Land vehicles – Wheeled – Running gear
Reexamination Certificate
2000-05-25
2001-07-31
Dickson, Paul N. (Department: 3618)
Land vehicles
Wheeled
Running gear
C280S124154, C280S124166
Reexamination Certificate
active
06267397
ABSTRACT:
TECHNICAL FIELD
The present invention relates especially to a torsion beam type rear suspension apparatus in suspension apparatuses for a vehicle.
BACKGROUND ART
As a conventional suspension apparatus for a vehicle, a torsion beam type rear suspension apparatus which has a torsion beam coupled between right and left rear wheels, and a pair of trailing arms which are formed into a planar shape to allow a displacement in the widthwise direction of the vehicle body and extend from the two end portions of the torsion beam in the longitudinal direction of the entire vehicle body is known (see Japanese Patent Laid-Open No. 4-283114). In this suspension apparatus, the free end portions of the trailing arms are supported on a vehicle body frame via bushings, and the rear end portions of the trailing arms are joined to the right and left end portions of the torsion beam by welding.
The torsion beam type rear suspension apparatus is mounted in a light car or the like since it has a simple structure and is inexpensive. Also, such rear suspension apparatus can decrease the floor height and can assure a broad rear cargo space or the like, since the coil spring level can lower by disposing the center of the coil diameter of each coil spring not immediately above the trailing arm or torsion beam but to have an offset on the front or rear side of the vehicle body with respect to the torsion beam. Hence, demands in recent wagon and box type vehicles are increasing.
However, in the technique of the aforementioned reference, when a spring seat or its bracket is formed at a corner portion, the actual effective length of the trailing arm becomes short, and torsional elasticity increases, resulting in poor riding comfort. For this reason, each trailing arm may be prolonged in correspondence with a decrease in effective length, but such long trailing arm disturbs layout efficiency. On the other hand, the torsion beam may be prolonged. However, the torsional elasticity of the torsion beam then becomes too low, resulting in poor driving stability, or the mechanical strength of that portion of the torsion beam on which the torsional stress is concentrated must be increased and may lead to high cost resulting from an increase in weight.
In the suspension apparatus in which the center of the coil diameter of each coil spring is disposed to have an offset on the front side of the vehicle body with respect to the torsion beam, since the torsion of the torsion beam is larger than that of the suspension apparatus in which the center of the coil diameter of each coil spring is disposed to have an offset on the rear side of the vehicle body, the separation of the joint surface between the spring seat and torsion beam becomes large. Even when their joint strength is increased, the torsional stress is concentrated, and the joint surface of the torsion beam cracks.
DISCLOSURE OF INVENTION
The present invention has been made in consideration of the aforementioned problems, and has as its object to provide a suspension apparatus for a vehicle which can suppress a spring seat from separating and a torsion beam from cracking due to concentration of the torsional stress on the torsion beam, and can maintain high suspension performance by a lightweight and inexpensive structure.
In order to solve the above problems and to achieve the object, a suspension apparatus for a vehicle according to the present invention comprises the following arrangement.
That is, a torsion beam type rear suspension apparatus for a vehicle comprises a torsion beam which is coupled between right and left wheels and allows a torsional displacement produced between the wheels, a pair of right and left, planar trailing arms, which extend from two end portions of the torsion beam to predetermined positions in a back-and-forth direction of a vehicle body, and are pivotally and axially supported at the predetermined positions to allow a displacement in a lateral direction of the vehicle body, and coil spring seats joined to one side surface of the torsion beam on a front side of the vehicle body, and the torsion beam and the coil spring seats are joined via stress relaxing means.
With this structure, high suspension performance can be maintained by a lightweight and inexpensive structure while suppressing the spring seat from separating and the torsion beam from cracking due to concentration of the torsional stress on the torsion beam.
Preferably, the coil spring seats are provided to be spaced a predetermined spacing from the trailing arms in a widthwise direction of the vehicle body, and the apparatus further comprises dampers, lower end portions of which are pivotally and axially supported in spaces with the predetermined spacing.
With this structure, since the coil spring seat can have an offset with respect to the torsion beam, a lower floor height can be assured, and can broaden the rear cargo space or the like. Since the coil spring seat is not coupled to the trailing arm, a sufficiently large effective length can be assured and a compact suspension structure can be realized even when the trailing arm is shortened.
Furthermore, since the coil spring seat is cantilever-supported on the torsion beam, a force for separating the coil spring seat from the torsion beam acts due to the counter force of the coil spring and the torsion of the torsion beam, but such force can be effectively prevented by the damper.
As a result, cracking and fatigue of the joint portion between the torsion beam and coil spring seat can be eliminated, and no extra rigidity improvement such as an additional reinforcement plate for improving the mechanical strength of the joint portion is required, thus reducing the unsprung weight while assuring a large effective length of the trailing arm.
Preferably, the lower end portions of the dampers are axially supported by lower end portions of the trailing arms.
With this structure, in addition to the aforementioned effects, since the damper lower end portion is axially supported by the trailing arm lower end portion, the correcting force of the damper effectively acts as an upward bending force on the torsion beam via the coil spring seat, and a large damper length can be assured.
Preferably, the dampers are axially supported via pivot allowing means so as to be pivotal about axial centers thereof.
With this structure, in addition to the aforementioned effects, since pivotal motion of the damper is allowed only about its axial center, the damper can satisfactorily correct motions of the torsion beam and trailing arm.
Preferably, the dampers are disposed toward a direction range from a direction substantially parallel to upright surfaces of the trailing arms to an inward direction of the vehicle body.
With this structure, in addition to the aforementioned effects, the stretching direction of the damper can be restricted in a predetermined direction, and restriction of the stretching direction can assure an appropriate correcting force with respect to the torsion beam and trailing arm.
Preferably, joint seats with the torsion beam are formed on the coil spring seats to define an upward slope from an outer side to an inner side in a widthwise direction of the vehicle body.
With this structure, in addition to the aforementioned effects, high suspension performance can be maintained by a lightweight and inexpensive structure while suppressing the spring seat from separating in the outward widthwise direction of the vehicle body and the torsion beam from cracking due to concentration of the torsional stress on the torsion beam.
Preferably, each of the coil spring seats has a box shape, which has a rear flange portion that stands upright on a rear edge in the back-and-forth direction of the vehicle body, and inner and outer flange portions that stand upright on two ends in the widthwise direction of the vehicle body, and a back surface of at least the rear flange portion is joined to a front surface of the torsion beam in the back-and-forth direction of the vehicle body.
With this structure, the coil spring seat can be laid out to hav
Hamada Kenji
Komiya Katsuyuki
Koyama Toshihide
Brooks & Kushman P.C.
Dickson Paul N.
Mazda Motor Corporation
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