JP4689246B2 - Image forming apparatus - Google Patents

Description

The present invention relates to an image forming apparatus, and more particularly, such as a laser printer using a child photographic method electrostatic printer, copier, facsimile machine, an image forming apparatus that put on like these MFP.

  2. Description of the Related Art Conventionally, in a color image forming apparatus such as a so-called tandem color printer, color copying machine, or the like, which is configured by arranging a plurality of photosensitive drums that are rotating bodies in a line, a photosensitive drum (hereinafter simply referred to as “photosensitive body”). ) Is known (see Patent Documents 1 to 4).

  With reference to FIGS. 9 and 10, an example of a method of aligning the axis of the drum-shaped photoconductor 10 in the conventional color image forming apparatus will be described. FIG. 9 shows a bearing positioning configuration of the photoconductor 10, and FIG. 10 schematically shows an enlarged and exaggerated detail configuration equivalent to the bearing positioning configuration of the photoconductor 10 shown in FIG. In both figures, reference numeral 70 denotes a rotation driving device for rotating the photosensitive member 10 as a rotating member. The rotational drive device 70 corresponds to, for example, a conventional example of a plurality of rotational drive devices disposed in the printer 1 of FIG. 1 showing an embodiment of the present invention described later.

  As shown in FIGS. 9 and 10, the rotation driving device 70 is attached to and detached from a photosensitive member drive shaft 29 in which a photosensitive member shaft 28 b as one shaft of the photosensitive member 10 drives the photosensitive member 10 through a coupling portion 35. It is configured freely. When the photosensitive member shaft 28b is connected to the photosensitive member driving shaft 29 via the coupling portion 35, the photosensitive member 10 is connected between a driving gear 39 and a pulley that constitute a gear train for rotationally driving the photosensitive member 10. It is rotationally driven by a driving means (not shown) such as a driving motor via a driving force transmission means such as an endless belt (not shown).

  In the rotation driving device 70, the photosensitive member shaft 28a as the other shaft of the photosensitive member 10 is connected to the ball bearing 31 as the first bearing, the photosensitive member shaft 28b is connected to the ball bearing 32 as the second bearing, and the coupling portion. The photoconductor drive shaft 29 on the side facing the photoconductor shaft 28b through the ball 35 is connected to a ball bearing 73 as a third bearing, and the photoconductor drive shaft 29 on the side facing a driving means (not shown) such as a drive motor. Are rotatably supported by a ball bearing 34 as a fourth bearing, and the ball bearing 31, the ball bearing 32, the ball bearing 73, and the ball bearing 34 are connected to the apparatus main body 26 (face plate unit 27, main body side plate 26a, holder 40, and By positioning and fixing with respect to the side plate bracket 26b), the photoconductor shaft 28a, the photoconductor shaft 28b, and the photoconductor drive shaft 29 are aligned with each other.

  Specifically, the ball bearing 31 is positioned with respect to the face plate unit 27 which is positioned and supported so as to be detachable with respect to the apparatus main body 26, and the ball bearing 34 is fixed to the apparatus main body 26. The ball bearing 32 and the ball bearing 73 are positioned with respect to the holder 40 fixed to the main body side plate 26a. In other words, when positioning is performed with the above-described bearings, tolerance increases with the photosensitive member shaft 28a-ball bearing 32-32 holder 40-ball bearing 73-photosensitive member driving shaft 29.

  The photoconductor 10, the photoconductor shafts 28a and 28b, the ball bearings 31 and 32, and the coupling portion 35 on the side facing the photoconductor shaft 28b appropriately constitute a process constituting an image forming unit integrated with a developing device or the like. A cartridge unit (hereinafter abbreviated as “PCU”) 71 is configured to be detachable from the apparatus main body 26, that is, to be detachable in a direction indicated by a double arrow in FIG. 10 through a guide support member (not shown). ing. In addition, in FIG. 9, illustration of the circumference | surroundings including the holder 40 is abbreviate | omitted (FIG. 2 which shows embodiment mentioned later is also the same).

JP 2000-214654 A JP 2000-227696 A JP 2001-147618 A JP 2003-186348 A

  However, in the method of aligning the axis of the photosensitive member 10 in the rotation driving device 70 shown in FIGS. 9 and 10, the photosensitive member is driven unless the four ball bearings 31, 32, 73, 34 as rolling bearings are positioned at the ideal positions. The shaft 29 and the photoconductor shafts 28a and 28b are displaced from each other, the engagement of the coupling portion 35 is deteriorated, and the fluctuation of the angular velocity of the photoconductor drive shaft 29 is increased by the coupling portion 35 and transmitted to the photoconductor 10. This was one of the causes of color misregistration.

In order to deal with this problem, there have been practiced cases in which a penetrating shaft in which the photosensitive member driving shaft and the photosensitive member shaft are integrated is used. However, this method has a problem that it is difficult to replace the PCU. In addition, a method of positioning each bearing at an ideal position is also conceivable, but for this purpose, the cost for molding the main body becomes very high, and it is technically difficult in view of the accumulation of dimensional tolerances.
It is also possible to position the photosensitive member shaft and the photosensitive member drive shafts by holes and bosses. However, if it is necessary to electrically insulate the photosensitive member shaft from the photosensitive member drive shaft, a metal shaft is used. Positioning with each other is not possible.

Accordingly, the present invention has been made in view of the above-described points, and accurately aligns the axis of the photosensitive member drive shaft such as a photosensitive drum that is a rotating member and also an image bearing member and the shaft of the photosensitive member shaft. Accordingly, an image forming apparatus capable of suppressing an increase in angular velocity fluctuation at the time of driving delivery of a coupling portion due to a shift of an axis is provided, and an image forming apparatus capable of forming a color image having a plurality of photoconductors that it has the primary purpose of reducing color shift in.

In order to solve the above-described problems and achieve the above-mentioned object, the invention according to each claim employs the following characteristic means / invention specific items (hereinafter referred to as “configuration”).
According to the first aspect of the present invention, one shaft of the photoconductor is configured to be detachable from a drive shaft that drives the photoconductor via a coupling, and the other shaft of the photoconductor is a first bearing. The one shaft is rotatably supported by the second bearing, the drive shaft on the one shaft side is rotatably supported by the third bearing, and the drive shaft is supported by the fourth bearing via the coupling. In the image forming apparatus in which the first to fourth bearings are positioned and fixed with respect to the apparatus main body so that the axes of the one shaft, the other shaft, and the drive shaft are aligned, the second bearing and the second bearing The third bearing is positioned and fixed with respect to a support member fixed on the apparatus main body side, and the first bearing, the second bearing, and the fourth bearing are ball bearings , and the third bearing Is the drive shaft on the one shaft side in the direction orthogonal to the center line of the drive shaft. A sliding bearing having a predetermined clearance, and has a positioning means separate from the coupling for aligning the axis of the one shaft and the drive shaft on the one shaft side, and the cup The positioning means separate from the ring includes a positioning hole formed in the center of any one of the one shaft end and the drive shaft end on the one shaft side, the one shaft end and the one A face plate unit, which is fixed to the center of one of the drive shaft ends on one shaft side and is configured integrally with the photosensitive member and detachable from the apparatus main body, is positioned and fixed to the apparatus main body. Ri Do and a positioning pin for positioning fitted without play into the positioning hole in the circumferential direction when occupied mounting position, positioning is formed in the ball bearing unit, an axial end portion of the one of the first bearing the Positioning hole and the one shaft side And wherein the performed axis alignment precision between the serial drive shaft end lightly press-fitted to said positioning pin portion, the accumulation of tolerances of three points of the ball bearing unit is a fourth bearing with respect to the apparatus body of the drive shaft To do.
Here, the face plate unit unitized on the first bearing fixing side is detachable from the apparatus main body on the fourth bearing fixing side, and is attached to the apparatus main body on the fourth bearing fixing side. The face plate unit that is positioned and fixed to the apparatus main body when it is done is also included (hereinafter the same).

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect , at least one of the positioning hole forming portion and the positioning pin is formed of an electrically insulating material .
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, a plurality of the photoreceptors are provided, and color image formation is possible .

According to the present invention, the configuration described in each claim can solve the above problems and provide a novel image forming apparatus. The main effects of the invention are as follows.
According to the present invention, positioning is lightly press-fitted into the ball bearing portion which is the first bearing, the positioning hole formed in one shaft end portion of the photosensitive member, and the driving shaft end portion on one shaft side of the photosensitive member. This is done by accumulating the tolerance of the three points of the ball bearing portion which is the fourth bearing with respect to the apparatus main body of the driving shaft of the photosensitive member and the accuracy of alignment with the positioning pin. The accumulation of tolerances of components, etc.) is reduced, and the shaft center of the photosensitive member drive shaft and the photosensitive member shaft can be accurately aligned, and the increase in angular velocity fluctuations in the coupling portion due to the shaft core displacement is suppressed. In addition, since the margin of the bearing positioning portion of the apparatus main body is more than conventional, the cost and the molding technique are advantageous.
Further, in an image forming apparatus capable of forming a color image , in addition to the above effects, color misregistration can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings. In the conventional example, the embodiment, the modified example, and the like shown in FIGS. 9 and 10, the constituent elements such as members and components having the same function and shape are once described by attaching the same reference numerals. The description is omitted as much as possible. In order to simplify the drawings and the description, even components that are to be represented in the drawings may be omitted as appropriate without being specifically described in the drawings. When quoting and explaining constituent elements such as published patent gazettes, the reference numerals are shown in parentheses to distinguish them from those of the embodiments.

  In this embodiment, the image forming apparatus is a color printer 1 (hereinafter abbreviated as “printer 1”) that can form a full-color image by employing a tandem method.

First, the basic configuration and operation of the printer 1 will be described with reference to FIG. The printer 1 shown in FIG. 1 has a configuration in which a paper feeding unit 2 that stores paper P as a recording material is disposed at the bottom of an apparatus main body 26 and an image forming unit 3 is disposed above the paper feeding unit 2. The image forming unit 3 includes an image forming unit 8 including four image forming units 8Y, 8C, 8M, and 8BK as a plurality of image forming units including an image carrier, and a plurality of rollers 4, 5, 6 and An intermediate transfer unit 7 having an intermediate transfer belt 7a as an intermediate transfer member constituted by a flexible endless belt wound around these rollers 4, 5 and 6, and optical writing on each image carrier. An optical writing unit 15 as an optical writing unit to perform and a fixing device 19 for fixing the toner image on the paper P are provided.
The image forming units 8Y, 8C, 8M, 8BK and the intermediate transfer unit 7 are configured to be detachable from the apparatus main body 26, respectively. That is, each of the image forming units 8Y, 8C, 8M, and 8BK constitutes a PCU, and can be detached to the front side of the paper surface when a front door (not shown) is opened. Between the sheet feeding unit 2 and the fixing device 19, a conveyance path R for conveying the sheet P on which an image is formed by the image forming unit 3 is formed. The roller 6 constitutes a secondary transfer device which will be described later, and is disposed facing the conveyance path R indicated by a one-dot chain line. An end portion R1 of the transport path R is opened to face a paper discharge tray 22 as a stacking portion constituting the paper discharge portion 20 formed in the upper portion of the apparatus main body 26.

  The space between the roller 4 and the roller 5 of the intermediate transfer belt 7a corresponds to the lower side belt running side of the belt 7a. In the intermediate transfer belt 7 a, a secondary transfer roller 16 serving as a secondary transfer device is disposed at a portion facing the roller 6 so as to face the conveyance path R, and a belt for cleaning the belt surface at a portion facing the roller 4. A cleaning device 17 is provided.

The image forming unit 8 is disposed below the intermediate transfer belt 7a by being disposed so as to face the lower belt running side of the intermediate transfer belt 7a. In the present embodiment, the image forming units 8Y, 8C, 8M, and 8BK have basically the same configuration, and in FIG. 1, only the components of the image forming unit 8BK are denoted by reference numerals. Each of the image forming units 8Y, 8C, 8M, and 8BK includes a drum-shaped photoconductor 10 as an image carrier in contact with the intermediate transfer belt 7a, a charging device 11, a developing device 12, and a cleaning device 13.
Around each photoreceptor 10, a charging device 11, a developing device 12, and a cleaning device 13 are arranged. Transfer rollers 14 as transfer means for performing primary transfer are provided inside the intermediate transfer belt 7a at positions where the respective photoreceptors 10 are in contact with the intermediate transfer belt 7a. The image forming units 8Y, 8C, 8M, and 8BK have different configurations in that the color of toner as a developer contained in each developing device 12 is different. The developing devices 12 of the image forming units 8Y, 8C, 8M, and 8BK contain yellow, cyan, magenta, and black toners, respectively. Each developing device 12 is configured such that when toner is reduced, replenishing toner is supplied from toner replenishing bottles T1, T3, T3, and T4 disposed on the upper portion of the apparatus main body 26, respectively.

  The optical writing unit 15 irradiates the surface of each photoconductor 10 with the light-modulated laser beam L, and forms a latent image for each color on the surface of the photoconductor. In the present embodiment, the image forming unit 8 is disposed below.

  In the printer 1 shown in FIG. 1, when an image forming operation is started, the photoconductor 10 of each image forming unit 8 is rotationally driven in a clockwise direction by a driving device (not shown), and the surface of each photoconductor 10 is charged by a charging device 11. Are uniformly charged to a predetermined polarity. The surface of each charged photoconductor 10 is irradiated with laser light L from the optical writing unit 15 to form an electrostatic latent image on each surface. At this time, the image information to be exposed on each photoconductor 10 is single-color image information obtained by separating a desired full-color image into color information of yellow, cyan, magenta, and black. The electrostatic latent image formed in this way is visualized as a toner image by the toner of each developing device 12 when passing between each photoconductor 10 and the developing device 12.

  One of the plurality of rollers 4, 5 and 6 around which the intermediate transfer belt 7a is wound is driven to rotate counterclockwise by a driving device (not shown), whereby the intermediate transfer belt 7a is indicated by an arrow. The other rollers are driven to rotate by being driven in the counterclockwise direction shown. A yellow toner image formed by the image forming unit 8Y including the developing device 12 having yellow toner is transferred by the transfer roller 14 to the intermediate transfer belt 7a that travels in this manner. To the transferred yellow toner image, a cyan toner image formed by the image forming units 8C, 8M, and 8BK, a magenta toner image, and a black toner image are sequentially superimposed and transferred by the transfer roller 14, and the intermediate transfer belt 7a is thus transferred. A full-color toner image is carried on the surface.

  Residual toner adhering to the surface of each photoconductor 10 after the toner image is transferred is removed from the surface of the photoconductor 10 by each cleaning device 13, and then the surface is subjected to a static elimination action by a static elimination device (not shown). The surface potential is initialized to prepare for the next image formation.

  On the other hand, the sheet P fed from the sheet feeding unit 2 is sent to the conveyance path R, and a pair of registration rollers disposed on the upstream side (the sheet feeding unit 2 side) of the conveyance path R with respect to the secondary transfer roller 16. The sheet feeding timing is taken by 18, and the roller 6 and the secondary transfer roller 16 are fed to the facing transfer portion. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the surface of the intermediate transfer belt 7 a is applied to the secondary transfer roller 16, whereby the toner image on the surface of the intermediate transfer belt 7 a is collectively put on the paper P. Is transcribed. The sheet P to which the toner image has been transferred is conveyed to the fixing device 19, and when passing through the fixing device 19, heat and pressure are applied to melt and fix the toner image. The sheet P on which the toner image is fixed is conveyed to the discharge unit 21 disposed at the end R1 of the conveyance path R and is discharged to the discharge tray 22. After the toner image is transferred to the paper P, the toner remaining on the belt is removed from the belt cleaning device 17 by the intermediate transfer belt 7a.

  The tandem type printer 1 configured as described above has four image forming units 8Y, 8M, 8C, and 8BK facing the intermediate transfer belt 7a, and sequentially transfers the toner images of the respective colors onto the intermediate transfer belt 7a. Therefore, for example, the image forming time is significantly shortened compared to the type in which a single image forming unit has a four-color developing device, and a toner image is transferred onto an intermediate transfer belt and then transferred onto a sheet. can do. Further, since the paper discharge tray 22 as a stacking portion is disposed on the upper portion of the apparatus main body 26, the paper discharge tray 22 does not jump out from the apparatus main body 26 to the surroundings, and the installation area and the occupied area are reduced. Have.

  The above description is an image forming operation when a full-color image is formed on the paper P. A single-color image can be formed using any one of the image forming units of the image forming unit 8, or two colors or A three-color image can also be formed. Further, when performing monochrome printing using the printer 1 of the present embodiment, an electrostatic latent image is formed only on the photoreceptor 10 of the image forming unit 8BK, developed by the unit, transferred to the paper P, Fixing may be performed by the fixing device 19.

Next, with reference to FIG. 2 to FIG. 7, a rotational drive device and a method of aligning the axis of the photosensitive member, which are characteristic configurations of the present embodiment, will be described.
2 to 7, reference numeral 25 denotes a rotation driving device that rotationally drives the photosensitive member 10 as a rotating member. The rotation driving device 25 is disposed corresponding to each of the image forming units 8Y, 8M, 8C, and 8BK of the printer 1 shown in FIG. 2 and 3 show the bearing positioning configuration of the photoconductor 10 in the rotary drive device 25, and FIGS. 4 and 5 show the bearing positioning configuration of the photoconductor 10 in the rotary drive device 25 shown in FIGS. An equivalent detailed configuration is schematically shown in an enlarged and exaggerated manner.

  The rotation drive device 25 uses a plain bearing 33 instead of the ball bearing 73 which is an example of a rolling bearing as the third bearing, as compared with the conventional rotation drive device 70 shown in FIGS. 9 and 10. The point and the point which has a positioning means separate from the coupling part 35 are mainly different.

The following description will focus on the configuration of the above-described difference of the rotary drive device 25, but the configuration similar to that of the rotary drive device 70 and details of the method of aligning the axes will also be supplemented.
As shown in FIGS. 2 to 6, in the rotary drive device 25, the photosensitive member shaft 28a as the other shaft of the photosensitive member 10 is a ball bearing 31 as a first bearing, and the photosensitive member shaft 28b is a second bearing. The photosensitive member driving shaft 29 on the side facing the photosensitive member shaft 28b through the coupling portion 35 is connected to the sliding bearing 33 as the third bearing, and driving means (not shown) (for example, a driving motor). The photosensitive member drive shaft 29 on the side is rotatably supported by a ball bearing 34 as a fourth bearing, and the ball bearing 31, the ball bearing 32, the slide bearing 33, and the ball bearing 34 are connected to the apparatus main body 26 (face plate unit 27, Positioning and fixing with respect to the main body side plate 26a, the holder 40 and the side plate bracket 26b), and alignment with a positioning means (see FIGS. 4 to 6) separate from the coupling portion 35. Through It is characterized by combining the axial of the photoreceptor shaft 28a and the photosensitive member shaft 28b and the photosensitive member drive shaft 29.

The apparatus main body 26 is made of a sheet metal such as a steel sheet or resin that has been subjected to an appropriate surface treatment. The main body side plate 26a and the side plate bracket 26b are formed of a sheet metal such as a steel plate subjected to an appropriate surface treatment. The face plate unit 27 is formed of, for example, a resin in which a sheet metal is appropriately inserted.
The face plate unit 27, the photoconductor 10, the photoconductor shafts 28a and 28b, the ball bearings 31 and 32, and the coupling 35a on the photoconductor shaft 28b side constitute the image forming units 8Y, 8M, 8C, and 8BK (PCU). Thus, it can be attached to and detached from the apparatus main body 26, that is , can be inserted / removed / opened / opened in the direction indicated by the double arrow in FIG. 4 via a guide support member (not shown) in the present embodiment . FIG. 5 shows a state when the face plate unit 27 in each of the image forming units 8Y, 8M, 8C, and 8BK (PCU) is detached from the apparatus main body 26 in the direction indicated by the arrow.

  The face plate unit 27 is inserted / removed at the time of replacement of the image forming units 8Y, 8M, 8C, and 8BK, the developing device 12, etc., or the intermediate transfer unit 7 shown in FIG. This is a well-known configuration for opening and closing work. When the face plate unit 27 occupies a mounting position where the face plate unit 27 is mounted and positioned and fixed, the face plate unit 27 is positioned in the apparatus main body 26 in a three-dimensional direction in conjunction with a lock mechanism (not shown) that locks the face plate unit 27 to the apparatus main body 26.・ It is fixed.

  For convenience of explanation, the photosensitive member shaft 28a and the photosensitive member shaft 28b are described with reference numerals separately. However, the photosensitive member shaft 28a and the photosensitive member shaft 28b are shown by broken lines in FIGS. A single shaft member that is long and passes through both end plates of the photoconductor 10, and is fixed to each end plate after the shaft cores are aligned on both sides of each end plate. The photoreceptor shafts 28a and 28b are made of, for example, a steel material.

  As shown in FIGS. 2 to 5, the ball bearing 31 is positioned by lightly press-fitting (hereinafter referred to as “light press-fitting”) the photoreceptor shaft 28 a into the inner ring (hereinafter referred to as “inner race”) of the ball bearing 31. The ball bearing 31 is positioned and supported by the face plate unit 27 by lightly press-fitting an outer ring (hereinafter referred to as “outer race”) into the hole of the face plate unit 27 and fixing it. Therefore, when the face plate unit 27 is mounted on the apparatus main body 26 together with the image forming units 8Y, 8M, 8C, and 8BK and occupies the mounting position, the ball bearing 31 is positioned and fixed to the apparatus main body 26. The ball bearing 31 is finally positioned and fixed in the three-dimensional direction with respect to the apparatus main body 26 by restricting the movement of the photosensitive shaft 28a in the axial direction by a retaining ring (not shown).

  For safety reasons, there are devices that prevent the user from easily detaching and opening each image forming unit (PCU) from the device body 26 together with the face plate unit. However, the positioning method is basically described above. It is the same.

  The ball bearing 34 is positioned by lightly press-fitting the photosensitive member drive shaft 29 on the side facing the drive motor into the inner race of the ball bearing 34, and a side plate bracket 26b in which the outer race of the ball bearing 34 is fixed to the main body side plate 26a. This is achieved by being positioned and supported by the apparatus main body 26 via the side plate bracket 26b by being lightly press-fitted into the holes and fixed. The ball bearing 34 is restricted in movement in the axial direction of the photosensitive member drive shaft 29 by a retaining ring (not shown), and is finally positioned and fixed in the three-dimensional direction with respect to the apparatus main body 26.

  The holder 40 as a support member fixed on the apparatus main body 26 side is integrally formed of, for example, an electrically insulating resin, and is fixedly attached to the main body side plate 26a by fastening means such as screws. As the resin forming the holder 40, for example, the frictional resistance at the time of attaching / detaching to / from the outer race peripheral surface of the ball bearing 32 made of steel or the outer peripheral surface of the slide bearing 33 is reduced and wear resistance is reduced. Polyacetal resin (POM), polyamide resin (PA), or suitable engineering plastic is used. If this advantage is not desired, the holder 40 may be formed of sheet metal or the like.

  As shown in FIGS. 2 to 5, the ball bearing 32 is positioned by lightly press-fitting the photosensitive member shaft 28b into the inner race and restricting the axial movement of the photosensitive member shaft 28b with a retaining ring (not shown). By inserting the outer race of the ball bearing 32 into a recess (not shown) formed in the inner peripheral portion of the holder 40 and inserting the outer race of the ball bearing 32, the holder 40 is positioned on the apparatus main body 26. The Rukoto.

The slide bearing 33 that rotatably supports the photoconductor drive shaft 29 is formed of, for example, a sintered alloy or an oil-containing resin that does not require lubricating oil, and is a photoconductor shaft in a direction orthogonal to the center line of the photoconductor drive shaft 29. With a clearance fit (the outer diameter of the photosensitive member drive shaft 29 is a negative tolerance and the inner diameter of the bearing is a positive tolerance) having a predetermined gap between the outer peripheral surface and the outer diameter of the photosensitive member drive shaft 29 on the side facing the surface 28b. It is a necessary condition. As the set value of the minimum clearance (clearance fit) as the predetermined gap, from the results of experiments and the like, the minimum value of the inner diameter of the slide bearing 33-the maximum value of the outer diameter of the photosensitive member drive shaft 29 = 0.01 is the minimum clearance. It has been found that it should be in the range of ~ 0.1 mm.
If the minimum clearance is smaller than 0.01 mm, the effect of the alignment of the shaft cannot be expected, and the workability at the time of fitting / attaching the photosensitive member drive shaft 29 to the slide bearing 33 is deteriorated. If it exceeds 0.1 mm, the effect of aligning the shaft center cannot be expected, and the function as a bearing cannot be exhibited.

The slide bearing 33 is positioned by inserting the photoconductor drive shaft 29 on the side facing the photoconductor shaft 28b into the inner periphery of the slide bearing 33, and using a retaining ring (not shown) to place the slide bearing 33 in the axial direction of the photoconductor drive shaft 29. Is inserted into the holder 40, and the outer race of the slide bearing 33 is fitted into a recess (not shown) formed in the inner periphery of the holder 40, so that the holder 40 is fixed. It will be positioned by the apparatus main body 26 which has it.
A drive gear 39 for rotationally driving the photoreceptor 10 is fixed on the photoreceptor drive shaft 29 between the slide bearing 33 and the ball bearing 34. The drive gear 39 is connected to a drive motor as drive means (not shown) via a gear train (not shown).

  As shown in FIGS. 4 to 6, the positioning means separate from the coupling portion 35 includes a positioning hole 36 formed at the center of the right end portion of the photoconductor shaft 28b and the side facing the photoconductor shaft 28b. In the drawing of the photosensitive member drive shaft 29, it is composed of a positioning pin 37 as a rod-like portion that is press-fitted and fixed at the center of the left end portion and fits into the positioning hole 36 without play when the face plate unit 27 occupies the mounting position. The positioning pin 37 is made of, for example, a resin that is an electrically insulating material.

  The positioning means separate from the coupling portion 35 is not limited to the above, and a positioning pin as a rod-shaped portion may be provided on the photosensitive member shaft 28b side, and a positioning hole may be provided on the photosensitive member driving shaft 29 side. . Further, the positioning hole 36 may be formed or coated with an electrically insulating material, or both the positioning hole 36 and the positioning pin 37 may be formed or coated with an electrically insulating material. May be.

  2, 4, and 5, the coupling unit 35 includes a coupling 35 a that is fixed to the right end portion of the photoconductor shaft 28 b, and a photoconductor drive shaft on the side facing the photoconductor shaft 28 b. 29, the left end portion includes a coupling 35b that can move (slide) in the axial direction of the photosensitive member drive shaft 29 and can selectively engage with the coupling 35a. At least one of the coupling 35a and the coupling 35b is formed or coated with an electrically insulating material. The coupling 35b is urged in a direction to engage with the coupling 35a by a compression spring 38 wound around the photosensitive member drive shaft 29 between the plain bearing 33 and the coupling 35b shown in FIG. In FIG. 6, the attachment / shape of the coupling part 35 is omitted.

  As described above, when the face plate unit 27 occupies the mounting position, the positioning pin 37 is lightly press-fitted (inserted without play) into the positioning hole 36, so that the photosensitive member shaft 28b and the photosensitive member driving shaft 29 are aligned. Can be accurately performed, and the coupling 35a and the coupling 35b are engaged with each other against the urging force of the compression spring 38, so that the photosensitive member drive shaft 29 side is independent of the function of the shaft alignment. The rotational driving force from is transmitted. In addition, at this time, the photoconductor shaft 28b, the photoconductor drive shaft 29, the coupling 35a, and the coupling 35b are electrically insulated from each other. This is effective in the case of controlling the charging potential of a photoreceptor that needs to be electrically insulated.

As described above, in this embodiment, for example, the coupling (B) and the coupling (36) shown in FIG. 2 and FIG. 3 of Japanese Patent Laid-Open No. 2001-147618 (Patent Document 3) and described in the paragraph “0050”. Compared with the combination of the two, the transmission function of the rotational driving force by the coupling portion and the function of the alignment of the photosensitive member shaft 28b and the photosensitive member driving shaft 29 are separated and independent. ) and with the release member for releasing the engagement between the coupling (36) becomes unnecessary, the axis alignment accuracy is also further improved, Ru der which a marked effect of above and below.

The embodiment shown in FIG. 7 will be described in comparison with the comparative example shown in FIG.
The embodiment shown in FIG. 7 basically uses the rotary drive device 25 in the printer 1 of the present embodiment shown in FIGS. 1 to 6, and has the following specifications and constant test conditions. The integrated values of the angular velocities when the axes of 28a and 28b and the photosensitive member driving shaft 29 are aligned are obtained and compared between the photosensitive member shaft 28b side and the photosensitive member driving shaft 29 side.
The comparative example shown in FIG. 8 basically uses the rotary drive device 70 in the conventional printer shown in FIGS. 9 and 10, and is under the test conditions that differ from the above-described embodiment only in the following specifications. , 28b and the photosensitive member drive shaft 29 are obtained by comparing the integrated values of the angular velocities when the axial centers of the photosensitive member drive shaft 29 and the photosensitive member drive shaft 29 are not aligned.

  In both graphs of FIGS. 7 and 8, time (second: sec) is taken on the horizontal axis, and amplitude (mm) is taken on the vertical axis. The moving distance is calculated by integrating the respective speeds (circumferential speeds) of the photosensitive member shaft 28b and the photosensitive member driving shaft 29, and the amplitude is an integral value of the moving distance and the actual speed when the speed is assumed to be constant. The difference was obtained. As can be seen from both figures, it can be easily understood that the larger the speed fluctuation, the larger the amplitude at that time.

(Example specifications)
Ball bearing 31, ball bearing 32 and ball bearing 34: JIS 0 grade sliding bearing: minimum clearance of 0.01 to 0.1 mm
Axial misalignment between positioning hole 36 and positioning pin 37: within 0.01 mm (no play)
Tolerance at the center of the hole of the apparatus body 26 into which the ball bearing 31 and the ball bearing 34 are lightly press-fitted: 0.5 mm
Tolerance of holder 40: 0.05 mm

(Specification specifications)
Ball bearing 31, ball bearing 32, ball bearing 73 and ball bearing 34: JIS 0 grade Tolerance at the center of the hole in the apparatus body 26 into which the ball bearing 31 and the ball bearing 34 are lightly press-fitted: 0.5 mm
Tolerance of holder 40: 0.05 mm

According to the present embodiment and example, the ball bearing 31 (first bearing) is positioned with respect to the apparatus main body 26 via the face plate unit 27, and the ball bearing 34 (via the side plate bracket 26b and the main body side plate 26a). The fourth bearing) is positioned with respect to the apparatus main body 26, and the ball bearing 32 (second bearing) and the slide bearing 33 (third bearing) are placed via a holder 40 that is easy to mount on the ball bearing 32. Positioning with respect to the apparatus main body 26, and the bearing of the photosensitive member driving shaft 29 on the side facing the photosensitive member shaft 28b is separate from the slide bearing 33 and the coupling portion 35 having the predetermined gap (backlash). By using the positioning means for the body, the alignment of the axis is performed by the axes of the photosensitive member shaft 28b and the photosensitive member driving shaft 29 opposed to the photosensitive member shaft 28b. Therefore, in this bearing positioning configuration, the position of the photosensitive member drive shaft 29 on the photosensitive member shaft 28b side is not determined by the slide bearing 33, and therefore, the accumulation of tolerances at the ball bearing 32 and the slide bearing 33 is extremely small and can be ignored (tolerance is small). The positioning is performed by positioning the photoconductor shaft 28a through the ball bearing 31 with respect to the apparatus main body 26, the positioning hole 36 of the photoconductor shaft 28b, and the positioning pin lightly press-fitted into the photoconductor drive shaft 29. 37, the accuracy of the alignment with the axis 37, and the tolerance of the three positioning holes of the photosensitive member drive shaft 29 with respect to the apparatus main body 26 are accumulated, so that the constituent elements are compared with the conventional example shown in FIGS. The accumulation of tolerances (components, etc.) is reduced, and the shaft cores of the photoconductor shafts 28a and 28b and the photoconductor drive shaft 29 can be aligned with high accuracy. By making it possible to suppress an increase in the angular speed variation of the coupling portion 35 due to the deviation, it is possible to reduce the color shift.
In addition, since the margin of the bearing positioning portion of the apparatus main body 26 is more generous than before, it is advantageous in terms of cost and molding technology.

  In other words, in this embodiment, since the axial misalignment between the positioning hole 36 and the positioning pin 37 is set within 0.01 mm, even if the ball bearing 31 and the ball bearing 34 are lightly press-fitted, Tolerance between the centers of the holes: Even when the maximum value side is 0.5 mm, the photoconductor shafts 28a and 28b and the photoconductor drive shaft 29 are kept coaxial, and the photoconductor shafts 28a and 28b and the photoconductor drive shaft are maintained. Therefore, the axes of the photosensitive member shafts 28a and 28b and the photosensitive member driving shaft 29 can be aligned with high accuracy. On the other hand, in the comparative example, when the ball bearing 31 and the ball bearing 34 are lightly press-fitted, the center tolerance between the holes of the apparatus main body 26 is 0.5 mm, and the holder 40 and the ball bearing 32, Since the tolerance of the holder 40 and the ball bearing 73 is 0.05 mm, the coaxiality between the photoreceptor shafts 28a and 28b and the photoreceptor drive shaft 29 is not maintained, and the photoreceptor shafts 28a and 28b and the photoreceptor drive shaft are not maintained. Therefore, the axis of the photoconductor shafts 28a and 28b and the photoconductor drive shaft 29 cannot be aligned with high accuracy.

  Since fluctuations in the angular velocity of the photoconductor 10 may be a major cause of color misregistration in slip transfer, preventing an increase in angular velocity fluctuation is effective in reducing color misregistration. Here, slip transfer refers to an optical system, a photoconductor as an image carrier, paper (sheet-like recording medium: recording paper, transfer paper, etc.), intermediate transfer belt, roll, transfer in an image forming process in an electrophotographic system. It means a phenomenon in which an image is transferred while slipping due to a geometric factor of a component related to image formation, such as a drum, and a dynamic factor accompanying each movement / rotation variation.

According to the present embodiment and examples, the following advantages and effects can be obtained in addition to the above basic advantages and effects.
The ball bearing 32 and the slide bearing 33 are positioned and fixed with respect to the resin holder 40 fixed on the apparatus main body 26 side, so that the ball bearing 32 and the slide bearing 33 are easily mounted.
By using ball bearings as the first, second, and fourth bearings, the cost can be reduced compared to the case of using, for example, a cylindrical bearing as a rolling bearing.
Positioning means separate from the coupling portion 35 is located at the center of the left end of the photosensitive member driving shaft 29 on the side facing the photosensitive shaft 28b and the positioning hole 36 formed at the center of the right end of the photosensitive member shaft 28b. The shaft centering is performed by the simplest positioning means by comprising a positioning pin 37 as a rod-like portion that is press-fitted and fixed and fits into the positioning hole 36 without play when the face plate unit 27 occupies the mounting position. Can be configured at low cost.

  In the above-described embodiments, examples, and the like, the drum-shaped photosensitive member 10 as the image bearing member has been described as a rotating member. However, the rotating member is not limited to this, and for example, the intermediate shown in FIG. 1 of the present embodiment. As shown in FIG. 1 and FIG. 2 of at least one of the rollers 4, 5 and 6 for driving an intermediate transfer belt 7a as an intermediate transfer member in the transfer unit 7, and Japanese Patent Application Laid-Open No. 2004-139031. The present invention can also be applied to at least one rotational drive device among rollers (12, 13, 14) for driving an intermediate transfer belt (8) as an intermediate transfer member in the intermediate transfer unit (15). Further, for example, conveyance as a conveyance transfer means that carries and conveys transfer paper (P) as a transfer material, which is arranged to face the photoreceptor shown in FIGS. 1 to 3 of Japanese Patent Laid-Open No. 11-95565. The present invention can also be applied to a rotation driving device of the transfer belt (9) or a transfer drum (8) which is a recording material carrier shown in FIGS. 1 and 4 of JP-A-9-15993, for example.

  As described above, the present invention has been described with respect to specific embodiments and examples. However, the technical scope disclosed by the present invention is limited to those exemplified in the above-described embodiments and examples. However, those skilled in the art can configure various embodiments, modifications, and examples according to the necessity and application within the scope of the present invention. it is obvious.

1 is a side view of an entire printer showing an embodiment of the present invention. FIG. 2 is a front view of a rotation driving device provided in the printer of FIG. 1. It is a front view which expands and shows the principal part of the rotational drive apparatus of FIG. FIG. 4 is a schematic cross-sectional front view of a rotary drive device equivalent to the rotary drive device of FIGS. 2 and 3. FIG. 4 is a schematic cross-sectional front view equivalent to the rotation drive device of FIGS. 2 and 3 and is a view when the face plate unit in the image forming unit is detached from the apparatus main body. It is a perspective view of the principal part which shows the positioning means arrange | positioned at the rotational drive apparatus of FIG. 2 and FIG. (A) is on the photosensitive member drive shaft side, (b) is on the photosensitive member shaft side, and the integrated value (time− It is a graph showing (amplitude). (A) is on the photosensitive member drive shaft side, (b) is on the photosensitive member shaft side, and the integrated value (time−) when the axial center of the photosensitive member shaft and the photosensitive member drive shaft of the rotation driving device in the comparative example is not aligned. It is a graph showing (amplitude). FIG. 10 is a front view of a rotation driving device disposed in a conventional image forming apparatus (printer). FIG. 10 is a schematic cross-sectional front view of a rotary drive device equivalent to the rotary drive device of FIG. 9.

Explanation of symbols

1 Printer (image forming device)
10 photoconductor 25 rotary drive 26 device main body 26a main body side plate 26b side plate bracket 28a photoconductor shaft (other shaft of the photosensitive member)
28b Photosensitive member axis (one axis of the photosensitive member )
29 Photoconductor drive shaft (drive shaft)
31 Ball bearing (first bearing, rolling bearing)
32 Ball bearing (second bearing, rolling bearing)
33 Slide bearing (third bearing)
34 Ball bearing (fourth bearing, rolling bearing)
35 Coupling part 36 Positioning hole (positioning means)
37 positioning pins (positioning hand stage)
40 Holder (support member)

Claims (3)

One shaft of the photoconductor is configured to be detachable from a drive shaft that drives the photoconductor through a coupling. The other shaft of the photoconductor is a first bearing, and the one shaft is a second shaft. The drive shaft on the one shaft side is rotatably supported by the third bearing and the drive shaft is supported by the fourth bearing via the coupling, respectively, and the first to fourth bearings. In the image forming apparatus for aligning the axial centers of the one shaft, the other shaft, and the drive shaft by positioning and fixing to the apparatus main body,
The second bearing and the third bearing are positioned and fixed with respect to a support member fixed on the apparatus main body side,
The first bearing, the second bearing, and the fourth bearing are ball bearings , and the third bearing is between the drive shaft on the one shaft side in the direction orthogonal to the center line of the drive shaft. A plain bearing with a predetermined clearance,
A positioning means separate from the coupling for aligning the axis of the one shaft and the drive shaft on the one shaft side;
The positioning means separate from the coupling includes a positioning hole formed in the center of one of the one shaft end and the drive shaft end on the one shaft side, and the one shaft end. A face plate unit fixed to the center of either one of the drive shaft end portions on the one shaft side and configured integrally with the photosensitive member and detachable with respect to the device main body is positioned and fixed to the device main body. Ri Do and a positioning pin the positioning and fit without play into the positioning holes in the circumferential direction when accounted for mounting positions,
The positioning is performed by aligning the ball bearing portion which is the first bearing, the positioning hole formed in the one shaft end portion, and the positioning pin lightly press-fitted into the drive shaft end portion on the one shaft side. An image forming apparatus characterized in that the accuracy is determined by accumulating tolerances at three points of a ball bearing portion which is a fourth bearing with respect to the apparatus main body of the drive shaft . The image forming apparatus according to claim 1.
At least one of the positioning hole forming portion and the positioning pin is formed of an electrically insulating material . The image forming apparatus according to claim 1 or 2,
An image forming apparatus comprising a plurality of the photoconductors and capable of forming a color image .

Images