U.S. patent application number 12/335113 was filed with the patent office on 2009-08-06 for resin boots for constant velocity universal joint.
This patent application is currently assigned to Fukoku Co., Ltd.. Invention is credited to Kazuhiko SUEOKA, Yasuji Takada.
Application Number | 20090194953 12/335113 |
Document ID | / |
Family ID | 46322607 |
Filed Date | 2009-08-06 |
United States Patent
Application |
20090194953 |
Kind Code |
A1 |
SUEOKA; Kazuhiko ; et
al. |
August 6, 2009 |
RESIN BOOTS FOR CONSTANT VELOCITY UNIVERSAL JOINT
Abstract
A resin boot for constant velocity universal joint, includes: a
resin bellows including an approximately conical bellows-shaped
portion with its inner hollow part, a small diameter end portion
communicated with an inner space of the bellows-shaped portion and
arranged at one end, and a large diameter side end portion
communicated with the inner space of the bellows-shaped portion and
arranged at the other end; a large thickness portion formed in an
inner surface of a large diameter side end portion of the resin
bellows in accordance with an injection molding, protruded in the
vertical direction to the center of the large diameter side end
portion and arranged in the circumferential direction at regular
intervals; and a small thickness portion arranged between the large
thickness portions and formed thinner in the diametrical direction
compared with large thickness portion.
Inventors: |
SUEOKA; Kazuhiko; (Ageo-shi,
JP) ; Takada; Yasuji; (Ageo-shi, JP) |
Correspondence
Address: |
RADER FISHMAN & GRAUER PLLC
LION BUILDING, 1233 20TH STREET N.W., SUITE 501
WASHINGTON
DC
20036
US
|
Assignee: |
Fukoku Co., Ltd.
Ageo-shi
JP
|
Family ID: |
46322607 |
Appl. No.: |
12/335113 |
Filed: |
January 13, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11220727 |
Sep 8, 2005 |
7488259 |
|
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12335113 |
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10396520 |
Mar 26, 2003 |
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11220727 |
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Current U.S.
Class: |
277/636 |
Current CPC
Class: |
B29L 2023/18 20130101;
B29C 45/14336 20130101; B29L 2031/703 20130101; F16D 3/845
20130101; Y10S 464/905 20130101 |
Class at
Publication: |
277/636 |
International
Class: |
F16J 15/52 20060101
F16J015/52 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 19, 2003 |
JP |
2003-041317 |
Claims
1.-3. (canceled)
4. A resin boot for a constant velocity universal joint,
comprising: a resin bellows including an approximately conical
bellows-shaped portion with an inner hollow space, a small diameter
end portion communicated with an inner space of the bellows-shaped
portion and arranged at one end thereof, and a large diameter side
end portion communicated with the inner space of the bellows-shaped
portion and arranged at the other end thereof, the large diameter
side end having a plurality of protrusion portions protruded toward
a central axis of the large diameter side end portion and arranged
in a circumferential direction at approximately regular intervals;
a different thickness portion including a plurality of large
thickness portions, each corresponding to the plurality of
protrusion portions, and a plurality of small thickness portions,
each arranged between the adjacent plurality of large thickness
portions and formed thinner in a diametrical direction than the
large thickness portions, and formed such that the plurality of
large thickness portions and the plurality of small thickness
portions are continuously formed in the circumferential direction;
and an integrally welded portion between an outer surface of the
large diameter side end portion of the resin bellows and the
different thickness portion, wherein the different thickness
portion is welded and integrated with the outer surface of the
large diameter side end portion of the resin bellows by injection
molding, whereby the integrally welded portion is formed.
5. The resin boot for a constant velocity universal joint according
to claim 4, wherein a small thickness portion molding space and a
large thickness portion molding space are formed in the outer
surface of the large diameter side end portion of the bellows, and
wherein a molten material is injected into the small thickness
portion molding space and the large thickness portion and the small
thickness portion are welded and integrated with the outer surface
of the large diameter side end portion.
6. The resin boot for a constant velocity universal joint according
to claim 5, wherein the molten material is injected into an
approximate center in the circumferential direction of the small
thickness portion molding space.
Description
DESCRIPTION OF THE RELATED APPLICATION
[0001] The present application is a divisional application of the
US Patent Publication No. US 2006/0068925 A1 which was filed on
Sep. 8, 2005 and published on Mar. 30, 2006.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a resin boot for constant
velocity universal joint used in a state of being firmly fixed to
an outer peripheral surface of a tripod joint, an outer periphery
of which is formed in a convex-recess shape, in a constant velocity
universal joint, for example, used in a drive shaft and a propeller
shaft for transmitting a power from an engine of a motor vehicle to
a tire.
[0004] 2. Description of the Related Art
[0005] The tripod joint has recess portions formed in desired
portions on the outer peripheral surface for various purposes such
as reduction in thickness, reduction in weight and the like.
[0006] In the resin boot for constant velocity universal joint used
in a state of being firmly fixed to the outer peripheral surface of
the constant velocity universal joint, a bellows-shaped portion
thereof plays a part in a cover and also a part in bending in
correspondence to a motion of the drive shaft, the propeller shaft
or the like, and an end portion thereof is firmly fixed to the
outer periphery of the constant velocity universal joint via a band
and plays a part in an oil (grease) seal and dust seal.
[0007] Accordingly, it is necessary to form an inner periphery of
the end portion of the boot in a shape closely attached so as to be
aligned with the outer periphery of the tripod joint (a joint outer
race or the like), and since the tripod joint has the recess
portions formed in the outer periphery thereof as described above,
it is necessary that the end portion in a large diameter side
firmly fixed to the outer periphery be formed to have an inner
periphery having a different thickness portion.
[0008] In the past, as a boot for constant velocity universal joint
used for a tripod joint, there is known a boot having a structure
as shown in FIG. 24 and FIG. 25 (for example, refer to Catalogue
"Constant Velocity Universal Joints or Automobiles" (CAT. No.
5601-II/JE) page 9, issued on Feb. 3, 2000 by NTN Co., Ltd).
[0009] According to the structure of the related art, the boot
includes a resin bellows 100 which is formed, for example, by an
injection blow molding and has a large diameter side end portion
101 having a uniform thickness, and a rubber grommet 200 which has
an outer diameter fitted to an inner surface of the large diameter
side end portion 101 of the resin bellows 100, is formed in a
circular ring shape, and has thickness portions 201 protruding in
an inner diameter direction every fixed intervals. An outer
periphery of the grommet 200 independently formed as mentioned
above is fit to the inner periphery of the large diameter side end
portion 101 of the bellows 100. An inner periphery of the grommet
200 is fit to an outer periphery of the tripod joint 80. The boot
is fastened and firmly fixed to the outer periphery of the tripod
joint 80 from the outer peripheral side of the large diameter side
end portion 101 by a fastening device such as a band 300 or the
like.
[0010] Further, in the past, a resin grommet having thickness
portions protruding in an inner diameter direction every fixed
intervals is previously formed, the grommet is held within a metal
mold and thereafter injection molding or blow molding of a resin
bellows is executed, to thereby integrate the grommet and the
bellows within the metal mold (for example, refer to Japanese
Unexamined Utility Model Registration Application Publication No.
2-22463 and Japanese Unexamined Patent Publication No.
2002-286048).
[0011] However, when assembling the boot having the structure as
shown in FIG. 24 and FIG. 25 in which the bellows 100 and the
grommet 200 are independently formed and are fitted and assembled,
there is a fear in that a grease may leak. That is, if the fitting
operation is carelessly carried out at a time of fitting the
grommet 200 to the inner periphery of the bellows large diameter
side end portion 101, a displacement is generated between the both
elements. Alternatively, it is possible to outward fit the bellows
large diameter side end portion 101 after fitting the grommet 200
to the outer periphery of the tripod joint 80, however, there is a
fear in that a displacement may be generated between the bellows
large diameter side end portion 101 and the grommet 200, thereby
generating grease leakage.
[0012] Further, in Japanese Unexamined Utility Model Registration
Application Publication No. 2-22463 and Japanese Unexamined Patent
Publication No. 2002-286048, no specific technical means is
provided in integrally forming the grommet and the bellows, so the
both elements are not securely welded even if they are integrally
formed on the surface. Accordingly, the portion which is expected
to be integrally formed peels off, with the result that there is
generated a problem such as grease leakage.
SUMMARY OF THE INVENTION
[0013] The inventors have paid attention to a dichroic molding, and
have succeeded in developing a resin boot for constant velocity
universal joint in which a different thickness portion including
thick and thin portions is secondarily formed by injection molding
on the inner or outer surface of the large diameter side end
portion of the resin bellows which is previously formed in primary
molding.
[0014] The present invention is made in view of, and there is a
need to provide a resin boot for constant velocity universal joint
in which a different thickness portion including large thickness
portions and small thickness portions are welded and integrated in
an inner or outer surface of a large diameter side end portion of a
primarily molded resin bellows by injection molding.
[0015] According to an aspect of the invention, a resin boot for a
constant velocity universal joint, includes a resin bellows, a
different thickness portion, and an integrally welded portion. The
resin bellows includes an approximately conical bellows-shaped
portion with an inner hollow space, a small diameter side end
portion communicated with the inner space of the bellows-shaped
portion and arranged at one end thereof, and a large diameter side
end portion communicated with the inner space of the bellows-shaped
portion and arranged at the other end thereof. The large diameter
side end portion has a plurality of protrusion portions protruded
toward a central axis of the large diameter side end portion and
arranged in a circumferential direction at approximately regular
intervals. The different thickness portion includes a plurality of
large thickness portions, each corresponding to the plurality of
protrusion portions, and a plurality of small thickness portions,
each arranged between the adjacent plurality of large thickness
portions and formed thinner in a diametrical direction than the
large thickness portions, and formed such that the plurality of
large thickness portions and the plurality of small thickness
portions are continuously formed in the circumferential direction.
The integrally welded portion exists between an inner surface of
the large diameter side end portion of the resin bellows and the
different thickness portion. The different thickness portion is
welded and integrated with the outer surface of the large diameter
side end portion of the resin bellows by injection molding, whereby
the integrally welded portion is formed.
[0016] In the resin boot for a constant velocity universal joint, a
small thickness portion molding space and a large thickness portion
molding space are formed in the outer surface of the large diameter
side end portion of the bellows. A molten material is injected into
the small thickness portion molding space and the large thickness
portion and the small thickness portion are welded and integrated
with the outer surface of the large diameter side end portion.
[0017] In the resin boot for a constant velocity universal joint,
the molten material is injected into an approximate center in the
circumferential direction of the small thickness portion molding
space.
[0018] According to the above aspect of the present invention,
there can be provided a resin boot for a constant velocity
universal joint in which the different thickness portions including
large thickness portions and small thickness portions are welded
and integrated with the outer surface of the large diameter side
end portion of the resin bellow by injection molding, whereby it is
possible to solve the problem of the grease leakage and, at the
same time, improve an assembling operability.
[0019] Further, as for the resin boot for a constant velocity
universal joint in which the different thickness portion including
the large thickness portions and the small thickness portions are
welded and integrated with the outer surface of the large diameter
side end portion of the resin bellow by secondary molding, a
contact portion of the molten material from injected at the time of
secondary molding cannot be seen, with the result that an excellent
sealing effect is attained and grease does not leak.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a vertical sectional view showing a resin boot for
constant velocity universal joint in accordance with an embodiment
of the present invention;
[0021] FIG. 2 is a cross-sectional view showing the resin boot for
constant velocity universal joint in accordance with the embodiment
of the present invention;
[0022] FIG. 3 is a simplified cross-sectional view showing a
secondary molding step of this embodiment;
[0023] FIG. 4 is an enlarged cross-sectional view showing a main
part in FIG. 3;
[0024] FIG. 5 is an enlarged cross-sectional view showing a
secondarily molded large diameter side end portion in a partly
omitted manner;
[0025] FIG. 6 is a simplified cross-sectional view of the resin
bellows;
[0026] FIG. 7 is a bottom view of the resin bellows;
[0027] FIG. 8 is a simplified cross-sectional view showing a fitted
form of an outer circumference of a core mold into an inner surface
of a boundary between a large diameter side end portion of the
resin bellows and the end portion of the bellows-shaped
portion;
[0028] FIG. 9 is a simplified cross-sectional view showing a form
of transferring to a step of clamping the outer surface of the
large diameter side end portion of a resin bellows with a split
mold;
[0029] FIG. 10 is a simplified cross-sectional view showing a form
of clamping the large diameter side end portion of a resin bellows
with a core mold and a split mold;
[0030] FIG. 11 is a simplified view showing the injection positions
of a molten material (pin gate positions);
[0031] FIG. 12 is a simplified cross-sectional view showing a form
of injecting the molten materials from small thickness portion
molding spaces;
[0032] FIG. 13 is a simplified cross-sectional view showing a form
of the molten material, which is injected from the small thickness
portion molding spaces, flowing in the small thickness portion
molding spaces;
[0033] FIG. 14 is a simplified bottom view showing a form shown
from the bottom side of the large diameter side end portion of the
form in FIG. 13;
[0034] FIG. 15 is a simplified bottom view showing a form of the
molten material, which is injected from the small thickness portion
molding spaces, flowing to the opposite two sides of conical
directions each directing the large thickness molding spaces;
[0035] FIG. 16 is a simplified bottom view showing a form of the
molten material flown into the large thickness molding spaces being
mixed and flown together;
[0036] FIG. 17 is a simplified bottom view showing a form of the
molten material being cured such that the entirely welded secondary
molding part is integrated into the inner surface of the large
diameter side end portion of the resin bellows;
[0037] FIG. 18 is a simplified cross-sectional view showing an open
form of the split mold;
[0038] FIG. 19 is a cross-sectional view showing a resin boot for
constant velocity universal joint in accordance with a second
embodiment of the present invention in a simplified manner;
[0039] FIG. 20 is a simplified bottom view showing a form of the
molten material, which is injected from the small thickness portion
molding spaces, flowing to the opposite two sides of conical
directions each directing the large thickness molding spaces;
[0040] FIG. 21 is a cross-sectional view showing a form a secondary
molding part being welded and integrated into the outer surface of
the large diameter side end portion of the resin bellows in
accordance with the second embodiment;
[0041] FIG. 22 is a simplified bottom view showing a form shown
from the bottom side of the form in FIG. 21;
[0042] FIG. 23 is an enlarged simplified cross-sectional view
showing the position of the pin gate in FIG. 19;
[0043] FIG. 24 is a vertical sectional side view of a form of a
conventional resin boot for constant velocity universal joint being
mounted on a tripod joint; and
[0044] FIG. 25 is a vertical sectional front view of a form
sectionalized at the position of the large diameter side end
portions of the resin boot for constant velocity universal joint in
accordance with the form in FIG. 24.
DESCRIPTION OF THE PREFERRED EMBODIMENT
First Embodiment
[0045] A description will be given of one embodiment in accordance
with the present invention with reference to the accompanying
drawings. In this case, the present embodiment only shows one
aspect of the present invention, and the present invention is not
limited to this embodiment any more, and can be changed in design
within the scope of the present invention as occasion demands.
[0046] FIG. 1 is a vertical sectional view showing a resin boot for
constant velocity universal joint in accordance with an embodiment
of the present invention, FIG. 2 is a cross-sectional view showing
the resin boot for constant velocity universal joint in accordance
with the embodiment of the present invention, FIG. 3 is a
simplified cross-sectional view showing the secondary molding step
of this embodiment, FIG. 4 is an enlarged cross-sectional view
showing a main part in FIG. 3, and FIG. 5 is an enlarged
cross-sectional view showing a secondarily molded large diameter
side end portion in a partly omitted manner.
[0047] The resin boot for constant velocity universal joint in
accordance with the embodiment of the present invention is used for
a constant velocity universal joint in which a desired recess
portion is formed on an outer surface, that is, a tripod joint (for
example, the tripod joint 80 described in the prior art and shown
in FIG. 24 and FIG. 25).
[0048] The boot in accordance with this embodiment as shown in FIG.
1 includes a resin bellows 8 (FIG. 6 and FIG. 7) corresponding to a
primarily molded product having a bellows-shaped portion 55 formed
in a conical shape, a large diameter side end portion 41 formed in
one end side of the bellows-shaped portion 55, and a small diameter
side end portion 40 formed in another end side, which are
integrally molded by using a thermoplastic resin, and a different
thickness portion 56 corresponding to a secondarily molded product
which is integrally molded in an inner periphery of the large
diameter side end portion 41 of the resin bellows 8 by using a
thermoplastic resin.
[0049] First, a description will be given of the resin bellows 8
corresponding to the primarily molded product shown in FIG. 6 and
FIG. 7. The resin bellows 8 corresponding to the primarily molded
product is obtained by primarily molding the bellows-shaped portion
55, the large diameter side end portion 41 and the small diameter
side end portion 40 in accordance with a known primary molding
step. The large diameter side end portion 41 and the small diameter
side end portion 40 are provided in both end sides of the resin
bellows 8 so as to be communicated with an internal space of the
bellows-shaped portion 55.
[0050] The bellows-shaped portion 55 has a desired thickness and is
formed in an approximately conical shape structured such that a
recess groove portion (also referred to as a valley portion) 62 in
which an outer diameter (or an inner diameter) becomes smaller in
accordance with being close to the small diameter side end portion
40 from the large diameter side end portion 41, and a convex groove
portion (also referred to as a peak portion) 63 are alternately
formed.
[0051] In this case, in the present invention, the bellows-shaped
portion 55 is not particularly limited, and an optimum condition
can be appropriately applied to terms and conditions such as a
thickness of the bellows-shaped portion 55, a pitch between the
valley portion 62 and the peak portion 63 and the like within the
range of the present invention.
[0052] In accordance with the present embodiment, the large
diameter side end potion 41 is structured such that an outer
periphery is formed in an approximately complete round shape and is
provided with a recess portion 59 for mounting a fastening device
such as a desired shaped band or the like in a periphery, and an
inner periphery, as shown in FIG. 5, is provided alternately with a
recess-shaped portion 57 and a convex-shaped portion 58 which are
continuously provided in a circumferential direction in a direction
of height of an end portion, in order to improve a contact force
with the different thickness portion 56 corresponding to the
secondarily molded product, whereby the inner periphery is formed
in a concavo-convex shape.
[0053] In accordance with the present embodiment, the small
diameter side end potion 40 is structured such that an outer
periphery is formed in an approximately complete round shape and is
provided with a recess portion 60 for mounting a fastening device
such as a desired shaped band or the like in a periphery, and an
inner periphery is provided with a convex groove portion 61 fitted
to a peripheral recess groove 83 which is formed in an outer
periphery of a leading end of a drive shaft in a tripod joint 80 in
a circumferential direction.
[0054] In this case, in the present embodiment, both of the large
diameter side end portion 41 and the small diameter side end
portion 40 mentioned above are respectively set to desired uniform
thicknesses. These thicknesses are not particularly limited, and an
optimum optional thickness is selected.
[0055] This several conditions of the large diameter side end
portion 41 and the small diameter side end portion 40 are not
specially limited and the most appropriate conditions are applied
within a scope of the present invention. In the present embodiment,
thickness of the large diameter side end portion 41 and the small
diameter side end portion 40 are uniformed, however an embodiment
in which the thickness is not uniformed falls within a scope of the
present invention.
[0056] Next, a description will be given of the different thickness
portion 56 corresponding to the secondarily molded product. The
different thickness portion 56 corresponding to the secondarily
molded product is welded and integrated (I) in the inner surface of
the large diameter side end portion 41 in the resin bellows 8
corresponding to the primarily molded product in accordance with a
secondary molding step.
[0057] In accordance with the present embodiment, the different
thickness portion 56, as shown in FIG. 1, FIG. 2, and FIG. 17, is
constituted by three large thickness portions 56a and three small
thickness portions 56b which are alternately formed continuously in
the inner periphery of the large diameter side end portion 41 of
the resin bellows 8 with a fixed interval in a circumferential
direction by using a thermoplastic resin (for example, a polyester
thermoplastic elastomer).
[0058] In FIG. 5, a solid line portion shows the large thickness
portion 56a, and a broken line portion shows the small thickness
portion 56b. A range shown by reference symbol b in the drawing is
a diametrically thickness common portion in each of the portions
and has the same thickness in a circumferential direction. Further,
a position shown by reference symbol c in the drawing shows a
boundary point in the diametrical thickness between the large
thickness portion 56a and the small thickness portion 56b.
[0059] The large thickness portion 56a is formed in a convex shape
which is closely contacted with and fitted to the recess portion 81
formed in the outer periphery of the outer case of the tripod joint
80, and in the present embodiment, three large thickness portions
are formed in an R-shaped convex shape at approximately regular
intervals in the circumferential direction and protrude toward a
central axis direction of the large diameter portion 41.
[0060] A depth of this large thickness portion 56a (the boundary
point in the diametrical thickness between the large thickness
portion 56a and the small thickness portion 56b) is up to an inner
wall just before position d (close to the large diameter side end
portion rather than an inner wall of a boundary 62a) of the
boundary 62a between the large diameter side end portion 41 of the
resin bellows 8 and the bellows-shaped portion 55.
[0061] The small thickness portion 56b is formed by a curved
surface having an inner diameter which is closely contacted with
the outer periphery of the outer case 82 except the recess portion
81 of the tripod joint 80. In this embodiment, the small thickness
portion 56b has the diametrical thickness smaller than that of the
large thickness portion 56a, and is disposed between the large
thickness portions 56a.
[0062] That is, when the boundary point c between the end edge
(depth) close to the direction of the small diameter side end
portion 40 of the large thickness portion 56a and the inner surface
of the small thickness portion 56b comes to the inner wall of the
boundary 62a between the large diameter side end portion 41 and the
bellows-shaped portion 55, there is a high risk that a crack is
generated due to a stress generated in the periphery of the inner
surface of the boundary 62a, on the basis of the expansion, the
free movement and the like in the portion of the boundary 62a.
Accordingly, the boundary point c is set such as not to be
positioned in the inner wall of the boundary 62a mentioned above or
the inner wall close to the small diameter side end portion over
the inner wall of the boundary 62a.
[0063] Terms and conditions such as a shape, a number, a thickness,
a width, a depth and the like of the large thickness portion 56a
and the small thickness portion 56b can be appropriately changed in
correspondence to an outer peripheral shape of the tripod joint to
be subjected.
[0064] Further, in the present embodiment, as shown in FIGS. 2 and
5, two non-penetrating holes (recess portions) 86 are provided in
an axial direction of the large thickness portion 56a, thereby
intending to achieve a weight saving, a shrinkage prevention and an
improvement of elasticity.
[0065] In this case, one or two holes 86 are provided in all of the
large thickness portions. Further, in the present embodiment, the
hole 86 is provided in all of the large thickness portions,
however, may be provided in optionally selected large thickness
portions. Further, in the present embodiment, the hole is formed in
the frustum shape which has a complete round shape in a
cross-sectional view and has the diameter smaller in accordance
with going in the depth direction (the direction of the small
diameter side end portion), however, it is possible to select any
optional shape such as an oval shape in a cross-sectional view, a
tear drop shape in a cross-sectional view or the like, and it is
possible to change in design within the range of the present
invention.
[0066] The thermoplastic resin for structuring the resin bellows 8
corresponding to the primarily molded product and the different
thickness portion 56 corresponding to the secondarily molded
product is not particularly limited, an optimum material within the
range of the present invention is selected, and whichever they are
made of the same material, materials having different hardness or
different materials, they are within the range of the present
invention. In this case, the different thickness portion 56
corresponding to the secondarily molded product is preferably made
of a material having a seal function of preventing the grease from
leaking, and on the other hand, the resin bellows 8 corresponding
to the primarily molded product can select a material which purely
corresponds to an inherent object, that is, a material having a
bending property, a heat resistance, a cold resistance and the
like.
[0067] Next, a description will be given of one embodiment of a
method of manufacturing the resin boot for constant velocity
universal joint in accordance with the present invention.
[0068] [Resin Bellows Preparing Step]
[0069] As a method of molding the resin bellows 8 (FIG. 6 and FIG.
7) in which the thickness of the large diameter side end portion 41
mentioned above is uniform, a blow molding, an injection blow
molding and the like are well known, however, the method is not
particularly limited, and an optimum bellows molding method is
appropriately employed within the range of the present
invention.
[0070] [Secondarily Molding Step]
[0071] The present step is a secondarily molding step of integrally
molding the different thickness portion 56 corresponding to the
secondarily molded product in the inner surface of the large
diameter side end portion 41 of the bellows 8 by holding resin
bellows 8, which is the primarily molded in accordance with the
resin bellows preparing step, within the injection molding metal
mold 64, and injecting a desired molten material, for example, a
thermoplastic resin 4a having a high temperature equal to or more
than 260.degree. C. within the metal mold 64 at a high speed. A
description will be given of one embodiment thereof with reference
to FIGS. 3 to 18. In this case, since the known structures are
applied to the other structures than the structure described below,
a description thereof will be omitted. In this case, the injected
thermoplastic resin has the temperature equal to or more than
260.degree. C., however, the resin is not particularly limited, and
can be appropriately changed in design within the range in which
the raw material is not changed.
[0072] First, by inserting a core mold 70 to the inner surface of
the large diameter side end portion 41 of the primarily molded
resin bellows 8 mentioned above, a desired secondarily molding
space 69 is formed continuously in a circumferential direction
between the inner surface of the large diameter side end portion 41
of the resin bellows 8, and thereafter by insert holding into the
resin bellows placing space 68 of the split mold 65 the resin
bellows 8 and the core mold 70 are clamped.
[0073] The injection molding metal mold 64 is formed of a resin
bellow placing space 68 coinciding with an outer appearance shape
(an outer profile) of the resin bellows 8 by a desired split mold
65 constituting the metal mold 64.
[0074] In this case, it is possible to employ a step of previously
holding the resin bellows 8 as well as inserting to the resin
bellows placing space 68, forming a desired secondarily molding
space 69 with respect to the inner periphery of the large diameter
side end portion 41 of the resin bellows 8 so as to insert and
arrange the core mold 70, and thereafter clamping the mold. This
step is within the range of the present invention.
[0075] The resin bellows placing space 68 forms a profile in which
the outer appearance shape of the resin bellows 8 is closely
contacted with an inner surface at a time of clamping the mold, and
is formed in such a manner that an opening edge 41a of the large
diameter side end portion 41 of the resin bellows 8 is flush with
an upper end surface 65a of the split mold 65.
[0076] The core mold 70 is constituted by an approximately
cylindrical core portion 71 inserted into an inner periphery of the
large diameter side end portion 41 of the resin bellows 8, and a
disc-like collar portion 72 extended in a horizontal direction from
an upper end of the core portion 71, and forms an outer peripheral
shape of the tripod joint 80 to be subjected, the same outer
peripheral shape as the outer diameter and a portion corresponding
to the outer diameter in an outer peripheral portion 74 between an
outer periphery 73 closest to a leading end side of the core
portion 71 and the collar portion 72. Further, when the collar
portion 72 is brought into contact with the upper end surface 65a
of the split mold 65 so as to seal the above side of the secondary
molding space 69, and the outer peripheral portion 74 of the core
portion 71 is inserted, the bellows valley portion 62a closest to
the large diameter side end portion 41 in the resin bellows 8 is
clamped by the outer periphery 73 closest to the leading end side
of the outer peripheral portion 74 and the peak portions 66 of the
opposing split molds 65.
[0077] The secondary molding space 69 formed by inserting the outer
peripheral portion 74 of the core portion 71 to the inner periphery
of the large diameter side end portion 41 of the resin bellows 8 is
formed as a desired space by the outer peripheral shape of the core
portion 71 and the inner peripheral shape of the large diameter
side end portion 41.
[0078] In the present embodiment, three recess portions 75 are
formed with predetermined interval in the outer peripheral portion
of the core portion 71 and thus the large thickness portion molding
space 76 is formed between these recess portions 75 and the inner
peripheral of the large diameter side end portion 41 of the bellows
8, the small thickness portion molding space 77 connected with the
large thickness portion molding space 76 is formed between the
outer periphery other than the recess portion 75 and the inner
peripheral of the large diameter side end portion 41 of the bellows
8.
[0079] That is, when the boundary point c between the end edge
(depth) close to the direction of the small diameter side end
portion 40 of the large thickness portion 56a and the inner surface
of the small thickness portion 56b comes to the inner wall of the
boundary 62a between the large diameter side end portion 41 and the
bellows-shaped portion 55, there is a high risk that a crack is
generated due to a stress generated in the periphery of the inner
surface of the boundary 62a, on the basis of the expansion, the
free movement and the like in the portion of the boundary 62a.
Accordingly, the boundary point c is set such as not to be
positioned in the inner wall of the boundary 62a mentioned above or
the inner wall close to the small diameter side end portion over
the inner wall of the boundary 62a.
[0080] Further, the sprue is provided with projections (not shown)
for forming one or two holes 86 arranged in the large thickness
portion 56a at desired positions (three positions in the present
embodiment) of the collar portion 72 with a fixed interval.
Accordingly, the hole 86 can be formed at the same time of the
secondary molding (FIG. 2 and FIG. 5).
[0081] A pin gate 79 for injecting the thermoplastic resin into the
secondary molding space 69 via a sprue 78 is formed in the collar
portion 72 (FIGS. 3, 4 and 12). Position of the pin gate 79 of one
or a plurality of an arbitrary place in the secondary molding space
69 is selected. For example, it is possible to position the pin
gate 79 in the small thickness portion molding space 77.
[0082] In the present embodiment, the pin gate 79 is selectively
provided in an approximately center in the circumferential
direction of the small thickness portion molding space 77.
[0083] Further, the thermoplastic resin 4a is injected to each
small thickness portion molding space 77, 77, 77 from an
approximately center in the circumferential direction of the each
small thickness portion molding space 77, 77, 77 in the secondary
molding space 69, and from the pin gate 79, 79, 79 mounted on every
small thickness portion molding space 77, 77, 77 (FIGS. 3, 4 and
12).
[0084] As mentioned above, as for the thermoplastic resin 4a
injected from the pin gate 79 constituted on the approximately
center in the circumferential direction of each small thickness
portion molding space 77, the small thickness portion molding space
(small space in the interval in the diametrical direction) 77 to
the large thickness portion molding space (large space in the
interval in the diametrical direction) 76 doubles as a part of a
runner, and the thermoplastic resin 4a is fed to the large
thickness portion molding space 76 in a split second with a high
speed and a high temperature while maintaining a high temperature
state, so that a weld or an air involving is not absolutely
generated, and the inner periphery of the bellows large diameter
side end portion 41, and the large thickness portion 56a and the
small thickness portion 56b formed by the secondary molding are
completely welded and integrated.
[0085] Particularly, in the present embodiment, for example, it is
assumed of the case where there are three large thickness portion
molding spaces 76 and three small thickness portion molding space
77 therebetween, and the thermoplastic resin 4a is injected from
each pin gate 79 constituted on the approximately center in the
circumferential direction of each of the mentioned small thickness
portion molding space 77 (FIG. 11 and FIG. 12).
[0086] The thermoplastic resin 4a injected from the pin gate 79
constituted on the approximately center in the circumferential
direction of each small thickness portion molding space 77, is
immediately flown in six flows of which divided into two opposite
conical directions individually, whereby the thermoplastic resin 4a
becomes a laminar flow which runs to the direction of each large
thickness portion molding space 76 at high speed while maintaining
high temperature (FIGS. 13, 14 and 15). Arrows in each figure
represents the flow of each thermoplastic resin 4a.
[0087] That is, the thermoplastic resin 4a injected from the pin
gate 79 constituted on the approximately center in the
circumferential direction of each small thickness portion molding
space 77, runs in six flows so as to be brought into slidable
contact with the inner surface of the large diameter side end
portion 41 of the resin bellows 8, whereby the temperature of the
inner surface of the large diameter side end portion 41 is elevated
near to that of the thermoplastic resin 4a for secondary molding,
and is melted.
[0088] Next, the two opposite flows of the like of the six flows
are immediately released into the large thickness portion molding
space 76 as to collide as being a turbulent flow, and two of the
flows are mixed in complex to a sing flow (FIG. 16).
[0089] Such interflow of the thermoplastic resins 4a is generated
at three large thickness portion molding spaces 76
simultaneously.
[0090] As described above, the thermoplastic resin 4a is charged in
every corner of the secondary molding space (large thickness
portion molding space 76 and small thickness portion molding space
77) 69.
[0091] As a result, there is hardly any contact portion (weld) or
shrink mark, and the inner surface of the large diameter side end
portion (primary molding portion) 41 of the resin bellows 8 and the
secondary molding portion (each large thickness portion 56a and
small thickness portion 56b) are completely welded and integrated
(I; FIG. 17).
[0092] FIG. 18 shows a state after completion of the secondary
molding, in which the split mold 65 is pulled back as to remove
from the clamping state, and the molded boot is released from the
mold.
[0093] In this case, the structure may be made such that the pin
gate 79 is provided in the large thickness portion molding space
76, and the thermoplastic resin 4a is injected from only the large
thickness portion molding space 76 or from a plurality of portions
including the large thickness portion molding space 76, however, in
view of preventing the air defect, the weld defect and the like, it
is preferable that the pin gate 79 is provided in the small
thickness portion molding space 77 as in the present
embodiment.
[0094] Further, in accordance with the present embodiment, in order
for the inner surface of the boundary 62a between the large
diameter side end portion 41 of the resin bellows 8 and the
bellows-shaped portion 55, and the outer periphery 73 closest to
the leading end side of the core portion 71 which is in contact
with the inner surface of the boundary 62a to form so as to be
fitted to each other, a self-seal effect caused by the injection
pressure is generated as well as the contact force of that portion
is increased, so that it is possible to increase the injection
pressure of the thermoplastic resin 4a at a time of the secondary
molding. Accordingly, it is possible to firmly weld the inner
periphery of the large diameter side end portion 41 of the resin
bellows 8 to the different thickness portion 56 formed by the
secondary molding.
[0095] For example, in the present embodiment, a convex groove
portion 84 continuously provided in a circumferential direction is
integrally molded on the inner surface of the boundary 62a between
the large diameter side end portion 41 of the resin bellows 8 and
the bellows-shaped portion 55, and a recess groove portion 85
opposing to the convex groove portion 84 on the inner surface of
the boundary 62a is continuously formed in the circumferential
direction in the outer periphery 73 closest to the leading end side
of the core portion 71, thereby increasing the contact force on the
basis of the fitting between the convex groove portion 84 and the
recess groove portion 85. In this case, in reverse to the present
embodiment, the structure may be made such that the recess groove
portion continuously provided in the circumferential direction is
integrally formed on the inner surface of the boundary 62a between
the large diameter side end portion 41 of the resin bellows 8 and
the bellows-shaped portion 55 at a time of the primary molding, and
on the other hand, the convex groove portion opposing to the recess
groove portion on the inner surface of the boundary 62a is formed
continuously in the circumferential direction in the outer
periphery 73 closest to the leading end side of the core portion
71. Accordingly, it is possible to appropriately change design
within the range of the present invention as far as the structure
can increase the contact force between both of the elements.
[0096] Further, when forming at least any one of the convex portion
and the recess portion on the inner surface of the large diameter
side end portion 41 of the resin bellows 8 at the same time of the
primary molding mentioned above, it is possible to firmly weld to
the different thickness portion 56 corresponding to the secondarily
molded product.
[0097] For example, in accordance with the present embodiment,
since a plurality of recess portions 57 and convex portions 58
which are continuously provided in the circumferential direction
are alternately arranged in the height direction of the inner
surface of the large diameter side end portion 41, it is possible
to increase a welding area (I) between the inner surface of the
large diameter side end portion 41 of the resin bellows 8
corresponding to the primarily molded product and the different
thickness portion 56 corresponding to the secondarily molded
product, and it is possible to firmly weld the both. In this case,
in accordance with the present embodiment, the structure is made
such that a plurality of recess portions 57 and convex portions 58
are provided, however, the structure is not limited to this as far
as the structure can achieve a firm welding as mentioned above. For
example, it is possible to consider that one or a plurality of
independent projections or recesses is provided, and in this case,
a length of the projection can be optionally set.
[0098] Further, in the case that the convex portion 58 extending in
the circumferential direction is formed on the inner surface of the
large diameter side end portion 41 of the resin bellows 8, the
convex portion 58 doubles as a dam, and serves an operation of
uniformly flowing the thermoplastic resin 4a injected from the pin
gate 79 to the small thickness portion molding space 77 from the
small thickness portion molding space 77 to the large thickness
portion molding space 76. That is, in the case of forming the
convex portion 58 as the dam, the high speed and high temperature
thermoplastic resin 4a injected to the small thickness portion
molding space 77 first flows in the direction of the large
thickness portion molding space 76 along a drift space (a drift
space above the convex portion 58) between the pin gate 79 and the
convex portion 58, subsequently flows into a drift space below the
convex portion 58, and flows so as to follow along the drift space.
Further, the thermoplastic resins 4a flowing along the respective
drift spaces reach the large thickness portion molding space 76 at
the same time. It is preferable to adjust the height and the length
of the convex portion 58 so that the thermoplastic resins 4a
flowing to a plurality of drift spaces can reach the large
thickness portion molding space 76 at the same time.
[0099] In this case, it is sufficient that the convex portion 58 is
formed at least on the inner surface of the large diameter side end
portion 41 corresponding to the small thickness portion molding
space. Further, the convex portion 58 is optionally provided in the
present invention, and the number of the convex portions 58 can be
appropriately changed in design.
[0100] It is possible to further firmly weld the resin bellows 8
corresponding to the primarily molded product to the different
thickness portion 56 corresponding to the secondarily molded
product by setting the injection condition of the thermoplastic
resin 4a into the secondary molding space 69 as follows.
[0101] That is, a direction .theta. of the injection pin gate 79 is
set under a condition 0.degree..ltoreq..theta..ltoreq.90.degree.,
with respect to the inner surface of the large diameter side end
portion 41 of the resin bellows 8, a position condition of the
injection pin gate 79 is set to a condition 0.ltoreq.t.ltoreq.2a/3
in which a distance between the inner surface of the large diameter
side end portion 41 of the resin bellows 8 and the injection pin
gate 79 is set to t, and a diametrical distance of the injection
side end portion 69a of the secondary molding space 69 is set to
a.
[0102] Accordingly, the high temperature thermoplastic resin 4a is
injected so as to be brought into slidable contact with the inner
surface of the large diameter side end portion 41 of the resin
bellows 8, and the thermoplastic resin 4a is charged into the
secondary molding space 69.
[0103] At this time, since the injected high temperature
thermoplastic resin 4a flows so as to be brought into slidable
contact with the inner periphery of the large diameter side end
portion 41 at a high speed, impurities attached on the surface of
the inner periphery of the large diameter side end portion 41 are
washed out, and a heat of the thermoplastic resin 4a flowing at the
high temperature and high speed is transmitted to the surface of
the inner periphery, thereby melting the inner surface. Therefore,
the injected thermoplastic resin 4a is firmly welded to the surface
of the large diameter side end portion 41 which is melted by the
heat of the thermoplastic resin 4a, and the different thickness
portion 56 is integrally molded in the inner periphery of the large
diameter side end portion 41 in accordance with the secondary
molding.
[0104] Further, in accordance with the present embodiment, when
holes 86 are structured in the large thickness portion by the above
described step, a volume of the large thickness portion 56a is
reduced, so that it is possible to make cooling times for the small
thickness portion 56b and the large thickness portion 56a
coincident or approximate with each other. Further, since a
turbulent flow is extremely less generated at a time when the
thermoplastic resin 4a flows in the large thickness portion molding
space 76, a weld or an air involving is not absolutely
generated.
[0105] That is, the following operation and effect are generated,
and a sealing property is consequently improved. Since the volume
of the large thickness portion 56a is reduced, it is possible to
intend a weight saving. It is possible to provide a product which
has no shrink mark and has an extremely high dimensional accuracy.
Further, a band fastening force has no difference between the small
thickness portion 56b and the large thickness portion 56a, and
becomes approximately uniform in all peripheries. Since the large
thickness portion 56a has an elastic force, the large thickness
portion fits to the outer periphery of the tripod joint.
Second Embodiment
[0106] In the first embodiment as described above, a different
thickness portion 56 composed of large thickness portions 56a and
small thickness portions 56b are welded and integrated (I) in the
inner surface of a large diameter side end portion 41 of a
primarily molded resin bellows 8 in accordance with a secondary
molding. However, the second embodiment shown in FIGS. 19 to 22
adopted the embodiment in which a different thickness portion 560
composed of large thickness portions 560a and small thickness
portions 560b are integrally injection molded in the outer surface
of a large diameter side end portion 410 of a primarily molded
resin bellows 800 in accordance with a secondary molding, in the
purpose to achieve the same object, which will be described in
detain below.
[0107] First, a resin bellows 800 which is primarily molded
product, during the primary molding, forms a large diameter side
end portion 410 into an approximately similar shape to that of an
outer peripheral surface of an outer case of the constant velocity
universal joint. Particularly, the resin bellows 800, during the
primary molding, forms the large diameter side end portion 410 on
the inner surface form and outer surface form (an approximately
similar shape to that of an outer peripheral surface of an outer
case having convex-recess portion in circumferential direction)
constituted of three openings of a recess portion 410b
corresponding to the outer peripheral surface of an outer case of
the constant velocity universal joint (tripod joint) 80 previously
shown in FIGS. 23 and 24, and the surface portion 410c of the large
diameter side end portion 410 without the recess portion 410b
(refer to FIG. 19 and FIG. 20). In the present embodiment, the
thickness of the large diameter side end portion 410 is the same
throughout the circumferential direction as presented, but the
embodiment is not limited thereto.
[0108] In addition, the resin bellows 800 of the present embodiment
constitutes the components of the first embodiment, except that the
large diameter side end portion 410 is formed into an approximately
similar shape to that of an outer peripheral surface of an outer
case of the constant velocity universal joint.
[0109] The different thickness portion 560 corresponding to the
secondarily molded product is welded and integrated (I) to the
outer surface of the large diameter side end portion 410 of resin
bellows 800 corresponding to the primarily molded product by the
secondary molding step which will be described below.
[0110] In accordance with the embodiment, the different thickness
portion 560, as shown in FIG. 22, is constituted by three openings
of the large thickness portion 560a and three openings of the small
thickness portion 560b which are alternately formed continuously
with a fixed intervals in the circumferential direction to the
outer surface of the large diameter side end portion 410 of resin
bellows 800 using a thermoplastic resin (for example, a polyester
thermoplastic elastomer) 4a. The large thickness portion 560a is
protruded in the vertical direction to the center of the large
diameter side end portion 410 and is arranged in the
circumferential direction at regular intervals. The small thickness
portion 560b is arranged between the large thickness portion 560a
and the diametrical thickness thereof is smaller than that of the
large thickness portion 560a.
[0111] Further, in the present embodiment as the same as with the
first embodiment, two non-penetrating holes (recess portions) are
provided in an axial direction of the large thickness portion 560a,
thereby intending to achieve a weight saving, a shrinkage
prevention and an improvement of elasticity.
[0112] Next, a description will be given of one embodiment of a
method of the manufacturing resin boot for constant velocity
universal joint in accordance with the present invention.
[0113] [Resin Bellows Preparing Step]
[0114] As a method of molding the resin bellows 800 mentioned
above, a blow molding, an injection blow molding and the like are
well known, however, the method is not particularly limited, and an
optimum bellows molding method is appropriately employed within the
range of the present invention.
[0115] [Secondarily Molding Step]
[0116] The present step is a secondarily molding step of integrally
molding the different thickness portion 560 corresponding to the
secondarily molded product in the outer surface of the large
diameter side end portion 410 of the bellows 800 by holding resin
bellows 800, which is the primarily molded in accordance with the
resin bellows preparing step, within the injection molding metal
mold 640 (a split mold 650) and the core mold 700, and injecting a
desired molten material into secondary molding space 690 formed
between the outer surface of the large diameter side end portion
410 of the bellows 800 and the split mold 650, for example, a
thermoplastic resin 4a having a high temperature equal to or more
than 260.degree. C. within the metal mold 640 at a high speed by
opening the pin gate 79. A description will be given of one
embodiment thereof. In this case, since the known structures are
applied to the other structures than the structure described below,
a description thereof will be omitted. In this case, the injected
thermoplastic resin has the temperature equal to or more than
260.degree. C., however, the resin is not particularly limited, and
can be appropriately changed in design within the range in which
the raw material is not changed.
[0117] First, by inserting a core mold 700 to the inner surface of
the large diameter side end portion 410 of the primarily molded
resin bellows 800 mentioned above, thereafter, a desired
secondarily molding space 690 (large thickness portion molding
space 760 and small thickness portion molding space 770) is formed
continuously in a circumferential direction between the outer
surface of the large diameter side end portion 410 of the resin
bellows 800 and the split mold 650 (the first step, FIG. 19 and
FIG. 20).
[0118] The injection molding metal mold 640 constituted of a
desired split mold 650, and as shown in FIG. 19 and FIG. 20, is
structured by an inner peripheral end portion 640a where at least
the large diameter side end portion 410 of the resin bellows 800
close to the bellows valley portion 62a is fitted with an outer
peripheral end portion 700a of the core mold 700 described below,
when clamping the split mold 650, as well as by a recess-shaped
surface portion 640b in a conical or an approximately conical-shape
for forming fixed spaces (secondary molding space 690) in the outer
surface of the large diameter side end portion 410 of the resin
bellows 800.
[0119] The core mold 700 is inserted and arranged in the inner
surface of the large diameter side end portion 410 of the resin
bellows 800, including an outer peripheral end portion 700a exist
in fitting the large diameter side end portion 410 of the resin
bellows 800 close to the bellows valley portion 62a with the inner
peripheral end portion 640a of the split mold 640, as well as a
convex-recess surface portion 700b for being integrated to the
inner surface of the large diameter side end portion 410 of the
resin bellows 800.
[0120] The convex-recess surface portion 700b is referred to as an
outer peripheral-shape of an outer case, outer peripheral-shape of
an outer diameter and outer diameter of the tripod joint 80 to be
subjected.
[0121] In the present embodiment, the convex-recess surface portion
700b is formed of three recess portions 750 with a fixed interval
in the outer peripheral portion of the core mold 700.
[0122] As a result, when the core 700 is inserted into the inner
surface of the large diameter side end portion 410 of the resin
bellows 800, the convex-recess surface portion 700b of the core 700
coincides with the inner surface of the large diameter side end
portion 410. Then, the large thickness portion molding space 760 is
formed between the recess portion 410b of the large diameter side
end portion 410 of the resin bellows 800, which coincides with the
recess portion 750 of the convex-recess surface portion 770b, and
the recess-shaped surface portion 640b of the split mold 650. Also,
the small thickness portion molding space 770, which is connected
to the large thickness portion molding space 760, is formed between
the outer periphery 751 and the outer periphery other than the
recess portion 750, and the surface portion 710c other than the
recess portion 410b of the large diameter side end portion 410 of
the resin bellows 800.
[0123] In this embodiment, the pin gate 79 that injects the
thermoplastic resin 4a to the secondary molding space 690 is
selectively provided in an approximately center in the
circumferential direction to the small thickness portion molding
space 770 (FIG. 20).
[0124] Further, the thermoplastic resin 4a is injected to each
small thickness portion molding space 770, 770, 770 from an
approximately center in the circumferential direction of the each
small thickness portion molding space 770, 770, 770 in the
secondary molding space 690, and from the pin gate 79, 79, 79
mounted on every small thickness portion molding space 770, 770,
770 (the second step, FIGS. 19 and 20).
[0125] As mentioned above, as for the thermoplastic resin 4a
injected from the pin gate 79 constituted on the approximately
center in the circumferential direction of each small thickness
portion molding space 770, the small thickness portion molding
space (small space in the interval in the diametrical direction)
770 to the large thickness portion molding space (large space in
the interval in the diametrical direction) 760 doubles as a part of
a runner, and the thermoplastic resin 4a is fed to the large
thickness portion molding space 760 in a split second with a high
speed and a high temperature while maintaining a high temperature
state, so that a weld or an air involving is not absolutely
generated, and the outer surface of the bellows large diameter side
end portion 410, and the large thickness portion 560a and the small
thickness portion 560b formed by the secondary molding are
completely welded and integrated (the third step, FIGS. 21 and
22).
[0126] Particularly, in the present embodiment, for example, it is
assumed of the case where there are three large thickness portion
molding spaces 760 and three small thickness portion molding space
770 therebetween, and the thermoplastic resin 4a is injected from
each pin gate 79 constituted on the approximately center in the
circumferential direction of each of the mentioned small thickness
portion molding space 770 (FIG. 19 and FIG. 20).
[0127] The thermoplastic resin 4a injected from the pin gate 79
constituted on the approximately center in the circumferential
direction of each small thickness portion molding space 770, is
immediately flown in six flows of which divided into two opposite
conical directions individually, whereby the thermoplastic resin 4a
becomes a laminar flow which runs to the direction of each large
thickness portion molding space 760 at high speed while maintaining
high temperature (FIG. 20). Arrows in each figure represents the
flow of each thermoplastic resin 4a.
[0128] That is, the thermoplastic resin 4a injected from the pin
gate 79 constituted on the approximately center in the
circumferential direction of each small thickness portion molding
space 770, runs in six flows so as to be brought into slidable
contact with the outer surface of the large diameter side end
portion 410 of the resin bellows 8, whereby the temperature of the
outer surface of the large diameter side end portion 410 is
elevated near to that of the thermoplastic resin 4a for secondary
molding, and is melted.
[0129] Next, the two opposite flows of the like of the six flows
are immediately released into the large thickness portion molding
space 760 as to collide as being a turbulent flow, and two of the
flows are mixed in complex to a sing flow.
[0130] Such interflow of the thermoplastic resins 4a is generated
at three large thickness portion molding spaces 760
simultaneously.
[0131] As described above, the thermoplastic resin 4a is charged in
every corner of the secondary molding space 690 (large thickness
portion molding space 760 and small thickness portion molding space
770).
[0132] As a result, there is hardly any contact portion (weld) or
shrink mark, and the outer surface of the large diameter side end
portion (primary molding portion) 410 of the resin bellows 800 and
the secondary molding portion (each large thickness portion 560a
and small thickness portion 560b) are completely welded and
integrated (I; FIGS. 21 and 22).
[0133] Further, in order to improve adhesiveness between the outer
surface of the large diameter side end portion 410 and the
different thickness portion 560 (large thickness portion 560a and
small thickness portion 560b) corresponding to the secondarily
molded product, the convex-recess portions, not shown, formed
continuously in the circumferential direction with components
constituted alternately can be also adopted. Moreover, the convex
portion doubles as a part of the dam, whereby functions to flow the
thermoplastic resin 4a injected to the small thickness portion
molding space 770 from the pin gate 79 from the small thickness
portion molding space 770 to the large thickness portion molding
space 760 uniformly. Also, the convex-recess portions mentioned
above are the same components and the functional effects as with
the recess portion 57 and the convex portion 58 constituted in the
inner surface of the large diameter side end portion 41 in the
first embodiment.
[0134] Further, in accordance with the present embodiment, to have
no fear of grease leakage in the boot, it is better to position the
pin gate 79 in the large thickness portion molding space 760 rather
than the small thickness portion molding space 770.
[0135] Other conditions or the like may be set in accordance with
the first embodiment mentioned above.
[0136] Further, it is possible to further firmly weld the resin
bellows 800 corresponding to the primarily molded product to the
different thickness portion 560 corresponding to the secondarily
molded product by setting the injection condition of the
thermoplastic resin 4a into the secondary molding space 690 as
follows.
[0137] That is, a direction of the injection pin gate 79 is set
under a condition 0.degree..ltoreq..theta..ltoreq.90.degree., with
respect to the outer surface of the large diameter side end portion
410 of the resin bellows 800, a position condition of the injection
pin gate 79 is set to a condition 0.ltoreq.t.ltoreq.2a/3 in which a
distance between the outer surface of the large diameter side end
portion 410 of the resin bellows 800 and the injection pin gate 79
is set to t, and a diametrical distance of the injection side end
portion of the secondary molding space 690 is set to a.
[0138] Accordingly, the high temperature thermoplastic resin 4a is
injected so as to be brought into slidable contact with the outer
surface of the large diameter side end portion 410 of the resin
bellows 800, and the thermoplastic resin 4a is charged into the
secondary molding space 690.
[0139] At this time, since the injected high temperature
thermoplastic resin 4a flows so as to be brought into slidable
contact with the outer surface of the large diameter side end
portion 410 at a high speed, impurities attached on the surface of
the outer periphery of the large diameter side end portion are
washed out, and a heat of the thermoplastic resin 4a flowing at the
high temperature and high speed is transmitted to the surface of
the outer periphery, thereby melting the surface. Therefore, the
injected thermoplastic resin 4a is firmly welded to the surface of
the large diameter side end portion 410 which is melted by the heat
of the thermoplastic resin 4a, and the different thickness portion
560 is integ
* * * * *