SERVODIRECTION

POWER STEERING DEVICE

Abrégé anglais

To provide a power steering device capable of
increasing a degree of freedom in layout, stabilizing an
oil liquid surface and preventing air from being included
or preventing mixing of some foreign materials.
[Solving Means] There are provided a power assisting
cylinder 20 arranged between a steering shaft 14 and a
chassis frame 11; a control valve 21 operated by the
steering shaft to control the power assisting cylinder;
an oil pump 23 for pressurizing operating oil supplied to
the power assisting cylinder; and an oil tank 24 for
storing the operating oil, wherein the oil tank is of a
closed type and integrally arranged in the oil pump.

Revendications

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A power steering device for a vehicle, comprising:
a power assist cylinder, said power assist cylinder
being arranged between a steering shaft and a chassis frame of
the vehicle;
a control valve operable by said steering shaft to
control said power assist cylinder;
an oil pump for pressurizing operating oil supplied
to said power assist cylinder; and
an oil tank for storing said operating oil, said oil
tank being integrally installed in said oil pump, and being
connected with an oil passage for returning the operating oil
to the oil pump, and further, said oil tank being closed, thus
enabling air in the oil tank to be completely removed so that
a variation in a surface of the operating oil in the oil tank
can be eliminated, and foreign matters can be prevented from
merging with the operating oil.
2. ~The power steering device for a vehicle according to
claim 1, wherein the steering shaft includes a spool lever
integrally attached thereto, said control valve being
attachable to the spool lever to be operable by the steering
shaft.
3. ~The power steering device for a vehicle according to
claim 1, further comprising an operating oil supply pipe
connected between said oil pump and said control valve, said
operating oil supply pipe for supplying the pressurized
operating from said oil pump to said control valve.
4. ~The power steering device for a vehicle according to
claim 1, further comprising an operating oil returning pipe
connected between said control valve and said oil pump, said
operating oil returning pipe for returning the operating oil
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from said control valve to said oil pump.
5. ~The power steering device for a vehicle according to
claim 3, further comprising an operating oil returning pipe
connected between said control valve and said oil pump, said
operating oil returning pipe for returning the operating oil
from said control valve to said oil pump.
6. ~The power steering device for a vehicle according to
claim 4, wherein said operating oil returning pipe is
connected to said oil tank, said oil tank being connected to
an oil passage formed in said oil pump for returning the
operating oil to said oil pump.
7. ~The power steering device for a vehicle according to
claim 5, wherein said operating oil returning pipe is
connected to said oil tank, said oil tank being connected to
an oil passage formed in said oil pump for returning the
operating oil to said oil pump.
8. ~The power steering device for a vehicle according to
claim 1, wherein the steering shaft includes a center arm
projecting radially therefrom, said power assist cylinder
being attachable to the center arm for assisting in the
rotation of the steering shaft.
9. ~A power steering device in a vehicle, comprising:
a chassis frame;
a steering shaft rotatably mounted to said chassis
frame;
a power assist cylinder, said power assist cylinder
being mounted between said steering shaft and said chassis
frame;
a control valve operably mounted to said steering
shaft to control said power assist cylinder;
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an oil pump for pressurizing operating oil supplied
to said power assist cylinder; and
an oil tank for storing said operating oil, said oil
tank being integrally installed in said oil pump, and being
connected with an oil passage for returning the operating oil
to the oil pump, and further, said oil tank being closed, thus
enabling air in the oil tank to be completely removed so that
a variation in a surface of the operating oil in the oil tank
can be eliminated, and foreign matters can be prevented from
merging with the operating oil.
10. ~The power steering device in a vehicle according to
claim 9, wherein said steering shaft includes a spool lever
integrally attached thereto, said spool lever being
operatively connected to said control valve for operating said
control valve.
11. ~The power steering device in a vehicle according to
claim 9, further comprising an operating oil supply pipe
connected between said oil pump and said control valve, said
operating oil supply pipe for supplying the pressurized
operating from said oil pump to said control valve.
12. ~The power steering device in a vehicle according to
claim 9, further comprising an operating oil returning pipe
connected between said control valve and said oil pump, said
operating oil returning pipe for returning the operating oil
from said control valve to said oil pump.
13. ~The power steering device in a vehicle according to
claim 11, further comprising an operating oil returning pipe
connected between said control valve and said oil pump, said
operating oil returning pipe for returning the operating oil
from said control valve to said oil pump.
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14. ~The power steering device in a vehicle according to
claim 12, wherein said operating oil returning pipe is
connected to said oil tank, said oil tank being connected to
an oil passage formed in said oil pump for returning the
operating oil to said oil pump.
15. ~The power steering device in a vehicle according to
claim 13, wherein said operating oil returning pipe is
connected to said oil tank, said oil tank being connected to
an oil passage formed in said oil pump for returning the
operating oil to said oil pump.
16. ~The power steering device in a vehicle according to
claim 9, wherein the steering shaft includes a center arm
projecting radially therefrom, said power assist cylinder
being attached to said center arm for assisting in the
rotation of said steering shaft.
17. ~The power steering device in a vehicle according to
claim 1, wherein said oil tank is integrally installed beneath
said oil pump.
18. ~The power steering device in a vehicle according to
claim 9, wherein said oil tank is integrally installed beneath
said oil pump.
19. ~The power steering device for a vehicle according to
claim 1, wherein the oil passage has a longitudinal axis which
is substantially perpendicular to an axis of the oil pump.
20. ~The power steering device in a vehicle according to
claim 9, wherein the oil passage enters the oil pump at a
position offset from a center of the oil pump
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Description

CA 02357481 2001-09-19
JJ-11 319CA
TITLE: Power Steering Device
FIELD OF THE INVENTION
The present invention relates to a power
steering device, and more particularly, a power steering
device which is preferably used in an all terrain
vehicle.
BACKGROUND OF THE INVENTION
As the prior art power steering device of this
kind, the structure shown in Fig. 3 is well known.
The power steering device shown in this figure
is constituted of a power assisting cylinder 3 arranged
between a steering shaft 1 and a chassis frame 2, a
control valve 4 operated by the steering shaft 1 to
control the power assisting cylinder 3, an oil pump 5 for
pressurizing the operating oil supplied to the power
assisting cylinder 3, and an oil tank 6 for storing the
operating oil, wherein the oil tank 6 is of a surrounding
atmosphere released type and fixed to the chassis frame
2.
Then, the oil pump 5, the oil tank 6 and the
control valve 4 are connected to each other through three
oil pipes 7.
However, the aforesaid prior art shows a
problem that the power assisting cylinder 3, control
valve 4, oil pump 5 and oil tank 6 are separately and
individually arranged, their layout is restricted when
they are installed at the chassis frame.
In addition, since the oil tank 6 is of a
surrounding atmosphere releasing type, there is a
possibility that the oil liquid surface in the oil tank 6
is not stabilized and further some foreign materials
enter from outside into the oil tank 6.
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CA 02357481 2001-09-19
JJ-11 319CA
The present invention has been invented in view
of the problems found in the prior art and it is an
object of the present invention to provide a power
steering device capable of increasing a degree of freedom
in layout, stabilizing an oil liquid surface and
preventing some foreign materials from entering into the
device.
SUMMARY OF THE INVENTION
The power steering device of the present
invention is characterized in that the same is comprised
of a power assisting cylinder arranged between a steering
shaft and a chassis frame, a control valve operated by
the steering shaft to control the power assisting
cylinder, an oil pump for pressurizing operating oil
supplied to the power assisting cylinder, and the oil
tank is of a closed type and integrally installed in the
oil pump.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are
shown in the drawings, wherein:
[Fig. 1] A side elevational view for showing an
all terrain vehicle to which one preferred embodiment of
the present invention is applied.
[Fig. 2] A system configuration view for
showing one preferred embodiment of the present
invention.
[Fig. 3] A schematic system configuration view
for showing one prior art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, one preferred
embodiment of the present invention will be described in
detail as follows.
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CA 02357481 2001-09-19
JJ-11 319CA
Fig. 1 illustrates a straddling type vehicle
acting as a vehicle to which the preferred embodiment of
the present invention is applied, wherein there are
provided a pair of front wheels 12 and a pair of rear
wheels 13 supported in forward or rearward and rightward
or leftward directions of a chassis frame 11 having an
engine 10 mounted at a central part of the chassis; a
steering shaft 14 pivotally installed at the front part
of the chassis frame 11; a steering arm 15 for connecting
each of the front wheels 12 acting as steering wheels
with the steering shaft 14; a steering wheel 16 installed
at the upper part of the steering shaft 14; a seat 17
installed at the chassis frame 11 at a rear position of
the steering wheel 16; and a power steering device 18
concerning the preferred embodiment installed between a
part near the steering shaft 14 and the chassis frame 11.
This power steering device 18 is, as shown in
Fig. 2, provided with a center arm 19 arranged so as to
project in a radial direction at the lower part of the
steering shaft 14; a power assisting cylinder 20
installed between it and the chassis frame 11; a control
valve 21 installed at the power assisting cylinder 20 to
control the power assisting cylinder 20; a spool lever 22
integrally arranged at the steering shaft 14 to operate
the control valve 21; an oil pump 23 installed at the
engine 10 and supplying operating oil to the control
valve 21 while being pressurized; and an oil tank 24
storing the operating oil.
Then, the oil pump 23 and the control valve 21
are connected through the operating oil supply pipe 25
supplying the operating oil pressurized by the oil pump
23 to the control valve 21 and through the operating oil
returning pipe 26 for returning the operating oil from
the control valve 21 to the oil pump 23.
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CA 02357481 2001-09-19
JJ-11 319CA
Then, in the preferred embodiment, the oil tank
24 is integrally fixed to the oil pump 23, and it is
connected with the oil passage 23a for the operating oil
returning passage formed in the oil pump 23.
In the case of the power steering device 18
concerning the preferred embodiment constructed as
described above, the steering wheel 16 is operated in any
one of the rightward or leftward direction, the spool
lever 22 fixed to the steering wheel 16 is oscillated to
cause the control valve 21 to be operated, and the
operating oil supplied from the oil pump 23 is supplied
to the power assisting cylinder 20 and then a turning
force of the steering wheel 16 toward its operating
direction is given to the steering shaft 14 through the
center arm 19.
With such an arrangement as above, operating
force of the steering wheel 16 is reduced.
In turn, the operating oil discharged out of
the power assisting cylinder 20 is returned back to the
oil tank 24 arranged at the oil pump 23 through the
control valve 21 and the operating oil returning pipe 26.
As described above, in the preferred embodiment
of the present invention, after the operating oil
returned back from the power assisting cylinder 20 is
returned back to the oil tank 24 arranged at the oil pump
23, the operating oil is supplied to the oil pump 23.
In this case, the oil tank 24 is integrally
arranged at the oil pump 23, thereby it is not necessary
to make a separate arrangement of the oil tank 24.
Accordingly, it is not necessary to make a
separate arrangement of the mounting space for the oil
tank 24, the effective utilization of space for the
chassis can be carried out, and a degree of freedom in
layout is increased.
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CA 02357481 2001-09-19
JJ-11 319CA
Further, the oil pipings can be concentrated
into two pipes, i.e. an operating oil supply pipe 25
communicating between the oil pump 23 and the control
valve 21, and an operating oil returning pipe 26, the oil
piping communicating between the oil pump 23 and the oil
tank 24 that were required in the prior art can be
eliminated and a degree of freedom in layout can be
increased in view of this fact.
Further, the oil tank 24 is of a closed type,
thereby it can be used under a state in which air in the
oil tank 24 is completely removed, so that variation in
the oil liquid surface is eliminated and not only
inclusion of air is prevented, but also some foreign
materials such as water or mud can be prevented from
merging into the operating oil.
Further, various shapes or sizes of each of the
component members indicated in the aforesaid preferred
embodiment or the like are only one example and they can
be modified in various manner in response to request in
design.
For example, by allowing a variation in volume
by the oil tank 24 of a bellows structure, an effect of
preventing inclusion of air described above can be
increased or variation in volume caused by the variation
in temperature or the like of the operating oil can be
adapted.
As described above, in accordance with the
power steering device of the present invention, the oil
tank is integrally assembled with the oil pump, it is not
necessary to arrange a separate mounting space for the
oil tank and the effective utilization of the space for
the chassis can be attained and a degree of freedom in
layout can be increased.
Further, the oil piping for use in
communicating between the oil pump and the oil tank can
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CA 02357481 2001-09-19
JJ-11 319CA
be eliminated and a degree of freedom for its layout can
be increased.
In addition, the oil tank is of a closed type,
it can be used under a state in which air in the oil tank
is completely removed from it, so that variation in the
oil liquid surface is eliminated and inclusion of air is
prevented and it is also possible to prevent some foreign
materials such as water or mud and the like from entering
into the operating oil.
Accordingly, the present invention is
preferentially used in an all terrain vehicle.
Although various preferred embodiments of the
present invention have been described herein in detail,
it will be appreciated by those skilled in the art, that
variations may be made thereto without departing from the
spirit of the invention or the scope of the appended
claims.
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