Note: Descriptions are shown in the official language in which they were submitted.
CA 02488666 2004-11-30
- 1 -
BOOT FOR CONSTANT VELOCITY UNIVERSAL JOINT
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a boot for
protecting a constant velocity universal joint disposed,
for example, on a driving shaft (power transmission shaft)
or the like which transmits power to an axle hub from a
differential gear of an automobile, particularly to
prevention of damages of a boot by a sharp edge of an end
face portion of an outer housing of a constant velocity
universal joint.
Description of the Related Art
Constant velocity universal joints are used in
opposite end portions, for example, in a driving shaft for
an automobile. Moreover, a flexible boot is attached in
such a manner as to cover a bent portion of the constant
velocity universal joint in order to seal grease for
lubricating the constant velocity universal joint and to
prevent entrance of foreign matters such as dust and water
from the outside. Large and small end portions of the boot
are usually fastened and fixed to an outer peripheral
surface of an outer housing of the constant velocity
universal joint on a differential side or a hub side and an
outer peripheral surface of a driving shaft portion by
fastening means such as bands (see, e.g., page 1 and FIG. 1
CA 02488666 2004-11-30
- 2 -
of Japanese Patent Application Laid-Open No. 2002-39208).
Moreover, it is known that a surface portion
facing the end face of the tip portion of the outer housing
of the constant velocity universal joint is formed on the
large end portion of the boot on an inner peripheral side
in order to prevent the large end portion of the boot for
the constant velocity universal joint and the outer housing
of the constant velocity universal joint from being shifted
in an axial direction.
However, in the above-described boot for the
constant velocity universal joint, when the boot for the
constant velocity universal joint is bent accompanying a
stroke of a suspension or bend of the driving shaft caused
by a steering operation, the inner peripheral surface of
the boot contacting the end face of the tip portion of the
outer housing of the constant velocity universal joint is
pressed onto the tip portion of the outer housing of the
constant velocity universal joint, and a so-called "bite-
in" occurs in some case. When such bite-in occurs, the
boot needs to be prevented from being damaged by a sharp
edge or burr of the tip portion of the outer housing of the
constant velocity universal joint by machining.
SUMMARY OF THE INVENTION
The present invention has been developed in
consideration of the above-described problem, and an object
of the present invention is to prevent an inner surface of
CA 02488666 2004-11-30
- 3 -
a boot for a constant velocity universal joint from being
bitten by an edge portion of an outer housing of the
constant velocity universal joint.
To solve the above-described problem, according to
the present invention, there is provided a boot for a
constant velocity universal joint, comprising: a large end
portion into which an outer housing of the constant
velocity universal joint is inserted; a small end portion
into which a shaft portion connected to the constant
velocity universal joint is inserted; and bellows formed
between the large end portion and the small end portion,
the large end portion having a face portion facing the end
face of a tip portion of the outer housing of the constant
velocity universal joint, a portion facing an end face
inner peripheral portion of the tip portion of the outer
housing being dented to form the face portion.
According to the present invention, a gap is
formed between the inner surface of the boot for the
constant velocity universal joint and an inner peripheral
edge portion of the outer housing of the constant velocity
universal joint, on which a sharp edge or burr is easily
formed. Moreover, even when the boot is bent to a
predetermined maximum bend angle, a shape of the face
portion is appropriately set in such a manner as to prevent
the gap from being 0. Accordingly, the inner surface of
the boot can be prevented from being brought into contact
with the sharp edge regardless of the bend of the boot,
CA 02488666 2004-11-30
- 4 -
occurrence of the bite-in can be prevented, and the inner
surface of the boot for the constant velocity universal
joint can be prevented from being bitten by an edge portion
of the outer housing of the constant velocity universal
joint.
According to the present invention, the inner
surface of the boot for the constant velocity universal
joint can be prevented from being bitten by the edge
portion of the outer housing of the constant velocity
universal joint.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a vertical sectional view of one
embodiment of a boot for a constant velocity universal
joint, to which the present invention is applied;
FIG. 2 is an enlarged sectional view at a time
when an outer housing of the constant velocity universal
joint is inserted into a large end portion of the boot for
the constant velocity universal joint of FIG. l;
FIG. 3 is a diagram showing that the boot is bent
in a state in which the outer housing of the constant
velocity universal joint is inserted into the large end
portion of the boot for the constant velocity universal
joint of FIG. 1; and
FIG. 4 is an enlarged sectional view of a part IV
of FIG. 3.
CA 02488666 2004-11-30
- 5 -
DESCRIPTION OF THE PREFERRED EMBODIMENT
One embodiment of a boot for a constant velocity
universal joint, to which the present invention is applied,
will be described hereinafter. FIG. 1 is an elevation view
showing an appearance of a boot for a constant velocity
universal joint of the present embodiment. As shown in FIG.
l, a boot 1 is formed into a cylindrical shape, and has a
large end portion 3 fixed to a constant velocity universal
joint side, and a small end portion 5 fixed to a shaft
portion side of a driving shaft connected to this constant
velocity universal joint. Moreover, bellows 7 having
flexibility and constituted to be bendable are formed
between the large end portion 3 and the small end portion 5.
It is to be noted that in the present embodiment, the boot
1 is formed of a resin having elasticity, such as
thermoplastic polyester-based elastomer.
The bellows 7 are constituted by repeatedly
arranging convex portions 7a and concave portions 7b
extending in a peripheral direction in a cylinder shaft
direction of the boot l, that is, in a vertical direction
in FIG. 1. That is, a cross section of the bellows 7 is
convex on an outer peripheral side in the convex portion 7a,
and that of the bellows 7 is convex on an inner peripheral
side in the concave portion 7b. In the present embodiment,
for example, five convex portions 7a are disposed, and the
corresponding concave portion 7b is disposed on a large end
portion 3 side of each convex portion 7a. Moreover,
CA 02488666 2004-11-30
- 6 -
diameters of each convex portion 7a and concave portion 7b
are set to be large toward the large end portion 3 from a
small end portion 5 side. As a result, the bellows 7 are
entirely formed into substantially conical shape.
A face portion 9 formed into a substantially
constant outer diameter is disposed over a shaft direction
in a side-portion outer peripheral surface of the large end
portion 3. A band (not shown) for fastening the boot 1 to
the outer peripheral surface portion of the outer housing
of a tripod joint (not shown) which is a constant velocity
universal joint is attached to the face portion 9. It is
to be noted that the tripod joint is one type of constant
velocity universal joint, rollers arranged in a trifurcate
lock are disposed around a shaft, and a groove portion in
which these rollers slide is formed in a casing or outer
housing on an inner peripheral side. A stepped portion 11
for preventing the band from being shifted in an axial
direction is formed on the end of the face portion 9 on the
small end portion 5 side of the boot 1 in a cylindrical
axial direction.
FIG. 2 is an enlarged sectional view showing that
an outer cylinder 13 of the constant velocity universal
joint is inserted in the large end portion 3 of the
constant velocity universal joint boot 1 of the present
embodiment. A tip portion 15 of the outer housing 13 of
the constant velocity universal joint on an insertion side
into the large end portion 3 is formed into a cylindrical
CA 02488666 2004-11-30
_ 7 -
shape, and concave portions which are characteristics of
the tripod joint are formed in three portions on a
circumference. Moreover, an inner peripheral surface 17 of
the tip portion 15 is formed into a constant inner diameter
over a cylindrical shaft direction excluding the above-
described inner surface of the concave portion. On the
other hand, the tip portion 15 has an annular end face 19
directed on the side of the small end portion 5 of the boot
1 in the cylindrical axial direction. Moreover, a portion
21 tapered toward its point is formed from the outer
peripheral edge portion of the end face 19 to the side
surface of the tip portion 15. A boundary portion between
the end face 19 and the tapered portion 21 is subjected to
R-chamfering. Further behind the tapered portion 21, that
is, on the left side of FIG. 2 as faced, a parallel portion
23 having a constant outer diameter, a tapered portion 25
whose outer diameter is gradually reduced toward a rear
side, and a parallel portion 27 whose outer diameter is set
to be substantially equal to that of a rear end portion of
the tapered portion 25 are formed in order from a tip side.
On the other hand, as shown in FIG. 2, face
portions having shapes adapted to those of the above-
described end face 19, tapered portion 21, parallel portion
23, tapered portion 25, and parallel portion 27 are also
formed on the inner surface of the large end portion 3 of
the boot 1. A diameter of an inner peripheral edge portion
of an annular face portion 31 of the boot 1 facing the end
CA 02488666 2004-11-30
face 19 of the outer housing 13 of the constant velocity
universal joint, a diameter of an inner peripheral edge
portion, or a diameter of a smallest diameter portion 33 is
formed to be larger than a minimum diameter of the end face
19 of the outer housing 13. Moreover, an annular concave
face portion 34 formed in such a manner as to be dented on
the small end portion 5 side from the annular face portion
31 in the cylindrical axial direction of the boot 1 is
formed in a region of the inner surface of the boot 1 on
the inner peripheral side from the annular face portion 31.
As shown in FIG. 2, the concave face portion 34 is formed
into a concave shape having a circular sectional shape. A
boundary portion of the concave face portion 34 contacting
the annular face portion 31 is formed into an edge portion
having an angle. For example, in the boundary portion
between the annular face portion 31 and the concave face
portion 34, opposite faces have an angle, for example, of
about 45 degrees. On the other hand, an innermost
peripheral portion of the concave face portion 34 is formed
into a tapered shape having a slight tilt with respect to a
face crossing a cylindrical axis of the boot 1 at right
angles. Since the concave face portion 34 is formed, a
release portion 35 which is an annular gap is formed
between the end face 19 of the outer housing 13 of the
constant velocity universal joint and the concave face
portion 34.
As shown in FIG. 2, a region of the inner surface
CA 02488666 2004-11-30
- 9 -
of the boot 1 on the inner peripheral side from the inner
peripheral edge of the concave face portion 34 is formed
into a convex surface having a circular sectional shape,
and contacts the inner peripheral surface of the bellows 7
via a stepped portion 39 formed by increasing the diameter
of the convex surface portion in a stepwise manner from an
inner peripheral edge portion 37.
FIG. 3 is a sectional view showing that the
bellows 7 are bent in a state in which the outer housing 13
of the constant velocity universal joint is inserted into
the large end portion 3 of the boot 1 for the constant
velocity universal joint according to the present
embodiment. It is to be noted that this view shows a state
in which the axial direction of the large end portion 3 is
fixed, and the axial direction of the small end portion 5
is shifted clockwise as facing FIG. 3. Moreover, an angle
formed by the axial directions of the small end portion 5
and the large end portion 3 is a maximum bend angle of the
constant velocity universal joint, for example, to which
the constant velocity universal joint boot of the present
embodiment is attached. FIG. 4 is an enlarged sectional
view of part IV of FIG. 3. It is to be noted that in FIG.
4, a contour line of the boot 1 before bent is shown by a
broken line for reference. As shown in FIG. 4, also in
this state, an interval between the concave face portion 34
which is the inner surface of the large end portion 3 of
the boot l, and the end face 19 of the outer housing 13 of
CA 02488666 2004-11-30
- 10 -
the constant velocity universal joint is smaller than that
in a state shown in FIG. 2, but the concave face portion
faces the end face at the interval without contacting the
end face. It is to be noted that, as shown in FIG. 4, a
diameter r1 of a maximum diameter portion of the concave
face portion 34 is set to be larger than an inner diameter
r2 of the end face 19.
As described above, according to the present
embodiment, the release portion 35 which is a space portion
is formed between the inner surface of the constant
velocity universal joint boot l, and an inner peripheral
edge portion 36 of the end face 19 of the outer housing 13
of the constant velocity universal joint on which the sharp
edge or burr is easily formed. Moreover, the concave face
portion 34 is formed in such a manner as to prevent the
interval of the release portion 35 from being 0 even when
the boot 1 is bent at a predetermined maximum bend angle.
Therefore, the inner surface 34 or the like of the boot 1
can be prevented from being brought into contact with the
inner peripheral edge portion 36 of the end face 19
regardless of the bend of the boot 1, and the inner surface
of the constant velocity universal joint boot 1 can be
prevented from being bitten by the edge portion of the
outer housing 13 of the constant velocity universal joint.
It is to be noted that the present invention is
not limited to the above-described embodiment, and can be
appropriately modified in the scope of the present
CA 02488666 2004-11-30
- 11
invention. For example, the shape of the outer housing of
the constant velocity universal joint, or the shape of the
large end portion may be modified. The shapes of the
bellows and the small end portion may be appropriately
modified. Furthermore, in the present embodiment, the boot
is formed of a resin. For example, a grommet portion of
the large end portion on the inner peripheral side may be
separately formed of a resin or rubber having a hardness
lower than that of a resin of the boot main body. The
whole boot may be integrally formed only of the resin or
rubber having low hardness.
