JOINT STRUCTURE AND JOINING METHOD THEREOF
Technical Fiel5 d
[0001]
The present disclosure relates to a joint structure and
a joining method thereof, and particularly, relates to a joint
structure formed by crimping joint of a shaft member and a
10 cylindrical member used for a torque sensor, and to a joining
method thereof.
Background Art
[0002]
15 Heretofore, a torque sensor described in Patent
Literature 1 has been mentioned as a technique concerning a
joint structure, which fits a cylindrical member to a shaft
member such as a solid shaft or a hollow shaft, and crimps
the cylindrical member to then fix the cylindrical member to
20 the shaft member.
As illustrated in FIG. 13, in the torque sensor of Patent
Literature 1, plural axial grooves 111 extending in an axial
direction and a circumferential groove 122 continuous in a
circumferential direction are formed on an outer
25 circumferential surface of a large-diameter portion 103A of
an end portion of an output shaft 103.
The axial grooves 111 are formed over both end portions
of the large-diameter portion 103A. The circumferential
- 3 -
groove 122 is formed near a position where an end portion of
a cylindrical member 110 is located when the cylindrical
member 110 is fixed.
[0003]
Plural hemispherical projections 113 are formed o5 n
positions slightly protruding from a lower end portion of an
inner circumferential surface of the cylindrical member 110.
The number and the forming position of the projections 113
correspond to those of axial grooves 111. The height of the
10 projections 113 is equal to the depth of the axial grooves
111.
In fixing the cylindrical member 110 to the
large-diameter portion 103A, the projections 113 are fitted
into the axial grooves 111 to position the cylindrical member
15 110 in the circumferential direction with respect to the
output shaft 103. Next, the cylindrical member 110 is pushed
such that the end portion of the cylindrical member 110 comes
close to the circumferential groove 122. In such a state,
the end portion of the cylindrical member 110 is crimped
20 inwardly so as to bite into the circumferential groove 122.
As described above, in the technique described in Patent
Literature 1, the projections provided on the cylindrical
member are fit into the grooves provided on the shaft member
to prevent displacement in a rotational direction.
25
Citation List
Patent Literature
[0004]
- 4 -
PTL 1: JP H11-248562 A
Summary of Invention
Technical Problem
[00055 ]
The torque sensor described in Patent Literature 1,
however, has room for improvement in following points (1) to
(4).
(1) In fitting the projections provided beforehand on
10 the cylindrical member to the axial grooves, a problem such
as a gap between the fitted portions or scraping of the
projections may occur depending on working accuracy of the
projections and the axial grooves. In a combination in which,
for example, a diameter of a circle inscribed to the
15 projections is lager than a diameter of the bottom of the
groove, looseness may occur in the rotational direction.
(2) When the projection is formed by deformation
processing, springback results in a shear drop at the foot
of the projection and the shear drop may interfere a groove
20 shoulder. When the cylindrical member is inserted into the
shaft member in such a state, the projection of the
cylindrical member is scraped, and thus contamination is
caused and may result in a problem.
[0006]
25 (3) In matching the tip of the projection of the
cylindrical member with the bottom of the groove and fitting
them to each other, when the projection comes into contact
with the groove at one point of the bottom of the groove,
- 5 -
rigidity in the rotational direction is low. Thus, such a
contact is not sufficient as a rotation stopper in a mode in
which an external force is applied to the cylindrical member
in the worst case.
(4) Since the inner diameter of the projections is fitte5 d
into the bottom of the groove, the diameter of the circle
inscribed to the projections may affect the assembly accuracy
of the cylindrical member. For example, when the coaxial
degree between the circle inscribed to the projections formed
10 by deformation processing and the cylindrical member is not
sufficient, the cylindrical member may be eccentric relative
to the shaft member.
In this connection, the present disclosure has been made
by focusing on the problem mentioned above, and it is an object
15 of the present disclosure to provide a joint structure capable
of suitably joining the members which compose the joint
structure, and to provide a joining method thereof.
Solution to Problem
20 [0007]
An embodiment of a joint structure for achieving the
above-described object includes: a shaft member; and a
cylindrical member, an inner surface of which is fitted to
an outer surface of the shaft member.
25 The cylindrical member including: a plurality of first
crimped portions which are crimped along a plurality of axial
grooves provided in an axial direction of the shaft member,
respectively; and
- 6 -
a second crimped portion which fits the axial grooves and
is crimped along a circumferential groove, the
circumferential groove being provided on a circumferential
surface of the shaft member by reducing a diameter of an
axially intermediate portion of the cylindrical member in 5 a
radial direction.
Herein, each of the first crimped portions of the joint
structure may have a shape projecting from the inner
circumferential surface of the cylindrical member as a
10 spherical projection.
[0008]
Furthermore, in the joint structure, a position of a tip
in the axis direction of the spherical projection may be laid
out within a predetermined range on a side surface side of
15 the circumferential groove.
Furthermore, in the joint structure, a diameter of a
circle inscribed to the first crimped portions may be set
lager in cross section than a curvature radius of a bottom
portion in a circumferential direction of each of the axial
20 grooves.
Furthermore, in the joint structure, the
circumferential groove may be have a bathtub-shaped
cross-section in the axial direction.
[0009]
25 Furthermore, an embodiment of a joining method of a joint
structure, includes:
a provisional first crimped portion forming step for
forming a plurality of projections on an inner
- 7 -
circumferential surface of a cylindrical member such that the
plurality of projections are engaged with a plurality of axial
grooves provided on a shaft member, respectively;
fitting the shaft member to the cylindrical member such
that an outer surface of the shaft member comes into contac5 t
with the inner surface of the cylindrical member, and such
that the projections on the inner circumferential surface of
the cylindrical member engage with the plurality of axial
grooves provided on the shaft member and a circumferential
10 groove provided on a circumferential surface of the shaft
member; and
a crimped portion forming step for forming first crimped
portions and a second crimped portion which is connected the
first crimped portions and crimped along the circumferential
15 groove at the same time by laying out a tip in an axis direction
of each of the plurality of the projections of respective
provisional first crimped portions within a predetermined
range on a side surface side of the circumferential groove,
and by reducing a diameter of the cylindrical member along
20 the circumferential groove provided on the circumferential
surface of the shaft member.
[0010]
Furthermore, another embodiment of a joining method of
a joint structure, includes:
25 a provisional first crimped portion forming step for
forming a plurality of projections on an inner
circumferential surface of a cylindrical member such that the
- 8 -
plurality of projections are engaged with a plurality of axial
grooves provided on a shaft member, respectively;
fitting the shaft member to the cylindrical member such
that an outer surface of the shaft member comes into contact
with the inner surface of the cylindrical member, and suc5 h
that the plurality of axial grooves provided on the shaft
member engage with the projections on the inner
circumferential surface of the cylindrical member; and
a first crimped portion forming step for forming first
10 crimped portions by deforming provisional first crimped
portions along the axial grooves of the shaft member; and
a second crimped portion forming step for forming a
second crimped portion which is connected the first crimped
portions and crimped along a circumferential groove provided
15 on a circumferential surface of the shaft member by reducing
a diameter of an axially intermediate portion of the
cylindrical member in a radial direction.
[0011]
Herein, in the joining methods of the joint structure,
20 each of the first crimped portions may have a shape projecting
from the inner circumferential surface of the cylindrical
member as a spherical projection.
Furthermore, in the joining methods of the joint
structure, a diameter of a circle inscribed to the first
25 crimped portions may be set lager in cross section than a
curvature radius of a bottom portion in a circumferential
direction of each of the axial grooves.
- 9 -
Furthermore, in the joining methods of the joint
structure, the circumferential groove may be have a
bathtub-shaped cross-section in the axial direction.
Advantageous Effects of Inventio5 n
[0012]
According to the present disclosure, it is possible to
provide a joint structure capable of suitably joining the
members which compose the joint structure, and to provide a
10 joining method thereof.
Brief Description of Drawings
[0013]
FIG. 1 is a perspective view illustrating a configuration
15 in a certain embodiment of a joint structure;
FIG. 2 is a partial cross-sectional view illustrating
the configuration in the certain embodiment of the joint
structure;
FIG. 3 is a partial cross-sectional view of a main portion,
20 illustrating the configuration in the certain embodiment of
the joint structure;
FIG. 4 is a partial cross-sectional view illustrating
a configuration of a cylindrical member in the certain
embodiment of the joint structure;
25 FIG. 5 is a partial cross-sectional view illustrating
a state before a first crimped portion forming step in the
certain embodiment of a joining method of the joint structure;
- 10 -
FIGs. 6A and 6B are partial cross-sectional views of the
main portion in the first crimped portion forming step in the
certain embodiment of the joining method of the joint
structure, in which FIG. 6A illustrates the state before the
first crimped portion forming step, and FIG. 6B illustrate5 s
the state after the first crimped portion forming step;
FIGs. 7A and 7B are perspective views illustrating states
in the second crimped portion forming step in the certain
embodiment of the joining method of the joint structure, in
10 which FIG. 7A illustrates the state before the second crimped
portion forming step, and FIG. 7B illustrates the state after
the second crimped portion forming step;
FIG. 8 is a partial cross-sectional view of the main
portion, illustrating a state after the second crimped
15 portion forming step in the certain embodiment of the joining
method of the joint structure;
FIG. 9 is a cross-sectional view illustrating a
configuration of a circumferential groove in another
embodiment of the joint structure and the joining method;
20 FIGs. 10A and 10B are perspective views illustrating
states in the second crimped portion forming step in the other
embodiment of the joint structure and the joining method, in
which FIG. 10A illustrates the state before the second crimped
portion forming step, and FIG. 10B illustrates the state after
25 the second crimped portion forming step;
FIGs. 11A to 11D are photographs of the cylindrical
member in the other embodiment of the joint structure and the
joining method, in which FIGs. 11A to 11C are photographs of
- 11 -
an outer diameter of the cylindrical member on which a
projection is formed, with the advance of crimping by reducing
the diameter, viewed from directly above, and FIG. 11D is a
photograph of the state of the projection on the inner
diameter side of the cylindrical member after the crimpin5 g
by reducing the diameter;
FIGs 12A to 12C are graphs illustrating a rotation
stopping effect of the projection in the other embodiment of
the joint structure and the joining method, a torque applied
10 to the joined portion of the shaft member and the cylindrical
member is illustrated on a vertical axis, and a relative angle
between the shaft member and the cylindrical member is shown
on a horizontal axis;
FIG. 13 is a perspective view illustrating a
15 configuration in a conventional joint structure;
FIG. 14 is a partial cross-sectional view of the main
portion illustrating the configuration in the conventional
joint structure; and
FIG. 15 is a partial cross-sectional view of the main
20 portion illustrating the configuration in the conventional
joint structure.
Description of Embodiments
[0014]
25 A description is made below of embodiments of a joint
structure according to the present disclosure and a joining
method thereof with reference to the drawings.
(Joint Structure)
- 12 -
FIG. 1 is a perspective view illustrating a configuration
in a certain embodiment of a joint structure according to the
present disclosure. Furthermore, FIG. 2 is a partial
cross-sectional view illustrating the configuration in the
certain embodiment of the joint structure according to th5 e
present disclosure. Furthermore, FIG. 3 is a partial
cross-sectional view of a main portion, illustrating the
configuration in the certain embodiment of the joint
structure according to the present disclosure. Furthermore,
10 FIG. 4 is a partial cross-sectional view illustrating a
configuration of a cylindrical member in the certain
embodiment of the joint structure according to the present
disclosure. It is to be noted that FIG. 4 is expressed by
omitting a shaft member from FIG. 1 and FIG. 2.
15 [0015]
As illustrated in FIG. 1 to FIG. 4, a joint structure
1 of the present embodiment includes a shaft member 10 and
a cylindrical member 20 having an inner circumferential
surface fitted to an outer circumferential surface of the
20 shaft member 10.
Plural axial grooves 11 are provided on a circumferential
surface of the shaft member 10 in an axial direction.
Furthermore, a circumferential groove 12 is provided over
whole periphery of the circumferential surface of the shaft
25 member 10.
The cylindrical member 20 includes plural first crimped
portions 21 crimped along the plural axial grooves 11,
respectively, and a second crimped portion 22 being fitted
- 13 -
to the axial grooves 11 and crimped along the circumferential
groove 12 of the shaft member 10 by reducing a diameter of
an axially intermediate portion in a radial direction. In
the present embodiment, the second crimped portion 22 is
provided over whole periphery of the circumferential surfac5 e
of the cylindrical member 20.
[0016]
That is, the first crimped portions 21 are provided on
intersections between the axial grooves 11 and the
10 circumferential groove 12, and the second crimped portion 22
is formed on the first crimped portions 21 by reducing the
diameter of the cylindrical member 20. Specifically, as
illustrated in FIG. 4, a projection projecting from the inner
circumferential surface of the cylindrical member 20 inwardly
15 (hereinafter, also simply referred to as projection) is
deformed by being crimped such that the side surface shape
of the axial groove 11 is transferred thereto.
Furthermore, as illustrated in FIG. 4, it is preferable
that the first crimped portion 21 have a shape projecting from
20 the inner circumferential surface of the cylindrical member
20 as a spherical projection.
Furthermore, it is preferable that a diameter of a circle
inscribed to the first crimped portions 21 be set larger than
the curvature radius of a bottom portion in a cross section
25 in a circumferential direction of the axial groove 11.
[0017]
(Joining Method of Joint Structure)
- 14 -
Next, a description is made of a joining method of the
joint structure shown in FIG. 1 to FIG. 4.
FIG. 5 is a partial cross-sectional view illustrating
a state before a first crimped portion forming step in the
certain embodiment of the joining method of the join5 t
structure. Furthermore, FIGs. 6A and 6B are partial
cross-sectional views of the main portion in the first crimped
portion forming step in the certain embodiment of the joining
method of the joint structure, in which FIG. 6A illustrates
10 the state before the first crimped portion forming step, and
FIG. 6B illustrates the state after the first crimped portion
forming step.
[0018]
Furthermore, FIGs. 7A and 7B are perspective views
15 illustrating states in the second crimped portion forming
step in the certain embodiment of the joining method of the
joint structure, in which FIG. 7A illustrates the state before
the second crimped portion forming step, and FIG. 7B
illustrates the state after the second crimped portion
20 forming step. Furthermore, FIG. 8 is a partial
cross-sectional view of the main portion illustrating a state
after the second crimped portion forming step in the certain
embodiment of the joining method of the joint structure.
The joining method of the joint structure of the present
25 embodiment includes a provisional first crimped portion
forming step of forming a provisional first crimped portion
21A (see FIG. 5) on the cylindrical member 20, and a first
crimped portion forming step and a second crimped portion
- 15 -
forming step after fitting the shaft member 10 and the
cylindrical member 20 while bringing the outer surface of the
shaft member 10 into contact with the inner surface of the
cylindrical member 20 and engaging the provisional first
crimped portion 21A with the axial groove 115 .
[0019]
(Provisional First Crimped Portion Forming Step)
The provisional first crimped portion forming step is
a step of forming plural projections on the inner
10 circumferential surface of the cylindrical member 20 such
that these projections is engaged with the plural axial
grooves 11 provided on the shaft member 10, respectively. It
is to be noted that the provisional first crimped portions
21A are projections that are provided beforehand at positions
15 where the first crimped portions 21 are to be provided on the
outer circumferential surface of the cylindrical member 20
and project from the inner circumferential surface of the
cylindrical member 20. That is, the cylindrical member 20
is fitted to the shaft member 10 while engaging the projects
20 of the provisional first crimped portions 21A with the axial
grooves 11.
[0020]
(First Crimped Portion Forming Step)
Furthermore, as illustrated in FIGs. 6A and 6B, the first
25 crimped portion forming step is a step of forming the first
crimped portions 21 by further crimping the provisional first
crimped portions 21A in a state in which the positions of the
provisional first crimped portions 21A provided on the
- 16 -
cylindrical member 20 in the provisional first crimped
portion forming step are matched to a position where the
second crimped portion is to be formed in the second crimped
portion forming step described below.
Herein, a description is made of a relationship betwee5 n
the diameter of the circle inscribed to the projections of
the provisional first crimped portions, projecting from the
from the inner circumferential surface of the cylindrical
member and the curvature radius of the bottom portion in the
10 cross section in the circumferential direction of the axial
grooves. FIG. 14 is a cross-sectional view of the main
portion illustrating a fitting state in a case in which the
cylindrical member is crimped and fixed to the shaft member
having axial grooves and the cross‐sectional shape of the
15 axial grooves in the circumferential direction is a single
circular arc.
In the aspect illustrated in FIG. 14, since the
projection comes into contact with the axial groove only at
the tip of the projection (also at the bottom of the groove),
20 there is no rigidity in the rotational direction. Thus, the
function as a rotation stopper is not sufficient. This
applies to not only the case in which the cross-sectional
shape of the axial grooves is a single circular arc but also
any case in which the cylindrical member is fitted to the shaft
25 member at the tip of the projection.
[0021]
Furthermore, FIG. 15 is a cross-sectional view of the
main portion illustrating a fitting state in a case in which
- 17 -
the cylindrical member is crimped when the diameter of the
circle inscribed to the projections of the provisional first
crimped portions, projecting from the inner circumferential
surface of the cylindrical member is substantially equal to
the curvature radius of the bottom portion in the cros5 s
section in the circumferential direction of the axial
grooves.
In the aspect illustrated in FIG. 15, the rigidity in
the rotational direction can be obtained, however, the
10 shoulder portion of the axial groove is more likely to damage
the projection due to a phase shift in assembling.
Furthermore, when the projection is formed on the
cylindrical member 20 by deformation processing, springback
may result in a shear drop at the foot of the projection. In
15 order to avoid these problems, it is necessary to provide a
grinding undercut at the shoulder portion of the axial groove,
and thus, the fitting depth between the axial groove and the
projection becomes shallower.
[0022]
20 Therefore, in the present embodiment, the diameter of
the circle inscribed to the projections of the provisional
first crimped portions 21A provided on the cylindrical member
20 beforehand, projecting from the inner circumferential
surface of the cylindrical member 20 is set lager than the
25 curvature radius of the bottom portion in the cross section
in the circumferential direction of the axial grooves 11 of
the shaft member 10. That is, in the state illustrated in
FIG. 6A (before the first crimped portion forming step), there
- 18 -
is a gap between the projection of the provisional first
crimped portion 21A provided on the cylindrical member 20
beforehand, projecting from the inner circumferential
surface of the cylindrical member 20 and the axial groove.
Therefore, the axial groove 11 does not scrape off th5 e
projection of the provisional first crimped portion 21A in
an assembling step. Furthermore, as the projection does not
come into contact with the shaft member 10, the working
accuracy of the projection does not affect assembling
10 accuracy.
[0023]
Then, with the advance of crimping the provisional first
crimped portion 21A in the first crimped portion forming step,
as illustrated in FIG. 6B, the projection projecting from
15 inner circumferential surface of the cylindrical member 20
is deformed toward the axial groove 11 to come into contact
with the axial groove 11. It is to be noted that the diameter
of the circle inscribed to the projections of the first
crimped portions 21, projecting from the inner
20 circumferential surface of the cylindrical member 20 is still
lager than the curvature radius of the bottom portion in the
cross section in the circumferential direction of the axial
grooves 11 also after the first crimped portion forming step.
By such a configuration, it is possible to stably ensure
25 a rotation stopping function regardless of a dimensional
relation between the projection and the axial groove 11.
[0024]
(Second Crimped Portion Forming Step)
- 19 -
As illustrated in FIGs. 7A and 7B, the second crimped
portion forming step is a step of crimping the cylindrical
member 20 along the circumferential groove 12 of the shaft
member 10 by reducing a diameter of an axially intermediate
portion of the cylindrical member 20 in a radial directio5 n
by using a die 30, the cylindrical member 20 being fitted to
the shaft member 10 to form the second crimped portion 22.
It is to be noted that, in the second crimped portion forming
step, the second crimped portion 22 is formed so as to be
10 connected to the first crimped portion.
The die 30 includes plural approximately fan-shaped
divided bodies 31 combined in the circumferential directions
to form a circular ring-shape. Each divided body 31 has an
inner circumferential surface having a shape capable of
15 coming into contact with the outer diameter of the cylindrical
member 20. The divided body 31, as illustrated in FIGs. 7A
and 7B for example, has a shape obtained by dividing the
circular ring-shaped die 30 into six pieces. It is to be noted
that, in FIGs. 7A and 7B, representation of one divided body
20 31 is omitted.
Each divided body 31 has a protruding portion 31a on the
inner circumferential surface thereof for pushing the
cylindrical member 20 to the circumferential groove 12 to
forming the second crimped portion 22.
25 In the second crimped portion forming step, first, as
illustrated in FIG. 6A, the die 30 is arranged to surround
the cylindrical member 20 after the first crimped portion
forming step on the outer circumferential surface side.
- 20 -
[0025]
Next, as illustrated in FIG. 6B, the respective divided
body 31a are pushed in synchronization with one another by
using an apparatus (not illustrated) of synchronizing the
respective divided body 31a with one another so as to pus5 h
the respective divided body 31a toward the axis line of the
die 30. As a result, the diameter of the cylindrical member
20 is reduced in the radial direction to form the second
crimped portion 22 which is connected to the first crimped
10 portions 21 and crimped along the circumferential groove 12.
Herein, in the second crimped portion forming step, as
illustrated in FIG. 8, it is preferable that the positon O1
in the axis direction of the tip of the projection of the second
crimped portion 22, projecting from the inner circumferential
15 surface of the cylindrical member 20 be set to be displaced
from the position O2 of the lowest point of the
circumferential groove 12. This is because when the positon
O1 in the axis direction of the tip of the projection is located
at the position O2 of the lowest point of the circumferential
20 groove 12, an engaging amount between the axial groove 11 and
the projection may become small, and thus, desired rigidity
may be hardly obtained. On the other hand, when an offset
amount between the projection and the circumferential groove
12 is too large, deformation of the projection by crimping
25 becomes insufficient, and thus the projection does not
exhibit a function as a rotation stopper.
[0026]
- 21 -
For these reasons, it is preferable to lay out the
position O1 of the tip in the axis direction of the projection
within a predetermined range on the side surface side of the
circumferential groove 12.
It is to be noted that, in FIG. 8, by laying out th5 e
projection not only as "the projection of the second crimped
portion 22" but also as a projection of the provisional first
crimped portion 21A, and reducing the diameter of the
cylindrical member 20 along the circumferential groove 12,
10 the first crimped portion 21 and the second crimped portion
22 which is connected to the first crimped portion 21 and
crimped along the first crimped portion 21 can be formed at
the same time. The step of performing the first crimped
portion forming step and the second crimped portion forming
15 step at the same time is referred to as a crimped portion
forming step.
[0027]
(Other Embodiments)
FIG. 9 is a cross-sectional view illustrating a
20 configuration of the circumferential groove in another
embodiment of the joint structure and the joining method.
Furthermore, FIGs. 10A and 10B are perspective views
illustrating states in the second crimped portion forming
step in the other embodiment of the joint structure and the
25 joining method, in which FIG. 10A illustrates the state before
the second crimped portion forming step, and FIG. 10B
illustrates the state after the second crimped portion
forming step. It is to be noted that, in the description of
- 22 -
the present embodiment, a description of a duplicate
configuration with that of the above-mentioned embodiment is
omitted.
As illustrated in FIGs. 9, 10A, and 10B, in the present
embodiment, the axial grooves 11 of the shaft member 10 hav5 e
a bathtub-shaped cross-section in the circumferential
direction. Such a shape makes the projection come into
contact with the both side surfaces of the axial groove 11
to obtain rigidity in the rotational direction. It is to be
10 noted that, as illustrated in FIGs. 9, 10A, and 10B, a flat
portion is provided on the bottom portion of the axial groove
11, and the both sides of the flat portion rise at 60 degrees.
[0028]
Furthermore, the open width of the axial groove 11 is
15 designed to be wider than the width of the foot of the
projection. Thus, the dimensional relation is designed such
that the shoulder portion of the axial groove 11 and the
projection do not interfere with each other at the time of
assembling.
20 Furthermore, it is preferable that the axial groove 11
be worked by cold forging work, and that the shaft member 10
be formed by performing a machining process on the cold forged
product. At this time, when the side surface of the axial
groove 11 linearly rises toward the outer diameter of the
25 shaft member 10, burrs may be generated when the outer
circumferential surface is machined and may come into contact
with the projection. In order to avoid this, it is preferable
that the both side surfaces of the axial groove 11 have a shape
- 23 -
that opens outward in the vicinity of the outer
circumferential surface of the shaft member 10.
[0029]
Herein, photographs of the cylindrical member 20 of the
present embodiment illustrated in FIGs. 9, 10A, and 10B ar5 e
represented in FIGs. 11A to 11D. FIGs. 11A to 11C are
photographs of the projection viewed from directly above on
the outer diameter side of the cylindrical member 20. These
photographs represent an aspect in which the crimping by
10 reducing the diameter progresses in the order of FIGs. 11A,
11B, and 11C. Furthermore, FIG. 11D is a photograph of the
state of the projection on the inner diameter side of the
cylindrical member 20 after the crimping by reducing the
diameter. In the photograph, it can be confirmed that the
15 side surface shape of the axial groove 11 is transferred to
the both side surface of the projection. As illustrated in
FIGs. 11A to 11D, it is found that the contact between the
projection and the side surface of the axial groove 11 allows
joining without looseness in the rotational direction.
20 [0030]
Furthermore, FIGs 12A to 12C are graphs illustrating a
rotation stopping effect of the projection, in which a torque
applied to the joined portion of the shaft member 10 and the
cylindrical member 20 is illustrated on a vertical axis, and
25 a relative angle between the shaft member 10 and the
cylindrical member 20 is shown on a horizontal axis. It is
to be noted that the rises of the torque at the both ends in
each diagram indicate points where the torque rises since the
- 24 -
projaction comes into contact with the side surface of the
axial groove 11. It is to be noted that FIGs. 12A to 12C
illustrate measurement results in the respective states
illustrated in FIGs. 11A to 11C, respectively, and indicate
the relationship between the progress of the crimping b5 y
reducing the diameter and the looseness in the rotational
direction. As illustrated in FIGs. 12A to 12C, it can be
confirmed that as the crimping by reducing the diameter
progresses and the projection comes into contact with the side
10 surface of the axial groove 11, the looseness in the
rotational direction becomes smaller.
As described above, according to the certain embodiment
of the present disclosure, the first crimped portion formed
on the cylindrical member 20 is deformed to be pushed to the
15 axial groove 11 with the crimping of the cylindrical member
20 in the second crimped portion forming step, and given a
function of the rotation stopper as a result.
[0031]
Furthermore, in the configuration of the present
20 embodiment, since the projection and the axial groove 11 have
a relationship in which there is completely a gap therebetween
at the time of assembling, it is not need to worry about the
scraping of the projection and an influence on the assembling
accuracy described above. Furthermore, since the first
25 crimped portion is provided on the intersection between the
axial groove 11 and the circumferential groove 12, the
projection is deformed toward the axial groove 11 with
crimping of the cylindrical member 20 by reducing the diameter.
- 25 -
Thus, there is no gap between the projection and the axial
groove 11 after crimping (after the second crimped portion
forming step), the projection exhibits a function as a
rotation stopper.
Therefore, it is possible to provide a joint structur5 e
capable of suitably joining the shaft member and the
cylindrical member which compose the joint structure, and to
provide a joining method thereof.
[0032]
10 As above, the description has been made of the joint
structure and the joining method thereof. However, the joint
structure according to the present disclosure and the joining
method thereof are not limited to the above-described
embodiments, and are modifiable in various ways without
15 departing from the spirit of the present invention. For
example, detailed conditions such as the shapes and the
numbers of the axial groove and the circumferential groove,
and the shapes and the numbers of the first crimped portion
and the second crimped portion are alterable within a range
20 where the functions of the present invention are exhibited.
Reference Signs List
[0033]
1 joint structure
25 10 shaft member
11 axial groove
12 circumferential groove
20 cylindrical member
21 first crimped portion (spherical projection)
22 second crimped portion

CLAIMS
1. A joint structure comprising:
a shaft member; and
a cylindrical member, an inner surface of which is fitte5 d
to an outer surface of the shaft member, the cylindrical
member including:
a plurality of first crimped portions which are
crimped along a plurality of axial grooves provided in an
10 axial direction of the shaft member, respectively; and
a second crimped portion which fits the axial
grooves and is crimped along a circumferential groove, the
circumferential groove being provided on a circumferential
surface of the shaft member by reducing a diameter of an
15 axially intermediate portion of the cylindrical member in a
radial direction.
2. The joint structure according to claim 1, wherein each
of the first crimped portions has a shape projecting from the
20 inner circumferential surface of the cylindrical member as
a spherical projection.
3. The joint structure according to claim 2, wherein a
position of a tip in the axis direction of the spherical
25 projection is laid out within a predetermined range on a side
surface side of the circumferential groove.
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4. The joint structure according to any one of claims
1 to 3, wherein a diameter of a circle inscribed to the first
crimped portions is set lager in cross section than a
curvature radius of a bottom portion in a circumferential
direction of each of the plurality of axial grooves5 .
5. The joint structure according to any one of claims
1 to 4, wherein the circumferential groove has a
bathtub-shaped cross-section in the axial direction.
10
6. A joining method of a joint structure, the joining
method comprising:
a provisional first crimped portion forming step for
forming a plurality of projections on an inner
15 circumferential surface of a cylindrical member such that the
plurality of projections are engaged with a plurality of axial
grooves provided on a shaft member, respectively;
fitting the shaft member to the cylindrical member such
that an outer surface of the shaft member comes into contact
20 with the inner surface of the cylindrical member, and such
that the projections on the inner circumferential surface of
the cylindrical member engage with the plurality of axial
grooves provided on the shaft member and a circumferential
groove provided on a circumferential surface of the shaft
25 member; and
a crimped portion forming step for forming first crimped
portions and a second crimped portion which is connected the
first crimped portions and crimped along the circumferential
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groove at the same time by laying out a tip in an axis direction
of each of the plurality of the projections of respective
provisional first crimped portions within a predetermined
range on a side surface side of the circumferential groove,
and by reducing a diameter of the cylindrical member alon5 g
the circumferential groove provided on the circumferential
surface of the shaft member.
7. A joining method of a joint structure, the joining
10 method comprising:
a provisional first crimped portion forming step for
forming a plurality of projections on an inner
circumferential surface of a cylindrical member such that the
plurality of projections are engaged with a plurality of axial
15 grooves provided on a shaft member, respectively;
fitting the shaft member to the cylindrical member such
that an outer surface of the shaft member comes into contact
with the inner surface of the cylindrical member, and such
that the plurality of axial grooves provided on the shaft
20 member engage with the projections on the inner
circumferential surface of the cylindrical member; and
a first crimped portion forming step for forming first
crimped portions by deforming provisional first crimped
portions along the axial grooves of the shaft member; and
25 a second crimped portion forming step for forming a
second crimped portion which is connected the first crimped
portions and crimped along a circumferential groove provided
on a circumferential surface of the shaft member by reducing
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a diameter of an axially intermediate portion of the
cylindrical member in a radial direction.
8. The joining method of the joint structure according
to claim 6 or 7, wherein each of the first crimped portion5 s
formed in the crimped portion forming step or the first
crimped portion forming step has a shape projecting from the
inner circumferential surface of the cylindrical member as
a spherical projection.
10
9. The joining method of the joint structure according
to any one of claims 6 to 8, wherein a diameter of a circle
inscribed to the first crimped portions is set lager in cross
section than a curvature radius of a bottom portion in a
15 circumferential direction of each of the plurality of axial
grooves.
10. The joining method of the joint structure according
to any one of claims 6 to 9, wherein the circumferential groove
20 has a bathtub-shaped cross-section in the axial direction.