JP2014119102A - Rotational force transmission device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of impact noise and vibration between a driving gear and a driven gear due to rotation irregularity of the driving gear.SOLUTION: A rotational force transmission device 101 includes: a driving helical gear 123 rotating by a drive source; a driven helical gear 121B engaged with the driving helical gear, and movable in a rotational axis direction; a compression spring 126 receiving the driven helical gear moving in the rotational axis direction in proportion to an acceleration of the driving helical gear, and restricting an acceleration of the driven helical gear. If rotation irregularity occurs to the driving helical gear, the driven helical gear moves in H and J directions by the inclination of a cog of the driving helical gear and the driven helical gear, and the compression spring 126. This can prevent over-rotation due to the inertia of the driven helical gear resulting from backlash between the driving helical gear and the driven helical gear, and reduce impact noise and vibration due to the abutment between the driving helical gear and the driven helical gear.

Description

  The present invention relates to a rotational force transmission device that transmits rotational force with a gear, and an image forming apparatus including the rotational force transmission device.

  An image forming apparatus such as a copying machine, a printer, or a fax machine that forms an image on a sheet includes a roller pair as a pair of rotating bodies that convey the sheet. The roller pair is configured to rotate by transmitting a rotational force from a motor or another mechanism (hereinafter referred to as a drive source) by a rotational force transmission device including a gear train. In this case, there are a case where the roller pair rotates only in one direction and conveys the sheet in one direction, and a case where the roller pair rotates forward and backward to reciprocate and convey the same sheet. As a case of reciprocal conveyance, there is switchback conveyance for turning the sheet upside down to form images on both sides of the sheet.

  However, the rotational force transmission device has backlash on the gears of the gear train, so that the tooth of the driven gear and the tooth of the driving gear come into contact with each other due to uneven rotation of the drive source or switching of the rotation direction, and the impact sound and vibration. May be emitted.

  Hereinafter, an operation for generating an impact sound will be described. In addition, although the case where a stepping motor (hereinafter referred to as “ST motor”) that can easily control the rotation of a roller pair is used as a drive source will be described, the same phenomenon occurs in other types of motors.

  In general, the ST motor is configured to perform quick rotation every predetermined step angle every time a pulse is input to the ST motor. However, when the ST motor rotates by one step angle, the step angle and the rotation angular velocity are different, and the driven gear may be unevenly rotated. Note that the step angle of the ST motor and the angle of rotation of the gear teeth by one pitch may be different or the same.

  In FIG. 11A, when the drive spur gear 900 is rotated in the arrow A direction by an ST motor (not shown), the driven spur gear 901 is engaged with the drive spur gear 900 at the meshing portion Y and rotated in the arrow B direction. . At this time, rotation unevenness occurs in the ST motor, and the drive spur gear 900 may be accelerated from a predetermined rotational speed to a predetermined rotational speed or higher and then returned to the predetermined rotational speed. In this case, when the drive spur gear 900 is accelerated and then returns to a predetermined rotational speed, the driven spur gear 901 cannot immediately return to the predetermined rotational speed due to inertia, but overrotates by the amount of backlash. Then, it abuts against the drive spur gear 900 (FIG. 11 (B) G1). As a result, impact sound and vibration are generated.

  In some cases, the drive spur gear 900 is decelerated from a predetermined rotational speed to a predetermined rotational speed or less and then returned to the predetermined rotational speed. Also in this case, the driven spur gear 901 cannot be decelerated and rotated immediately from the predetermined rotational speed due to inertia, and is over-rotated by the backlash at the predetermined rotational speed and applied to the drive spur gear 900. (Fig. 11 (B) G1). As a result, impact sound and vibration are generated.

  Therefore, there is a configuration in which a viscous damper is provided on the drive shaft of the ST motor in order to reduce impact noise and vibration (Patent Document 1).

Japanese Utility Model Publication No. 61-33314

  However, the configuration of Patent Document 1 has a problem that the inertia of the ST motor shaft is increased by providing a flywheel in the damper, and the agility of forward / reverse rotation control of the motor is impaired.

  It is an object of the present invention to provide a rotational force transmission device that prevents the generation of impact noise and vibration between the drive gear and the driven gear caused by uneven rotation of the drive gear, and an image forming apparatus including the rotational force transmission device. is there.

  The rotational force transmission device of the present invention includes a driving helical gear that is rotated by a driving source, a driven helical gear that is meshed with the driving helical gear and is movable in the rotation axis direction, and the driving helical gear. And a restriction means for receiving the driven helical gear that moves in the direction of the rotation axis in accordance with the acceleration of the rotating shaft and restricting the acceleration of the driven helical gear.

  An image forming apparatus of the present invention transmits an image forming unit that forms an image on a sheet, a rotating body pair that conveys a sheet on which an image is formed by the image forming unit, and rotation of a drive source to the rotating body pair. A rotational force transmission device, wherein the rotational force transmission device is the rotational force transmission device described above.

  The rotational force transmission device of the present invention receives the driven helical gear that moves in the direction of the rotation axis according to the acceleration of the driving helical gear by the regulating means, and regulates the acceleration of the driven helical gear. It has become. For this reason, the rotational force transmission device of the present invention prevents over-rotation due to the inertia of the driven helical gear caused by uneven rotation of the driving gear, and the impact caused by the contact between the driving helical gear and the driven helical gear. Generation of sound and vibration can be prevented.

  Since the image forming apparatus of the present invention includes the rotational force transmission device that prevents the generation of impact sound and vibration caused by uneven rotation of the gears, the operation sound can be reduced.

FIG. 3 is a cross-sectional view of the image forming apparatus 1 according to the embodiment of the present invention along the sheet conveying direction. It is the schematic of the rotational force transmission apparatus 101 in embodiment of this invention. It is sectional drawing along the gear train of the rotational force transmission apparatus 101 of FIG. FIG. 4 is an enlarged perspective view of a driving helical gear 123, a follower helical gear 121A, and a driven helical gear 121B in the rotational force transmission device 101. 5 is a perspective view of a follower helical gear 121A, a driven helical gear 121B, and a rotation transmission mechanism 130 in the rotational force transmission device 101. FIG. It is the figure which showed the viscous fluid reservoir 121Bd of the driven helical gear 121B. FIG. 5 is a diagram showing the relationship between the rotation direction and the rotation time of a helical gear 123 when the reversing roller pair 110 is reversed. FIG. 3 is a perspective view of a driven helical gear 121B when the helical helical gear 121A is omitted in FIG. FIG. 3 is a perspective view of the driven helical gear 121B in the case where the following helical gear 121A is omitted and the helical gear 121C having a different diameter is integrally provided with the driven helical gear 121B. In FIG. 3, the driven helical gear 121 </ b> B and the related helical gear 121 </ b> B when the helical gear 121 </ b> A is omitted and a compression spring 226 is provided instead of the grease between the driven helical gear 121 </ b> B and the fixed plate 127. It is a perspective view with the part to do. It is a figure for demonstrating operation | movement of the conventional gear train.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention and a rotational force transmission device incorporated in the image forming apparatus will be described with reference to the drawings. In addition, the numerical value used in this embodiment is a reference numerical value for making the embodiment easy to understand, and is not a numerical value that limits the present invention.

(Image forming device)
FIG. 1 is a cross-sectional view of the image forming apparatus 1 according to the embodiment of the present invention along the sheet conveyance direction. The image forming apparatus 1 includes a sheet feeding unit 2 that feeds a sheet S, an image forming unit 3 that transfers a toner image onto the sheet, a fixing unit 4 that fixes the toner image on the sheet S, and a toner image that is fixed. A discharge unit 5 for discharging the sheet S, an image reading unit 60 for reading a document, and the like.

  The sheet feeding unit 2 is provided in the lower part of the apparatus main body 1 </ b> A of the image forming apparatus 1. The sheet feeding unit 2 includes a stacking tray 21 on which the sheets S are stacked, a pickup roller 22 that picks up the sheets S stacked on the stacking tray 21, and a separation feeding unit 23 that separates and feeds the picked up sheets S. It is equipped with. The sheet feeding unit 2 also includes a manual feeding unit 24 that can manually feed the sheet S from the side of the image forming apparatus 1. The manual feeding unit 24 includes a manual tray 25 on which sheets S are stacked, and a separation feeding unit 26 that separates and feeds sheets S stacked on the manual tray 25. The manual feed tray 25 is provided in the apparatus main body 1A so that the apparatus main body 1A can be opened and closed.

  The image forming unit 3 is disposed above the sheet feeding unit 2. The image forming unit 3 includes a photosensitive drum 31 on which a toner image is formed, a charging roller 32 that uniformly charges the surface of the photosensitive drum 31, and an electrostatic latent image on the photosensitive drum 31 by irradiating laser light. And a laser irradiation device 33 for forming the. Further, the image forming unit 3 includes a developing device 34 that visualizes the electrostatic latent image on the photosensitive drum 31 as a toner image, a transfer roller 35 that contacts the photosensitive drum 31 and forms a transfer nip N, and the like. Yes.

  The fixing unit 4 is provided in a sheet conveyance path downstream of the image forming unit 3 in the sheet conveyance direction (hereinafter simply referred to as “downstream side”).

  The discharge unit 5 is provided on the downstream side of the fixing unit 4. The discharge unit 5 includes a discharge roller pair 51 for discharging the sheet S from the inside of the apparatus main body 1A, and a discharge tray 52 for stacking the discharged sheets S. The image reading unit 60 is provided on the upper part of the apparatus main body 1 </ b> A of the image forming apparatus 1. The image reading unit 60 includes a document placing unit 61 for placing a document, a reading scanner 62 for reading image information of the document placed on the document placing unit 61, and the like.

  When the image forming apparatus 1 starts an image forming job, the laser irradiation device 33 moves the surface of the photosensitive drum 31 based on image information (image information signal) such as a document transmitted from a personal computer (not shown) or the reading scanner 62. Is irradiated with laser light. As a result, the surface of the photosensitive drum 31 that is uniformly charged to a predetermined polarity potential by the charging roller 32 is exposed, and an electrostatic latent image is formed on the surface of the photosensitive drum 31. The electrostatic latent image is developed by the developing device 34 and visualized as a toner image.

  In parallel with the toner image forming operation, the sheets S separated and fed one by one from the sheet feeding unit 2 are registered rollers provided in a sheet conveyance path on the downstream side of the conveyance roller pair 10 by the conveyance roller pair 10. The sheet is conveyed to the pair 11, and the skew is corrected by the registration roller pair 11. After that, the sheet S whose skew has been corrected is conveyed to the transfer nip N at a predetermined timing, and the visualized toner image is transferred to the sheet S by the transfer roller 35.

  The sheet S on which the toner image has been transferred is conveyed from the transfer nip N to the fixing unit 4, and receives heat and pressure at the fixing unit 4, so that the toner is melted and fixed as an image. Thereafter, the sheet S on which the image is fixed is discharged to the discharge tray 52 by the discharge roller pair 51, and the image forming job is completed.

  After the toner image is formed on one surface (first surface), the sheet on which the toner image is also formed on the other surface (second surface) passes through the reverse path 7 from the fixing unit 4 by the intermediate discharge roller pair 6. It is sent to the reverse roller pair 110. The leading end portion of the sheet S conveyed in the order of the reverse path 7 and the reverse roller pair 110 protrudes in the in-body discharge direction (the direction of arrow C in FIG. 1). The rear end portion of the sheet S held between the pair of reversing rollers 110 passes through the conveyance path switching flapper 111 and reaches a position of 7 mm (a position calculated based on a time after passing through a sheet detection sensor not shown). Then, the reverse roller pair 110 stops rotating and then reversely rotates. The reverse rotation is performed by the reverse rotation of the motor, which will be described later, and the rotational force transmission device 101. The reversely rotating reverse roller pair 110 pulls the sheet S into the apparatus main body 1A (in the direction of arrow D in the figure).

  As a result, the sheet S is switched back and turned upside down. The duplex conveyance roller pairs 8a, 8b, and 8c convey the sheet S to the registration roller pair 11 again. The registration roller pair 11 conveys the sheet to the transfer nip N. At this time, the second surface of the sheet S comes into contact with the photosensitive drum 31, and the toner image is transferred to the second surface at the transfer nip N. The sheet S on which the toner image is fixed by the fixing unit 4 is finally discharged to the discharge tray 52 by the discharge roller pair 51.

(Rotational force transmission device)
A rotational force transmission device 101 that transmits the rotation of a stepping motor (hereinafter referred to as “ST motor”) 122 as a drive source to the pair of reverse rollers 110 will be described with reference to the drawings.

  FIG. 2 is a schematic diagram of the rotational force transmission device 101 according to the embodiment of the present invention. FIG. 3 is a cross-sectional view taken along the gear train of the rotational force transmission device 101 of FIG. FIG. 4 illustrates a driving helical gear 123, a driven helical gear 121B that rotates following the driving helical gear 123, and a following gear that rotates following the helical helical gear 121B. It is an expansion perspective view with follower helical gear 121A. FIG. 5 is a perspective view of the follower helical gear 121 </ b> A, the driven helical gear 121 </ b> B, and the rotation transmission mechanism 130 in the rotational force transmission device 101. FIG. 6 is a view showing the viscous fluid reservoir 121Bd of the driven helical gear 121B.

(Configuration of rotational force transmission device)
The rotational force transmitting device 101 transmits the rotation of the ST motor 122 to the rotating shaft 112 of the driving roller 110a of the reversing roller pair 110 as a pair of rotating bodies. The reverse roller pair 110 includes a driving roller 110a and a driven roller 110b.

  A roller helical gear 120 is provided at one end of the rotating shaft 112 of the drive roller 110a in the reverse roller pair 110. The follower helical gear 121A meshes with the roller helical gear 120. The follower helical gear 121 </ b> A is rotatably provided on a rotation shaft 124 that is fixedly provided on the fixed plate 127. Further, a driven helical gear 121B is also rotatably provided on the rotating shaft 124.

  The following helical gear 121A is rotated following the helical gear 121B by a rotation transmission mechanism 130 provided between the following helical gear 121A and the driven helical gear 121B. The rotation transmission mechanism 130 is provided with a protrusion 121Aa protruding toward the driven helical gear 121B and a driven helical gear 121A and a driven helical gear 121B. It is comprised with rib 121Ba. The protrusion 121 </ b> Aa is formed in an arc shape along the outer periphery of the rotating shaft 124. A plurality of ribs 121Ba are formed radially from the rotating shaft 124. The protrusion 121Aa enters between the adjacent ribs 121Ba and 121Ba and comes into contact with the rib 121Ba in the rotational direction. In a state where the protrusion 121Aa enters between the adjacent ribs 121Ba and 121Ba, a gap (play) between the protrusion 121Aa and the adjacent ribs 121Ba and 121Ba can be rotated by a rotation angle of 5 °. Is formed. Due to this gap, transmission of vibration between the driven helical gear 121B and the following helical gear 121A can be prevented.

  A compression spring (compression coil spring) 126 loosely fitted on the rotary shaft 124 is provided between the following helical gear 121A and the driven helical gear 121B. One end of the compression spring 126 is received by the notch 121Bb of the rib 121Ba.

  The driven helical gear 121B meshes with the driving helical gear 123 fixed to the drive output shaft 128 of the ST motor 122. Thus, the rotation of the ST motor 122 is transmitted to the driving roller 110a via the driving helical gear 123, the driven helical gear 121B, the follower helical gear 121A, and the roller helical gear 120. It has become. Incidentally, the rotation speed of the ST motor is 40 to 50 rpm.

  An E-ring 125 is detachably mounted in a groove 124a formed on the outer periphery of the end of the rotating shaft 124. Since the compression spring 126 is interposed between the driven helical gear 121B and the follower helical gear 121A, the follower helical gear 121A is received by the E-ring 125, and the driven helical gear 121B will be described later. It is received by the fixed plate 127 through the grease W. When the driven helical gear 121B receives no rotational force, a gap G2 of 0.3 mm (FIG. 3) is generated between the driven helical gear 121B and the following helical gear 121A. . For this reason, the driven helical gear 121B and the follower helical gear 121A are movable by a gap G2 (0.3 mm) in the rotation axis directions H and J (the thrust direction of the gear) during rotation.

Between the side surface 121Bc on the opposite side to the surface of the driven helical gear 121B that receives the urging force of the compression spring 126 and the fixing plate 127 as a fixing member facing the side surface 121Bc, the side surface 121Bc has a viscosity. Grease W as a fluid is applied and interposed. The viscosity of the grease W is 90 mm ² / s. A concave viscous fluid reservoir 121Bd in which grease W is accumulated is formed on the side surface 121Bc of the driven helical gear 121B. An inclined surface 121Be is formed on the ridgeline between the side surface 121Bc and the viscous fluid reservoir 121Bd, and a wedge-shaped gap G3 (FIG. 6B) is formed by the inclined surface 121Be and the side surface 121Bc. For this reason, when the driven helical gear 121B rotates, the grease W stored in the viscous fluid reservoir 121Bd is pulled out from the viscous fluid reservoir 121Bd by the wedge-shaped gap, and is interposed between the side surface 121Bc and the fixing plate 127. It is supposed to be. As a result, the grease W is not deficient between the driven helical gear 121B and the fixed plate 127.

(Operation of rotational force transmission device)
Next, operations of the driving helical gear 123, the driven helical gear 121B, the following helical gear 121A, and the roller helical gear 120 when the ST motor 122 is driven will be described.

  3 and 4, the inclination directions of the teeth of the helical gears are as follows. The tooth 123a of the driving helical gear 123 is inclined to the right. The tooth 121Bf of the driven helical gear 121B is inclined to the left. The tooth 121Ab of the following helical gear 121A is inclined to the right. The teeth 120a of the roller helical gear 120 are inclined to the left. Incidentally, the twist angle of each tooth of the driving helical gear 123, the driven helical gear 121B, the following helical gear 121A and the roller helical gear 120 is 30 degrees.

(When driving helical gear 123 rotates in the direction of arrow E)
Normally, the ST motor 122 is rotated quickly at a predetermined rotation speed regularly by a predetermined step angle by a pulse. Along with this, the driving helical gear 123 also rotates quickly at a predetermined rotational speed regularly at a predetermined step angle, and the driven helical gear 121B also rotates according to the regular rotation of the driving helical gear 123. ing.

  In this case, when the ST motor 122 rotates and the driving helical gear 123 rotates in the direction of arrow E, the tooth 123a of the driving helical gear 123 pushes the tooth 121Bf of the driven helical gear 121B, and the driven is The helical gear 121B is rotated in the arrow M direction. When the driving helical gear 123 is rotating quickly at a predetermined rotational speed, the driven helical gear 121B moves in the direction of arrow H against the compression spring 126 due to the inclination of the teeth 121Bf, and the compression spring 126 It rotates while being pushed back in the direction of arrow J by the urging force. For this reason, the driven helical gear 121B is maintained in contact with the teeth of the driving helical gear 123. Even if the speed fluctuation occurs, the driven helical gear 121B overrotates by the amount of backlash due to inertia, and the driven helical gear is driven. There is no contact with the adjacent tooth of the gear 123. As a result, the rotational force transmission device 101 can prevent the generation of impact sound and vibration due to contact between the gears.

  However, the rotation unevenness occurs in the ST motor 122 during a predetermined one step angle, and the driving helical gear 123 is accelerated and rotated in the direction of arrow E to a predetermined rotational speed or more, and then returns to the predetermined rotational speed. There is a case. In this change in rotational speed, when the driving helical gear 123 is accelerated and rotated in the direction of arrow E, the driven helical gear 121B is pushed by the driving helical gear 123, and the predetermined rotation is caused by the inclination of the tooth 121Bf. It is moved extra in the direction of the arrow H by the amount accelerated by the speed. The amount of compression of the compression spring 126 is increased by the amount that the driven helical gear 121B is moved in the direction of the arrow H, and the urging force that pushes the driven helical gear 121B back in the direction of the arrow J increases.

  Thereafter, the driving helical gear 123 returns from the accelerated rotation to a predetermined rotational speed. However, the driven helical gear 121B does not immediately decelerate and rotate due to inertia, but over-rotates while accelerating in the direction of arrow M, so that the driven helical gear 123 disengages from the tooth that has been in contact with the tooth. Thus, there is a risk of contacting the adjacent teeth with the acceleration rotational speed. However, the driven helical gear 121B is pushed back in the direction of the arrow J by the compression spring 126 whose amount of compression has been increased, and the meshing state of the driven helical gear 123 with the teeth that have been in contact so far is maintained. The As a result, the driven helical gear 121B is prevented from over-rotating due to inertia and coming into contact with the adjacent tooth of the driving helical gear 123, so that impact sound and vibration are not generated.

  Note that the following helical gear 121A is a helical gear whose tooth inclination direction is different from the tooth of the driven helical gear 121B, so that the driven helical gear 121B moves in the direction of the arrow H. The following helical gear 121A moves in the direction of arrow J. For this reason, the compression spring 126 increases the amount compressed by the follower helical gear 121A, and the urging force that pushes the driven helical gear 121B back in the direction of arrow J increases.

  Further, there may be a case where the rotation unevenness occurs in the ST motor 122 during the predetermined one step angle, and the driving helical gear 123 decelerates to a predetermined rotational speed or less and then returns to the predetermined rotational speed. In this rotational speed change, when the driven helical gear 123 rotates at a reduced speed, the driven helical gear 121B cannot immediately rotate at a reduced speed due to inertia. For this reason, the driven helical gear 121B over-rotates in the direction of the arrow M at a predetermined rotational speed, away from the tooth 123a of the driving helical gear 123 that has been in contact so far, and is moved to the adjacent tooth. There is a risk of contact at a predetermined rotational speed. However, if the driven helical gear 121B tries to move away from the tooth that has been in contact with the driving helical gear 123 so far due to inertial rotation, the biasing force of the compression spring 126 causes the grease W side (in the direction of arrow J) ( (Viscous fluid side). Then, the driven helical gear is pressed against the grease W interposed between the driven helical gear 121B and the fixed plate 127, is decelerated and rotated by the viscosity of the grease W, and is driven to decelerate and rotate. The meshing of the helical gear 123 with the teeth that have been in contact so far is maintained. Also in this case, it is possible to prevent the generation of impact sound and vibration.

  Thereafter, the driving helical gear 123 returns to a predetermined rotational speed from a predetermined rotational speed or less. The driven helical gear 121b is pushed by the driving helical gear 123 and is moved in the direction of the arrow H by the inclination of the tooth 121Bf, the contact pressure with the grease W is reduced, and the accelerated helical gear 121b rotates smoothly. To return to a predetermined rotational speed.

(When driving helical gear 123 rotates in the direction of arrow F)
The above is the explanation of the operation when the driving helical gear 123 rotates in the direction of arrow E. However, since the driving helical gear 123 can rotate in the forward and reverse directions, the case where it rotates in the direction of arrow F next. The operation of the rotational force transmission device 101 will be described.

  When the ST motor 122 rotates in the reverse direction and the driving helical gear 123 rotates in the direction of arrow F, the tooth 123a of the driving helical gear 123 pushes the tooth 121Bf of the driven helical gear 121B, and the driven helical gear is driven. 121B is rotated in the direction of arrow Q. When the driving helical gear 123 is rotating quickly at a predetermined rotational speed, the driven helical gear 121B is moved in the direction of arrow J by the inclination of the tooth 121Bf and the elasticity of the compression spring 126. It rotates while being pressed against the grease W. For this reason, the driven helical gear 121B is maintained in contact with the same tooth of the driving helical gear 123 and is over-rotated by the amount of backlash due to inertia, and the driving helical gear 123 is adjacent to the driving helical gear 123. There is no contact with the teeth. As a result, the rotational force transmission device 101 can prevent the generation of impact sound and vibration due to contact between the gears.

  However, the rotation unevenness occurs in the ST motor 122 during the predetermined one step angle, and the driving helical gear 123 is accelerated and rotated in the direction of the arrow F beyond the predetermined rotational speed, and then returns to the predetermined rotational speed. There is a case. In this rotational speed change, when the driving helical gear 123 is accelerated and rotated in the direction of the arrow F, the driven helical gear 121B is pushed by the driving helical gear 123, and the predetermined rotation is caused by the inclination of the tooth 121Bf. It is moved extra in the direction of arrow J by the amount accelerated by the speed. The grease W is compressed by an amount corresponding to the extra movement of the driven helical gear 121B in the direction of arrow J, and the biasing force that pushes the driven helical gear 121B back in the direction of arrow H increases.

  Thereafter, the driving helical gear 123 returns from the accelerated rotation to a predetermined rotational speed. Due to inertia, the driven helical gear 121B does not immediately rotate at a reduced speed, but remains in accelerated rotation, overrotates in the direction of arrow Q, moves away from the tooth that has been in contact so far, and returns to a predetermined rotational speed. There is a possibility that the driven gear contacts the tooth adjacent to the helical gear 123 at the acceleration rotational speed. However, the driven helical gear 121B is rapidly decelerated and rotated by the viscosity of the grease W, and the meshing state with the teeth that have been in contact with the driving helical gear 123 until now is maintained. Further, the driven helical gear 121B is maintained in meshing with the teeth of the driving helical gear 123 that have been in contact so far by being pushed back in the direction of arrow J by the grease W whose compression amount has increased. Is done. As a result, the driven helical gear 121B is prevented from over-rotating due to inertia and coming into contact with the adjacent tooth of the driving helical gear 123, so that impact sound and vibration are not generated.

  Further, there may be a case where the rotation unevenness occurs in the ST motor 122 during the predetermined one step angle, and the driving helical gear 123 decelerates to a predetermined rotational speed or less and then returns to the predetermined rotational speed. In this rotational speed change, when the driven helical gear 123 rotates at a reduced speed, the driven helical gear 121B cannot immediately rotate at a reduced speed due to inertia. For this reason, the driven helical gear 121B over-rotates in the Q direction at a predetermined rotational speed, away from the tooth 123a of the driving helical gear 123 that has been in contact so far, and is applied to the adjacent tooth. There is a risk of abutting with the rotation speed. However, if the driven helical gear 121B tries to move away from the tooth that has been in contact with the driving helical gear 123 so far by inertial rotation, the driven helical gear 121B is pushed by the compression spring 126 to the grease W side in the arrow J direction (viscosity). To the fluid side). Then, the driven helical gear 121B is pressed against the grease W and is decelerated and rotated by the viscosity of the grease W, and the driven helical gear 123 that is rotating at a reduced speed is meshed with the teeth that have been in contact so far. Is maintained. Also in this case, it is possible to prevent the generation of impact sound and vibration.

  As described above, when the driven helical gear 121B rotates, the follower helical gear 121A follows and rotates through the rotation transmission mechanism 130, and the roller helical gear 120 rotates. Finally, the rotating shaft 112 and the driving roller 110a provided on the roller helical gear 120 rotate. The following helical gear 121A is also rotated forward and backward by the driven helical gear 121B, and the roller helical gear 120 is also rotated forward and backward. Since the following helical gear 121A and the roller helical gear 120 are also helical gears, the following helical gear 121A moves along the rotation shaft 124 in accordance with forward and reverse rotation. Thereby, the generation of impact sound and vibration due to the contact between the tooth 121Ab of the follower helical gear 121A and the tooth 120a of the roller helical gear 120 is prevented. The rotation transmission mechanism 130 drives the driving roller 110a when changing the rotation direction of the driving roller 110a of the pair of reversing rollers 110 by play with a rotation angle of 5 ° in the rotation direction of the driven helical gear 121B and the follower helical gear 121A. It is designed to absorb inertial rotation.

  In the above description, the case where the driving helical gear 123 is rotating in one direction has been described, but the case of reverse rotation will be described. That is, the operation of the rotational force transmission device 101 when the reverse roller pair 110 rotates forward and backward to carry the sheet in a switchback manner will be described.

  In order to convey the sheet in the direction of arrow C in FIG. 1, the rotational force transmission device 101 rotates the pair of reversing rollers 110 in the direction of arrow F by the ST motor 122 and the driving helical gear 123. When the sheet is fed backward in the direction of arrow D, the driving helical gear 123 is rotated in the direction of arrow E.

  When the driving helical gear 123 rotates in the direction of arrow F, the driven helical gear 121B rotates in the direction of arrow Q and is pressed against the grease W. When the driving helical gear 123 reverses from the arrow F direction to the arrow E direction, the driven helical gear 121B attempts to rotate inertially in the arrow Q direction. Is prevented. For this reason, by the reversal of the rotation direction of the driving helical gear 123, the teeth of the driving helical gear 123 are separated from the teeth 121Bf of the driven helical gear 121B that have been in contact so far, and the adjacent teeth 121Bf. The impact at the time of abutting is small, and impact sound and vibration are reduced.

  Thereafter, the driven helical gear 121B moves in the direction of the arrow H against the compression spring 126 by meshing with the driving helical gear 123, and corresponds to the rotation unevenness of the driving helical gear 123. Thus, the rotation is prevented by the generation of impact sound and vibration.

  As described above, the rotational force transmission device receives the driven helical gear that moves in the direction of the rotation axis in accordance with the acceleration generated by the rotational change of the driving helical gear by the compression spring or grease as the restricting means, The acceleration of the driven helical gear is regulated. In addition, the compression spring or grease is elastically deformed (the amount of regulation changes) according to the acceleration generated by the rotational change of the driving helical gear. Thereby, the rotational force transmission device can reduce the impact sound and vibration caused by the meshing of the gears.

  As shown in FIG. 7, when the pair of reversing rollers 110 is reversed, the time T1 during which the driving helical gear 123 is rotating in the F direction is 1 second, while it is rotating in the E direction. The waiting time T2 is set to 2 seconds. The time T <b> 1 is a time during which the sheet does not pass through the reverse roller pair 110 after the sheet starts to be conveyed in the arrow C direction by the reverse roller pair 110. The time T2 is a time required for the reversing roller pair 110 to convey the sheet in the D direction and to rotate the sheet somewhat to feed it into the apparatus main body 1A even after the sheet has been conveyed. In order to reliably feed the sheet into the apparatus main body 1A, T1 <T2 is set. Also, during the time T2, the reverse roller pair 110 is rotated slightly after the conveyance of the sheet is completed, and the load on each gear is reduced at this time, and the driven helical gear 121B is compressed by the compression spring 126. Therefore, it is located on the fixed plate 127 side. Thus, after that, when the driving helical gear 123 is rotated in the reverse direction to convey the sheet in the C direction to the reversing roller, the impact sound caused by the contact between the driving helical gear 123 and the driven helical gear 121B. And vibration can be reduced.

In the above description, the spring constant k of the compression spring 126 is set as follows. The relationship between the vibration frequency fm during operation of the ST motor 122 that slightly changes the rotation of the driving helical gear 123 and the natural frequency fp of the following helical gear 121A is set as shown in Equation (1). It is. m is the mass of the follower helical gear 121A.
fg <fp
⇔ (√k / m) / 2π <fp
⇔k <4π ² · m · fp ² (1)

  Incidentally, the spring constant k of the compression spring 126 of the rotational force transmission device 101 of the present embodiment is 0.1 N / mm.

  Thus, since the spring constant k of the compression spring 126 is set so that the relationship fg <fp is established, the vibration of the ST motor is driven by the driven helical gear 123, the driven helical gear 121B, the compression The follow-up is hardly transmitted to the helical gear 121A via the spring. In addition, an increase in noise due to vibration of the pulse motor can be prevented with a compact and simple configuration.

  Note that the rotation of the driven helical gear 121B is transmitted to the roller helical gear 120 via the following helical gear 121A. However, as shown in FIG. Only the tooth gear 121B may be provided, and the roller helical gear may be meshed with the driven helical gear. In this case, the teeth 120a of the roller helical gear 120 are inclined to the right (not shown).

  Further, as shown in FIG. 9, the driven helical gear 121B has a stepped gear in which a different-diameter driven helical gear 121C as an output gear having a diameter different from that of the driven helical gear 121B is coaxially formed, The roller helical gear 120 may be meshed with the non-diameter driven helical gear 121C. In FIG. 9, the different diameter driven helical gear 121C has a smaller diameter than the driven helical gear 121A, but may have a larger diameter. Further, the tooth 121Ca of the different-diameter driven helical gear 121C is inclined in the same direction as the tooth 121Bf of the driven helical gear 121B, but may be inclined in the opposite direction.

  Further, as shown in FIG. 10, a compression spring 226 may be provided instead of the grease W. The compression spring 226 as the restricting member allows the driven helical gear 121B to move in the arrow J direction and then pushes it back in the arrow H direction. The compression spring 226 operates in the same manner as the other compression spring 126 while the driven helical gear 121B moves in the directions of the arrows J and H, and the impact sound generated by the uneven rotation of the driving helical gear 123. Vibration is reduced. The compression springs 126 and 226 also move the driven helical gear 121B to the driving helical gear 123 and the roller helical gear 120 even if the driven helical gear 121B moves in the directions of arrows H and J. The elasticity is set so as to maintain the meshing position.

  In the above description, the motor is a stepping motor. However, the rotational force transmission device 101 can cope with a non-uniform rotation of a normal motor, not an ST motor. Further, the driving helical gear 123 may rotate using a rotational force from a rotational force transmission device of another device as a drive source instead of a motor. For this reason, a drive source is not limited to a motor.

DESCRIPTION OF SYMBOLS 1: Image forming apparatus, 4: Image forming part, 101: Rotational force transmission apparatus, 110: Reversing roller pair (rotating body pair), 110a: Drive roller, 120: Roller helical gear, 121A: Following helical gear 121B: driven helical gear, 121Bd: viscous fluid reservoir, 121C: helical gear of different diameter (output gear) 122: stepping motor (driving means), 123: driven helical gear, 124: rotating shaft, 126, 226: Compression spring (regulating means, spring), W: Grease (regulating means, viscous fluid)

Claims (12)

A driving helical gear rotated by a driving source;
A driven helical gear that meshes with the helical gear and is movable in the rotational axis direction;
A regulation means for receiving the driven helical gear that moves in the rotational axis direction according to the acceleration of the driven helical gear and regulating the acceleration of the driven helical gear;
A rotational force transmission device characterized by that. The regulation means changes a regulation amount according to the acceleration.
The rotational force transmission device according to claim 1. The regulating means is a spring;
The rotational force transmission device according to claim 1, wherein The restricting means is a viscous fluid located between a side surface of the driven helical gear and a fixing member facing the side surface.
The rotational force transmission device according to claim 1, wherein The regulating means is
A spring located on one side of the driven helical gear;
A viscous fluid positioned between a side surface opposite to the side surface receiving the biasing force of the spring of the driven helical gear, and a fixing member facing the opposite side surface;
The rotational force transmission device according to any one of claims 1 to 4, wherein the rotational force transmission device is provided. A viscous fluid reservoir is provided on at least one of a side surface of the driven helical gear and a fixing member facing the side surface.
The rotational force transmission device according to claim 4 or 5, wherein The drive helical gear can be rotated forward and backward,
The rotational force transmission device according to any one of claims 1 to 6. A follower gear facing the driven helical gear with the spring in between,
A rotation transmission mechanism that transmits rotation of the driven helical gear to the following gear with play in a rotation direction;
The rotational force transmission device according to claim 3 or 5, wherein The follower gear is a helical gear having a tooth inclination direction different from that of the driven helical gear.
The rotational force transmission device according to claim 8. The natural frequencies of the driving helical gear, the driven helical gear, and the spring are different from each other.
The rotational force transmission device according to any one of claims 3, 5, and 8. The rotation according to any one of claims 1 to 7, wherein the driven helical gear is a step gear integrally provided with an output gear formed coaxially with the driven helical gear. Power transmission device. An image forming unit for forming an image on a sheet;
A pair of rotating bodies for conveying a sheet on which an image is formed by the image forming unit;
A rotational force transmission device that transmits the rotation of the drive source to the pair of rotating bodies,
The torque transmission device is the torque transmission device according to any one of claims 1 to 11.
An image forming apparatus.

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