U.S. patent application number 16/145037 was filed with the patent office on 2019-01-31 for hollow spring member.
This patent application is currently assigned to NHK SPRING CO., LTD.. The applicant listed for this patent is NHK SPRING CO., LTD.. Invention is credited to Daisuke TAKEDA, Masahiro UMEZAWA.
Application Number | 20190030979 16/145037 |
Document ID | / |
Family ID | 59965773 |
Filed Date | 2019-01-31 |
![](/patent/app/20190030979/US20190030979A1-20190131-D00000.png)
![](/patent/app/20190030979/US20190030979A1-20190131-D00001.png)
![](/patent/app/20190030979/US20190030979A1-20190131-D00002.png)
![](/patent/app/20190030979/US20190030979A1-20190131-D00003.png)
![](/patent/app/20190030979/US20190030979A1-20190131-D00004.png)
![](/patent/app/20190030979/US20190030979A1-20190131-D00005.png)
![](/patent/app/20190030979/US20190030979A1-20190131-D00006.png)
United States Patent
Application |
20190030979 |
Kind Code |
A1 |
UMEZAWA; Masahiro ; et
al. |
January 31, 2019 |
HOLLOW SPRING MEMBER
Abstract
On an end portion of a hollow rod, which is a material of a
hollow coil spring, a terminal sealed portion is formed. The
terminal sealed portion has a rotationally symmetric shape in which
an axis passing through the center of the rod is a symmetric axis.
The terminal sealed portion includes an end wall portion, and a
distal-end-center closure portion formed on the axis. In the
distal-end-center closure portion, a distal end opening portion of
the spin-formed rod is joined together and formed as an integral
part. On the axis at the inner surface of the end wall portion, a
recess having a rotationally symmetric shape in which the axis is
the symmetric axis is formed. A thickness of the recess of the end
wall portion is reduced toward the axis.
Inventors: |
UMEZAWA; Masahiro;
(Yokohama-shi, JP) ; TAKEDA; Daisuke;
(Yokohama-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NHK SPRING CO., LTD. |
Yokohama-shi |
|
JP |
|
|
Assignee: |
NHK SPRING CO., LTD.
Yokohama-shi
JP
|
Family ID: |
59965773 |
Appl. No.: |
16/145037 |
Filed: |
September 27, 2018 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2017/013098 |
Mar 29, 2017 |
|
|
|
16145037 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60G 2202/12 20130101;
B60G 2206/8112 20130101; B60G 2206/81035 20130101; B60G 2206/8403
20130101; B60G 21/055 20130101; B60G 2206/8106 20130101; F16F 1/02
20130101; B60G 11/14 20130101; B60G 2202/13 20130101; B60G 2206/724
20130101; B60G 2202/135 20130101; B60G 21/045 20130101; B60G
2206/81 20130101; F16F 2234/02 20130101; B60G 2206/8109 20130101;
C21D 7/06 20130101; F16F 2224/0208 20130101; B60G 2206/80 20130101;
C21D 9/02 20130101; F16F 1/14 20130101; B60G 15/062 20130101; B60G
2206/012 20130101; F16F 1/042 20130101; B60G 2206/427 20130101;
F16F 1/06 20130101; F16F 2226/02 20130101 |
International
Class: |
B60G 21/055 20060101
B60G021/055; F16F 1/06 20060101 F16F001/06; F16F 1/14 20060101
F16F001/14; B60G 11/14 20060101 B60G011/14 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 30, 2016 |
JP |
2016-068043 |
Claims
1. A hollow spring member which is constituted of a hollow rod, and
includes a terminal sealed portion at an end portion of the rod,
the terminal sealed portion having a rotationally symmetric shape
in which an axis passing through a center of the rod is a symmetric
axis, and including: an end wall portion including an end face; a
distal-end-center closure portion existing on the axis at a center
of the end wall portion; and a recess formed on an inner surface of
the end wall portion, and having a rotationally symmetric shape in
which the axis is the symmetric axis.
2. The hollow spring member of claim 1, wherein a thickness of the
recess of the end wall portion is reduced toward the axis, and a
center of the recess is located on the axis.
3. The hollow spring member of claim 1, wherein the hollow spring
member is constituted of the hollow rod formed into a helical
shape, and has a shape of a coil spring.
4. The hollow spring member of claim 1, wherein the hollow spring
member is constituted of the hollow rod including a torsion portion
and an arm portion, and has a shape of a vehicle stabilizer.
5. The hollow spring member of claim 1, wherein the hollow spring
member is constituted of the hollow rod including mounting portions
on both ends of the hollow rod, and has a shape of a torsion rod.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation Application of PCT
Application No. PCT/JP2017/013098, filed Mar. 29, 2017 and based
upon and claiming the benefit of priority from prior Japanese
Patent Application No. 2016-068043, filed Mar. 30, 2016, the entire
contents of all of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0002] The present invention relates to a hollow spring member such
as a coil spring, a stabilizer, or a torsion rod, using a hollow
rod as the material.
2. Description of the Related Art
[0003] A suspension for a vehicle such as a car comprises a coil
spring, an upper spring seat, and a lower spring seat. The upper
spring seat supports an upper end of the coil spring. The lower
spring seat supports a lower end of the coil spring. The coil
spring is compressed between the lower spring seat and the upper
spring seat. Further, the coil spring extends and retracts in
accordance with the magnitude of a load applied between the lower
spring seat and the upper spring seat. In order to reduce fuel
consumption of a vehicle, or enhance the driving performance, there
is an increasing demand for reducing the weight of vehicles. A coil
spring which constitutes the suspension is not an exception, and
reducing the weight of the coil spring is an inevitable
requirement.
[0004] As the means for reducing the weight of a coil spring,
Patent Literature 1 (JP 2007-127227 A) describes a hollow coil
spring using a hollow rod (a hollow wire) as the material. In the
hollow coil spring of Patent Literature 1, an opening at a distal
end of the hollow rod is closed by a cap, which is a part separate
from the rod. Patent Literature 2 (JP 2012-117612 A) describes the
technology of closing an opening at a distal end of a rod of a
hollow coil spring by spinning. The distal end of the rod is formed
to be hemispherical (in a dome shape) by the spinning.
[0005] In the hollow coil spring described in Patent Literature 1,
the opening at the distal end of the rod is closed by a cap, which
is a part separate from the rod. Accordingly, the cap may be
deformed or come off. With the hollow coil spring of Patent
Literature 2, the opening at the distal end of the rod can be
closed by a terminal sealed portion without using a cap. The
present inventors have produced a terminal sealed portion of the
hollow spring member experimentally, and conducted quality
evaluation. As a result of intensive study conducted by the present
inventors, it has been found that a conventional terminal sealed
portion has a problem. For example, when heat treatment such as
quenching and tempering was performed for the hollow spring member,
sealability of the terminal sealed portion had a problem, which is
assumed to have resulted from a rapid temperature change of the rod
affecting the terminal sealed portion.
BRIEF SUMMARY OF THE INVENTION
[0006] Accordingly, an object of the present invention is to
provide a hollow spring member having a terminal sealed portion in
which a distal end of a rod is reliably closed.
[0007] One embodiment of the present invention relates to a hollow
spring member constituted of a hollow rod, and includes a terminal
sealed portion at an end portion of the rod. The terminal sealed
portion has a rotationally symmetric shape in which an axis passing
through the center of the rod is a symmetric axis, and includes an
end wall portion including an end face, a distal-end-center closure
portion, and a recess formed on an inner surface of the end wall
portion. The distal-end-center closure portion is formed on the
axis at the center of the end wall portion. The recess has a
rotationally symmetric shape in which the axis is the symmetric
axis. Moreover, the recess has such a shape that a thickness of the
end wall portion is reduced toward the axis, and the center of the
recess is located on the axis. One embodiment of the hollow spring
member is a hollow coil spring constituted of a hollow rod (wire)
that is formed into a helical shape. Another embodiment of the
hollow spring member is a vehicle stabilizer constituted of a
hollow rod in which a torsion portion and an arm portion are
formed. An example of the hollow spring member may be a torsion
rod.
[0008] Spinning is performed for forming the terminal sealed
portion of the present embodiment. In the spinning, a rod which has
been heated is rotated about an axis of the rod. A spinning jig is
made to contact an outer peripheral surface of the rod which is
rotating, and the spinning jig is moved in a direction along the
axis toward a distal end of the rod. Simultaneously with the above,
the spinning jig is moved toward the center of the rod. By
repeating the spinning more than once, a distal end opening portion
of the rod is gradually spin-formed. As the distal end opening
portion of the rod is finally joined together on the axis (rotation
center) and is formed as an integral part, a hermetically-closed
distal-end-center closure portion is formed.
[0009] According to the hollow spring member of the present
invention, a thickness of the distal-end-center closure portion
formed at the end wall portion of the terminal sealed portion can
be made less than a thickness of a part surrounding the
distal-end-center closure portion due to the recess. Accordingly,
in regard to a temperature change (heating, quenching, etc.,) which
occurs in heat treatment, etc., a part near the distal-end-center
closure portion will have a uniform temperature most quickly. Thus,
an influence of thermal stress resulting from an excessive
temperature difference caused at the distal-end-center closure
portion is suppressed, and sealability of the distal-end-center
closure portion can be ensured.
[0010] Additional objects and advantages of the invention will be
set forth in the description which follows, and in part will be
obvious from the description, or may be learned by practice of the
invention. The objects and advantages of the invention may be
realized and obtained by means of the instrumentalities and
combinations particularly pointed out hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0011] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate embodiments of
the invention, and together with the general description given
above and the detailed description of the embodiments given below,
serve to explain the principles of the invention.
[0012] FIG. 1 is a perspective view showing a part of a vehicle
suspension comprising a hollow coil spring.
[0013] FIG. 2 is a cross-sectional view of a terminal sealed
portion of a hollow coil spring according to a first
embodiment.
[0014] FIG. 3 is a front view of the terminal sealed portion shown
in FIG. 2.
[0015] FIG. 4 is a side view schematically showing a part of a
spinning apparatus.
[0016] FIG. 5 is a cross-sectional view showing an example of an
end portion of a hollow rod before the terminal sealed portion is
formed.
[0017] FIG. 6 is a flowchart showing an example of steps of
manufacturing the hollow coil spring.
[0018] FIG. 7 is a cross-sectional view showing an example of a rod
having a chamfered portion on an inner side of the end portion.
[0019] FIG. 8 is a cross-sectional view showing an example of a rod
having a chamfered portion on an outer side of the end portion.
[0020] FIG. 9 is a cross-sectional view of a terminal sealed
portion according to a second embodiment.
[0021] FIG. 10 is a cross-sectional view of a terminal sealed
portion according to a third embodiment.
[0022] FIG. 11 is a plan view of a vehicle stabilizer according to
a fourth embodiment.
[0023] FIG. 12 is a plan view of a torsion rod according to a fifth
embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0024] A hollow coil spring according to a first embodiment, and a
method of manufacturing the hollow coil spring will described with
reference to FIGS. 1 to 6. The hollow coil spring is an example of
a hollow spring member.
[0025] FIG. 1 shows a part of a McPherson-strut-type suspension 1,
as an example of a vehicle suspension. The suspension 1 of the
present embodiment comprises a hollow coil spring 10, a lower
spring seat 11, an upper spring seat 12, and a shock absorber 13.
The lower spring seat 11 supports a lower end turn portion 10a of
the hollow coil spring 10. The upper spring seat 12 supports an
upper end turn portion 10b of the hollow coil spring 10. The shock
absorber 13 functions as a strut. The hollow coil spring 10 may be
used for a suspension other than the McPherson-strut-type
suspension.
[0026] The hollow coil spring 10 shown in FIG. 1 is fitted to a
vehicle body in such a state that it is compressed between the
lower spring seat 11 and the upper spring seat 12 (i.e., a state in
which a preload is applied). The hollow coil spring 10 elastically
supports a load applied from above in the vehicle body. The hollow
coil spring 10 is compressed between the spring seats 11 and 12 in
accordance with the magnitude of the load. Accordingly, a distance
between the spring seats 11 and 12 is varied in accordance with the
load.
[0027] The hollow coil spring 10 of the present embodiment includes
a hollow rod (a hollow wire) 20 that is helically formed (coiled).
The hollow rod 20 is a material of the hollow coil spring 10, and
is made of spring steel. The specific shape of the hollow coil
spring 10 is not limited to cylindrical, and the hollow coil spring
10 may be formed variously as, for example, a barrel-shaped coil
spring, an hourglass coil spring, a tapered coil spring, a variable
pitch coil spring, and springs of the other shapes.
[0028] A material of the rod 20 is a steel material for a spring
which can be processed by hot working (for example, in a
temperature range in which steel is austenitized). Although a type
of the steel material is not particularly limited, a steel material
for a general suspension coil spring, for example, may be used.
Apart from the spring steel, high-strength steel or steel for
carburizing, for example, may be used. Alternatively, in some
cases, low-carbon steel having a carbon concentration of
approximately 0.15 to 0.60 wt % may be used. In other words,
various steel materials can be applied.
[0029] On both ends of the hollow coil spring 10, more
specifically, end portions 20a and 20b of the rod 20, terminal
sealed portions 30 are formed, respectively. The terminal sealed
portions 30 are formed in advance by a spinning apparatus 60 before
the rod 20 is formed (coiled) helically.
[0030] FIG. 2 shows a cross section of the terminal sealed portion
30 along an axis X1. FIG. 3 is a front view of the terminal sealed
portion 30 shown in FIG. 2. A cross section obtained in a radial
direction perpendicular to the axis X1 of the rod 20 is circular.
As shown in FIG. 2, the terminal sealed portion 30 has a
rotationally symmetric shape in which the axis X1 passing through a
center C (FIG. 3) of the rod 20 is the symmetric axis. More
specifically, the terminal sealed portion 30 has such a shape that
its cross section along the axis X1 does not change even if the
terminal sealed portion 30 is rotated by an arbitrary angle about
the axis X1. The cross section along the axis X1 is intended as a
cross section obtained in a longitudinal direction passing through
the center C (axis X1) of the rod 20. Inside the rod 20, an
enclosed space 31 is formed.
[0031] The terminal sealed portion 30 includes an end wall portion
41 including an end face 40, and an arc-shaped curved surface 42. A
center 40c of the end face 40 is located on the axis X1. The end
face 40 shown in FIG. 2 has such a convex shape that a portion near
the center 40c is slightly projected to the outside. The end face
40 may have a flat shape substantially perpendicular to the axis
X1. Alternatively, the end face 40 may have such a convex shape
that the end face 40 is slightly bulged in a shape of an arc. The
arc-shaped curved surface 42 is formed in a shape of an arc between
an outer peripheral surface 20c of the rod 20 and the end face 40.
The arc-shaped curved surface 42 connects between the outer
peripheral surface 20c of the rod 20 and the end face 40 with a
smooth curved surface. An inner surface 20d of the rod 20 has a
rotationally symmetric shape in which the axis X1 is the symmetric
axis, likewise the outer peripheral surface 20c.
[0032] As shown in FIG. 2, on the axis X1 at the center of the end
wall portion 41, a distal-end-center closure portion 43 is formed.
A distal end (distal end opening portion) 20e of the hollow rod 20
is converged toward the axis X1 by the spinning. As the distal end
(distal end opening portion) 20e of the rod 20 subjected to
spinning merges on the axis X1 to be joined together and formed as
an integral part, the distal-end-center closure portion 43 is
formed. On an inner surface of the end wall portion 41, a recess 45
having a rotationally symmetric shape in which the axis X1 is the
symmetric axis is formed. The recess 45 has such a shape that a
thickness t of the end wall portion 41 is reduced toward the axis
X1. Moreover, the center of the recess 45 (i.e., a distal end 45a
of the recess 45) is located on the axis X1 (symmetric axis),
likewise the distal-end-center closure portion 43. At the center of
the recess 45, the distal-end-center closure portion 43 is formed.
A thickness t1 of the distal-end-center closure portion 43 is less
than the thickness t at a part surrounding the distal-end-center
closure portion 43.
[0033] FIG. 4 is a side view schematically showing a part of a
spinning apparatus 60. By the spinning apparatus 60, the terminal
sealed portion 30 is formed at the end portion 20a of the rod
(hollow wire) 20. FIG. 5 is a cross-sectional view of the rod 20
before the terminal sealed portion 30 is formed. An example of an
outside diameter D of the rod 20 is 19 mm, and an example of a
thickness T is 3 mm. The rod 20 has a rotationally symmetric shape
in which the axis X1 is the symmetric axis.
[0034] The spinning apparatus 60 shown in FIG. 4 includes a lathe
61, heating means 62, and a spinning mechanism 64. The lathe 61
chucks the rod 20, and rotates the rod 20 about the axis X1. The
heating means 62 heats the end portion 20a of the rod 20. The
spinning mechanism 64 comprises a roller-shaped spinning jig 63. An
example of the heating means 62 is a gas burner. A preferred
another example of the heating means 62 is a high-frequency
induction heating coil. In order to heat the end portion 20a of the
rod 20, using the high-frequency induction heating coil is
recommended. In a state in which the spinning jig 63 is in contact
with the rod 20 that is rotating, the spinning jig 63 is driven to
rotate about a rotational axis 63a.
[0035] The end portion 20a of the rod 20 is rotated by the lathe
61. The end portion 20a of the rotating rod 20 is heated to, for
example, austenitizing temperature, by the heating means 62. The
heated rod 20 glows red, and has softness suitable for processing.
The heated rod 20 is rotated about the axis X1 by the lathe 61. A
distal end of the spinning jig 63 is made to contact the outer
peripheral surface 20c of the end portion 20a of the rod 20 that is
heated and rotated in this way. The distal end of the spinning jig
63 is brought to contact a spinning start point F1 (FIGS. 4 and 5),
which is tens of millimeters (for example, 20 mm) away from the
distal end (distal end opening portion) 20e of the rod 20. Further,
the spinning jig 63 is moved in a direction indicated by arrow P2
(i.e., a direction along the axis X1). Simultaneously with the
above, the spinning jig 63 is moved in a radial direction of the
rod 20 toward the axis X1.
[0036] By such movement of the spinning jig 63, the distal end
(distal end opening portion) 20e of the rod 20 is plastically
flowed such that it is gathered toward the axis X1 from the outer
peripheral surface 20c. Further, the distal end (distal end opening
portion) 20e of the rod 20 is spin-formed such that the diameter of
the distal end (distal end opening portion) 20e of the rod 20 is
gradually reduced. The above spinning is performed several times
before the temperature of the rod 20 is dropped excessively. By
doing so, the distal end 20e of the rod 20 subjected to spinning is
joined together on the axis X1 and is formed as an integral part.
As a result, the distal-end-center closure portion 43 that is
sealed is formed at the end wall portion 41.
[0037] The distal-end-center closure portion 43 exists on the axis
X1 at the center of the end wall portion 41. The distal-end-center
closure portion 43 is hermetically closed by the spinning.
Accordingly, it is possible to prevent fluid such as water, oil,
and gas, from entering inside the enclosed space 31 through the
distal-end-center closure portion 43, from outside the end wall
portion 41.
[0038] The end face 40 and the arc-shaped curved surface 42 of the
terminal sealed portion 30 are formed when the terminal sealed
portion 30 is formed by the spinning apparatus 60. More
specifically, the end face 40 and the arc-shaped curved surface 42
can be formed in accordance with a locus of movement of the
spinning jig 63 during the spinning. Accordingly, there is no need
to separately add a different step such as machining for forming
the end face 40 and the arc-shaped curved surface 42. On an inner
surface of the end wall portion 41, the recess 45 having a
rotationally symmetric shape in which the axis X1 is the symmetric
axis is formed.
[0039] The recess 45 can be formed by controlling the movement of
the spinning jig 63 when the distal end 20e of the rod 20 is to be
spin-formed by the spinning jig 63. The distal-end-center closure
portion 43 is located on the axis X1. The thickness at the center
of the end wall portion 41 (thickness t1 of the distal-end-center
closure portion 43) has become smaller than the thickness at a part
surrounding the center due to the recess 45 which has been formed.
Accordingly, in regard to a temperature change (heating or
quenching), which occurs when heat-treating the coil spring 10, a
part near the distal-end-center closure portion 43 will have a
uniform temperature most quickly. In other words, a temperature
variation of the distal-end-center closure portion 43 becomes
small, and thermal stress which is produced in the
distal-end-center closure portion 43 can be reduced. As the thermal
stress is suppressed, sealability of the distal-end-center closure
portion 43 is ensured, and a weakness of the distal-end-center
closure portion 43 can be overcome.
[0040] FIG. 6 shows an example of steps of manufacturing the hollow
coil spring 10. In terminal sealing step S1 in FIG. 6, the terminal
sealed portions 30 are formed on the end portions 20a and 20b of
the rod 20, respectively. After that, in coiling step S2, the rod
20 is formed into a helical shape by a coil spring manufacturing
device. An example of the coil spring manufacturing device
comprises a mandrel which rotates, a rotational head portion, a
chuck configured to fix a distal end of the rod onto the rotational
head portion, a guide which guides the rod, and the like.
[0041] In coiling step S2, the distal end (terminal sealed portion
30) of the rod 20 is fixed to the rotational head portion by the
chuck of the coil spring manufacturing device. Further, by moving
the guide in an axial direction of the mandrel while the mandrel is
being rotated, the rod 20 is wound around the mandrel like a coil
at a predetermined pitch. More specifically, the coil spring 10 is
formed helically by hot working. The formed coil spring 10 is
removed from the mandrel.
[0042] In heat treatment step S3 in FIG. 6, heat treatment such as
quenching and tempering is performed for the coil spring 10. By
this heat treatment, a heat-treated structure of steel having
hardness necessary as a spring is formed. In shot peening step S4,
shot peening is performed by a shot peening machine. By the shot
peening, a compressive residual stress is produced on a surface of
the coil spring 10. Further, in setting step S5, setting is
performed for the coil spring 10. After coating has been applied to
the coil spring 10 in coating step S6, the coil spring 10 is
inspected in inspection step S7, and the coil spring 10 meeting the
standard is accepted as a product.
[0043] FIG. 7 shows an example in which a chamfered portion 70 is
formed on an inner side of the end portion 20a of the rod 20. When
the rod 20 has the outside diameter D of .PHI.19 mm, and the
thickness T of 3 mm, a length L1 of the chamfered portion 70 is set
to 2 mm. The chamfered portion 70 may have a length other than the
above. The terminal sealed portion 30 having the recess 45 may be
formed by performing the spinning on the end portion 20a of the rod
20, which has the chamfered portion 70 on the inner side of the rod
20 as in this example, by the spinning apparatus 60 shown in FIG.
4.
[0044] FIG. 8 shows an example in which a chamfered portion 71 is
formed on an outer side of the end portion 20a of the rod 20. When
the rod 20 has the outside diameter D of 419 mm, and the thickness
T of 3 mm, a length L2 of the chamfered portion 71 is set to 2 mm.
The chamfered portion 71 may have a length other than the above.
The terminal sealed portion 30 having the recess 45 may be formed
by performing the spinning on the end portion 20a of the rod 20,
which has the chamfered portion 71 on the outer side of the rod 20
as in this example, by the spinning apparatus 60 shown in FIG.
4.
[0045] FIG. 9 shows a cross section of a terminal sealed portion
30A according to a second embodiment. The terminal sealed portion
30A also has a rotationally symmetric shape in which an axis X1 of
a rod 20 is the symmetric axis, likewise the terminal sealed
portion 30 of the first embodiment. More specifically, the terminal
sealed portion 30A includes an end wall portion 41, an arc-shaped
curved surface 42, a distal-end-center closure portion 43, and a
recess 45 in a cross section along the axis X1 (symmetric axis).
The end wall portion 41 includes an end face 40a, which is
perpendicular to the axis X1, and is substantially flat. The
arc-shaped curved surface 42 is contiguous with the end face 40a
and an outer peripheral surface 20c. The distal-end-center closure
portion 43 is formed on the axis X1 at the center of the end wall
portion 41. The recess 45 has a rotationally symmetric shape in
which the axis X1 is the symmetric axis. The center of the recess
45 (i.e., a distal end 45a of the recess 45) is located on the axis
X1. The end face 40a which is substantially flat can be formed by
pressing a jig having a flat pressure surface, for example, against
the end wall portion 41.
[0046] FIG. 10 shows a cross section of a terminal sealed portion
30B according to a third embodiment. The terminal sealed portion
30B also forms a rotationally symmetric shape in which an axis X1
of a rod 20 is a symmetric axis. More specifically, the terminal
sealed portion 30B includes an end wall portion 41, an arc-shaped
curved surface 42, a distal-end-center closure portion 43, and a
recess 45 in a cross section along the axis X1 (symmetric axis).
The end wall portion 41 includes an end face 40a, which is
perpendicular to the axis X1, and is substantially flat. The
arc-shaped curved surface 42 is contiguous with the end face 40a
and an outer peripheral surface 20c. The distal-end-center closure
portion 43 is formed on the axis X1 at the center of the end wall
portion 41. The recess 45 has a rotationally symmetric shape in
which the axis X1 is the symmetric axis. The center of the recess
45 (i.e., a distal end 45a of the recess 45) is located on the axis
X1. A thickness at the center of the recess 45, more specifically,
a thickness t2 of the distal-end-center closure portion 43 is less
than a thickness t at a part surrounding the distal-end-center
closure portion 43.
[0047] FIG. 11 shows a hollow stabilizer 80 for a vehicle according
to a fourth embodiment. The hollow stabilizer 80 is an example of a
hollow spring member, and is arranged in a suspension mechanism
part of a vehicle. The hollow stabilizer 80 is constituted of a
hollow rod 20, and includes a torsion portion 81 extending in a
width direction of the vehicle, arm portions 82 and 83 extending
from both ends of the torsion portion 81, and mounting portions 84
and 85. Each of the mounting portions 84 and 85 is formed by
processing an end portion of the hollow rod 20 having a terminal
sealed portion similar to that of the above embodiments.
[0048] FIG. 12 shows a hollow torsion rod (torsion bar) 90
according to a fifth embodiment. The hollow torsion rod 90 is an
example of a hollow spring member, and a torsional load is applied
to the hollow torsion rod 90. The torsion rod 90 is constituted of
a hollow rod 20. Mounting portions 91 and 92 are provided on both
ends of the hollow torsion rod 90. Each of the mounting portions 91
and 92 is formed by processing an end portion of the hollow rod 20
having a terminal sealed portion similar to that of the above
embodiments.
[0049] The present invention is also applicable to a hollow spring
member such as a stabilizer or a torsion rod constituted of a
hollow rod, for example, other than the hollow coil spring. Also,
various shapes may be adopted for the shape of the end wall portion
and the shape of the recess of the terminal sealed portion without
departing from the spirit of the invention. Further, the diameter
and the type of steel of the rod (hollow wire or hollow rod), which
is the material of the hollow spring member, are not limited to
those described in the embodiments.
[0050] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *