Wheel drive unit

Details Wheel drive unit Wheel drive unit

2001-08-16

2004-10-05

Binda, Greg (Department: 3679)

Rotary shafts, gudgeons, housings, and flexible couplings for ro

Housing

With rolling body supporting shaft in housing

C464S145000, C301S105100

Reexamination Certificate

active

06800033

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a wheel drive unit which is a combination of a wheel support rolling bearing unit, a constant velocity joint unit and a snap ring, and is used for rotatably supporting with respect to a suspension unit, a driven wheel {the front wheel of a FF vehicle (front engine, front drive wheel) the rear wheel of both a FR vehicle (front engine, rear drive wheel) and a RR vehicle (rear engine, rear drive wheel) and all wheels of a 4 WD vehicle (four drive wheel)} supported on an independent suspension type suspension, and for rotationally driving the driven wheel.
BACKGROUND OF THE INVENTION
In order to rotatably support a vehicle wheel with respect to a suspension unit, various kinds of rolling bearing units for wheel support with an outer ring and inner ring assembled so as to be freely rotatable via rolling elements, are used. Moreover, a wheel support rolling bearing unit for supporting a driven wheel in a suspension of the independent suspension type and rotationally driving the driven wheel, must be combined with a constant velocity joint to smoothly transmit (maintain constant velocity) the rotation of the drive shaft to the abovementioned vehicle wheel, regardless of the relative displacement between a differential gear and the driven wheel and of a steering angle applied to the wheel.
FIG. 6
shows a typical bearing unit
3
for wheel drive wherein a rolling bearing unit
1
for wheel support and a constant velocity joint
2
are combined together for this kind of purpose.
This rolling bearing unit for wheel support
1
is found by rotatably supporting a hub
5
and an inner ring
6
on the inner diameter side of an outer ring
4
via a plurality of rolling elements
7
. Of these, the outer ring
4
when connectingly secured to a knuckle
9
(refer to
FIG. 7
mentioned below) constituting a suspension unit by means of a first flange
8
provided on the outer peripheral face thereof, does not rotate even at the time of use. Furthermore, a double row of outer ring raceways
10
is provided on the inner peripheral face of the outer ring
4
, and the hub
5
and the inner ring
6
are rotatably supported on the inner diameter side, concentric with the outer ring
4
.
Of these, the hub
5
is provided with a second flange
11
for supporting the wheel, on a portion near an outer end (the end which is on the outside in a widthwise direction of the vehicle when fitted to the vehicle, namely, the left hand side of each figure including
FIG. 6
) of the outer peripheral face. Furthermore, the first inner ring raceway
12
is formed on a central portion of the outer peripheral face of the hub
5
. Similarly, an inner ring
6
with a second inner ring raceway
14
formed on an outer peripheral face thereof, is externally secured to a small diameter step
13
formed on an inner end (the end which is on the middle side in a widthwise direction of the vehicle when fitted to the vehicle, namely the right hand side of each figure). Moreover, in the center portion of the hub
5
, a spline bore
15
is provided, so that the hub
5
is formed in a hollow cylindrical shape.
On the other hand, the constant velocity joint
2
has an outer ring
16
for constant velocity joint, an inner ring
17
for constant velocity joint and a spline shaft
18
. Of these, the outer ring
16
for constant velocity joint and the spline shaft
18
constitute a drive member
19
. That is, the spline shaft
18
is provided on an outer end of the drive member
19
and is freely engaged with the spline bore
15
, and the outer ring
16
for constant velocity joint is provided on an inner end of the drive member
19
. At a plurality of places on the inner peripheral face of the outer ring
16
for constant velocity joint around the circumferential direction are respectively formed outside engaging grooves
20
at right angles to the circumferential direction. Moreover, regarding the inner ring
17
for constant velocity joint, a second spline bore
21
is formed at right angles to the circumferential direction in a center portion, and on the outer peripheral face, inside engaging grooves
22
are formed at right angles to the circumferential direction in portions coinciding with the outside engaging grooves
20
. Moreover, balls
23
are provided between each of the inside engaging grooves
22
and each of the outside engaging grooves
20
so as to be freely rotatable along each engaging groove
22
and
20
, with the balls
23
being retained in cage
24
. At a part of the inner peripheral face of the outer ring
16
for constant velocity joint, portions between pairs of circumferentially adjacent outside engaging grooves
20
constitute cage guide faces
25
. Each cage guide face
25
is positioned on a single spherical surface with a displacement center of the constant velocity joint
2
as the center thereof. Regarding the shape of the constituent elements of this kind of constant velocity joint
2
, this is similar to the case of a well known Rzeppa type or Birfield type constant velocity joint, and since this has no relevance to the gist of the present invention, detailed description is omitted.
In combining the above described constant velocity joint
2
and the wheel support rolling bearing unit
1
, the spline shaft
18
is inserted into the spline bore
15
of the hub
5
from the inner side towards the outer side. Then a nut
27
is screwed onto an external thread portion
26
provided on an outer end portion of the spline shaft
18
projecting from an outer end face of the hub
5
, and then by tightening, these are connected and secured together. In this condition, since the inner end face of the inner ring
6
is abutted against the outer end face of the outer ring
16
for constant velocity joint, there is no displacement of the inner ring
6
in a direction to come off from the small diameter step portion
13
. At the same time, an appropriate pre-load is applied to each of the rolling elements
7
.
Moreover, when fitted to the suspension unit of a vehicle, a male spline portion
29
provided on an outer end of a drive shaft
28
is spline engaged with a second spline bore
21
provided in a central portion on the inner ring
17
for constant velocity joint. Then, a snap ring
37
which is stoppingly engaged in an engaging groove
30
formed around the whole periphery in the outer peripheral face at the outer end of the male spline portion
29
, is engaged with an engaging step portion
32
formed in an opening rim at the outer end of the second spline bore
21
, thereby preventing the male spline portion
29
from coming out from the second spline bore
21
. Furthermore, the inner end of the drive shaft
28
is connectingly secured to the center of a trunnion
34
(refer to
FIG. 1
showing a first example of an embodiment of the present invention) of a tripod type constant velocity joint
33
provided on an output shaft of a differential gear.
Regarding the first example of the abovementioned conventional construction shown in
FIG. 6
, the weight is increased because the rolling bearing unit
1
for wheel support and the constant velocity joint
2
are connectingly secured based on the threaded and tightened engagement between the male thread portion
29
and the nut
27
. That is, providing the external thread portion
26
on the spline shaft
18
of the constant velocity joint
2
requires lengthening of the spline shaft
18
, and the nut
27
also becomes necessary. Therefore the axial dimension and the weight of the bearing unit
3
for wheel drive are increased by the male thread portion
26
and the nut
27
.
To address this problem, in the specification of U.S. Pat. No. 4,881,842 is disclosed as shown in
FIG. 7
, a bearing unit
3
a
for wheel drive that enables shortening of the axial dimension and a reduction in weight, by connectingly securing the rolling bearing unit for wheel support and the constant velocity joint by a relatively simple construction. Also in the case of the secured example of the conventional construction sh

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