Title: Tripod type constant velocity universal joint
Abstract: A tripod type constant velocity universal joint of a single roller type is provided, which can be used in a vehicle operating at high angles without causing an increase in costs by lowering the level of vibration even at a high operating angle. A tripod type constant velocity universal joint is composed of an outer joint member with three track grooves, extending in its axial direction, on the inner circumferential surface of the outer joint member, a tripod member with three radially projecting leg shafts around the circumference of the tripod member, and rotatable rollers mounted on each leg shaft through a plurality of needle rollers and positioned in the track grooves of the outer joint member, the outer circumferential surfaces of the rollers being guided by roller guide surfaces provided on both sides of the track grooves. In this construction, grooves extending along the track grooves are provided on the roller guide surfaces where the rollers contact.
Patent Number: 6,893,351 Issued on 05/17/2005 to Ishiguro, et al.
| Inventors:
|
Ishiguro; Shigeyoshi (Shizuoka-ken, JP);
Sugiyama; Tatsuro (Shizuoka-ken, JP);
Nagatani; Haruo (Shizuoka-ken, JP)
|
| Assignee:
|
NTN Corporation (Osaka, JP)
|
| Appl. No.:
|
907967 |
| Filed:
|
July 19, 2001 |
Foreign Application Priority Data
| Aug 11, 2000[JP] | 2000-244462 |
| Current U.S. Class: |
464/111; 464/124; 464/905 |
| Intern'l Class: |
F16D 003/20.5 |
| Field of Search: |
464/111,124,120,122,123,132,905,11,115,121
403/125,126,133,135
384/49
|
References Cited [Referenced By]
U.S. Patent Documents
| 4167860 | Sep., 1979 | Sakaguchi et al.
| |
| 4810232 | Mar., 1989 | Farrell et al.
| |
| 5391013 | Feb., 1995 | Ricks et al.
| |
| 5474500 | Dec., 1995 | Girguis.
| |
| 5989124 | Nov., 1999 | Goto et al.
| |
| 6010420 | Jan., 2000 | Niki et al.
| |
| 6322453 | Nov., 2001 | Ishiguro et al.
| |
| Foreign Patent Documents |
| 39 36 603 | May., 1991 | DE.
| |
| 2 586 767 | Sep., 1986 | FR.
| |
| 2 672 092 | Jan., 1992 | FR.
| |
Primary Examiner: Thompson; Kenneth
Attorney, Agent or Firm: Arent Fox PLLC
Claims
1. A tripod type constant velocity universal joint comprising:
an outer joint member having three track grooves extending in its axial direction
of the outer joint member and on an inner circumference surface of the outer joint
member;
a tripod member having three radially projecting leg shafts around a circumference
of the tripod member; and
rotatable rollers mounted on each leg shaft through a plurality of needle rollers
and positioned in the track grooves of the outer joint member,
wherein outer circumferential surfaces of the rollers are guided by roller guide
surfaces provided on both sides of the track grooves,
wherein grooves are provided on the roller guide surfaces at a pair of contact
points where the rollers contact the roller guide surfaces and extend in a direction
orthogonal relative to a longitudinal axis of each rotatable roller, and
wherein the contact points are disposed intermediate the outer circumferential
surfaces of the rollers.
2. The tripod type constant velocity universal joint according to claim 1, wherein
at least one additional groove is provided on the roller guide surfaces between
the pair of contact points where the rollers contact the roller guide surfaces.
3. The tripod type constant velocity universal joint according to claim 2, wherein
the outer circumferential surface of the roller is formed in a spherical shape,
and the outer circumferential surface of the roller in cross section forms an arc
shape with its center of curvature shifted radially outward from the axis of the roller.
4. The tripod type constant velocity universal joint according to 2, wherein
there are dual angular contact points between the roller guide surface and the roller.
5. The tripod type constant velocity universal joint according to claim 2, wherein
the outer circumferential surface of the leg shaft is crowned and a ratio R/d of
the crowning R to an outer diameter d of the leg shaft is in a range of 5.0 to 39.3.
6. The tripod type constant velocity universal joint according to claim 2, wherein
the inner circumferential surface of the roller is crowned and a ratio R/D of the
crowning R to an inner diameter D of the roller shaft is in a range of 2.2 to 35.2.
7. The tripod type constant velocity universal joint according to 2, wherein
the outer circumference of the leg shaft is formed in an elliptical cylinder.
8. The tripod type constant velocity universal joint according to 2, wherein
the surfaces of the ends of the needle rollers are formed in a convex shape.
9. The tripod constant velocity universal joint according to 2, wherein the grooves
provided on the roller guide surfaces define pockets for grease supplied inside
the constant velocity universal joint.
10. A tripod type constant velocity universal joint comprising:
an outer joint member having three track grooves extending in an axial direction
of the outer joint member and on an inner circumference surface of the outer joint
member;
a tripod member having three radially projecting leg shafts around a circumference
of the tripod member; and
rotatable rollers mounted on each leg shaft through a plurality of needle rollers
and positioned in the track grooves of the outer joint member,
wherein outer circumferential surfaces of the rollers are guided by roller guide
surfaces provided on both sides of the track grooves, and
wherein grooves are provided on the roller guide surfaces at a pair of contact
points where the rollers contact the roller guide surfaces and extend in a direction
orthogonal relative to a longitudinal axis of each rotatable roller,
wherein the outer circumferential surface of the leg shaft is crowned and a ratio
R/d of the crowning R to an outer diameter d of the leg shaft is in a range of
5.0 to 39.3.
11. The tripod type constant velocity universal joint according to claim 10,
wherein the outer circumferential surface of the roller is formed in a spherical
shape, and the outer circumferential surface of the roller in cross section forms
an arc shape with its center of curvature shifted radially outward from the axis
of the roller.
12. The tripod type constant velocity universal joint according to claim 10,
wherein there are dual angular contact points between the roller guide surface
and the roller.
13. The tripod type constant velocity universal joint according to claim 10,
wherein the inner circumferential surface of the roller is crowned and a ratio
R/D of the crowning R to an inner diameter D of the roller shaft is in a range
of 2.2 to 35.2.
14. The tripod type constant velocity universal joint according to claim 10,
wherein the outer circumference of the leg shaft is formed in an elliptical cylinder.
15. The tripod type constant velocity universal joint according to claim 10,
wherein the surfaces of the ends of the needle rollers are formed in a convex shape.
16. The tripod constant velocity universal joint according to claim 10, wherein
the grooves provided on the roller guide surfaces define pockets for grease supplied
inside the constant velocity universal joint.
17. A tripod type constant velocity universal joint comprising:
an outer joint member having three track grooves extending in an axial direction
of the outer joint member and on an inner circumference surface of the outer joint
member;
a tripod member having three radially projecting leg shafts around a circumference
of the tripod member; and
rotatable rollers mounted on each leg shaft through a plurality of needle rollers
and positioned in the track grooves of the outer joint member,
wherein outer circumferential surfaces of the rollers are guided by roller guide
surfaces provided on both sides of the track grooves, and
wherein grooves are provided on the roller guide surfaces at a pair of contact
points where the rollers contact the roller guide surfaces and extend in a direction
orthogonal relative to a longitudinal axis of each rotatable roller,
wherein the inner circumferential surface of the roller is crowned and a ratio
R/D of the crowning R to an inner diameter D of the roller shaft is in a range
of 2.2 to 35.2.
18. The tripod type constant velocity universal joint according to claim 17,
wherein the outer circumferential surface of the roller is formed in a spherical
shape, and the outer circumferential surface of the roller in cross section forms
an arc shape with its center of curvature shifted radially outward from the axis
of the roller.
19. The tripod type constant velocity universal joint according to claim 17,
wherein there are dual angular contact points between the roller guide surface
and the roller.
20. The tripod type constant velocity universal joint according to claim 17,
wherein the outer circumference of the leg shaft is formed in an elliptical cylinder.
21. The tripod type constant velocity universal joint according to claim 17,
wherein the surfaces of the ends of the needle rollers are formed in a convex shape.
22. The tripod constant velocity universal joint according to claim 17, wherein
the grooves provided on the roller guide surfaces define pockets for grease supplied
inside the constant velocity universal joint.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tripod type constant velocity universal joint
used in a power transmitting section of automobiles, aircraft, ships, and industrial machinery.
2. Description of the Related Art
For example, among constant velocity universal joints used as means for transmitting
a rotational power of an automobile engine to its wheels at a constant speed is
a tripod type constant velocity joint. This tripod type constant velocity universal
joint connects a driving side shaft and a driven side shaft together and can transmit
a rotational torque between them at a constant velocity even if there is an operating
angle between them. The tripod type constant velocity universal joint even permits
a relative displacement in an axial direction.
FIG.
15 and FIG. 16 show a fundamental structure of a tripod type constant
velocity universal joint. This constant velocity universal joint is composed of,
as essential structural members, a tripod member
2 with three radially projecting
leg shafts
1, an outer joint member
5 with three axially extending
track grooves
3 formed on the inner circumferential surface of the outer
joint member, and rollers
7. Each of the track grooves
3 has at both
sides axially extending roller guide surfaces
4. The rollers
7 are
mounted on the leg shafts
1 of the tripod member
2 through a plurality
of needle rollers
6 and positioned in the track grooves
3 of the
outer joint member. The rollers
7 are guided on their external circumferential
surfaces by the roller guide surfaces
4 provided at the both sides of the
track grooves.
The tripod member
2 is fitted over a serration part (or spline part) formed
on an end part of the other shaft, not shown, and is secured. As shown in FIG.
17, a plurality of the needle rollers
6 are arranged, so that they can rotate,
on an outer circumferential surface of the leg shaft
1 of the tripod member
2. The needle rollers
6 are limited with respect to their displacement
on the leg shaft
1 in the axial direction by washers
8 and
9
installed at the base and top parts of the leg shaft
1, and a retaining
ring
10 secured at the top part of the leg shaft
1. The outer circumferential
surface of the leg shaft
1 of the tripod member
2 has a cylindrical
shape, and rollers
7 are fitted over the outer circumferential surface of
the leg shaft
1 through the needle rollers
6 so that they can rotate.
The inner circumferential surface of the roller
7 has a cylindrical shape
and the outer surface thereof has a genuine partial sphere shape.
The outer joint member
5 forms a cylindrical cup with one end open and
the other end closed, with the other shaft, not shown, being integrally provided
at the other end of the outer joint member. Three axial track grooves
3
are formed on the circumference around a center shaft at intervals of 120 degrees
on the inner circumferential surface of the outer joint member
5. At both
sides of each track groove
3 are the two roller guide surfaces
4,
and, as shown in FIG. 18, the roller guide surface
4 makes angular contact
with the roller
7 at two points A and B. This is done by forming the roller
guide surface
4 in the shape of a gothic arch.
In this tripod type constant velocity universal joint, power is transmitted by
the connection between the roller guide surfaces
4 of the outer joint member
5 and the rollers
7 of the tripod member
2. The rollers
7
absorb plunging by rotating along the roller guide surfaces
4. In the case
of power transmission when the axis of the outer joint member
5 and the
axis of the tripod member
2 are aligned, or an operating angle is 0 degree,
the point of intersection of the axes of each leg shaft
1 is located on
the axis of the outer joint member
5. In this way the rollers
7 rotate
while maintaining dual contact points with the roller guide surfaces
4.
When there is an operating angle, although the magnitude of the contact force fluctuates
depending on the rotational phase, the operation of the tripod type constant velocity
universal joint is stable because the rollers and the roller guide surfaces
4
are always in contact with each other at the two points A and B.
The tripod type constant velocity universal joint described above is a sliding
type in which relative displacement, caused by plunging, between the two shafts
in the axial direction is allowed. Torque is transmitted by connecting the tripod
member
2 with one shaft, connecting the outer joint member
5 with
the other shaft, and positioning the leg shafts
1 of the tripod member
2
in the track grooves
3 of the outer joint member
5. In this construction,
the tripod member
2 is provided with the three leg shafts
1 projecting
in an axial direction, and the outer joint member
5 is provided with the
three track grooves
3 extending in the axial direction.
In this tripod type constant velocity universal joint, because the roller
7
and the roller guide surface
4 are in angular contact at the points A and
B, and the roller
7 does not contact with the center part and both sides
of the roller guide surface
4, a strong edge load is not created, the needle
rollers
6 do not become skew, and friction resistance does not increase.
Furthermore, because of lower eccentric load, rotational moment caused in the roller
7 acting at a right angle to the leg shaft
1 around the axis thereof
can be decreased, and frictional force and induced thrust that cause vibration
can be reduced. Also, movement in the axial direction when transmitting rotational
torque with an operating angle becomes smooth, so that induced thrust is reduced.
However, conventional tripod type constant velocity universal joints are
usually mounted on vehicles operating at low angles, for example equal to or less
than 4 degrees, and for vehicles operating at high angles, for example equal to
or more than 7 degrees, tripod type constant velocity universal joints of a double
roller type are used taking into consideration a higher level of vibration in such
applications. The conventional tripod type constant velocity universal joints described
above correspond to a single roller type.
A tripod type constant velocity universal joint of a double roller type is provided
with a roller assembly each contained as a unit. The roller assembly is composed
of a circular inner roller which is fitted over the outer circumferential surface
of a leg shaft, and an outer roller positioned within the track groove which rotates
in the axial direction of an outer joint member. Needle rollers are interposed
between the inner and outer rollers. Within the roller assembly the inner and outer
rollers are individually rotatable.
In this tripod type constant velocity universal joint, the roller assembly composed
of the inner and outer rollers can swing freely with respect to the leg shaft.
Therefore, when transmitting a rotational force at a high operating angle between
the outer joint member and the tripod member, the roller assembly can rotate only
in the axial direction of the outer joint member, and the vibration inducing force
of the outer joint member can be absorbed by the rotation of the needle rollers,
so that sliding resistance can be reduced. Furthermore, the moment acting to incline
the roller assembly during operation becomes smaller, the roller assembly can maintain
its posture, resistance between the outer joint member and the roller assembly
during rotation becomes smaller, and induced thrust can be reduced.
However, because a tripod type constant velocity universal joint of a double
roller type has a structure provided with the roller assemblies composed of inner
and outer rollers, using a tripod type constant velocity universal joint of this
type in a vehicle which operates at a low angle causes the cost to increase.
SUMMARY OF THE INVENTION
An object of the present invention is to enable the use of a tripod type constant
velocity universal joint in vehicles operating at high angles, without causing
an increase in costs, by reducing the level of vibration even at high operating angles.
A tripod type constant velocity universal joint in accordance with the present
invention is composed of an outer joint member with three track grooves, which
extend in its axial direction around the circumference, on the inner surface of
the outer joint member, and a tripod member with three radially projecting leg
shafts around the circumference of the tripod member. Rollers are mounted on each
leg shaft, so that they can rotate, through a plurality of needle rollers, and
positioned in the track grooves of the outer joint member. The rollers are guided
at their outer circumferential surfaces by roller guide surfaces provided on both
sides of the track grooves. In this construction, grooves extending along the track
grooves are formed on the roller guide surfaces at the points where the rollers contact.
In a tripod type constant velocity universal joint in accordance with the present
invention, because the grooves extending along the track grooves are formed on
the roller guide surfaces at the points where the rollers contact, the grooves
formed on the roller guide surfaces function as pockets for grease supplied inside
the constant velocity universal joint. By the grease in the pockets improves the
lubrication, the sliding resistance and induced thrust between the roller guide
surfaces and the rollers are reduced, so that the level of vibration is lowered.
As a result, the level of vibration can be reduced in a tripod type constant velocity
universal joint of a single roller type even when operating at high angles. In
this way it becomes possible to use the joint in a vehicle operating at high angles
without causing an increase in costs.
To achieve this lowered level of vibration, it is preferable that the following
are added to the structure of the tripod type constant velocity universal joint:
1. Clearance between the outer circumferential surface of the roller and the
track
groove is widened by an amount equal to a reduction in the clearance caused by
inclination of the roller. The widening is achieved by making the outer circumferential
surface of the roller in a spherical shape, and making the outer circumferential
surface of the roller in cross section an arc shape with its center of curvature
shifted radially outward from the axis of the roller.
2. The roller guide surface and the roller are in angular contact at two points.
3. The outer circumferential surface of the leg shaft is crowned.
4. The inner circumferential surface of the roller is crowned.
5. The outer circumferential surface of the leg shaft is formed in an elliptical
cylinder shape in the embodiments of FIG. 1 and FIG. 3.
6. The ends of the needle roller are formed in a convex shape.
The nature, principle, and utility of the invention will become more apparent
from the following detailed description when read in conjunction with the accompanying
drawings in which like parts are designated by like reference numerals or characters.
BRIEF EXPLANATION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 shows a cross sectional view of a tripod type constant velocity universal
joint in accordance with an embodiment of the present invention with oil grooves
formed on roller guide surfaces;
FIG. 2 is an enlarged cross sectional view of an essential part showing a roller
and a roller guide surface of the embodiment presented in FIG. 1;
FIG. 3 shows a cross sectional view of a tripod type constant velocity universal
joint in accordance with another embodiment of the present invention with roller
guide surfaces in cross section forming a polygon shape;
FIG. 4 is an enlarged cross sectional view of an essential part showing a roller
and a roller guide surface of the embodiment presented in FIG. 3;
FIG. 5 is a characteristics diagram showing the relationship between induced
thrust and operating angles;
FIG. 6 is another embodiment of the present invention, showing a tripod type
constant velocity universal joint with the outer circumferential surfaces of the
leg shafts and inner circumferential surfaces of the rollers crowned, and both
ends of the needle rollers formed in a convex shape;
FIG. 7 is an enlarged cross sectional view of an essential part showing a leg
shaft, a needle roller and a roller of the embodiment in FIG. 6;
FIG. 8 is a characteristics diagram showing the relationship of induced thrust
relative to operating angle presented in the embodiment in FIG. 6;
FIG. 9 is still another embodiment of the present invention, showing a tripod
type constant velocity universal joint, wherein the outer circumferential surface
of a roller in cross section forms an arc shape with the center of curvature shifted
radially outward from the axis of the roller;
FIG. 10 is a cross sectional side view of the tripod type constant velocity
universal joint in the embodiment in FIG. 9, showing a state in which the roller
is inclined in the axial direction of an outer joint member;
FIG. 11 is a further embodiment of the present invention showing a cross sectional
view of a tripod type constant speed universal joint, in which the outer circumferential
surface of the roller in cross section forms an arc shape with the center of curvature
thereof shifted radially outward from the axis of the roller, the outer circumferential
surface is formed in an elliptical cylinder, and the outer circumferential surface
of the leg shaft and inner circumferential surface of the roller are crowned;
FIG. 12 is a cross sectional side view of the tripod type constant velocity
universal joint in the embodiment in FIG. 11, showing a state in which the roller
is inclined in the axial direction of an outer joint member;
FIG. 13 is an enlarged cross sectional view of an essential part showing the
leg shaft, the outer surface of which forms an elliptical cylinder, the needle
rollers, and the inner surface of the roller of the embodiment shown in FIG. 11;
FIG. 14 is a characteristics diagram showing the relationship between the induced
thrust and the operating angle in the embodiments of FIG.9 and FIG. 10,
and FIG. 11 to FIG. 13;
FIG. 15 is a cross sectional view showing a conventional tripod type constant
velocity universal joint;
FIG. 16 is a cross sectional side view of the conventional tripod type constant
velocity universal joint presented in FIG. 15;
FIG. 17 is an enlarged cross sectional view of an essential part of the conventional
tripod type constant velocity universal joint in FIG. 15, showing a leg shaft,
a needle roller, and a roller; and
FIG. 18 is an enlarged cross sectional view of an essential part of the conventional
tripod type constant velocity universal joint in FIG. 15, showing a roller and
a roller guide surface.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An embodiment shown in FIG. 1 is a tripod type constant velocity universal joint
of a single roller type. This constant velocity universal joint is composed of,
as essential structural members, a tripod member
12 with three radially
extending leg shafts
11, an outer joint member
15 with three axially
extending track grooves
13 formed on the inner circumferential surface of
the outer joint member, and rollers
17. Each of the track groove
13
have, at both sides, axially extending roller guide surfaces
14. The rollers
17 are mounted on the leg shafts
11 of the tripod member
12
through a plurality of needle rollers
16 and positioned in the track grooves
13 of the outer joint member
15. The rollers
17 are guided
on their external circumferential surfaces by the roller guide surfaces
14
provided at both sides of each of the track grooves.
The tripod member
12 is fitted over a serration part (or spline part)
formed on an end part of the other shaft, not shown, and is secured. A plurality
of the needle rollers
16 are mounted on the circumferential surface of the
leg shaft
11 of the tripod member
12 so that they can rotate. The
displacement of the needle rollers
16 on the leg shaft
11 is limited
in an axial direction by washers
18 and
19, installed at a base and
top part of the leg shaft
11, and retaining ring
20 installed on
a top part of the leg shaft
11.
The outer joint member
15 forms a substantial cylindrical cup with one
end open and the other end closed. The other shaft, not shown, is integrally provided
at the other end of the outer joint member, and three axial track grooves
13
are formed on the circumference around a center shaft at intervals of 120 degrees.
At the both sides of each track groove
13 are the two roller guide surfaces
14, and, as shown in FIG. 2, the roller guide surface is in angular contact
with the roller
17 at two points C and D by forming the roller guide surface
14 in the shape of a gothic arch.
In this tripod type constant velocity universal joint, power is transmitted by
the connection of the roller guide surfaces
14 of the outer joint member
15 with the rollers
17 of the tripod member
12. The rollers
17 absorb plunging by rotating along the roller guide surfaces
14.
In the case of transmission when the axis of the outer joint member
15
and the axis of the tripod member
12 are aligned, or when an operating angle
is 0 degrees, the point of intersection of the axes of each leg shaft
11
is located on the axis of the outer joint member
15. In this way the rollers
17 rotate while maintaining dual contact points with the roller guide surfaces
14. When there is an operating angle, although the magnitude of the contact
force fluctuates depending on the rotational phase, the operation of the tripod
type constant velocity universal joint is stable because the rollers
17
and the roller guide surfaces
14 are always in contact with each other at
the two points C and D. In this embodiment, grooves
21 and
22 extending
along the track grooves
13 are formed on the two contact points C and D
on the roller guide surface that is in contact with the roller
17, and at
the same time a groove
23 extending along each of the track grooves
13
is formed on the intermediate part between the contact points C and D.
The grooves
21 to
23 formed on the roller guide surface
14
function as pockets for grease supplied inside the constant velocity universal
joint. The grease in the pockets improves the lubrication and consequently the
induced thrust can be reduced. The term "induced thrust" means thrust force produced
by friction inside a constant velocity universal joint when torque is applied to
this joint rotating at a certain operating angle. In a tripod type joint induced
thrust appears mainly as a strong tertiary component.
In the embodiment shown in FIG.
1 and FIG. 2, the roller guide surface
14 is provided with the grooves
21 to
23. However, a structure
shown in FIG.
3 and FIG. 4 is also possible. In the embodiment shown in
FIG.
3 and FIG. 4, a roller guide surface
14′ in cross section
forms a polygon shape and the roller
17 makes contact with the roller guide
surface at the four points E to H. Clearance formed between each of the four contact
points E to H serves, in the same way as the grooves of
21 to
23
described above, as pockets for grease supplied inside the constant velocity universal joint.
In the embodiments shown in FIG. 1 to FIG. 4, when a conventional type and an
improved type (in accordance with the embodiments) are compared as shown in FIG.
5, the improved type has less induced thrust than the conventional type even with
larger operating angles. Consequently the improved type can be used for vehicles
operating at higher angles.
FIG.
6 and FIG. 7 show an embodiment in which an outer circumferential
surface
24 of the leg shaft
11′ of the tripod member
12
and on an inner circumferential surface
25 of a roller
17′
are crowned.
Crowning the outer circumferential surface
24 of the leg shaft
11′
and the inner circumferential surface
25 of the roller
17′
increases mutual freedom of movement of the leg shaft
11′ and the
roller
17′ (needle rollers
16′ exist between the two)
so that the level of vibration can be reduced. This means that the roller
17′
is in parallel with track groove
13 as much as possible when it moves, with
a reduced inclination, even when there is an operating angle, and as a result the
level of vibration can be reduced.
In the embodiment shown in FIG.
6 and FIG. 7, both the outer circumferential
surface
24 of the leg shaft
11′ and inner circumferential
surface
25 of the roller
17′ are crowned. However, a reduction
in the level of vibration can be obtained by crowning either of the outer circumferential
surface
24 of the leg shaft
11′ or the inner circumferential
surface
25 of the roller
17′.
Crowning in the range R
89 to R
700 on the outer circumferential
surface
24 of the leg shaft
11′ is preferred, and in the range
R
50 to R
800 on the inner circumferential surface
25 of the
roller
17′ is preferred. Crowning below R
89 and R
50
causes the surface pressure to become too high, which causes a shorter lifetime
of the joint in a load endurance test and lowers durability. Contrary to this,
when the crowning is larger than R
700 and R
800 it becomes difficult
to obtain a reduction in induced thrust. This means that a reduction of 5% or less
in induced thrust is only within an allowance, and the desired reduction cannot
be obtained.
In the preferred crowning range on the outer circumferential surface
24
of the leg shaft
11′, which is from R
89 to R
700, the
ratio of the crowning R to the outer diameter d of the leg shaft
11′
becomes R/d=5.0 to 39.3. In the preferred crowning range on the inner circumferential
surface
25 of the roller
17′, which is from R
50 to
R
800, the ratio of the crowning R to the inner diameter D of the roller
17′ becomes R/d=2.2 to 35.2.
In order to further reduce the level of vibration, it is preferable that the
ends
26 of needle rollers
16′, provided between the roller guide
surface
14 and the roller
17′, are formed in a convex shape.
A convex shape on the ends
26 of the needle rollers
16′ helps
reduce sliding resistance and induced thrust. The term "sliding resistance" means
the magnitude of axial friction force that occurs when an outer joint member and
a shaft mutually slide in a sliding type joint such as a tripod type constant velocity joint.
In the embodiments shown in FIG.
6 and FIG. 7, as shown in FIG. 8, when
a conventional type and a improved type (in accordance with the embodiments) are
compared, the improved type has less induced thrust than the conventional type
even with a higher operating angle so that the improved type can be used for vehicles
operating at higher angles.
FIG.
9 and FIG. 10 show an embodiment in which the outer circumferential
surface of a roller
17″ in cross section forms an arc shape and the
centers of curvature O
1 and O
2 are shifted radially outward
from an axis O of the roller
17″. FIGS. 11 to
13 show an embodiment
in which the outer circumferential surface of roller
17″ in cross
section forms an arc shape with the centers of curvature O
1 and O
2
shifted radially outward from the axis O of the roller, and furthermore,
the outer surface of the leg shaft
11′ in cross section forms an
elliptical cylinder. The outer circumferential surface of the leg shaft
1l′
and the inner circumferential surface of the roller
17″ are crowned.
In the tripod type constant velocity universal joint of this embodiment, by forming
the roller
17″ with the outer circumferential surface in an arc cross
section with the centers of curvature O
1 and O
2 shifted radially,
outward from the axis O of the roller, the force suppressing the inclination of
the roller
17″ is increased. This means that the roller
17″
is in parallel with the track groove
13 as much as possible when it moves,
with a reduced inclination, even when there is an operating angle, and as a result
the level of vibration can be reduced.
Making the leg shaft
11′ in an elliptical cylinder and crowning
the outer circumferential surface of the leg shaft
11′ and the inner
circumferential surface of the roller
17″, enables a swinging motion
of the roller
17″ on the leg shaft
11′ in the axial
direction of the leg shaft. Thereby, the roller
17″ is in parallel
with track groove
13 as much as possible when it moves, with a reduced inclination,
even when there is an operating angle, and as a result the level of vibration can
be further reduced.
When the roller
17″ is inclined in the axial direction of the
leg shaft
11″, a contact angle between the roller
17″
and the roller guide surface
14 varies and a track clearance becomes smaller.
Therefore, it is preferable that, like this embodiment, the outer circumferential
surface of the roller
17″ in cross section forms an arc shape with
the centers of curvature O
1 and O
2 of the outer circumferential
surface shifted radially outward from the axis O of the roller. At the same time,
the roller guide surface
14 is formed in a shape in which a track clearance
can be secured between the track groove
13 and the roller guide surface
14 even when the roller
17″ is inclined at a maximum operating angle.
By doing this, freedom of movement of the roller
17″ relative to
the roller guide surface
14 is increased and the level of vibration is further reduced.
In the embodiment shown in FIG.
9 and FIG. 10, and the embodiment in FIG.
11 to
13, when a conventional type and improved types (in accordance with
the embodiments) are compared as shown in FIG. 14, the improved types have less
induced thrust than the conventional type even at larger operating angles so that
the improved types can be used for vehicles operating at higher angles.
While there has been described what are at present considered to be preferred
embodiments of the invention, it will be understood that various modifications
may be made thereto, and it is intended that the appended claims cover all such
modifications as fall within the true spirit and scope of the invention.
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