Source: http://www.google.com/patents/US7395912?dq=5787449
Timestamp: 2016-07-28 07:01:24
Document Index: 323515196

Matched Legal Cases: ['Application No. 2005', 'Application No. 2005', 'art 61', 'art 61', 'art 61', 'art 62', 'art 62', 'art 61', 'art 113', 'art 60', 'art 61', 'art 62', 'art 61', 'art 62', 'art 61', 'art 62']

Patent US7395912 - Operating assist device for vehicle clutch - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA clutch mechanism includes a friction clutch with a clutch spring, a clutch lever connected to the friction clutch via clutch wires and being manually operable against the urging force of the clutch spring, and a clutch assisting device. The clutch assist device has an assist mechanism having an auxiliary...http://www.google.com/patents/US7395912?utm_source=gb-gplus-sharePatent US7395912 - Operating assist device for vehicle clutchAdvanced Patent SearchPublication numberUS7395912 B2Publication typeGrantApplication numberUS 11/328,714Publication dateJul 8, 2008Filing dateJan 9, 2006Priority dateJan 7, 2005Fee statusPaidAlso published asEP1679449A1, EP1679449B1, US20060169561Publication number11328714, 328714, US 7395912 B2, US 7395912B2, US-B2-7395912, US7395912 B2, US7395912B2InventorsAkifumi Ooishi, Yousuke IshidaOriginal AssigneeYamaha Hatsudoki Kabushiki KaishaExport CitationBiBTeX, EndNote, RefManPatent Citations (19), Non-Patent Citations (1), Referenced by (12), Classifications (5), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetOperating assist device for vehicle clutch
US 7395912 B2Abstract
A clutch mechanism includes a friction clutch with a clutch spring, a clutch lever connected to the friction clutch via clutch wires and being manually operable against the urging force of the clutch spring, and a clutch assisting device. The clutch assist device has an assist mechanism having an auxiliary force member (e.g., a spring) that urges the clutch wires in such a direction as to disengage the friction clutch while the clutch lever is moved from a disengage start position, where the clutch lever receives the reactive force of the clutch spring, to a disengaged position, where the disengagement of the friction clutch is completed. The assist mechanism maintains the urging force of the auxiliary spring applied to the clutch wires within a fixed range while the clutch lever is shifted from the midpoint between the disengage start position and the disengaged position to the disengage position. The clutch assist device reduces the manual force required to operate the clutch while preserving the operational feel of the clutch lever when moving the lever from a released position to a half clutched position, to a full clutch position.
1. A clutch mechanism for a vehicle comprising a clutch assist device operating between a clutch and a clutch operator, the clutch operator being connected to the clutch by a transmitting component, the clutch including a clutch element being biased by a clutch spring toward an engaged position and being movable by the clutch operator and the transmitting component from the engaged position to a disengaged position, the clutch assist device comprising an auxiliary force member which is disposed relative to the transmitting component, at least when the clutch operator is moved to disengage the clutch element, to apply an assist force to the transmitting component in such a direction as to assist disengaging the clutch element while the clutch operator is moved from a disengage start position, at which point the clutch operator works against the bias of the clutch spring, to a disengaged position where the clutch element is in the disengaged position, wherein the assist force of the auxiliary force member applied to the transmitting component is maintained within a fixed range while the clutch operator is moved from an intermediate position, lying between the disengage start position and the disengaged position, to the disengage position, wherein the clutch has a clutch release mechanism, and the transmitting component has a first clutch wire connected to the clutch operator and a second clutch wire connected to the clutch release mechanism, and wherein the clutch assist device is disposed between the first clutch wire and the second clutch wire.
2. The clutch mechanism of claim 1, wherein the auxiliary force member urges the transmitting component toward a position corresponding to the engaged position of the clutch when the clutch operator is in a return position, and the direction of the assist force applied to the transmitting component is changed from such a direction to a direction assisting disengagement of the clutch when the clutch operator is moved toward the disengaged position from the return position through the disengage start position, additionally comprising a canceling force member, which applies an urging force to cancel the urging force of the auxiliary force member that is applied to the transmitting component when the clutch operator is initially moved from the return position toward the disengage start position.
3. The clutch operation assisting device of claim 1, wherein the clutch assist device is configured to directly transmit displacement of the first clutch wire to the second clutch wire such that the displacements of the first and second clutch wires are equal to each other at the time when the clutch operator is actuated.
4. A clutch assist device operating between a clutch and a manual clutch operator, the clutch operator being connected to the clutch by a transmitting component, the clutch including a clutch element being biased by a clutch spring toward an engaged position and being movable by the clutch operator and the transmitting component from the engaged position to a disengaged position, the clutch assist device comprising:
a movable member movable in synchronization with the transmitting component,
auxiliary force member which is disposed relative to the transmitting component to apply an assist force to the transmitting component, at least when the clutch operator is moved to disengage the clutch element, in such a direction as to assist disengaging the clutch element while the clutch operator is moved from a disengage start position, at which point the clutch operator works against the bias of the clutch spring, to a disengaged position where the clutch element is in the disengaged position,
a rotatable member for transmitting the urging force of the auxiliary force member to the movable member; and
a cam mechanism being interposed between the movable member and the rotatable member, the cam mechanism including a cam surface configured to maintain the urging force applied by the rotatable member to the movable member within a fixed range while the clutch operator is moved from an intermediate position between the disengage start position and the disengaged position to the disengaged position;
wherein the transmitting component has a first clutch wire connected to the clutch operator and a second clutch wire connected to a clutch release mechanism of the clutch, and wherein the first and second clutch wires are connected to the movable member.
5. The clutch assist device of claim 4, wherein the cam mechanism has a cam groove formed through one of the movable member and the rotatable member that defines the cam surface, and a cam follower being in contact with the cam groove and supported by the other of the movable member and the rotatable member.
6. The clutch operation assisting device of claim 5, wherein the auxiliary force member comprises a spring, and the cam groove in conjunction with the cam follower are configured to restrain the spring from expanding or contracting freely while the clutch operator is moved from the intermediate position to the disengaged position.
7. The clutch mechanism of claim 4, wherein the auxiliary force member urges the transmitting component toward a position corresponding to the engaged position of the clutch when the clutch operator is in a return position, and the direction of the assist force applied to the transmitting component is changed from such a direction to a direction assisting disengagement of the clutch when the clutch operator is moved toward the disengaged position from the return position through the disengage start position, additionally comprising a canceling force member, which applies an urging force to cancel the urging force of the auxiliary force member that is applied to the transmitting component when the clutch operator is initially moved from the return position toward the disengage start position.
8. The clutch operation assisting device of claim 7, wherein the urging force of the clutch spring applied to the movable member is zero and the rotatable member receives the urging force of the canceling force member while the clutch operator is moved from the return position to the disengaged start position.
9. The clutch operation assisting device of claim 7, additionally comprising a stopper for receiving the rotatable member when the clutch operator is in the return position, the stopper being urged by the canceling force member.
10. A clutch assist device incorporated in a clutch mechanism having a friction clutch with a clutch spring, a transmitting component connected to the friction clutch, and a clutch operator which is connected to the transmitting component and which changes the engagement state of the friction clutch when operated against the urging force of the clutch spring, the clutch assist device comprising:
a movable member movable in synchronization with the clutch operator;
an auxiliary elastic member for applying an urging force to rotate the rotatable member, the auxiliary elastic member being pivotal through a fixed path with movement of the movable member; and
a cam mechanism interposed between the movable member and the rotatable member for transmitting the urging force applied to the rotatable member to the movable member,
wherein, when the clutch operator is operated in such a direction as to disengage the friction clutch, the auxiliary elastic member applies an urging force to move the movable member in such a direction as to assist disengaging the friction clutch while the clutch operator is moved from a disengage start position, at which point the clutch operator works against the bias of the clutch spring, to a disengaged position where the clutch element is in the disengaged position, and wherein the cam mechanism is configured to change a velocity ratio, which is the ratio of the rotational velocity of the rotatable member to the traveling velocity of the movable member, while the clutch operator is moved from the disengage start position to the disengaged position.
11. The clutch operation assisting device of claim 10, wherein the velocity ratio at the time when the clutch operator is at the disengage start position is greater than that at the time when the operating element is in the disengaged position.
12. The clutch operation assisting device of claim 10, wherein the average of the velocity ratio at the time when the clutch operator is moved from the disengage start position to an intermediate position between the disengage start position and the disengaged position is greater than the average of the velocity ratio at the time when the clutch operator is moved from the intermediate position to the disengaged position.
13. The clutch operation assisting device of claim 10, wherein the cam mechanism is configured to gradually decrease the velocity ratio while the clutch operator is moved from the disengage start position to the disengaged position.
14. The clutch operation assisting device of claim 10, wherein the movable member is a second rotatable member.
15. The clutch operation assisting device of claim 10, wherein the cam mechanism has a cam groove formed through one of the movable member and the rotatable member, and a cam follower being in contact with the cam groove and supported by the other of the movable member and the rotatable member.
16. The clutch operation assisting device of claim 10, wherein the auxiliary force member comprises a spring.
17. A clutch assist device incorporated in a clutch mechanism having a friction clutch with a clutch spring, a transmitting component connected to the friction clutch, and a clutch operator which is connected to the transmitting component and which changes the engagement state of the friction clutch when operated against the urging force of the clutch spring, the clutch assist device comprising:
wherein, when the clutch operator is operated in such a direction as to disengage the friction clutch, the auxiliary elastic member applies an urging force to move the movable member in such a direction as to assist disengaging the friction clutch while the clutch operator is moved from a disengage start position, at which point the clutch operator works against the bias of the clutch spring, to a disengaged position where the clutch element is in the disengaged position, and wherein the cam mechanism is configured to maintain a ratio between the reactive force of the clutch spring and the load applied to the clutch operator within a preset range while the clutch operator is moved from the disengaged start position to an intermediate position between the disengage start position and the disengaged position.
18. A clutch assist device incorporated in a clutch mechanism having a friction clutch with a clutch spring, a transmitting component connected to the friction clutch, and a clutch operator which is connected to the transmitting component and which changes the engagement state of the friction clutch when operated against the urging force of the clutch spring, the clutch assist device comprising:
a force transmitting component interposed between the movable member and the rotatable member for transmitting the urging force caused by the auxiliary elastic member which the rotatable member receives to the movable member,
wherein, when the clutch operator is operated in such a direction as to disengage the friction clutch, the auxiliary elastic member applies an urging force to move the movable member in such a direction as to disengage the friction clutch while the clutch operator is moved from a disengage start position to a disengaged position, and
wherein the urging force transmitting component is configured to change a velocity ratio, which is the ratio of the rotational velocity of the rotatable member to the traveling velocity of the movable member, while the clutch operator is moved from the disengage start position to the disengaged position. Description
This application is based on and claims priority under 35 U.S.C. � 119(a)-(d) to Japanese Patent Application No. 2005-128069, filed Apr. 26, 2005, and to Japanese Patent Application No. 2005-002872, filed Jan. 7, 2005, the entire contents of which are hereby incorporated by reference.
An engine unit of a vehicle, for example a motorcycle, is often equipped with a friction clutch that operates to engage and disengage a transmission. With the clutch engaged, the transmission transfers torque from the engine crankshaft to one or more wheels of the motorcycle and, with the clutch disengaged, the transmission is decoupled from the engine so as not transfer a driving torque to the wheel(s). The friction clutch typically has friction plates and clutch plates laid alternately next to one another. A clutch spring presses the friction plates against the clutch plates and biases the friction plates into this state so as to transmit torque.
A clutch assist mechanism has been previously proposed to reduce the force necessary to actuate the clutch operating lever. See Japanese Patent Publication No. Hei 7-132872. The clutch assist device disclosed in this patent publication is incorporated in a clutch release mechanism to which the clutch wire is connected.
The conventional assist mechanism has an arm rotatable together with a push lever of the clutch release mechanism and a spring unit disposed between an end of the arm and the engine. The spring unit has a spring holder which can expand and contract in its axial direction and a compression coil spring for urging the spring holder in the direction in which the spring holder expands. The spring holder has a first end rotatably connected to the end of the arm and a second end rotatably connected to a bracket extending from the engine.
In the conventional assist mechanism, the center of rotation of the arm and the first and second ends of the spring holder are aligned on one straight line when the clutch operating lever is operated by a distance corresponding to its free play (i.e., movement of the clutch operating lever before disengagement of the clutch start). Therefore, the urging force of the compression coil spring acts in such a direction as to compress the arm and does not act as a force (moment) to rotate the arm.
However, when the clutch lever is rotated beyond the free play range, the joint between the end of the arm and the first end of the spring holder is offset from the straight line connecting the center of rotation of the arm and the second end of the spring holder. Therefore, the urging force of the compression coil spring acts in such a direction as to rotate the arm, and the arm is forcibly rotated in such a direction to disengage the friction clutch. As a result, the urging force of the compression coil spring is added to the force applied to operate the clutch lever and the force necessary to operate the clutch lever to disengage the friction clutch is reduced.
According to the clutch operating device disclosed in the above-noted Japanese patent publication, when the clutch lever is rotated to a disengage start position at the end of the free play range, the urging force of the clutch spring is applied to the clutch lever. The compression coil spring of the assist mechanism expands to cancel the urging force of the clutch spring in synchronization with the operation of the clutch lever in such a direction as to disengage the friction clutch after the clutch lever has passed the disengage start position.
In the clutch operating device, however, the compression coil spring of the assist mechanism can freely expand after the clutch lever has passed the disengage start position. Therefore, the urging force of the compression coil spring applied from the arm to the push lever is not controlled. That is, since an end of the spring holder is directly connected to an end of the arm and the spring unit rotates in the same manner as the arm, the magnitude of the urging force applied to the push lever is left uncontrolled.
Thus, it is not possible to prevent the clutch lever from suddenly becoming light as it gets close to a disengage position where the friction clutch is disengaged while the clutch lever is moved to disengage the friction clutch. Therefore, the operating feel of the clutch lever is unnatural, and there is still room for improvement in terms of the operability of the clutch lever.
When the clutch lever is moved to disengage the friction clutch, the force necessary to operate the clutch lever is preferably small especially in the first half between the disengage start position and the disengage position (the half on the side of the disengage start position). That is, it is preferable to reduce the force necessary to operate the clutch lever in the initial stage of what is called half-clutch operation. However, with the conventional clutch operation device, a large force is necessary in the first stage of the half-clutch operation. Therefore, there is also room for improvement in terms of the operability of the clutch lever in this respect.
A need therefore exists for a clutch operation assisting device with which the operation of the operating element when disengaging the clutch does not feel awkward and which can improve the operability of the assist mechanism.
An aspect of the present invention involves a clutch mechanism for a vehicle comprising a clutch assist device operating between a clutch and a clutch operator. The clutch operator is connected to the clutch by a transmitting component. The clutch includes a clutch element, which is biased toward an engaged position and is movable by the clutch operator and the transmitting component from the engaged position to a disengaged position. A clutch assist device operates between the clutch an the transmitting component. The clutch assist device comprises an auxiliary force member, which is disposed relative to the transmitting component, at least when the clutch operator is moved to disengage the clutch element, to apply an assist force to the transmitting component. The assist force is applied in such a direction as to assist disengaging the clutch element while the clutch operator is moved from a disengage start position, at which point the clutch operator works against the bias of the clutch spring, to a disengaged position where the clutch element is in the disengaged position. The assist force of the auxiliary force member, which is applied to the transmitting component, is maintained within a fixed range while the clutch operator is moved from an intermediate position, lying between the disengage start position and the disengaged position, to the disengage position.
Accordingly, when the clutch operator is operated in such a direction as to disengage the clutch, the urging force of the auxiliary force member is added to the force applied by the clutch operator. Therefore, the clutch lever is more easily operated.
In addition, the urging force of the auxiliary force member applied to the transmitting component does not increase over a fixed range even when the clutch operator gets close to the disengaged position. Consequently, the manual force operating operator lever is prevented from suddenly becoming light as the operator nears the disengaged position. The clutch assist device thus reduces the manual force required to operate the clutch while preserving the operational feel of the clutch operator when moving the operator from a released position to a half clutched position, to a full clutch position.
An additional aspect of the present invention involves a clutch assist device for incorporation into a clutch mechanism. The clutch mechanism includes a friction clutch with a clutch spring, a transmitting component connected to the friction clutch, and a clutch operator which is connected to the transmitting component and which changes the engagement state of the friction clutch when operated against the urging force of the clutch spring. The clutch assist device comprises a movable member that is movable in synchronization with the clutch operator and a rotatable member. An auxiliary elastic member for applying an urging force to rotate the rotatable member, is pivotal through a fixed path with movement of the movable member. A cam mechanism is interposed between the movable member and the rotatable member for transmitting the urging force applied to the rotatable member to the movable member. When the clutch operator is operated in such a direction as to disengage the friction clutch, the auxiliary elastic member applies an urging force to move the movable member in such a direction as to assist disengaging the friction clutch while the clutch operator is moved from a disengage start position, at which point the clutch operator works against the bias of the clutch spring, to a disengaged position where the clutch element is in the disengaged position.
In a preferred mode, the rotatable member and the cam mechanism are interposed between the auxiliary elastic member and the movable member. Since the auxiliary elastic member oscillates through the fixed path, the direction of the urging force can be freely changed. Therefore, the urging force can be always applied in a desired direction, and the loss of the urging force applied to the movable member can be reduced although a cam mechanism is interposed between the auxiliary elastic member and the movable member. In addition, the wear of the components in the clutch assist device can be reduced, and the service life and reliability of the clutch assist device can be improved.
Also, since the cam mechanism is interposed between the auxiliary elastic member and the movable member, the relation between the auxiliary elastic member and the movement of the movable member can be freely set. Therefore, the variation characteristics of the urging force applied to the movable member (in other words, the variation characteristics of the urging force at the time when the clutch operator is operated) can be easily set according to the application and performance criteria. Therefore, the operability of the clutch lever can be further improved by, for example, reducing the force necessary to operate the clutch lever immediately after the disengagement of the friction clutch has started.
These and other features, aspects, and advantages of the present invention will now be described in connection with preferred embodiments of the invention, in reference to the accompanying drawings. The illustrated embodiments, however, are merely examples and are not intended to limit the invention. The drawings include the following thirty-five figures.
FIG. 36 is a cross-sectional view illustrating the connection structure between the operation assisting device and the friction clutch in another modification.
FIG. 37 is a view of the connection illustrated in FIG. 36 as seen in the direction of the arrow A of FIG. 36.
For the purpose of describing the embodiments below, several terms of orientations are used to describe the motorcycle, the clutch assist device, and the components of the motorcycle with which the clutch assist device operates. Terms such as, for example, “up,” “down,” “left,” “right,” “vertical,” “horizontal,” “higher,” “upper,” “lower,” “front,” and “back” are used from the perspective of the motorcycle orientation shown in FIG. 1 and in manner consistent with the ordinary meaning of these terms; however, the clutch assist device and the associated components of the motorcycle can assume different orientations than those illustrated in the embodiments. Hence, it is not intended that such terms of orientation limit the invention.
In this embodiment, a clutch assist device 50 is installed at an intermediate point of the clutch wire 43 to reduce the manual load required to operate the clutch lever 9. In other words, the clutch wire 43 has a first clutch wire 43 a connected to the clutch lever 9 and a second clutch wire 43 b connected to the push lever 40, and the first clutch wire 43 a and the second clutch wire 43 b are connected to each other via the clutch assist device 50.
As shown in FIG. 4, the wire connecting part 61 of the first rotatable member 57 is located in the front half space (in the left half in FIG. 4) in the case body 53. The wire connecting part 61 has a lower edge 67. The lower edge 67 is curved in an arc around the first pivot shaft 63. The lower edge 67 of the wire connecting part 61 has an engaging groove 68 (see FIG. 8) and an engaging hole 69. The engaging groove 68 receives the inner wire 44 of the first clutch wire 43 a and the inner wire 44 of the second clutch wire 43 b and opens at the outer peripheral surface of the edge 67. The engaging hole 69 is a slot elongated along the circumferential direction of the lower edge 67. The engaging hole 69 opens at the outer peripheral surface of the lower edge 67 and at the engaging groove 68. Engaging elements 70, which have cylindrical shapes and are secured to the respective ends of the inner wires 44, are engaged with the opening edge of the engaging hole 69.
Therefore, the inner wire 44 of the first clutch wire 43 a and the inner wire 44 of the second clutch wire 43 b are integrally connected to each other via the first rotatable member 57. This connection allows the inner wire 44 of the first clutch wire 43 a and the inner wire 44 of the second clutch wire 43 b to move together through the same distance.
As shown in FIG. 3 and FIG. 7, the case cover 54 preferably has a pair of first wire introduction port 95 a and 95 b and a second wire introduction port 96. The first and second introduction ports 95 a, 95 b and 96 open into the exterior case 51. The first wire introduction port 95 a protrudes upward from an upper part of the front end the case cover 54. The other first wire introduction port 95 b protrudes obliquely upward from an intermediate part of the front end of the case cover 54. The second wire introduction port 96 protrudes backward from a lower part of the rear end of the case cover 54.
In this embodiment, the first clutch wire 43 a is inserted into the first wire introduction port 95 a. The inner wire 44 of the first clutch wire 43 a extends into the exterior case 51 and is connected to the first rotatable member 57. The first clutch wire 43 a extends upward along the first portion 5 a of the down tube 5 from a front end of the exterior case 51 (see FIG. 1).
The second clutch wire 43 b is inserted into the second wire introduction port 96. The inner wire 44 of the second clutch wire 43 b extends into the exterior case 51 and is connected to the first rotatable member 57. The second clutch wire 43 b extends backward from a rear end of the exterior case 51 along the left side of the engine 13 and linearly connects the first rotatable member 57 of the assist mechanism 52 and the push lever 40 (see FIG. 1).
FIG. 4 and FIG. 5 show the state of the assist mechanism 52 at the time when the clutch lever 9 is in the fully released position. When the clutch operating lever 9 is in the fully released position, the second pivot shaft 74 of the link plate 72 and the third pivot shaft 76 of the link lever 73 are positioned below the straight line S1 connecting the pivot end 86 and the connecting end 89 of the spring holder 81. Also, the spring unit 59 is inclined such that the connecting end 89 of the spring holder 81 is positioned higher than the pivot end 86. In addition, the cam groove 71 of the link plate 72 extends in the longitudinal direction of the case body 53 and is maintained in a convex upward position.
When the rider moves the clutch operating lever 9 from the fully released position toward the disengage start position, the first rotatable member 57 is pulled upward via the first clutch wire 43 a and is rotated in the clockwise direction as indicated by the arrows in FIG. 10 and FIG. 11. The rotation of the rotatable member 57 causes the lever part 62 having the cam groove 71 to move downward. Therefore, the cam follower 79, which is in contact with the cam groove 71, receives a force; this force urges the cam follower 79 toward the front of the case body 53, and the link plate 72 and the link lever 73 are rotated in the counterclockwise direction. As a result, the spring unit 59 is rotated downward about the pivot end 86.
When the clutch operating lever 9 reaches the disengage start position, the second and third pivot shafts 74, 76 are positioned on the straight line S1 as shown in FIG. 11. Therefore, although the urging force of the auxiliary spring 82 is being applied to the link plate 72 and the link lever 73, the link plate 72 and the link lever 73 are not rotated by the urging force.
When the clutch operating lever 9 is moved from the disengage start position toward the disengage position, the first rotatable member 57 is further rotated in the clockwise direction. The rotation of the first rotatable member 57 causes the lever part 62 having the cam groove 71 to move downward, and the cam groove 71 is brought to an upright position. Therefore, the cam follower 79 in contact with the cam groove 71 receives a force which urges it obliquely downward toward the front of the case body 53, and the link plate 72 and the link lever 73 are rotated in the counterclockwise direction.
In this embodiment, when the clutch operating lever 9 is shifted from the disengage start position to the disengaged position, the spring unit 59 is rotated downward about the pivot end 86 and the straight line SI is offset to a position below the center of rotation of the link plate 72 and the link lever 73.
Therefore, the spring holder 81, which receives the urging force of the auxiliary spring 82, expands and the urging force of the auxiliary spring 82 acts to rotate the link plate 72 and the link lever 73. Thus, when the clutch operating lever 9 is moved toward the disengaged position from the disengage start position, the link plate 72 and the link lever 73 are forcibly rotated in the counterclockwise direction by the auxiliary spring 82. Therefore, the urging force of the auxiliary spring 82 is added to the operating force the rider applies to squeeze the clutch operating lever 9. Thus, less force is required by the rider to operate the clutch operating lever 9.
According to this embodiment, the cam groove 71 determines the timing at which the link plate 72 and the link lever 73 receive an urging force from the spring unit 59 and starts moving in the counterclockwise direction. More specifically, the cam groove 71 is of such a shape as to maintain the urging force of the auxiliary spring 82 applied from the link plate 72 and the link lever 73 to the first rotatable member 57 within a fixed range when the clutch lever 9 is moved from the midpoint between the disengage start position and the disengaged position toward the disengaged position. In other words, the cam groove 71 is of such a shape as to permit the movement of the link plate 72 and the link lever 73 while the clutch operating lever 9 is moved from the disengage start position to the midpoint and as to restrict the movement of the link plate 72 and the link lever 73 to prevent the auxiliary spring 82 from expanding freely while the clutch lever 9 is moved from the midpoint to the disengaged position. Therefore, in this embodiment, the cam mechanism, which is comprised of the cam groove 71 and the cam follower 79, controls the urging force of the auxiliary spring 82 applied to the first rotatable member 57.
In FIG. 15, curve designated as Y shows the change of the load applied to the clutch operating lever 9 when the clutch operating lever 9 is moved in such a direction as to disengage the friction clutch 18. As can be understood from curve Y, the load applied to the clutch lever 9 is always smaller than the load of the clutch spring 27 applied to the push lever 40 while the clutch lever 9 is shifted to the disengaged position from the disengage start position. This is because, when the link plate 72 is rotated in the counterclockwise direction by the force transmitted through the first clutch wire 43 a, the urging force of the auxiliary spring 82, which forcibly urges the link plate 72 to rotate in the counterclockwise direction, is added.
In addition, in this embodiment, since the shape of the cam groove 71 is determined as described before, the load applied to the clutch operating lever 9 can be maintained generally constant while the clutch operating lever 9 is moved from the midpoint to the disengaged position. As a result, the load applied to the push lever 40 and the load applied to the clutch lever 9 change with similar characteristics with respect to the wire stroke amount as shown in FIG. 15.
As described before, when the clutch operating lever 9 is in the fully released position (i.e., the return position), the second pivot shaft 74 of the link plate 72 and the third pivot shaft 76 of the link lever 73 are positioned below the straight line S1, as shown in FIG. 4 and FIG. 5. Therefore, the link plate 72 and the link lever 73 are urged in the clockwise direction; that is, in a direction opposite the direction to disconnect the friction clutch 18, by the urging force of the auxiliary spring 82.
The case cover 54 has a support wall 111 extending from the opening edge of the opening 10 to the center of the opening 110. The support wall 111 is located at a position which does not interfere with the wire connecting part 61 of the first rotatable member 57 and has a boss part 113 with a screw hole 112 at its end. The position of the screw hole 112 preferably coincides with the center of the opening 110.
Furthermore, the assist mechanism 52 of this embodiment has the canceling spring unit 100, which abuts against the lock pin 103 of the link plate 72 from below when the clutch operating lever 9 is in the fuilly released position. The canceling spring 105 of the canceling spring unit 100 acts to cancel the counter assist force caused by the auxiliary spring 82 and prevents the rotation of the link plate 72 in such a direction as to engage the friction clutch 18 based on the counter assist force. Therefore, the initial input load necessary to squeeze the clutch lever 9 first is not increased to ease the operation and feel of the clutch lever 9.
The first rotatable member 57 has a pivot part 60 and a wire connecting part 61. As shown in FIG. 4, the first rotatable member 57 of the first embodiment has a lever part 62 having the cam groove 71 in addition to the wire connecting part 61. The rotatable member 57 of the second embodiment, however, does not have the lever part 62 and the wire connecting part 61 has a cam groove 71, as shown in FIG. 18. In this embodiment, since the lever part 62 is omitted, the area of the first rotatable member 57 is smaller. The first rotatable member 57 is generally in the form of a sector with a central angle of smaller than 120� as viewed along the axial direction of the first pivot shaft 63. The shape of the first rotatable member 57 is not specifically limited, though. The first rotatable member 57 may have other shape as well, such as, for example, be triangular. The first rotatable member 57 may be made even smaller in size in some applications. For example, the first rotatable member 57, in the illustrated embodiment, is generally in the form of a sector with a central angle of less than 90�.
When the clutch lever 9 is moved from the disengage start position to the disengaged position, the spring unit 59 is further rotated in the clockwise direction about the pivot end 86. Then, the straight line SI (connecting the pivot end 86 and the connecting end 89 of the spring unit 59) is offset upward from the center of rotation of the link plate 72 (pivot shaft 74).
In the embodiments described above, the first and second clutch wires 43 a, 43 b (more specifically, the inner wires 44 thereof) as first and second linear members are physically separated from each other. However, the first linear member and the second linear member are not necessarily separated from each other as long as they can be connected to the rotatable member 57. The first linear member and the second linear member may be joined together. That is, one side portion and other side portion of one linear member connected to the first rotatable member 57 may be regarded as the first linear member and the second linear member, respectively. In this case, although the first joint and the second joint may be located in different locations, the linear member may be connected to the first rotatable member 57 at one point so that the first and second joints can be located at the same position.
As shown in FIG. 36 and FIG. 37, the second clutch wire 43 b may be omitted and a shaft coaxially extending from the push lever shaft 39 may be used as a pivot shaft 63 as the rotatable shaft for the first rotatable member 57. This configuration can create an effect almost the same as those of the embodiments described above.
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