Planetary gear transmission systems or components – Differential planetary gearing – Spur gear differential
Reexamination Certificate
1999-12-28
2001-09-18
Bonck, Rodney H. (Department: 3681)
Planetary gear transmission systems or components
Differential planetary gearing
Spur gear differential
C475S336000
Reexamination Certificate
active
06290624
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a 4-wheel drive vehicle, and more particularly, to a center differential for a 4-wheel drive vehicle that differently distributes drive torque to front and rear wheels while functioning as a limited slip differential.
BACKGROUND OF THE INVENTION
FIGS. 3 and 4
show a conventional center differential used in a 4-wheel drive vehicle. The terms “front” and “rear” as used herein shall mean and refer to the respective forward and rearward directions of the vehicle body.
As shown in the drawings, a ring gear
51
is disposed around a differential case
52
and connected to a drive pinion (not shown). Front and rear side gears
53
and
54
are disposed within the differential case
52
and are splined to a drive shaft (not shown). The side gears
53
and
54
are provided with helical gear teeth
55
at their outer surfaces.
Four sets of pinion gear assemblies
57
each having first and second pinion gears
60
and
61
are disposed within gear grooves
56
formed on an inner wall of the differential case
52
and are engaged with the side gears
53
and
54
. The first pinion gear
60
has long and short helical gears
58
and
59
disposed along a common axis, and the second pinion gear
61
has long and short helical gears
63
and
62
disposed along a common axis. The first and second pinion gears
60
and
61
of each set of pinion gear assemblies
57
are disposed such that the long and short helical gears
58
and
59
mesh with the short and long helical gears
62
and
63
of the second pinion gear
61
, respectively. In addition, the long helical gears
58
and
63
mesh with the rear and front side gears
54
and
53
, respectively.
End washers
65
are disposed between the side gears
53
and
54
and the differential case
52
.
When the vehicle runs straight forward, because no rotation speed difference occurs between the front and rear side gears
53
, and
54
, the pinion gears
60
and
61
do not rotate about their axes and the front and rear side gears
53
and
54
rotate together with the differential case
52
.
When a speed difference occurs between the front and rear side gears
53
and
54
, the pinion gears
60
and
61
compensate for the speed difference by reversibly rotating with respect to each other.
When a load difference occurs between the front and rear wheels, the front and rear side gears
53
and
54
operate such that a mesh-reacting force is generated between the side gears
53
and
54
and the pinion gears
60
and
61
. The mesh-reacting force acts as a thrust force applied to a teeth surface of the helical gear in an axial direction.
Accordingly, the side gears
53
and
54
are forced against the washers
64
and
65
, and the pinion gears
60
and
61
are engaged with the differential case
52
by the thrust force. As a result, the side gears
53
and
54
and the pinion gears
60
and
61
are integrally connected to the differential case
52
, thereby distributing equal drive torque to front and rear differentials (not shown) to realize limited slip differential operation.
However, in the above-described differential, because the diameters of the front and rear side gears are identical to each other and the pinion gears are meshed with the front and rear side gears in parallel, a friction area between the pinion gears and the inner wall of the differential case is limited, making it difficult to obtain limited slip differential force during a limited slip differential mode.
In addition, it is preferable to differently distribute drive torque to front and rear wheels to meet a balance with respect to the ground contacting force of the front and rear wheels. However, in the conventional center differential, because the distributing ratio of drive torque to the front and rear wheels is fixed at 50:50, it is difficult to enlarge the range of driving capability of the center differential.
SUMMARY OF THE INVENTION
The present invention has been made in an effort to solve the above-described problems.
It is an objective of the present invention to provide a center differential that can provide high limited slip differential force and distribute drive torque to front and rear wheels in accordance with the ground contacting force of the front and rear wheels.
To achieve the above objective, the present invention provides a center differential for a four-wheel drive vehicle, comprising a differential case having a longitudinal axis, front and rear side gears disposed within the differential case in a longitudinal direction, and a plurality of pinion gears engaged with the outer circumferences of the front and rear side gears, wherein each rotating axis of the pinion gears is declined at a predetermined angle with respect to the longitudinal axis of the differential case.
REFERENCES:
patent: 1297954 (1919-03-01), Williams
patent: 5108353 (1992-04-01), Brewer et al.
patent: 5242336 (1993-09-01), Hori
patent: 5385514 (1995-01-01), Dawe
patent: 5433673 (1995-07-01), Cilano
patent: 5443431 (1995-08-01), Cilano
patent: 5669844 (1997-09-01), Homan et al.
patent: 5730679 (1998-03-01), Ichiki
patent: 5910066 (1999-06-01), Schulz et al.
patent: 6059683 (2000-05-01), Teraoka et al.
patent: 0920636 (1947-04-01), None
patent: 257825 (1949-04-01), None
Bonck Rodney H.
Christie Parker & Hale LLP
Hyundai Motor Company
Pang Roger
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