JP2005241946A - Image forming apparatus and driving transmitting joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which stress is not given to a holding part even when the shaft centers of input/output shafts are deviated and rotation transmitting accuracy between the input/output shafts is secured even when material having high strength is not used, and to provide a driving transmitting joint. <P>SOLUTION: A color printer 1 has a main body 2 and a photoreceptor unit 30 which can be attached to/detached from the main body 2. The main body 2 has a gear 43 and a joint 45 receiving rotational driving force for the unit 30, and the unit 30 has a coupling 36 receiving the rotational driving force from the main body 2. Furthermore, abutting holes 47 and 36a are formed on the joint bearing part 43a of the gear 43 and the coupling 36, and both ends of the joint 45 are inserted in the holes 47 and 36a. The holes 47 and 36a are constituted in the shape of an untwisted triangular pole and the joint 45 is constituted in the shape of a twisted triangular pole. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a printer or a copier, and a drive transmission joint used therefor. More specifically, the present invention relates to an image forming apparatus in which an image forming unit including a photoconductor is detachable, and a drive transmission joint that transmits driving between the main body and the image forming unit.

  2. Description of the Related Art Conventionally, in some image forming apparatuses, a consumable part such as a photoconductor is unitized to be detachable so that it can be replaced by a user. For example, a tandem type image forming apparatus having image forming units for four colors of yellow, magenta, cyan, and black includes a total of four image forming units for each color. When such an image forming unit is mounted on the image forming apparatus main body, at least the photosensitive drum needs to be driven to rotate. Therefore, the photosensitive drum is connected to a drive source provided in the image forming apparatus main body so that power can be transmitted.

Various configurations of the connecting portion have been conventionally proposed (see, for example, Patent Document 1 and Patent Document 2). In the image forming apparatus described in Patent Document 1, each of the drive gear and the photosensitive drum has a separate coupling shaft, and a twisted polygonal column hole and a twisted polygonal column protrusion are connected to each of the connecting portions. Is formed. When the holes and the protrusions are fitted to each other and driven to rotate, a force to be screwed into each other works and alignment is performed. Moreover, in the coupling structure described in Patent Document 2, a plurality of convex portions are provided at the end portions of the universal joint incorporated in the gear, and are fitted by the convex portions.
JP 2000-214646 A USP 6397029

  However, in the above-described image forming apparatus of Patent Document 1, at the time of driving transmission, the input and output shafts are attracted so as to be aligned like screws. For this reason, there is a problem that stress may be applied to a member that holds the input / output shaft, a housing of the image forming apparatus, and the like, which may cause distortion. In order to cope with this point, it is necessary to devise such that the input / output shaft is precisely formed so that the misalignment is small, or the holding portion or the like is configured to allow distortion. Providing a structure that allows distortion causes an increase in the size and cost of the apparatus, and there is a problem that it is difficult to attach and detach the image forming unit if it is precisely formed. Further, in the image forming apparatus disclosed in Patent Document 2, a rotational driving force is applied to the convex portion provided at the end of the universal joint. Therefore, it is necessary to form the universal joint itself with a material having high strength. There was a problem.

  The present invention has been made to solve the problems of the above-described conventional image forming apparatus and the drive transmission joint used therein. In other words, the problem is that even if the axis of the input / output shaft is misaligned, the holding part is not stressed, and the rotation transmission accuracy between the input / output shafts is ensured without using a strong material. Another object of the present invention is to provide an image forming apparatus and a drive transmission joint that can be used.

  The image forming apparatus of the present invention, which has been made for the purpose of solving this problem, is an image forming apparatus that forms an image by mounting a detachable photosensitive unit, and is a first that receives a rotational driving force to the photosensitive unit. A drive transmission member; and an intermediate drive transmission member positioned between the first drive transmission member and the photosensitive unit and receiving a rotational driving force from the first drive transmission member. A recess is formed on one side of the member, and the other has an end located in the recess, the end has three ridges on the side, and the recess has three sides on the side. There are abutting portions that abut the ridges at a number of integral multiples, and the ridges and the abutting portions have different torsion angles, and a rotational driving force is applied from the intermediate drive transmission member to the photosensitive unit. To communicate.

  According to the image forming apparatus of the present invention, the rotational driving force to the photosensitive unit is transmitted to the removable photosensitive unit via the first drive transmission member and the intermediate drive transmission member. Here, the drive transmission between the first drive transmission member and the intermediate drive transmission member is due to the three ridges of the other end being in contact with the contact portion of one recess. Furthermore, since the ridge portion and the contact portion have different twist angles, these contact portions are three points, one on each ridge portion. In the three-point contact, the centers of the three contact points coincide with the centers of the ridge and the contact portion, so that the rotation centers of the first drive transmission member and the intermediate drive transmission member coincide with each other at that position. The On the other hand, even if the shaft core of the first drive transmission member and the shaft core of the intermediate drive transmission member are inclined with respect to each other, there is no effect on contact or drive transmission at three points. Accordingly, the deviation between the shaft core of the first drive transmission member and the shaft core of the intermediate drive transmission member when the photosensitive unit is mounted is absorbed by the inclination of the shaft core, so that stress is applied to those holding portions. It will never be done. Thereby, even if the shaft center of the input / output shaft is shifted, no stress is applied to the holding portion, and the rotation transmission accuracy between the input / output shafts can be ensured without using a material having high strength.

  Here, different twist angles may be, for example, that one side is not twisted and the other side is twisted. In this case, the ridge portion or the contact portion may be twisted. Alternatively, both of them may be twisted and their twist angles or twist directions may be different.

Furthermore, in the present invention, it is desirable that the diameter of the end portion is smaller than the maximum diameter of the concave portion and larger than the minimum diameter, and the contact member is disposed in the contact portion.
In this way, it is easy to insert the end portion into the recess. Furthermore, if a contact member is arranged at the contact portion, the pressure contact force against the contact point is received by the contact member, so that the influence of the deformation of the recess or the like is prevented.

Furthermore, in the present invention, the first drive transmission member and the intermediate drive transmission member have an elastic member that urges the first drive transmission member and the intermediate drive transmission member to be separated from each other, and the concave portion is provided with a protruding portion that protrudes inward from the side portion. It is desirable that the end portion is provided with a retaining portion that comes into contact with the protruding portion from the back side.
In this way, when the drive transmission is not performed, the first drive transmission member and the intermediate drive transmission member are separated from each other, so that the image forming unit can be easily attached and detached. Furthermore, when they are separated from each other, the projecting portion and the retaining portion come into contact with each other, so that the intermediate drive transmission member does not fall off.

  An image forming apparatus according to the present invention is an image forming apparatus that includes a main body and a photosensitive unit that can be attached to and detached from the main body, and performs image formation by attaching the photosensitive unit to the main body. A first drive transmission member that receives a rotational driving force to the body unit, and the photosensitive unit has a second drive transmission member that receives a rotational driving force from the main body. An intermediate drive transmission member located between the first drive transmission member and the second drive transmission member; a drive transmission location between the first drive transmission member and the intermediate drive transmission member; an intermediate drive transmission member; The drive transmission location between the drive transmission member and the drive transmission member is formed with a recess on one side, and the other has an end located in the recess, and the end has three ridges on the side. The recesses are in contact with the ridges at an integral multiple of 3 on the side. It has a section, and the ridge portion and the contact portion may be one which is a structure having a different helix angle from each other.

  According to the image forming apparatus of the present invention, the rotational driving force is transmitted from the first drive transmission member to the second drive transmission member via the intermediate drive transmission member. At this time, the drive transmission between them is due to the abutment at the three points of the ridge portion and the abutment portion on either side. Accordingly, when the photosensitive unit is mounted, the displacement between the axis of the first drive transmission member and the axis of the intermediate drive transmission member, or the axis of the intermediate drive transmission member and the axis of the second drive transmission member Any deviation is absorbed by the inclination of the axis. Thereby, even if the shaft center of the input / output shaft is shifted, no stress is applied to the holding portion, and the rotation transmission accuracy between the input / output shafts can be ensured without using a material having high strength.

Further, in the present invention, the intermediate drive transmission member has end portions at both ends, the first drive transmission member and the second drive transmission member both have a concave portion, and the concave portion of the first drive transmission member includes a side portion. The intermediate drive transmission member is provided with a retaining portion that comes into contact with the projection from the rear side, and the first drive transmission member and the intermediate drive transmission member are connected to each other. It is desirable to have elastic members that are biased in the direction of being separated from each other.
In this way, the photosensitive unit can be easily attached and detached, and the intermediate drive transmission member does not fall off.

  The present invention also provides a drive transmission joint for transmitting rotational drive from the first drive transmission member to the second drive transmission member, and an intermediate drive transmission located between the first drive transmission member and the second drive transmission member. A drive transmission location between the first drive transmission member and the intermediate drive transmission member and a drive transmission location between the intermediate drive transmission member and the second drive transmission member, and a recess formed on one side And the other has an end located in the recess, the end has three ridges on the side, and the recess has an integral multiple of 3 on the side, The present invention also includes a drive transmission joint that has a contact portion that contacts the ridge portion, and the ridge portion and the contact portion have different twist angles.

  According to the image forming apparatus and the drive transmission joint of the present invention, no stress is applied to the holding portion even if the shaft center of the input / output shaft is displaced, and there is no need to use a strong material between the input / output shafts. The rotation transmission accuracy can be ensured.

"First form"
Hereinafter, a first embodiment of the present invention will be described in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to a tandem type color printer.

  In the color printer 1 of the present invention, as shown in FIG. 1, the image forming units 10Y, 10M, 10C, and 10K for each color are arranged along the intermediate transfer belt 11. A paper cassette 12 is attached to the lower part of the color printer 1, and the paper in the paper cassette 12 is conveyed to the paper feeding / conveying section 14 by the paper feeding roller 13. The images formed by being superimposed on the intermediate transfer belt 11 by the image forming units 10Y, 10M, 10C, and 10K for the respective colors are transferred to a sheet by the secondary transfer unit 15 and fixed by the fixing unit 16. The sheet on which the image is formed in this manner is discharged by the discharge roller 17. All of these configurations are housed in the housing 20.

  The image forming units 10Y, 10M, 10C, and 10K for the respective colors have the same configuration, and each includes a photoreceptor 21, a developing unit 22, an exposure unit 23, a charging unit 24, a cleaner unit 25, and a transfer unit 26. ing. Since the configuration and operation of each part of the image forming units 10Y, 10M, 10C, and 10K are general, a description thereof is omitted here. Among the image forming units 10Y, 10M, 10C, and 10K, a predetermined portion including at least the photosensitive member 21 is unitized to form an image forming unit 30. The image forming unit 30 is detachable from the housing 20 of the color printer 1. Hereinafter, a portion of the color printer 1 excluding the image forming unit 30 is referred to as a main body 2.

  A door that can be opened and closed is provided on the front side of the color printer 1 in FIG. By opening this door, the front end of each image forming unit 30 is exposed. The user can remove the image forming unit 30 from the main body 2 by grasping the exposed end and pulling it toward the front side in the figure. Further, the image forming unit 30 can be attached again by inserting the image forming unit 30 into the space where the image forming unit 30 of the main body 2 has been removed and pushing it inward in the drawing. When the door is closed after the attachment, the front end of the image forming unit 30 is held and fixed by the inner surface of the door.

  Next, an outline of a connecting portion between the main body 2 and the image forming unit 30 is shown in FIGS. This connecting portion is arranged on the back side of the color printer 1 in FIG. FIG. 2 is a cross-sectional view of this connecting portion. Here, FIG. 3 is a perspective view of the right half of FIG. 2 in a connected state, and FIG. 4 is an exploded perspective view of the same.

  The image forming unit 30 includes a photoreceptor 21 and is a part that can be attached to and detached from the main body 2. In the image forming unit 30, as shown on the left side in FIG. 2, a flange 32 is fixed to the end portion of the photosensitive member 21, and a rotating shaft 34 of the photosensitive member 21 is fixed to the flange 32. Further, a coupling 36 is attached to one end of the rotating shaft 34. Since the coupling 36, the rotating shaft 34, the flange 32, and the photosensitive member 21 are all fixed to each other, they rotate together when receiving the rotational driving force of the main body 2.

  On the main body 2 side, as shown on the right side in FIG. 2, a gear 43 is fixed to the housing 20 via a gear bearing 44. The gear 43 is provided with a joint receiving portion 43a extending in the left direction in the figure. The joint receiving portion 43a has a substantially cylindrical shape, and a contact hole 47 into which the joint 45 and the spring 46 are inserted is formed therein. A ring 48 is attached to the left end of the joint receiving portion 43a. The ring 48 is formed with three fixed legs 48a and retaining portions 48b protruding in the inner circumferential direction. These gear 43, gear bearing 44, joint 45, and ring 48 are all made of resin. The fixing leg 48a of the ring 48 is snap-fitted into a fixing hole 43b formed in the joint receiving portion 43a using the flexibility of the resin.

  Here, the gear 43 transmits a driving force by a power unit provided inside the main body 2 to the joint 45. As will be described in detail later, the contact hole 47 of the joint receiving portion 43a and the joint 45 are partially in contact to transmit rotation. The gear bearing 44 is fixed to the housing 20 and rotatably supports the gear 43. The spring 46 is compressed by the image forming unit 30 being attached to the main body 2 and biases the joint 45 to the left in FIG.

  Next, the shape of the joint 45 will be described. As shown in FIG. 4, the joint 45 includes a twisted triangular prism main body 45 a. In the joint 45, a hemispherical tip 45b is formed at the center on the front side in FIG. 4, and a side convex portion 45d is formed on each side surface. The joint 45 is integrally formed of a resin such as polyacetal (POM) or polycarbonate (PC). Further, as shown in FIG. 5, a meat steal may be formed on the joint 45.

  2 and 3, when the image forming unit 30 is attached to the main body 2, the coupling 36 of the image forming unit 30 and the joint receiving portion 43a of the gear 43 are in contact with each other. Yes. On the joint 45 side of these members, a non-twisted triangular prism-shaped contact hole 36a and a contact hole 47 are formed. For example, when the coupling 36 is viewed from the right side in FIG. 2, a contact hole 36a having a complicated shape as shown in FIG. 6 is formed. Of these, the three abutting surfaces 36b are important, and these abutting surfaces 36b form triangular prism-shaped holes that are not twisted. Similarly, contact holes 47 having three contact surfaces are provided on the inner surface of the joint receiving portion 43a to form a triangular prism-shaped hole that is not twisted.

  Next, transmission of rotational driving force by the joint 45 and the contact hole 36a will be described. For the sake of explanation, the rotation transmitting portion by the coupling 36 having the non-twisted triangular prism-shaped contact hole 36a and the twisted triangular prism-shaped joint 45 is taken out and shown in FIGS. In order to simplify the explanation, in these drawings, the contact hole 36a is described as a shape having only the contact surface 36b. As shown in these drawings, two or more of the three ridge lines p of the joint 45 are connected to the inner surface of the contact hole 36a regardless of the positional relationship between the axis of the joint 45 and the axis of the coupling 36. It will never be parallel. Therefore, the relative rotation between the joint 45 and the coupling 36 causes each ridge line p of the joint 45 to abut only at one point on each of the three inner surfaces of the abutting hole 36a. That is, the joint 45 and the contact hole 36a are fitted at three points with respect to driving in the rotational direction, and the rotational driving force is transmitted.

  Here, the relationship between the diameter of the joint 45 and the diameter of the contact hole 36a is set in the following range. The backlash, which is the difference between the diameter of the contact hole 36a and the diameter of the joint 45, is set to be smaller than the backlash that the joint 45 idles inside the contact hole 36a. That is, the diameter of the joint 45 is larger than the minimum diameter of the contact hole 36a. In addition, when the axial center of the joint 45 and the contact hole 36a becomes the maximum eccentric declination allowed by the apparatus, the setting is set to be larger than the amount of play that allows the joint 45 to be inserted into the contact hole 36a. Is done. That is, the diameter of the joint 45 is smaller than the maximum diameter of the contact hole 36a. By setting in this way, the joint 45 can be easily inserted into the contact hole 36a. Further, it is more preferable that each ridge line p of the joint 45 is given R in order to improve the insertion and fitting state of the joint 45 and the contact hole 36a.

  Thus, since the insertion of the joint 45 into the contact hole 36a is easy, the insertion of the image forming unit 30 into the main body 2 in the axial direction is also easy. In the stage immediately after the insertion, the shaft centers of the joint 45 and the coupling 36 may not coincide at all. Thereafter, the joint 45 and the contact hole 36a are relatively rotated, so that they come into contact at three points as described above. At this time, the axial centers of the coupling 36 and the joint 45 are overlapped at the same position at the cross-sectional position by the three contact points.

  On the other hand, contact at three points is possible even if the inclinations of the two axes are slightly different. Accordingly, the deviation between the axis of the coupling 36 and the axis of the joint 45 is absorbed by the inclination of the joint 45 due to the rotation after insertion. Further, they are securely fitted by the three contact points while the axis of each other remains inclined. This occurs in the same manner on both the coupling 36 side of the image forming unit 30 and the joint receiving portion 43 a side formed on the gear 43 of the main body 2 with respect to both ends of the joint 45.

Next, it will be described that the rotation is transmitted with high accuracy even when the shaft cores are fitted while the shafts are inclined. An outline of the rotation state of the gear 43 and the coupling 36 connected by the inclined joint 45 is shown in FIG. First, when the angular velocity of the gear 43 is ω0 and the reference radius is r0, the linear velocity Vd1 (t) at the reference radius position of the gear 43 is given by the following equation (1).
Vd1 (t) = r0 * ω0 (1)

Further, the gear 43 and the joint 45 have the same linear velocity at the contact point. Therefore, when the rotational radius of the joint 45 corresponding to the reference radius r0 in the fitted state at that time is r1 (t), the angular velocity ω1 (t) of the joint 45 is given by the following equation (2).
ω1 (t) = Vd1 (t) / r1 (t) (2)
Further, substituting the right side of equation (1) into Vd1 (t) of equation (2) yields the following equation (3).
ω1 (t) = r0 * ω0 / r1 (t) (3)

On the other hand, also on the coupling 36 side, the angular velocity of the joint 45 is ω1 (t), and the linear velocity of the joint 45 and the coupling 36 is equal at the contact point. Therefore, the linear velocity Vd2 (t) of the coupling 36 at the position of the rotation radius r1 (t) of the joint 45 is given by the following equation (4).
Vd2 (t) = r1 (t) * ω1 (t) (4)
Substituting the right side of the equation (3) into ω1 (t) in the above gives the following equation (5).
Vd2 (t) = r1 (t) * r0 * ω0 / r1 (t)
= R0 * ω0 (5)

On the other hand, the angular velocity ω2 (t) of the coupling 36 is given by the following equation (6) because the rotational radius of the coupling 36 at the contact point between the coupling 36 and the joint 45 is r0.
Vd2 (t) = r0 * ω2 (t) (6)
Therefore, the following equation (7) is obtained from the equations (5) and (6).
ω2 (t) = ω0 (7)

  From this, it can be seen that the rotational angular velocity of the coupling 36 is equal to the rotational angular velocity of the gear 43 and is a steady rotation. Therefore, according to the joint 45, even if the shafts of the joint 45 and the coupling 36 are not aligned with each other, the joint 45 is fitted as it is and the drive transmission in the rotational direction is reliably performed.

  Further, the coupling 36 may be formed as shown in FIG. For example, a meat steal may be formed around the bottom of the contact hole 36a. Further, since the ridge line p of the joint 45 abuts on the abutting surface 36b, a protective material 36c having a high strength may be attached to protect the abutting surface 36b. In particular, since the gear 43 is formed of a material with good slip, the contact surface of the contact hole 47 of the joint receiving portion 43a may be scraped by the pressure contact of the joint 45. Therefore, the protective material 36c may be attached to the inner surface of the joint receiving portion 43a. For example, a metal plate or the like is suitable as the protective material 36c.

  With this configuration, the connecting portion between the joint 45 and the coupling 36 is only fitted in the rotational direction, and is free for movement in the axial direction. Therefore, the user can easily attach and detach the image forming unit 30 by moving it in the axial direction. When the image forming unit 30 is detached from the main body 2, the pressure contact force in the right direction in the figure to the joint 45 by the coupling 36 from the state shown in FIG. 2 is lost. Therefore, the joint 45 projects leftward in the figure by the urging force of the spring 46. At this time, the side protrusion 45d of the joint 45 abuts against the retaining portion 48b of the ring 48, so the joint 45 does not fall off.

  As described above in detail, according to the color printer 1 of the present embodiment, the connecting portion between the image forming unit 30 and the main body 2 has a twisted triangular prism-shaped joint 45 and non-twisted triangular prism-shaped contact holes 36a, 47. And using. Since these abut at three points by the driving force in the rotation direction, the axial center positions coincide with each other at the abutting position. On the other hand, since there are only three contact points, the tilt of the rotation axis is allowed to some extent. Therefore, the rotation of the shaft is kept precisely while maintaining the rotation speed. Thereby, even if the shaft center of the input / output shaft is shifted, no stress is applied to the holding portion, and the rotation transmission accuracy between the input / output shafts can be ensured without using a material having high strength.

"Second form"
Hereinafter, a second embodiment of the present invention will be described in detail with reference to the accompanying drawings. This embodiment is different from the first embodiment only in the connection portion between the image forming unit 30 and the main body 2. Since the overall configuration and the like are almost the same, only different parts will be described here.

FIG. 11 shows a schematic configuration of the connecting portion of this embodiment. In this figure, the image forming unit 30 is shown on the right side in the figure.
The image forming unit 30 is held by a housing 31 and includes a photosensitive member 21, a flange 32, and a bearing 33 from the right in the drawing. The flange 32 is fixed to the end of the photoconductor 21 and rotates integrally with the photoconductor 21. The bearing 33 is fixed to the housing 31 by rotatably supporting the end portion of the flange 32. A cylindrical fixing portion 33a is formed at the left end of the bearing 33 in the drawing.

  On the main body 2 side, as shown on the left side in FIG. 11, a gear 43, a gear bearing 44, a joint 45, and a spring 46 are attached to frames 41 and 42 fixed to the housing 20. The gear 43 transmits a driving force by a power unit provided inside the main body 2 to the joint 45. The gear 43 is formed with a joint receiving portion 43a extending rightward in the drawing. The gear bearing 44 is fixed to the frame 42 and rotatably supports the joint receiving portion 43a of the gear 43. A cylindrical fixing portion 44 a is formed at the right end portion of the gear bearing 44 in the drawing. Further, a retaining portion 44 b protruding in the inner circumferential direction is formed on the inner circumferential side of the central portion of the gear bearing 44.

  Further, as shown in FIG. 12, the joint 45 has a twisted triangular prism main body 45a. The right end portion in the figure is a twisted triangular pyramidal tip portion 45b, and the left end portion in the figure is formed with a cylindrical convex portion 45c into which the spring 46 is fitted. Further, on the three surfaces of the main body 45a, side convex portions 45d are formed closer to the cylindrical convex portion 45c than the center. The tip side of the side protrusion 45d is formed in a taper shape.

  Further, as shown in FIG. 11, a spring 46 is disposed between the gear 43 and the joint 45. As a result, the joint 45 is biased in the right direction in the figure. In this embodiment, a non-twisted triangular prism-shaped contact hole 47 is formed in each of the joint receiving portion 43 a of the gear 43 and the flange 32 of the image forming unit 30. When the image forming unit 30 is attached, the joint 45 abuts both the joint receiving portion 43a and the flange 32 at three points. Accordingly, the rotational driving force of the gear 43 is transmitted to the photosensitive member 21 by the joint 45.

  Further, in the connection portion of this embodiment, the inner peripheral diameter of the fixing portion 44a of the gear bearing 44 and the outer peripheral diameter of the fixing portion 33a of the bearing 33 of the image forming unit 30 are formed to be substantially equal. Since the fixing portion 33a and the fixing portion 44a are disposed so as to face each other, when the image forming unit 30 is attached to the main body 2, as shown in FIG. The fixing portion 33a is inserted and fitted. Accordingly, the fixing portion 44a and the fixing portion 33a, and thus the gear bearing 44 and the bearing 33, are directly fixed to each other. Here, the gear bearing 44 is fixed to the frame 42 of the main body 2. On the other hand, the bearing 33 is fixed to the housing 31 of the image forming unit 30. Accordingly, the image forming unit 30 is positioned and fixed with respect to the main body 2 by this fitting.

  As described in detail above, even with a color printer having a connecting portion of this embodiment, similarly to the color printer 1 of the first embodiment, the holding portion is stressed even if the axis of the input / output shaft is displaced. Therefore, the rotation transmission accuracy between the input and output shafts can be ensured without using a material with high strength.

Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.
For example, in each of the above embodiments, the joint 45 has a substantially triangular prism shape, and the contact holes 47 and 36a are provided in the joint receiving portion 43a and the coupling 36 into which the joint is inserted. Alternatively, the joint receiving portion 43a and the coupling 36 may be provided with a substantially triangular prism-shaped convex portion and connected by joints having contact holes at both ends. Or you may make it have a contact hole and a convex part in the both ends of a joint, respectively.

  Further, for example, in each of the above embodiments, the joint 45 is twisted and the contact holes 36a and 47 are not twisted, but the same effect can be obtained even if they are reversed. FIGS. 13A and 13B are a side view and a front view simply showing a fitting state of a joint 51 having a twisted triangular prism joint 51 and a twisted triangular prism hole 52. 14 is an AA cross section of FIG. 13, and FIG. 15 is a BB cross section of FIG. Even in this case, each ridge line of the joint 51 abuts on the inner surface of the hole 52 at one point. Therefore, even if the shaft centers of the joint 51 and the hole 52 do not match, the rotational driving force is transmitted as it is fitted. Alternatively, the joint and the hole may be twisted, and their twist angles may be different.

  Further, for example, the joint 45 in each of the above forms may be a composite joint 55 in which a plurality of members are connected as shown in FIG. The central portion 55a is preferably made of a material that is resistant to twisting, and is preferably made of metal or the like when formed thin. Both end portions 55b and 55c each have a twisted short triangular prism shape. In such a composite joint 55, different materials can be used for both end portions 55b and 55c, or those formed by changing the diameter and the twist angle can be used.

  Further, for example, the joint 45 of each of the above forms may be a joint 56 provided with an L-shaped protrusion 56a instead of the tip 45b as shown in FIG. In this case, a notch 57a is provided at the open end of the contact hole 36a as the coupling 57 into which the side having the projection 56a is fitted. The notch 57a is sufficiently wider than the protrusion 56a. In this way, the direction of fitting between the joint 56 and the coupling 57 is defined. Since joints and couplings are generally integrally molded with resin, the directionality during molding may appear as a property of the part. Therefore, if the joint 56 and the coupling 57 are used, the directionality of the image forming unit 30 can be prevented from changing when the image forming unit 30 is replaced.

It is sectional drawing which shows schematic structure of the color printer of a 1st form. It is sectional drawing which shows a connection part. It is a perspective view which shows a connection part. It is a disassembled perspective view which shows a connection part. It is a perspective view which shows the shape of a joint. It is a perspective view which shows a coupling. It is explanatory drawing which shows the relationship between a joint and a coupling. It is explanatory drawing which shows the relationship between a joint and a coupling. It is explanatory drawing which shows a drive transmission state. It is a perspective view which shows a coupling. It is sectional drawing which shows the connection part of the color printer of a 2nd form. It is a perspective view which shows the shape of the joint of a 2nd form. It is explanatory drawing which shows another example of a joint and a coupling. It is sectional drawing which shows another example of a joint and a coupling. It is sectional drawing which shows another example of a joint and a coupling. It is a perspective view which shows the shape of a joint. It is explanatory drawing which shows another example of a joint and a coupling.

Explanation of symbols

1 Color printer (image forming device)
2 Main body 30 Image forming unit 36 Coupling (second drive transmission member)
36a Contact hole (concave)
36c Protective material (contact member)
43 Gear (first drive transmission member)
43a Joint receiving part (concave part)
45 Joint (Intermediate drive transmission member)
45a Body (end)
45d Side convex part (preventing part)
46 Spring (elastic member)
47 Contact hole (contact part)
48b Retaining part (protruding part)
p Ridge (ridge)

Claims (6)

In an image forming apparatus for forming an image by mounting a detachable photosensitive unit,
A first drive transmission member for receiving a rotational driving force to the photosensitive unit;
An intermediate drive transmission member positioned between the first drive transmission member and the photosensitive unit and receiving a rotational driving force from the first drive transmission member;
A recess is formed in one of the first drive transmission member and the intermediate drive transmission member, and the other has an end located in the recess,
The end has three ridges on the side,
The concave portion has an abutting portion that abuts on the ridge portion at a location that is an integral multiple of 3 on the side portion,
The ridge portion and the contact portion have different twist angles,
An image forming apparatus, wherein a rotational driving force is transmitted from the intermediate drive transmitting member to the photosensitive unit. The image forming apparatus according to claim 1,
The diameter of the end is smaller than the maximum diameter of the recess and larger than the minimum diameter;
An image forming apparatus, wherein a contact member is disposed at the contact portion. The image forming apparatus according to claim 1, wherein:
An elastic member that urges the first drive transmission member and the intermediate drive transmission member in a direction away from each other;
The concave portion is provided with a protruding portion protruding inward from the side portion,
The image forming apparatus according to claim 1, wherein the end portion is provided with a retaining portion that comes into contact with the protruding portion from the back side. In an image forming apparatus having a main body and a photosensitive unit detachable from the main body, and performing image formation by attaching the photosensitive unit to the main body,
The main body has a first drive transmission member that receives a rotational driving force to the photosensitive unit,
The photosensitive unit has a second drive transmission member that receives a rotational driving force from the main body,
One of the main body and the photosensitive unit has an intermediate drive transmission member positioned between the first drive transmission member and the second drive transmission member,
Both the drive transmission location between the first drive transmission member and the intermediate drive transmission member and the drive transmission location between the intermediate drive transmission member and the second drive transmission member,
A recess is formed on one side and the other has an end located within the recess;
The end has three ridges on the side,
The concave portion has an abutting portion that abuts on the ridge portion at a location that is an integral multiple of 3 on the side portion,
The image forming apparatus, wherein the ridge portion and the contact portion have a structure having different twist angles. The image forming apparatus according to claim 4,
The intermediate drive transmission member has the ends at both ends,
The first drive transmission member and the second drive transmission member both have the recess,
The concave portion of the first drive transmission member is provided with a protruding portion that protrudes inward from the side portion,
The intermediate drive transmission member is provided with a retaining portion that comes into contact with the protruding portion from the back side,
An image forming apparatus comprising: an elastic member that urges the first drive transmission member and the intermediate drive transmission member in a direction in which the first drive transmission member and the intermediate drive transmission member are separated from each other. In a drive transmission joint for transmitting rotational drive from the first drive transmission member to the second drive transmission member,
An intermediate drive transmission member located between the first drive transmission member and the second drive transmission member;
Both the drive transmission location between the first drive transmission member and the intermediate drive transmission member and the drive transmission location between the intermediate drive transmission member and the second drive transmission member,
A recess is formed on one side and the other has an end located within the recess;
The end has three ridges on the side,
The concave portion has an abutting portion that abuts on the ridge portion at a location that is an integral multiple of 3 on the side portion,
The drive transmission joint according to claim 1, wherein the ridge portion and the contact portion have structures having different twist angles.

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