DESCRIPTION
TITLE OF INVENTION: STRUCTURAL MEMBER
TECHNICAL FIELD
[0001] The present invention relates to a structural
member preferred for use with, for example, a
structural joint member having plural projecting
portions integrally formed on an outer peripheral
face of a hollow main tube part.
BACKGROUND ART
[0002] Due to environmental conservation issues,
weight reduction of structural member is demanded.
Among structural members, structural members for
transportation apparatuses, particularly for
automobile, are strongly demanded to be reduced in
weight because the effects of weight reduction of
structural members for automobiles are large, such as
fuel consumption improvement and exhaust gas and
carbon dioxide emission reduction.
[0003] Weight reduction of a structural member can
be achieved by enhancing the strength of material of
the structural member and thinning of the structural
member. Regarding destruction of the structural
member accompanying thinning of the structural member,
namely, plastic deformation and fatigue failure of
the structural member, the insufficient strength
decreased due to thinning can be compensated by
material strength enhancement of the structural
member. However, regarding deflection of the
structural member, namely, elastic deformation of the
structural member, it is not possible to compensate
insufficient rigidity decreased due to thinning by
material strength enhancement of the structural
member.
[0004] In particular, in the case of a structural
member for automobiles, even when the material of the
structural member is increased in strength to obtain
the same strength of the entire structural member as
that before thinning, if the geometrical structure of
the entire thinned structural member is the same as
that before thinning, and the rigidity of the entire
thinned structural member has decreased, this causes
noise and/or vibrations.
[0005] Further, among structural members for
automobile, if rigidity decreases due to thinning of
vehicle body member, chassis member, or the like,
there is also a problem that operating stability
decreases.
[0006] Therefore, to improve the strength as the
entire structure without decreasing the rigidity
thereof, it is necessary to enhance the strength of
structural members forming the entire structure, and
prevent reduction of rigidity of the entire structure
by changing the geometrical structure of the entire
structure.
[0007] As a method for preventing decrease in
rigidity of the entire structure formed of structural
members even when the structural members are thinned,
it is effective to improve rigidity of coupling
members, and to use a joint member having a hollow
structure in particular.
[0008] As a metal processing method for obtaining a
structural member having a hollow structure, there
are casting, welding of plate materials, hydroforming,
and so on.
[0009] Casting has a difficulty in thinning as
compared to other metal processing methods. Further,
elements for securing fluidity are added to an alloy
for casting in either case of iron-based alloy and
light-weight alloy, and thus it is difficult to
enhance the strength of the material itself as
compared to an elongated material or. an extruded
material of steel plate material or light-weight
alloy. On the other hand, die-casting which allows
thinning has a difficulty in obtaining a structural
member having a hollow shape.
[0010] Further, when plate materials are welded to
produce a structural member, although freedom in
shape of the structural member is high, the welding
length becomes long when the structural member is
produced to have a hollow shape, and thus there is a
problem that it is inferior in productivity.
[0011] Accordingly, it is effective to form the
entire structure, for example the automobile body or
chassis, by welding a structural joint member which
is hydroformed.
[0012] Patent Document 1 and Non-patent Document 1
disclose a hydroformed body having plural projecting
portions on a main tube part by shaping an element
tube by hydroforming.
[0013] Further, Patent Document 2 discloses a bulgeformed
product of polygonal tube for joint member,
employing a hollow material formed of aluminum or an
alloy thereof extruded in a, polygonal shape in
advance as a raw material,. where two expanded
portions are formed in this polygonal hollow material
by bulge forming.
CITATION LIST
PATENT LITERATURE
[0014] Patent Literature 1: Japanese Examined Patent
Application Publication No. 58-167033
Patent Literature 2: Japanese Unexamined Utility
Model Application Publication No. 5-84420
NON PATENT LITERATURE
[0015] Non Patent Literature 1: Tube Forming-
Secondary Formation and Product Design of a Tube
Member-, The Japan Society for Technology of
Plasticity, Corona Publishing (1992)
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0016] The hydroformed body disclosed in Patent
Document 1 has two projecting portions on the main
tube part. However, these two projecting portions
are disposed apart from each other, and there is a
problem that a structure branching from a portion in
the hydroformed body being an origin cannot be formed.
[0017] The hydroformed body described in Non-patent
Document 1 has two projecting portions on the main
tube part, and the disposed positions of the two
projecting portions are close. Thus, it has a
structure branching from a;portion in the hydroformed
body being an origin.
[0018] However, on the hydroformed body described in
Non-patent Document 1, respective projecting heights
of the two projecting portions are so short that it
is not possible to couple another part to the tip of
the projecting portions by welding or the like, and
hence it is not possible to be used as a joint member.
[0019] The bulge-formed product described in Patent
Document 2 has a structure such that the aluminum
extruded material having a hollow hexagonal cross
section has two expanded portions, and the. two
expanded portions have the same shape and are at the
same positions in a longitudinal direction of the
aluminum extruded material.
[0020] However, on the bulge-formed product of
polygonal tube for joint member described in Patent
Document 2, since the two expanded portions have the
same shape and are at the same positions in the
longitudinal direction of the aluminum extruded
material, it is difficult to secure projecting
heights of the expanded portions during bulge forming,
and a desired projecting height cannot be obtained.
[0021] The present invention has been made to solve
the above-described problems, and an object thereof
is to provide a structural member which has plural
projecting portions branching from a portion of the
structural member being an origin, and is capable of
securing a desired projecting height of the plural
projecting portions, for example a necessary height
for coupling another part by welding or the like.
SOLUTION TO PROBLEM
[0022] The gist of the present invention is as
follows.
(1) A structural member including:
a hollow main tube part; and
at least two projecting portions formed
integrally on an outer peripheral face of the main
tube part, in which
the two projecting portions are disposed at an
angle of 30 degrees or more and less than 180 degrees
around a main axis of the main tube part, and
both intersecting planes, which are projecting
planes of end faces of the two projecting portions
toward the main tube part, share a plane
perpendicular to the main axis of the main tube part
only in portions of the intersecting planes.
(2) The structural member according to (1), in
which the two projecting portions are disposed at an
angle of 60 degrees or more and 120 degrees or less
around the main axis of the main tube part.
(3) The structural member according to (1),
further including another projecting portion
integrally formed on an outer peripheral face of the
main tube part, in which all intersecting planes,
which are projecting planes of end faces of the two
projecting portions and the other projecting portion
toward the main tube part, share a plane
perpendicular to the main axis of the main tube part
only in portions of the intersecting planes.
(4) The structural member according to (1), in
which the main tube part and the two projecting
portions are formed by hydroforming an element tube.
(5) The structural member according to (4), in
which an outside diameter of the element tube is D,
and areas of the portions of the intersecting planes
are 30% or more and 90% or less relative to an area
of each of the intersecting planes and a projecting
height of each of the two projecting portions is 0.3D
or higher.
(6) The structural member according to (5), in
which the projecting height of each of the two
projecting portions is 0.8D or lower.
(7) The structural member according to (4), in
which a tensile strength of the element tube is 340
MPa or more and 850 MPa or less.
(8) The structural member according to (1), in
which the main tube part is provided with a curved
joining face or an oblique flat joining face which
sequentially joins the two projecting portions.
(9) The structural member according to (8), in
which the curved joining face or the oblique flat
joining face has a gradually varying portion which
becomes smaller in area toward a tube end of the main
tube part.
(10) The structural member according to (9), in
which the length of the gradually varying portion is
0.2D or longer and 2.OD or shorter in a direction
parallel to the main axis of the main tube part.
(11) The structural member according to (8), in
which the curved joining face or the oblique flat
joining face is provided with a circumferential rib
which projects inward of the main tube part.
(12) The structural member according to (8), in
which the curved joining face or the oblique flat
joining face is provided with a circumferential rib
which projects outward of the main tube part.
(13) The structural member according to (1), in
which at least one of the two projecting portions has
a welding seat face protruding portion on at least a
portion in a circumferential direction.
(14) The structural member according to (1), in
which at least one of the two projecting portions has
at least one leaf spring welding seat face portion in
a circumferential direction.
(15) The structural member according to (1), in
which at least one of the two projecting portions has
a welding margin formed by opening at least a portion
of an end face of the projecting portions.
ADVANTAGEOUS EFFECTS OF INVENTION
[0023] According to the present invention, it is
possible to provide a structural member which has
plural projecting portions branching from a portion
of the structural member being an origin, and is
capable of securing a desired projecting height of
the plural projecting portions, for example a
necessary height for coupling another part by welding
or the like.
BRIEF DESCRIPTION OF DRAWINGS
[0024] [Fig. 1] Fig. 1 is a perspective view
illustrating an automobile chassis joint according to
a first embodiment.
[Fig. 2] Fig. 2 is a cross-sectional view
taken along line I-I of Fig. 1.
[Fig. 3] Fig. 3 is a cross-sectional view
taken along line II-II of Fig. 1.
[Fig. 4] Fig. 4 is a cross-sectional view
taken along line III-III of Fig. 1.
[Fig. 5] Fig. 5 is a perspective view
illustrating a hydroformed body in which both of two
intersecting planes do not share a plane
perpendicular to a main axis of a main tube part.
[Fig. 6] Fig. 6 is a perspective view
illustrating a hydroformed body in which both of the
two intersecting planes share a plane perpendicular
to the main axis of the main tube part via the entire
intersecting planes.
[Fig. 7] Fig. 7 is a perspective view
illustrating a hydroformed body in which a portion of
one of the two intersecting planes and the whole of
the other intersecting plane share a plane
perpendicular to the main axis of the main tube part.
[Fig. 8] Fig. 8 is a perspective view
illustrating a three-branch automobile chassis joint
according to a second embodiment.
[Fig. 9A] Fig. 9A is a perspective view
illustrating an automobile door surrounding joint
according to a third embodiment.
[Fig. 9B] Fig. 9B is a cross-sectional view
taken along line IV-IV of Fig. 9A.
[Fig. 10] Fig. 10 is a perspective view
illustrating an automobile chassis joint according to
a fourth embodiment.
[Fig. 11] Fig. 11 is a cross-sectional view
taken along line V-V of Fig. 10.
[Fig. 12] Fig. 12 is a cross-sectional view
taken along line VI-VI of Fig. 10.
[Fig. 13] Fig. 13 is a cross-sectional view
taken along line VII-VII of Fig. 10.
[Fig. 14] Fig. 14 is a view describing a
curved joining face and a gradually varying portion
which are provided in an automobile chassis joint
according to a fourth embodiment.
[Fig. 15A] Fig. 15A is a cross-sectional view
- 10 -
taken along line VIII-VIII of Fig. 14.
[Fig. 15B] Fig. 15B is a cross-sectional view
taken along line IX-IX of Fig. 14.
[Fig. 15C] Fig. 15C is a cross-sectional view
taken along line X-X of Fig. 14.
[Fig. 15D] Fig. 15D is a cross-sectional view
taken along line XI-XI of Fig. 14.
[Fig. 16] Fig. 16 is a perspective view
illustrating an automobile chassis joint according to
a fifth embodiment.
[Fig. 17A] Fig. 17A is a cross-sectional view
taken along line XII-XII of Fig. 16.
[Fig. 17B] Fig. 17B is a cross-sectional view
taken along line XIII-XIII of Fig. 16.
[Fig. 17C] Fig. 17C is a cross-sectional view
taken along line XIV-XIV of Fig. 16.
[Fig. 18] Fig. 18 is a perspective view
illustrating an automobile chassis joint according to
a sixth embodiment.
[Fig. 19A] Fig. 19A is a cross-sectional view
taken along line XV-XV of Fig. 18.
[Fig. 19B] Fig. 19B is a cross-sectional view
taken along line XVI-XVI of Fig. 18.
[Fig. 19C] Fig. 19C is a cross-sectional view
taken along line XVII-XVII of Fig. 18.
[Fig. 20A] Fig. 20A is a view illustrating an
example of providing a circumferential rib on a
curved joining face provided in a region where the
intersecting plane of a projecting portion and the
- 11 -
intersecting plane of another projecting portion do
not share a plane perpendicular to the main axis of
the main tube part.
[Fig. 20B] Fig. 20B is a view illustrating an
example of providing the circumferential rib on the
curved joining face provided in the region where the
intersecting plane of the projecting portion and the
intersecting plane of the other projecting portion do
not share a plane perpendicular to the main axis of
the main tube part.
[Fig. 21] Fig. 21 is a perspective view
illustrating an automobile chassis joint according to
a seventh embodiment.
[Fig. 22A] Fig. 22A is a cross-sectional view
taken along line XVIII-XVIII of Fig. 21.
[Fig. 22B] Fig. 22B is a cross-sectional view
taken along line XIX-XIX of Fig. 21.
[Fig. 22C] Fig. 22C is a cross-sectional view
taken along line XX-XX of Fig. 21.
[Fig. 23] Fig. 23 is a perspective view
illustrating an automobile chassis joint according to
an eighth embodiment.
[Fig. 24A] Fig. 24A is a cross-sectional view
taken along line XXI-XXI of Fig. 23.
[Fig. 24B] Fig. 24B is a cross-sectional view
taken along line XXII-XXII of Fig. 23.
[Fig. 25] Fig. 25 is a perspective view
illustrating an automobile chassis joint according to
the ninth embodiment.
- 12 -
[Fig. 26] Fig. 26 is a cross-sectional view
taken along line XXIII-XXIII of Fig. 25.
[Fig. 27] Fig. 27 is a perspective view
illustrating an automobile chassis joint according to
a modification example of the ninth embodiment.
[Fig. 28] Fig. 28 is a perspective view
illustrating an automobile chassis joint according to
a modification example of the ninth embodiment.
[Fig. 29] Fig. 29 is a cross-sectional view
taken along line XXIV-XXIV of Fig. 28.
[Fig. 30] Fig. 30 is a perspective view
illustrating an automobile chassis joint according to
a tenth embodiment.
[Fig. 31] Fig. 31 is a perspective view
illustrating an automobile chassis joint according to
a modification example of the tenth embodiment.
DESCRIPTION OF EMBODIMENTS
[0025] Hereinafter, preferred embodiments of the
present invention will be described with reference to
the attached drawings.
The present inventors prepared hydroformed bodies
while varying thicknesses and materials of element
tubes before hydroforming and positions and numbers
of projecting portions, examined projecting heights
of plural projecting portions formed through the
hydroforming, and conducted dedicated studies on
hydroformed bodies which can be used as a structural
hydroformed joint member.
- 13 -
[0026] As a result, it was found that when partial
regions in predetermined ranges of respective
projecting portions share a plane perpendicular to
the main axis of a main tube part, the respective
projecting heights of the projecting portions become
equal to or higher than a predetermined length
necessary for connecting with an opponent part to be
coupled.
[0027] Further, it was also found that the shape of
the main tube part connecting the respective
projecting portions enables to improve rigidity of
the entire hydroformed body, and that the shapes of
ends and end faces of the projecting portions enable
to improve weldability with an opponent part to be
welded to the projecting portion.
[0028] -First Embodiment-
Fig. 1 is a perspective view illustrating an
automobile chassis joint which is a structural
hydroformed joint member according to a first
embodiment applying the present invention. In Fig. 1,
numeral 10 denotes the automobile chassis joint
(hereinafter referred to as a "chassis joint"). The
chassis joint 10 has a hollow main tube part 20 and
projecting portions 30a, 30b concentrated on the main
tube part 20.
[0029] The chassis joint 10 is obtained by
hydroforming an element tube with a thickness of 2.3
mm, an outside diameter of 114.3 mm, and a length of
1500 mm.
- 14 -
[0030] The material of the element tube is a steel
material with a tensile strength of 390 MPa class
(total elongation: 34%). However, the material is
not limited thereto. Since the chassis joint 10 has
a hollow structure, decrease in its rigidity is small
when it is thinned, and thus the material of the
element tube is preferred to be a high-tensile steel
with a tensile strength of 340 MPa or higher class
and 850 MPa or lower class. When the tensile
strength of the element tube is less than 340 MPa, it
becomes necessary to increase the thickness of the
element tube for securing the strength of the chassis
joint after hydroforming, and the weight reduction
ratio decreases. On the other hand, when the tensile
strength of the element tube is more than 850 MPa,
hydroformability decreases due to decrease in the
maximum expansion ratio of the element tube.
[0031] Further, the conditions of the hydroforming
may be set in an ordinary manner. For example, the
chassis joint 10 was formed from a mechanical
structural carbon steel tube, STKM13B, with an
outside diameter of 114.3 mm and a thickness of 2.9
mm, and was formed with an axial extrusion amount of
150 mm on both left and right sides, and internal
pressure of 100 MPa at a maximum. Further, if a gap
exists between a projecting portion and a cavity, the
gap may cause a burst, and thus a counter punch is
used in each of the projecting portions. The load of
the counter punch is 300 kN at a maximum.
- 15 -
[0032] Although not illustrated specifically, an end
of the projecting portion 30a is coupled by welding
to an end of B pillar of an automobile. Further, an
end of the projecting portion 30b is coupled by
welding to an end of cross member of an automobile.
[0033] The projecting portions 30a, 30b integrally
formed on an outer peripheral face of the main tube
part 20 are disposed to be shifted by 90 degrees
around the main axis 40 of the main tube part 20.
Note that the main axis 40 is a center line position
of the element tube before forming.
[0034] Further, in a region indicated by K in Fig. 1,
the projecting portions 30a, 30b overlap by positions
in a longitudinal direction of the chassis joint 10,
and the chassis joint 10 has a structure branching
from a portion of the chassis joint 10, namely, the
region indicated by K being an origin. That is, both
an intersecting plane 35a of the projecting portion
30a and an intersecting plane 35b of the projecting
portion 30b share a plane perpendicular to the main
axis 40 only in portions. Here, the intersecting
planes 35a, 35b are respective projecting planes of
an end face 33a of the projecting portion 30a and an
end face 33b of the projecting portion 30b toward the
main tube part 20 (not including a root R portion of
the main tube part 20).
[0035] Next, the projecting heights of the
projecting portions 30a, 30b will be described. Fig.
2 is a cross-sectional view taken along line I-I of
- 16 -
Fig. 1. The projecting height of a projecting
portion is the length of a line coupling a farthest
point from the main axis among points on the end face
of the projecting portion and the farthest point from
the main axis among points on the intersecting plane
between the, projecting portion and the main tube part.
The projecting height of the projecting portion 30a
is a projecting height La illustrated in Fig. 2. A
point 32a is the farthest point from the main axis 40
among points on the end face 33a of the projecting
portion 30a. A point 34a is the farthest point from
the main axis 40 among points on the intersecting
plane 35a between the projecting portion 30a and the
main tube part 20. That is, the projecting height La
is the length of the shortest distance 31a between
the point 32a and the point 34a. Further, the
projecting height of the projecting portion 30b is a
projecting height Lb illustrated in Fig. 2. A point
32b is the farthest point from the main axis 40 among
points, on the end face 33b of the projecting portion
30b. A point 34b is the farthest point from the main
axis 40 among points on the intersecting plane 35b
between the projecting portion 30b and the main tube
part 20. That is, the projecting height Lb is the
length of the shortest distance 31b between the point
32b and the point 34b.
[0036] The projecting heights La, Lb need to be 0.3D
or higher. Here, D represents an outside diameter of
the element tube before hydroforming. This is
- 17 -
because when the projecting heights La, Lb are lower
than 0.3D, it is not possible to couple an opponent
part to the projecting portions 30a, 30b by welding
or the like, and the joint does not function as a
joint member as originally intended. Further, the
projecting heights La, Lb are preferred to be 0.8D or
lower. When the projecting heights La, Lb are higher
than 0.8D, the plastic deformation amount of the
element tube becomes large, and a crack may occur in
roots of the projecting portions 30a, 30b. Note that
this range of the projecting heights La, Lb is
obtained by experiment.
[0037] The projecting heights La, Lb satisfy the
above-described lower and upper limits when partial
regions in respective predetermined ranges of the
projecting portion 30a and the projecting portion 30b
of the chassis joint 10 share a plane perpendicular
to the main axis 40 of the main tube part 20. Here,
the partial regions in the predetermined ranges are
regions indicated by K in Fig. 1.
[0038] In Fig. 1, the regions indicated by K need to
be in a specific numeric range defining the
intersecting planes 35a, 35b which will be described
later. As illustrated in Fig. 1, the projecting
portion 30a intersects the main tube part 20 via the
intersecting plane 35a. Further, the projecting
portion 30b intersects the main tube part 20 via the
intersecting plane 35b. As already described, the
intersecting plane 35a is a projecting plane of the
- 18 -
end face 33a toward the main tube part 20. In this
case, the root R portion of the main tube part 20 is
not included. Similarly, the intersecting plane 35b
is a projecting plane of the end face 33b toward the
main tube part 20. In this case, the root R portion
of the main tube part 20 is not included.
[0039] The projecting heights La, Lb of the
projecting portions 30a, 30b satisfy 0.3D or higher
and 0.8D or lower when a portion 36a of the
intersecting plane 35a and a portion 36b of the
intersecting plane 35b of the chassis joint 10 share
a plane perpendicular to the main axis 40, the area
of the portion 36a of the intersecting plane 35a is
in the range of 30% or more and 90% or less relative
to the area of the intersecting plane 35a, and the
area of the portion 36b of the intersecting plane 35b
is in the range of 30% or more and 90% or less
relative to the area of the intersecting plane 35b.
[0040] This point will be described taking examples
of a cross section taken along I-I, a cross section
taken along II-II, and a cross section taken along
III-III of Fig. 1. The portion 36a of the
intersecting plane 35a and the portion 36b of the
intersecting plane 35b share the cross section taken
along line I-I of Fig. 1. That is, both the
intersecting plane 35a and the intersecting plane 35b
exist in Fig. 2 illustrating the cross section taken
along line I-I of Fig. 1.
[0041] On the other hand, the cross section taken
- 19 -
along line II-II of Fig. 1 includes the intersecting
plane 35a but does not include the intersecting plane
35b. That is, in Fig. 3 illustrating the cross
section taken along line II-II of Fig. 1, only the
intersecting plane 35a exists and the intersecting
plane 35b does not exist.
[0042] Further, the cross section taken along line
III-III of Fig. 1 includes the intersecting plane 35b
but does not include the intersecting plane 35a.
That is, in Fig. 4 illustrating the cross section
taken along line III-III of Fig. 1, only the
intersecting plane 35b exists and the intersecting
plane 35a does not exist.
[0043] In short, in Fig. 1, the projecting portion
30a and the projecting portion 30b share a plane
perpendicular to the main axis 40 only in the region
indicated by K. Specifically, the cross section
taken along line I-I is within the region indicated
by K, and the cross section taken along line II-II
and the cross section taken along line III-III are
outside the region indicated by K. Then, the region
indicated by K can be represented by the ratio of
areas of the intersecting planes 35a, 35b.
[0044] Specifically, the projecting heights La, Lb
of the chassis joint 10 satisfy 0.3D or higher and
0.8D or lower when both the intersecting planes 35a,
35b of the two projecting portions 30a, 30b share a
plane (for example, the cross section taken along
line I-I) perpendicular to the main axis 40 of the
- 20 -
main tube part 20 only in the portion 36a of the
intersecting plane 35a and the portion 36b of the
intersecting plane 35b, the area of the portion 36a
of the intersecting plane 35a is in the range of 30%
or more and 90% or less of the area of the
intersecting plane 35a, and the area of the portion
36b of the intersecting plane 35b is in the range of
30% or more and 90% or less, of the area of the
intersecting plane 35b.
[0045] In this point, in the following three cases
for example, the projecting heights La, Lb of the two
projecting portions 30a, 30b do not satisfy 0.3D or
higher and 0.8D or lower. Note that in the following
examples, for convenience, ones corresponding to the
components of this embodiment are designated by the
same numerals and described.
[0046] The first is the case where both the
intersecting plane 35a and the intersecting plane 35b
do not share a plane perpendicular to the main axis
40 via the entire intersecting planes 35a, 35b. Fig.
5 is a perspective view illustrating an example of a
hydroformed body of the first case. In Fig. 5,
numeral 11 denotes the hydroformed body. In the
hydroformed body 11 illustrated in Fig. 5, the
projecting portions 30a, 30b are separated in a
longitudinal direction (main axis 40 direction) of
the hydroformed body 11. Thus, when the element tube
is hydroformed, a plastically deformed material is
supplied sufficiently to each of the projecting
- 21 -
portions 30a, 30b, and the projecting heights La, Lb
of the projecting portions 30a, 30b both exceeds 0.8D.
[0047] The second is the case where both the
intersecting plane 35a and the intersecting plane 35b
share a plane perpendicular to the main axis 40 via
the entire intersecting planes 35a, 35b. Fig. 6 is a
perspective view illustrating an example of a
hydroformed body of the second case. In Fig. 6,
numeral 12 denotes the hydroformed body. On the
hydroformed body 12 illustrated in Fig. 6, the
positions of the projecting portions 30a, 30b in a
longitudinal direction (main axis 40 direction) of
the hydroformed body 12 are the same, and the shapes
of the projecting portions 30a, 30b are the same.
Therefore, when the element tube is hydroformed, a
large amount of plastically deformed material has to
be supplied to each of the projecting portions 30a,
30b, and the projecting heights La, Lb of the
projecting portions 30a, 30b both do not satisfy 0.3D.
[0048] The third is the case where a portion of one
of the intersecting plane 35a and the intersecting
plane 35b and the whole of the other intersecting
plane share a plane perpendicular to the main axis 40.
Fig. 7 is a perspective view illustrating an example
of a hydroformed body of the third case. In Fig. 7,
numeral 13 denotes the hydroformed body. In the
hydroformed body 13 illustrated in Fig. 7, a portion
36a of the intersecting plane 35a of the projecting
portion 30a and the whole of the intersecting plane
- 22 -
35b of the projecting portion 30b share a plane
perpendicular to the main axis 40. That is, in the
hydroformed body 13 illustrated in Fig. 7, the
projecting portion 30b is disposed within a. range
where the projecting portion 30a is disposed with
respect to a longitudinal direction (main axis 40
direction) of the hydroformed body 13. In such an
arrangement, when the element tube is hydroformed, it
is easy for the plastically deformed material to be
supplied to a projecting portion with a large volume,
and hence the plastically deformed material is
supplied. by priority to the projecting portion 30a
with a larger volume, and the projecting height La of
the projecting portion 30a exceeds 0.8D. On the
other hand, it is difficult for the plastically
deformed material to be supplied to the projecting
portion 30b with a small area, and the projecting
height of the projecting portion 30b does not reach
0.3D. Formation satisfying both La > 0.8D and Lb <
0.3D hardly occurs, and when the projecting height Lb
of the projecting portion 30b is set to 0.3D or
higher and 0.8D or lower, the projecting height La of
the projecting portion 30a exceeds 0.8D. When the
projecting height La of the projecting portion 30a is
set to 0.3D or higher and 0.8D or lower, the
projecting height Lb of the projecting portion 30b
does not reach 0.8D.
[0049] As has been described, when the element tube
is hydroformed, if the intersecting plane 35a of the
- 23 -
projecting portion 30a and the intersecting plane 35b
of the projecting portion 30b share a plane
perpendicular to the main axis 40, the plastically
deformed material is supplied toward the end faces
33a, 33b of the projecting portions 30a, 30b from
both the intersecting plane 35a and the intersecting
plane 35b on this shared plane. Therefore, to set
the projecting heights La, Lb of the projecting
portions 30a, 30b to certain values or higher, a
sufficient supply amount of the plastically deformed
material is needed.
[0050] The projecting heights La, Lb of the
structural hydroformed joint member 10 satisfy 0.3D
or higher and 0.8D or lower when both the
intersecting plane 35a and the intersecting plane 35b
share a plane perpendicular to the main axis 40 of
the main tube part 20 only in the portion 36a of the
intersecting plane 35a and the portion 36b of the
intersecting plane 35b, the area of the portion 36a
of the intersecting plane 35a is in the range of 30%
or more and 90% or less of the area of the
intersecting plane 35a, and the area of the portion
36b of the intersecting plane 35b is in the range of
30% or more and 90% or less of the area of the
intersecting plane 35b.
[0051] That is, in Fig. 1, in the region illustrated
by K, since the intersecting plane 35a and the
intersecting plane 35b share a plane perpendicular to
the main axis 40 of the main tube part 20, supply of
- 24 -
the plastically deformed material is insufficient.
However, other than the region indicated by K, since
the intersecting plane 35a and the intersecting plane
35b do not share a plane perpendicular to the main
axis 40 of the main tube part 20, supply of the
plastically deformed material is sufficient, and the
insufficient amount of material supply in the region
indicated by K can be compensated. As a result, the
projecting heights La, Lb of the projecting portions
30a, 30b can be set to 0.3D or higher and 0.8D or
lower.
[0052] By variation of the region indicated by K,
the area of the portion in the intersecting plane 35a
in which the intersecting plane 35a and the
intersecting plane 35b share the plane perpendicular
to the main axis 40, that is, the area of the portion
36a of the intersecting plane 35a varies. Regarding
the area of the portion 36a of the intersecting plane
35a, it is necessary that the lower limit is 30% and
the upper limit is 90% relative to the area of the
intersecting plane 35a. When the area of the portion
36a of the intersecting plane 35a is less than 30%
relative to the area of the intersecting plane 35a,
the projecting height La exceeds 0.8D. Further, when
the area of the portion 36a of the intersecting plane
35a is less than 30% relative to the area of the
intersecting plane 35a, sufficient improvement in
rigidity of a coupling portion by using the chassis
joint 10 cannot be expected. On the other hand, when
- 25 -
the area of the portion 36a of the intersecting plane
35a is more than 90% relative to the area of the
intersecting plane 35a, material supply in the region
indicated by K becomes insufficient. Thus, the
projecting height La of the projecting portion 30a
becomes low, and the projecting height La does not
reach 0.3D.
[0053] The area of the portion 36b of the
intersecting plane 35b is similar to the case of the
portion 36a of the intersecting plane 35a.
[0054] By applying the present invention as
described above, the plural projecting portions 30a,
30b branching from a portion of the hydroformed body
being an origin can be provided on the hydroformed
body. These plural projecting portions 30a, 30b have
projecting heights necessary for coupling an opponent
part by welding or the like to the hydroformed body,
and thus the hydroformed body can be used as a
structural hydroformed joint member, and can be made
as a structure branching from a portion of the
structural hydroformed joint member being an origin.
[0055] Further, since the structural hydroformed
joint member has a hollow structure, the structural
hydroformed joint member can be reduced in weight
while achieving both strength and rigidity, and can
consequently allow the entire structure formed by
using the structural hydroformed joint member to be
reduced in weight while achieving both strength and
rigidity, thereby exhibiting significant industrial
- 26 -
effects.
[0056] In this embodiment, the two projecting
portions 30a, 30b are disposed diagonally around the
main axis 40 of the main tube part 20, but the angle
thereof is not limited to be orthogonal. When the
two projecting portions 30a, 30b are disposed to be
shifted by 180 degrees around the main axis 40,
hydroforming is relatively easy. However, by
applying the present invention, hydroforming to have
the projecting heights La, Lb satisfying 0.3D or
higher and 0.8D or lower is possible even when the
two projecting portions 30a, 30b are disposed closely
around the main axis 40, that is, disposed at an
angle shifted by 30 degrees or more and less than 180
degrees around the main axis 40.
[0057] Note that when the present invention is
applied to a structural member for automobile, high
mechanical strength and rigidity as a joint member is
needed, and thus the two projecting portions 30a, 30b
are desired to be disposed at an angle shifted by 45
degrees or more and less than 135 degrees around the
main axis 40. When placing importance on sufficient
mechanical strength as a structural member for
automobile, the above-described projections are
needed to be a certain size or larger. Thus, in
order for the projecting heights La, Lb to satisfy
0.3D or higher and 0.8D or lower, the lower limit
value of the aforementioned angle is 45 degrees due
to the limitation of hydroforming. On the other hand,
- 27 -
when placing importance on rigidity to be given to
the entire automobile structure as a structural
member for automobile, the upper limit of the
aforementioned angle is 135 degrees.
[0058] Moreover, when higher mechanical strength and
rigidity are needed as a structural member for
automobile, the aforementioned angle is desired to be
60 degrees or more and 120 ,degrees or less. When
much higher mechanical strength and rigidity are
needed not only in the structural member for
automobile, the aforementioned angle is desired to be
80 degrees or more and 100 degrees or less.
[0059] -Second Embodiment-
In the first embodiment, the case where there are
two projecting portions is described, but the case
where there are three or more projecting portions can
be described similarly. Fig. 8 is a perspective view
illustrating a three-branch automobile chassis joint
which is a structural hydroformed joint member
according to a second embodiment applying the present
invention. In Fig. 8, numeral 14 illustrates the
three-branch automobile chassis joint (hereinafter
referred to as a "three-branch chassis joint").
Differences from the first embodiment are mainly
described below. Similar components are designated
by same numerals, and detailed descriptions thereof
are omitted.
[0060] As illustrated in Fig. 8, the three-branch
chassis joint 14 is obtained by adding another
- 28 -
projecting portion 30c to projecting portions 30a,
30b similar to those described in the first
embodiment. The three-branch chassis joint 14 has an
intersecting plane 35a of a projecting portion 30a,
an intersecting plane 35b of a projecting portion 30b,
and an intersecting plane 35c of a projecting portion
30c. In this case, it is necessary to share a plane
perpendicularto a main axis 40 of a main tube part
20 only in a portion 36a of the intersecting plane
35a, a portion 36b of the intersecting plane 35b, and
a portion 36c of the intersecting plane 35c.
[0061] When there are three or more projecting
portions in this manner, all the intersecting planes
share a plane perpendicular to the main axis 40 of
the main tube part 20 only in their respective
portions. For example, in the case of the threebranch
chassis joint 14, all the intersecting planes
35a, 35b, 35c share the plane perpendicular to the
main axis 40 only in their respective portions.
Therefore, for example, when the intersecting plane
35a and the intersecting plane 35b share a plane
perpendicular to the main axis 40 only in their
respective portions and the intersecting plane 35b
and the intersecting plane 35c share a plane
perpendicular to the main axis 40 only in their
respective portions, but the intersecting plane 35a
and the intersecting plane 35c do not share a plane
perpendicular to the main axis 40 only in their
respective portions, not all the intersecting planes
- 29 -
35a, 351b, 35c share the plane perpendicular to the
main axis 40 only in their respective portions.
[0062] Further, regarding the area of the portion
36c of the intersecting plane 35c, the lower limit
needs to be 30% and the upper limit be 90% relative
to the area of the intersecting plane 35c, similarly
to the case of the intersecting planes 35a, 35b.
[0063] Regarding each of projecting heights La, Lb,
Lc, it is necessary that the lower limit is 0.3D and
the upper limit is 0.8D. It was found from
experiment that when the number of projecting
portions is increased, the size of one projecting
portion decreases, and thus the projecting height
does not depend on the number of projecting portions.
Note that the projecting height Lc of the projecting
portion 30c is defined similarly to the case of La,
Lb described in the first embodiment.
[0064] -Third Embodiment-
Although in the first embodiment the projecting
portions 30a, 30b are formed to project in an
orthogonal direction to the main axis 40 of the main
tube part 20, the projecting portions may also be
formed to project obliquely relative to the main axis
40. Fig. 9A is a perspective view illustrating an
automobile door surrounding joint which is a
structural hydroformed joint member according to a
third embodiment applying the present' invention.
Further, Fig. 9B is a cross-sectional view taken
along line IV-IV of Fig. 9A. In Fi.g. 9A, numeral 15
- 30 -
denotes the automobile door surrounding joint.
Differences from the first embodiment are mainly
described below. Similar components are designated
by same numerals, and detailed descriptions thereof
are omitted.
[0065] In the automobile door surrounding joint 15,
both an intersecting plane 35a of a projecting
portion 30a and an intersecting plane 35b of a
projecting portion 30b share a plane perpendicular to
the main axis 40 only in portions in the region
indicated by K. Then, the area of a portion 36a of
the intersecting plane 35a is in the range of 30% or
more and 90% or less of the intersecting plane 35a
and the area of a portion 36b of the intersecting
plane 35b is in the range of 30% or more and 90% or
less of the intersecting plane 35b, and projecting
heights La, Lb are 0.3D or higher and 0.8D or lower.
That is, when the plane perpendicular to the main
axis 40 of a main tube part 20 is shared only in the
portion 36a of the intersecting plane 35a of the
projecting portion 30a and only in the portion 36b of
the intersecting plane 35b of the projecting portion
30b, the projecting heights La, Lb are 0.3D or higher
and 0.8D or lower.
[0066] The automobile door surrounding joint 15
illustrated in Fig. 9A and Fig. 9B is formed so that
the projecting portion 30a projects in an orthogonal
direction to the main axis 40 of the main tube part
20, and the projecting portion 30b projects obliquely
- 31 -
at 12 degrees relative to the orthogonal direction of
the main axis 40 of the main tube part 20. The
intersecting plane 35b of the projecting portion 30b
which projects obliquely relative to the main axis 40
is a projected plane of an end face 33b projected
toward the main tube part 20 along its projecting
direction (straight direction oblique at 12 degrees
relative to the orthogonal direction of the main axis
40). Note that the angle of the projecting portion
30b is not limited to this. Further, the projecting
portion 30a may also be disposed to project in an.
oblique direction with respect to the main axis 40 of
the main tube part 20.
[0067] -Fourth Embodiment-
In a fourth embodiment, a shape connecting
projecting portions will be described. Fig. 10 is a
perspective view illustrating an automobile chassis
joint which is a structural hydroformed joint member
according to the fourth embodiment. In Fig. 10,
numeral 16 denotes a chassis joint. Further, Fig. 14
is a view illustrating a curved joining face and
gradually varying portions provided on the chassis
joint 16 according to the fourth embodiment.
Differences from the first embodiment are mainly
described below. Similar components are designated
by same numerals, and detailed descriptions thereof
are omitted.
[0068] The automobile chassis joint 16 according to
the fourth embodiment connects a projecting portion
- 32 -
30a to a projecting portion 30b sequentially by a
smooth curved face, as illustrated in Fig. 10 and Fig.
14. This curved face will be referred to as a curved
joining face 50 below. Since the curved joining face
50 sequentially connects the projecting portion 30a
and the projecting portion 30b, improvement in
rigidity of the entire structure in which the chassis
joint 16 is one of components can be expected.
[0069] When the projecting portion 30a is connected
to the projecting portion 30b sequentially by a
smooth curved face, gradually varying portions 52a,
52b may be provided at positions apart from the
projecting portions 30a, 30b on the main tube part 20.
[0070] In the chassis joint 16 illustrated in Fig.
10, similarly to the chassis joint 10 according to
the first embodiment, the area of a portion 36a of an
intersecting plane 35a is in the range of 30% or more
and 90% or less of the area of the intersecting plane
35a and the area of a portion 36b of an intersecting
plane 35b is in the range of 30% or more and 90% or
less of the area of the intersecting plane 35b, and
both projecting heights La, Lb are 0.3D or higher and
0.8D or lower.
[0071] Further, on the cross section taken along
line V-V of Fig. 10, both the intersecting plane 35a
and the intersecting plane 35b exist as illustrated
in Fig. 11. On the other hand, on the cross section
taken along line VI-VI of Fig. 10, only the
intersecting plane 35a exists and the intersecting
- 33 -
plane 335b does not exist, as illustrated in Fig. 12.
Further, on the cross section taken along line VIIVII
of Fig. 10, only the intersecting plane 35b
exists and the intersecting plane 35a does not exist,
as illustrated in Fig. 13.
[0072] Next, the curved joining face 50 and the
gradually varying portions 52a, 52b will be described.
The projecting portion 30a and the projecting portion
30b are connected smoothly and sequentially by the
curved joining face 50, and the projecting portion
30a and the projecting portion 30b are joined. When
there are three or more projecting portions, adjacent
projecting portions around the main axis 40 are
connected to each other by the smooth curved face,
and the projecting portions are joined one to another.
[0073] The curved joining face 50 has the gradually
varying portions 52a, 52b on both ends in the main
axis 40 direction of the main tube part 20. Fig. 15A
to Fig. 15D are views illustrating a cross-sectional
shape variation of the main tube part 20 for
describing the shape of the gradually varying portion
52a of the chassis joint 16. Fig. 15A is a crosssectional
view taken along line VIII-VIII of Fig. 14.
Fig. 15B is a cross-sectional view taken along line
IX-IX of Fig. 14. Fig. 15C is a cross-sectional view
taken along line X-X of Fig. 14. Fig. 15D is a
cross-sectional view taken along line XI-XI of Fig.
14. In the cross section taken along the line VIIIVIII
close to one tube end 21a, the curved joining
- 34 -
face 50, does not exist. Then, the area of the
gradually varying portion 52a increases in the order
of the cross section taken along line IX-IX, the
cross section taken along line X-X, and the. cross
section taken along line XI-XI, and the area becomes
largest on the cross section taken along line XI-XI.
That is, the gradually varying portion 52a reaches
its end point at the position of the cross section
taken along line XI-XI. Thus, the curved joining
face 50 has the gradually varying portion 52a whose
area decreases toward the tube end 21a. A tube end
21b opposite to the main tube part 20 also has the
similar gradually varying portion 52b.
[0074] By joining the projecting portion 30a and the
projecting portion 30b by the curved joining face 50,
the entire rigidity of the chassis joint 16 can be
improved. Then, by further providing the gradually
varying portions 52a, 52b, the entire rigidity of the
chassis joint 16 can be increased further.
[0075] When the size of the gradually varying
portion 52b is represented by a length W in a
direction parallel to the main axis 40 of the main
tube part 20 as illustrated in Fig. 14, both rigidity
improvement and hydroformability of the chassis joint
16 can be achieved when W is 0.2D or longer and 2.OD
or shorter. When W is shorter than 0.2D, the shape
variation of the gradually varying portion 52b is
rapid, and thus the hydroformability decreases. On
the other hand, when W exceeds 2.OD, the rigidity
- 35 -
improvement effect decreases. D represents an
outside diameter of the element tube before
hydroforming. The same applies to the gradually
varying portion 52a.
[0076] -Fifth Embodiment-
A protruding circumferential rib may be provided
between adjacent projecting portions 30a, 30b around
a main axis 40 of a main tube part 20. Fig. 16 is a
perspective view illustrating an automobile chassis
joint which is a structural hydroformed joint member
according to a fifth embodiment. In Fig. 16, numeral
17 denotes the chassis joint.
[0077] In the chassis joint 17 according to the
fifth embodiment, a circumferential rib 53 protruding
inward of the main tube part 20 is formed on a curved
joining face 50 connecting the projecting portion 30a
and the projecting portion 30b.
[0078] Fig. 17A to Fig. 17C are views illustrating a
cross-sectional shape variation of the main tube part
20. Fig. 17A is a cross-sectional view taken along
line XII-XII of Fig. 16. Fig. 17B is a crosssectional
view taken along line XIII-XIII of Fig. 16.
Fig. 17C is a cross-sectional view taken along line
XIV-XIV of Fig. 16. As is clear from the cross
section taken along line XIV-XIV illustrated in Fig.
17C, the circumferential rib 53 protruding inward of
the main tube part 20 is formed on the curved joining
face 50. By providing a protruding rib like the
circumferential rib 53 on the curved joining face 50,
- 36 -
the rigidity of the entire chassis joint 17 can be
improved.
[0079] The depth of the circumferential rib 53 is
preferred to be in the range of 1.0t or more and 3.Ot
or less. Here, t represents the thickness of an
element tube before hydroforming. When the depth of
the circumferential rib 53 is less than 1.0t,
rigidity improvement effect, cannot be obtained. On
the other hand, when it exceeds 3.0t,
hydroformability decreases.
[0080] -Sixth Embodiment-
The circumferential rib may be projecting outward
of the main tube part 20. Fig. 18 is a perspective
view illustrating an automobile chassis joint which
is a structural hydroformed joint member according to
a sixth embodiment. In Fig. 18, numeral 18 denotes
the chassis joint.
[0081] In the chassis joint 18 according to the
sixth embodiment, a circumferential rib 54 protruding
outward of the main tube part 20 is formed on a
curved joining face 50 connecting a projecting
portion 30a and a projecting portion 30b.
[0082] Fig. 19A to Fig. 19C are views illustrating a
cross-sectional shape- variation of the main tube part
20. Fig. 19A is a cross-sectional view taken along
line XV-XV of Fig. 18. Fig. 19B is a cross-sectional
view taken along line XVI-XVI of Fig. 18. Fig. 19C
is a cross-sectional view taken along line XVII-XVII
of Fig. 18. As is clear from the cross section taken
- 37 -
along line XVII-XVII illustrated in Fig. 19C, the
circumferential rib 54 protruding outward of the main
tube part 20 is formed on the curved joining face 50.
By providing a protruding rib like the
circumferential rib 54 on the curved joining face 50,
the rigidity of the entire chassis joint 17 can be
improved. The depth of the circumferential rib 54 is
the same as the case of the, circumferential rib 53.
[0083] Here, as illustrated in Fig. 18, the
circumferential rib 54 projecting outward of the main
tube part 20 can be provided on the curved joining
face 50 inside the region indicated by K in Fig. 1 in
which the intersecting plane 35a of the projecting
portion 30a and the intersecting plane 35b of the
projecting portion 30b share a plane perpendicular to
the main axis 40. Alternatively, as illustrated in
Fig. 20A and Fig. 20B, the circumferential rib 54 may
be provided on the curved joining face 50 outside the
region indicated by K. Fig. 20A and Fig. 20B are
views illustrating examples of providing the
circumferential rib 54 on the curved joining face 50
outside the region where the intersecting plane 35a
of.the projecting portion 30a and the intersecting
plane 35b of the projecting portion 30b share a plane
perpendicular to the main axis 40. Fig. 20A
illustrates the case where the circumferential rib 54
is on the tube end 21b side, and Fig. 20B illustrates
the case where the circumferential rib 54 is on the
tube end 21a side. Note that the position of the
- 38 -
circumferential rib 54 projecting outward of the main
tube part 20 is described here, but the same applies
to the position of the circumferential rib 53
projecting inward of the main tube part 20 described
in the fifth embodiment.
[0084] -Seventh Embodiment-
Instead of the circumferential rib 54 projecting
outward of the main tube part 20, an oblique flat
face rib may be provided. Fig. 21 is a perspective
view illustrating an automobile chassis joint which
is a structural hydroformed joint member according to
a seventh embodiment. In Fig. 21, numeral 19 denotes
the chassis joint.
[0085] Fig. 22A to Fig. 22C are views illustrating a
cross-sectional shape variation of the main tube part
20. Fig. 22A is a cross-sectional view taken along
line XVIII-XVIII of Fig. 21. Fig. 22B is a crosssectional
view taken along line XIX-XIX of Fig. 21.
Fig. 22C is a cross-sectional view taken along line
XX-XX of Fig. 21. As is clear from the cross section
taken along line XX-XX illustrated in Fig. 22C, the
curved joining face 50 has an oblique flat face rib
55,which projects outward of the main tube part 20
and the projecting face thereof is an oblique flat
face. The oblique flat face rib 55 can obtain
effects similar to those of the circumferential ribs
53, 54 having a shape curved along the shape of the
curved joining face 50.
[0086] Eighth Embodiment-
- 39 -
As described in the fourth to seventh embodiments,
the connection of the projecting portions 30a, 30b is
not limited to sequential connection by a curved face,
but may be an oblique flat face. Fig. 23 is a
perspective view illustrating an automobile chassis
joint which is a structural hydroformed joint member
according to an eighth. embodiment. In Fig. 23,
numeral 24 denotes the chassis joint.
[0087] Fig. 24A and Fig. 24B are views illustrating
a cross-sectional shape variation of the main tube
part 20. Fig. 24A is a cross-sectional view taken
along line XXI-XXI of Fig. 23. Fig. 24B is a crosssectional
view taken along line XXII-XXII of Fig. 23.
As is clear from the cross section taken along line
XXII-XXII illustrated in Fig. 24B, a projecting
portion 30a and a projecting portion 30b are
connected sequentially by an oblique flat joining
face 58, and the projecting portion 30a and the
projecting portion 30b are joined. When there are
three or more projecting portions, adjacent
projecting portions around the main axis 40 are
connected to each other by the oblique flat joining
face, and the projecting portions are joined one to
another. By thus employing the oblique flat joining
face 58, the rigidity of the entire chassis joint 24
decreases slightly as compared to the curved joining
face 50, but hydroformability can be improved.
[0088] -Ninth Embodiment-
In a ninth embodiment, end welding parts of
- 40 -
projecting portions on a structural hydroformed joint
member applying the present invention will be
described. Fig. 25 is a perspective view
illustrating an automobile chassis joint which is the
structural hydroformed joint member according to the
ninth embodiment. In Fig. 25, numeral 25 denotes a
chassis joint. Further, Fig. 26 is a cross-sectional
view taken along line XXIII-XXIII of Fig. 25.
Differences from the first embodiment are mainly
described below. Similar components are designated
by same numerals, and detailed descriptions thereof
are omitted.
[0089] The chassis joint 25 is welded at welding end
parts 37a, 37b of projecting portions 30a, 30b to an
opponent part, thereby forming a desired structure.
As illustrated in Fig. 25, an annular welding seat
face protruding portion 60 is provided on the welding
end part 37b, the welding seat face protruding
portion 60 contacts by priority with the opponent
part due to its protruding shape. Accordingly,
welding at the welding seat face protruding portion
60 ensures welding of the chassis joint 25 and the
opponent part, and weldability improves. In
particular, when laser welding with a small heat
input part is used, it is effective to provide the
welding seat face protruding portion 60.
[0090] A protruding height Hw1 illustrated in Fig. 26
is preferred to be 0.3t1 or higher and 2t1 or lower.
Here, t1 represents the thickness of the chassis joint
- 41 -
25. When Hw1 is lower than 0.3t1r the above-described
weldability improvement effect cannot be obtained.
On the other hand, when Hwl exceeds 2t1r
hydroformability decreases. Further, a flat face
length Lwl is not particularly limited but is
preferred to be 5 mm or more and 10 mm or less. When
Lwl is less than 5 mm, the welding range deviates from
the welding seat face protruding portion 60, and
welding cannot be performed securely. On the other
hand, when Lwl exceeds 10 mm, hydroformability
decreases. Further, a protrusion shoulder radius Rw1
is preferred to be 3t1 or smaller for securing
hydroformability.
[0091] Fig. 27 illustrates a modification example of
the ninth embodiment. The. welding seat face
protruding portion 60 may have a dotted shape as
illustrated in Fig. 27. That is, the projecting
portion 30b is preferred to have the welding seat
face protruding portion 60 on at least a portion in a
circumferential direction in the welding end part 37b.
[0092] Fig. 28 illustrates a modification example of
the ninth embodiment. Instead of the welding seat
face protruding portion 60, a leaf spring welding
seat face portion which will be described below may
be employed. Fig. 28 is a perspective view of a
chassis joint 25 employing a leaf spring welding seat
face portion 61 instead of the welding seat face
protruding portion 60. Further, Fig. 29 is a crosssectional
view taken along line XXIV-XXIV of Fig. 28..
- 42 -
[0093] The leaf spring welding seat face portion 61
has a shape like a leaf spring by providing a cutout
62, as illustrated in Fig. 29. By employing such a
leaf spring welding seat face portion 61, when the
chassis joint 25 is welded to an opponent part, it is
possible to weld the leaf spring welding seat face
portion 61 in a state that it is slightly deformed
like a leaf spring, and the., contact between the
opponent part and the leaf spring welding seat face
portion 61 can be improved further. Thus, welding
can be performed more securely, and weldability can
be improved further.
[0094] A seat face height HW2 illustrated in Fig. 29
is preferred to be 0.3t1 or higher and 1.5t1 or lower.
Here, t1 represents the thickness of the chassis joint
25. When HW2 is lower than 0.3t1, the above-described
weldability improvement effect cannot be obtained.
On the other hand, when HW2 exceeds 1.5t2r it is
possible that a crack occurs in a root of the leaf
spring welding seat face portion 61 when the leaf
spring welding seat face portion 61 is formed by
hydroforming. A flat face length LW2 and a seat face
shoulder radius RW2 are similar to the flat face
length Lwl and the protrusion shoulder radius Rwl.
[0095] Note that the case where the welding seat
face protruding portion 60 and the leaf spring
welding seat face portion 61 are provided on the
welding end part 37b of the projecting portion 30b
has been described, but the same applies to the case
- 43 -
where they are provided on a welding end part 37a of
the projecting portion 30a.
[0096] -Tenth Embodiment-
In a tenth embodiment also, an end welding part
of a projecting portion on a structural hydroformed
joint member applying the present invention will be
described. In the tenth embodiment, an embodiment
will be described in which,, for welding to an
opponent part is performed at the projecting portion
of the structural hydroformed joint member, a part of
an end face of the projecting portion is opened to
form a welding margin. Fig. 30 is a perspective view
illustrating an automobile chassis joint which is the
structural hydroformed joint member according to the
tenth embodiment. In Fig. 30, numeral 26 indicates
the chassis joint. Differences from the first
embodiment are mainly described below. Similar
components are designated by same numerals, and
detailed descriptions thereof are omitted.
[0097]° In the chassis joint 26, at least a part of
the end face 33b of the projecting portion 30b is
opened to form a'welding margin 70a. The welding
margin 70a is overlapped with a welding part of an
opponent part and welded thereto. In this manner,
welding of the chassis joint 26 to the opponent part
is secured. The method for opening at least a part
of the end face 33b of the projecting portion 30b may
be an ordinary method. For example, it may be
shearing, end milling, or the like.
- 44 -
[0098] When plural members (parts) are welded to
form a structure, if rigidity of a particular member
(part) is too high, a breakage may occur easily from
anywhere other than the welded part of this
particular member (part) when this structure is used.
Further, like an impact absorbing member for
automobile, it may be desired to cause a breakage
intentionally from a particular part of the structure.
In these cases, rigidity of the projecting portion
30b can be controlled by opening at least a part of
the end face 33b of the projecting portion 30b and
changing the area of the opening.
[0099] Fig. 31 illustrates a modification example of
the tenth embodiment. The end face 33b of the
projecting portion 30b can be opened so that plural
welding margins 70a to 70d can be formed, as
illustrated in Fig. 31. Note that in Fig. 30 and Fig.
31, the case where the welding margin is provided on
the end face 33b of the projecting portion 30b is
described, but the same applies to the case where it
is provided on the end face 33a of the projecting
portion 30a.
EXAMPLE
[0100] Next, the present invention will be described
further with examples. The condition of the examples
are one condition example employed for confirming
implementability and effect of the present invention,
and the present invention is not limited to this
condition example. The present invention can employ
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various conditions without departing from the spirit
of the present invention and as long as the object of
the present invention is achieved.
[0101] In the chassis joint 10 as illustrated in Fig.
1 and the three-branch chassis joint 14 as
illustrated in Fig. 8, the region indicated by K in
Fig. 1 and Fig. 8 were varied, and an area ratio R
where a plane perpendicular, to the main axis 40 of
the main tube part 20 is shared in each intersecting
plane was varied. Then, how the projecting heights
La, Lb, Lc of the projecting portions 30a, 30b, 30c
would vary by this was examined.
[0102] Note that, describing about the intersecting
plane 35a, the area ratio R is the ratio of the area
of the intersecting plane 35a which shares the plane
perpendicular to the main axis 20 with another
intersecting plane, to the area of the intersecting
plane 35a. That is, in Fig. 1, it is the ratio of
the area of the portion 36a of the intersecting plane
35a to the area of the intersecting plane 35a. The
same applies to the intersecting planes 35b, 35c.
[0103] There were two diameters, 60.5 mm and 114.3
mm,. of the element tube used. Further, the thickness
of the element tube was 2.3 mm. The condition of
hydroforming was: axial extrusion of 180 mm and
internal pressure of 80 MPa when the element tube
with a tensile strength of 390 MPa class is formed;
axial extrusion of 200 mm and internal pressure of
100 MPa when the element tube with a tensile strength
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of 540 MPa class is formed; and axial extrusion of
210 mm and internal pressure of 120 MPa when the
element tube with a tensile strength of 780 MPa class
is formed.
[0104] Combinations and results of the respective
conditions are illustrated in Table 1.
[0105]
[Table 1]
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[0106] As is clear from Table 1, it was confirmed
that when both intersecting planes share a plane
perpendicular to the main axis 40 of the main tube
part 20 only in portions of the intersecting planes,
and the areas of the portions of the intersecting
planes are 30% or more and 90% or less relative to
the respective areas of the intersecting planes, that
is, the intersecting plane area ratio R is 30% or
more and 90% or less, all the projecting heights are
0.3D or higher by which the function as a joint can
be secured with respect to the outside diameter D of
the element tube (see formation result 0).
[0107] In this respect, it was confirmed that even
when a plane perpendicular to the main axis 40 of the
main tube part 20 is shared only in portions of the
intersecting planes, if the areas of the portions of
the intersecting planes are not 30% or more and 90%
or less relative to the respective areas of the
intersecting planes, that is, the intersecting plane
area ratio R is 30% or more and 90% or less, part or
all of the projecting heights do not satisfy 0.3D or
higher by which the function as a joint can be
secured (see formation result X).
[0108] Further, it was confirmed that effects
similar to those illustrated in Table 1 were obtained
when the chassis joints 10, 14 are provided with at
least one of curved joining. face 50, gradually
varying portions 52a, 52b, circumferential ribs 53,
54, oblique flat joining face 58, welding seat face
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protruding portion 60, leaf spring welding seat face
portion 61, and welding margins 70a to 70d.
[0109] It should be noted that the above embodiments
merely illustrate concrete examples of implementing
the present invention, and the technical scope of the
present invention is not to be construed in a
restrictive manner by these embodiments. That is,
the present invention may be implemented in various
forms without departing from the technical spirit or
main features thereof. For example, an example is
presented in the above-described embodiments that a
lateral cross section (cross section perpendicular to
the main axis 40) of the main tube part 20 has a
substantially rectangular shape with roundness.
However, the shape of the main tube part 20 is not
limited, and the lateral cross section of the main
tube part 20 may be circular or polygonal.
[0110] Further, by applying the structural member of
the present invention to a building joint member, the
number of steps of assembly can be reduced
significantly as compared to the case where a plate
member, rod member or the like is fastened with a
bolt and so on to construct a building.
[0111] Further, when the structural member of the
present invention is applied to a building joint
member, the structure having the same strength and
rigidity can be reduced in weight, and the load to
support the empty weight of the building decreases.
Thus, the structure of the entire building can be
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simplified, and quake resistance can be improved.
[0112] Moreover, the structural member of the
present invention exhibits the largest effect in a
steel material such as a high-tensile steel, but may
be applied to a light-weight alloy material such as
aluminum alloy.
INDUSTRIAL APPLICABILITY
[0113] In the present invention, plural branching
projecting portions can be provided on a main tube
part, and these projecting portions have a desired
projecting height. For example, when it is used as a
structural joint member having a necessary projecting
height for coupling an opponent part by welding or
the like, a structure branching from a portion in the
structural joint member being an origin can be
obtained. Therefore, the present invention has high
industrial utility value.
CLAIMS
[Claim 1] A structural member comprising:
a hollow main tube part; and
at least two projecting portions formed
integrally on an outer peripheral face of the main
tube part, wherein
the two projecting portions are disposed at an
angle of 30 degrees or more, and less than 180 degrees
around a main axis of the main tube part, and
both intersecting planes, which are projecting
planes of end faces of the two projecting portions
toward the main tube part, share a plane
perpendicular to the main axis of the main tube part
only in portions of the intersecting planes.
[Claim 2] The structural member according to claim 1,
wherein
the two projecting portions are disposed at an
angle of 60 degrees or more and 120 degrees or less
around the main axis of the main tube part.
[Claim 3] The structural member according to claim 1,
further comprising another projecting portion
integrally formed on an outer peripheral face of the
main tube part, wherein
all intersecting planes, which are projecting
planes of end faces of the two projecting portions
and the other projecting portion toward the main tube
part, share a plane perpendicular to the main axis of
the main tube part only in portions of the
intersecting planes.
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[Claim 4] The structural member according to claim 1,
wherein
the main tube part and the two projecting
portions are formed by hydroforming an element tube.
[Claim 5] The structural member according to claim 4,
wherein
an outside diameter of the element tube is D, and
areas of the portions of the intersecting planes
are 30% or more and 90% or less relative to an area
of each of the intersecting planes and a projecting
height of each of the two projecting portions is 0.3D
or higher.
[Claim 6] The structural member according to claim 5,
wherein
the projecting height of each of the two
projecting portions is 0.8D or lower.
[Claim 7] The structural member according to claim 4,
wherein
a tensile strength of the element tube is 340 MPa
or more and 850 MPa or less.
[Claim 8] The structural member according to claim 1,
wherein
the main tube part is provided with a curved
joining face or an oblique flat joining face which
sequentially joins the two projecting portions.
[Claim 9] The structural member according to claim 8,
wherein
the curved joining face or the oblique flat
joining face has a gradually varying portion which
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becomes smaller in area toward a tube end of the main
tube part.
[Claim 10] The structural member according to claim
9, wherein
the length of the gradually varying portion is
0.2,D or longer and 2.OD or shorter in a direction
parallel to the main axis of the main tube part.
[Claim 11] The structural member according to claim
8, wherein
the curved joining face or the oblique flat
joining face is provided with a circumferential rib
which projects inward of the main tube part.
[Claim 12] The structural member according to claim
8, wherein
the curved joining face or the oblique flat
joining face is provided with a circumferential rib
which projects outward of the main tube part.
[Claim 13] The structural member according to claim
1, wherein
at least one of the two projecting portions has a
welding seat face protruding portion on at least a
portion in a circumferential direction.
[Claim 14] The structural member according to claim
1, wherein
at least one of the two projecting portions has
at least one leaf spring welding seat face portion in
a circumferential direction.
[Claim 15] The structural member according to claim
1, wherein
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at least one of the two projecting portions has a
welding margin formed by opening at least a portion
of an end face of the projecting portions.