1. Field of the Invention
This invention generally relates to a damper mechanism. More specifically, the present invention relates to a damper mechanism and a damper disk assembly for absorbing or damping torsional vibrations in a power transmission system.
2. Background Information
Clutch disk assemblies used in vehicles have a clutch function for engaging and disengaging the assembly with a flywheel and to receive rotation from the flywheel. Clutch disk assemblies also have a damper function for absorbing and damping torque variations transmitted from the flywheel. These torque variations can also create vibrations.
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 that emanate from a transmission when the transmission is in a neutral position, e.g., while waiting at traffic signals with a disengaged clutch pedal. These noises occur because engine torque is low in an engine idling range and engine combustion causes large torque variations.
The tip-in/tip-outs (low frequency vibrations) are large longitudinal vibrations of a vehicle which occur when a driver rapidly depresses or releases an accelerator. More specifically, excessive vibrations occur when a torque is supplied stepwise to the drive and transmission system. As a result, a torque transmitted to wheels is reversely transmitted from the wheels to the drive system so that an excessive return torque occurs in the wheels. Thereby, the vehicle body transitionally vibrates back-and-forth to a large extent.
Noises during idling are related to a torque region around zero in torsion characteristics of the clutch disk assembly. A lower torsional rigidity can effectively dampen the vibrations. Accordingly, a clutch disk assembly has been provided in which a low rigidity spring is used for achieving nonlinear torsion characteristics having two stages exhibiting low and high rigidities. This clutch disk assembly is configured to exhibit a low torsional rigidity and a low hysteresis torque in the first stages. Therefore, this clutch disk assembly can effectively prevent noises during idling.
As described above, it is necessary to maintain a low rigidity in the first stage and to maintain relatively high rigidities in the second and third stages. For achieving sufficient stop torque, a region of the largest rigidity is required in a region of the largest torsion angle.
A damper mechanism that achieves the aforementioned characteristics is already known. Such a damper mechanism has two kinds of springs that operate in series in the first stage, and two kinds of springs that operate in parallel to provide high rigidity when the torsion angle is large. For example, in a structure disclosed in Japanese Laid-Open Patent Publication No. 5-240302, two kinds of springs operate in series when the torsion angle is small. Further, the two kinds of springs operate in parallel when the torsion angle exceeds a predetermined value.
This damper mechanism includes clutch and retaining plates, a hub, a rotary member, a first elastic member, an intermediate member, and a second elastic member. The clutch and retaining plates are on an input side. The hub is on an output side. The rotary member is arranged between the clutch and retaining plates and the hub. The first elastic member elastically couples the hub and an intermediate member in the rotating direction. The second elastic member elastically couples the intermediate member to the clutch and retaining plates in the rotating direction.
The clutch and retaining plates are provided with compressing portions which are spaced predetermined distances from the circumferentially opposite ends of the first elastic member. Each of stop pins coupling the clutch and retaining plates together is spaced a predetermined distance from an edge of a recess formed in a flange of the hub. Owing to the above structure, when the hub is twisted in one direction with respect to the clutch and retaining plates, the first and second elastic members initially operate in series so that a characteristically low rigidity is achieved. When the torsion angle increases to a predetermined value, the intermediate member engages with the hub, and the compressing portions of the clutch and retaining plates come into contact with the first elastic member. Thereafter, the first elastic member is compressed between the hub and the input plate, and the second elastic member is compressed between the hub and the input plate. Thus, the first and second elastic members operate in parallel between the hub and the input plate. When the torsion angle further increases, the stop pin comes into contact with the edge of the recess in the flange of the hub so that the relative rotation stops.
In the structure described above, the first and second elastic members start to be compressed at the torsion angle of 0 degrees. Therefore, the circumferential space between the stop pin and the edge of the recess in the flange of the hub can excessively increase. More specifically, the recess in the flange must be circumferentially large. In this case, windows that are formed in the flange of the hub for accommodating the elastic members must be small with regards to their circumferential angle or number.
In the structure described above, all the loads of the first and second elastic members act on the hub and the input plate when the first and second elastic members are compressed in parallel. Therefore, the flange of the hub must have an increased strength.
In view of the above, there exists a need for damper mechanism and damper disk assembly which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
An object of the present invention is to provide a damper mechanism, which can achieve characteristics of a low rigidity in a region of small torsional vibrations as well as characteristics of a high rigidity in a region of a large torsion angle, and which reduces a circumferential space in a relative rotation stop portion.
Another object of the present invention is to provide a damper mechanism, which can achieve a low rigidity in a region of small torsional vibrations as well as a high rigidity in a region of a large torsion angle, and which reduces a necessity for increasing a strength of the flange of the hub.
According to a first aspect of the present invention, a damper mechanism for absorbing and damping torsional vibrations in a rotating direction is provided. The damper mechanism includes a first rotary member, a second rotary member, an intermediate rotary member, a first elastic member, a second elastic member, a first relative rotation stop portion and a compressing portion. The second rotary member is rotatable with respect to the first rotary member. The intermediate rotary member is disposed between the first and second rotary members. The first elastic member is disposed between the first rotary member and the intermediate rotary member. The first elastic member is compressed when relative rotation occurs between the first rotary member and the intermediate rotary member. The second elastic member is disposed between the intermediate rotary member and the second rotary member. The second elastic member is compressed when relative rotation occurs between the intermediate rotary member and the second rotary member. The second elastic member is initially compressed in the rotating direction between the intermediate rotary member and the second rotary member to bear an initial load. The first relative rotation stop portion stops the relative rotation between the first rotary member and the intermediate rotary member when the torsion angle of the first rotary member with respect to the second rotary member reaches a first torsion angle. The compressing portion starts the compression of the first elastic member between the first and second rotary members when the torsion angle of the first rotary member with respect to the second rotary member reaches a second torsion angle larger than the first torsion angle. The second elastic member is configured to bear an initial load such that the compression does not occur between the intermediate rotary member and the second rotary member until the torsion angle exceeds the first torsion angle.
In the damper mechanism according to the first aspect of the present invention, only the first elastic member is compressed and the second elastic member is not compressed when the first rotary member is twisted relatively to the second rotary member in a small torsion angle region. Therefore, torsion characteristics are determined only by the first elastic member. When the torsion angle reaches the first torsion angle, the first relative rotation stop portion stops the relative rotation between the first rotary member and the intermediate rotary member. Therefore, the first elastic member compressed between the first and intermediate rotary members is kept in the compressed state. The second elastic member is compressed between the intermediate and second rotary members. Thereby, the torsion characteristics are determined only by the second elastic member. After the torsion angle reaches the second torsion angle, the compressing portion operates to compress the first elastic member between the first and second rotary members. Thus, the first elastic member is compressed between the first and second rotary members. Further, the second elastic member is compressed between the intermediate and second rotary members. In this manner, the first and second elastic members are compressed in parallel.
According to the characteristics described above, the first elastic member provides the first stage of the characteristics. The second elastic member provides the second stage of the characteristics. The first and second elastic members together provide the third stage of the characteristics by the parallel operation.
According to the damper mechanism of the first aspect of the present invention, the parallel compression and therefore the parallel operation of the first and second elastic members are performed in such a manner that the first elastic member is operated by the first rotary member. The second rotary member is operated by the intermediate rotary member engaged with the first rotary member so that a load torque acting on the intermediate rotary member is small. Consequently, the strength of the intermediate rotary member can be lower than that in the prior art.
According to another aspect of the present invention, the damper mechanism further includes a second relative rotation stop portion for stopping the relative rotation between the first and second rotary members when the torsion angle of the first rotary member with respect to the second rotary member reaches a third torsion angle larger than the second torsion angle. In this structure, the first and second elastic members do not act in series so that the circumferential size of the second relative rotation stop portion can be small.
According to yet another aspect of the present invention, the damper mechanism further has such a feature that the first relative rotation stop portion is formed by and between the first rotary member and the intermediate rotary member. The second relative rotation stop portion is formed by and between the intermediate rotary member and the second rotary member. In this structure, the second relative rotation stop portion formed by the intermediate rotary member and the second rotary member can be reduced in circumferential angular size.
According to yet another aspect of the present invention, the damper mechanism further has such a feature that the compressing portion is formed of a portion of the second rotary member. The compressing portion is disposed in a position spaced by a first space in the rotating direction from the first elastic member. A second space formed in the rotating direction between the intermediate rotary member and the second rotary member in the second relative rotation stop portion is angularly larger than the first space. When the torsion angle exceeds the second torsion angle by an extent corresponding to the first space, the compressing portion which is a portion of the second rotary member comes into contact with the second elastic member.
In accordance with still another aspect of the present invention, a damper disk assembly is provided for absorbing and damping torsional vibrations in a rotating direction. The damper disk assembly includes an output rotary hub, a pair of disk-like input members, an intermediate disk-like member, a first elastic member, a second elastic member, a first relative rotation stop portion and a compressing portion. The paired disk-like input members are disposed relatively rotatably around the output rotary hub, and are fixed together with an axial space therebetween. The intermediate disk-like member is disposed rotatably around the output rotary hub and axially between the paired disk-like input members, and is provided with first and second windows. The first elastic member is disposed within the first window. The first elastic member is arranged between the output rotary hub and the intermediate disk-like member for compression in accordance with the relative rotation between the output rotary hub and the intermediate disk-like member. The second elastic member is accommodated in the second window. The second elastic member is arranged between the intermediate disk-like member and the pair of disk-like input members for compression in accordance with the relative rotation between the intermediate rotary member and the pair of disk-like input members. The second elastic member is initially compressed in the rotating direction between the intermediate rotary member and the pair of disk-like input members to bear an initial load. The first relative rotation stop portion stops the relative rotation between the output rotary hub and the intermediate disk-like member when the torsion angle of the output rotary hub with respect to the input disk-like member pair reaches a first torsion angle. The compressing portion starts the compression of the first elastic member between the output rotary hub and the input disk-like member pair when the torsion angle of the output rotary hub with respect to the input disk-like member pair reaches a second torsion angle larger than the first torsion angle. The second elastic member bears an initial load for preventing further compression between the intermediate disk-like member and the input disk-like member pair in a range smaller than the first torsion angle.
According to this damper disk of the present invention, the first elastic member is compressed between the output rotary hub and the intermediate disk-like member in a range of a small torsion angles for which the output rotary hub is twisted in the rotating direction. The output rotary hub is twisted with respect to the pair of disk-like input members. Thereby, the torsion characteristics are provided only by the first elastic member. When the torsion angle increases to the first torsion angle, the first relative rotation stop portion stops the relative rotation between the output rotary hub and the intermediate disk-like member. Thereby, the first elastic member maintains a state in which it is compressed in the rotating direction between the output rotary hub and the intermediate disk-like member. Further, the second elastic member is compressed in the rotating direction between the intermediate disk-like member and the pair of disk-like input members. Thereby, the second elastic member provides the torsion characteristics. When the torsion angle reaches the second torsion angle, the compressing portion starts the compression of the first elastic member. Thereby, the first elastic member is compressed between the output rotary hub and the pair of disk-like input members. Further, the second elastic member is compressed in the rotating direction between the intermediate disk-like member and the input disk-like member pair. Thus, the first and second elastic members operate in parallel between the output rotary hub and the pair of disk-like input members.
As a result, the torsion characteristics of this damper mechanism include the first stage, the second stage, and the third stage. In the first stage only the first elastic member operates. In the second stage only the second elastic member operates. In the third stage only the first and second elastic members operate in parallel.
In this damper disk assembly of the present invention, the first and second elastic members are compressed in parallel, and thereby the parallel operation is performed. During this parallel operation, the first elastic member is compressed between the output rotary hub and the pair of disk-like input members. Further, the second elastic member is compressed in the rotating direction between the intermediate disk-like member and the pair of disk-like input members. Therefore, the load torque exerted on the intermediate disk-like member can be small. Moreover, the strength of the intermediate disk-like member can be smaller than that in the prior art.
According to yet another aspect of the present invention, the damper disk assembly further includes a second relative rotation stop portion. The second relative rotation stop portion stops the relative rotation between the output rotary hub and the pair of disk-like input members when the torsion angle of the output rotary hub with respect to the input disk-like member pair reaches a third torsion angle larger than the second torsion angle.
In this damper disk assembly of the present invention, the first and second elastic members do not operate in series during the operations in the first and second stages. Therefore, the circumferential angular size of the second relative rotation stop portion can be sufficiently small.
According to yet another aspect of the present invention, the damper disk assembly further has such a feature that the first relative rotation stop portion is formed by and between the output rotary hub and the intermediate disk-like member. Further, the second relative rotation stop portion is formed by and between the intermediate disk-like member and the input disk-like member pair.
In this damper disk assembly of the present invention, the angular size of the second relative rotation stop portion formed by the intermediate disk-like member and the pair of disk-like input members can be sufficiently small.
According to yet another aspect of the present invention, the damper disk assembly further has such a feature that the second relative rotation stop portion is formed of an axial portion and a recess in the intermediate disk-like member. The axial portion extends axially for fixing the paired input disk-like members together. The recess in the intermediate disk-like member engages with the axial portion.
Since the second relative rotation stop portion can have a sufficiently small annular size, the recess in the intermediate disk-like member or the like can be small in circumferential size. Thereby, the first and second windows formed in the intermediate disk-like member can be increased in circumferential size and/or number.
According to yet another aspect of the present invention, the damper disk assembly further has such a feature that the output rotary hub has a hub and a sub-plate. The sub-plate extends radially outward from the hub and has a window engaged with the circumferentially opposite ends of the first elastic member.
According to yet another aspect of the present invention, the damper disk assembly further has such a feature that the output rotary hub further includes a damper for elastically coupling the hub and the sub-plate in the rotating direction. The damper has a lower rigidity than the rigidity of the first elastic member. In this damper disk assembly, the damper operates prior to operation of the first elastic member, and thereby achieves a low rigidity in the initial torsion characteristics.
According to yet another aspect of the present invention, the damper disk assembly further includes a pair of spring seats. The pair of spring seats are disposed on the circumferentially opposite ends of the first elastic member. The pair of spring seats are supported within the window in the sub-plate and the first window in the intermediate disk-like member. The compressing portion is formed in one of the pair of disk-like input members, and is spaced by a first space in the rotating direction from each of the spring seats.
According to yet another aspect of the present invention, the damper disk assembly further has such a feature in which the second relative rotation stop portion is provided with a second space in the rotating direction between the intermediate disk-like member and the pair of disk-like input members. Further, the second space is circumferentially angularly larger than the first space.
According to yet another aspect of the present invention, the first and second elastic members of the damper disk assembly are aligned in the rotating direction. Furthermore, the second elastic members are larger in number than the first elastic member.
According to yet another aspect of the present invention, the damper disk assembly further has such a feature that the first elastic member has a lower rigidity than the rigidity of the second elastic member.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention.