and 7, four right drum positioning members 54 including a reference member 91, a spring member 95, a shaft holding member 90, and a positioning shaft 98 are provided. It has been.

  On the other hand, in the third embodiment of the present invention, as shown in FIGS. 11 and 12, four positioning shafts 115 are provided.

  The positioning shaft 115 has an outer diameter that is substantially the same as the inner diameter of the positioning hole 51, and has a tip that is tapered.

  Each positioning shaft 115 is fixed by being inserted into a shaft fixing hole 116 formed in the fixing plate 101 and positioned with respect to the main body casing 2.

  Specifically, as shown in FIG. 12, each positioning shaft 115 is configured such that the left drum positioning member 53 advances to the advanced position in a state where the drum unit 24 is mounted on the main body casing 2, so that the drum unit 24 is moved to the right as a whole. When it moves to the right, it is arranged so as to enter the positioning hole 51 of the corresponding photosensitive drum 12 from the right side. Then, a shaft fixing hole 116 is formed at a position corresponding to a base end portion of each positioning shaft 115 in the fixing plate 101, and each positioning shaft 115 is inserted into the shaft fixing hole 116, thereby positioning each positioning shaft 115. The shaft 115 is fixed.

  Thus, the four positioning shafts 115 are positioned with respect to the main body casing 2. Further, the four positioning shafts 115 are fixed to one fixed plate 101 at equal intervals in the front-rear direction.

The left drum positioning members 53 and the positioning shafts 115 are opposed to each other at an interval so as to share the central axis in the left-right direction.
(2) Positioning of Photosensitive Drum with respect to Main Body Casing As described above in the first embodiment, the left drum positioning member 53 can be moved between the retracted position and the advanced position by a known interlocking mechanism as the front cover 5 is opened and closed. is there.

  When the drum unit 24 is mounted on the main casing 2 and the left drum positioning member 53 is in the retracted position, each positioning shaft 115 is formed on each right flange member 42R of the photosensitive drum 12 on the right side in the main casing 2. The shaft insertion hole 37 and the tip end portion thereof are opposed to each other with an interval in the left-right direction.

  Further, when the left drum positioning member 53 is in the advanced position, the left drum positioning member 53 advances to the right, whereby the drum unit 24 is moved to the right as a whole via each left flange member 42L. As the drum unit 24 moves to the right, the distal end portion of the positioning shaft 115 comes into contact with the sword portion 52 formed in the sealing portion 48 of the right flange member 42R, and the positioning shaft 115 is positioned in the positioning hole 51. Then, the positioning shaft 115 enters the positioning hole 51.

As described above, the four photosensitive drums 12 are positioned in the front-rear direction and the vertical direction with respect to the main body casing 2 by the four left drum positioning members 53, the four positioning shafts 115, and the two fixing plates 101.
(3) Effects In the third embodiment, a positioning shaft 115 is provided instead of the right drum positioning member 54 of the first embodiment described above.

  The right drum positioning member 54 described above includes a reference member 91, a spring member 95, and a shaft holding member 90 in addition to the positioning shaft 98.

  That is, the positioning shaft 115 is formed with a smaller number of parts than the right drum positioning member 54 described above.

  When the drum unit 24 is attached to the main casing 2 and the left drum positioning member 53 is in the advanced position, the positioning shaft 115 is positioned inside the positioning hole 51 formed in the sealing portion 48 of the right flange member 42R. Enter the space.

  Therefore, the photosensitive drum 12 can be positioned with respect to the main body casing 2 while the number of parts can be reduced.

DESCRIPTION OF SYMBOLS 1 Color laser printer 2 Main body casing 12 Photosensitive drum 31 Frame 39 Drum exposure hole 41 Base pipe 42 Flange member 50 Advance / retreat member 55 Positioning shaft 67 Gear part 98 Positioning shaft 101 Fixing plate 104 Main body reference axis 105 Holding part

Claims (13)

The device body;
A photosensitive drum comprising a raw tube and supported members provided at both axial ends of the raw tube;
A support member that is rotatably attached to the supported member and is mounted so as to be able to be pulled out with respect to the apparatus main body;
It is provided in the main body of the apparatus and is disposed opposite to the photosensitive drum in the axial direction of the photosensitive drum, and is movable to an advancing position that advances toward the photosensitive drum and a retracted position that is separated from the photosensitive drum. A moving member,
The moving member includes a first positioning portion for engaging with the supported member on one end side in the axial direction of the photosensitive drum at the advanced position and positioning the photosensitive drum with respect to the apparatus main body. An image forming apparatus as a feature. A plurality of the photosensitive drums are provided, and are arranged in parallel along the mounting direction of the support member, spaced apart from each other.
The image forming apparatus according to claim 1, wherein a plurality of the moving members are provided so as to face each of the photosensitive drums.   The image forming apparatus according to claim 2, further comprising a fixing member that fixes the plurality of moving members.   The moving member includes a second positioning portion for engaging the supported member on the other axial end side of the photosensitive drum at the advanced position and positioning the photosensitive drum with respect to the apparatus main body. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The first positioning portion is a shaft member;
The moving member is arranged so that the axis of the shaft member and the axis of rotation coincide with each other, and the driving force transmitted from the driving source provided in the apparatus main body is transmitted to the supported member. The image forming apparatus according to claim 1, wherein a rotating body is provided.   The image forming apparatus according to claim 1, wherein the apparatus main body includes a positioning member for positioning the support member with respect to the apparatus main body. The support member is provided with a through-hole facing the photosensitive drum in the axial direction of the photosensitive drum,
The supported member has a first direction that is a mounting direction and a drawing direction of the support member with respect to the through hole, and a second direction that is orthogonal to both the first direction and the axial direction of the photosensitive drum. The image forming apparatus according to claim 6, wherein the image forming apparatus is loosely fitted so as to be movable.   The image forming apparatus according to claim 6, wherein the positioning member is provided on the upstream side in the mounting direction and the downstream side in the mounting direction of the support member. The support member is provided with a plurality of through holes corresponding to the photosensitive drums,
Of the supported members of each of the photosensitive drums, one of the supported members has a first direction that is a mounting direction and a drawing direction of the support member with respect to the corresponding through hole, and the first direction and The photosensitive drum is fitted so as to be restricted from moving in a second direction perpendicular to both axial directions of the photosensitive drum,
Another one of the supported members is loosely fitted to the corresponding through hole so as to be movable in the first direction and restricted in movement in the second direction,
The other supported members are loosely fitted to the corresponding through-holes so as to be movable at least in the first direction. Image forming apparatus. The supported member to be fitted so that movement in the first direction and the second direction is restricted is located on the most downstream side in the mounting direction of the support member,
The supported member that is loosely fitted so as to be movable in the first direction and restricted in movement in the second direction is located on the most upstream side in the mounting direction of the support member. The image forming apparatus according to 9.   The image forming apparatus according to claim 9, wherein the apparatus main body includes a regulating member for positioning a downstream end portion in a mounting direction of the support member.   The image forming apparatus according to claim 11, wherein an interval between each of the photosensitive drums in the first direction is set based on the restriction member.   The image forming apparatus according to claim 1, wherein the support member is made of resin.