Power transmission device

Abstract

A power transmission device, comprising: a driving rotary member (4) which is rotatable by a force of a driving device; a driven rotary part (7) of a driven device (2) to which the rotation of the driving rotary part (4) can be transmitted; a rotation transmission part (8) which connects the driven rotation part (7) to the driving rotation part (4) and separates the driven rotation part (7) from the driving rotation part (4) as soon as an overload acts on the driven device; and a damping mechanism (9) provided between the rotation transmission part (8) and the driving rotation part (4), wherein the damping mechanism (9) comprises - a plurality of cylindrical sections (15B) which are provided equidistantly in the circumferential direction on the driving rotary part (4), - a plurality of screw threaded parts (19) each provided in the cylindrical portions (15B) and to which one end of the rotation transmission part (8) is fixed, - a plurality of damping rubber parts (16) each provided exclusively in the cylindrical portions (15B) and each fixed to the plurality of screw thread parts (19), and - a plate (21) which connects the plurality of screw thread parts (19) in contact and in an integrated manner.

Description

BACKGROUND OF THE INVENTIONThe present invention relates to a power transmission device used in a compressor for an automobile air conditioner or the like, and more particularly to a power transmission device in which a driving rotary member and a driven rotary member are separated from each other when an overload acts on a driven device.A power transmission device of this type, which is used in a compressor for an automobile air conditioner or the like, includes a damper mechanism. The rotation of a driving rotary member is transmitted to a driven rotary member through the damper mechanism (see JP 2003-56595 A, JP 2001-012492 A, U.S. Pat. No. 6,200,221 B1, Japanese Laid-Open Patent Publications JP 2003-35 321 A, JP 2004-245 274 A, WO 2003 / 040 579 A1, WO 2003 / 040 579 A1 and Japanese Laid-Open Patent Publication JP 2003-28 191 A).An example of a conventional power transmission device will be briefly described with reference to Fig. 11: reference numeral 2 relates to a compressor (driven device) for an automobile air conditioner; 3, a housing for the compressor 2; 4, a disk (driving rotary member) rotatably mounted on a cylindrical portion 3a of the housing 3 through a bearing 5; 6, a rotating shaft of the compressor 2; 7, a hub (driven rotary member) mounted on the rotating shaft 6; 8, a rotatable transmission member connected to the disk 4 to the hub 7; and 9, a damper mechanism connecting the disk 4 to the rotation transmission member 8. These members constitute a power transmission device 1 of the compressor 2.The rotation transmission member 8 includes a substantially round disk-shaped main body 8A and a plurality of fixing portions 8C extending from the outer periphery of the main body 8A equidistantly in a circumferential direction. The rotation transmission member 8 integrally includes the deformable joints 8B extending from the fixing portions 8c along the outer periphery of the main body 8A. The hub 7 and a clamping plate 11 detachably clamp distal ends (connecting cuts) 8D from the connectors 8B. This connects the disk 4 and the hub 7 detachably to each other. The rotation transmission part 8 is usually designed as a spring steel plate.The damper mechanism 9 is for absorbing the shock or torsion fluctuation during power transmission, and includes a damper holding part 15 in which, for example, three damper rubber parts 16 are provided in the damper holding part 15 equidistantly in the circumferential direction or the like. The cushion holding member 15 is disposed in an annular groove 17 of the disk 4 and has three cylindrical portions 18 which in turn receive the respective cushion rubber members 16. Each cushion rubber member 16 is formed cylindrically and is provided in the corresponding cylindrical portion 18 together with a screw thread member 19. The screw thread part 19 forms a flanged cylinder with internal threads, and the cushion rubber part 16 is fixed thereto with its outer periphery. The lock screws 10 fix the corresponding fixing portion 8C of the rotation transmitting member 8 to the front end face of the screw thread member 19 to press the hub-side end face of the cushion rubber member 16 against the inner surface of the disk 16.In this power transmission device 1, the power from the automobile engine (driving device) is transmitted to a rotating shaft 6 through the disk 4, the damper holding member 15, damper rubber members 16, screw thread members 19, the rotation transmission member 8, and the hub 7.The damper mechanism 9 effectively absorbs the torsional vibrations or shock by the damper rubber members 16 transmitted from the disk 4 to the hub 7 during the transmission of power. Consequently, stress acting on the connecting portions 8D of the rotation transmission member 8 due to the torsional fluctuation or the shock during the power transmission is reduced, and the connecting portions 8D do not come out of engagement between the hub 7 and the clamping plate 11.Once an overload occurs in the compressor 2, the rotation of the rotating shaft 6 is suppressed to generate a rotational force equal to or greater than a predetermined magnitude between the disk 4 and the hub 7. This rotational force separates the disk 4 and the hub 7 which were connected by the rotation transmission member 8. More specifically, once the rotation of the rotatable shaft 6 is suppressed, the rotational force generated between the disk 4 and the hub 7 releases the connecting portions 8D of the rotation transmission member 8 from a position between the hub 7 and the clamping plate 11 to separate the disk 4 and the hub 7 from each other. The connecting pieces 8b have then elastically returned to the initial position to move the connecting portions 8D behind the clamping plate 11. Therefore, the rotation transmission member 8 and the hub 7 do not interfere once the connecting portions 8D are released, and the rotation transmission of the disc 4 can be reliably released.In the above-described conventional power transmission device 1, the damper mechanism 9 includes the damper holding part 15, the three damper rubber parts 16 that absorb the torsional fluctuations and shock, and the three screw thread parts 19 that transmit the rotation of the disk 4 to the driven side through the damper rubber parts 16. The screw thread parts 19 are provided in the cushion holding part 15 independently of each other. The holding portions 8C of the rotation transmitting member 8 are fixed to front end surfaces of the screw thread members 19, respectively, to urge the cushion rubber members 16 against the inner surface of the disc 4. In this damper mechanism 9, the sum of the pressures, centering precisions, rectilinearities and the like of the respective damper members 16 deviate from each other due to manufacturing errors or the like, and accordingly, the movements of the respective screw thread members 19 are not always equal. The rotational force from the disc 4 cannot be transmitted uniformly to the screw threaded portions 19. As a result, the loads (rotational forces) acting on the respective holding portions 18 of the rotation transmission member 8 become uneven. A large load is generated by the fixing portion 8C on which a large load acts. In this fixing portion 8C, a crack is formed, which breaks the rotation transmission member 8.SUMMARY OF THE INVENTIONIt is an object of the present invention to provide a power transmission device in which loads acting on the respective joints of the power transmission member are equal, so that no large load is generated even partially by the rotation transmission member. In order to achieve the object described above, according to the invention a force transmission device is provided according to the features of claim 1.Brief Description of the DrawingsFIG. 1 is a front view in partial section of a power transmission device according to the first embodiment of the present invention; FIG. 2 is a sectional view taken along the line II-II in FIG. 1 ; FIG. 3 is a rear view of the power transmission device of FIG. 1 ; FIG. 4A is a front view of the rotation transmission part of FIG. 2 ; FIG. 4B is a side view thereof; FIG. 4C is a state diagram in which the rotation transmission member is mounted on a shaft; FIG. 4D is a state diagram in which the rotation transmission member is connected to a disk; FIGS. 5A and b are front and side views of the clamping plate of FIG. 2, respectively; FIG. 6 is a front view of the panel of FIG. 2 ; FIG. 7 is a sectional view of a power transmission device according to the second embodiment of the present invention; FIG. 8 is a sectional view of a power transmission device according to the third embodiment not belonging to the invention; FIG. 9 is a sectional view of a power transmission device according to the fourth embodiment not belonging to the invention; FIG. 10 is a sectional view of a power transmission device according to the fifth embodiment not belonging to the invention; and FIG. 11 is a sectional view of a conventional power transmission device.DESCRIPTION OF THE PREFERRED EMBODIMENTSA power transmission device according to the first embodiment of the present invention will be described in detail with reference to FIGS. 1 to 6. The same individual components and portions as those of the prior art are denoted by the same reference numerals, and description will be omitted as appropriate. The structure of a power transmission device 20 is almost the same as that of the above-described conventional power transmission device 1, and differs in that a plate 21 is provided on a damper mechanism 9.Referring to FIGS. 1 and 2, a disk 4 serves as a driving rotating member including a disk-shaped plate 4A and an outer cylindrical portion 4B and an inner cylindrical portion 4C which integrally extend from one end side of the disk-shaped plate 4A. A plurality of V-shaped recesses 23 are formed in the outer circumferential surface of the outer cylindrical portion 4B. A power from the automobile engine is transmitted to the outer cylindrical portion 4B through a V belt (not shown). The inner cylindrical portion 4C is rotatably supported in an axis-symmetrical manner on a boss 3A formed on a housing 3 of a compressor 2 through a bearing 5.One end of the rotatable shaft 6 of the compressor 2 extends outside the projection 3A of the housing 3.The hub 7 integrally comprises a boss 7A splined to the shaft end of the rotating end of the shaft 6, and a disc-shaped flange 7B extending radially of the boss 7A. The flange 7B has three receiving holes 26. Rivets 25 are inserted into the respective accommodation bore 26 which is a clamping plate 11 to the rear portion of the flange 7B. Three clamping portions 7C that radially clamp connecting portions 8D of a rotation transmission member 8 together with the clamping plate 11 integrally extend circumferentially equidistantly from the outer periphery of the flange 7B.The rotation transmission member 8 of Fig. 2 and Figs. 4A to 4D interposed between the disc 4 and the hub 7 to detachably connect them is formed by a spring steel plate comprising a substantially completely disc-shaped shape. The rotation transmission member 8 has three joints forming the slits 30 equidistantly in the circumferential direction. Therefore, the rotation transmission member 8 includes an annular main body 8A provided inside the slits 30, and three joints 8B extending around the main body 8A and elastically deformable in the axial direction. The proximal ends of the links 8B (those ends on the rotational direction side of the rotation transmission member 8) form holding portions 8C to be fixed to the damper mechanism 9. The distal ends of the joints 8B form connecting portions 8D detachably fixed by the hub 7 and the clamping plate 11.Each joint 8B is bent, as shown in FIG. 4B, toward the surface side (hub 7 side) by bending at the proximal end 31 aof the joint 8B at a predetermined angle γ, for example, along an oblique bending line 100 on the boundary with respect to the attachment portion 8C connecting an inner edge P to an outer edge Q. Consequently, each connecting portion 8B is inclined in the initial state. The outer edge Q is provided on the opposite side (rear side in the rotational direction) to the inner edge P in consideration of the rotational direction of the rotation transmission part 8. The inclination angle of the bending line 100, that is, the angle that the bending line 100 encloses with a straight line L in the radial direction connecting a center O of the rotation transmission part 8 and the inner edge P is set to an angle β. Bend line 100 is shown as a line for written and pictorial convenience. The connecting pieces 8D are preferably plastically deformed, so that the bending line 100 forms a curve. The connector 8B is bent into two portions, for example, the proximal end 31a of the connector 8B and a boundary 31b between the connector 8B and the connector 8D. The joint 8B is bent at a required angle toward the surface side (hub 7 side) as shown in FIG. 4B so as to be inclined at the initial state. This bending line 101 is coincident with the straight line L 1 (FIG. 4A ), which is a straight line in the radial direction of the rotation transmission member 8 and extends through the inner edge of the connecting portion 8D.Each fixing portion 8C connects the main body 8A to the corresponding joint 8B and forms the same plane as the main body 8A. A fixing hole 32 is formed at the center of the holding portion 8C, through which a fixing screw 10 is inserted. The set screw 10 is screwed with a corresponding screw threaded part 19 of the damper mechanism 9 using the fixing hole 32 to fix the fixing portion 8C to the front end side of the screw threaded part 19.Each connecting portion 8D is disposed opposite to the fixing portion 8C in the rotational direction (the rotational direction of an arrow) of the rotation transmission member 8, and is closely opposed to a fixing portion 8C on the opposite rotational direction side. The connecting portion 8B is bent toward the connecting piece 8B at a required angle in the opposite direction (side of the disk 4) as shown in FIG. 4B. A circumferential engaging portion 33 extends from the center of the rear surface of the connecting portion 8D to increase the connecting force with the clamping plate 11.As soon as the clamping portions 7C of the hub 7 and the clamping portions 11B of the clamping plate 11 clamp the connecting portions 8D of the respective connecting pieces 8D to bring the fixing portions 8D into tight contact with the lower surfaces of the clamping portions 7C, the connecting pieces 8B elastically deform toward the disk 4. Therefore, the main body 8A and the connecting portions 8D substantially deform in parallel to each other as shown in FIGS. 4C and 4D, as soon as the rotation transmitting member 8 is fixed to the hub 7 to increase the distance from the hub 7 to the lower surface of the main body 8A, in other words, to increase the distance D between the main body 8A and the connecting portions 8D. The distance D is an effect obtained by sufficiently reducing a bending angle θ of each of the joint piece 8B and the joint portion 8D. Therefore, the distance D may be larger than in the conventional device. This is achieved by setting the distance D which is substantially equal to or slightly smaller than a distance E between the two opposite sides of the disc 4 and the hub 7.With this arrangement, the amount of elastic deformation (E-D) of each joint 8B in fastening the fastening portion 8C to the disk 4 can be reduced. The bending angle θ formed by the joint 8B and the joint portion 8D mostly remains constant between the initial state of FIG. 4B and a state of FIG. 4D in which the rotation transmission member 8 is fixed to the hub 7.The clamping plate 11 shown in FIGS. 5A and 5B is formed as a spring steel plate or the like in a disc-like shape, and includes a ring-like main body 11A and three clamping portions 11B integrally extending equidistantly from the outer periphery of the main body 11A in the circumferential direction. The main body 11A includes three through holes 34 corresponding to the accommodation holes 26 of the hub 7. Each clamping portion 11B has a locking bore 35 at its center. Each engaging portion 33 extending from the connecting portion 8D of the rotation transmitting member 8 engages with a corresponding locking hole 35 to prevent the connecting portion 8D from being loosened in the circumferential direction.The damper mechanism 9 shown in FIGS. 2, 3 and 6, which absorbs the torsional vibration and shock during operation, is formed in an annular recess 17 surrounded by the disk-shaped plate 4A, outer cylindrical portion 4B and inner cylindrical portion 4C of the disk 4. The damper mechanism 9 includes a damper holding part 15, three damper rubber parts 16 provided in the damper holding part 15 equidistantly in the circumferential direction, three screw thread parts 19 on which the damper rubber parts 16 are respectively mounted, and the plate 21 integrally connecting the screw thread parts 19 and the like.The damper holding part 15 includes a disk-shaped main body 15A, three cylindrical portions 15B integrally extending equidistantly in the circumferential direction from the compressor 2 side of the main body 15A, and ribs 15C reinforcing the cylindrical portions 15B. Rivets 41 fix the main body 15A to the inner surface of the disk-shaped plate 4A of the disk 4.Each cushion rubber part 16 comprises a cylindrical body and is disposed in the cylindrical portion 15B together with the screw thread part 19. The end face of the cushion rubber member 16 facing the hub 7 side is in tight contact with the inner surface of the disk-shaped plate 4A of the disk 4.Each screw thread part 19 comprises a flange-shaped cylindrical body having an internal thread on its inner circumferential surface. The cushion rubber 16 is fixed to the outer periphery of the screw thread portion 19. The end face of the screw thread part 19 extends through a bore in the main body 15A of the cushion holding part 15 and an insertion bore 43 in the disk-shaped plate 4A of the disk 4 to extend slightly outside the disk 4.The set screw 10 fixes the fixing portion 8C of the rotation transmission member 8 to the protruding end face of the screw thread member 19 to urge an end face of the cushion rubber member 16 against the inner surface of the disk-shaped plate 4A.The plate 21 is formed of a substantially rigid metal plate having a ring-like shape with a substantially same size as the main body 15A of the cushion holding part 15, as shown in FIGS. 2 and 6. The plate 21 comprises a central bore 44 through which the inner cylindrical portion 4C of the disc 4 is inserted, and three fixing bores 45. locking screws 46 fix the plate 21 to the rear sides of the flanges of the respective screw thread parts 19 from the rear side 4 of the disc. Therefore, the plate 21 integrally connects the three screw thread parts 19. Therefore, the rotation transmission part 8 and the plate 21 fix the both ends of each screw thread part 19 to prevent disengagement in the rotational direction of each screw thread part.In the construction of the power transmission device 20 having the above-mentioned structure, the damper mechanism is provided in an annular recess 17 of the disk 4, and the rivets 41 fix the damper holding part 15 to the disk 4.Subsequently, the disk 4 is rotatably mounted to the boss 3A of the housing via the bearing 5.Consequently, the hub 7, the rotation transmission member 8 and the clamping plate 11 are integrally mounted on the rotatable shaft 6. In order to integrate the hub 7, the rotation transmission member 8, and the clamping plate 11, the clamping plate 11 and the rotation transmission member 8 are stacked on the lower side of the flange 7B of the hub 7, and the engagement portions 33 of the rotation transmission member 8 engage with the fastening holes 35 of the clamping plate 11. The rivets 25 are inserted and caulked into receiving holes 26 of the hub 7 and the through holes 34 of the clamping plate 11 to connect the hub 7, the rotation transmission member 8, and the clamping plate 11. Consequently, the connecting portions 8D of the rotation transmission member 8 are clamped by the clamping portions 7C of the hub 7 and the clamping portions 11B of the clamping plate 11.After the hub 7 and the clamping plate 11 are fastened, the connecting portions 8D of the rotation transmission member 8 are brought into tight contact with the clamping portions 7C of the hub 7. Once the connecting portions 8D are brought into tight contact with the clamping portions 7C, the connecting pieces 8D of the hub 7 are elastically deformed toward the hub 7 to increase the inclination angle with respect to the main body 8A, thereby separating the connecting portions 8D from the main body 8A. Consequently, the main body 8A and the connecting portions 8D are arranged substantially parallel to each other.In this state, the boss 7A of the hub 7 is spline-fitted to the rotatable shaft 6, and the bolt 24 fixes the boss 7A to the rotatable shaft 6, and then the joints 8B are elastically deformed to displace the main body 8A of the rotation transmitting member 8 toward the compressor 2 and urge the main body 8A against the front end faces of the screw thread members 19. The locking screws 10 are inserted into the fixing holes 32 of the rotation transmitting member 8 and screwed into tapped holes of the screw threaded members 19 to fix the fixing portions 8C of the transmitting member 8 to the screw threaded members 19. The assembly of the power transmission device 20 is then completed.In this power transmission device 20, the power of the motor is transmitted to the rotatable shaft 6 through the disk 4, the damper holding member 15, damper rubber members 16, screw thread members 19, the rotation transmission member 8 and the hub 7.During power transmission, the damper mechanism 9 effectively absorbs the torsional vibrations and shock by the damper rubber members 16 transmitted from the disk 4 to the hub 7. Therefore, the shock during transmission and the torsional fluctuation during transmission, which do not cause overload, reduce the stress acting on the connecting portions 8d of the rotation transmission member 8. Consequently, the connecting portions 8D do not escape from a position between the hub 7 and the clamping plate 11.Since the damper mechanism 9 integrally connects the three screw thread parts 19 to the plate 21, movement or detachment of the individual screw thread parts 19 can be prevented. Consequently, the rotational force from the disc 4 can be uniformly transmitted to the respective screw threaded members 19, and the loads (rotational forces) acting on the fixing portions 8C of the rotation transmitting member 8 can be equal. Therefore, no large stress is generated to a specific fixing portion 8 cwhich forms a crack therein or causes breakage. As a result, the durability of the rotation transmission member 8 can be improved.For example, if an overload acting on the compressor 2 for some reason stops the rotating shaft 6, a force from the automobile engine separates the disk 4 from the hub 7 connected by the rotation transmission member 8. More specifically, even after the rotary shaft 6 stops, the disc 4 tries to continue rotation to continuously drive the rotation transmission member 8. When a pulling force accompanying the rotation exceeds the clamping force of the hub 7 and the clamping plate 11, the connecting portions 8D are released from their position between the hub 7 and the clamping plate 11 and disengage the disc 4 and the hub 7. When the disc 4 and the hub 7 disengage the rotation transmission member 8, the connecting pieces 8B are elastically recessed to restore the rotation transmission member 8 to the original state so that the connecting portions 8D are positioned behind the clamping plate 11. After the connecting portions 8D are released, the rotation transmission member 8 and the hub 7 are no longer engaged with each other, so that the transmission of the rotation on the disc 4 can be surely interrupted.According to the present invention, even if an axial load acts as an impact on the joint 8B of the rotation transmission member 8 during braking or starting, tearing in the proximal end 31 aof the joint 8B and breakage of the proximal end 31 aalong the bending line 100 can be prevented. More specifically, the bending line 100 according to the present invention is an oblique bending line inclined by an angle β with respect to the radially oriented straight line L connecting the center O of the rotation transmission member to the inner edge P of the joint 8B. Consequently, the bend line 100 is formed long, so that the load generated by the proximal end 31 aof the connector 8B can be dispersed along the bend line 100. Accordingly, the value of the maximum stress at the inner edge P reduces. At the inner edge P, no crack forms or the joint 8B will not crack by the crack.Therefore, the reliability and the durability of the power transmission device 20 can be increased.Further, according to the invention, the bending angle θ formed between the joint 8B and the joint portion 8D is set such that the elastic deformation value E - D (FIG. 4C ) of the joint 8B obtained when the rotation transmission member 8 connects the disk 4 and the hub 7 substantially reduces. Therefore, the reaction force of the power transmission part 8 after assembly is also small, so that the axial load against the bearing (not shown) that receives the rotating shaft 6 in an axis-symmetrical manner can be reduced. This can reduce the rotation resistance of the bearing and further improve the durability and reliability of the power transmission device 20.Fig. 7 shows the second embodiment of the present invention. A plate 21 integrally connecting the three screw thread parts 19 of a damper mechanism 9 and a rotation transmission part 8 are stacked one on top of another according to the second embodiment. Set screws 10 fasten and fix the plate 21 and the rotation transmission part 8 with the end-face ends of the screw thread parts 19 to one another. The other structures are identical to those of the above-described embodiment.In this structure, although the screw thread parts 19 have cantilever supporting structures, the joining force of the rotation transmission part 8, the screw thread parts 19 and the plate 21 can be sufficiently increased because the plate 21 is made of a rigid body and interposed between the rotation transmission part 8 and screw thread parts 19. Therefore, movement of the screw thread parts 19 and disengagement of the screw thread parts 19 in the rotational direction can be surely prevented, so that the same effect as in the above-described embodiment can be obtained.Fig. 8 shows a third embodiment of the present invention. This embodiment shows a housing in which a damper mechanism 9 is directly supported in a damper rubber member mounting portion 110 formed in the disk 4. Consequently, the outer surfaces of the cushion rubber 16 are in tight contact with the inner surface of the cushion rubber mounting portion 110. A flange 19A of each screw thread part 19 abuts against a coming-off preventing portion 111 formed by an annular protrusion in the fixing portion 110 so as not to come off toward the hub 7. The rear end of the cushion rubber 16 likewise abuts against the portion 111 to prevent rearward escape of the disc 4.Further, the end of the cushion rubber 16 facing the hub 7 corresponding to the front end extends beyond the end face of the disc 4. A set screw 10 fixes a plate 21 and a main body 8A of the rotation transmission part 8 to the protruding end side of the cushion rubber part 16.The damper mechanism 9 including the above arrangement can protect the plate 21 from wear. In particular, as far as the plate 21 is fixed to a disk 4 according to the embodiment of FIG. 7, the disk 21 does not wear as soon as a cushion rubber 16 is rotated as the load changes to generate friction between the disk 4 and the disk 21. In contrast, no friction occurs and wear of the disk 4 can be prevented if the disk 21 is provided separately from the disk 21, as in the embodiment, because there is no sliding portion between the disk 4 and the disk 21.Fig. 9 shows a fourth embodiment of the present invention. This embodiment is a modification of the third embodiment described above. A cushion rubber 16 is divided in the axial direction to include first and second cylindrical rubber 16A and 16B. The first rubber member 16A is provided in a cushion rubber member mounting portion 110 of a disc 4 and between a flange 19A of a screw threaded member 19 and a coming-off preventing portion 111 to control the back and forth movement. The second rubber member 16B is disposed in a front cushion rubber member mounting portion 110 separately from the rubber member 16A. The rear end of the second rubber member 16B abuts on the coming-off preventing portion 111 to regulate the rearward movement. The front end of the second rubber member 16B extends from the fixing portion toward the disk 4. The other structures are identical to those of the third embodiment described above.In a damper mechanism 9 having the above arrangement, the screw threaded member 19 is held in non-contact with the disc 4 to eliminate a sliding portion. The cushion rubber 16 receives the rotation transmitting member 8 and the screw threaded member 19. Consequently, upon rotation of the cushion rubber member 16 occurring during the load change, no friction acts between the screw thread member 19 and the disc 4.Fig. 10 shows a fifth embodiment of the present invention. This embodiment is a modification of the third embodiment described above. In place of the set screw, a pin 120 is used as a fixing means for fixing a rotation transmitting member 8 and a plate 21 to a cushion rubber member 16. The cushion rubber 16 has a cylindrical body having an open front end and a closed rear end. The pin 120 has annular recesses 121 and projections 122 in its outer periphery supported by the cushion rubber member 16. This prevents the pin 120 from coming off the cushion rubber 16.In a damper mechanism 9 having the above-described arrangement, the screw threaded member 19 required when the set screw 10 is used can be omitted because the pin 120 can be directly inserted into the damper rubber member 16, so that the number of components is reduced.Each of the above-described embodiments includes a housing in which the fixing portions 8C of the rotation transmission member 8 to the disk 4 serving as the driving rotation member are fixed, and the connecting portions 8D to the hub 7 serving as the driving rotation member are connected. However, the present invention is not limited to this at all. The fastening portions 8 cmay be fixed to the hub 7, and the clamping plate 11 may be detachably connected to the connecting portions 8D to the disc 4.Each of the above-described embodiments shows a case in which the distance D (FIG. 4C ) from the main body 8A to each connecting portion 8D is formed slightly smaller than the distance E between the opposed surfaces of the disk 4 and the hub 7, and the rotation transmission member 8 is fixed to the hub 7. However, the present invention is not limited thereto. The distance D may be slightly greater than the distance E (D>E). In this case, the direction of the axial load acting on the rotating shaft 6 is opposite to the above-described embodiments.As stated above, the plate integrally connects the plurality of cutting screw members according to the present invention to each other to regulate the movement of the individual cutting screw members. Therefore, the rotational forces to be transmitted from the driving rotational member to the respective screw thread members become uniform to uniformize the loads to be applied to the respective joints of the rotation transmission member. Therefore, the loads generated in the respective fixing portions of the rotation transmission member become equal. No large load is generated by individual fixing portions causing a crack or a fracture in the fixing portion. This improves the durability of the rotation transmission member.Once the plate is fixed to the back surfaces of the cutting screw parts so that the rotation transmission part and the plate support the both ends of each screw thread part, detachment of the cutting screw parts in the rotation direction can be surely prevented when a load is applied or during starting. If the plate is fixed to the front surfaces of the screw thread parts, the joining force of the cutting thread parts and the plate increases. Consequently, loosening of the cutting thread parts can be prevented even when the cutting thread parts are supported in a cantilever manner.Since the plate is not in contact with the driving rotation member, there is no sliding portion between the rotation transmission member and the driving rotation member. This can prevent wear of the rotation transmission part and the driving rotation part and a reduction in strength caused by wear. Since the rotation transmitting member and the cutting screw member are held by the cushion rubber member to space them from the driving rotation member, there is no sliding portion between the rotation transmitting member, the screw thread member and the driving rotation member. Consequently, wear of the rotation transmission part, the screw thread part, and the driving rotation part can be prevented.Since the joint is bent such that the bend line is inclined to increase the length of the bend line, the stress along the bend line splits to moderate stress concentrations. Therefore, a crack in the proximal end of the connector or a breakage along the bending line can be prevented.By the connection portion of the rotation transmission member being held clamped by the driven rotation member and the clamping plate, the bending angle of the connection piece and the fixing portion is designed such that the distance between the main body and the connection portion is substantially equal to the distance between the driving rotation member and the driven rotation member. If the fixing portion is fixed to the driving rotation member, the joint is slightly elastically deformed. The axial load acting on the bearing that axis-symmetrically receives the rotating shaft and axis-symmetrically receives the driving rotating member decreases. This can reduce the rotation resistance of the bearings. If the connecting piece is slightly elastically deformed, the rotation transmission part can be mounted on the driving rotation part with a low handling force. This facilitates the assembly of the rotation transmission part to the driving rotation part.

Claims

A power transmission device, comprising: a driving rotation member (4) rotatable by a force of a driving device; a driven rotation member (7) of a driven device (2) on which the rotation of the driving rotation member (4) is transmittable; a rotation transmission member (8) connecting the driven rotation member (7) to the driving rotation member (4) and disconnecting the driven rotation member (7) from the driving rotation member (4) when an overload acts on the driven device; and a damping mechanism (9) provided between the rotation transmission member (8) and the driving rotation member (4), the damping mechanism (9) comprising: a plurality of cylindrical portions (15B) provided on the driving rotation member (4) equidistantly in the circumferential direction; a plurality of screw thread members (19) provided in the cylindrical portions (15B), respectively, and to which one end of the rotation transmission member (8) is fixed; a plurality of damping rubber members (16) provided in the cylindrical portions (15B), respectively, and fixed to the plurality of screw thread members (19), respectively; and a plate (21) that connects the plurality of screw thread members (19) to each other in contact and integrated manner.The device according to claim 1, wherein the plate (21) is fixed to back surfaces of the plurality of screw thread parts (19).The device according to claim 1, wherein the plate (21) is fixed to front surfaces of the plurality of screw thread parts (19).The device according to claim 1, wherein the rotation transmission member (8) includes an annular main body (8A), a plurality of fixing portions (8C) protruding equidistantly in the circumferential direction from an outer periphery of the main body (8A) and fixed to the plurality of screw thread members (19), a plurality of joints (8B) extending from the plurality of fixing portions (8C) respectively along the outer periphery of the main body (8A) and bent in a direction perpendicular to a surface of the main body (8A) and elastically deformable in the axial direction, and a joint portion (8D), extending from a distal end of each of the plurality of links (8B) and detachably clamped by the driven rotary member (7) and a clamping plate (11), and a proximal end at each of the links (8B) bent along an oblique line so that an inner edge corresponds to a bending line (100) having a front side in the rotational direction and an outer edge thereof corresponds to a rear side in the rotational direction.The device according to claim 1, wherein the rotation transmission part (8) includes an annular main body (8A) that includes a disk-like shape and has a plurality of joints that form slits (30) equidistantly in the circumferential direction on a side near an outer circumference, and a plurality of joints (8B) that extend from the main body (8A) to surround an outer circumference of the main body (8A) and are elastically deformable in the axial direction, each of the joints (8B) including a proximal end side fixing portion (8C) that is inclined with respect to a surface of the main body (8A) and fixed to a part corresponding to the plurality of screw thread parts (19) and includes a distal end side connecting portion (8D), which is inclined in a direction opposite to the link (8B) and detachably fixed by the driven rotary member (7) and a clamping plate (11), wherein the connecting portion (8D) is formed by bending toward the main body (8A), and wherein a bending angle of the connecting portion (8D) is set such that a distance between the main body (8A) and the connecting portion (8D) becomes equal to a distance between the driving rotary member (4) and the driven rotary member (7) once the driven rotary member (7) and the clamping plate (11) are clamped to the connecting portion (8d).

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