Rotary shafts – gudgeons – housings – and flexible couplings for ro – Torque transmitted via flexible element – Coil spring
Reexamination Certificate
1999-03-26
2001-06-05
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Torque transmitted via flexible element
Coil spring
C464S064100, C464S066100, C192S213210
Reexamination Certificate
active
06241614
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
The invention relates to a damper mechanism and particularly to a damper mechanism for damping torsional vibrations in a power transmission system.
B. Description of the Background Art
A clutch disk assembly used in, for instance an automotive vehicle, is typically installed in a clutch mechanism such that the clutch disk assembly can be used in clutch engagement and clutch dis-engagement operations for transmitting torque from a flywheel to a transmission input shaft. The clutch disk assembly preferably also includes a vibration dampening function for absorbing and damping vibration transmitted from the flywheel. Generally, vibrations of a vehicle include idling noises (rattle), driving noises (acceleration/deceleration rattle and muffled noises) and tip-in/tip-out (low frequency vibrations). The clutch disk assembly has the above damper function for removing these noises and vibrations.
The idling noises are rattling noises which occur from a transmission when the transmission is in a neutral position, e.g., during waiting at traffic signals with clutch pedal off. This rattling occurs due to the fact that engine torque is low in an engine idling range and engine combustion causes large torque variations in the idling range. In this state, gear contact occurs between an input gear and a counter gear of a transmission, and thereby noises are produced.
The tip-in/tip-out low frequency vibrations are large longitudinal vibrations of a vehicle which occur when a driver rapidly depresses or releases an accelerator with the clutch in an engaged, torque transmitting condition. If rigidity of a drive transmission system is low, torque transmitted to wheels is transmitted or reflected from the wheels back through the drive train creating large oscillations of torque.
In a state where no torque is transmitted (zero torque transmission), for instance during idling, the dampening characteristics of most clutch disk assemblies are such that idling vibrations cannot be adequately dampened creating corresponding noises. Therefore, a low torsional rigidity is preferable in this region of zero torque transmission. Contrarily, it is necessary to maximize the rigidity of the torsion characteristics of the clutch disk assembly for suppressing the longitudinal vibrations of the tip-in/tip-out.
For overcoming the above problems, a clutch disk assembly which uses two kinds of springs for achieving vibration dampening characteristics in two separate stages has been provided. This structure has a low torsional rigidity and a low hysteresis torque in the first stage of a low torsion angle, and therefore can achieve an effect of preventing noises during idling. Since the torsional rigidity and the hysteresis torque are high in the second stage of a high torsion angle, the longitudinal vibrations at the time of tip-in/tip-out can be effectively damped.
A damper mechanism is already known where operation of a high hysteresis torque generating mechanism in a second stage with a high torsion angle is prevented when minute vibrations caused, e.g., by combustion variations of an engine are supplied in the second stage region. Thereby the minute vibrations are effectively absorbed by a low hysteresis torque.
In a damper mechanism of the conventional clutch disk assembly described above, torsional operation is repeated through a wide angular range in and between the positive second stage and the negative second stage in the torsion characteristic when low frequency vibrations are supplied thereto. Therefore, only a low hysteresis torque is generated in the region of the positive and negative first stages between the positive and negative second stages. Accordingly, all of the vibrations can be damped only to a small extent, and low frequency vibrations cannot be damped sufficiently. Further, the regions of the positive and negative first stages may form a gap or space in the torsion characteristics, resulting in an undesirable increase in longitudinal vibrations.
SUMMARY OF THE INVENTION
One object of the invention is to allow effective damping of torsional vibrations caused by torsion in and between positive and negative second stages in a damper mechanism having torsion characteristics in two stages.
In accordance with one aspect of the present invention, a damper mechanism includes a first rotary member and a second rotary member. The secondary rotary member is coupled to the first rotary member for relative rotary displacement with respect to the first rotary member about a central rotary axis. The relative rotary displacement occurs in a rotating direction defined about the central rotary axis. A first elastic member elastically couples the first and second rotary members together in the rotating direction. The first elastic member is compressible in a first stage of the relative rotary displacement between the first and second rotary members, the first stage being confined within a first torsion angle. A second elastic member elastically couples the first and second rotary members together in the rotating direction, and is compressible in a second stage of the relative rotary displacement between the first and second rotary members. The second stage is defined by an second torsion angle that exceeds the first torsion angle in circumferential size. The second elastic member provides rigidity in the second stage. The rigidity of the second elastic member is greater than the rigidity of the first elastic member in the first stage. A friction generating mechanism frictionally couples the first and second rotary members to each other in the rotating direction. The friction generating mechanism is configured to allow sliding between the first and second rotary members within both of the first and second stages. A friction suppressing means prevents sliding of the friction generating mechanism in response to torsional vibrations having a magnitude less than a predetermined torque in the first and second stages.
Preferably, a separate plate is operably disposed between the first and second rotary members. The first elastic member is disposed between the first rotary member and the separated plate. The second elastic member is disposed between the separate plate and the second rotary member.
Preferably, a second friction suppressing mechanism suppresses sliding in the friction generating mechanism in response to torsional vibrations having a magnitude less than a predetermined torque in the first stage.
In accordance with another aspect of the present invention, a damper mechanism includes a first rotary member and a second rotary member coupled to the first rotary member for relative rotary displacement with respect to the first rotary member about a central rotary axis. The relative rotary displacement occurs in a rotating direction defined about the central rotary axis. A first elastic member elastically couples the first and second rotary members together in the rotating direction. The first elastic member is compressible in a first stage of the relative rotary displacement between the first and second rotary members. The first stage is confined within a first torsion angle. A second elastic member elastically couples the first and second rotary members together in the rotating direction, and is compressible in a second stage of the relative rotary displacement between the first and second rotary members. The second stage is defined by an second torsion angle that exceeds the first torsion angle in circumferential size. The second elastic member provides rigidity in the second stage that is greater than rigidity of the first elastic member in the first stage. A friction generating mechanism frictionally couples the first and second rotary members to each other in the rotating direction. The friction generating mechanism is configured to refrain from sliding in response to torsional vibrations of less than a predetermined torque in the first and second stages, and the friction generating mechanism is configured to slide in response to torsional vibrations
Mizukami Hiroshi
Ohkubo Mamoru
Browne Lynne H.
Dunwoody Aaron
Exedy Corporation
Shinjyu Global IP Counselors, LLP
LandOfFree
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