JP4792830B2 - Tooth missing gear, power transmission device and image forming apparatus - Google Patents

Description

  The present invention relates to a chipped gear, a power transmission device having the chipped gear, and an image forming apparatus having the power transmission device.

  In an image forming apparatus such as a copying machine, a printer, or a facsimile, a sheet supply apparatus that supplies a sheet for forming an image is used. This type of sheet supply apparatus has a sheet feeding cassette. The sheet feeding cassette stores a large number of sheets, and the uppermost sheet stored in the sheet feeding cassette is fed out by intermittent driving of a feed roll. . 2. Description of the Related Art As a power transmission device for intermittently driving a feed roll, there is known a device that uses a drive gear that rotates constantly and a driven gear that includes a tooth-missing gear. The driven gear is urged by a spring, for example, in one rotation direction. When the feed roll is stopped, the solenoid is engaged and fixed against the urging of the spring. When the solenoid is driven to release the engagement, the driven gear is preliminarily rotated by the urging of the spring, and the driving gear and the driven gear are engaged with each other.

  In the power transmission device configured as described above, depending on the preliminary rotation timing of the driven gear, the teeth of the driving gear and the teeth of the driven gear may be synchronized. It is damaged, abnormal noise is generated, or the drive gear is stopped. For this reason, in the driven gear, a bending portion is formed at a portion where the meshing is started, and when the teeth of the driving gear and the teeth of the driven gear are synchronized, the bending portion is bent in the radial direction to release the pressing force of each other. The technique to do is known (patent document 1).

JP-A-6-50406

  However, in the above-described conventional example, the bent portion is bent in the radial direction, so that there is a problem that the base portion of the bent portion is particularly easily damaged.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a tooth missing gear, a power transmission device, and an image forming apparatus that can prevent breakage of teeth due to riding on at the time of meshing by providing a bent portion, and can prevent breakage of the bent portion. There is.

The first feature of the present invention is that a gear main body, a bending portion formed so that one end is supported on the gear main body and the other end extends in the circumferential direction and is bent in the radial direction, and A tooth-missing portion that is upstream of the rotational direction and lacks tooth formation; and a plurality of teeth formed around the gear body portion and the bending portion, and an inner surface of the bending portion is the gear body A curved portion having a curved shape at a root portion supported by the portion, and a main portion formed following the curved portion and having a radius of curvature larger than that of the curved portion, and at least the curved portion and the main portion In the tooth closest to the connection point, at least one root portion of the tooth is connected to the outer surface of the bending portion with a smoothly spreading curve, and the tooth tip shape of the tooth formed in the bending portion is a circle. The teeth that are arcuate and are closest to the connection point between the curved portion and the main portion are At least a portion of the tooth profile of the is in the missing teeth gear located on the straight line connecting the said connection point with the center of the gear main body portion. Therefore, even if the teeth climb on the mesh, the bending portion can prevent the teeth from being damaged, and at least one root portion of the tooth closest to the connection point between the curved portion and the main portion can be prevented. Since it is connected to the outer surface of the bent part with a smoothly spreading curve, the expected fracture line can be made longer by the amount connected with the smoothly spreading curve, and the possibility of the bent part being damaged from the root part is reduced. can do.

Preferably, the tooth closest to the connection point between the curved portion and the main portion has a tooth thickness direction center of the tooth on a straight line connecting the center of the gear main body portion and the connection point. In this case, it is preferable that the tooth closest to the connection point between the curved portion and the main portion is connected to the outer surface of the flexible portion with a curved line in which both root portions spread smoothly.

Preferably, the tooth tip shape formed on the gear main body portion is different from the tooth tip shape formed on the flexure portion . In this case, the deflection unit is preferably different from the said deflection of the tip of the teeth formed on the base side of the shape and the bent part of the formed tooth side shape.

  Preferably, the bending portion is formed with a first tooth, a second tooth, and a third tooth from the tip of the bending portion, and a phase between the vertices of the first tooth and the second tooth. And the phase between the vertices of the second and third teeth is made different. Thus, by making the phase between the vertices of the teeth different, the probability that the teeth will bite can be increased, and the guide teeth of the first tooth, the second tooth, and the third tooth from the tip of the bending portion. As a function can be enhanced. Further, in this case, the first tooth has a linear portion on the upstream side in the rotational direction, the second tooth has a linear portion on the downstream side in the rotational direction, and the third tooth has a tooth tip. Is preferably arcuate. In addition, for example, when the distance from the gear on the other side is short, the first teeth and the second teeth are formed on the bending portion from the tip of the bending portion, and the first tooth has a toothpaste. It is preferable that it is lower than the tooth depth of the second tooth.

  Preferably, a convex portion that restricts the bending of the bending portion is formed at a portion of the gear main body portion that the bending portion opposes via the slit. Since the bending amount of the bending portion can be regulated by the bending portion coming into contact with the convex portion, the possibility that the bending portion is damaged can be further reduced.

The second feature of the present invention is that it has a drive gear formed with a large number of teeth, and a driven gear arranged to face the drive gear, the driven gear comprising a gear body portion, One end is supported by the gear body and the other end extends in the circumferential direction and is bent so as to bend in the radial direction; a tooth missing portion that is upstream of the bending portion in the rotational direction and lacks tooth formation; A plurality of teeth formed around the gear main body and the bending portion and meshing with teeth of the drive gear, and an inner surface of the bending portion is curved at a root portion supported by the gear main body. And a main part that is formed following the curved part and has a radius of curvature larger than that of the curved part, and at least in the tooth closest to the connection point between the curved part and the main part. Is a curved line in which at least one root of the tooth spreads smoothly. Is connected to the outer surface of the section, the tooth tip profile of the teeth formed on the flexible portion is arc-shaped, the closest tooth to the connection point between the main portion and the rounded portion has at least one tooth of the tooth The power transmission device is located on a straight line connecting the center of the gear body and the connection point .

Preferably, the teeth of the drive gear have a curved entire tip shape. Preferably, the bent portion of the driven gear is formed with a first tooth and a second tooth from a tip of the bent portion, and a phase between the first tooth and the vertex of the second tooth is the drive. It is different from the phase between the vertices of the gear teeth . More preferably, the bent portion of the driven gear is formed with a first tooth and a second tooth from the tip of the bent portion, and the phase between the first tooth and the vertex of the second tooth is the driving gear. The phase between the vertices of the teeth is different.

  Furthermore, the present invention includes an image forming apparatus provided with the above power transmission device.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an image forming apparatus 10 according to an embodiment of the present invention. The image forming apparatus 10 includes an image forming apparatus main body 12, an image forming unit 14 is mounted in the image forming apparatus main body 12, and a discharge unit 16 is provided on the upper portion of the image forming apparatus main body 12. A sheet supply device 18 described later is provided below the image forming apparatus main body 12.

  The discharge unit 16 includes an inclined unit 20 that is rotatable with respect to the image forming apparatus main body 12. The inclined portion 20 has a lower discharge port portion, and is inclined so as to gradually increase toward the front surface direction (the right direction in FIG. 1), with the discharge port portion as a lower end and a higher tip as an upper end. The inclined portion 20 is supported by the image forming apparatus main body 12 so as to be rotatable around the lower end. As shown by a two-dot chain line in FIG. 1, when the inclined portion 20 is rotated upward and opened, an opening portion 22 is formed, and a process cartridge 24 to be described later can be attached and detached through the opening portion 22. .

  The image forming means 14 is of, for example, an electrophotographic system, and includes an image carrier 26 made of a photosensitive member, a charging device 28 made of, for example, a charging roll for uniformly charging the image carrier 26, and charged by the charging device 28 An optical writing device 30 for writing a latent image on the image carrier 26 by light, a developing device 32 for visualizing the latent image of the image carrier 26 formed by the optical writing device 30 with a developer, and the developing device. A transfer device 34 composed of, for example, a transfer roll for transferring the developer image by 32 to a sheet, a cleaning device 36 composed of, for example, a blade for cleaning the developer remaining on the image carrier 26, and a sheet transferred by the transfer device 34 For example, a fixing device 38 composed of a pressure roll and a heating roll. The optical writing device 30 is composed of, for example, a scanning type laser exposure device, and is arranged in the vicinity of the front surface (right side surface in FIG. 1) of the image forming apparatus main body 12 in parallel with the sheet feeding cassettes 50 and 50 of the sheet supply device 18. The image carrier 26 is exposed across the area 32. Further, the developing device 32 has a developing roll 42 that faces the image carrier 26.

  The process cartridge 24 is obtained by integrating an image carrier 26, a charging device 28, a developing device 32, and a cleaning device 36. The process cartridge 24 is disposed immediately below the inclined portion 22 of the discharge portion 16 and is attached and detached through the opening portion 22 formed when the inclined portion 20 is opened as described above.

  In the image forming apparatus main body 12, for example, a resist roll 44 is disposed on the upstream side (lower side in FIG. 1) of the transfer device 34. The sheet conveyed from the sheet supply device 18 to the conveyance path 46 is temporarily stopped by the registration roll 44, sent to the image forming unit 14 at a predetermined timing, and an image is formed, and discharged to the discharge unit 16 by the discharge roll 48. Is done.

  The image forming apparatus main body 12 is provided with an opening / closing cover 49 for pulling out the fixing device 38. The opening / closing cover 49 is opened / closed toward the front surface of the image forming apparatus main body 12 (right direction in FIG. 1).

  In the sheet supply device 18, for example, two sheet feeding cassettes 50 and 50 are stacked in two stages. Each of the paper feed cassettes 50, 50 has a cassette body 52, 52 and a bottom plate 54, 54 provided on the cassette body 52, 52. The bottom plates 54 and 54 are supported by the cassette main bodies 52 and 52 so that the rear ends thereof are slidable with respect to the cassette main bodies 52 and 52 and can swing with the rear ends as fulcrums. A sheet bundle is placed on the bottom plates 54 and 54. Near the front ends of the cassette main bodies 52, 52 and the bottom plates 54, 54, for example, elastic bodies 55, 55 such as compression springs are provided to urge the bottom plates 54, 54 upward.

  In addition, sheet supply units 56 and 56 are provided near the upper front ends of the sheet feeding cassettes 50 and 50. The sheet supply units 56 and 56 include feed rolls 58 and 58 and conveyance rolls 60 and 60 that convey the sheets supplied from the feed rolls 58 and 58.

In FIG. 2, details of the sheet supply unit 56 are shown.
Flange portions 62 and 62 are provided on both sides near the front end of the above-described bottom plate 54 so as to protrude upward, and insertion holes 64 and 64 are formed through the flange portions 62 and 62. On the other hand, protruding pins 66, 66 are formed so as to protrude upward on both sides near the front end of the cassette main bodies 52, 52 described above, and the protruding pins 66, 66 are fitted into the insertion holes 64, 64, thereby the bottom plate. 54 is guided by the projecting pins 66 and 66 and moves up and down.

  The sheet supply unit 56 is provided with a main body frame 68 that is fixed integrally with the image forming apparatus main body 12 described above. A rotation shaft 70 is rotatably supported on the main body frame 68, and the above-described feed roll 58 is fixed to the rotation shaft 70. The feed roll 58 includes a half-moon-shaped core portion 72 and roller portions 74 and 74 that are provided on both sides of the core portion 72 and formed in a disk shape. The roller portions 74 and 74 are fixed concentrically with the rotating shaft 70. The core portion 72 is slightly larger in diameter than the roller portions 74 and 74, and is eccentric from the rotation shaft 70 by the larger diameter. Further, a facing roll 76 is rotatably provided on the main body frame 68 so as to face the feed roll 58. The separating roll 76 is formed of a member having a large frictional surface. The roller portions 74 and 74 of the feed roll 58 rotate while being in contact with the winding roll 76 by the rotation of the rotating shaft 70. Since the core portion 72 has a half-moon shape and the circumferential surface is eccentric from the roller portions 74 and 74, the uppermost sheet is fed out by intermittently abutting and rotating with the uppermost position of the sheet bundle stacked on the bottom plate 54. . At this time, if a plurality of sheets are sandwiched between the feed roll 58 and the separating roll 76, the separating roll 76 stops or reverses, causes the sheets to slip, and rolls the sheet, supplying only the uppermost sheet. It is supposed to be.

  As shown also in FIGS. 3 and 4, the power transmission device 78 includes a drive gear 80 and a driven gear 82. The drive gear 80 meshes with an input gear 83 connected to a motor (not shown). The driven gear 80 is a tooth-missing gear and is fixed to one end of the rotary shaft 70 described above and has a tooth-missing portion 84 that lacks tooth formation. When facing each other, the driving gear 80 is idled so that the driving force from the driving gear 80 is not transmitted to the driven gear 82. As shown in FIG. 3, the driven gear 82 is connected to one end of an urging means 86 made of an elastic body such as a tension spring. The urging means 86 urges the driven gear 82 in one direction. . A claw portion 88 is formed on the driven gear 82, and the movable piece 92 of the solenoid 90 is engaged with the claw portion 88. Therefore, when the solenoid 90 is driven from the state shown in FIG. 3, the engagement between the movable piece 92 and the claw portion 88 is released, the driven gear 82 is rotated by the urging force of the urging means 86, and the driving gear 80 is driven by the driven gear 82. To become engaged. Further, in the driven gear 80, a bending portion 96 is formed in the circumferential direction in the gear main body portion 94. One end of the bending portion 96 is supported by the gear main body portion 94 and can be bent in the radial direction.

  As shown in FIG. 2, the cam devices 98 and 98 are provided on both sides of the rotating shaft 70, for example. While the sheet is being supplied by the cam devices 98, 98, the bottom plate 54 is pushed up by the urging of the elastic bodies 55, 55. When the sheet supply is completed, the bottom plate 54 is pushed down against the elastic bodies 55, 55. Yes.

  Next, the details of the power transmission device 78 described above will be described with reference to FIGS. The drive gear 80 has a large number of teeth 100 having a constant pitch on the peripheral surface. These teeth 100 have, for example, a so-called full-tooth shape in which a tooth tip portion is a circular arc and a side surface portion is a curve such as an involute curve.

  On the other hand, the driven gear 82 has the tooth missing portion 84 and the bending portion 96 as described above. That is, a slit 102 is formed on the downstream side in the rotation direction following the peripheral surface of the tooth missing portion 84, and a bending portion 96 is formed through the slit 102. The inner surface of the bent portion 96 facing the slit 102 has a curved portion 104 that is curved at the root portion of the bent portion 96, and a main portion 106 that is formed following the curved portion 104. The curved portion 104 is composed of an arc having a radius of 1 mm, for example. Thus, by making the base part of the bending part 96 into a round shape, the breaking stress is dispersed and the strength can be increased. In addition, you may make it have a corner | angular part, without making the base part by the side of the gear main-body part 94 into a round shape. The main portion 106 has a radius of curvature larger than that of the curved portion 104, and is constituted by, for example, an arc centered on the center of the driven gear 82. In this embodiment, the radial width of the bending portion 96 in the main portion 106 is uniform. It has become.

  However, as indicated by a two-dot chain line in FIG. 5, the radial width of the bending portion 96 may be gradually increased toward the root portion. Thereby, since the breaking stress when the bending part 96 bends can be disperse | distributed, the possibility of the fracture | rupture of the bending part 96 can be decreased.

  Further, as shown by a two-dot chain line in FIG. 5, a convex portion 110 is formed in a portion of the gear main body 94 that opposes through the slit 102 in the vicinity of the tip of the bending portion 96, and the bending amount of the bending portion 94 is within a predetermined range. You may make it regulate the bending of the bending part 94 so that it may fit in.

  The driven gear 82 has a large number of teeth 108 formed on the outer peripheral surface of the gear main body 94 excluding the outer peripheral surface of the bending portion 96 and the tooth missing portion 84. For example, the bending portion 96 is formed with five teeth. The first tooth from the tip of the bending portion 96 is the first tooth 108a, the second tooth is the second tooth 108b, and the third tooth. Is the third tooth 108c, the fourth tooth is the fourth tooth 108d, and the fifth tooth is the fifth tooth 108e. The tooth profile of the first tooth 108a is a straight line on the upstream side in the rotational direction, the tip of the tooth is an arc, and the downstream side in the rotational direction is a curve such as an involute. The apex of the first tooth 108a is shifted downstream in the rotational direction. The tooth profile of the second tooth 108b is a curve such as an involute on the upstream side in the rotational direction, the tooth tip is an arc, and the downstream side in the rotational direction is a straight line. The apex of the second tooth 108b is shifted upstream in the rotational direction. The tooth shapes of the third tooth 108c, the fourth tooth 108d, and the fifth tooth 108e are full-circular shapes in which the upstream side and the downstream side are curves such as involute, and the tooth tip is an arc.

  Since the vertex of the first tooth 108a is shifted to the downstream side and the vertex of the second tooth 108b is shifted to the upstream side, the phase between the vertexes of the first tooth 108a and the second tooth 108b is It is shorter than the phase between the vertices of the tooth 100. Further, the phase between the vertices of the second teeth 108 b and the third teeth 108 c is longer than the phase between the vertices of the teeth 100 of the drive gear 80. The phase between the vertices of the third teeth 108c and the fourth teeth 108d is equal to the phase between the vertices of the teeth 100 of the drive gear 80. Therefore, even if the first teeth 108a are in contact with each other in synchronization with one tooth 100 of the drive gear 80, the second teeth 108b are in contact with the next tooth 100 of the drive gear 80. In addition, even if the second teeth 108b are in contact with one tooth 100 of the drive gear 80 and the tooth tips contact each other, the third tooth 108c is the next tooth 100 of the drive gear 80. And the tooth tips can be prevented from coming into contact with each other, and the engagement of both teeth can be promoted.

  The tip circles of the first teeth 108a and the second teeth 108b are formed smaller than the third to fifth tip circles, and the tips of the first teeth 108a and the second teeth 108b are the drive gear 80. The probability of contact with the other teeth 100 is reduced, and the mutual engagement of the teeth is facilitated by facilitating the mutual sliding of the teeth. Further, the teeth 108a to 108e formed on the bending portion 96 have arcuate tooth tips as described above, whereas the teeth 108 formed on the gear main body portion 94 are cut into a flat shape. , Each shape is different. The teeth 108a to 108e formed on the bending portion 96 allow the ride-up, whereas the teeth 108 formed on the gear main body portion 94 should not be run-up, so the tooth tip is cut.

As best shown in FIG. 6, a total of five locations, the downstream root portion of the third tooth 108c, the both side root portions of the fourth tooth 108d, and the both side root portions of the fifth tooth 108e, have a smoothly spreading curve, For example, it is connected to the outer surface of the bending portion 96 with an arc. In particular, the fifth tooth 108e is the tooth closest to the connection point between the curved portion 104 and the main portion 106, and the fifth tooth 108e is on the radial straight line L1 connecting the center of the driven gear 82 and the connection point. There is a center in the tooth thickness direction (circumferential direction), and the root portions on both sides of the fifth tooth 108e are arcuate. For this reason, as shown by a two-dot chain line in FIG. 6, it is possible to reduce the possibility that the fracture prediction lines L2 and L3 spread on both sides and the flexure 96 breaks from the root portion.
In this embodiment, the center of the tooth thickness direction (circumferential direction) of the fifth tooth 108e is on the straight line L1, but the present invention is not limited to this, and the tooth thickness direction is in the vicinity of the straight line L1. It suffices if there is a center, and furthermore, a part of the tooth profile of the tooth 108e may be on the straight line L1.

  In addition, as shown in FIG. 7, the tooth depth of the first tooth 108a can be made lower than that of the other teeth. When lowering, the upstream side in the rotational direction is cut, and the shape on the downstream side in the rotational direction is maintained. Thereby, the phase between the vertices of the first tooth 108a and the second tooth 108b can be further shortened. As described above, when the power transmission device 78 is used for driving a feed roll of a paper feeding device, when the angle of the cut portion of the half-moon-shaped core portion is to be reduced and the portion in contact with the sheet is to be lengthened, the drive is performed. It is necessary to bring the gear 80 and the driven gear 82 closer. If the distance until the drive gear 80 and the driven gear 82 are engaged with each other is short, when the tooth depth of the first teeth 108a is increased as in the case of the other teeth as in the above embodiment, the drive gear 80 Although the impact when the tooth 100 and the first tooth 108a are synchronized with each other and the tips of the teeth contact each other is large, the impact is reduced by shortening the tooth depth of the first tooth 108a as in this embodiment. Since the phase between the apexes of the first teeth 108a and the second teeth 108b can be shortened, the probability of meshing can be further increased.

  As described above, the present invention can be applied to a chipped gear that prevents the teeth from climbing when engaged, and is used in a power transmission device using the chipped gear, and further includes the power transmission device. It can be used for an image forming apparatus.

1 is a side view showing an image forming apparatus according to an embodiment of the present invention. It is a perspective view which shows the sheet supply part used for embodiment of this invention. It is a front view which shows the power transmission device which concerns on embodiment of this invention. It is a side view which shows the power transmission device which concerns on embodiment of this invention. It is a front view which shows the principal part of the drive gear and driven gear which concern on embodiment of this invention. It is a front view which expands and shows the bending part tip vicinity of the driven gear which concerns on embodiment of this invention. It is a front view which expands and shows the bending part base vicinity of the driven gear which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 18 Sheet supply apparatus 50 Paper feed cassette 56 Sheet supply part 58 Feed roll 80 Drive gear 82 Driven gear 84 Tooth missing part 94 Gear body part 96 Deflection part 100 Teeth 102 Slit 104 Curved part 106 Main part 108 Teeth 108a First 1st tooth 108b 2nd tooth 108c 3rd tooth 108d 4th tooth 108e 5th tooth 110 convex part

Claims (14)

A gear body,
One end of the gear body is supported, and the other end extends in the circumferential direction and is bent in the radial direction.
A tooth missing portion on the upstream side of the bending portion in the rotational direction and lacking tooth formation;
A plurality of teeth formed around the gear body and the flexure,
The inner surface of the bent portion has a curved portion that is curved at a root portion supported by the gear body portion, and a main portion that is formed following the curved portion and has a larger radius of curvature than the curved portion. And
At least in the tooth closest to the connection point between the curved portion and the main portion, the root portion of at least one of the teeth is connected to the outer surface of the bending portion with a smoothly spreading curve ,
The tip shape of the tooth formed in the bending portion is an arc shape,
Tooth closest to the connection point between the curved portion and the main portion is a tooth missing gear in which at least a part of the tooth profile of the tooth is on a straight line connecting the center of the gear body portion and the connection point. . Closest tooth to the connection point between the main portion and the curved portion, claim 1, characterized in that there is a centering tooth thickness direction center of the tooth on the straight line connecting the said connection point of the gear main body portion The toothless gear described. 3. The tooth missing portion according to claim 2 , wherein the tooth closest to the connection point between the curved portion and the main portion is connected to the outer surface of the flexible portion with a curved line in which both root portions spread smoothly. gear. The tooth missing gear according to any one of claims 1 to 3 , wherein a tooth tip shape of the tooth formed on the gear main body portion is different from a tooth tip shape of the tooth formed on the bending portion. 5. The chipped gear according to claim 4 , wherein a tooth shape formed on a distal end side of the bending portion is different from a tooth shape formed on a root side of the bending portion. A first tooth, a second tooth, and a third tooth are formed on the bending portion from the tip of the bending portion, and the phase between the vertices of the first tooth and the second tooth, and the second tooth The chipped gear according to any one of claims 1 to 5, wherein a phase between the tops of the third tooth and the third tooth is different. The first tooth has a linear portion on the upstream side in the rotational direction, the second tooth has a linear portion on the downstream side in the rotational direction, and the third tooth has an arcuate tip. The tooth-missing gear according to claim 6 . The first tooth and the second tooth are formed in the bent portion from the tip of the bent portion, and the tooth depth of the first tooth is lower than the tooth depth of the second tooth. The tooth-missing gear according to any one of 1 to 7 . Wherein the portion of the gear main body flexures counteracts through the slit, missing tooth gear according to any one of claims 1 to 8, characterized in that convex portions for regulating the deflection of the flexible portion is formed . A drive gear formed with a large number of teeth;
A driven gear disposed opposite to the drive gear,
The driven gear includes a gear body portion, a bending portion formed so that one end is supported on the gear body portion and the other end extends in the circumferential direction and is bent in the radial direction, and on the upstream side in the rotation direction of the bending portion. A tooth missing portion that lacks the formation of teeth, and a plurality of teeth that are formed around the gear main body portion and the bending portion and mesh with the teeth of the drive gear;
The inner surface of the bent portion has a curved portion that is curved at a root portion supported by the gear body portion, and a main portion that is formed following the curved portion and has a larger radius of curvature than the curved portion. And
At least in the tooth closest to the connection point between the curved portion and the main portion, the root portion of at least one of the teeth is connected to the outer surface of the bending portion with a smoothly spreading curve ,
The tip shape of the tooth formed in the bending portion is an arc shape,
The tooth closest to the connection point between the curved portion and the main portion is such that at least a part of the tooth profile of the tooth is on a straight line connecting the center of the gear body and the connection point. .   The power transmission device according to claim 10, wherein the teeth of the drive gear have a curved entire tooth profile. The bent portion of the driven gear is formed with a first tooth and a second tooth from the tip of the bent portion, and the phase between the first tooth and the second tooth vertex is between the tooth vertexes of the drive gear. The power transmission device according to claim 10 , wherein the power transmission device is different from a phase of the power transmission device. The bent portion of the driven gear is formed with a first tooth, a second tooth, and a third tooth from the tip of the bent portion, and a phase between the top of the first tooth and the second tooth and a second tooth The power transmission device according to any one of claims 10 to 12, wherein a phase between the teeth and the vertex of the third tooth is different from a phase between the teeth of the drive gear. An image forming apparatus provided with a power transmission device according to any one claims 10 to 13.

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