Rotary shafts – gudgeons – housings – and flexible couplings for ro – Torque transmitted via flexible element – Coil spring
Reexamination Certificate
1999-07-07
2001-07-24
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Torque transmitted via flexible element
Coil spring
C192S213220
Reexamination Certificate
active
06264563
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
The invention relates to a damper mechanism, and particularly a damper mechanism for transmitting torque and damping torsional vibration.
B. Description of the Background Art
A clutch disk assembly used in a clutch of an automotive vehicle generally has clutch engagement and dis-engagement functions and a vibration dampening features. The dampening features typically include absorbing and damping vibrations transmitted from the flywheel.
The clutch disk assembly includes a pair of input plates opposed to each other, an output hub integrally provided with a radially outwardly extending flange, and coil springs elastically coupling the input plates to the output hub in the circumferential direction. The coil springs provide some of the vibration dampening features. The paired input plates are fixed to one another by stop pins at their outer peripheral portions, and therefore can rotate together as a single structure. The stop pins extend through recesses formed at the outer periphery of the flange, respectively. The input plate pair can rotate relative to the flange through a predetermined angle range, and the relative rotation between therebetween is limited by contact between the stop pins and circumferential ends of the recesses. As described above, the stop pins couple the paired input plates together, and also serve to limit relative rotation between the input plates and the flange of the hub.
The stop pin must have a predetermined diameter, and must be arranged radially inside the outer peripheries of the paired input plates. Due to the above requirements, the relative torsion angle between the pair of input plates and the flange cannot be increased beyond a certain angular range in the structure employing the stop pins. This means that the performance of coil springs cannot be fully utilized even if the coil springs have a high strength, because the relative torsion angle cannot be increased sufficiently. For reducing gear noises and muffled noises in a drive system during driving, it is necessary to minimize the torsional rigidity during acceleration and deceleration, and thereby set a torsional resonance frequency of the drive system to a value lower than a service speed range of an engine. For achieving a low torsional rigidity and a high stop torque, it is necessary to ensure a wide range for a low torsion angle.
An object of the invention is to provide a damper mechanism, which allows a sufficiently large torsion angle between an input rotary member and an output rotary member, and thereby can suppress vibrations during driving.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a torque transmission mechanism includes a first rotary member and a second rotary member adapted for limited relative rotation with respect to the first rotary member. A damper mechanism is disposed between the first and second rotary members, the damper mechanism having a plurality of elastic members operably disposed between the first and second rotary members. The elastic members are circumferentially compressed in response to relative rotary displacement between the first and second rotary members. The damper mechanism is adapted to exhibit torsion dampening characteristics within a first region and a second region of angular displacement between the first and second rotary members, the damper mechanism exhibiting a greater degree of rigidity in the second region than in the first region. A friction mechanism within the damper mechanism is adapted to generate frictional resistance in response to relative rotary displacement within at least a portion of the second region. A friction suppression mechanism disposed between the first and second rotary members is adapted to limit operation of the friction mechanism within a predetermined angular displacement range within the second region such that generated friction is reduced within the predetermined angular displacement range. The damper mechanism exhibits a torsional rigidity in the second region of no more than 1.5 kgfm/deg (1.5 kilograms of force•meter per degree).
Preferably, the torsional rigidity in the second region of the torsion characteristics is less than 1.0 kgfm/deg. However, the torsional rigidity in the second region is preferably in a range from 0.6 kgfm/deg to 0.8 kgfm/deg.
Preferably, the friction mechanism and the friction suppression mechanism are adapted such that a first level of hysteresis torque is generated in response to small vibrations that cause relative rotary displacement within the predetermined angular displacement range within in the second region. A second level of hysteresis torque is generated in response to vibrations that cause relative rotary displacement greater than the predetermined angular displacement range within the second range. The first level of hysteresis torque is smaller than the second level of hysteresis torque, such that ratio of the first level to second level is no more than 0.15.
Preferably, the ratio of (first level)/(second level) is no more than 0.10.
Preferably, the ratio of (first level)/(second level) is in a range from 0.03 to 0.05.
Preferably, the first level of hysteresis torque has a magnitude of no more than 0.20 kgfm.
Preferably, the first level of hysteresis torque is no more than 0.10 kgfm.
Preferably, the first level of hysteresis torque is in a range of from about 0.04 kgfm to about 0.08 kgfm.
According to the damper mechanism of the above aspect, a conventional stop pin is not employed, and a plate-like coupling portion is employed for coupling the second and third rotary plates together and restricting the relative torsion angle of the first rotary plate to the second and third rotary plates. Since the plate-like coupling portion is radially shorter than the conventional stop pin, it can be arranged in the radially outermost position of each rotary plate. As a result, the allowed torsion angle of a stop mechanism is not reduced by the window or the like, and can be sufficiently large. Since the allowed maximum torsion angle can be large, the torsional rigidity in the second region of the torsion characteristics can be significantly reduced. As a result, a torsional resonance frequency of a drive system can be reduced below a service speed range of an engine. When a torsional vibration not exceeding the predetermined angle is supplied to the damper mechanism in the second region of the torsion response, the friction suppressing mechanism stops the operation of the friction mechanism so that a large friction resistance does not occur. As a result, gear noises and muffled noises of the drive system during driving are significantly reduced.
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Browne Lynne H.
Exedy Corporation
Shinjyu Global IP Counselors, LLP
Thompson Kenneth
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