Torque transmission device

Abstract

Provided is a torque transmission device (10) capable of reducing deviation between a design value of transmission torque and actual transmission torque. The torque transmission device is provided with: a drum (13) that is coupled to a shaft (11); outer plates (14) that rotate integrally with the drum; a retainer (17) that is disposed between the outer plates and an intermediate member (20) disposed on the shaft; inner plates (15) that rotate integrally with the retainer and have friction surfaces provided between the inner plates and the outer plates; and a pusher (18) that applies a force for pressing the outer plates and the inner plates in the axial direction. The intermediate member receives, via the retainer, a force applied by the pusher to the outer plates and the inner plates.

Description

Torque Transmission Device

[0001] The present invention relates to a torque transmission device including a friction clutch.

[0002] Prior art relating to a torque transmission device that transmits shaft torque to an intermediate member disposed on the shaft via a multi-plate clutch (friction clutch) is disclosed in Patent Document 1. In the prior art, when an axial force is applied to the friction clutch to engage it, the shaft torque is transmitted to the intermediate member (sprocket) via the drum.

[0003] Japanese Utility Model Application Laid-Open Publication No. 4-9330

[0004] In the prior art, the stopper (retaining ring) fixed to the drum receives an axial force when the friction clutch is engaged, and this force causes the drum that secures the retaining ring to elastically deform, which could result in the actual transmission torque being smaller than the design value of the transmission torque.

[0005] The present invention has been made to solve this problem, and has as its object to provide a torque transmission device that can reduce the deviation between the design value and the actual transmission torque.

[0006] A first aspect for achieving this object comprises a drum connected to a shaft, an outer plate that rotates integrally with the drum, a retainer that is arranged between the outer plate and an intermediate member that is arranged on the shaft, an inner plate that rotates integrally with the retainer and has a friction surface between it and the outer plate, and a pusher that applies a force that presses the outer plate and the inner plate in the axial direction, and the intermediate member receives the force applied by the pusher to the outer plate and the inner plate via the retainer.

[0007] In a second aspect, in the first aspect, the intermediate member includes a cylindrical portion disposed between the shaft and the retainer, and the retainer is fixed to the cylindrical portion.

[0008] In a third aspect, in the first aspect, the intermediate member includes a cylindrical portion disposed between the shaft and the inner plate, and the inner plate is fixed to the cylindrical portion.

[0009] A fourth aspect is the device according to any one of the first to third aspects, further comprising a pressure plate disposed between the pusher and the inner plate, the pressure plate being fixed to the pusher.

[0010] According to the present invention, the intermediate member disposed on the shaft receives the axial force applied by the pusher to the outer plate and the inner plate via the retainer, thereby preventing deformation of the drum and reducing the difference between the design value and the actual transmission torque.

[0011] Fig. 2 is a cross-sectional view of the torque transmission device according to the first embodiment, Fig. 3 is a cross-sectional view of the torque transmission device in an enlarged view of a portion indicated by II in Fig. 1, Fig. 4 is a cross-sectional view of the torque transmission device according to a second embodiment.

[0012] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a cross-sectional view of a torque transmission device 10 according to a first embodiment. The torque transmission device 10 transmits torque from a shaft 11 to an intermediate member 20 via a friction clutch 12.

[0013] Figure 2 is an enlarged cross-sectional view of the torque transmission device 10 of a portion indicated by II in Figure 1. The friction clutch 12 includes a drum 13 that rotates integrally with the shaft 11, an outer plate 14 that rotates integrally with the drum 13, an inner plate 15 that faces the outer plate 14 in the axial direction, a cylindrical portion 16 that rotates integrally with the inner plate 15, and an annular retainer 17 that is disposed between an intermediate member 20 and the outer plate 14.

[0014] The tubular portion 16 is coupled to the base 20a of the intermediate member 20 and extends in the axial direction from the base 20a of the intermediate member 20. In this embodiment, the tubular portion 16 is formed integrally with the intermediate member 20. The radial center portion of the retainer 17 contacts the surface of the base 20a of the intermediate member 20 facing the axial direction. The retainer 17 is fixed to the outer periphery of the tubular portion 16 by interference fit (press fitting).

[0015] The inner plate 15 is fixed to the cylindrical portion 16 by the splines so as to be movable in the axial direction, with its rotation relative to the cylindrical portion 16 being restricted. Because the inner plate 15 is fixed to the cylindrical portion 16, the number of parts can be reduced compared to when a separate part is provided to secure the inner plate 15. The outer plate 14 is fixed to the drum 13 by the splines so as to be movable in the axial direction, with its rotation relative to the drum 13 being restricted.

[0016] The friction clutch 12 is a multi-plate clutch in which two or more friction surfaces are provided between an outer plate 14 and an inner plate 15. A pusher 18 applies an axial force to the outer plate 14 and the inner plate 15 via a pressure plate 19 disposed radially inside the drum 13.

[0017] The intermediate member 20 is rotatably disposed on the shaft 11 by a radial bearing 21 disposed between the shaft 11 and the intermediate member 20. The shaft 11 is provided with a step 22 facing the pusher 18, and an annular spacer 23 is disposed on the step 22. The intermediate member 20 is rotatable relative to the spacer 23 by a thrust bearing 24 disposed between the spacer 23 and the intermediate member 20. In this embodiment, the intermediate member 20 is a sprocket (chain wheel) that transmits power using a chain 25. The chain 25 is stretched between the intermediate member 20 and an output shaft 26 (see FIG. 1 ).

[0018] The pressure mechanism 30 (see FIG. 1) is a mechanism that presses the outer plate 14 and the inner plate 15 together using the pusher 18. The pressure mechanism 30 includes a motor 31 and a reducer (not shown) that amplifies the torque of the motor 31. The torque of the reducer is output to a gear 32. The gear 32 meshes with teeth provided on the outer periphery of a first plate 33.

[0019] The first plate 33 and the second plate 34 are rotatably supported on the outer periphery of the shaft 11. A cam surface (not shown) where the first plate 33 and the second plate 34 face each other in the axial direction has a plurality of grooves formed on the same circumference with a predetermined phase difference as the center of rotation. A ball 35 sandwiched between the cam surface rotates between the first plate 33 and the second plate 34. The ball 35 may be replaced with a roller.

[0020] The spacer 36 has its axial movement limited by a retaining ring 37 fixed to the shaft 11. The second plate 34 has its axial movement limited by the spacer 36. The second plate 34 is rotatable relative to the spacer 36 by a thrust bearing 38 disposed between the spacer 36 and the second plate 34. A thrust bearing 39 is disposed between the first plate 33 and the pusher 18. A spring 40 is disposed between the pusher 18 and the drum 13. The spring 40 stores elastic energy that pushes the pusher 18 axially back against the drum 13.

[0021] When the friction clutch 12 is engaged, the motor 31 is driven to rotate the first plate 33 relative to the second plate 34 via the gear 32. The first plate 33 is pushed by the balls 35, which push the pusher 18 in the axial direction via the thrust bearing 39. The pusher 18 pushes the outer plate 14 and the inner plate 15 in the axial direction via the pressure plate 19 against the elastic force of the spring 40. Because the retainer 17 is disposed between the outer plate 14 and the intermediate member 20, whose axial movement is restricted, the outer plate 14 and the inner plate 15 are sandwiched between the pressure plate 19 and the retainer 17, and a pressing force is applied. The friction force generated between the outer plate 14 and the inner plate 15 engages the friction clutch 12.

[0022] When the friction clutch 12 is engaged, the torque of the shaft 11 is transmitted to the intermediate member 20 via the drum 13, the outer plate 14, the inner plate 15, and the cylindrical portion 16, and is further transmitted to the output shaft 26 via the chain 25. The axial force of the pusher 18 when the friction clutch 12 is engaged is received by the intermediate member 20 arranged on the shaft 11 via the pressure plate 19, the outer plate 14, the inner plate 15, and the retainer 17.

[0023] Because the axial force of the pusher 18 does not act on the drum 13, it is possible to prevent a portion of the axial force of the pusher 18 from being used to elastically deform the drum 13. Because the axial force of the pusher 18 is proportional to the friction force between the outer plate 14 and the inner plate 15, and the transmission torque of the friction clutch 12 is proportional to the friction force between the outer plate 14 and the inner plate 15, it is possible to reduce the difference between the design value of the transmission torque of the friction clutch 12 and the actual transmission torque of the friction clutch 12.

[0024] When the friction clutch 12 is to be disengaged, the motor 31 is driven in the reverse direction to rotate the first plate 33 relative to the second plate 34 via the gear 32, and the pusher 18 and the first plate 33 are pushed back by the spring 40. As the pressing force between the outer plate 14 and the inner plate 15 decreases, the friction force between the outer plate 14 and the inner plate 15 also decreases, and the friction clutch 12 is disengaged.

[0025] Since the force of the pusher 18 when the friction clutch 12 is engaged is received by the base 20a of the intermediate member 20 via the retainer 17, elastic deformation of the intermediate member 20 can be reduced compared to when the force is received at the radial tip of the intermediate member 20. Therefore, the difference between the design value of the transmission torque and the actual transmission torque can be further reduced.

[0026] Because the retainer 17 is fixed to the cylindrical portion 16, which cannot move in the axial direction, the retainer 17 can be prevented from pressing the outer plate 14 and the inner plate 15 together when the friction clutch 12 is disengaged. This prevents the gap between the friction surfaces of the outer plate 14 and the inner plate 15 from becoming smaller when the friction clutch 12 is disengaged, thereby reducing the generation of drag torque.

[0027] A second embodiment will be described with reference to Fig. 3. In the second embodiment, the same parts as those in the first embodiment are designated by the same reference numerals, and the following description will be omitted. Fig. 3 is a cross-sectional view of a torque transmission device 10 in the second embodiment. Like Fig. 2, Fig. 3 is an enlarged view of the part indicated by II in Fig. 1. The torque transmission device 10 includes a friction clutch 41.

[0028] In the friction clutch 41, a pressure plate 19 is connected to the pusher 18. In this embodiment, the pressure plate 19 is connected to the pusher 18 by a screw 42. When the pusher 18 is pushed back and the friction clutch 41 is disengaged, the pressure plate 19 connected to the pusher 18 also moves away from the retainer 17. Since the pressure plate 19 can be prevented from pressing the outer plate 14 and the inner plate 15 together when the friction clutch 41 is disengaged, the gap between the friction surfaces of the outer plate 14 and the inner plate 15 can be prevented from becoming small when the friction clutch 41 is disengaged. This reduces the generation of drag torque.

[0029] The means for connecting the pressure plate 19 to the pusher 18 is not limited to the screw 42. Other means include, for example, mechanically joining the pusher 18 and the pressure plate 19 by plastic deformation of a part of the pusher 18 or the pressure plate 19, or welding.

[0030] The present invention has been described above based on an embodiment, but the present invention is not limited to this embodiment in any way, and it can be easily inferred that various improvements and modifications are possible within the scope of the present invention without departing from the spirit of the present invention.

[0031] In the above embodiment, the pressure mechanism 30 of the friction clutch 12, 41 uses a cam to move the pusher 18, but this is not limiting. Other examples of pressure mechanisms include a hydraulic clutch that moves the pusher 18, an electromagnetic clutch that moves the pusher 18, and an air clutch or vacuum clutch that functions by air pressure or negative air pressure.

[0032] In the embodiment, the intermediate member 20 is described as a sprocket (chain gear) that transmits power using the chain 25, but the present invention is not limited to this. Examples of other intermediate members include a gear that transmits torque between itself and another gear by meshing teeth, and a belt pulley that transmits torque by a belt. In the case of a gear, examples of the intermediate member 20 include a spur gear, a bevel gear, a helical gear, and a screw gear.

[0033] REFERENCE SIGNS LIST 10 Torque transmission device 11 Shaft 13 Drum 14 Outer plate 15 Inner plate 16 Cylindrical portion 17 Retainer 18 Pusher 19 Pressure plate 20 Intermediate member

Claims

1. A torque transmission device that transmits torque of a shaft to an intermediate member placed on the shaft, comprising: a drum connected to the shaft; an outer plate that rotates integrally with the drum; a retainer placed between the outer plate and the intermediate member; an inner plate that rotates integrally with the retainer and has a friction surface between it and the outer plate; and a pusher that applies a force that presses the outer plate and the inner plate in the axial direction, wherein the intermediate member receives the force applied by the pusher to the outer plate and the inner plate via the retainer.

2. A torque transmission device according to claim 1, wherein said intermediate member includes a cylindrical portion disposed between said shaft and said retainer, and said retainer is joined to said cylindrical portion.

3. A torque transmission device according to claim 1, wherein the intermediate member includes a cylindrical portion disposed between the shaft and the inner plate, and the inner plate is fixed to the cylindrical portion.

4. A torque transmission device according to any one of claims 1 to 3, further comprising a pressure plate disposed between said pusher and said inner plate, said pressure plate being connected to said pusher.

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