JP2006017271A - Driving transmission device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive transmission device capable of realizing stable drive transmission by regulating gear engaging position and roller connecting position, always maintaining appropriate gear engaging condition in response to temperature change of surroundings and deviation of gears, and regulating distance and parallel condition between shafts. <P>SOLUTION: This drive transmission device transmits rotation and torque between at least one pair of rotating force transmitting members. The drive transmission device has a center distance regulating member 12 provided on the same shaft with each of the rotating force transmitting members 11 to regulate distance between each of shafts by abutting on each other. Appropriate drive transmitting condition can be always maintained in response to temperature change of surroundings, and stable drive transmission can be realized. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a drive transmission device, and in particular, in a drive transmission device such as a gear drive transmission device that defines a gear meshing position of a gear or a roller drive transmission device that defines a joining position between rollers, Further, the present invention relates to a technique for realizing stable drive transmission by always maintaining an appropriate gear meshing state and roller joining state even with respect to roller eccentricity.

  In a drive unit used in an image forming apparatus such as a digital copying machine or a laser printer, a reduction system using gears of a large aperture and a small module is used in order to suppress the influence of uneven rotation of the gear meshing cycle on the image. Is effective. As can be seen from FIG. 18 showing the relationship between the resin gear module and the tooth height in the large-diameter small module gear having a radius of about 50 mm as shown in FIG. The effect of thermal expansion was relatively small when the small module gear was used, but the effect of thermal expansion cannot be ignored in small modules of module 0.2 or less. Specifically, in the gear transmission mechanism for precision driving of large and small modules, when the temperature of the environment changes, the gear diameter changes due to thermal expansion, making it impossible to maintain an appropriate meshing state, and stable drive transmission. Can not be. Therefore, there are problems such as idling due to disengagement of gears in a low temperature environment, and drive transmission errors due to the mixture of both teeth and single teeth in a high temperature environment. In addition, it is possible to suppress the effect of thermal expansion by fixing the drive shaft and driven shaft between the material of the gear and the material of the gear, but when the gear is eccentric when attached to the shaft Since the meshing position of the gear changes in one rotation, a section with a large backlash and a section with a small backlash are generated, which causes image density unevenness called image banding in an image forming apparatus such as a laser printer.

Thus, several proposals for solving these problems have been made. As one of them, according to Patent Document 1, a drive transmission mechanism is proposed in which a change due to a temperature change between two axes is driven by mounting the two axes on a base material equivalent to the linear expansion coefficient of the gear.
JP 2002-211942 A

  However, according to the above-mentioned Patent Document 1, a temperature gradient is generated by a difference in temperature distribution due to a difference in position in an actual apparatus or a heat generation of a drive motor being propagated to a base material, and a contraction amount different from that of a gear. The problem of becoming occurs.

  The present invention is for solving these problems, and defines a tooth meshing position and a roller joining position, and always maintains an appropriate tooth meshing state against environmental temperature changes and gear eccentricity. Then, it aims at providing the drive transmission device which can implement | achieve stable drive transmission by prescribing | regulating the distance and parallelism between axes | shafts.

  In order to solve the above problems, the drive transmission device of the present invention transmits rotation and torque between at least a pair of rotational force transmission members. The drive transmission device of the present invention is characterized by having an inter-axis distance defining member that is coaxial with each axis of the rotational force transmitting member and abuts each other to define the distance between the axes. Therefore, it is possible to always maintain an appropriate drive transmission state even with respect to environmental temperature changes and to realize stable drive transmission.

  When the rotational force transmission member is a gear, the inter-axis distance defining member is a cylinder or a coaxial disk that is coaxial with the shaft of the gear and has an outer diameter corresponding to the diameter of a reference pitch circle in at least a pair of gears. It is preferable that

  Further, when the rotational force transmitting member is a roller, the inter-axis distance defining member is coaxial with the roller axis, and is an outer portion that defines the distance between the roller shafts when the roller surfaces maintain predetermined contact. A cylindrical or coaxial disk having a diameter is preferable.

  Further, following the change when the distance between the axes defined by the inter-axis distance defining member changes, the axis of at least one of the rotational force transmitting members is relatively moved to reduce the distance between the axes. By providing a variable inter-axis distance variable mechanism, it is possible to always maintain an appropriate drive transmission state with respect to environmental temperature changes, and to realize stable drive transmission by defining the distance and parallelism between the axes.

  Furthermore, the material constituting the inter-shaft distance variable mechanism is the same as the thermal expansion of the rotation transmission member with respect to the temperature change of the environment because the material has the same linear expansion coefficient as that of at least one of the rotational force transmission members. Since the thermal expansion of the variable inter-axis distance mechanism occurs, the inter-axis distance is also correspondingly increased, and stable drive transmission can be realized by defining the inter-axis distance and parallelism.

  In addition, since the material of the inter-axis distance defining member is the same material as the rotational force transmitting member, the thermal expansion of the inter-axis distance defining member occurs as much as the thermal expansion of the rotational transmitting member. Stable drive transmission can be realized by defining the distance and parallelism between the axes.

  Furthermore, by forming the rotational force transmission member and the inter-shaft distance regulating member by integral molding, positioning within the molding die is less likely to cause eccentricity of rotation, making it possible to define a highly accurate drive transmission position. Even when the temperature of the environment changes, it is possible to always maintain an appropriate drive transmission state and realize stable drive transmission.

  In addition, by providing an elastic member on the entire or part of the contact surface of the inter-axis distance regulating member, high-frequency vibration generated during drive transmission is attenuated to reduce noise and rotational unevenness in the high-frequency region. Transmission can be achieved. Further, backlash can be reduced, and drive transmission that is resistant to load fluctuations can be achieved.

  Further, by having a rib having an outer diameter corresponding to the diameter of the reference pitch circle of the gear on the rim side surface of the gear coaxially with the gear, the teeth of the gears are in contact with each other when the gears are engaged with each other. Since the meshing position is maintained, it is possible to always maintain an appropriate meshing state even when the temperature of the environment changes, and to realize stable drive transmission.

  According to the drive transmission device of the present invention, it is possible to always maintain an appropriate drive transmission state with respect to environmental temperature changes and to realize stable drive transmission.

  FIG. 1 is a diagram showing a configuration of a drive transmission device according to a first embodiment of the present invention. (A) of the figure is a front view, (b) of the figure is a side view. As shown in the figure, a gear 100 which is a drive transmission device of the present embodiment includes a gear portion 11 having teeth 13 provided on the outer peripheral surface at a constant interval, and a reference pitch circle in the gear portion 11. The cylindrical portion 12 has an outer diameter corresponding to the diameter of the gear portion 11 and is coaxial with the gear portion 11. As shown in FIG. 2A, the gear 100 of the present embodiment having such a configuration is used as a gear coaxial with the drive shaft 22 of the motor 21 and a gear coaxial with the driven shaft 23, respectively. As shown in FIG. 2B, the tooth meshing position of the gears is defined by the position where the cylindrical portions 12 are joined. That is, the tooth meshing position of each gear is defined on the reference pitch circle of each gear. Therefore, according to the drive transmission device applied to the gear according to the present embodiment, the appropriate tooth meshing state is always maintained even with respect to environmental temperature changes, and further, the distance between the shafts is Parallelism is defined, and stable drive transmission can be realized. The cylindrical portion 12 may be a member integrated with the rotating shaft, and may be coupled to the resin gear by integral molding.

  Next, FIG. 3 is a view showing the configuration of the inter-shaft distance variable mechanism attached to the drive transmission device according to the first embodiment of the present invention. (A) of the figure is a front view of the entire drive transmission apparatus of the present embodiment, and (b) of the figure is a front view showing the configuration of the inter-axis distance variable mechanism. In the figure, the same reference numerals as those in FIGS. 1 and 2 indicate the same components. In the drive transmission device according to the first embodiment shown in FIG. Here, as shown in FIGS. 3A and 3B, the inter-shaft distance varying mechanism 30 is attached to a part of the housing 31 with screws or the like, and a shaft hole 32 through which the drive shaft 22 of the motor 21 passes. A notch groove 34 in which a slidable drive bearing member 33 is accommodated in order to keep the drive shaft 22 of the motor 21 parallel to the fixed driven shaft 23 and a shaft through which the driven shaft 23 passes. It has a mounting plate 36 provided with a hole 35. The drive bearing member 33 accommodated in the notch groove 34 of the mounting plate 36 slides in the arrow A shown in FIG. 3B which is the longitudinal direction of the notch groove 34, and further the longitudinal direction of the notch groove 34. It is pressed in both directions of the arrow A by each elastic force of an elastic member 38 provided between the end face in the direction and the stopper 37. On the other hand, a driven bearing member 39 provided with a hole coaxial with the shaft hole 35 through which the driven shaft 23 passes is attached to the mounting plate 36 with screws or the like. Further, a guide member 40 is provided in order to stably slide the drive bearing member 33 only in the two directions indicated by the arrow A. Here, in the case where the inter-shaft distance variable mechanism 30 is not provided, when the environmental temperature changes, the diameter of the reference pitch circle of the gear varies depending on the thermal expansion change of the radius of each gear portion 11 and each cylindrical portion 12. Along with this, the fixed axes are subjected to a phenomenon in which stress is applied in opposite directions due to the change in dimensions, and the distance between the axes and parallelism cannot be maintained. Therefore, by providing the inter-shaft distance variable mechanism 30 having the above-described configuration, the sum of the radius change amounts of the gear portions 11 and the cylindrical portions 12 that the drive bearing member 33 changes according to the thermal expansion change. It slides in both directions of the arrow A which is the direction between the axes so as to cancel, and the distance between the drive shaft 22 and the driven shaft 23 and the parallelism are maintained. Therefore, it is possible to always maintain an appropriate tooth meshing state and realize stable drive transmission. In addition, even when the gears are eccentric when attached to the shaft, the gears are always kept in proper mesh, and because they are provided on each shaft, the distance between the shafts and the parallelism are regulated to achieve stable drive transmission. can do.

  Here, in the case where the inter-shaft distance variable mechanism 30 of FIG. 3 is not provided, the above-described phenomenon occurs. However, a simple configuration corresponding to such a phenomenon, for example, as shown in FIG. Is attached to a part of the housing 31 with a screw or the like at a mounting position on the center extension line of the shaft hole 35 through which the driven shaft 23 provided on the mounting plate 41 passes, and is further slidable in the long groove 42. A structure may be employed in which the flat plate 43 holding the pin 41 is attached to the housing 31 and the mounting plate 41 is made of a material having the same linear expansion coefficient as the gear portion 11 and the cylindrical portion 12. By adopting such a configuration, like the gear portion 11 and the cylindrical portion 12 that thermally expands according to a temperature change, the mounting plate 41 itself also thermally expands according to a change in environmental temperature, and is particularly screwed. The drive shaft 22 is moved by thermal expansion from the center extension line of the shaft hole 34 toward the shaft hole 32, so that the distance and parallel between the drive shaft 22 and the drive shaft 22 can be reduced with reference to the fixed driven shaft 23. Can be maintained. Therefore, by producing the mounting plate 41 with a material having the same linear expansion coefficient as that of the material of at least one of the cylindrical portions 12, the cylindrical portion 12 has the same amount of thermal expansion as the pitch circle diameter of the gear with respect to a change in environmental temperature. Since the thermal expansion of the diameter occurs, the mounting plate 41 is also thermally expanded in the same manner, the position of the shaft hole 32 is changed, and the drive shaft 22 is moved. As a result, the distance between the shafts is changed correspondingly. Stable drive that can maintain tooth meshing on a circle and that defines the distance and parallelism between the shafts without excessive stress on the drive shaft, driven shaft, bearing member, cylinder, and gears. Transmission can be realized.

  Next, FIG. 5 is a diagram showing the configuration of the drive transmission device according to the second embodiment of the present invention. (A) of the figure is a front view, (b) of the figure is a side view. The same reference numerals as those in FIG. 1 denote the same components. The gear 200, which is the drive transmission device of the present embodiment shown in the figure, is provided with a cylindrical portion 12 so as to sandwich the gear portion 11 as a configuration different from that of the first embodiment. Therefore, as shown in FIGS. 6 (a) and 6 (b), the tooth meshing position of the gear 13 is maintained on the reference pitch circle of each gear, and the proper tooth meshing is always maintained even when the environmental temperature changes. Can be maintained, and more stable drive transmission can be realized, and the distance between the shafts and the parallelism are further defined by the cylindrical portions 12 on both sides of the gear portion 11, so that the teeth can be engaged. It is possible to minimize the influence of tooth collapse and eccentricity.

  Here, a modification of the gear 200 that is the drive transmission device in the second embodiment will be described. FIG. 7 is a front view showing an integrally molded gear made of POM material. The gear 71 shown in the figure has a gear part and a cylindrical part made of the same material, and the diameter of the outer peripheral end corresponding to the cylindrical part is the diameter of the reference pitch circle of the gear 13, so that Relatively equal deformations. Therefore, if the mold accuracy is adjusted with high accuracy, the amount of eccentricity can be minimized and the cost can be reduced. The material is not limited to plastic, but can also be applied to copper-based sintering, iron-based sintering, and Al alloy formation. FIG. 8 is a front view showing a gear having an outer peripheral end portion and teeth and a central portion made of different materials. In the gear 81 shown in the figure, the outer peripheral end portion 82 of the cylindrical portion and the teeth 13 are formed of a material having the same linear expansion coefficient, and the central portion 83 is formed of a material different from that of the teeth 13 and the outer peripheral end portion 82. . In order to eliminate the minute vibration caused by the propagation of the tooth meshing vibration of the tooth 13 and finally the propagation to the photosensitive member connected to the shaft of the drive transmission device, the tooth 13 and the outer peripheral end 82 have high vibration damping. The material is used, or a material with little deformation in terms of thermal and humidity can be selected, or a material for cost reduction can be selected and used depending on the purpose. Further, FIG. 9 is a front view showing a gear having a clearance groove formed at the outer peripheral end of the tooth and the cylindrical portion. In the gear 91 shown in the figure, a clearance groove 92 is formed between the tooth 13 and the outer peripheral end portion 82 of the cylindrical portion. Therefore, even if there is a backlash in the thrust direction, that is, the axial direction of the tooth meshing gear, it is possible to prevent the outer peripheral end portion 82 of the cylindrical portion from being damaged.

  FIG. 10 is a front view showing the configuration of the drive transmission device according to the third embodiment of the present invention. As shown in the figure, an elastic member 101 such as rubber is provided on the entire outer peripheral surface of the outer peripheral end of the cylindrical portion 12. The thickness, elastic coefficient, and material of the elastic member 101 are set so that the diameter of the end portion of the elastic member 101 corresponds to the diameter of the reference pitch circle of the gear when the teeth of the gear portion 11 are engaged with each other. . Therefore, when the cylindrical portions of the gears come into contact with each other when the teeth are engaged with each other, the temperature of the environment changes and the elastic member 101 is slightly deformed. However, the reference pitch of the gears against the temperature change of the environment. The thermal expansion of the diameter of the cylindrical portion 12 occurs as much as the thermal expansion of the diameter of the circle, so that an appropriate tooth meshing state can always be maintained and stable drive transmission can be realized. In addition, the elastic member 101 such as rubber provided on the entire outer peripheral surface of the outer peripheral end of the cylindrical portion 12 attenuates high-frequency vibration generated when the teeth are engaged, thereby reducing noise and rotation unevenness in the high-frequency region. Thus, a drive transmission device can be provided. Further, backlash can be reduced, and drive transmission that is resistant to load fluctuations can be achieved.

  FIG. 11 is a front view showing a configuration of a drive transmission device according to a fourth embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 10 denote the same components. As shown in the figure, an elastic member 101 such as rubber is provided on a part of the outer peripheral surface of the outer peripheral end of the cylindrical portion 12. When the teeth of the gear portion 11 are engaged with each other, the diameter of the cylindrical portion 12 where the elastic member 101 is not provided corresponds to the diameter of the reference pitch circle of the gear, and the cylindrical portions 12 are always in contact with each other. Thus, the thickness, elastic coefficient, and material of the elastic member 101 are set. The radius of the portion where the elastic member 101 is provided is larger than the radius of the outer peripheral surface of the outer peripheral end portion of the cylindrical portion 12 where the elastic member 101 is not provided. Then, the elastic member 101 is elastically deformed by the pressing force between the shafts, and the gear meshes in a state where the cylindrical portions 12 are always in contact with each other. Therefore, the thermal expansion of the diameter of the reference pitch circle of the gear against the temperature change of the environment. Even if the thermal expansion of the diameter of the cylindrical portion 12 occurs in the same amount, it is possible to always maintain an appropriate tooth meshing state and realize stable drive transmission. In addition, the elastic member 101 such as rubber provided at the outer peripheral end of a part of the cylindrical portion attenuates high-frequency vibration generated during tooth meshing, thereby reducing noise and rotation unevenness in the high-frequency region. An apparatus can be provided. Furthermore, it is possible to reduce backlash and drive transmission that is resistant to load fluctuations is possible. In addition, by forming a groove on the surface of the elastic member 101 shown in FIGS. 10 and 11, the amount of change due to thermal expansion can be further increased.

  FIG. 12 is a front view showing the configuration of the drive transmission device according to the fifth embodiment of the present invention. The gear, which is the drive transmission device of the present embodiment shown in the figure, is provided with a rib 121 on the rim side surface of the gear portion 11 so that the outer peripheral end portion is located at the diameter of the reference pitch circle. Since the rib 121 having an outer diameter corresponding to the diameter of the reference pitch circle of the gear is coaxial with the gear portion 11, the tooth meshing position in a state where the ribs of each gear are in contact with each other when meshing with the other gear. Will keep. Therefore, it is possible to always maintain an appropriate tooth meshing state with respect to a change in environmental temperature and to realize stable drive transmission. Moreover, since the rib 121 and the gear part 11 can also be obtained by integral molding, when the gear part 11 is eccentric, the rib 121 is similarly eccentric, so that the tooth meshing position is kept at an appropriate position. Can do. Furthermore, when the roundness error of the gear portion 11 occurs in the molding, for example, when the outer periphery is elliptical, the rib 121 is similarly elliptical, so that the tooth meshing position can be maintained.

  FIG. 13 is a front view showing the configuration of the drive transmission apparatus according to the sixth embodiment of the present invention. The gear, which is the drive transmission device of the present embodiment shown in the figure, has a coaxial disk 131 having a diameter of a reference pitch circle. Since the coaxial disk 131 having the outer diameter corresponding to the diameter of the reference pitch circle of the gear is coaxial with the gear portion 11, the tooth meshing position in a state where the disks of each gear are in contact with each other when meshing with the other gear. Will keep. Therefore, it is possible to always maintain an appropriate meshing state with respect to changes in environmental temperature, and to realize stable drive transmission.

  FIG. 14 is a front view showing an example in which the drive transmission device of the present invention is applied to a roller drive mechanism. The drive transmission device shown in the figure is an example in which the drive transmission unit and the driven transmission unit are roller-shaped members, and the roller surface of the first roller 141 contacts the roller surface of the second roller 142. It is a roller drive mechanism that contacts. As shown in (b) of the figure, the roller driving mechanism is configured such that the distance between the shaft 143 of the first roller 141 and the shaft 144 of the second roller 142 when the roller surfaces contact each other. In order to define parallelism, a coaxial cylindrical portion 145 is provided in a portion other than the roller surface of each of the rollers 141 and 142, respectively. Therefore, the roller surface of the first roller 141 can be in contact with the roller surface of the second roller 142 with no gap and with a predetermined uniform contact force.

  FIG. 15 is a front view showing a moving mechanism for moving the drive transmission device of the present invention. The moving mechanism shown in the figure is a moving mechanism for a small-diameter gear that moves following the expansion and contraction of the cylindrical portion of the large-diameter gear. The small-diameter gear formed on the motor side is supported so as to be rotatable with respect to the holder. At the other end, a spring hook portion 151 for abutting the large-diameter gear while applying a bias extends. A spring 152 is applied here to pull the two and bring them into contact. In the same figure, a rotating cam 153 is provided on a part of the arm having the spring hook portion 151, thereby enabling the large-diameter gear to be attached and detached.

  FIG. 16 is a characteristic diagram showing the relationship of the positional variation of the photoconductor caused by rotational eccentricity. As shown in the figure, the diameters of the cylindrical portions that rotate simultaneously with the gear drive trains of the four colors at the same time as the gears of the even number ratio are made equal so that the phase fluctuations of the position of the photoconductor generated by the rotation eccentricity are matched. Deviation is minimized.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications and substitutions are possible as long as they are described within the scope of the claims.

It is a figure which shows the structure of the drive transmission device which concerns on the 1st Example of this invention. It is a figure which shows the specific example of the drive transmission apparatus of the example of 1st Embodiment. It is a figure which shows the structure of the center distance variable mechanism attached to the drive transmission device which concerns on the 1st Example of this invention. It is a figure which shows the structure of another specific example of the drive transmission apparatus which concerns on the 1st Example of this invention. It is a figure which shows the structure of the drive transmission apparatus which concerns on the 2nd Example of this invention. It is a figure which shows the specific example of the drive transmission apparatus of the example of 2nd Embodiment. It is a front view which shows the gear integrally formed with the POM material. It is a front view which shows the gearwheel which comprised the outer peripheral edge part and tooth | gear, and center part of the cylindrical part with another material. It is a front view which shows the gearwheel which formed the escape groove in the outer peripheral edge part of a tooth | gear and a cylindrical part. It is a front view which shows the structure of the drive transmission apparatus which concerns on the 3rd Example of this invention. It is a front view which shows the structure of the drive transmission apparatus which concerns on the 4th Example of this invention. It is a front view which shows the structure of the drive transmission apparatus which concerns on the 5th Example of this invention. It is a front view which shows the structure of the drive transmission apparatus which concerns on the 6th Example of this invention. It is a front view which shows the example which applied the drive transmission apparatus of this invention to the roller drive mechanism. It is a front view which shows the moving mechanism which moves the drive transmission apparatus of this invention. FIG. 6 is a characteristic diagram showing a relationship between positional fluctuations of a photoconductor caused by rotational eccentricity. It is a front view which shows the gearwheel of a large aperture small module. It is a figure which shows the relationship between the module and tooth height of a gearwheel, and the radius variation | change_quantity by thermal expansion.

Explanation of symbols

11; Gear portion, 12, 145; Cylindrical portion, 13; Teeth,
30; Inter-shaft distance variable mechanism, 41; Mounting plate,
71, 81, 91, 100, 200; gears,
101; elastic member, 121; rib, 131; coaxial disk,
141; first roller; 142; second roller.

Claims (11)

In a drive transmission device that transmits rotation and torque between at least a pair of rotational force transmission members,
A drive transmission device comprising an inter-axis distance defining member that is coaxial with each axis of the rotational force transmitting member and abuts each other to define a distance between the axes.   When the rotational force transmission member is a gear, the inter-axis distance defining member is a cylinder that is coaxial with the shaft of the gear and has an outer diameter corresponding to a diameter of a reference pitch circle in at least a pair of gears. The drive transmission device according to 1.   When the rotational force transmission member is a gear, the inter-axis distance defining member is a coaxial disc that is coaxial with the gear shaft and has an outer diameter corresponding to the diameter of a reference pitch circle in at least a pair of gears. The drive transmission device according to claim 1.   When the rotational force transmitting member is a roller, the inter-axis distance defining member is coaxial with the roller axis, and is an outer surface that defines the distance between the roller shafts when the roller surfaces maintain predetermined contact. The drive transmission device according to claim 1, wherein the drive transmission device is a cylinder having a diameter.   When the rotational force transmitting member is a roller, the inter-axis distance defining member is coaxial with the roller axis, and is an outer surface that defines the distance between the roller shafts when the roller surfaces maintain predetermined contact. The drive transmission device according to claim 1, wherein the drive transmission device is a coaxial disk having a diameter.   Following the change when the distance between each axis defined by the inter-axis distance defining member changes, the axis of at least one of the rotational force transmitting members is relatively moved to reduce the distance between the axes. The drive transmission device according to claim 1, wherein a variable inter-axis distance variable mechanism is provided.   The drive transmission device according to claim 6, wherein a material constituting the inter-axis distance varying mechanism is a material having a linear expansion coefficient equal to that of at least one of the rotational force transmission members.   The drive transmission device according to claim 1, wherein a material of the inter-axis distance defining member is the same material as the rotational force transmission member.   The drive transmission device according to claim 8, wherein the rotational force transmission member and the inter-axis distance defining member are formed by integral molding.   The drive transmission device according to any one of claims 1 to 9, wherein an elastic member is provided on the entire surface or a part of the contact surface of the inter-axis distance defining member. The drive transmission device according to claim 2 or 3, wherein a rib having an outer diameter corresponding to a diameter of a reference pitch circle of the gear is provided coaxially with the gear on a rim side surface of the gear.

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