JP6703920B2 - Power transmission device - Google Patents

Description

The present invention relates to a power transmission device, and particularly to a power transmission device that transmits torque from an input side member to an output side member.

In vehicles such as automobiles, a power transmission device such as a torque converter with a lockup mechanism is provided between an engine and a transmission.

For example, the power transmission device basically includes an input plate, an output plate, and a damper unit arranged between them. Torque is input to the input plate from a member on the engine side such as a flywheel. Further, the output plate is connected to a member on the transmission side. The damper part has a flange and a plurality of coil springs. A part of the input plate engages with the flange, and the torque input to the flange is transmitted to the output plate via the coil spring.

In the power transmission device as described above, the engaging portion between the input plate and the flange is composed of a plurality of claws and a groove into which the claws fit. In such an engaging portion, since there is a gap between the claw and the groove, a rattling noise is generated due to torque fluctuation during power transmission.

Therefore, in the torque converter with a lockup mechanism shown in Patent Document 1, a friction locking mechanism is provided to suppress rattling noise caused by a gap between the lockup piston and the drive plate.

Further, in the device of Patent Document 2, a corrugated plate-like elastic member is arranged at the meshing portion of the teeth to suppress the rattling noise.

JP, 2008-298113, A JP-A-60-159420

In Patent Document 1, a friction locking mechanism is provided to suppress rattling noise, but an axial space for that is required, and a relatively large number of parts is required. Further, in the device of Patent Document 2, a corrugated plate-shaped elastic member is provided, but this type of elastic member is difficult to manufacture, and requires a relatively large arrangement space. Further, the configuration of Patent Document 2 is difficult to apply to an apparatus in which the input plate and the output plate are arranged at positions axially displaced from each other.

An object of the present invention is to be able to suppress rattling noise in a power transmission device with a simple configuration.

(1) A power transmission device according to one aspect of the present invention is a device that transmits torque from a member on an input side to a member on an output side. This power transmission device includes an input side rotating member, an output side rotating member, and a biasing member. The input side rotation member has a first engagement portion, and torque is input from the input side member. The output side rotation member has a second engagement portion that is engageable with the first engagement portion in the rotation direction through a predetermined gap, and is arranged side by side with the input side rotation member in the axial direction. The torque is output to the member. The urging member is arranged between the input-side rotating member and the output-side rotating member, and is capable of elastic deformation equal to or larger than the gap between the first engaging portion and the second engaging portion. And at least one of the output side rotation members is urged in the rotation direction.

In this device, at least one of the input side rotating member and the output side rotating member is biased in the rotational direction by the biasing member.

Here, for example, in a state where no torque is input, the biasing member may be configured to secure a gap between the first engaging portion and the second engaging portion of both rotating members. In this case, when torque is input to the input side rotation member, the input torque is transmitted to the output side rotation member via the biasing member and output to the output side member. When the input torque is increased and the biasing member is elastically deformed to eliminate the gap between the engaging portions, the torque is directly transmitted from the first engaging portion to the second engaging portion.

In addition, both the engaging portions may be brought into contact with each other by the biasing member in a state where no torque is input.

In any case, since the rotation of the input side rotation member and the output side rotation member due to a minute torque fluctuation is restricted by the biasing member, the engagement between the input side rotation member and the output side rotation member arranged side by side in the axial direction is performed. The rattling noise in the part can be suppressed.

(2) Preferably, the biasing member is a torsion spring. The torsion spring includes a coil portion, a first arm extending from one end of the coil portion and having a tip end engaged with the input side rotation member, and a torsion arm extending from the other end of the coil portion and engaging the output side rotation member with the tip end portion. A second arm;

Here, since the biasing member is composed of the torsion spring, the rattling noise can be suppressed with a simple structure. Also, the assembling of the biasing member becomes easy. Further, the specifications can be easily changed by changing the wire diameter of the torsion spring, the arm length, and the like.

(3) Preferably, it further comprises a first support member and a second support member that are arranged at a predetermined interval in the circumferential direction on one of the input side rotation member and the output side rotation member. The biasing member is a torsion spring, and the torsion spring has a first coil portion, a second coil portion, a connecting portion, a first arm, and a second arm. The first coil portion is supported by the first support member. The second coil portion is supported by the second support member. The connecting portion extends between one end of the first coil portion and one end of the second coil portion. The first arm extends from the other end of the first coil portion, and the tip portion thereof engages with the other of the input side rotation member and the output side rotation member. The second arm extends from the other end of the second coil portion and has a tip portion that engages with the other of the input side rotation member and the output side rotation member.

(4) Preferably, one of the first engaging portion and the second engaging portion is an engaging claw extending in the axial direction and having a first width in the circumferential direction. The other of the first engaging portion and the second engaging portion is an engaging groove into which an engaging claw is inserted and which has a second width in the circumferential direction.

(5) A power transmission device according to another aspect of the present invention is a device that transmits torque from an input side member to an output side member. This power transmission device includes an input side rotation member, an output side rotation member, and a torsion spring. The input side rotation member has a first engagement portion, and torque is input from the input side member. The output side rotation member has a second engagement portion that is engageable with the first engagement portion in the rotation direction via a predetermined gap, and outputs torque to the output side member. The torsion spring is arranged between the input-side rotating member and the output-side rotating member, and is capable of elastic deformation equal to or larger than the gap between the first engaging portion and the second engaging portion. At least one of the output side rotation members is biased in the rotation direction.

Here, similarly to the above, the rattling noise can be suppressed with a simple configuration. Moreover, the assembly of the torsion spring becomes easy. Further, the specifications can be easily changed by changing the wire diameter of the torsion spring, the arm length, and the like.

In the present invention as described above, the rattling noise in the power transmission device can be suppressed with a simple configuration.

1 is a sectional configuration diagram of a power transmission device according to a first embodiment of the present invention. The front partial view of FIG. The figure corresponding to FIG. 2 of the modification of 1st Embodiment. The side view of FIG. The figure equivalent to FIG. 2 of 2nd Embodiment of this invention. The figure for demonstrating operation|movement of 2nd Embodiment. The figure for demonstrating operation|movement of 2nd Embodiment. The figure corresponding to FIG. 2 of 3rd Embodiment. The figure equivalent to FIG. 2 of 4th Embodiment.

FIG. 1 is a sectional view of a power transmission device according to an embodiment of the present invention. An engine (not shown) is arranged on the left side of FIG. 1, and a transmission (not shown) is arranged on the right side of the figure. In addition, O-O shown in FIG. 1 is a rotating shaft core for power transmission.

-First embodiment-
[Overall structure of power transmission device]
A power transmission device 1 shown in FIG. 1 is a device for transmitting torque from a housing 2 which is an engine side (input side) member to an input shaft 3 of a transmission which is a transmission side (output side) member. The housing 2 is configured to be rotatable around a rotation axis O and has a first case 5 fixed to a member (not shown) on the engine side, and a second case 6 having an outer peripheral portion fixed to the outer peripheral portion of the first case 5. And have. The housing 2 is filled with lubricating oil, and the power transmission device 1 is a wet type (a type that operates in lubricating oil).

The power transmission device 1 includes an input plate 10 (an example of an input side rotating member), a damper device 11, and a plurality of torsion springs 12 (an example of a biasing member). The damper device 11 includes a flange 14 (an example of an output side rotating member), a plurality of outer peripheral side torsion springs 15 and a plurality of inner peripheral side torsion springs 16, and an output plate 17.

[Input plate 10]
The input plate 10 is fixed to the outer peripheral portion by welding on the inner side surface of the second case 6. The input plate 10 includes an annular, disk-shaped fixing portion 10a and a plurality of claws 10b (first engaging portions) formed by bending a part of the outer peripheral end of the fixing portion 10a toward the engine. ing. The inner peripheral end of the fixed portion 10a is fixed to the inner side surface of the second case 6 as described above. A plurality of mounting holes 10c are formed in the fixed portion 10a at predetermined intervals in the circumferential direction.

Note that FIG. 2 shows a view of the outer peripheral portions of the input plate 10 and the flange 14 of FIG. 1 as viewed from the transmission side.

[Flange 14]
The flange 14 is a disk-shaped plate, and is arranged side by side in the axial direction with the input plate 10 (correctly, the fixed portion 10a of the input plate 10). That is, the flange 14 and the input plate 10 are arranged at different axial positions. As shown in FIG. 2, the flange 14 has a plurality of claw receiving portions 14a and a plurality of outer peripheral side accommodation portions 14b and inner peripheral side accommodation portions 14c, respectively. A plurality of mounting holes 14d are formed between the plurality of claw receiving portions 14a in the circumferential direction.

The plurality of claw receiving portions 14a are formed at positions corresponding to the claws 10b of the input plate 10, protruding radially outward from the outer peripheral end. The claw receiving portion 14a is formed with a groove 14e (second engaging portion) which has a predetermined width in the circumferential direction and whose outer peripheral side is open. The claw 10b of the input plate 10 is inserted into the groove 14e. When the claw 10b is located in the center of the groove 14e, a gap δ is secured on both sides between the claw 10b and the groove 14e.

[Torsion spring 12]
The torsion spring 12 has a coil portion 12a, a first arm 12b, and a second arm 12c. The first arm 12b extends from one end of the coil portion 12a toward the inner peripheral side, and the tip is bent toward the transmission side in the axial direction. Then, the bent portion is inserted into the mounting hole 10c of the input plate 10. The second arm 12c extends from the other end of the coil portion 12a toward the inner peripheral side, and the tip is bent toward the engine side in the axial direction. Then, the bent portion is inserted into the mounting hole 14d of the flange 14.

In this embodiment, the torsion spring 12 and each member are designed so that a gap δ is secured between both sides of the pawl 10b and the groove 14e in a state where no torque is input to the device.

[Output plate 17]
The output plate 17 has a first plate 21 and a second plate 22 that are arranged to face each other in the axial direction. The inner circumferences of the first plate 21 and the second plate 22 are fixed to the outer circumference of the hub 24 by rivets 23. Therefore, the first plate 21 and the second plate 22 cannot move in the axial direction, and cannot rotate relative to each other. The first plate 21 and the second plate 22 are each formed with a plurality of outer peripheral openings 21a, 22a and inner peripheral openings 21b, 22b arranged in the circumferential direction. The openings 21a, 22a, 21b, 22b are arranged at positions corresponding to the outer peripheral side accommodation portion 14b and the inner peripheral side accommodation portion 14c of the flange 14.

[Outer and inner torsion springs 15 and 16]
The outer peripheral side torsion spring 15 is housed in the outer peripheral side housing portion 14b of the flange 14, and is supported in the axial direction and the radial direction by the outer peripheral side openings 21a and 22a of the output plate 17. The inner circumferential side torsion spring 16 is housed in the inner circumferential side housing portion 14c of the flange 14 and is axially and radially supported by the inner circumferential side openings 21b and 22b of the output plate 17. The flange 14 and the output plate 17 are elastically connected in the rotational direction by the torsion springs 15 and 16.

[motion]
When no torque is input to the input plate 10, as shown in FIG. 2, a gap δ is secured between the ends of the claw 10b and the groove 14e by the biasing force of the torsion spring 12. When torque is input to the input plate 10 in such a state, the input plate 10 rotates in the +R direction in FIG. When the input torque is small, the torsion spring 12 is elastically deformed, and the claw 10b does not contact the side surface of the groove 14e.

On the other hand, when a torque of a predetermined magnitude or more is input, the amount of elastic deformation of the torsion spring 12 increases, the claw 10b contacts the side surface of the groove 14e, and the torque is directly input from the input plate 10 to the flange 14. It The torque input to the flange 14 is transmitted to the output plate 17 via the outer peripheral side torsion spring 15 and the inner peripheral side torsion spring 16 and is output to the input shaft 3 of the transmission via the hub 24.

Here, although there is a gap between the claw 10b and the side surface of the groove 14e, the biasing force of the torsion spring 12 becomes a resistance until the two come into contact with each other, so that the impact when the two come into contact with each other is mitigated. Therefore, the rattling noise can be suppressed.

Further, in this device, the torsion spring 12 can obtain a torsional characteristic with low rigidity until the claw 10b comes into contact with the side surface of the groove 14e. For this reason, in addition to the torsional characteristics of relatively high rigidity by the outer peripheral side and inner peripheral side torsion springs 15 and 16, the torsional characteristics of low rigidity can be obtained, and the torsion characteristics can be realized in multiple stages.

[Modification of First Embodiment]
(A) In the above embodiment, the setting is made so that the same gap δ is secured between both sides of the claw 10b and the side surface of the groove 14e in the state where no torque is input. You may set so that an end surface may contact the side surface of the corresponding groove 14e.

(B) The arrangement of the torsion spring 12 is not limited to the above embodiment. For example, as shown in FIG. 3 and FIG. 4 which is a side view thereof, they may be arranged on the inner peripheral side of the input plate 10 ′ and the flange 14 ′. In this example, the claw 10b' of the input plate 10' is engaged with the groove 14a' formed on the outer peripheral surface of the flange 14'. Then, in the torsion spring 12', the first arm 12b' and the second arm 12c' extend from the coil portion 12a' to the outer peripheral side, and the tips thereof are attached to the mounting holes formed in the input plate 10' and the flange 14', respectively. It is installed.

-Second Embodiment-
[Constitution]
FIG. 5 shows a second embodiment. The second embodiment is different from the first embodiment only in the configuration of the input plate 30, the flange 31, and the torsion spring 32, and the other configurations are the same. Therefore, in FIG. 3, only different portions are shown. 5(a) and 5(b) are both front partial views, FIG. 5(a) shows a portion where the torsion spring 32 is mounted, and FIG. 5(b) shows a claw 30b and a flange 31 of the input plate 30. The engaging portion with the groove 31a is shown. Further, FIG. 7C is a side view of FIG.

Like the first embodiment, the input plate 30 is fixed to the outer peripheral portion by welding on the inner side surface of the first case. The input plate 30 is formed in an annular disc shape and has a plurality of protrusions 30a and a plurality of claws 30b as shown in FIGS. The plurality of projecting portions 30a are formed so as to project radially outward from the outer peripheral surface of the input plate 30, and are arranged at predetermined intervals in the circumferential direction. A pair of pins 34 are attached to both ends of the protrusion 30a in the circumferential direction so as to extend along the axial direction. The plurality of claws 30b are formed by bending a part of the outer peripheral end of the input plate 10 toward the engine and extend in the axial direction.

The flange 31 is a disc-shaped plate and is arranged side by side in the axial direction with the input plate 30. A plurality of grooves 31a having a predetermined depth on the inner peripheral side and opening on the outer peripheral side are formed on the outer peripheral end of the flange 31. The claws 30b of the input plate 30 are inserted into the plurality of grooves 31a (see FIG. 5B). When the claw 30b is located at the center of the groove 31a, a gap δ is secured on both sides between the claw 30b and the groove 31a.

The torsion spring 32 is arranged at a position corresponding to, for example, four grooves of the plurality of grooves 31 a of the flange 31. The claw 30b of the input plate 30 is inserted in the remaining groove. The torsion spring 32 has a first coil portion 32a and a second coil portion 32b, a connecting portion 32c, a first arm 32d and a second arm 32e. The first coil portion 32 a is supported by one pin 34 mounted on the protruding portion 30 a of the input plate 30. The second coil portion 32b is supported by the other pin 34. The connecting portion 32c extends in the circumferential direction and connects one end of the first coil portion 32a and one end of the second coil portion 32b. The first arm 32d extends inward from the other end of the first coil portion 32a. The tip of the first arm 32d is in contact with one side surface of the groove 31a of the flange 31. The second arm 32e extends from the other end of the second coil portion 32b toward the inner peripheral side, and the tip end portion thereof is in contact with the other side surface of the groove 31a of the flange 31.

In this embodiment, the torsion spring 32 and each member are designed so that a gap δ is secured between both sides of the claw 30b and the groove 31a when no torque is input to the device.

[motion]
In the second embodiment, as shown in FIG. 6, the first arm 32d and the second arm 32e are set in the groove while the torsion spring 32 is elastically deformed. That is, the torsion spring 32, the input plate 30, and the flange 31 are set between the input plate 30 and the flange 31 with a pre-torque applied in both rotation directions.

Here, until the torque input to the input plate 30 exceeds the pre-torque, the gap δ is secured between both ends of the claw 30b and the groove 31a as in the first embodiment. Then, when a torque exceeding the pre-torque is input, as shown in FIG. 7, the elastic deformation amount of the first arm 32d of the torsion spring 32 increases, and one end surface of the claw 30b abuts the side surface of the groove 31a. Here, torque is directly input from the input plate 30 to the flange 31 via the side surfaces of the claw 30b and the groove 31a. The torque input to the flange 31 is transmitted to the output plate 17 via the outer peripheral side torsion spring 15 and the inner peripheral side torsion spring 16, and is output to the input shaft 3 of the transmission via the hub, as described above.

Here, as in the first embodiment, there is a gap between the claw 30b and the side surface of the groove 31a, but since the biasing force of the torsion spring 32 becomes a resistance until they come into contact with each other, they come into contact with each other. The impact at the time is eased. Therefore, the rattling noise can be suppressed.

In addition, in this device, the torsion spring 32 can obtain a torsional characteristic with low rigidity until the claw 30b contacts the side surface of the groove 31a. For this reason, in addition to the torsional characteristics of relatively high rigidity by the outer peripheral side and inner peripheral side torsion springs 15 and 16, the torsional characteristics of low rigidity can be obtained, and the torsion characteristics can be realized in multiple stages.

[Modification of Second Embodiment]
In the above-described embodiment, the pre-torque is applied to the torsion spring 32 so that the same gap δ is secured between both sides of the claw 30b and the side surface of the groove 31a. However, for example, one end surface of the claw 30b corresponds. You may set so that it may contact|abut the side surface of the groove 31a.

-Third Embodiment-
In the first and second embodiments, an example in which the input plate and the flange are arranged side by side in the axial direction is shown. However, when the input plate and the flange are arranged side by side in the radial direction at the same position in the axial direction. FIG. 8 shows a third embodiment of the present invention.

In this example, the input plate 40 is arranged on the outer peripheral side, and the flange 41 is arranged on the inner peripheral side at the same axial position. The input plate 40 and the flange 41 are annular plate members and are capable of relative rotation.

On the inner peripheral surface of the input plate 40, a plurality of claws 40a protruding inward in the radial direction are formed. On the other hand, on the outer peripheral surface of the flange 41, a groove 41a having a predetermined depth on the inner peripheral side and opening to the outer peripheral side is formed. The groove 41a claw 40a is inserted.

The torsion spring 42 has a coil portion 42a, a first arm 42b, and a second arm 42c. The coil portion 42a is mounted and supported by a pin 43 fixed to the side surface of the flange 41. The first arm 42b extends from one end of the coil portion 42a to the outer peripheral side, and the tip thereof is bent toward the transmission side in the axial direction. The bent portion is inserted into the mounting hole of the input plate 40. The second arm 42c extends laterally from the other end of the coil portion 42a, and has a tip bent toward the engine side in the axial direction. Then, the bent portion is inserted into the mounting hole of the flange 41.

In the third embodiment, similarly to the first embodiment, the torsion spring 42 and each of the torsion springs 42 and the respective springs are arranged so that a gap is secured between both sides of the claw 40a and the groove 41a in a state where no torque is input to the present device. The member is designed.

Also in the third embodiment, it is possible to obtain the same effects as those of the first and second embodiments.

-Fourth Embodiment-
FIG. 9 shows a fourth embodiment. In the fourth embodiment, similarly to the third embodiment, the input plate 50 and the flange 51 are arranged side by side in the radial direction at the same position in the axial direction. The input plate 50 is arranged on the outer peripheral side, and the flange 51 is arranged on the inner peripheral side at the same position in the axial direction. The input plate 50 and the flange 51 are annular plate members and are capable of relative rotation.

On the inner peripheral surface of the input plate 50, a plurality of claws 50a protruding inward in the radial direction are formed. On the other hand, on the outer peripheral surface of the flange 51, a plurality of first grooves 51a and second grooves 51b each having a predetermined depth on the inner peripheral side and opening on the outer peripheral side are formed. The claw 50a is inserted in the first groove 51a. The second groove 51b is wider in the circumferential direction than the first groove 51a, and the first arm 52b and the second arm 52c of the torsion spring 52 described later are inserted therein.

The torsion spring 52 is arranged at a position corresponding to the second groove 51b of the flange 51. The torsion spring 52 has a main body 52a, a first arm 52b, and a second arm 52c. The main body 52a is formed in a substantially V shape, and is supported by the three pins 53a, 53b, 53c. More specifically, the three pins 53a to 53c are arranged side by side in the circumferential direction at predetermined intervals. Both ends of the main body 52a are supported on the outer peripheral sides of the pins 53a and 53c, and the center of the main body 52a is supported on the inner peripheral side of the pins 53b. The first arm 52b extends from one end of the main body 52a to the inner peripheral side. The tip end of the first arm 52b is in contact with one side surface of the second groove 51b of the flange 51. The second arm 52c extends from the other end of the main body portion 52a toward the inner peripheral side, and the tip end portion thereof is in contact with the other side surface of the second groove 51b of the flange 51.

In the fourth embodiment, the torsion spring 52 and each member are designed such that a gap is secured between both sides of the claw 50a and the first groove 51a when no torque is input to the present device. ..

Also in the fourth embodiment, it is possible to obtain the same effects as those of the first and second embodiments.

[Other Embodiments]
The present invention is not limited to the above embodiments, and various changes or modifications can be made without departing from the scope of the present invention.

In the first and second embodiments, the torsion spring is used as the urging member, but other forms of urging member may be used.

1 Power transmission device 10, 30, 40, 50 Input plate 10 (input side rotating member)
10b, 10b', 30b, 40a, 50a Claw (first engaging portion)
12, 12', 32, 42, 52 Torsion spring (biasing member)
12a, 12a', 42a Coil part 12b, 12b', 32d, 42b, 52b 1st arm 12c, 12c', 32e, 42c, 52c 2nd arm 14, 14', 31, 41, 51 Flange (output side rotation member )
14e, 31a, 41a Groove (second engaging portion)
32a 1st coil part 32b 2nd coil part 34,43 pin (support member)
51a First groove (second engaging portion)

Claims (6)

A power transmission device for transmitting torque from an input side member to an output side member,
An input side rotating member having a first engaging portion, to which torque is input from the input side member;
A second engaging portion that is engageable with the first engaging portion in the rotation direction through a predetermined gap is provided, and the second engaging portion is arranged side by side in the axial direction with the input side rotating member, and is provided on the output side member. An output side rotating member that outputs torque,
The input side rotating member is disposed between the input side rotating member and the output side rotating member and is capable of elastic deformation equal to or larger than a gap between the first engaging portion and the second engaging portion. And a biasing member that biases at least one of the output side rotation member in the rotation direction,
Equipped with
The biasing member secures the predetermined gap between the rotation directions of the first engaging portion and the second engaging portion in a state where no torque is input to the input side rotating member, Moreover, it is provided so as to elastically deform when torque is input,
Power transmission device. The biasing member is a torsion spring,
The torsion spring is
Coil part,
A first arm extending from one end of the coil portion and having a tip end engaged with the input side rotation member;
A second arm extending from the other end of the coil portion and having a tip end engaged with the output side rotation member;
Has,
The power transmission device according to claim 1. Further comprising a first support member and a second support member arranged at one of the input side rotation member and the output side rotation member at a predetermined interval in the circumferential direction,
The biasing member is a torsion spring,
The torsion spring is
A first coil portion supported by the first support member;
A second coil portion supported by the second support member;
A connecting portion extending between one end of the first coil portion and one end of the second coil portion;
A first arm extending from the other end of the first coil portion and having a tip end engaged with the other of the input side rotation member and the output side rotation member;
A second arm extending from the other end of the second coil portion and having a tip end engaged with the other of the input side rotation member and the output side rotation member;
Has,
The power transmission device according to claim 1. One of the first engaging portion and the second engaging portion is an engaging claw that extends in the axial direction and has a first width in the circumferential direction,
The other of the first engagement portion and the second engagement portion is an engagement groove into which the engagement claw is inserted and which has a second width in the circumferential direction,
The power transmission device according to claim 1. A power transmission device for transmitting torque from an input side member to an output side member,
An input side rotating member having a first engaging portion, to which torque is input from the input side member;
An output side rotation member that has a second engagement portion that is engageable with the first engagement portion in the rotation direction through a predetermined gap, and outputs torque to the output side member,
The input side rotating member is disposed between the input side rotating member and the output side rotating member and is capable of elastic deformation equal to or larger than a gap between the first engaging portion and the second engaging portion. And a torsion spring for urging at least one of the output side rotation member in the rotation direction,
Equipped with
The biasing member secures the predetermined gap between the rotation directions of the first engaging portion and the second engaging portion in a state where no torque is input to the input side rotating member, Moreover, it is provided so as to elastically deform when torque is input,
Power transmission device. When a torque is input, the relative angle between the first arm and the second arm is less than or equal to the free angle of the torsion spring.
The power transmission device according to claim 2.

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