Metal deforming – By application of fluent medium – or energy field – With actuated tool engaging work
Reexamination Certificate
2001-02-21
2002-12-03
Jones, David B. (Department: 3725)
Metal deforming
By application of fluent medium, or energy field
With actuated tool engaging work
C072S058000, C301S124100, C301S127000
Reexamination Certificate
active
06487886
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to an irregular-section tubular body and an axle beam for a torsion beam and a method of manufacturing the same. In particular, the manufacturing method of the present invention manufactures the irregular-section tubular body having a concave portion by press-forming a tubular worked body by applying liquid pressure to an inner surface thereof. The axle beam for a torsion beam of the present invention is joined, if the torsion beam is used in a rear-wheel suspension device of a vehicle, to a pair of trailing arms to attach wheel sides integrally to the axle beam.
2. Description of Related Art
A manufacturing method for an irregular-section tubular body having a concave portion, concaved in a direction perpendicular to axis thereof (hereinafter simply referred “axis perpendicular direction”), at least part of the concave portion being in an axial direction is known. One such manufacturing method includes press-forming a tubular worked body by applying pressure to a liquid sealed in an internal space of a tubular body to an inner surface thereof.
For example, Japanese Patent Laid-open (Koukai) No. 8-90097 discloses a manufacturing method for manufacturing an irregular-section tube having a shape of which varies in a longitudinal direction by usage of liquid pressure. In this manufacturing method, an internal space of a circular tube as the worked body is filled with liquid. Further liquid is then supplied by a pump to apply predetermined pressure P1 to an inner surface of the circular tube. In this condition, the circular tube is press-formed by a pair of upper and lower press molds of predetermined shape and subjected to bending work. Finally, further liquid is supplied into the circular tube to increase the liquid pressure to a predetermined value P2 so that the circular tube bulges or expands along mold surfaces of the upper and lower press molds. Thus, the circular tube is formed into the final irregular-section shape to complete the formation.
Using the above irregular-section tubular body, an axle beam formed and used for a torsion beam as a rear-wheel suspension device of a vehicle is also known.
For example, EP 0650860 B1 discloses, as shown in the attached
FIG. 20
, a torsion beam comprised of a pair of trailing arms
91
attached to wheel sides, and an axle beam
92
each end of which is joined to each of trailing arms
91
, respectively, to connect them integrally to the axle beam. The axle beam
92
is formed into a shape to have a large bending rigidity and small twisting (torsion) rigidity. As shown in the attached
FIG. 21
, the axle beam
92
has cross-section in the axis perpendicular direction of closed section shape including a closed space therein. The cross-section has a star shape in which three wing portions
92
a
extend radially outwardly and equidistantly in a circumferential direction.
However, the conventional manufacturing method of the irregular-section tube body requires both the press-forming process which bends the circular tube by the press molds, and the liquid pressurizing process, which pressurizes liquid in the circular tube by the liquid pressurizing device to obtain the final irregular-section shape of the tubular body. For these reasons, conventional manufacturing methods have been suffering from the disadvantages of the manufacturing process being complex and troublesome.
In addition, since the circular tube is bulged only by the liquid pressure to follow to the mold surfaces, very large liquid pressure is needed for the bulging. For this reason, the liquid pressurizing device used to positively pressurize the liquid, and a large-size extra hydraulic pressing device used to apply a mold fastening force to the press molds against the increasing liquid pressure are necessary. As a result, not only does the equipment become complex and large-sized, but equipment cost increases.
In the above conventional axle beam
92
, as shown in
FIG. 21
, three wing portion
92
a
of the same size and same shape and extending radially outwardly and equidistantly in the circumferential direction are disposed. As a result, it has a cross-section shape in which a centroid and a shearing center coincide. Such coincidence decreases the roll rigidity in the axle beam
92
and creates an over-steer tendency, whereby the steer stabilizing is decreased.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above circumstances and provides a manufacturing method for an irregular-section tubular body which simplifies the manufacturing process and excludes the additional liquid pressurizing device and the extra hydraulic pressing device, thereby avoiding the complex and large-sized equipment and an increase equipment cost are avoided. Also, the present invention provides an axle beam for the torsion beam which provides an increase in the steer stabilizing character by an improvement of the section-shape in the axis perpendicular direction thereof. Further, the present invention provides upper and lower press molds for press-forming a tubular worked body to the axle beam for the torsion beam.
In a first embodiment of the manufacturing method for the irregular-section tubular body comprises a tubular worked body, with a sealed liquid therein, is press-formed by an upper press mold and a lower press mold at least one of which has at least one convex mold portion to form a concave portion concaved in an axis perpendicular (radial) direction at an axial part of the worked body by the convex mold portion; and the press-forming of the worked body to the final tubular body is completed by a one stroke process from a press start point to a press complete point by using a liquid pressure increasing as a decrease of the internal volume of the worked body occurs due to formation of the concave portion, without pressurizing the liquid in the worked body by a pressurizing device.
In the suitable mode, the one stroke process includes a pressure increase process in the former half of the stroke from the press start point to a predetermined point, the pressure increase process press-forming the worked body with the liquid pressure gradually increasing as a decrease of the internal volume of the worked body, due to formation of the concave portion to an inner peripheral surface of the worked body; and a non-pressure increase process in the latter half of stroke from the predetermined point to the press complete point, the non-pressure increase process, following the pressure increase process, press-forming the worked body without applying the increasing liquid pressure to the inner peripheral surface of the worked body.
Here, the press-forming performed without applying the increasing liquid pressure on the inner peripheral surface of the worked body includes a press-forming performed (i) with applying a liquid pressure maintained in a constant pressure on the inner peripheral surface of the worked body, (ii) with applying a gradually decreasing liquid pressure on the inner peripheral surface of the worked body, and (iii) with applying a gradually decreasing liquid pressure on the inner peripheral surface of the worked body from the start to midway through a non-pressure increase process, and without applying liquid pressure on the inner peripheral surface in a final stage of the non-pressure increase.
In the suitable mode, the mold surface of the upper press mold and a mold surface of the lower press mold do not restrain a circumferential part of an outer peripheral surface of the worked body to leave a non-restrain surface at a portion where the concave portion is being formed. Also, in the non-pressure increase process, the liquid pressure applied to the inner peripheral surface of the worked body is maintained at a constant pressure or is decreased, by a liquid-discharge controlling device discharging liquid from the worked body at the predetermined point. Further, in the pressure increase process, with the worked body being set above the lower press mold having the convex mold portio
Sano Tetsuji
Shimada Setsuko
Ueno Yukikazu
Jones David B.
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
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