U.S. patent application number 11/011064 was filed with the patent office on 2005-08-18 for friction spot joint structure.
This patent application is currently assigned to Mazda Motor Corporation. Invention is credited to Gendou, Toshiyuki, Iwashita, Tomoyuki, Kato, Kikuo, Takase, Kenji.
Application Number | 20050178817 11/011064 |
Document ID | / |
Family ID | 34697937 |
Filed Date | 2005-08-18 |
United States Patent
Application |
20050178817 |
Kind Code |
A1 |
Takase, Kenji ; et
al. |
August 18, 2005 |
Friction spot joint structure
Abstract
In a friction spot joint structure, a first plate member is
pressed against a second plate member by using a rotary tool and a
receiving member. A concave portion is formed by a rotating pin
portion of the rotating tool, with an interface between the first
plate member and the second plate member remained. In this time,
the first and second plate members are allowed to plastic-flow, so
that an annular bulging portion of the second plate member raised
into the first plate member is formed around the concave
portion.
Inventors: |
Takase, Kenji; (Hiroshima,
JP) ; Iwashita, Tomoyuki; (Hiroshima, JP) ;
Kato, Kikuo; (Hiroshima, JP) ; Gendou, Toshiyuki;
(Hiroshima, JP) |
Correspondence
Address: |
NIXON PEABODY, LLP
401 9TH STREET, NW
SUITE 900
WASHINGTON
DC
20004-2128
US
|
Assignee: |
Mazda Motor Corporation
Aki-gun
JP
|
Family ID: |
34697937 |
Appl. No.: |
11/011064 |
Filed: |
December 15, 2004 |
Current U.S.
Class: |
228/112.1 |
Current CPC
Class: |
B23K 20/1265
20130101 |
Class at
Publication: |
228/112.1 |
International
Class: |
B23K 020/12 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 16, 2004 |
JP |
2004-037708 |
Claims
What is claimed is:
1. A friction spot joint structure in which a fist plate member and
a second plate member are point joined with each other by plastic
flow in a manner that using a rotary tool having: a pin portion at
a tip end thereof and a shoulder portion having a larger diameter
than that of the pin portion at a base end of the pin portion; and
a receiving member arranged so as to face the rotary tool in an
axial direction of a rotary axis, the first plate member and the
second plate member overlapped with each other is interposed
between the rotary tool and the receiving member, the pin portion
is pressed into the first plate member while rotating the rotary
tool, and the shoulder portion is pressed against the first plate
member in the axial direction, comprising: a concave portion formed
by the pin portion and including a continuous interface between the
first plate member and the second plate member; and an annular
bulging portion of the second plate member which protrudes by
plastic flow into the first plate member around an entire outer
periphery of the concave portion.
2. The friction spot joint structure of claim 1, wherein a
protruding portion is formed so as to protrude outward from the
annular bulging portion.
3. The friction spot joint structure of claim 1, wherein the first
plate member and the second plate member are made of a light
metal.
4. The friction spot joint structure of claim 2, wherein the first
plate member and the second plate member are made of a light metal.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This Non-provisional application claims priority under 35
U.S.C. .sctn. 119(a) on Patent Application No. 2004-037708 filed in
Japan on Feb. 16, 2004, the entire contents of which are hereby
incorporated by reference.
BACKGROUND ART
[0002] 1. Field of the Invention
[0003] The present invention relates to a friction spot joint
structure in which a plurality of plate members are overlapped and
joined by plastic-flowing the plate members.
[0004] 2. Description of the Prior Art
[0005] It has been known conventionally that light metals,
particularly aluminum and the like are unsuitable for fused joint
such as arc welding, compared with steels, because they are more
conductive and transfer more heat than steels.
[0006] Taking the above into consideration, friction spot joint
structure has been known in which plate members are point joined by
fusing a part thereof by friction, for example, as disclosed in
Japanese Patent Application Laid Open Publication No. 2002-292479A.
In detail, in a friction spot joint apparatus including: a rotary
tool having a pin portion at its tip end and a shoulder portion of
a diameter larger than that of the pin portion at the base end of
the pin portion; and a receiving member arranged so as to face the
rotary tool in the axial direction of the rotation axis, first and
second plate members overlapped with each other are interposed
between the rotary tool and the receiving member, the pin portion
is pressed into the first plate member and the second plate member,
while rotating the rotary tool, and the shoulder portion is pressed
against the first plate member in the axial direction by, whereby
the plate members are point joined.
[0007] In the conventional friction spot joint structure, the
pressure and number of rotation of the rotary tool and the joining
period must be adjusted precisely. However, the adjustment is
difficult because the relationship between the joint quality and
such joining conditions is unclear. Hence, variation of the joint
quality becomes large. Further, the point joint is performed by
fusing plate materials by friction, which requires a considerable
time period.
SUMMARY OF THE INVENTION
[0008] The present invention has been made in view of the above
problems and has its object of obtaining a joint structure of
constant joint quality at high joint strength by devising a joint
structure of two plate members.
[0009] To attain the above object, the plate members are joined by
mechanical joint in the present invention.
[0010] Specifically, the first invention is directed to a friction
spot joint structure in which a fist plate member and a second
plate member are point joined with each other by plastic flow in a
manner that using a rotary tool having: a pin portion at a tip end
thereof and a shoulder portion having a larger diameter than that
of the pin portion at a base end of the pin portion; and a
receiving member arranged so as to face the rotary tool in an axial
direction of a rotary axis, the first plate member and the second
plate member overlapped with each other is interposed between the
rotary tool and the receiving member, the pin portion is pressed
into the first plate member while rotating the rotary tool, and the
shoulder portion is pressed against the first plate member in the
axial direction.
[0011] The friction spot joint structure includes: a concave
portion formed by the pin portion and including a continuous
interface between the first plate member and the second plate
member; and an annular bulging portion of the second plate member
which protrudes by plastic flow into the first plate around an
entire outer periphery of the concave portion.
[0012] With the above structure, the continuous interface between
the first plate member and the second plate member exists.
Therefore, the pressed second plate member plastic-flows into the
first plate member in a solid phase state when the first and the
second plate members interposed between the rotary tool and the
receiving member are softened by friction heat caused at the
rotating shoulder and pin portions. Thus, that the first plate
member and the second plate member are joined to each other
mechanically, forming the annular bulging portion around the
concave portion. The joint strength depends on the size of a
mechanically joined part of the bulging portion, which can be
easily adjusted by changing joining conditions such as the pressure
and number of rotation of the rotary tool, the joining period and
the like. Hence, a target joint strength can be obtained
constantly.
[0013] Further, the continuous interface remains between the first
plate member and the second plate member at the bottom of the
concave portion, and therefore, stress concentration is hard to be
invited compared with the case with a discontinuous interface.
Accordingly, cracking is prevented and the shear fracture strength
is increased. Furthermore, the second plate member is not exposed
to the wall face forming the concave portion. Therefore, in the
case using a material having an anti-corrosion characteristic as
the first plate member, even if the second plate member is inferior
in anti-corrosion characteristic, the anti-corrosion characteristic
at the joint part is ensured and easy quality management for
surface treatment, coating and the like can be attained because the
same material exists continuously in the surface portion.
[0014] In the second invention, a protruding portion is formed so
as to protrude outward from the annular bulging portion. By this
formation, the protruding portion of the second plate member
encroaches into the first plate member outward from the bulging
portion, whereby, the protruding portion exhibits an effect as an
anchor to increase the strength against a load in a direction of
force to separate the first plate member from the second plate
member.
[0015] In the third and fourth inventions, the first plate member
and the second plate member are made of a light metal. In light
metals having small specific gravities, such as aluminum,
magnesium, plastic flow in a solid phase state is easily caused at
comparatively low temperatures. Hence, with the light metal
employed, the effects of the present invention are remarkably
exhibited.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a side view showing a joint gun.
[0017] FIG. 2 is a section showing, in an enlarged scale, a
friction spot joint structure according to an embodiment of the
present invention.
[0018] FIG. 3 is a graph illustrating dependencies of a diameter of
a fractured part and tensile shear strength on a joining period in
the friction spot joint structure according to Embodiment 1.
[0019] FIG. 4 is a section showing a joint part obtained at joining
period of 0.4 sec.
[0020] FIG. 5 is a view corresponding to FIG. 4 and showing a joint
part obtained at joining period of 0.7 sec.
[0021] FIG. 6 is a section showing, in an enlarged scale, a bulging
portion in FIG. 5.
[0022] FIG. 7 is a section showing a joint part in a friction spot
joint structure according to Embodiment 2.
[0023] FIG. 8 is a section showing, in an enlarged scale, an
encircled part C in FIG. 7.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] Embodiments of the present invention will be described below
with reference to accompanying drawings. Wherein, the following
embodiments are preferred examples essentially and do not intend to
limit application, use and scope of the present invention.
Construction of Joint Gun
[0025] FIG. 1 shows a joint gun 1 installed in a friction point
joining apparatus (the whole construction is not shown) according
to the embodiments of the present invention. The joint gun 1, which
is fitted to, for example, a wrist of a robot, is provided for
point-joining a plurality of plate members made of a light metal
such as an aluminum alloy, a magnesium alloy, a zinc alloy used for
bodies and the like of automobiles in a state that they are
overlapped with each other in the thickness direction thereof, to
form a friction joint structure. The joint gun 1 includes a joint
tool 6 composed of a rotary tool 4 and a receiving member 5, and
the rotary tool 4 and the receiving member 5 interpose a part to be
joined of a work W, which is composed of a first plate member W1
and a second plate member W2 overlapped with each other in the
thickness direction thereof.
[0026] As schematically shown in FIG. 2, the rotary tool 4 includes
a pin portion 42 in a column shape at a tip end portion 41 thereof,
and a shoulder portion 43 of which diameter is larger than the
diameter of the pin portion 42 is formed at the tip end portion 41
on the base end side of the pin portion 42.
[0027] The rotary tool 4 is arranged along a rotation axis X (axial
line) intersecting at a right angle with an overlap plane S1
between the first and second plate members W1, W2 of the work W,
and is rotated around the rotation axis X by a rotary shaft motor
11. Further, the rotary tool 4 moves up and down along the rotation
axis X by a pressing shaft motor 12. The first and second plate
members W1, W2 may be made of the same material or different
materials and its combination is not limited only if each of them
is made of a light metal.
[0028] The receiving member 5 is formed of a main body 51 in column
shape having a top face 52 of which shape and area are
substantially the same as or larger than those of the tip end
portion 41 of the rotary tool 4. Further, the receiving member 5 is
mounted in the rotary axis X to the tip end of a substantially
L-shaped arm 13 so as to face the rotary tool 4, with the work W
interposed.
Work Joining Sequence
[0029] As shown in FIG. 2, the rotary tool 4 is rotated around the
rotation axis X by the rotary shaft motor 11 of the joint gun 1.
After the number of rotation of the rotary tool 4 reaches a
predetermined value, the rotary tool 4 is brought down by the
pressing shaft motor 12 so as to be in contact with the surface of
the work W (first plate member W1), while rotating the rotary tool
4. In so doing, the work W is interposed between the rotary tool 4
and the receiving member 5 and is pressed in the direction of the
rotation axis X (downward in FIG. 2). In this manner, the pin
portion 42 of the rotary tool 4 is pressed into the work W. On the
other hand, the receiving member 5 supports the work W at a top
face 52 thereof By this supporting, the pressure of the rotary tool
4 to the work W is received at the top face 52 of the receiving
member 5, thereby preventing the work W from deformation toward the
receiving member 5.
[0030] Next, the rotary tool 4 is further pressed toward the work
W, while rotating the rotary tool 4. In this association, the pin
portion 42 of the rotary tool 4 is squeezed into the first plate
member W1, to generate heat. Further, after the pin portion 42 is
buried in the first plate member W1, the shoulder portion 43 of the
rotary tool 4 and the surface of the first plate member W1 are
rubbed against each other to generate friction heat. The thus
generated friction heat is transferred from the first plate member
W1 to the second plate member W2, thereby softening the second
plate member W2.
[0031] The rotation and the pressing of the rotary tool 4 are
continued to generate plastic flow in the rotation direction in the
first and second plate members W1, W2. The further continuation of
the rotation and the pressing of the rotary tool 4 increases the
range of the plastic flow in the work W.
[0032] Furthermore, when the pin portion 42 and the shoulder
portion 43 are rotated and press the first plate member W1 toward
the second plate member W2, the pin portion 42 and shoulder portion
43 are buried into the work W and a concave portion 61 is formed by
the pin portion 42, with a continuous interface S2 between the
first plate member W1 and the second plate member W2 remained. In
this time, the first and second plate members W1, W2 plastic-flow
in a solid phase state and the second plate member W2 pressed
between the rotary tool 4 and the receiving member 5 flows outward
in radial direction of the concave portion 61 into a part of the
first plate member W1 where internal pressure is smaller than the
side wall face of the concave portion 61. In this association, an
annular bulging portion 63 is formed in the first plate member W1
so as to surround the concave portion 61 with the rotation axis X
as a center. Accompanied by the rotation of the shoulder portion
43, further plastic flow is caused outward in the radial direction
around the annular bulging portion 63, so that a protruding portion
64 protruding outward in the radial direction is formed around the
annular bulging portion 63. The protruding portion 64 of the second
plate member W2 encroaches in and is joined to the first plate
member W2.
[0033] After continuation of the plastic flow in the work W for a
given period of time in this way, the rotary tool 4 is raised by
the pressing shaft motor 12, while rotating the rotary tool 4, so
that the rotary tool 4 is pulled out from the work W.
[0034] Thereafter, the work W is cooled quickly to be hardened,
thereby completing the joining of the work W.
Effects of Embodiment
[0035] In the friction spot joint structure according to the above
embodiment, the concave portion 61 is formed by the pin portion 42,
with the continuous interface S2 between the first plate member W1
and the second plate member W2 remained by pressing the first plate
member W1 toward the second plate member W2 between the rotary tool
4 and the receiving member 5, and the annular bulging portion 63 of
the second plate member W2 is formed which protrudes into the first
plate member W1 by plastic flow of the first and second plate
members W1, W2. The joint strength depends on the size of a
mechanically joined part of the bulging portion 63, which can be
easily adjusted by changing joining conditions such as the pressure
and number of rotation of the rotary tool 4, ajoining period and
the like. Accordingly, a target joint strength can be obtained
constantly. Further, with the interface S2, the shear fracture
strength is increased and easy quality management for surface
treatment, coating and the like are attained.
[0036] Moreover, the protruding portion 64 formed around the
bulging portion 63 exhibits an effect as an anchor, thereby
increasing the strength against a load in a direction of force to
separate the joint part.
[0037] In addition, the first and second plate members W1, W2 are
made of a light metal, which easily causes plastic flow in a solid
phase state, thereby remarkably exhibiting the effects of the
present embodiment.
Modified Example of Embodiment
[0038] The receiving member 5 is fixed in the above embodiment but
may be movable in the rotation axis X. Further, the receiving
member 5 is formed of the column shaped main body 51 having the top
face 52 of which shape and area are substantially the same as or
larger than those of the tip end portion 41 of the rotary tool 4 in
the present invention, but the receiving member 5 may be in a plate
shape.
WORKING EXAMPLES
[0039] Working Examples that were performed practically will be
described next.
Working Example 1
[0040] Referring to the work W, a 6000 series aluminum alloy of 1
mm in thickness was used as the first plate member W1 and a 3000
series aluminum alloy of 1 mm in thickness was used as the second
plate member W2. The work W was joined using the aforementioned
friction point joining apparatus.
[0041] Specifically, the rotary tool 4 having the shoulder portion
43 of 8 mm in diameter was used, the pressure and number of
rotation thereof were set to 3.42 kN and 2500 rpm, respectively,
and a plurality of joint parts were formed in a single work W with
the joining period changed per 0.1 sec. Then, the work W was cut
into joint parts per joining period to observe each section thereof
Further, the tensile shear strength of each joint part per joining
period was measured.
[0042] FIG. 3 shows studied results of dependencies of diameters R
of fractured parts and tensile shear strength on the joining
period. FIG. 4 is a section showing the joint part obtained at the
joining period of 0.4 sec., and FIG. 5 is a section showing the
joint part obtained at the joining period of 0.7 sec. Each diameter
R of the fractured parts correspond substantially to the maximum
diameter of the bulging portion 63 and to an effective diameter of
a mechanically joined part in the overlap plane S1 between the
first plate member W1 and the second plate member W2. Specifically,
as shown in an enlarged scale in FIG. 6, the first plate member W1
and the second plate member W2 were mechanically joined to each
other in a range of the diameter R of the fractured part with no
space. On the other hand, though not appearing in the drawing, a
minute space between the first plate member W1 and the second plate
member W2 was observed at the outside of the range of the diameter
R.
[0043] As can be understood from comparison of FIG. 4 with FIG. 5,
by setting joining period longer, the bulging portion 63 grows and
the diameter R of the fractured part is increased. In other words,
it is found that, as shown in FIG. 3, the diameter R of the
fractured part is increased as the joining period is longer to some
extent, accompanying increase in tensile shear strength. When the
joining period is 0.7 sec., the protruding portion 64 is formed at
the bulging portion 63, as shown in an enlarged scale in FIG. 6,
and the tensile shear strength is further increased. It should be
noted that it is found that in the case where the joining period is
longer than a given period (0.8 sec. in the present working
example), the tensile shear strength is reduced contrarily because
the first plate member W1 at the interface S2 becomes too thin, and
so on.
[0044] A range B in FIG. 3 indicates a range of the joint period
where the fractured part is formed in a button shape (annular) in a
plan view in the tensile shear test, and the most excellent joint
strength was obtained in this range B. A range A indicates a range
of the joint period where the fractured part in a plan view is
discontinuous and does not form an annular shape in the tensile
shear test. In the range A, the joint strength was lower than in
the range B. Wherein, in the joining period of 0.4 sec., the
annular bulging portion 63 was formed as shown in FIG. 4, and the
tensile shear strength was increased.
[0045] As described above, the size of the mechanically joined
part, that is, the diameter R of the fractured part can be easily
adjusted by changing the joining conditions such as the pressure
and number of rotation of the rotary tool 4, the joining period and
the like, and therefore, it was found that a target joint strength
can be obtained constantly.
Working Example 2
[0046] Referring to the work W, a 6000 series aluminum alloy of 1
mm in thickness was used as the first plate member W1 and a 5000
series aluminum alloy of 2 mm in thickness was used as the second
plate member W2. The work W was joined using the aforementioned
friction point joining apparatus in which the pressure of the
rotary tool 4 was set to be 3.92 kN, the number of rotation thereof
was set to be 3500 rpm and the joining period was set to be 0.8
sec. The joint part obtained is shown in an enlarged scale in FIG.
7. It is understood that the bulging portion 63 was formed
excellently in the friction spot joint structure in Working Example
2. It was found, as shown in an enlarged scale in FIG. 8, that the
continuous interface S2 between the first plate member W1 and the
second plate member W2 was formed at the bottom (encircled part C
in FIG. 7) of the concave portion 61.
* * * * *