JP2021169831A - Power transmission device - Google Patents

Abstract

To provide a power transmission device capable of absorbing load torque even when great load torque works during engine start.SOLUTION: A power transmission device 7 includes: an input member 10; an output member 11; a first coil spring 12 to be torsionally deformed according to torque from the input member 10; an impact absorbing member 30 arranged in the state of contacting the first coil spring 12 so as to be deformed in association with the torsional deformation of the first coil spring 12; and a spring clutch 13. The spring clutch 13 has a second coil spring 132, a first hold part 131 arranged on the input member side, and a second hold part 133 arranged on the output member side. When the rotation speed of the first hold part 131 is equal to or higher than the rotation speed of the second hold part 133, the first and second hold parts 131, 133 are integrally rotated, and when the rotation speed of the first hold part 131 is lower than the rotation speed of the second hold part 133, power transmission between the first and second hold parts is cut off.SELECTED DRAWING: Figure 2

Description

The present invention relates to a power transmission device that transmits power from a drive source such as an engine.

Generally, in an automobile, a belt is wound between a pulley fixed to an engine output shaft and a pulley for driving an auxiliary machine such as a cooling fan or an alternator, and the rotation of the engine is controlled by the alternator or the like via the belt. Is communicating to. A one-way clutch is built into the alternator pulley so that the inertial rotation of the alternator does not act as a load on the belt when the engine is decelerating. A transmission device that reduces the load on the belt, improves the belt life, and suppresses the belt slip noise is known.

Conventionally, there is one that uses a clutch spring as the one-way clutch (see Patent Document 1), and the transmission device (decoupler assembly) is a clutch spring when the pulley is accelerated with respect to the hub (output member). Is expanded in diameter and frictionally engaged with the inner surface of the pulley to transmit power, and when the pulley is decelerated with respect to the hub, the clutch spring is reduced in diameter and the frictional engagement is released. Further, in the transmission device, a torsion (coil) spring is interposed between the carrier connected to the output side of the clutch spring and the hub, and the torsion spring is a belt caused by an angular velocity fluctuation of the engine output shaft. Absorbs tension fluctuations (torque fluctuations). Further, a torque limiter is fitted to the torsion spring with a predetermined gap, and when a torque of a predetermined value or more acts on the torsion spring, the deformation of the torsion spring in the outer radial direction comes into contact with the torque limiter. The torque above the predetermined value is directly transmitted from the pulley to the hub without acting on the torsion spring. As a result, the torque acting on the torsion spring is limited to a predetermined value or less, and an overload on the torsion spring is prevented.

Japanese Patent No. 5057997

The torsion spring can absorb the fluctuation of the belt tension by the torsion operation in the load torque range generated during the normal operation. However, in the large load torque range generated when the engine is started or restarted after idling stop, the torsional spring is regulated by the torque limiter, so that the large load torque acts directly on the belt. A large load acts on the belt.

In recent years, the number of idling stop vehicles has tended to increase in order to reduce fuel consumption and exhaust gas. In this case, the number of engine starts (including restart) during the period of automobile use has increased dramatically, and the durability of the belt has improved. Greater attention needs to be paid.

Therefore, an object of the present invention is to provide a power transmission device that can absorb the load torque even if a large load torque is applied when the engine is started, thereby solving the above-mentioned problems. ..

One aspect of the present invention is between an input member to which a rotational driving force from a driving source is input, an output member to which the rotational driving force input to the input member is output, and the input member and the output member. The first coil spring, which is arranged on the power transmission path of the above and is twisted and deformed according to the torque from the input member, and the first coil spring, which is arranged in contact with the first coil spring, is arranged in the twisted deformation of the first coil spring. A shock absorbing member that deforms with it, a second coil spring, a first holding portion arranged on the input member side of the second coil spring on the power transmission path, and the second coil spring on the power transmission path. The spring clutch includes a spring clutch having a second holding portion arranged on the output member side of the above, and the spring clutch is used when the rotation speed of the first holding portion is equal to or higher than the rotation speed of the second holding portion. The first and second holding portions are integrally rotated by the second coil spring being twisted and deformed and frictionally engaged, and the rotation speed of the first holding portion is higher than the rotation speed of the second holding portion. If it is too slow, the power transmission device is characterized in that the frictional engagement is released and the power transmission between the first and second holding portions is cut off.

According to the present invention, when a large load torque from the drive source acts on the input member, such as when the engine is started or when the engine is restarted from the idling stop, the first coil spring is radially more than a predetermined amount corresponding to the torque. However, when it comes into contact with the shock absorbing member, the radial change is regulated and the shock absorbing member is deformed to prevent excessive deformation of the first coil spring and to prevent the first coil spring from being deformed at an early stage. By preventing damage and absorbing a large load torque by the shock absorbing member, it is possible to prevent a shocking load torque from acting on the transmission device and improve durability. Further, by using the spring clutch, it is possible to prevent power transmission from the output member side to the input member side with a simple and quiet configuration.

The front view which shows the outline of the belt type transmission device which drives an auxiliary machine. FIG. 5 is a cross-sectional view showing a pulley device. Exploded view of the pulley device. (A) Plan view of the pulley body, (b) Perspective view of the pulley body. Exploded view of the first coil spring and the first holding member. The rear view of the first holding member. (A) A perspective view of the second coil spring, (b) a front view of the second holding member, and (c) a rear view of the second holding member. (A) A perspective view of the inner ring, (b) a cross-sectional view of the inner ring. Perspective view of the positioning member. The perspective view of the split piece of a shock absorbing member.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a belt-type transmission device 100 that transmits the rotation of the engine output shaft 2 to an auxiliary machine, and the belt-type transmission device 100 has a crank pulley 3 fixed to the output shaft 2 of the engine 1 as a drive source. , A fan pulley 5 connected to a cooling fan (not shown) as an example of an auxiliary machine, a pulley device 7 connected to an alternator 6 as an example of an auxiliary machine, and a belt 9 wound around each of these pulleys. Has. The rotation of the engine output shaft 2 is transmitted from the crank pulley 3 to the fan pulley 5 and the pulley device 7 via the belt 9.

As shown in FIGS. 2 and 3, the pulley device 7 has a pulley body (outer ring) 10 as an input member and an inner ring (output shaft) as an output member to which the rotational driving force input to the pulley body 10 is output. A first coil spring 12 and a spring clutch 13 that functions as a one-way clutch are arranged on a power transmission path between the pulley body 10 and the inner ring 11. Therefore, the torque fluctuation of the rotational driving force from the engine 1 input to the pulley body 10 is absorbed by the first coil spring 12, and is output to the inner ring 11 via the spring clutch 13.

Further, in the normal transmission state in which the rotation speed of the pulley body 10 is equal to or higher than the rotation speed of the inner ring 11, the spring clutch 13 transmits the power input to the pulley body 10 to the inner ring 11, but the rotation of the pulley body 10 In the negative transmission state where the speed is less than the rotation speed of the inner ring 11, the power transmission is cut off to prevent the rotation of the alternator 6 from acting on the belt 9 and the engine 1 through the pulley body 10 to become a load. Hereinafter, the detailed configuration of the pulley device 7 as the transmission device will be described. In the following description, the rotation axis direction of the inner ring 11 and the pulley body 10 arranged coaxially is referred to as a rotation axis direction or simply an axial direction, and in this rotation axis direction, the bottom 101 side of the pulley body 10 is referred to. The first end side and the open end side opposite to the bottom 101 are referred to as the second end side.

The pulley body 10 is a cylindrical member having one end opened as described above, and a winding portion 102 around which a belt 9 having a plurality of V-shaped grooves is formed is formed on the outer peripheral surface thereof. (See also FIG. 4 (a)). Further, in the pulley body 10, a through hole 103 through which the first end portion 11a of the inner ring 11 is inserted is provided at the center of the bottom portion (side wall portion) 101 on the closed side, and the through hole 103 is provided with a slide bearing. By arranging 20, the pulley body 10 is supported so as to be relatively rotatable with the first end portion 11a of the inner ring 11. A retaining member 15 having a diameter larger than that of the through hole 103 is attached to the tip of the first end portion 11a, and the retaining member 15 defines the axial position of the slide bearing 20 and the slide bearing 20. Is prevented from falling out of the inner ring 11.

Further, as shown in FIG. 4B, an engaging groove 101c with which the first end portion 121 of the first coil spring 12 is engaged is formed on the inner side surface 101b of the bottom portion 101 of the pulley body 10. The engagement groove 101c is inclined so that the depth thereof increases from the downstream side to the upstream side in the rotation direction X of the pulley body 10 when the engine is driven, and the first coil is formed in the engagement groove 101c. The pulley body 10 and the first coil spring 12 are connected by engaging the first end portion 121 of the spring 12.

On the other hand, as shown in FIGS. 2 and 3, the second end portion 122 of the first coil spring 12 is connected to the first holding member (first holding portion) 131 of the spring clutch 13. The spring clutch 13 includes the first holding member 131, the second coil spring 132, and the second holding member (second holding portion) 133. As shown in FIG. 5, the first holding member 131 includes a cylindrical portion 131a and a flange portion 131b projecting radially outward from the second end side of the cylindrical portion 131a. An engaging groove 131c with which the second end 122 of the first coil spring 12 described above is engaged is formed on the side surface of the flange 131b on the first end side, and the engaging groove 131c is described above. In the rotation direction X, the depth is inclined so as to become deeper from the upstream side to the downstream side. Therefore, when the first coil spring 12 rotates together with the pulley body 10 in the X direction in the drawing, the second end portion 122 of the first coil spring 12 and the end portion of the engagement groove 131c come into contact with each other, and the first holding member 131 also rotates integrally with the first coil spring 12 in the X direction. The outer diameter of the flange portion 131b is set to be slightly smaller than the inner diameter of the pulley body 10.

Further, the cylindrical portion 131a of the first holding member 131 is configured to form an accommodating space for accommodating the second coil spring 132 inside. More specifically, as shown in FIG. 6, the cylindrical portion 131a has a bottom portion 131e formed on the first end portion side to prevent the second coil spring 132 from protruding toward the first end portion in the axial direction. At the same time, the diameter of the inner peripheral surface 131d is set to be smaller than the outer diameter of the second coil spring 132 in the natural state. That is, the second coil spring 132 is fitted into the inner peripheral surface 131d with a predetermined tightening allowance.

Further, as shown in FIGS. 7A to 7C, the first end portion 132a of the second coil spring 132 is only in sliding contact with the bottom portion 131e and is not connected to the first holding member 131. , The second end portion 132b is connected to the second holding member 133 described above. The second holding member 133 has an engaging groove 133c formed on the side surface 133b on the first end side with which the second end 132b of the second coil spring 132 engages, and the inner diameter side of the engaging groove 133c. The boss portion 133a fitted into the accommodation space of the first holding member 131 projects toward the first end portion side.

Further, on the side surface 133d on the second end side of the second holding member 133, mounting recesses 133e are formed at a plurality of locations in the circumferential direction (three locations in the present embodiment), and these mounting recesses 133e are formed on the inner ring 11. By engaging with the convex portion 11f (see FIG. 8A), the second holding member 133 is adapted to rotate integrally with the inner ring 11.

Therefore, the second coil spring 132 comes into sliding contact with the inner peripheral surface 131d of the cylindrical portion 131a of the first holding member 131, and the rotation speed of the first holding member 131 becomes equal to or higher than the rotation speed of the second holding member 133. In the normal transmission state, the torque transmitted by the frictional force with the inner peripheral surface 131d twists the second coil spring 132 in the direction of expanding the diameter, and the inner peripheral surface 131d of the cylindrical portion 131a of the first holding member 131. And the second coil spring 132 are frictionally engaged with each other. As a result, the first holding member 131, the second holding member 133, and the inner ring 11 rotate integrally, and the driving force input to the spring clutch 13 is output to the inner ring 11.

On the other hand, in the negative transmission state where the rotation speed of the first holding member 131 is less than the rotation speed of the second holding member 133, the second coil spring 132 is moved between the first holding member 131 and the second holding member 133. Twisting in the direction of reducing the diameter, the frictional force between the inner peripheral surface 131d of the cylindrical portion 131a of the first holding member 131 and the second coil spring 132 is reduced. As a result, relative rotation is possible between the first holding member 131 and the second coil spring 132, and the power transmission between the first and second holding members 131 and 133 is cut off.

Further, as shown in FIGS. 8 (a) and 8 (b), the inner ring 11 has through holes 103, 131 g, 133 f and a second through hole 103, 131 g, 133 f and a second formed in the center of the pulley body 10, the first and second holding members 131, 133. A small diameter portion 11c through which the coil spring 132 is inserted is provided, and a large diameter portion 11b is provided on the second end side of the small diameter portion 11c. The large-diameter portion 11b is formed so as to have a larger diameter in the radial direction than the small-diameter portion 11c, and the convex portion 11f provided at a step portion between the small-diameter portion 11c and the large-diameter portion 11b. It is formed so as to have a smaller diameter.

As shown in FIG. 2, a bearing 17 is attached to the large diameter portion 11b, and the bearing 17 is positioned in the axial direction by abutting on the side surface of the convex portion 11f on the second end side. It is positioned. Further, a ring-shaped positioning member 19 is interposed between the bearing 17 and the first holding member 131. The positioning member 19 is press-fitted into the inner peripheral surface of the pulley body 10, and is formed on the side surface 19a on the first end side thereof on the side surface on the second end side of the flange portion 131b as shown in FIG. A concave portion 19b is formed with which the convex portion 131f (see FIG. 6) is engaged.

The positioning member 19 is a pulley while abutting the first coil spring 12 from the second end side in the rotation axis direction with respect to the first holding member 131 so that the first coil spring 12 is compressed by a predetermined dimension in the width direction (rotation axis direction). By press-fitting into the body 10, the position in the rotation axis direction of the first holding member 131 is defined, and thus the position in the rotation axis direction of the first coil spring 12 is defined. The bearing 17 described above is interposed between the large diameter portion 11b of the inner ring 11 and the inner peripheral surface of the positioning member 19, whereby the pulley body 10 is connected to the inner ring 11 on the second end side. It is supported so that it can rotate relative to each other. Further, as shown in FIG. 8B, the inner ring 11 is formed in a hollow shaft shape, and the female screw portion 11d is formed from the second end side. The rotor shaft (not shown) of the alternator 6 is coupled to the female screw 11d. Further, a square hole 11e into which a tool used for attachment to the alternator 6 is inserted is formed on the end surface of the inner ring 11 on the first end side.

In this way, the pulley device 7 arranges the first coil spring 12 on the outer peripheral surface side of the cylindrical portion 131a of the first holding member 131, and arranges the second coil spring 132 on the inner peripheral surface side of the cylindrical portion 131a. The first and second coil springs 12, 132 are arranged so as to overlap each other in the radial direction when viewed from the rotation axis direction. Therefore, the pulley device 7 can be compactly configured in the axial direction. Further, since the one-way clutch that disconnects the power transmission in the negative transmission direction is configured by the spring clutch 13, the quietness is excellent as compared with the case of adopting a one-way clutch such as a ratchet type, and the structure is simple. Moreover, it is possible to reduce the cost.

Next, the shock absorbing member 30 will be described. As shown in FIG. 2, a ring-shaped shock absorbing member 30 made of an elastic member is arranged on the outer diameter side of the first coil spring 12. As shown in FIG. 10, the shock absorbing member 30 is formed by combining a plurality of (two in the present embodiment) divided pieces 301 and 301, and the inner peripheral surface of the hollow portion is a first coil spring. It is arranged in contact with the outer periphery of the twelve. Further, the shock absorbing member 30 is made of an elastic member, urethane having a hardness of, for example, Shore A90 to 95 in the present embodiment, and its outer diameter is larger than the diameter of the inner peripheral surface of the hollow portion of the pulley body 10. It is slightly large and lightly press-fitted and fixed to the inner peripheral surface of the hollow portion of the pulley body 10. Although urethane is taken as an example of the shock absorbing member 30, it may be formed of rubber, synthetic resin, or the like of another material.

The first coil spring 12 is, for example, a coil spring having a rectangular cross section, for example, five turns having a torque capacity larger than that of a circular cross section. It is configured to deform in the direction. The spring constant of the first coil spring 12 in the present embodiment is, for example, 10 [Nm] so as to absorb torque fluctuations during normal operation within a range that does not cause torsional damage even when twisted by torque. It is set to absorb the following torque fluctuations. Further, when the first coil spring 12 is deformed in the diameter expansion direction by a predetermined amount or more due to a large load torque, the shock absorbing member 30 is pressed and deformed according to the load torque acting on the first coil spring 12, and the energy is elastic. Absorb.

Next, the operation of the pulley device (auxiliary machine transmission device) 7 described above will be described. The rotation of the engine output shaft 2 is transmitted to the pulley body 10 of the pulley device 7 via the crank pulley 3 and the belt 9. When the engine 1 is in speed-increasing rotation and the rotation speed of the pulley body 10 is equal to or higher than the rotation speed of the inner ring 11 (at the time of positive transmission from the input side to the output side), the rotation of the pulley body 10 is the first coil spring 12 The torque fluctuation of the engine 1 is absorbed and transmitted to the first holding member 131 of the spring clutch 13. At this time, since the second coil spring 132 is twisted and deformed in the diameter-expanding direction and is frictionally engaged with the inner peripheral surface 131d (see FIG. 6) of the first holding member 131, the spring clutch 13 is the first holding member. The 131, the second coil spring 132, and the second holding member 133 rotate integrally, and the power is transmitted to the alternator 6 via the inner ring 11.

When the engine 1 is in a decelerated state and the rotation speed of the inner ring 11 is larger than the rotation speed of the pulley body 10 (when negative transmission is performed from the output side to the input side), the rotation of the pulley body 10 is the same as that of the first coil spring. It is transmitted to the first holding member 131 of the spring clutch 13 via 12. In this state, the rotation speed of the inner ring 11 (second holding member 133) is higher than the rotation speed of the first holding member 131 due to the inertia of the alternator 6, so that the second coil spring 132 is twisted and deformed in the radial direction, as described above. The frictional engagement of the first holding member 131 with the inner peripheral surface 131d is released. As a result, the inner ring 11 idles, and the rotation of the alternator 6 does not act on the belt 9 through the pulley body 10, and does not act on the belt 9 and the engine 1.

In normal operation in which the vehicle is driven by the rotation of the engine 1, the torque acting on the first coil spring 12 from the pulley body 10 is generally 10 [Nm] or less, and the first coil spring 12 has a load torque. Torque is transmitted to the inner ring 11 via the spring clutch 13 while twisting and deforming accordingly to absorb fluctuations in belt tension. As a result, the belt tension is smoothed, so that it is possible to suppress unnecessary consumption of engine torque and improve fuel efficiency.

When starting the engine, restarting after idling stop, sudden acceleration, etc., a large load torque of about 30 [Nm] generally acts on the pulley device 7. In this state, the rotation (torque) of the pulley body 10 is transmitted to the inner ring 11 via the first coil spring 12 and the spring clutch 13. The large load torque twists and deforms the first coil spring 12 in the diameter-expanding direction, so that the first coil spring 12 compresses and deforms the shock absorbing member 30. As a result, the large load torque is elastically received by the deformation of the shock absorbing member 30, and finally most of the large load torque becomes heat energy due to the deformation of the shock absorbing member 30. As a result, a large load torque at the time of starting, restarting, etc. is absorbed by the shock absorbing member 30, the shock tension acting on the belt 9 can be reduced, and the life of the belt 9 can be extended.

When the large load torque acts, the spring clutch 13 is generally engaged in the normal transmission state. When restarting immediately after idling stop, it is possible that the spring clutch 13 is in a negative transmission state in which it is released. Even in this case, since the first coil spring 12 is on the upstream side of transmission with respect to the spring clutch 13, a large torque due to restart is transmitted to the spring clutch 13 via the first coil spring 12, and the spring clutch 13 At the same time as the engagement, the shock absorbing member 30 is deformed by the diameter expanding operation of the first coil spring 12, and the shock accompanying the large torque is immediately absorbed.

When the rotation speed of the inner ring 11 is larger than the rotation speed of the pulley body 10, the inner ring 11 idles with respect to the pulley body 10. However, when the power generation load of the alternator 6 is large, the frictional coupling between the second coil spring 132 and the first holding member 131 is not instantly broken when the alternator 6 shifts to the idling operation, and the second coil spring 132 holds the first. There is a possibility of momentarily dragging the member 131. When the first holding member 131 is dragged, the second end portion 122 of the first coil spring 12 is largely separated from the end of the engaging groove 131c. If the second end 122 of the first coil spring 12 and the end of the engaging groove 131c of the first holding member 131 rotate relative to each other and are separated from each other, torque transmission is not smoothly performed. However, since the convex portion 131f is formed in the first holding member 131 and the concave portion 19b is formed in the positioning member 19, and the convex portion 131f is accommodated in the concave portion 19b, the convex portion 131f is dragged with respect to the first holding member 131 as described above. Even if a force acts in the direction in which the convex portion 131f is applied, the convex portion 131f is in a state of being caught in the concave portion 19b. As a result, the second end portion 122 of the first coil spring 12 is prevented from being largely separated from the end of the engaging groove 131c.

That is, the concave portion 19b is formed to have a length in the circumferential direction longer than that of the convex portion 131f, and the first holding portion 131 and the positioning member 19 are relatively rotatable in the circumferential direction within a predetermined range. Engaged. As a result, as described above, it is prevented that the second end portion 122 of the first coil spring 12 is largely separated from the end of the engaging groove 131c.

In the above-described embodiment, the first coil spring 12 has a winding direction that deforms in the direction of increasing the diameter by torque. However, a coil spring in the winding direction that deforms in the direction of reducing the diameter by torque is used, and the coil is used. A shock absorbing member may be arranged on the inner peripheral side of the spring. Further, although the second coil spring 132 also has a winding direction that deforms in the direction of increasing the diameter by torque, a coil spring in the winding direction that deforms in the diameter reducing direction by torque may be used. In this case, the first end portion of the second coil spring 132 and the first holding member 131 are connected, and the second coil spring 132 directly engages with the inner ring 11 or frictionally engages with the outer peripheral surface of the second holding member 133. When the second coil spring 132 is frictionally engaged with the inner ring 11, the frictionally engaged portion of the inner ring 11 functions as the second holding portion.

Further, in the above-described embodiment, the first coil spring 12 is arranged on the input member side of the spring clutch 13 on the power transmission path, but is arranged on the output member side of the spring clutch 13 on the power transmission path. You may. Further, although an alternator is applied as an auxiliary machine, other auxiliary machines may be used, and a device driven by a drive source such as an engine or a motor such as an air compressor or a power steering is also defined as an auxiliary machine. A belt is suitable for driving an auxiliary machine, but other transmission devices such as gears and chains may also be used.

1: Drive source (engine) / 7: Power transmission device / 10: Input member / 11: Output member (inner ring) / 12: First coil spring / 13: Spring clutch / 30: Shock absorbing member / 131: First holding Part (first holding member) / 131a: Cylindrical part / 132: Second coil spring / 133: Second holding part (second holding member)

Claims (5)

An input member to which the rotational driving force from the driving source is input, and
An output member that outputs the rotational driving force input to the input member, and
A first coil spring, which is arranged on a power transmission path between the input member and the output member and is twisted and deformed in response to torque from the input member.
A shock absorbing member that is arranged in contact with the first coil spring and deforms with the torsional deformation of the first coil spring.
The second coil spring, the first holding portion arranged on the input member side of the second coil spring on the power transmission path, and the output member side of the second coil spring on the power transmission path were arranged. With a spring clutch having a second holding portion,
In the spring clutch, when the rotation speed of the first holding portion is equal to or higher than the rotation speed of the second holding portion, the second coil spring is twisted and deformed and frictionally engaged with the first and second holding portions. When the holding portion is integrally rotated and the rotation speed of the first holding portion is slower than the rotation speed of the second holding portion, the frictional engagement is released and between the first and second holding portions. Disconnect the power transmission of
A power transmission device characterized by that. The first coil spring is arranged closer to the input member in the power transmission path than the spring clutch.
The power transmission device according to claim 1. The first holding portion includes a cylindrical portion in which the first coil spring is arranged on the outer peripheral surface side and the second coil spring is arranged on the inner peripheral surface side.
The first and second coil springs are arranged so as to overlap in the radial direction when viewed from the rotation axis direction of the input member.
2. The power transmission device according to claim 2. The shock absorbing member is arranged on the radial outer side of the first coil spring.
The first coil spring is twisted and deformed in the diameter expansion direction to compress and deform the shock absorbing member.
The second holding portion is connected so as to rotate integrally with the second coil spring and the output member.
The second coil spring is twisted and deformed in the diameter-expanding direction to frictionally engage with the inner peripheral surface of the first holding portion.
3. The power transmission device according to claim 3. A positioning member is provided that abuts the first holding portion from the side opposite to the first coil spring in the direction opposite to the rotation axis direction and positions the position of the first coil spring in the rotation axis direction.
The first holding portion and the positioning member are engaged with each other in the circumferential direction so as to be relatively rotatable within a predetermined range.
4. The power transmission device according to claim 4.

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