JP2013113316A - Power transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power transmission device which improves assemblability by reducing the number of components.SOLUTION: The power transmission device 1 includes: a pair of rotating members 3, 5 arranged so as to relatively rotate; a friction clutch 7 which is arranged between the pair of rotating members 3, 5 and intermits power transmission between the pair of rotating members 3, 5; and a ball screw mechanism 15 having a screw shaft 9, a nut 11 arranged on an outer circumference of the screw shaft 9 so as to rotate and move axially, and a plurality of balls 13 interposed between the screw shaft 9 and the nut 11, and gives pressing force to the friction clutch 7. The one rotating member 5 is supported by a fixing system member 21 through a pair of first and second bearings 17, 19. When the nut 11 rotates and moves to the one axial direction by receiving thrust force, the first bearing 17 receives thrust reaction force to the other axial direction generated in the screw shaft 9.

Description

  The present invention relates to a power transmission device applied to a vehicle.

  Conventionally, as a power transmission device, a pair of rotating members arranged so as to be relatively rotatable, a friction clutch arranged between the pair of rotating members and intermittently transmitting power between the pair of rotating members, a screw shaft, and the screw A ball screw mechanism that includes a nut that is rotatable on the outer periphery of the shaft and is movable in the axial direction, and a plurality of balls interposed between the screw shaft and the nut is provided with a ball screw mechanism that applies a pressing force to the friction clutch. (For example, refer to Patent Document 1).

  In this power transmission device, the nut of the ball screw mechanism rotates, receives a thrust force, and moves in the axial direction in the connecting direction of the friction clutch, whereby the friction clutch is connected. By connecting the friction clutch, power can be transmitted between the pair of rotating members.

US Patent Application Publication No. 2004/0163919

  By the way, in the power transmission device as described in Patent Document 1, when the nut of the ball screw mechanism receives a thrust force and moves in one axial direction, the screw shaft attempts to move in the other axial direction opposite to the nut. Reaction force is generated.

  The thrust reaction force generated on the screw shaft is received by a thrust needle bearing disposed between the fixing shaft fixed to one of the pair of rotating members and the screw shaft. One rotating member is supported on both sides in the axial direction by a pair of bearings, and one of the pair of bearings is disposed on the axially outer side of the thrust needle bearing and the fixed member.

  However, the power transmission device as in Patent Document 1 has a large number of parts such as a thrust needle bearing and a fixed member for receiving a thrust reaction force of the ball screw mechanism, and a bearing that rotatably supports one rotating member. Accompaniment was also reduced.

  Therefore, an object of the present invention is to provide a power transmission device that can reduce the number of parts and improve the assemblability.

  The present invention includes a pair of rotating members arranged to be relatively rotatable, a friction clutch arranged between the pair of rotating members and intermittently transmitting power between the pair of rotating members, a screw shaft, and an outer periphery of the screw shaft. And a ball screw mechanism for applying a pressing force to the friction clutch. The power transmission device includes a nut that is rotatable and axially movable, and a plurality of balls that are interposed between the screw shaft and the nut. And one rotating member of the pair of rotating members is supported by a stationary member via a pair of first and second bearings, and the first bearing has a thrust force when the nut rotates. When receiving and moving in one axial direction, it receives a thrust reaction force in the other axial direction generated in the screw shaft.

  In this power transmission device, when the first bearing that supports one rotating member rotates and the nut is rotated and receives the thrust force and moves in one axial direction, it receives the thrust reaction force in the other axial direction generated in the screw shaft. The first bearing can have two functions of supporting one rotating member and receiving a thrust reaction force of the ball screw mechanism.

  Therefore, in such a power transmission device, since the first bearing has two functions of supporting one rotating member and thrust reaction force receiving of the ball screw mechanism, the number of parts can be reduced and the assembling property can be improved. be able to.

  Advantageous Effects of Invention According to the present invention, there is an effect that it is possible to provide a power transmission device that can reduce the number of parts and improve the assemblability.

1 is a schematic diagram showing a power system of a vehicle to which a power transmission device according to an embodiment of the present invention is applied. It is sectional drawing of the power transmission device which concerns on embodiment of this invention.

  First, an example of a vehicle power system to which a power transmission device according to an embodiment of the present invention is applied will be described with reference to FIG.

  As shown in FIG. 1, the power system of the vehicle includes a drive source 101 such as an engine or an electric motor, a transmission 103 as a speed change mechanism, a front differential 105 that allows differential of the left and right wheels on the front wheel side, and a front axle. 107, 109, front wheels 111, 113, a transfer 115, a propeller shaft 117, and a friction clutch 7 (see FIG. 2) that intermittently controls the driving force transmitted from the front wheel side to the rear wheel side. The apparatus 1 includes a rear differential 119 that allows differential between the left and right wheels on the rear wheel side, rear axles 121 and 123, rear wheels 125 and 127, and the like.

  In the vehicle power system configured as described above, the driving force of the driving source 101 is transmitted to the front differential 105 via the transmission 103. The driving force transmitted to the front differential 105 is distributed to the front wheels 111 and 113 via the front axles 107 and 109 and also transmitted to the transfer 115 via the hollow shaft 129 connected to the front differential 105. The driving force transmitted to the transfer 115 is direction-changed by the direction-changing gear set 131 and is transmitted to the friction clutch 7 of the power transmission device 1 via the propeller shaft 117.

  When the friction clutch 7 is connected, the driving force transmitted to the power transmission device 1 is transmitted to the rear differential 119 and distributed from the rear axles 121 and 123 to the rear wheels 125 and 127. It becomes a driving state. When the connection of the friction clutch 7 is released, the vehicle enters a two-wheel drive state of front wheel drive. Hereinafter, the power transmission device according to the embodiment of the present invention will be described with reference to FIG.

  The power transmission device 1 according to the present embodiment includes an outer rotating member 3 and an inner rotating member 5 as a pair of rotating members arranged so as to be relatively rotatable, and between the outer rotating member 3 and the inner rotating member 5. A friction clutch 7 which is arranged and intermittently transmits power between the outer rotating member 3 and the inner rotating member 5; a screw shaft 9; and a nut 11 which can be rotated on the outer periphery of the screw shaft 9 and can be moved in the axial direction. A ball screw mechanism 15 that includes a plurality of balls 13 interposed between the screw shaft 9 and the nut 11 and applies a pressing force to the friction clutch 7 is provided.

  The inner rotating member 5 is supported by a casing 21 as a fixed system member via a pair of first and second bearings 17 and 19. The first bearing 17 receives a thrust force as the nut 11 rotates. When moving in one axial direction, the thrust reaction force in the other axial direction generated in the screw shaft 9 is received.

  The first bearing 17 is supported by the casing 21, and the second bearing 19 is supported by the casing 21 via the outer rotating member 3 and the third bearing 23.

  Furthermore, the axial end surface of the screw shaft 9 is in contact with the outer race of the first bearing 17.

  The thrust force of the ball screw mechanism 15 is input to a first restricting portion 25 that generates a fastening force of the friction clutch 7 and restricts movement of the friction clutch 7 in one axial direction provided on the inner rotating member 5. The thrust reaction force of the ball screw mechanism 15 is input to the second restricting portion 27 that is provided on the inner rotating member 5 and restricts the movement of the screw shaft 9 in the other axial direction via the first bearing 17.

  Further, the first bearing 17 is an angular ball bearing.

  The inner rotating member 5 is supported by the casing 21 via the screw shaft 9 in the radial direction.

  Further, between the screw shaft 9 and the casing 21, a rotation preventing portion 29 that restricts the rotation of the screw shaft 9 is provided.

  As shown in FIG. 2, the power transmission device 1 includes a casing 21, an outer rotating member 3, an inner rotating member 5, a friction clutch 7, a ball screw mechanism 15, an actuator 31, and the like.

  The casing 21 includes a case main body 33 that accommodates each member therein and a cover 35 that closes the case main body 33, and is integrally fixed by a fixing means (not shown) such as a bolt. In addition, the casing 21 is assembled to a carrier whose cover 35 side accommodates a rear differential 119 (see FIG. 1). The casing 21 houses the outer rotating member 3, the inner rotating member 5, the friction clutch 7, the ball screw mechanism 15, the actuator 31, and the like.

  The outer rotating member 3 is formed in a cylindrical shape with a bottom, and is rotatably supported by the casing 21 via a third bearing 23 that is a ball bearing. Further, a seal member 37 is provided between the outer rotating member 3 and the casing 21 in the radial direction so as to partition the inside and the outside of the casing 21, and the seal member 37 is disposed on the outer periphery of the outer rotating member 3. A dust cover 39 is provided to protect against dust. A spline-shaped engaging portion 41 is formed on the cylindrical inner periphery of the outer rotating member 3, and the outer clutch plate of the friction clutch 7 is engaged.

  A connecting member 43 such as a stud bolt is fixed to the bottom wall portion of the outer rotating member 3, and a rotating member (not shown) connected to the propeller shaft 117 (see FIG. 1) via the connecting member 43. The outer rotating member 3 is coupled to be rotatable together. An inner rotary member 5 is disposed on the rotational axis of the outer rotary member 3 so as to be rotatable relative to the outer rotary member 3.

  The inner rotating member 5 is formed in a hollow shape, and can rotate relative to the outer rotating member 3 via a first bearing 17 that is an angular ball bearing, a needle bearing 45, and a second bearing 19 that is a ball bearing on the outer periphery. It is supported by the casing 21. Specifically, the first bearing 17 and the needle bearing 45 support the inner rotating member 5 on the casing 21 via a screw shaft 9 described later in the radial direction, and the second bearing 19 includes the outer rotating member 3 and The inner rotary member 5 is supported on the casing 21 via the third bearing 23.

  A partition wall 47 is provided at a central portion on the axial center side of the inner rotating member 5 as a single member continuous with the inner rotating member 5, and partitions the inside and the outside of the casing 21. In addition, a seal member 49 that partitions the inside and the outside of the casing 21 is provided between the outer circumference of the axial end of the inner rotating member 5 and the radial direction of the casing 21.

  A spline-shaped connecting portion 51 is formed on the inner periphery of one end side in the axial direction of the inner rotating member 5, and a rotating member (not shown) connected to the rear differential 119 (see FIG. 1) side is the inner rotating member 5. And can be integrally rotated. In addition, a spline-shaped connecting portion 53 is formed on the outer periphery on the other end side in the axial direction of the inner rotating member 5, and the inner connecting member 55 is connected to the inner rotating member 5 so as to be integrally rotatable. The movement in the axial direction is restricted by the member 57. A spline-shaped engaging portion 59 is formed on the outer periphery of the inner connecting member 55 and the inner clutch plate of the friction clutch 7 is engaged. The driving force transmitted between the inner rotating member 5 and the outer rotating member 3 is interrupted by the friction clutch 7.

  The friction clutch 7 includes a plurality of outer clutch plates and a plurality of inner clutch plates. The plurality of outer clutch plates are engaged with an engaging portion 41 formed on the inner periphery of the outer rotating member 3 so as to be axially movable and integrally rotatable with the outer rotating member 3. The plurality of inner clutch plates are alternately arranged in the axial direction with respect to the plurality of outer clutch plates, and can be moved in the axial direction by the engaging portions 59 formed on the outer periphery of the inner connecting member 55 and rotate integrally with the inner rotating member 5. Engaged as possible.

  The friction clutch 7 is a multi-plate clutch composed of a plurality of control-type clutch plates capable of intermediate control of transmission torque with sliding friction. The friction clutch 7 is allowed to transmit power between the outer rotating member 3 and the inner rotating member 5 by being applied with a pressing force by the ball screw mechanism 15 and fastened.

  The ball screw mechanism 15 includes a screw shaft 9, a nut 11, and a plurality of balls 13 interposed between the screw shaft 9 and the nut 11. The screw shaft 9 is disposed on the outer periphery of the inner rotary member 5 via the needle bearing 45 and the first bearing 17. Further, the rotation of the screw shaft 9 is restricted by engaging a concave and convex anti-rotation portion 29 formed between the screw shaft 9 and the casing 21. A nut 11 is disposed on the outer peripheral side of the screw shaft 9.

  The nut 11 is arranged on the outer periphery of the screw shaft 9 so as to be rotatable and movable in the axial direction. A spiral groove 61 is formed on a mating surface between the nut 11 and the screw shaft 9 in the radial direction. A plurality of balls 13 are interposed in the spiral groove 61.

  The plurality of balls 13 are rotatably disposed in the spiral groove 61, and the axial movement of the nut 11 by the thrust force generated by the rotation of the nut 11 enables generation of a large thrust force with a small rotational force. . The rotation of the nut 11 is operated by the actuator 31.

  The actuator 31 includes an electric motor 63, a transmission gear member 65, an operation gear member 67, and a pressing member 69. The electric motor 63 is assembled to the outside of the case body 33 of the casing 21, and the motor shaft 71 is disposed inside the casing 21. The electric motor 63 is connected to a controller (not shown) as control means and is controlled by the controller. A transmission gear member 65 is engaged with the motor shaft 71 of the electric motor 63.

  The transmission gear member 65 is rotatably supported via a needle bearing 68 on a pin 66 press-fitted and fixed in the case main body 33 of the casing 21, and includes a large-diameter gear portion 73 and a small-diameter gear portion 75. The large-diameter gear portion 73 meshes with the motor shaft 71 of the electric motor 63 to reduce the rotation of the electric motor 63 and rotate the transmission gear member 65. The small diameter gear portion 75 meshes with the gear portion 77 of the operation gear member 67 and outputs the rotation of the electric motor 63 to the operation gear member 67.

  The operation gear member 67 is axially movable through a spline-shaped connecting portion 79 and is connected to the nut 11 so as to be integrally rotatable. Further, between the operation gear member 67 and the pressing member 69 in the axial direction, the axial movement of the operation gear member 67 is transmitted to the pressing member 69 and the relative rotation between the operation gear member 67 and the pressing member 69 is allowed. A thrust bearing 81 is disposed.

  In this operation gear member 67, the gear portion 77 meshes with the small-diameter gear portion 75 of the transmission gear member 65, and the nut 11 is rotated via the connecting portion 79 by the rotation of the transmission gear member 65. By the rotation of the nut 11, the nut 11 is moved in the axial direction in the connecting direction of the friction clutch 7 by the axial thrust force generated by the ball screw mechanism 15, and the operation gear member 67 is moved in the axial direction in the connecting direction of the friction clutch 7. . Due to the axial movement of the operation gear member 67, the pressing member 69 is axially moved in the connecting direction of the friction clutch 7 via the thrust bearing 81.

  The pressing member 69 is disposed adjacent to the friction clutch 7 in the axial direction, and is engaged with an engaging portion 41 formed on the inner periphery of the outer rotating member 3 so as to be axially movable and integrally rotatable with the outer rotating member 3. Yes. The pressing member 69 is not limited to the outer rotating member 3 and may be engaged with the engaging portion 59 of the inner connecting member 55 that rotates integrally with the inner rotating member 5 so as to be integrally rotatable. The pressing member 69 is moved in the axial direction by the ball screw mechanism 15 and presses the friction clutch 7 to fasten the friction clutch 7. Such a pressing member 69 is always urged in the direction in which the friction clutch 7 is disconnected by the urging member 83 in contact with the sliding washer 82.

  The urging member 83 is made of a disc spring, and is disposed together with the sliding washer 82 between the inner connecting member 55 and the pressing member 69 in the axial direction in a recess on the inner diameter side of the pressing member 69. The urging member 83 constantly urges the pressing member 69 in the direction in which the friction clutch 7 is released. Therefore, when the pressing member 69 is not moved in the connecting direction of the friction clutch 7, the pressing member 69 does not contact the plurality of clutch plates of the friction clutch 7, and the plurality of clutch plates of the friction clutch 7 are Generation of drag torque in the friction clutch 7 can be reduced without being pressed. In this state, the urging member 83 urges the nut 11 through the pressing member 69 in the direction in which the friction clutch 7 is disconnected. For this reason, the urging member 83 positions the nut 11 at the initial position so as to catch the axial backlash of the ball screw mechanism 15, thereby defining the initial position of the ball screw mechanism 15.

  In the power transmission device 1 configured as described above, the nut 11 is rotated via the transmission gear member 65 and the operation gear member 67 by the operation of the electric motor 63. The rotation of the nut 11 generates a thrust force for moving the nut 11 in the axial direction by the ball screw mechanism 15, the nut 11 is moved in the axial direction in the connecting direction of the friction clutch 7, and the operation gear member 67 is moved in the connecting direction of the friction clutch 7. It is moved in the axial direction. The axial movement of the operation gear member 67 causes the pressing member 69 to move in the axial direction in the connecting direction of the friction clutch 7 against the urging force of the urging member 83 via the thrust bearing 81. By the axial movement of the pressing member 69, the plurality of clutch plates of the friction clutch 7 are pressed and the friction clutch 7 is connected. By connecting the friction clutch 7, power can be transmitted between the outer rotating member 3 and the inner rotating member 5.

  As described above, the ball screw mechanism 15 rotates the nut 11 by the operation of the actuator 31, thereby causing the thrust force to move the nut 11 in the connecting direction of the friction clutch 7, which is one side in the axial direction, and the axial movement of the nut 11. This generates a thrust reaction force that moves the screw shaft 9 in the direction of releasing the connection of the friction clutch 7 on the other side in the axial direction.

  As described above, the thrust force of the ball screw mechanism 15 moves the nut 11 in the connecting direction of the friction clutch 7 and generates a fastening force on the friction clutch 7 via the pressing member 69. This thrust force is input to the first restricting portion 25 which is disposed adjacent to the friction clutch 7 and is fixed to the engaging portion 59 of the inner connecting member 55 which is connected to the inner rotating member 5 so as to be integrally rotatable. Then, it is input to the inner rotating member 5 through a regulating member 57 made of a C-shaped clip or the like.

  On the other hand, the thrust reaction force of the ball screw mechanism 15 moves the screw shaft 9 in the direction in which the friction clutch 7 is disconnected. The outer race of the first bearing 17 is in contact with the axial end surface of the screw shaft 9 that is about to be moved in the axial direction by the thrust reaction force. For this reason, the thrust reaction force of the ball screw mechanism 15 is received by the first bearing 17, and the movement of the screw shaft 9 due to the thrust reaction force can be prevented. The thrust reaction force received by the first bearing 17 is input to the second restricting portion 27 which is disposed adjacent to the inner race of the first bearing 17 and is fixed to the outer periphery of the inner rotating member 5. Is done.

  Thus, by receiving the thrust reaction force of the ball screw mechanism 15 by the first bearing 17 that rotatably supports the inner rotation member 5, it is not necessary to provide a thrust bearing or a fixing member for receiving the thrust reaction force. Further, the thrust force and the thrust reaction force of the ball screw mechanism 15 are input to the first restricting portion 25 and the second restricting portion 27 provided on the inner rotating member 5. For this reason, the structure that receives the thrust force and the thrust reaction force of the ball screw mechanism 15 can be completed by the inner rotating member 5 alone.

  In such a power transmission device 1, when the first bearing 17 that supports the inner rotating member 5 moves in one axial direction as the nut 11 rotates and receives thrust force, the first axial shaft 17 generated on the screw shaft 9 moves to the other axial direction. Since the thrust reaction force is received, the first bearing 17 is supported by the radial support of the inner rotating member 5, the support of the screw shaft 9 in the radial direction and the other axial direction, and the thrust reaction force reception of the ball screw mechanism 15. It can have two functions.

  Therefore, in such a power transmission device 1, the first bearing 17 supports the inner rotating member 5 in the radial direction, supports the screw shaft 9 in the radial direction and the other axial direction, and the thrust reaction force of the ball screw mechanism 15. Since it has the function of receiving, it is possible to reduce the number of parts and improve the assemblability.

  Further, since the first bearing 17 is supported by the casing 21 and the second bearing 19 is radially supported by the casing 21 via the outer rotating member 3 and the third bearing 23, The support with the second bearing 19 can be stabilized, and the support of the inner rotary member 5 can be stabilized.

  Further, since the axial end surface of the screw shaft 9 is in contact with the outer race of the first bearing 17, the thrust reaction force of the ball screw mechanism 15 can be reliably received by the first bearing 17.

  The thrust force of the ball screw mechanism 15 is input to the first restricting portion 25 provided on the inner rotating member 5, and the thrust reaction force of the ball screw mechanism 15 is the second restricting portion provided on the inner rotating member 5. 27, the structure that receives the thrust force and the thrust reaction force of the ball screw mechanism 15 can be completed by the inner rotating member 5 alone, and the operation of the ball screw mechanism 15 can be stabilized.

  Furthermore, since the first bearing 17 is an angular ball bearing, the thrust reaction force of the ball screw mechanism 15 can be received by the first bearing 17 while stabilizing the radial support of the inner rotating member 5.

  Moreover, since the inner side rotation member 5 is supported by the casing 21 via the screw shaft 9 in the radial direction, the support of the screw shaft 9 can be stabilized and the support of the ball screw mechanism 15 can be stabilized.

  Furthermore, since the rotation prevention part 29 which regulates rotation of the screw shaft 9 is provided between the screw shaft 9 and the casing 21, the nut 11 arranged on the outer periphery of the screw shaft 9 is reliably rotated. The axial movement of the nut 11 due to the thrust force of the ball screw mechanism 15 can be stabilized.

  In the power transmission device according to the embodiment of the present invention, the friction clutch is fastened via the pressing member by the axial movement of the nut. However, the present invention is not limited thereto, and the nut and the pressing member are provided integrally. The friction clutch may be directly engaged by axial movement of the nut.

  Further, reference numerals 16, 18, 20, 22, and 24 in FIG. 2 are restricting members each formed of a C-shaped clip or the like. By engaging with the engaging grooves, the bearings 17, 19, 23, and the inner rotating member are provided. 5, the axial direction position with the outer side rotation member 3 and the casing 21 is defined.

  Furthermore, the outer rotating member is connected to the propeller shaft so as to be integrally rotatable, and the inner rotating member is connected to the rear differential side so as to be integrally rotatable. However, the outer rotating member can be integrally rotated to the rear differential side. The input / output relationship between the outer rotating member and the inner rotating member may be either, for example, connected and the inner rotating member is connected to the propeller shaft so as to be integrally rotatable.

  Moreover, in the power system of the vehicle to which the power transmission device according to the embodiment of the present invention is applied, the power transmission device is disposed on the propeller shaft. However, the power transmission device is not limited to this, and is disposed on the left and right axles. May be arranged. In this case, the differential gear may be removed and torque transmitted by only the left and right friction clutches.

  Further, a drive source may be disposed on the front wheel side, a power transmission device may be disposed in an FR-based transfer that mainly drives the rear wheel side, and the friction clutch may be used for clutch torque transmission to the drive system on the front wheel side. .

  In addition, the power transmission device may use a friction clutch for differential limitation of a differential device mounted on any of a front differential, a rear differential, a center differential, and the like.

DESCRIPTION OF SYMBOLS 1 ... Power transmission device 3 ... Outer side rotation member (the other rotation member)
5 ... Inner rotating member (one rotating member)
DESCRIPTION OF SYMBOLS 7 ... Friction clutch 9 ... Screw shaft 11 ... Nut 13 ... Ball 15 ... Ball screw mechanism 17 ... 1st bearing 19 ... 2nd bearing 21 ... Casing (fixed system member)
23 ... 3rd bearing 25 ... 1st control part 27 ... 2nd control part 29 ... Anti-rotation part

Claims (7)

A pair of rotating members arranged so as to be rotatable relative to each other, a friction clutch arranged between the pair of rotating members and intermittently transmitting power between the pair of rotating members, a screw shaft and an outer periphery of the screw shaft. A power transmission device comprising a nut provided to be movable in the axial direction, and a ball screw mechanism for applying a pressing force to the friction clutch, comprising a plurality of balls interposed between the screw shaft and the nut,
One rotating member of the pair of rotating members is supported by a stationary system member via a pair of first and second bearings, and the first bearing receives a thrust force as the nut rotates and receives a thrust force. A power transmission device that receives a thrust reaction force in the other axial direction generated in the screw shaft when moving in one direction. The power transmission device according to claim 1,
The power transmission device, wherein the first bearing is supported by the stationary system member, and the second bearing is supported by the stationary system member via the other rotating member and a third bearing. The power transmission device according to claim 1 or 2,
An axial end surface of the screw shaft is in contact with an outer race of the first bearing. The power transmission device according to any one of claims 1 to 3,
The thrust force is input to a first restricting portion that generates a fastening force of the friction clutch and restricts movement of the friction clutch in one axial direction provided on the one rotating member, and the thrust reaction force is The power transmission device is input to a second restricting portion that is provided on the one rotating member and restricts the movement of the screw shaft in the other axial direction via the first bearing. The power transmission device according to any one of claims 1 to 4,
The power transmission device, wherein the first bearing is an angular ball bearing. The power transmission device according to any one of claims 1 to 5,
The power transmission device, wherein the one rotating member is supported by the stationary system member in the radial direction via the screw shaft. The power transmission device according to any one of claims 1 to 6,
Between the screw shaft and the fixed system member, a rotation preventing portion for restricting the rotation of the screw shaft is provided.

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