1. Field of the Invention
The present invention relates to a torsion beam suspension comprising: vertically pivotable left and right trailing arms extending in a longitudinal direction of a vehicle body; a torsion beam extending in a lateral direction of the vehicle body, the opposite ends of which are connected to the left and right trailing arms; a spindle support plate welded to each of the left and right trailing arms; and a spindle fixed to the spindle support plate so as to axially support a wheel.
2. Description of the Related Art
A conventional torsion beam suspension is known from Japanese Patent Application Laid-open No. 2000-94917.
In the conventional torsion beam suspension, a trailing arm is a hollow member made by combining and integrally welding press-formed upper and lower plates, and a bracket formed from an angular U-shaped metal plate is welded to the trailing arm to secure a spindle support plate which supports a wheel.
However, the above-mentioned conventional design has a problem in that the spindle axle line and the trailing arm major cross-section are largely offset with the angular U-shaped bracket disposed therebetween, so that the bracket must have a wall thick enough to reliably support a load from the wheel, resulting in an increased weight.
Therefore, it is conceivable that the angular U-shaped bracket ii eliminated, a spindle support plate is welded to an end of the trailing arm, and the spindle is fixed with bolt to the spindle support plate through a mounting flange integral with the spindle. In doing so, not only is the weight reduced by eliminating the heavy bracket, but it also becomes possible to bring the spindle axle line and the trailing arm major cross-section closer to each other, resulting in an advantageous strength.
However, in reality, when the trailing arm end is welded to the spindle support plate, the spindle mounting surface of the spindle support plate may be warped by the heat of welding. In order to prevent this thermal warping, it is necessary to make the spindle support plate sufficiently thick (for instance, over 10 mm), so that the total thickness of the spindle support plate and the mounting flange (for instance, 10 mm thick) integral with the spindle which is connected to the spindle support plate, becomes over 20 mm, disadvantageously resulting in no reduction in weight. Moreover, there is also a problem that welding property is deteriorated due to a large difference in thickness of the trailing arm having a small wall thickness and the spindle support plate having a large wall thickness.
In order to solve the problems of thermal warp and weight, the spindle support plate can be machined to be flat and thinner after welding the spindle support plate to the trailing arm end. However, in this case, because the spindle axle line is the reference for the surface cut, it is necessary to rotate the whole trailing arm in conducting the surface cut, so that machining becomes very complicated and costly.
It is also conceivable to eliminate the spindle support plate, and weld the spindle-mounting flange assembly directly to the trailing arm, but it is still necessary that the mounting flange thickness be for instance 13 mm or more, in order to solve the problem of thermal warp. Therefore, a weight increase is unavoidable.
Accordingly, an object of the present invention is to reduce weight by reducing the wall thickness of the spindle support plate which is directly welded to the end of the trailing arm, and to effectively prevent thermal warp which accompanies welding.
In order to achieve the above object, according to a first feature of the invention, a torsion beam suspension comprising: vertically pivotable left and right trailing arms extending in a longitudinal direction of a vehicle body; a torsion beam extending in a lateral direction of the vehicle body, the opposite ends of which are connected to the left and right trailing arms; a spindle support plate welded to each of the left and right trailing arms; and a spindle fixed to the spindle support plate so as to axially support a wheel, wherein a bent flange is formed around an outer periphery of a body of the spindle support plate and is fitted around an outer periphery of an end of the trailing arm, the bent flange being welded to the trailing arm.
With this arrangement, because the bent flange is formed around the outer periphery of the body of the spindle support plate and is fitted around the outer periphery of the end of the trailing arm, the bent flange being welded to the trailing arm, the heat from welding is blocked by the bent flange of the spindle support plate, to thereby prevent the heat from reaching the body. Therefore, thermal warp of the body of the spindle support plate which retains the spindle is prevented, and not only can the spindle mounting precision be improved without cutting the spindle support plate surface, but the support plate thickness can be reduced to reduce the weight. Moreover, welding property is improved because the difference in wall thickness compared with the trailing arm is reduced.
According to a second feature of the invention, in addition to the arrangement of the first feature, a spindle support hole is formed in the body of the spindle support plate by burring, and the spindle is press-fitted into the spindle support hole.
With this arrangement, the spindle support hole can be formed in the spindle support plate by burring because the spindle support plate is made thinner. As a result, the spindle can be retained by press-fitting it into the burring-formed spindle support hole without forming a spindle-mounting flange assembly to retain the spindle support plate, that is, the spindle weight can be reduced by the weight of the eliminated mounting flange.
Furthermore, according to a third feature of the invention, in addition to the arrangement of the second feature, a tip end of the spindle press-fitted into the spindle support hole passes through the trailing arm and projects out of the trailing arm, a projecting portion of the spindle being welded to the trailing arm.
With this arrangement, the tip end of the press-fitted spindle passes through and projects out of the trailing arm before being welded to the trailing arm to firmly connect the spindle to the trailing arm, whereby the heat of welding does not affect the spindle support plate.