Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02357483 2001-09-19
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TITLE: POWER STEERING DEVICE
FIELD OF THE INVENTION
This invention relates to a power steering
device installed on a vehicle.
BACKGROUND OF THE INVENTION
As the prior art power steering device of this
kind, the structure shown in Fig. 9 is well known in the
art.
The power steering device shown in this figure
is constituted by 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.
Then, the oil pump 5, the oil tank 6 and the
control valve 4 are connected to each other through three
oil pipes 7.
In addition, the steering shaft 1 is provided
with a spool lever 8 for operating the control valve 4,
and a center arm 9 oscillated by the power assisting
cylinder 3.
The prior art power steering device constituted
as described above is operated such that when the
steering shaft 1 is turned in any of the rightward or
leftward direction, the control valve 4 is operated by
the spool lever 8, thereby operating oil is supplied to
the power assisting cylinder 3.
Then, the center arm 9 is oscillated in the
turning direction of the steering shaft 1 under an
operation of the power-assisting cylinder 3, and the
operating force of the steering shaft 1 is reduced.
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In the aforesaid prior art, the power assisting
cylinder and the control valve 4 are arranged at a side
of the steering shaft 1, and they are connected by the
steering shaft 1 by the spool lever 8 and the center arm
9, so that the prior art has a problem that the entire
system becomes large in size and a certain accuracy is
required in connecting operation for each of the
component parts as well as its assembling work.
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 saving a space for a system and
performing an easy assembling.
SUMMARY OF THE INVENTION
The power steering device of the present
invention is a power steering device installed between a
steering shaft rotatably installed at a chassis frame and
a steering wheel connected to the steering shaft. The
power steering device is comprised of a cylindrical
holder coaxially arranged on the steering shaft, a
cylindrical rotary cylinder coaxially and rotatably
installed in this holder and forming two oil chambers
spaced apart in a circumferential direction between it
and an inner surface of the holder, and a spool changing-
over member coaxially and rotatably inserted in the
rotary cylinder and connected to the steering wheel. The
holder is provided with an operating oil supply hole and
an operating oil discharging hole. The rotary cylinder
is formed with a pair of communicating holes between each
of the oil chambers and an inside of the rotary cylinder,
the spool changing-over member is formed with operating
oil passages where a space part between it and an inner
circumferential surface of the rotary cylinder is divided
into two segments in a circumferential direction and
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connected with the supply holes and discharging holes.
There are provided a pair of partition walls for
changing-over communicating state between the pair of
operating oil passages and the pair of communicating
holes under a relative rotation with the rotary cylinder.
The power steering device in an aspect of the
invention is characterized in that the both operating oil
passages are connected with the spool changing-over
member described above and there is provided a check
valve for preventing a flow of operating oil directed
from the operating oil passages connected with the supply
hole for the operating oil and directed toward the
operating oil passage connected with the discharging hole
for the operating oil.
The power steering device in another aspect of
the invention is characterized in that there is provided
between the rotary cylinder and the spool changing-over
member a differential mechanism for integrally rotating
the rotary cylinder and the spool changing-over member,
when a steering force applied to the steering shaft is
low, and when the steering force is larger than a
predetermined value in a case of allowing a relative
rotation between the rotary cylinder and the spool
changing-over member.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are
shown in the drawings, wherein:
[Fig. 1] A side elevational view for showing
a cross-country running 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.
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[Fig. 3] A longitudinal sectional view for
showing a substantial part to illustrate one preferred
embodiment of the present
invention.
[Fig. 4] A cross sectional
view for showing a
substantial part to illustrate an operation of one
preferred embodiment the present invention.
of
[Fig. 5] A cross sectional
view for showing a
substantial part to illustrate an operation of one
preferred embodiment the present invention.
of
[Fig. 6] A cross sectional
view for showing a
substantial part to illustrate an operation of one
preferred embodiment the present invention.
of
[Fig. 7] A cross sectional
view for showing a
substantial part to illustrate an operation of one
preferred embodiment the present invention.
of
[Fig. 8] A cross sectional
view for showing a
substantial part to illustrate an operation of one
preferred embodiment the present invention.
of
[Fig. 9] A schematic configuration view for
showing a prior art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, preferred
embodiments of the present invention will be described in
detail as follows.
Fig. 1 illustrates a saddle type vehicle acting
as a vehicle to which the preferred embodiments 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
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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 of the
preferred embodiment installed in the midway part of the
steering shaft 14.
To the lower part of the steering shaft 14 is
cooperatively arranged an output shaft 19 to which the
steering arm 15 is fixed as shown in Fig. 2, and the
power steering device 18 is installed at a connecting
part between the output shaft 19 and the steering shaft
14.
As shown in Fig. 2, the power steering device
18 is comprised of a cylindrical holder 20 coaxially
arranged on the steering shaft 14; a cylindrical rotary
cylinder 23 coaxially and rotatably installed in the
holder 20 and forming two oil chambers 21, 22 (refer to
Fig. 4) spaced apart in a circumferential direction
between it and the inner surface of the holder 20; and a
spool changing-over member 24 inserted coaxially with the
rotary cylinder rotatably inserted into the rotary
cylinder 23 and connected to the output shaft 19. The
spool changing over member 24 is connected to the
steering shaft. The holder 20 is provided with operating
oil supply hole 25 and operating oil discharging hole 26,
the rotary cylinder 23 is formed with a pair of
communicating holes 27, 28 connected with each of the oil
chambers 21, 22 and the inner side of the rotary cylinder
23, the spool changing-over member 24 is formed with
operating oil passages 29, 30 dividing a space between it
and the inner circumferential surface of the rotary
cylinder 23 into two segments in a circumferential
direction and connected with the supply hole 25 and the
discharging hole 26, and further the spool changing-over
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member is provided with a pair of partition walls 31, 32
changing-over the communicating
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state between the pair of operating oil passages 29, 30
and the pair of communicating holes 27, 28 under a
relative rotation of the rotary cylinder 23.
The spool changing-over member 24 is provided
with a check valve 33 to cause the both operating oil
passages 29, 30 to be connected to each other and in turn
to prevent a flow of operating oil from the operating oil
passage 29 connected with the supply hole 25 for the
operating oil toward the operating oil passages 30
connected with the discharging hole 26 for the operating
oil.
In addition, the rotary cylinder 23 is provided
with a protruding pin 34 along an axial direction thereof
and further the spool changing-over member 24 is provided
with a pin 35 positioned on the same axis of the pin 34.
Further, the spool changing-over member 24 is
provided at its circumference a C-ring 36 which can be
deformed resiliently in its diameter direction, and each
of the pins 34, 35 is engaged with this discontinuous
part.
Accordingly, the end portions of the
discontinuous part of this C-ring 36 are abutted while
holding the both pins 34, 35, and when the operating
force of the steering shaft 14 is low, the rotary
cylinder 23 and the spool changing-over member 24 are
integrally rotated, and when the operating force becomes
more than a torque set in reference to a modulus of
elasticity of the C-ring 36, the C-ring 36 is deformed to
be pushed open, thereby the rotary cylinder 23 and the
spool changing-over member 24 are relatively rotated and
a differential mechanism in the preferred embodiment is
constituted by these both pins 34, 35 and the C-ring 36.
Then, operation of the preferred embodiment
constructed as described above will be described as
follows.
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At first, under a state in which no steering
operation is carried out, each of both partition walls
31, 32 is oppositely faced against the central part of
the communicating holes 27, 28 as shown in Fig. 5,
thereby both operating oil chambers 21, 22 are connected
with the both operating oil passages 29, 30.
Accordingly, no assisting force is produced
under a released state of the both operating oil chambers
21, 22 .
Then, in the case that the steering wheel 16 is
gradually turned left, the C-ring 36 is not deformed due
to a low steering force, and the rotary cylinder 23 and
the spool changing-over 24 are integrally rotated.
With such an arrangement as above, as shown in
Fig. 4, the rotary cylinder 23 and the spool changing
over member 24 are turned in a leftward direction while
holding the state shown in Fig. 5, resulting in that no
assisting force is produced even under this state.
This is an operating state in the case that the
steering angle is low and no assisting force is required.
When the steering is carried out under a large
steering angle, its steering force is increased, although
in the case that the steering force is larger than a
torque set by the C-ring 36, it is resiliently deformed
such that the diameter of the C-ring 36 is expanded,
resulting in that the rotary cylinder 23 and the spool
changing-over member 24 are rotated relatively as shown
in Fig. 7.
With such an arrangement as above, the
partition walls 31, 32 are displaced from the
communicating holes 27, 28 to cause one operating oil
passage 29 to be connected only with the left side
operating oil chamber 21 and further the other operating
oil passage 30 to be connected only with the right side
operating oil chamber 22.
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With such an arrangement as above, operating
oil is supplied to the left side operating oil chamber 21
from the operating oil supply hole 25 through the
operating oil passage 29, resulting in that pressure
within the left side operating oil chamber 21 is
increased, a leftward assisting force acts on the rotary
cylinder 23 and the steering force is reduced.
Such a function can be similarly attained also
in the rightward steering operation. In Figs. 6 and 9 a
positional relation between the rotary cylinder 23 and
the spool changing-over member 24 is illustrated.
In addition, when a kick-back or the like
occurs during the steering operation, the operating oil
flows through the spool changing-over member 24 under an
action of the check valve 33 to cause a shock of the
kick-back to be damped.
As described above, in accordance with the
power steering device 18 of this preferred embodiment,
the entire device is arranged on an axis of the steering
shaft 14, thereby it is possible to make a compact
steering device and eliminate an occupied space in the
chassis.
In addition, since the device can be assembled
concurrently when the steering shaft 14 is assembled, its
assembling work becomes convenient.
Various kinds of shapes or sizes of each of the
components indicated in the aforesaid preferred
embodiment are mere examples and they can be modified in
various manner in response to a request in design.
For example, since the operating oil supply
hole 25 or operating oil discharging hole 26 described
above is fixed, the operating oil supplying passage can
be constituted by a pipe and its durability can be
improved.
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Further, the supply hole 25 or discharging hole
26 is closed to cause the operating oil to be enclosed
therein, resulting in that it becomes possible to apply
it as a steering damper under utilization of viscosity of
the operating oil.
As described above, in accordance with the
power steering device of the present invention, the power
steering device is mounted coaxially on the steering
shaft, it becomes possible to make a compact device and
further an occupied space on the chassis is sufficiently
narrow.
In addition, since the device can be assembled
in concurrent with the assembling of the steering shaft,
its assembling operation becomes convenient and its
connecting portions are less in number and an assembling
accuracy can be improved.
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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