JP2006017938A - Clutch and image forming apparatus loaded with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a clutch reducing an abnormal sound produced when an input shaft and an output shaft are not connected. <P>SOLUTION: The clutch has a plate spring 77 by which a clutch body 66 is energized in a direction opposite to a rotation direction of an input gear 64 and by which, when rotation of a cam shaft 52 stops, a collar 73 is rotated in the direction opposite to the rotation direction of the input gear 64 to expand the diameter of a coil spring 76. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a clutch that transmits rotation of an input shaft to an output shaft and an image forming apparatus equipped with the clutch.

  Each time the toner image of each color is formed on the photosensitive drum, the image forming apparatus transfers the toner image onto the intermediate transfer belt, and after the overlap transfer is completed, the superimposed transfer image on the intermediate transfer belt is transferred to the image forming apparatus. There are some which are transferred onto a sheet by a transfer roller (see, for example, Patent Document 1).

  By the way, in this image forming apparatus, if the transfer roller is brought into contact with the intermediate transfer belt before the toner images of the respective colors are overlaid, the toner image on the intermediate transfer belt is scraped off by the transfer roller. For this reason, during the overlap transfer, the transfer roller is separated from the intermediate transfer belt, and the transfer roller is brought into contact with the intermediate transfer belt after the toner image overlap transfer is completed.

  The transfer roller is attached to the rotating end side of the rotating frame, and is separated from the intermediate transfer belt by the rotating frame being biased by a spring. Then, the rotation frame is rotated against the bias of the spring by the rotation of the cam, so that the transfer roller is pressed against the intermediate transfer belt.

As a method for transmitting the rotational force to the cam, a method for transmitting the rotation of the input shaft to the output shaft provided with the cam via a spring clutch is known. This spring clutch connects an input shaft and an output shaft by utilizing the winding of a coiled spring, and transmits the rotational force of the input shaft to the output shaft.
JP-A-8-190288

  However, in the conventional spring clutch, when the input shaft and the output shaft are not connected, the amount of torsion of the spring becomes insufficient for some reason, and the input shaft and the output shaft are slightly connected by the spring. That is, a half-clutch state may occur. In this case, chatter vibrations are generated due to friction between the spring and the input shaft, which may cause abnormal noise.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a clutch capable of reducing abnormal noise that occurs when the input shaft and the output shaft are not connected, and an image forming apparatus equipped with the clutch. Is to provide.

  In order to solve the above problems and achieve the object, the clutch of the present invention and the image forming apparatus equipped with the clutch are configured as follows.

(1) A clutch body that is rotatably supported within a predetermined angle range around an axial center line, an input shaft that is driven to rotate in a fixed direction around the axial center line, and rotated around the axial center line An output shaft that can be provided, a rotating body that can be rotated around the axis, and a winding direction opposite to the rotation direction of the input shaft, one end of which is fixed to the output shaft, A coil spring whose end is fixed to the rotating body and the input shaft are integrally provided, inserted into the coil spring, and tightened on the inner surface of the coil spring, thereby rotating the input shaft. A transmission section for transmitting to the output shaft and the rotating body, and first diameter expanding means for stopping the rotation of the rotating body and expanding the inner diameter of the coil spring when the output shaft and the rotating body are rotating. And input the clutch body By energizing in the opposite direction to the rotation of the output shaft, when the rotation of the output shaft stops, the rotating body is rotated in the energizing direction, and a second expansion that further expands the inner diameter of the coil spring is performed. And a diameter means.

(2) In the clutch described in (1), the second diameter expanding means is a leaf spring.

(3) An image forming apparatus having the clutch described in (1).

  ADVANTAGE OF THE INVENTION According to this invention, the abnormal sound produced when the input shaft and the output shaft are not connected can be reduced.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  First, the overall configuration of the electrophotographic copying machine will be briefly described with reference to FIGS.

  FIG. 1 is a perspective view showing an external appearance of an electrophotographic copying machine according to an embodiment of the present invention, FIG. 2 is a perspective view showing a state where a duplex printing unit 25 according to the embodiment is opened, and FIG. 1 is a schematic diagram showing an internal configuration of an electronic copying machine according to an embodiment.

  As shown in FIG. 1, the electrophotographic copying machine includes a copying machine main body 1, and a document transport unit 22 for transporting a document to a document table is provided on the upper surface thereof. A touch panel type operation panel 23 is provided in the upper part of the front surface of the copying machine main body 1. In addition, a plurality of stages of paper feed cassettes 24 are disposed at the lower part of the copying machine main body 1, and a double-sided printing unit 25 used for printing on both sides of a sheet is provided on one side.

  As shown in FIG. 2, when the duplex printing unit 25 is opened, the opening / closing cover 26 appears, and a secondary transfer unit 36 (not shown in FIG. 2) is provided on the inner surface side thereof. The secondary transfer unit 36 will be described in detail later.

  As shown in FIG. 3, a photoconductive drum 2 is rotatably provided in the copying machine main body 1.

Around the photosensitive drum 2, along the rotation direction, a charger 5 for charging the surface of the photosensitive drum 2 to a predetermined potential, a monochrome developing device 8B for developing an electrostatic latent image, and a color developer A rotary developing device 8A, an intermediate transfer belt 3 for temporarily transferring a developer image, and a cleaner 6 for removing residual toner on the photosensitive drum 2 are provided.

  The color rotary developing device 8A includes a first developing unit 8a that supplies yellow toner, a second developing unit 8b that supplies cyan toner, and a third developing unit 8c that supplies magenta toner. .

  The intermediate transfer belt 3 is stretched between the first to fourth rollers 3a to 3d with a predetermined tension, and constitutes a transfer belt unit 35 together with the first to fourth rollers 3a to 3d. The outer peripheral surface of the intermediate transfer belt 3 is pressed against the photosensitive drum 2 by the primary transfer roller 12. A cleaner 15 a for cleaning the intermediate transfer belt 3 is in contact with a portion of the intermediate transfer belt 3 that is wound around the first roller 3 a.

  Below the developing devices 8A and 8B, an exposure device 4 for forming an electrostatic latent image on the photosensitive drum 2 is provided. Below the exposure apparatus 4, the paper feed cassette 24 is provided. The paper feed cassette 24 is provided with a pickup roller 7 for taking out paper. The paper taken out by the pickup roller 7 is separated one by one by the paper feed roller 15 and the separation roller 16 and is conveyed along a conveyance path in the conveyance system 19.

  In the transport system 19, a transport roller pair 9, a registration roller pair 17, and a secondary transfer roller 11 are sequentially arranged along the paper transport direction. The registration roller pair 17 temporarily stops the conveyed sheet, corrects the inclination of the sheet with respect to the conveying direction, and makes the leading end of the sheet coincide with the leading end of the toner image on the intermediate transfer belt 3.

  A fixing device 13 for fixing the toner image transferred onto the paper is disposed on the downstream side of the secondary transfer roller 11 in the paper conveyance direction. The fixing device 13 includes a heating roller 13a and a pressure roller 13b.

  A discharge roller pair 30 for discharging the paper is provided on the downstream side of the fixing device 13 in the paper conveyance direction. On the carry-out side of the discharge roller pair 30, a discharge tray 31 that receives discharged paper is provided.

  Next, the printing operation of the electrophotographic copying machine will be briefly described.

  First, a document is set on the document transport unit 22 and the copy button on the operation panel 23 is turned on. As a result, the document is set at a predetermined position on the document table, and the design on the paper is optically read by a reading device (not shown).

  At this time, the surface of the photosensitive drum 2 is uniformly charged by the charger 5. The charged photosensitive drum 2 is irradiated with information light corresponding to the read information by the exposure device 4, whereby an electrostatic latent image is formed on the photosensitive drum 2.

  The electrostatic latent image is sent to the developing device 8B or the developing device 8A by the rotation of the photosensitive drum 2, and is developed by the toner of each color supplied from the developing devices 8A and 8B. The developed toner image is sent onto the intermediate transfer belt 3 by the rotation of the photosensitive drum 2 and is primarily transferred by the primary transfer roller 12.

  At this time, a sheet is fed from the paper feed cassette 24 between the intermediate transfer belt 3 and the secondary transfer roller 11, and the toner image on the intermediate transfer belt 3 is secondarily transferred to the sheet. When the toner image is transferred to the paper, the paper is peeled off from the intermediate transfer belt 3 and sent to the fixing device 13 where the toner image is fixed by heating and pressing. When the toner image is fixed on the sheet, the sheet is discharged to the outside through the discharge roller pair 30 and placed on the discharge tray 31.

  Note that when the toner image is transferred to the intermediate transfer belt 3, the photosensitive drum 2 is subjected to light static elimination by a static eliminator (not shown). The toner remaining on the photosensitive drum 2 is cleaned by the cleaner 6.

  Next, the secondary transfer unit 36 and its peripheral part will be described in detail with reference to FIGS.

  FIG. 4 is a perspective view showing the transfer belt unit 35 and the secondary transfer unit 36 according to the embodiment.

  As shown in FIG. 4, both ends of the opening / closing cover 26 are rotatably supported by the copying machine main body 1 via a support shaft (not shown), and a secondary transfer unit 36 is provided on the inner surface thereof. Is provided. When a sheet is jammed between the secondary transfer unit 36 and the transfer belt unit 35, the sheet can be removed by opening the opening / closing cover 26.

  5A and 5B are perspective views showing the secondary transfer unit 36 according to the embodiment from different angles, and FIG. 6 is a front view showing the secondary transfer unit 36 according to the embodiment. It is.

  As shown in FIGS. 5A and 5B and FIG. 6, support brackets 38 are respectively provided on both sides of the inner surface of the opening / closing cover 26, and the secondary transfer unit 36 is provided on these support brackets 38 via a support shaft 39. And is pivotally mounted.

  7A and 7B are perspective views showing the secondary transfer unit 36 according to the embodiment from different angles.

  As shown in FIG. 7A, the secondary transfer unit 11 is rotatably provided with the secondary transfer roller 11. The secondary transfer roller 11 includes bearing holes 41 at both ends thereof, and the support shaft 39 is inserted into the bearing holes 41 so that the secondary transfer roller 11 is rotatably supported by the support bracket 38.

  As shown in FIG. 7B, an L-shaped sheet metal 42 is provided on the upper surface of the secondary transfer unit 36 along the longitudinal direction thereof. L-shaped leaf springs 45 are provided at both ends of the sheet metal 42. The plate spring 45 is fixed to the sheet metal 42 by a fixing screw 46. Further, compression springs 44 are provided at positions opposite to the plate spring 45 at both ends of the sheet metal 42.

  FIG. 8 is a perspective view showing the opening / closing cover 26 according to the embodiment.

  As shown in FIG. 8, on both sides of the lower part of the opening / closing cover 26, bearing portions 26 a for fitting the support shaft (not shown) are provided. Upper and lower guide ribs 49a and 49b for guiding the conveyance of the sheet are formed on the upper and lower portions of the inner surface of the opening / closing cover 26. Support brackets 38 are provided on both sides of the inner surface of the opening / closing cover 26 in the vertical direction, and the secondary transfer unit 36 is rotatably supported by the support bracket 38 via a support shaft 39. In addition, a cam shaft 52 is provided substantially horizontally on the opening / closing cover 26, and a plurality of cam shafts 52 in the present embodiment are provided in the middle of the cam shaft 52.

  A power transmission gear train 57 is provided on one side of the inner surface of the opening / closing cover 26, and the secondary transfer roller 11 is connected to a driving mechanism on the copier body 1 side via the power transmission gear train 57. The camshaft 52 is connected to the power transmission gear train 57 via a shaft 61, a drive belt 62, a drive gear 63, and an electromagnetic clutch 58. The cam shaft 52 is intermittently rotated by the operation of the electromagnetic clutch 58 every time it rotates 180 degrees. The electromagnetic clutch 58 is an important point of the present invention, and will be described in detail later.

  FIG. 9 is a schematic view showing an arrangement configuration of the sheet metal 42, the compression spring 47, and the cam 53 according to the embodiment.

  As shown in FIG. 9, the cam 53 is opposed to the one surface side of the standing portion 42 a of the sheet metal 42 via a plate spring 45. The compression spring 47 is interposed between the other surface side of the standing portion 42a of the sheet metal 42 and a receiving member 55 provided integrally in the opening / closing cover 26 so as to elastically press the standing portion 42a of the sheet metal 42. It has become.

  FIG. 10 shows the rotation of the roller 3c, the secondary transfer roller 11 and the secondary transfer unit 36 over which the intermediate transfer belt 3 is stretched in a state where the secondary transfer roller 11 is pressed against the intermediate transfer belt 3 according to the embodiment. It is the schematic which shows the arrangement configuration of the dynamic fulcrum 36a.

  As shown in FIG. 10, it is perpendicular to a straight line L1 connecting the center S1 of the roller 3c and the center S2 of the secondary transfer roller 11, and is positioned on a straight line L2 passing through the center S2 of the secondary transfer roller 11. Further, a rotation fulcrum 36a of the secondary transfer unit 36 is provided.

  By the way, when forming a color image, a yellow toner image, a cyan toner image, and a magenta toner image formed with a time difference on the photosensitive drum 2 are sequentially transferred onto the intermediate transfer belt 3. Until completion, the secondary transfer roller 11 needs to be separated from the intermediate transfer belt 3 as shown in FIG. 11 and contact the intermediate transfer belt 3 as shown in FIG.

  When the secondary transfer roller 11 is brought into contact with the intermediate transfer belt 3, the electromagnetic clutch 58 is brought into a connected state, and from the state shown in FIG. 11, the power transmission gear train 57, the shaft 61, the drive belt 62, the drive gear 63, and the cam. A counterclockwise rotational force is applied to the cam 53 via the shaft 52. As a result, as shown in FIG. 12, the cam 53 is rotated 180 degrees to press the standing portion 42 a of the sheet metal 42 against the urging force of the compression spring 47 via the plate spring 45.

  By this pressing, the secondary transfer unit 36 is rotated in the direction of arrow B, and the secondary transfer roller 11 is brought into contact with the intermediate transfer belt 3. The sheet is conveyed between the secondary transfer roller 11 and the intermediate transfer belt 3 that are in pressure contact as described above, and the color toner image on the intermediate transfer belt 3 is transferred to the sheet.

  After this transfer, the secondary transfer roller 11 is separated from the intermediate transfer belt 3 again. In this case, the electromagnetic clutch 58 is disengaged, and the cam 53 is counterclockwise from the state shown in FIG. 12 via the power transmission gear train 57, the shaft 61, the drive belt 62, the drive gear 63, and the cam shaft 52. The rotational force of is given.

  As a result, the cam 53 is further rotated 180 degrees to rotate in the direction in which the pressing of the sheet metal 42 is released. By this rotation, as shown in FIG. 11, the secondary transfer unit 36 is rotated in the direction of arrow A around the rotation fulcrum 36 a by the urging force of the compression spring 47, and the intermediate transfer belt 3 and the secondary transfer roller 11. A gap a is formed between the two.

  Next, the electromagnetic clutch 58, which is an important point of the present invention, will be described with reference to FIGS.

  13 is a perspective view showing a state in which the electromagnetic clutch 58 according to the embodiment is attached to the opening / closing cover 26, FIG. 14 is a front view showing the electromagnetic clutch 58 according to the embodiment from the input gear 64 side, and FIG. FIG. 16 is a sectional view showing a connected state of the electromagnetic clutch 58 according to the embodiment, and FIG. 16 is a sectional view showing a disconnected state of the electromagnetic clutch 58 according to the embodiment.

  As shown in FIGS. 13 to 16, the electromagnetic clutch 58 is disposed on the inner surface of the opening / closing cover 26 through a support mechanism 65 (shown only in FIG. 14) within a predetermined angle range around the axis of the camshaft 52. It is supported with some backlash so that it can be rotated.

  A leaf spring 77 is provided on one side in the width direction of the lower surface of the electromagnetic clutch 58. The leaf spring 77 urges the electromagnetic clutch 58 in the direction opposite to the rotation of the input gear 64 (in the direction of arrow C). The urging force applied to the electromagnetic clutch 58 by the leaf spring 77 is set to about 0.4 to 0.8N.

  Next, the configuration of the electromagnetic clutch 58 will be described.

  The electromagnetic clutch 58 has a clutch body 66. The clutch body 66 is formed in a U-shaped cross section by upper and lower walls 66a and 66b parallel to each other and a vertical side wall 66c connecting the upper and lower walls 66a and 66b, and a cylindrical coil 67 is formed inside the clutch body 66. It is arranged substantially horizontally.

  One end surface of the coil 67 is opposed to the inner surface of the side wall 66 c of the clutch main body 66, and a metal swing plate 68 is disposed at a position facing the other end surface of the coil 67. The swing plate 68 is rotatably supported by the lower wall 66b of the clutch main body 66, and an upper end portion of the swing plate 68 by a spring 69 disposed below the lower wall 66b of the clutch main body 66. Is biased away from the clutch body 66.

  A stopper 70 is provided at the center of the upper end of the swing plate 68 on the opposite side of the clutch body 66. The stopper 70 is for stopping rotation of the collar 73 (described later), and is an approximate connection for connecting the first and second side walls 70a and 70b parallel to each other and the first and second side walls 70a and 70b. The horizontal upper wall 70c is formed in a U-shaped cross section.

  A cylindrical output hub 71 is rotatably inserted into the coil 67, and one end of the camshaft 52 is fitted into the output hub 71. The output hub 71 and the camshaft 52 extend through substantially the center of the swing plate 68 to the opposite side of the coil 67, and an input gear 64 (input shaft) is rotatably fitted on the tip thereof. Yes.

  The input gear 64 is rotated in a fixed direction (arrow D direction) by the drive gear 63. A cylindrical input hub 72 (transmission portion) is provided at the radial center of the side surface on the swing plate 68 side. Is provided. Around the input hub 72, a substantially cylindrical collar 73 (rotating body) is rotatably provided with a predetermined gap. The collar 73 includes a flange portion 74 at an end portion on the clutch body 66 side, and first and second projecting portions 75a and 75b are provided on both side surfaces thereof.

  The first and second protrusions 75a and 75b are arranged at positions shifted by 180 degrees with respect to the circumferential direction of the flange part 74, and each time the collar 73 rotates 180 degrees, the first protrusion 75a. Alternatively, the second protrusion 75b reaches the position of the stopper 70.

  Between the collar 73 and the input hub 72, a coil spring 76 having a winding direction opposite to the rotation direction (arrow D direction) of the input gear 64 is disposed. The coil spring 76 has a natural inner diameter smaller than that of the input hub 72 and is usually wound around the outer peripheral surface of the input hub 72 with a predetermined tightening force.

  The cross section of the metal wire constituting the coil spring 76 has a rectangular shape, and the inner surface of the coil spring 76 and the outer peripheral surface of the input hub 72 come into contact with each other in a wide area while being wound around the input hub 72. ing.

  The coil spring 76 has one end fixed to a portion of the collar 73 on the input gear 64 side and the other end fixed to a predetermined portion of the output hub 71. As a result, when the collar 73 is rotated in the direction opposite to the rotation of the input gear 64 (in the direction of arrow C) with respect to the camshaft 52 (in practice, the output hub 71), the coil spring 76 is twisted so that its inner diameter increases. It has become.

  Next, the operation of the electromagnetic clutch 58 having the above configuration will be described.

  When the input hub 72 is tightened by the coil spring 76, the input gear 64 is rotated via the coil spring 76 due to the frictional force acting between the outer peripheral surface of the input hub 72 and the inner peripheral surface of the coil spring 76. It is transmitted to the camshaft 52 and the collar 73.

  At this time, when the swing plate 68 is attracted by the coil 67, the second side wall 70b of the stopper 70 provided at the upper end of the swing plate 68 is the side surface of the flange portion 74 on the input gear 64 side, as shown in FIG. To approach.

  As a result, the second protrusion 75b provided on the side surface of the flange portion 74 on the input gear 64 side collides with the second side wall 70b of the stopper 70, and the rotation of the collar 73 is stopped.

  At this time, since a frictional force acts between the outer peripheral surface of the cam 53 and the leaf spring 45 of the secondary transfer unit 36, the camshaft 52 is difficult to rotate.

  For this reason, when the rotation of the collar 73 is stopped, the collar 73 and the camshaft 52 are rotated relative to each other, and the coil spring 76 connecting them is twisted, so that the inner diameter of the coil spring 76 is expanded. .

  As a result, the frictional force acting between the outer peripheral surface of the input hub 72 and the inner peripheral surface of the coil spring 76 is reduced, and a so-called shut-off state occurs in which the rotation of the input gear 64 is not transmitted to the camshaft 52. Even in the shut-off state, the outer peripheral surface of the input hub 72 and the inner peripheral surface of the coil spring 76 are slightly in contact with each other, which may cause chatter vibration.

  By the way, when the camshaft 52 is rotating, a slight rotational force is exerted on the clutch body 66 in the same direction as the rotation of the camshaft 52 (direction of arrow D) due to friction between the output hub 71 and the clutch body 66. Has occurred.

  For this reason, the clutch body 66 is slightly inclined with respect to the rotation direction of the camshaft 52 (the direction of the arrow D), that is, the rotation direction of the input gear 64. However, when the electromagnetic clutch 58 is in the disconnected state, the rotation of the camshaft 52 is stopped, so that the rotational force in the rotational direction of the input gear 64 does not act on the clutch body 66.

  As a result, the clutch body 66 slightly rotates in the opposite direction (arrow C direction) to the rotation of the input gear 64 due to the urging of the leaf spring 77. At this time, since the camshaft 52 hardly rotates due to the frictional force acting between the leaf spring 45 of the secondary transfer unit 36, the clutch body 66 rotates the input gear 64 relative to the camshaft 52. It will rotate in the opposite direction (arrow C direction).

  At this time, since the first protrusion 75a of the collar 73 and the first side wall 70a of the stopper 70 provided on the swing plate 68 are engaged, the clutch body 66 is in the direction opposite to the rotation of the input gear 64. Accordingly, the collar 73 rotates in the direction opposite to the rotation of the input gear 64 (in the direction of arrow C).

  As a result, relative rotation occurs between the camshaft 52 and the collar 73, and the coil spring 76 connecting them is twisted, whereby the inner diameter of the coil spring 76 is expanded.

  That is, if the clutch body 66 is urged by the leaf spring 77 in the direction opposite to the rotation of the input gear 64 (in the direction of arrow C), the inner diameter of the coil spring 76 is further increased when the electromagnetic clutch 58 is disengaged. Will expand.

  Thereby, when the electromagnetic clutch 58 is in the disconnected state, the frictional force acting between the outer peripheral surface of the input hub 72 and the outer peripheral surface of the coil spring 76 can be further reduced. Vibration is reduced and the occurrence of abnormal noise and the like is suppressed.

  According to the electrophotographic copying machine having the above-described configuration, the electromagnetic clutch 58 is urged by the leaf spring 77 in the direction opposite to the rotation of the input gear 64 (arrow C direction). Therefore, when the electromagnetic clutch 58 is in the disconnected state, the urging force by the leaf spring 77 becomes dominant because the rotation of the camshaft 52 stops, so that the electromagnetic clutch 58 is in the direction opposite to the rotation of the input gear 64 (arrow C). Direction).

  As a result, the collar 73 rotates in the same direction (arrow C direction), so that the inner diameter of the coil spring 76 connecting the camshaft 52 and the collar 73 is increased, and the outer surface of the input hub 72 and the coil spring are increased. The frictional force acting between the inner surface of 76 is further reduced.

  As a result, chatter vibration caused by frictional force acting between the outer surface of the input hub 72 and the inner surface of the coil spring 76 is reduced, and abnormal noise generated during operation of the electrophotographic copying machine is suppressed. Can do.

  In the present embodiment, switching when the secondary transfer roller 11 is brought into contact with and separated from the intermediate transfer belt 3 is described. However, the present invention is not limited to this, and the electromagnetic clutch 58 of the present invention is For example, the present invention can be applied to switching when the cleaner 15a is brought into and out of contact with the intermediate transfer belt 3, and is also applied to switching when the monochrome developing device 8B is brought into and out of contact with the photosensitive drum 2. You can also

  The present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the spirit of the invention in the stage of implementation. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment.

1 is a perspective view showing an external appearance of an electrophotographic copying machine according to an embodiment of the present invention. The perspective view which shows the state by which the double-sided printing unit which concerns on the embodiment was open | released. FIG. 2 is a schematic diagram showing an internal configuration of the electronic copying machine according to the embodiment. FIG. 3 is a perspective view showing a transfer belt unit and a secondary transfer unit according to the embodiment. A perspective view showing a secondary transfer unit according to the embodiment The perspective view which shows the secondary transfer unit which concerns on the same embodiment from a different angle. FIG. 4 is a front view showing a secondary transfer unit according to the embodiment. FIG. 3 is a perspective view showing a secondary transfer unit according to the embodiment. The perspective view which shows the secondary transfer unit which concerns on the same embodiment from a different angle. The perspective view which shows the opening / closing cover which concerns on the same embodiment. Schematic which shows the arrangement structure of the metal plate, compression spring, and cam which concern on the embodiment. Schematic showing an arrangement configuration of a roller on which the intermediate transfer belt is stretched, a secondary transfer roller, and a rotation fulcrum of the secondary transfer unit in a state where the secondary transfer roller 11 is pressed against the intermediate transfer belt according to the embodiment. Figure. FIG. 3 is a schematic diagram illustrating a state in which a transfer roller of a secondary transfer unit according to the embodiment is separated from an intermediate transfer belt. FIG. 6 is a schematic diagram illustrating a state in which a transfer roller of a secondary transfer unit according to the embodiment is in contact with an intermediate transfer belt. The perspective view which shows the state by which the electromagnetic clutch which concerns on the embodiment was attached to the opening / closing cover. The front view which shows the electromagnetic clutch which concerns on the same embodiment from the input gear side. Sectional drawing which shows the connection state of the electromagnetic clutch which concerns on the same embodiment. Sectional drawing which shows the interruption | blocking state of the electromagnetic clutch which concerns on the same embodiment.

Explanation of symbols

  52 ... Camshaft (output shaft), 64 ... Input gear (input shaft), 66 ... Clutch body, 72 ... Input hub (transmission part), 73 ... Collar (rotating body), 76 ... Coil spring, 77 ... Leaf spring ( Second diameter expanding means).

Claims (3)

A clutch body that is rotatably supported within a predetermined angle range around an axis line;
An input shaft that is rotationally driven in a fixed direction around the axis line;
An output shaft provided to be rotatable around the axis line;
A rotating body provided to be rotatable around the axis line;
A coil spring having a winding direction opposite to the rotation direction of the input shaft, one end fixed to the output shaft, and the other end fixed to the rotating body;
A transmission unit provided integrally with the input shaft, inserted into the coil spring, and tightened on the inner surface of the coil spring, thereby transmitting the rotation of the input shaft to the output shaft and the rotating body;
A first diameter expanding means for stopping rotation of the rotating body and expanding an inner diameter of the coil spring when the output shaft and the rotating body are rotating;
By energizing the clutch body in the direction opposite to the rotation of the input shaft, when the rotation of the output shaft stops, the rotating body is rotated in the energizing direction, and the inner diameter of the coil spring is increased. A second diameter expanding means for further expanding;
A clutch comprising:   The clutch according to claim 1, wherein the second diameter expanding means is a leaf spring.   An image forming apparatus comprising the clutch according to claim 1.

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