The present invention relates to a power transmission device that can transmit rotational force of an input member to an output member or interrupt the rotational force as desired.
In general, a power transmission device mounted on a motorcycle is intended to transmit the driving power of an engine to a transmission and a driving wheel or interrupt the driving power as desired and includes an input member, which is coupled toward the engine, an output member, which is coupled toward the transmission and the driving wheel, and a clutch member, which is coupled to the output member. Power is transmitted by bringing a plurality of driving-side clutch discs and driven-side clutch discs provided into press-contact and the transmission of the power is interrupted by releasing the press-contact force thereof.
More specifically, as disclosed in e.g. Patent Literature (PTL) 1, a prior-art power transmission device includes a clutch housing, which rotates with an input member and on which a plurality of driving-side clutch discs are mounted, a plurality of driven-side clutch discs, which are arranged alternately with the driving-side clutch discs of the clutch housing, a clutch member, which is coupled to an output member, and a pressure member, which is attached to the clutch member while being allowed to move in an axial direction of the clutch member and can bring the driving-side clutch discs and the driven-side clutch discs into press-contact or release the press-contact force with the axial movement relative to the clutch member. The prior-art power transmission device is structured to be capable of transmitting the rotational force input to the input member to the output member or interrupting the rotational force by bringing the driving-side clutch discs and the driven-side clutch discs into press-contact or releasing the press-contact force thereof.
Further, a press-contact assisting cam and a back-torque limiting cam are provided in the prior-art power transmission device. The press-contact assisting cam can increase the press-contact force of the driving-side clutch discs and the driven-side clutch discs when the pressure member and the clutch member relatively rotate to move closer to each other if a state in which the rotational force input to the input member can be transmitted to the output member is established. The back-torque limiting cam releases the press-contact force of the driving-side clutch discs and the driven-side clutch discs when the pressure member and the clutch member relatively rotate to move away from each other if the rotational speed of the output member exceeds the rotational speed of the input member.
Further, the prior-art power transmission device includes a resistant member made of a rubber material or the like, which is for generating sliding resistance against the pressure member when the pressure member rotates relative to the clutch member. Accordingly, the resistant member can generate rotational resistance when the pressure member and the clutch member relatively rotate owing to clearance caused between cam surfaces of the press-contact assisting cam or the back-torque limiting cam. Thus, impact or hitting noise accompanied when the cam surfaces abut on each other can be suppressed.
PTL 1:
However, the prior-art power transmission device includes a resistant member made of a rubber material or the like, which is for generating sliding resistance against the pressure member when the pressure member rotates relative to the clutch member. This involves problems of increase in the number of components and need for frequent maintenance, which is caused if the rubber material is worn considerably.
Therefore, the present applicant has focused attention on a clutch spring for adding urging force in an axial direction to a pressure member and reached a review of utilizing the clutch spring to generate rotational resistance when the pressure member rotates relative to the clutch member. That is, utilization of a clutch spring that adds urging force in an axial direction to a pressure member can generate sliding resistance in a rotational direction suitable for the axial urging force and can generate rotational resistance in the rotational direction accurately and easily without employing any other dedicated component of a rubber material or the like.
The present invention has been made in view of such circumstances to provide a power transmission device that can add rotational resistance to the rotation of a pressure member relative to a clutch member by using a clutch spring and can suppress impact or hitting noise accompanied when cam surfaces of a press-contact assisting cam or a back torque limiting cam abut on each other without employing any other dedicated member.
According to the invention of Claim 1, a power transmission device includes: a clutch housing that rotates with an input member and to which a plurality of driving-side clutch discs are attached; a clutch member to which a plurality of driven-side clutch discs are attached and that is coupled to an output member, the driven-side clutch discs being arranged alternately with the driving-side clutch discs of the clutch housing; a pressure member that is attached to the clutch member while being allowed to move in an axial direction of the clutch member and is capable of bringing the driving-side clutch discs and the driven-side clutch discs into press-contact with movement in the axial direction relative to the clutch member or releasing press-contact force thereof; a restricting member that is attached to the clutch member and is capable of restricting movement of the pressure member away from the clutch member by a predetermined dimension; a clutch spring that is attached by one end of the clutch spring abutting on a surface of the restricting member and adds urging force to the pressure member in a direction in which the driving-side clutch discs and the driven-side clutch discs are brought into the press-contact; and a press-contact assisting cam or a back-torque limiting cam, the press-contact assisting cam being capable of increasing the press-contact force of the driving-side clutch discs and the driven-side clutch discs when the pressure member and the clutch member relatively rotate to move closer to each other if a state in which rotational force input to the input member is transmittable to the output member is established, the back-torque limiting cam releasing the press-contact force of the driving-side clutch discs and the driven-side clutch discs when the pressure member and the clutch member relatively rotate to move away from each other if a rotational speed of the output member exceeds a rotational speed of the input member. The power transmission device is capable of transmitting the rotational force input to the input member to the output member or interrupting the rotational force through the press-contact of the driving-side clutch discs and the driven-side clutch discs or the releasing of the press-contact force thereof. In the power transmission device, the clutch spring is accommodated and attached in a depressed portion provided in the pressure member and when the pressure member rotates relative to the clutch member owing to clearance between cam surfaces of the press-contact assisting cam or the back torque limiting cam, the clutch spring is capable of generating rotational resistance by the one end being allowed to slide on a surface of the restricting member while an outer circumferential side surface in the longitudinal direction abuts and is held on an inner circumferential wall surface of the depressed portion. The dimension of the clearance between cam surfaces of the press-contact assisting cam or the back torque limiting cam is set so as to be larger than the value obtained by subtracting the dimension of the outside diameter of the clutch spring from the dimension of the opening diameter of the depressed portion..
According to the invention of Claim 2, a power transmission device includes: a clutch housing that rotates with an input member and to which a plurality of driving-side clutch discs are attached; a clutch member to which a plurality of driven-side clutch discs are attached and that is coupled to an output member, the driven-side clutch discs being arranged alternately with the driving-side clutch discs of the clutch housing; a pressure member that is attached to the clutch member while being allowed to move in an axial direction of the clutch member and is capable of bringing the driving-side clutch discs and the driven-side clutch discs into press-contact with movement in the axial direction relative to the clutch member or releasing press-contact force thereof; a restricting member that is attached to the clutch member and is capable of restricting movement of the pressure member away from the clutch member by a predetermined dimension; a clutch spring that is attached by one end of the clutch spring abutting on a surface of the restricting member and adds urging force to the pressure member in a direction in which the driving-side clutch discs and the driven-side clutch discs are brought into the press-contact; and a press-contact assisting cam or a back-torque limiting cam, the press-contact assisting cam being capable of increasing the press-contact force of the driving-side clutch discs and the driven-side clutch discs when the pressure member and the clutch member relatively rotate to move closer to each other if a state in which rotational force input to the input member is transmittable to the output member is established, the back-torque limiting cam releasing the press-contact force of the driving-side clutch discs and the driven-side clutch discs when the pressure member and the clutch member relatively rotate to move away from each other if a rotational speed of the output member exceeds a rotational speed of the input member. The power transmission device is capable of transmitting the rotational force input to the input member to the output member or interrupting the rotational force through the press-contact of the driving-side clutch discs and the driven-side clutch discs or the releasing of the press-contact force thereof. In the power transmission device, the clutch spring is accommodated and attached in an accommodating member attached to the pressure member and when the pressure member rotates relative to the clutch member owing to clearance between cam surfaces of the press-contact assisting cam or the back torque limiting cam, the clutch spring is capable of generating rotational resistance by the one end being allowed to slide on a surface of the restricting member while an outer circumferential side surface in the longitudinal direction abuts and is held on an inner circumferential wall surface of the accommodating member The dimension of the clearance between cam surfaces of the press-contact assisting cam or the back torque limiting cam is set so as to be larger than the value obtained by subtracting the dimension of the outside diameter of the clutch spring from the dimension of the opening diameter of the accommodating member.
According to the invention of Claim 3, a power transmission device includes: a clutch housing that rotates with an input member and to which a plurality of driving-side clutch discs are attached; a clutch member to which a plurality of driven-side clutch discs are attached and that is coupled to an output member, the driven-side clutch discs being arranged alternately with the driving-side clutch discs of the clutch housing; a pressure member that is attached to the clutch member while being allowed to move in an axial direction of the clutch member and is capable of bringing the driving-side clutch discs and the driven-side clutch discs into press-contact with movement in the axial direction relative to the clutch member or releasing press-contact force thereof; a restricting member that is attached to the clutch member and is capable of restricting movement of the pressure member away from the clutch member by a predetermined dimension; a clutch spring that is attached by one end of the clutch spring abutting on a surface of the restricting member and adds urging force to the pressure member in a direction in which the driving-side clutch discs and the driven-side clutch discs are brought into the press-contact; and a press-contact assisting cam or a back-torque limiting cam, the press-contact assisting cam being capable of increasing the press-contact force of the driving-side clutch discs and the driven-side clutch discs when the pressure member and the clutch member relatively rotate to move closer to each other if a state in which rotational force input to the input member is transmittable to the output member is established, the back-torque limiting cam releasing the press-contact force of the driving-side clutch discs and the driven-side clutch discs when the pressure member and the clutch member relatively rotate to move away from each other if a rotational speed of the output member exceeds a rotational speed of the input member. The power transmission device is capable of transmitting the rotational force input to the input member to the output member or interrupting the rotational force through the press-contact of the driving-side clutch discs and the driven-side clutch discs or the releasing of the press-contact force thereof. In the power transmission device, the clutch spring is inserted and attached in a boss portion provided in the clutch member and when the pressure member rotates relative to the clutch member owing to clearance between cam surfaces of the press-contact assisting cam or the back torque limiting cam, the clutch spring is capable of generating rotational resistance by an other end being allowed to slide on the surface of the spring seat that constitutes a seat surface of the clutch spring while an inner circumferential side surface in the longitudinal direction abuts and is held on an outer circumferential surface of the boss portion. The dimension of the clearance between cam surfaces of the press-contact assisting cam or the back torque limiting cam is set so as to be larger than the value obtained by subtracting the dimension of the diameter of the boss portion from the dimension of the inner diameter of the clutch spring.
According to the invention of Claim 4, in the power transmission device of Claim 1 or 2,the restricting member is formed by hardening a sliding surface on which at least the one end of the clutch spring slides.
According to the invention of Claim 5, in the power transmission device of Claim 3, the spring seat is formed by hardening a sliding surface on which at least the other end of the clutch spring slides.
According to the invention of Claim 1, the clutch spring is accommodated and attached in a depressed portion provided in the pressure member and when the pressure member rotates relative to the clutch member owing to clearance between cam surfaces of the press-contact assisting cam or the back torque limiting cam, the clutch spring is capable of generating rotational resistance by the one end being allowed to slide on a surface of the restricting member while an outer circumferential side surface in the longitudinal direction abuts and is held on an inner circumferential wall surface of the depressed portion. The dimension of the clearance between cam surfaces of the press-contact assisting cam or the back torque limiting cam is set so as to be larger than the value obtained by subtracting the dimension of the outside diameter of the clutch spring from the dimension of the opening diameter of the depressed portion.. Accordingly, rotational resistance can be added to the rotation of the pressure member relative to the clutch member by using the clutch spring, and impact or hitting noise accompanied when the cam surfaces of the press-contact assisting cam or the back torque limiting cam abut on each other can be suppressed without employing any other dedicated member. Furthermore, the inner circumferential wall surface of the depressed portion can prevent the clutch spring from leaning or bending when rotational resistance is generated, and necessary rotational resistance can be generated with higher reliability.
According to the invention of Claim 2, the clutch spring is accommodated and attached in an accommodating member attached to the pressure member and when the pressure member rotates relative to the clutch member owing to clearance between cam surfaces of the press-contact assisting cam or the back torque limiting cam, the clutch spring is capable of generating rotational resistance by the one end being allowed to slide on a surface of the restricting member while an outer circumferential side surface in the longitudinal direction abuts and is held on an inner circumferential wall surface of the accommodating member The dimension of the clearance between cam surfaces of the press-contact assisting cam or the back torque limiting cam is set so as to be larger than the value obtained by subtracting the dimension of the outside diameter of the clutch spring from the dimension of the opening diameter of the accommodating member. Accordingly, the inner circumferential wall surface of the accommodating member can prevent the clutch spring from leaning or bending when rotational resistance is generated, and necessary rotational resistance can be generated with higher reliability.
According to the invention of Claim 3, the clutch spring is inserted and attached in a boss portion provided in the clutch member and when the pressure member rotates relative to the clutch member owing to clearance between cam surfaces of the press-contact assisting cam or the back torque limiting cam, the clutch spring is capable of generating rotational resistance by an other end being allowed to slide on the surface of the spring seat that constitutes a seat surface of the clutch spring while an inner circumferential side surface in the longitudinal direction abuts and is held on an outer circumferential surface of the boss portion. The dimension of the clearance between cam surfaces of the press-contact assisting cam or the back torque limiting cam is set so as to be larger than the value obtained by subtracting the dimension of the diameter of the boss portion from the dimension of the inner diameter of the clutch spring. Accordingly, the outer circumferential surface of the boss portion can prevent the clutch spring from leaning or bending when rotational resistance is generated, and necessary rotational resistance can be generated with higher reliability.
According to the invention of Claim 4, the restricting member is formed by hardening a sliding surface on which at least the one end of the clutch spring slides. Thus, wearing of the sliding surface of the restricting member due to repeated sliding can be suppressed and poor movement caused by the wearing can be prevented.
According to the invention of Claim 5, the spring seat is formed by hardening a sliding surface on which at least the other end of the clutch spring slides. Thus, wearing of the sliding surface of the spring seat due to repeated sliding can be suppressed and poor movement caused by the wearing can be prevented.
Embodiments of the present invention are specifically described below with reference to the drawings.
A power transmission device according to a first embodiment, which is obtainable by die casting, is arranged in a vehicle, such as a two-wheel vehicle, to transmit the driving power of an engine toward a transmission or a driving wheel or interrupt the driving power as desired. As illustrated in
The gear 1 is enabled to rotate about the shaft 3 if the driving force (rotational force) transmitted from the engine is input, and is coupled to the clutch housing 2 with a rivet R or the like. The clutch housing 2 is constituted by a case member like a cylinder that is opened on its right end side in
A member provided in the clutch housing 2 constitutes the clutch member 4. The shaft 3 as an output member passes in an approximately central portion of the clutch member 4, and the clutch member 4 and the shaft 3 are coupled to each other by spline fitting and structured so that if the clutch member 4 rotates, the shaft 3 rotates as well. As illustrated in
More specifically, as illustrated in
The driven-side clutch discs 7 and the driving-side clutch discs 6 are alternately arranged to be stacked, and each clutch disc 6 and each clutch disc 7. that are adjacent are brought into press-contact or the press-contact force thereof is released. That is, both the clutch discs 6 and the clutch discs 7 are allowed to slide in the axial direction of the clutch member 4, and when pressed by the pressure member 5 in the leftward direction in
The pressure member 5 is attached in a position on the right end side of the clutch member 4 in
Thus, when the pressure member 5 moves in the rightward direction, the press-contact force of the driving-side clutch discs 6 and the driven-side clutch discs 7 is released, and the rotational force input to the gear 1 and the clutch housing 2 is interrupted without being transmitted to the clutch member 4 and the shaft 3. That is, the pressure member 5 is structured to be capable of bringing the driving-side clutch discs 6 and the driven-side clutch discs 7 into press-contact or releasing the press-contact force thereof with the axial movement relative to the clutch member 4.
Further, as illustrated in
The press-contact assisting cam can increase the press-contact force of the driving-side clutch discs 6 and the driven-side clutch discs 7 when the pressure member 5 and the clutch member 4 relatively rotate and move closer to each other if a state in which the rotational force input to the clutch housing 2 (the input member) can be transmitted to the shaft 3 (the output member) is established. That is, the press-contact assisting cam is structured so that, if a state in which the rotational force input to the clutch housing 2 (the input member) can be transmitted to the shaft 3 (the output member) is established, the clutch member 4 rotates relative to the pressure member 5 in the direction "a" as indicated in
The back torque limiting cam releases the press-contact force of the driving-side clutch discs 6 and the driven-side clutch discs 7 when the pressure member 5 and the clutch member 4 relatively rotate and move away from each other if the rotational speed of the shaft 3 (the output member) exceeds the rotational speed of the clutch housing 2 (the input member). That is, the back torque limiting cam is structured so that the clutch member 4 rotates relative to the pressure member 5 in the direction "c" as indicated in
The restricting member 10 is constituted by a member like an annular ring (see
In the pressure member 5 according to the present embodiment, as illustrated in
Specifically, as illustrated in
The clutch spring 8 according to the present embodiment is structured so that, when the pressure member 5 rotates relative to the clutch member 4 owing to the clearance between the cam surfaces of the press-contact assisting cam or the back torque limiting cam (in the present embodiment, the clearance caused between the clutch-member-side first cam surface 4a and the pressure-member-side first cam surface 5a or the clearance caused between the clutch-member-side second cam surface 4b and the pressure-member-side second cam surface 5b), the one end 8a slides on the surface 10a of the restricting member 10 while a side surface (the outer circumferential side surface 8c) is held in the longitudinal direction, and rotational resistance can be generated accordingly.
The clutch springs 8 according to the present embodiment are accommodated and attached in the depressed portions 5c provided in the pressure member 5 and are structured so that, when the pressure member 5 rotates relative to the clutch member 4 owing to the press-contact assisting cam or the back torque limiting cam, the outer circumferential side surfaces 8c in the longitudinal direction abut and are held on the inner circumferential wall surfaces 5d of the depressed portions 5c.
For example, as illustrated in
As illustrated in
When the operation of the back torque limiting cam is completed and the set state is recovered, with the rotation of the pressure member 5 relative to the clutch member 4, the clutch-member-side first cam surface 4a and the pressure-member-side first cam surface 5a that constitute the press-contact assisting cam move closer to each other (see
In the clutch spring 8 according to the present embodiment, when the back torque limiting cam operates from the set state (and also, similarly, when the operation of the back torque limiting cam is completed and the set state is recovered), as illustrated in
In particular, in the present embodiment, the dimension t of the clearance between the clutch-member-side second cam surface 4b and the pressure-member-side second cam surface 5b that constitute the back torque limiting cam is set so as to be larger than the value obtained by subtracting the dimension of the outside diameter of the clutch spring 8 (the diameter of the outer circumferential side surface 8c) from the dimension of the opening diameter of the depressed portion 5c. As a result, rotational resistance can be added with higher reliability while leaning or bending of the clutch spring 8 can be suppressed.
Thus, at normal times, the clutch spring 8 according to the present embodiment has a function of adding urging force in the axial direction and bringing the driving-side clutch discs 6 and the driven-side clutch discs 7 into press-contact and a function of generating rotational resistance by the one end 8a sliding on a surface of the restricting member 10 when the pressure member 5 rotates relative to the clutch member 4 owing to the clearance between the cam surfaces of the back torque limiting cam (or the press-contact assisting cam).
Next, a second embodiment of the present invention is described.
Similar to the first embodiment, a power transmission device according to the second embodiment, which is obtainable by die casting, is arranged in a vehicle, such as a two-wheel vehicle, to transmit the driving power of an engine to a transmission or a driving wheel or interrupt the driving power as desired. As illustrated in
In the pressure member 5 according to the present embodiment, as illustrated in
Further, as illustrated in
The restricting member 10 is constituted by a member like an annular ring (see
Similar to the first embodiment, the clutch spring 8 according to the present embodiment is attached so that its one end 8a abuts on a surface 10a of the restricting member 10 and its other end 8b abuts on a bottom surface of the accommodating member 11 or the vicinity of the bottom surface, and is structured to be capable of adding urging force to the pressure member 5 in a direction in which the driving-side clutch discs 6 and the driven-side clutch discs 7 are brought into press-contact (the axial direction). Similar to the first embodiment, the clutch spring 8 is constituted by a coil spring that extends in a spiral from the one end 8a to the other end 8b and structured to have an outer circumferential side surface 8c and an inner circumferential side surface 8d in its longitudinal direction (the direction from the one end 8a toward the other end 8b) (see
The clutch spring 8 according to the present embodiment is structured so that, when the pressure member 5 rotates relative to the clutch member 4 owing to clearance between the cam surfaces of the press-contact assisting cam or the back torque limiting cam (in the present embodiment, the clearance caused between the clutch-member-side first cam surface 4a and the pressure-member-side first cam surface 5a or the clearance caused between the clutch-member-side second cam surface 4b and the accommodating-member-side cam surface 11a), the one end 8a slides on the surface 10a of the restricting member 10 while a side surface (the outer circumferential side surface 8c) is held in the longitudinal direction, and rotational resistance can be generated accordingly.
The clutch springs 8 according to the present embodiment are accommodated and attached in the accommodating member 11 attached in the pressure member 5 and are structured so that, when the pressure member 5 rotates relative to the clutch member 4 owing to the press-contact assisting cam or the back torque limiting cam, the outer circumferential side surfaces 8c in the longitudinal direction abut and are held on the inner circumferential wall surfaces 11b of the accommodating members 11.
For example, as illustrated in
As illustrated in
When the operation of the back torque limiting cam is completed and the set state is recovered, with the rotation of the pressure member 5 relative to the clutch member 4, the clutch-member-side first cam surface 4a and the pressure-member-side first cam surface 5a that constitute the press-contact assisting cam move closer to each other (see
In the clutch spring 8 according to the present embodiment, when the back torque limiting cam operates from the set state (and also, similarly, when the operation of the back torque limiting cam is completed and the set state is recovered), as illustrated in
In particular, in the present embodiment, the dimension t of the clearance between the clutch-member-side second cam surface 4b and the accommodating-member-side cam surface 11a that constitute the back torque limiting cam is set so as to be larger than the value obtained by subtracting the dimension of the outside diameter of the clutch spring 8 (the diameter of the outer circumferential side surface 8c) from the dimension of the opening diameter of the accommodating member 11. As a result, rotational resistance can be added with higher reliability while leaning or bending of the clutch spring 8 can be suppressed.
Thus, at normal times, the clutch spring 8 according to the present embodiment has a function of adding urging force in the axial direction and bringing the driving-side clutch discs 6 and the driven-side clutch discs 7 into press-contact and a function of generating rotational resistance by the one end 8a sliding on the surface 10a of the restricting member 10 when the pressure member 5 rotates relative to the clutch member 4 owing to the clearance between the cam surfaces of the back torque limiting cam (or the press-contact assisting cam).
Next, a third embodiment of the present invention is described.
Similar to the first and second embodiments, a power transmission device according to the third embodiment, which is obtainable by die casting, is arranged in a vehicle, such as a two-wheel vehicle, to transmit the driving power of an engine to a transmission or a driving wheel or interrupt the driving power as desired. As illustrated in
In the clutch member 4 according to the present embodiment, as illustrated in
Further, as illustrated in
The restricting member 10 is constituted by a member like an annular ring (see
Similar to the first and second embodiments, the clutch spring 8 according to the present embodiment is attached so that the one end 8a abuts on the surface 10a of the restricting member 10 and the other end 8b abuts on the spring seat 12, and is structured to be capable of adding urging force to the pressure member 5 in a direction in which the driving-side clutch discs 6 and the driven-side clutch discs 7 are brought into press-contact (the axial direction). Similar to the first and second embodiments, the clutch spring 8 is constituted by a coil spring that extends in a spiral from the one end 8a to the other end 8b and structured to have an outer circumferential side surface 8c and an inner circumferential side surface 8d in its longitudinal direction (the direction from the one end 8a toward the other end 8b) (see
The clutch spring 8 according to the present embodiment is structured so that, when the pressure member 5 rotates relative to the clutch member 4 owing to clearance between the cam surfaces of the press-contact assisting cam or the back torque limiting cam (in the present embodiment, the clearance caused between the clutch-member-side first cam surface 4a and the pressure-member-side first cam surface 5a or the clearance caused between the clutch-member-side second cam surface 4b and the pressure-member-side second cam surface 5b), the other end 8b slides on a surface of the spring seat 12 while a side surface (the inner circumferential side surface 8d) is held in the longitudinal direction, and rotational resistance can be generated accordingly.
The clutch springs 8 according to the present embodiment are inserted and attached in the boss portions 4d provided in the clutch member 4 and are structured so that, when the pressure member 5 rotates relative to the clutch member 4 owing to the press-contact assisting cam or the back torque limiting cam, the inner circumferential side surfaces 8d in the longitudinal direction abut and are held on the outer circumferential surfaces of the boss portions 4d.
For example, as illustrated in
As illustrated in
When the operation of the back torque limiting cam is completed and the set state is recovered, with the rotation of the pressure member 5 relative to the clutch member 4, the clutch-member-side first cam surface 4a and the pressure-member-side first cam surface 5a that constitute the press-contact assisting cam move closer to each other (see
In the clutch spring 8 according to the present embodiment, when the back torque limiting cam operates from the set state (and also, similarly, when the operation of the back torque limiting cam is completed and the set state is recovered), as illustrated in
In particular, in the present embodiment, the dimension t of the clearance between the clutch-member-side second cam surface 4b and the pressure-member-side second cam surface 5b that constitute the back torque limiting cam is set so as to be larger than the value obtained by subtracting the dimension of the outside diameter of the boss portion 4d (the diameter) from the dimension of the inside diameter of the clutch spring 8 (the diameter of the inner circumferential side surface 8d). As a result, rotational resistance can be added with higher reliability while leaning or bending of the clutch spring 8 can be suppressed.
Thus, at normal times, the clutch spring 8 according to the present embodiment has a function of adding urging force in the axial direction and bringing the driving-side clutch discs 6 and the driven-side clutch discs 7 into press-contact and a function of generating rotational resistance by the other end 8b sliding on a surface of the spring seat 12 when the pressure member 5 rotates relative to the clutch member 4 owing to the clearance between the cam surfaces of the back torque limiting cam (or press-contact assisting cam).
According to the above-described first and second embodiments, when the pressure member 5 rotates relative to the clutch member 4 owing to the clearance between cam surfaces of the press-contact assisting cam or the back torque limiting cam, the clutch spring 8 can generate rotational resistance by the one end 8a sliding on the surface 10a of the restricting member 10 while a side surface (the outer circumferential side surface 8c in the first and second embodiments) is held in the longitudinal direction. Thus, the rotational resistance can be added to the rotation of the pressure member 5 relative to the clutch member 4 by using the clutch springs 8 and impact or hitting noise accompanied when the cam surfaces of the press-contact assisting cam or the back torque limiting cam abut on each other can be suppressed without employing any other dedicated member (by utilizing the restricting member 10).
According to the above-described third embodiment, when the pressure member 5 rotates relative to the clutch member 4 owing to the clearance between the cam surfaces of the press-contact assisting cam or the back torque limiting cam, the clutch spring 8 can generate rotational resistance by the other end 8b sliding on a surface of the spring seat 12 while a side surface (the inner circumferential side surface 8d in the third embodiment) is held in the longitudinal direction. Thus, the rotational resistance can be added to the rotation of the pressure member 5 relative to the clutch member 4 by using the clutch springs 8 and impact or hitting noise accompanied when the cam surfaces of the press-contact assisting cam or the back torque limiting cam abut on each other can be suppressed without employing any other dedicated member (by utilizing the spring seats 12).
In particular, according to the above-described first embodiment, the clutch springs 8 are accommodated and attached in the depressed portions 5c provided in the pressure member 5 and when the pressure member 5 rotates relative to the clutch member 4 owing to the press-contact assisting cam or the back torque limiting cam, the outer circumferential side surface 8c in the longitudinal direction abuts and is held on the inner circumferential wall surface 5d of the depressed portion 5c. Accordingly, the inner circumferential wall surface 5d of the depressed portion 5c can prevent the clutch spring 8 from leaning or bending when rotational resistance is generated and necessary rotational resistance can be generated with higher reliability.
According to the above-described second embodiment, the clutch springs 8 are accommodated and attached in the accommodating members 11 attached in the pressure member 5 and when the pressure member 5 rotates relative to the clutch member 4 owing to the press-contact assisting cam or the back torque limiting cam, the outer circumferential side surface 8c in the longitudinal direction abuts and is held on the inner circumferential wall surface 11b of the accommodating member 11. Accordingly, the inner circumferential wall surface 11b of the accommodating member 11 can prevent the clutch spring 8 from leaning or bending when rotational resistance is generated and necessary rotational resistance can be generated with higher reliability.
In addition, according to the above-described third embodiment, the clutch springs 8 are inserted and attached in the boss portions 4d provided in the clutch member 4 and is structured so that when the pressure member 5 rotates relative to the clutch member 4 owing to the press-contact assisting cam or the back torque limiting cam, the inner circumferential side surface 8d in the longitudinal direction abuts and is held on the outer circumferential surface of the boss portion 4d. Accordingly, the outer circumferential surface of the boss portion 4d can prevent the clutch spring 8 from leaning or bending when rotational resistance is generated and necessary rotational resistance can be generated with higher reliability.
Although the present embodiments are described above, the present invention is not limited to these embodiments. For example, regarding the surface 10a of the restricting member 10 or a surface of the spring seat 12, it is preferable that the sliding surface on which at least the one end 8a or the other end 8b of the clutch spring 8 slides be formed by hardening and preferable that carburization or the like be employed as the hardening. Thus, regarding the restricting member 10 or the spring seat 12, forming the sliding surface on which at least the one end 8a or the other end 8b of the clutch spring 8 slides by hardening makes it possible to suppress wearing of the sliding surface of the restricting member 10 or the spring seat 12 due to repeated sliding and prevent poor movement caused by the wearing.
Although both of the press-contact assisting cam and the back-torque limiting cam are provided in the present embodiments, for example, the present.invention may be applied to a power transmission device including the back-torque limiting cam only instead of further including the press-contact assisting cam. In addition, the power transmission device according to the present invention is applicable not only to motorcycles but also to various multiple disc clutch type power transmission devices used for automobiles, three-wheel or four-wheel buggies, or machines for general use.
The present invention is also applicable to, for example, a power transmission device with a different external appearance or with another added function as long as the power transmission device enables that, when the pressure member rotates relative to the clutch member owing to the clearance between the cam surfaces of the press-contact assisting cam or the back torque limiting cam, rotational resistance is generated by one end or the other end sliding on a surface of the restricting member or the spring seat that constitutes a seat surface of the clutch spring while a side surface of the clutch spring is held in the longitudinal direction.
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.