U.S. patent application number 15/184534 was filed with the patent office on 2016-12-22 for damping force variable shock absorber.
This patent application is currently assigned to Showa Corporation. The applicant listed for this patent is Showa Corporation. Invention is credited to Naoya KUROIWA, Kazuhiro MIWA.
Application Number | 20160369862 15/184534 |
Document ID | / |
Family ID | 56134218 |
Filed Date | 2016-12-22 |
United States Patent
Application |
20160369862 |
Kind Code |
A1 |
MIWA; Kazuhiro ; et
al. |
December 22, 2016 |
DAMPING FORCE VARIABLE SHOCK ABSORBER
Abstract
There is provided a compact damping force variable shock
absorber capable of implementing different adjustments for a
compression-side stroke and an extension-side stroke as initial
settings. A damping force variable device in one embodiment
includes: a main valve that opens and closes to control flow of oil
caused by sliding of a piston in a cylinder, thereby generating
damping force; a pilot chamber into which a portion of the flow of
the oil is introduced so that internal pressure is applied to the
main valve in a valve-closing direction; a pilot valve that opens
and closes to adjust the internal pressure of the pilot chamber;
and a communication passage that communicates the pilot chamber
with a rod-side oil chamber or a piston-side fluid chamber.
Inventors: |
MIWA; Kazuhiro;
(Fukuroi-shi, JP) ; KUROIWA; Naoya; (Fukuroi-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Showa Corporation |
Gyoda-shi |
|
JP |
|
|
Assignee: |
Showa Corporation
Gyoda-shi
JP
|
Family ID: |
56134218 |
Appl. No.: |
15/184534 |
Filed: |
June 16, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16F 2228/066 20130101;
F16F 9/185 20130101; F16F 9/46 20130101; F16F 13/007 20130101; F16F
9/464 20130101; B62K 25/08 20130101; B62M 7/00 20130101; F16F 9/465
20130101 |
International
Class: |
F16F 9/46 20060101
F16F009/46; B62K 25/08 20060101 B62K025/08; F16F 9/18 20060101
F16F009/18 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 17, 2015 |
JP |
2015-122328 |
Claims
1. A damping force variable shock absorber comprising: a cylinder
in which fluid is enclosed; a piston slidably fitted into the
cylinder; a piston rod having one end connected to the piston and
the other end extended outside the cylinder; a rod-side fluid
chamber partitioned by the piston and provided closer to the other
end in an axial direction of the cylinder than the piston; a
piston-side fluid chamber provided closer to one end in the axial
direction of the cylinder than the piston; and a damping force
variable device that controls flow of the fluid enclosed in the
cylinder so that damping force can be varied, wherein the damping
force variable device includes: a main valve that opens and closes
to control the flow of the fluid caused by sliding of the piston in
the cylinder, thereby generating damping force; a pilot chamber
into which a portion of the flow of the fluid is introduced so that
internal pressure is applied to the main valve in a valve-closing
direction; a pilot valve that opens and closes to adjust the
internal pressure of the pilot chamber; and a communication passage
that allows the pilot chamber or a passage between the pilot
chamber and the pilot valve to communicate with the rod-side fluid
chamber or the piston-side fluid chamber.
2. The damping force variable shock absorber according to claim 1,
wherein the communication passage allows the pilot chamber or the
passage between the pilot chamber and the pilot valve to
communicate with the rod-side fluid chamber.
3. The damping force variable shock absorber according to claim 1,
wherein the communication passage allows the pilot chamber or the
passage between the pilot chamber and the pilot valve to
communicate with the piston-side fluid chamber.
4. The damping force variable shock absorber according to claim 1,
further comprising: an outer tube provided on a vehicle body side,
the other end of the piston rod being attached to the outer tube;
an inner tube as the cylinder slidably inserted in an inner
circumference of the outer tube, the piston being slidably provided
in an inner circumference of the inner tube; a first bush provided
on an inner circumference on an axle side of the outer tube; a
second bush provided on an outer circumference on the vehicle body
side of the inner tube; an annular fluid chamber surrounded by the
outer tube, the inner tube, the first bush, and the second bush, a
cross-sectional area of the piston rod being smaller than a
cross-sectional area of the annular fluid chamber; a bottomed
cylindrical partition wall member, a portion of which is provided
in the inner tube, the piston rod being slidably inserted in the
partition wall member; a fluid storage chamber partitioned by the
partition wall member in the inner tube and formed closer to the
vehicle body side than the partition wall member; a fluid chamber
partitioned by the partition wall member in the inner tube and
formed closer to the axle side than the partition wall member, the
rod-side fluid chamber being partitioned by the piston in the fluid
chamber and formed closer to the vehicle body side than the piston,
the piston-side fluid chamber partitioned by the piston in the
fluid chamber and formed closer to the axle side than the piston; a
communication hole formed in the inner tube so as to allow the
annular fluid chamber and the rod-side fluid chamber to communicate
with each other; a check valve provided in the partition wall
member so as to allow only flow of fluid from the fluid storage
chamber to the rod-side fluid chamber; and a throttle provided in
the partition wall member so as to restrict the flow of the fluid
between the fluid storage chamber and the rod-side fluid
chamber.
5. The damping force variable shock absorber according to claim 1,
wherein the damping force variable device is provided inside the
piston.
6. The damping force variable shock absorber according to claim 1,
wherein the damping force variable device is provided outside the
piston.
7. The damping force variable shock absorber according to claim 1,
wherein the damping force variable device further includes an
actuator that generates thrust to the pilot valve in a
valve-closing direction.
8. The damping force variable shock absorber according to claim 2,
wherein the damping force variable device is provided inside the
piston.
9. The damping force variable shock absorber according to claim 2,
wherein the damping force variable device is provided outside the
piston.
10. The damping force variable shock absorber according to claim 2,
wherein the damping force variable device further includes an
actuator that generates thrust to the pilot valve in a
valve-closing direction.
11. The damping force variable shock absorber according to claim 3,
wherein the damping force variable device is provided inside the
piston.
12. The damping force variable shock absorber according to claim 3,
wherein the damping force variable device is provided outside the
piston.
13. The damping force variable shock absorber according to claim 3,
wherein the damping force variable device further includes an
actuator that generates thrust to the pilot valve in a
valve-closing direction.
14. The damping force variable shock absorber according to claim 4,
wherein the damping force variable device is provided inside the
piston.
15. The damping force variable shock absorber according to claim 4,
wherein the damping force variable device is provided outside the
piston.
16. The damping force variable shock absorber according to claim 4,
wherein the damping force variable device further includes an
actuator that generates thrust to the pilot valve in a
valve-closing direction.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application claims priority from Japanese Patent
Application No. 2015-122328 filed on Jun. 17, 2015, the entire
contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the present invention relate to a damping
force variable shock absorber.
[0004] 2. Description of the Related Art
[0005] In a two-wheeled motor vehicle, a wheel may be connected to
a vehicle body frame via a shock absorber. Examples of the shock
absorber include a damping force adjustment-type shock absorber
that controls flow of operating fluid (oil) to adjust damping
force. For example, JP-2009-281584-A discloses a shock
absorber.
[0006] In a damping force adjustment-type shock absorber, damping
force may be adjusted using the same control valve in a
compression-side stroke and an extension-side stroke. A damping
force balance between the compression-side stroke and the
extension-side stroke is determined by structural factors such as a
piston diameter and a piston rod diameter that give influence on an
amount of the operating fluid (oil) flowing in the shock absorber,
for example.
[0007] In such damping force adjustment-type shock absorber, since
the damping force balance between the compression-side stroke and
the extension-side stroke is determined by structural factors such
as the piston diameter and the piston rod diameter, it is difficult
to decrease or increase the damping force in any one of the
strokes.
[0008] Besides, when the damping force is controlled, a method of
electronically controlling the control valve using a solenoid or
the like may be used. However, when the control valve is
electronically controlled, a response delay or the like may
occur.
[0009] For example, in such damping force adjustment-type shock
absorber, the damping force is generated by a back pressure-type
main valve and a pressure control valve that generate damping force
by controlling the flow of the fluid. The pressure control valve
generates the damping force directly and adjusts internal pressure
of a pilot chamber to control valve-opening pressure of the main
valve. In this case, a damping force adjustment mechanism in which
one main valve, one pilot chamber, and one pressure control valve
are used for both the compression-side stroke and the
extension-side stroke is provided. Since only one set of these
members are present, the damping force adjustment mechanism can
have a compact configuration.
[0010] However, when the damping force is adjusted by
solenoid-based electronic control using one damping force
adjustment mechanism which includes one main valve, one pilot
chamber, and one pressure control valve, since fluid flows through
the same main valve, pilot chamber, and pressure control valve for
both the compression-side stroke and the extension-side stroke, the
damping force is adjusted in the same manner for both the
compression-side stroke and the extension-side stroke. Thus, it is
difficult for one damping force adjustment mechanism which uses
electronic control to realize different adjustments during the
compression-side stroke and the extension-side stroke as initial
settings.
[0011] Further, although separate damping force adjustment
mechanisms may be provided for respective strokes in order to
adjust the damping force in the compression-side stroke and the
extension-side stroke, the structure may become complex and the
manufacturing cost may increase.
SUMMARY OF THE INVENTION
[0012] An object of the present invention is to provide a compact
damping force variable shock absorber capable of realizing
different adjustments for a compression-side stroke and an
extension-side stroke as initial settings.
[0013] According to an embodiment, a damping force variable shock
absorber includes: a cylinder in which fluid is enclosed; a piston
slidably fitted into the cylinder; a piston rod having one end
connected to the piston and the other end extended outside the
cylinder; a rod-side fluid chamber partitioned by the piston and
provided closer to the other end in an axial direction of the
cylinder than the piston; a piston-side fluid chamber provided
closer to one end in the axial direction of the cylinder than the
piston; and a damping force variable device that controls flow of
fluid enclosed in the cylinder so that damping force can be
varied.
[0014] The damping force variable device includes: a main valve
that opens and closes to control the flow of the fluid caused by
sliding of the piston in the cylinder, thereby generating the
damping force; a pilot chamber into which a portion of the flow of
the fluid is introduced so that internal pressure is applied to the
main valve in a valve-closing direction; a pilot valve that opens
and closes to adjust the internal pressure of the pilot chamber;
and a communication passage that allows the pilot chamber or a
passage between the pilot chamber and the pilot valve to
communicate with the rod-side fluid chamber.
[0015] According to the damping force variable shock absorber of
the present invention, it is possible to provide a compact damping
force variable shock absorber capable of realizing different
adjustments during the compression-side stroke and the
extension-side stroke as initial settings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic diagram of a two-wheeled motor vehicle
having a damping force variable shock absorber according to a first
embodiment.
[0017] FIG. 2 is a longitudinal cross-sectional view of a first leg
of a front fork which is the damping force variable shock absorber
according to the first embodiment.
[0018] FIG. 3 is a longitudinal cross-sectional view schematically
illustrating a configuration of a supply and discharge portion
provided in a bottom portion of a partition wall member of the
damping force variable shock absorber according to the first
embodiment.
[0019] FIG. 4 is a longitudinal cross-sectional view of a damping
force variable device of a first leg of a front fork which is the
damping force variable shock absorber according to the first
embodiment.
[0020] FIG. 5 is a longitudinal cross-sectional view illustrating
flow of oil during a compression-side stroke of the damping force
variable device of the first leg of the front fork which is the
damping force variable shock absorber according to the first
embodiment.
[0021] FIG. 6 is a longitudinal cross-sectional view illustrating
the flow of the oil during an extension-side stroke of the damping
force variable device of the first leg of the front fork which is
the damping force variable shock absorber according to the first
embodiment.
[0022] FIG. 7 is an enlarged longitudinal cross-sectional view of a
main part of a pilot valve in case of failure of the damping force
variable device of the first leg of the front fork which is the
damping force variable shock absorber according to the first
embodiment.
[0023] FIG. 8 is a longitudinal cross-sectional view of a damping
force variable device of a first leg of a front fork which is a
damping force variable shock absorber according to a second
embodiment.
[0024] FIG. 9 is a longitudinal cross-sectional view illustrating
the flow of the oil during the compression-side stroke of the
damping force variable device of the first leg of the front fork
which is the damping force variable shock absorber according to the
second embodiment.
[0025] FIG. 10 is a longitudinal cross-sectional view illustrating
the flow of the oil during the extension-side stroke of the damping
force variable device of the first leg of the front fork which is
the damping force variable shock absorber according to the second
embodiment.
[0026] FIG. 11 is a hydraulic circuit diagram when the damping
force variable shock absorber of one of the first and second
embodiments is applied to another type of shock absorber.
[0027] FIG. 12 is a hydraulic circuit diagram when the damping
force variable shock absorber of one of the first and second
embodiments is applied to another type of shock absorber.
[0028] FIG. 13 is a hydraulic circuit diagram when the damping
force variable shock absorber of one of the first and second
embodiments is applied to another type of shock absorber.
[0029] FIG. 14 is a hydraulic circuit diagram when the damping
force variable shock absorber of one of the first and second
embodiments is applied to another type of shock absorber.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] Hereinafter, embodiments of the present invention will be
described with reference to the drawings.
First Embodiment
[0031] FIG. 1 is a schematic diagram of a two-wheeled motor vehicle
200 having a damping force variable shock absorber according to a
first embodiment. In the present embodiment, a front fork 10 is
illustrated as an example of a damping force variable shock
absorber. That is, the front fork 10 functions as a damping force
variable shock absorber.
[0032] As illustrated in FIG. 1, the two-wheeled motor vehicle 200
includes a vehicle body frame 210 that constitutes a part of a
vehicle body, a head pipe 211 attached to a front end of the
vehicle body frame 210, a front fork 10 provided on the head pipe
211, and a front wheel 213 attached to a lower end of the front
fork 10 with an axle 212 interposed.
[0033] The front fork 10 is disposed so as to sandwich the front
wheel 213 from left and right sides. Specifically, the front fork
10 includes a first leg 10a and a second leg 10b (not illustrated).
Only the first leg 10a disposed on the right side in a traveling
direction is illustrated in FIG. 1. Although an example in which
the first leg 10a is provided on the right side in the traveling
direction is illustrated, the first leg 10a may be provided on the
left side in the traveling direction. A specific configuration of
the front fork 10 will be described later.
[0034] The two-wheeled motor vehicle 200 includes a handlebar 214
attached to an upper portion of the front fork 10, a fuel tank 215
attached to a front upper portion of the vehicle body frame 210,
and an engine 216 disposed on a lower side of the fuel tank
215.
[0035] The two-wheeled motor vehicle 200 includes a seat 218
attached to a rear upper portion of the vehicle body frame 210, a
swing arm 219 attached to a lower portion of the vehicle body frame
210 so as to freely swing, a rear wheel 220 attached to a rear end
of the swing arm 219, and a pair of left and right rear suspensions
221 attached between the swing arm 219 and the vehicle body frame
210. The pair of rear suspensions 221 are disposed on left and
right sides of the rear wheel 220, respectively. Only a rear
suspension 221a disposed on the right side in the traveling
direction is illustrated in FIG. 1. Further, the two-wheeled motor
vehicle 200 includes a controller 222 that controls the entire
two-wheeled motor vehicle 200.
[0036] The vehicle body frame 210 is a frame that supports
functional members constituting the vehicle body such as the fuel
tank 215, the engine 216, and the like, for example. The head pipe
211 is an approximately cylindrical member. A handlebar rotation
shaft (not illustrated) provided integrally with the handlebar 214
and the front fork 10 is inserted into the head pipe 211, and the
head pipe 211 rotatably supports the handlebar rotation shaft.
[0037] The front wheel 213 is a vehicle wheel disposed on the front
side in the traveling direction of the vehicle body frame 210. The
handlebar 214 is a member that is disposed on the front side in the
traveling direction of the vehicle body frame 210 and is grasped by
a driver in order to steer the two-wheeled motor vehicle 200. The
fuel tank 215 is a container that is disposed on an upper side of
the vehicle body frame 210 so as to store fuel therein. The engine
216 is a driving source that supplies driving force for rotating
the rear wheel 220.
[0038] The seat 218 is a saddle-type seat which is disposed on the
upper side of the vehicle body frame 210 and on which the driver
rides. The swing arm 219 is a member of which the front end in the
traveling direction is swingably supported on the vehicle body
frame 210 and of which the rear end in the traveling direction
supports the rear wheel 220. The swing arm 219 swings about the
front end in the traveling direction so as to follow movement of
the rear wheel 220. The rear wheel 220 is a vehicle wheel disposed
on the rear side in the traveling direction of the vehicle body
frame 210.
[0039] The rear suspension 221 is a shock absorbing device that
suppresses shock applied to the rear wheel 220 due to unevenness on
a road surface from being transmitted to the vehicle body frame
210.
[0040] (Configuration of Front Fork 10)
[0041] Next, a configuration of the front fork 10 which is a
damping force variable shock absorber according to the first
embodiment will be described.
[0042] As described above, the front fork 10 includes the pair of
first and second legs 10a and 10b. In the front fork 10 illustrated
in FIG. 1, the first and second legs 10a and 10b have the same
configuration, for example. Thus, the configuration of the first
leg 10a will be described below.
[0043] FIG. 2 is a drawing illustrating a longitudinal
cross-section of the first leg 10a of the front fork 10 which is
the damping force variable shock absorber according to the first
embodiment. As illustrated in FIG. 2, the first leg 10a has such a
configuration that a portion of an inner tube 21 provided on a
lower end side thereof is inserted from below into an outer tube 20
provided on an upper end side thereof. The upper end side is a
vehicle body side and the lower end side is an axle side. The inner
tube 21 functions as a cylinder.
[0044] The front fork 10 illustrated in this example is an inverted
front fork in which the outer tube 20 is provided on the upper end
side and the inner tube 21 is provided on the lower end side. The
inner tube 21 is filled with oil, and the oil functions as
fluid.
[0045] An upper end side of the outer tube 20 is attached to the
vehicle body of the two-wheeled motor vehicle by an upper bracket
223 (see FIG. 1) and a lower bracket 224 (see FIG. 1). An upper end
of the outer tube 20 is closed by a cap bolt 22. A guide bush 23,
an oil seal 24, and a dust seal 25 that make sliding contact with
an outer circumference of the inner tube 21 are fitted to an inner
circumference of a lower end opening of the outer tube 20 in which
the inner tube 21 is inserted. Moreover, a guide bush 33 is fitted
to the outer circumference on the upper end side of the inner tube
21. Here, leakage of oil from the inner tube 21 is prevented by
sealing operation of the oil seal 24. Entering of dust from the
lower end opening of the outer tube 20 is prevented by sealing
operation of the dust seal 25. The guide bush 23 functions as a
first bush and the guide bush 33 functions as a second bush.
[0046] Moreover, the first leg 10a includes a bottomed cylindrical
partition wall member 27 of which a portion is provided inside the
inner tube 21. Moreover, a portion of the partition wall member 27
is fitted to an upper end of the inner tube 21. Moreover, the first
leg 10a includes a piston rod 26 of which an upper end is attached
to the cap bolt 22 of the outer tube 20 and which is slidably
inserted into the partition wall member 27. The piston rod 26 is
suspended toward the axle side from an axial center in the outer
tube 20. Moreover, the piston rod 26 is inserted from above into
the inner tube 21 and passes through a bottom portion 27a of the
partition wall member 27.
[0047] Moreover, the first leg 10a includes a piston 70 which is
provided at a lower end of the piston rod 26 so as to freely slide
along an inner circumference of the inner tube 21. A solenoid 90
that constitutes an actuator of the damping force variable device
50, the piston 70, and a spring collar 28 are fixed to the lower
end of the piston rod 26 by upper and lower nuts 29 and 30. Major
parts of the damping force variable device 50 are incorporated into
the piston 70. The piston rod 26 is hollow, and a power cord 31 for
supplying electric power to the solenoid 90 is inserted into the
piston rod 26. Moreover, a rebound spring 32 is wound above the nut
29 of the piston rod 26.
[0048] A lower end of the inner tube 21 is attached to a front axle
of the two-wheeled motor vehicle with an axle attachment member
(not illustrated) interposed. The portion of the inner tube 21
inserted into the outer tube 20 is held by the guide bush 33 fitted
to the outer circumference at the upper end of the inner tube 21
and the guide bush 23 fitted to the inner circumference at the
lower end of the outer tube 20 so as to be slidable in an up-down
direction in relation to the outer tube 20.
[0049] An annular oil chamber S3 of which upper and lower ends are
sealed by the guide bush 33 and the guide bush 23, respectively, is
formed in a gap between the inner circumference of the outer tube
20 and the outer circumference of the inner tube 21. The piston rod
26 has a smaller cross-sectional area than a cross-sectional area
of the annular oil chamber S3. Oil is enclosed in the annular oil
chamber S3. The annular oil chamber S3 functions as an annular
fluid chamber.
[0050] Moreover, the first leg 10a includes an oil storage chamber
Re which is partitioned by the partition wall member 27 inside the
inner tube 21 and is formed closer to the upper end side than the
partition wall member 27 and an oil chamber S0 which is partitioned
by the partition wall member 27 inside the inner tube 21 and is
formed closer to the lower end side than the partition wall member
27. Moreover, the first leg 10a includes a rod-side oil chamber S2
which is partitioned in the piston 70 inside the oil storage
chamber S0 and is formed closer to the upper end side than the
piston 70 and a piston-side oil chamber 51 which is partitioned in
the piston 70 inside the oil chamber S0 and is formed closer to the
lower end side than the piston 70. Moreover, a communication hole
21a that allows the annular oil chamber S3 and the rod-side oil
chamber S2 to communicate with each other is formed in the inner
tube 21. The oil storage chamber Re functions as a fluid storage
chamber, the oil chamber S0 functions as a fluid chamber, the
rod-side oil chamber S2 functions as a rod-side fluid chamber, and
the piston-side oil chamber 51 functions as a piston-side fluid
chamber.
[0051] Moreover, a rod guide 34 through which the piston rod 26
passes is fitted to an axial center of the bottom portion 27a of
the partition wall member 27 fitted to the inner circumference at
the upper end of the inner tube 21. The piston rod 26 is held by
the rod guide 34 so as to be slidable in the up-down direction.
[0052] The piston 70 engages with the inner circumference of the
inner tube 21 so as to be slidable in the up-down direction. An
inner side of the outer tube 20 and the inner tube 21 is
partitioned vertically by the partition wall member 27, and a space
disposed closer to the upper end side than the partition wall
member 27 is an oil storage chamber Re that functions as a
reservoir. The oil storage chamber Re includes an oil storage
portion Ro in which oil is supplied and discharged in relation to
the rod-side oil chamber S2 with the partition wall member 27 as a
boundary and a gas storage portion Rg in which gas such as air is
filled.
[0053] Here, a supply and discharge portion 40 that enables oil to
be supplied and discharged between the oil storage portion Ro and
the rod-side oil chamber S2 under the partition wall member 27 is
provided in the bottom portion 27a of the bottomed cylindrical
partition wall member 27. FIG. 3 is a cross-sectional view
schematically illustrating a configuration of the supply and
discharge portion 40 provided in the bottom portion 27a of the
partition wall member 27. As illustrated in FIG. 3, the supply and
discharge portion 40 includes an oil passage 40a, an oil passage
40b, a check valve 40c, and a throttle 40d.
[0054] The oil passages 40a and 40b allow the oil storage portion
Ro of the oil storage chamber Re and the rod-side oil chamber S2 to
communicate with each other. The check valve 40c is provided in the
oil passage 40a. The check valve 40c allows flow of the oil from
the oil storage portion Ro to the rod-side oil chamber S2 and
blocks the flow of the oil from the rod-side oil chamber S2 to the
oil storage portion Ro. The throttle 40d is provided in the oil
passage 40b. The throttle 40d limits the flow of the oil between
the oil storage portion Ro and the rod-side oil chamber S2.
[0055] A suspension spring 35 is disposed between the spring collar
28 and the bottom portion (not illustrated) in the inner tube
21.
[0056] Next, a configuration of the damping force variable device
50 will be described with reference to FIG. 4.
[0057] FIG. 4 is a drawing illustrating a longitudinal
cross-section of the damping force variable device 50 of the first
leg 10a of the front fork 10 which is the damping force variable
shock absorber according to the first embodiment. FIG. 4
illustrates a portion of the inner tube 21 for the sake of
convenience.
[0058] The major parts of the damping force variable device 50 are
incorporated into the piston 70. The piston 70 is divided into two
parts, an upper piston member 71 and a lower piston member 72.
Although an example in which the major parts of the damping force
variable device 50 are incorporated into the piston 70 has been
illustrated, the damping force variable device 50 is not limited to
this, and the major parts thereof may not be incorporated into the
piston 70 but the damping force variable device 50 may be provided
separately.
[0059] The damping force variable device 50 is formed by assembling
a valve stopper 52, an extension-side outlet check valve 53, the
lower piston member 72, a compression-side inlet check valve 54, an
extension-side inlet check valve 55, the upper piston member 71, a
compression-side outlet check valve 56, a valve stopper 57, a valve
seat member 58, and the solenoid 90 sequentially in a rod axis
direction from the lower side.
[0060] A rod portion 58a protrudes integrally from the axial center
of the valve seat member 58 toward the lower side. The rod portion
58a passes through a center in a radial direction of the valve
stopper 57, the compression-side outlet check valve 56, the upper
piston member 71, the extension-side inlet check valve 55, the
compression-side inlet check valve 54, the lower piston member 72,
the extension-side outlet check valve 53, and the valve stopper 52.
The nut 30 is screwed on a lower end of the rod portion 58a.
[0061] A main valve member 59 fitted to an outer circumference of
the rod portion 58a of the valve seat member 58 is accommodated in
a concave portion 72a of the lower piston member 72. An
approximately cylindrical main valve 60 is fitted and held on an
outer circumference of the main valve member 59 so as to be
slidable in the up-down direction. An annular pilot chamber 61
partitioned by the main valve member 59 is formed in a portion of
the concave portion 72a on a back surface side (the lower end side
in FIG. 4) of the main valve 60. The pilot chamber 61 introduces a
portion of the flow of the oil therein and applies internal
pressure to the main valve 60 in a valve-closing direction (toward
the upper end side). A plate spring 62 biases the main valve 60 in
an upward direction (toward the valve-closing side) so that the
main valve 60 sits on a lower surface (a sitting surface) of the
upper piston member 71 is accommodated in the pilot chamber 61.
[0062] A passage 63 is formed in the concave portion 72a of the
lower piston member 72 between an inner circumference of the
concave portion 72a and the outer circumference of the main valve
60. The passage 63 communicates with the pilot chamber 61 through
an oil hole 60a formed in the main valve 60.
[0063] A space 64 is formed in an inner circumference of a lower
portion of the upper piston member 71. Moreover, an oil hole 71a
that passes in the up-down direction and an oblique oil hole 71b
are formed in the upper piston member 71. Here, the oil hole 71a is
normally open to the rod-side oil chamber S2 (see FIG. 2) in the
inner tube 21 and is selectively opened and closed by the
extension-side inlet check valve 55. Moreover, the oil hole 71b is
normally open to the space 64 and is selectively opened and closed
by the compression-side outlet check valve 56.
[0064] A space 65 is formed in an inner circumference of a lower
portion of the lower piston member 72. Moreover, an oil hole 72b
that passes in the up-down direction and an oblique oil hole 72c
are formed in the lower piston member 72. Here, the oil hole 72b is
normally open to the piston-side oil chamber S1 (see FIG. 2) formed
in the inner tube 21 and is selectively opened and closed by the
compression-side inlet check valve 54. Moreover, the oil hole 72c
is normally open to the space 65 and is selectively opened and
closed by the extension-side outlet check valve 53.
[0065] Further, a communication passage 72d that allows the pilot
chamber 61 and the rod-side oil chamber S2 to communicate with each
other is formed in the lower piston member 72. As illustrated in
FIG. 4, the communication passage 72d is formed as a communication
hole that allows the pilot chamber 61 and the rod-side oil chamber
S2 to communicate with each other, for example. One end of the
communication passage 72d is open to a side surface of the lower
piston member 72 between a distance collar 66 described later and a
sliding sealing member 73 provided below the distance collar
66.
[0066] The communication passage 72d is not limited to a
configuration in which the communication passage 72d allows the
pilot chamber 61 and the rod-side oil chamber S2 to communicate
with each other. The communication passage 72d may allow a passage
between the pilot chamber 61 and a pilot valve 110 described later
to communicate with the rod-side oil chamber S2.
[0067] The passage between the pilot chamber 61 and the pilot valve
110 corresponds to a portion of an upstream-side pilot passage 171
but does not include the pilot chamber 61 and the oil hole 60a of
the main valve 60 which constitute a part of the upstream-side
pilot passage 171. In a normal state, the passage between the pilot
chamber 61 and the pilot valve 110 is a passage between the pilot
chamber 61 and a pilot valve body 99. Specifically, the passage
between the pilot chamber 61 and the pilot valve 110 is a passage
which includes an oil hole (not illustrated) that is formed in the
main valve member 59 and communicates with the pilot chamber 61, an
oil hole 58d, and an oil hole 58c.
[0068] Besides, in case of failure in which supply of current to
the solenoid 90 is interrupted and the solenoid 90 does not
generate thrust, the passage between the pilot chamber 61 and the
pilot valve 110 is a passage between the pilot chamber 61 and a
fail-safe valve 103 described later. Specifically, the passage
includes an oil hole (not illustrated) that is formed in the main
valve member 59 and communicates with the pilot chamber 61, the oil
hole 58d, the oil hole 58c, a space 100, and an oil hole 99a.
[0069] A portion of the sliding sealing member 73 is fitted to a
groove 74 formed in a side surface of the lower piston member 72.
An outer circumferential surface of the sliding sealing member 73
protrudes toward an outer circumference side (an outer side in the
radial direction) further than an outer circumferential surface of
the lower piston member 72 and is in contact with an inner
circumferential surface of the inner tube 21 so as to be
slidable.
[0070] A gap 75 is formed between the inner tube 21 and the piston
70 on a side closer to the upper end side than the sliding sealing
member 73. This gap 75 communicates with the rod-side oil chamber
S2 (see FIG. 2). Moreover, a gap 76 is formed between the inner
tube 21 and the piston 70 on a side closer to the lower end side
than the sliding sealing member 73. This gap 76 communicates with
the piston-side oil chamber S1 (see FIG. 2). The space in the inner
tube 21 on the lower end side of the partition wall member 27 is
partitioned into the rod-side oil chamber S2 and the piston-side
oil chamber S1 by the sliding sealing member 73 that forms a
portion of the piston 70.
[0071] One end of the communication passage 72d is open to the gap
75. At least one communication passage 72d may be provided. For
example, a plurality of communication passages 72d may be formed in
a circumferential direction of the lower piston member 72. By
changing the hold diameter and the number of holes in the
communication passage 72d, it is possible to arbitrarily change the
decrease in the pressure of the pilot chamber 61 and the passage
between the pilot chamber 61 and the pilot valve 110.
[0072] A concave portion 58b of which an upper side is open is
formed in an upper portion of the axial center of the valve seat
member 58. An oil hole 58c is formed so as to extend from the
concave portion 58b toward the lower side along the axial center of
the rod portion 58a. An oil hole 58d is formed so as to extend from
the lower end of the oil hole 58c toward an outer side in the
radial direction at a right angle. The oil hole 58d communicates
with the pilot chamber 61 through an oil hole (not illustrated)
formed in the main valve member 59 in the radial direction.
[0073] A plurality of oil holes 59a that passes in the axial
direction is formed in the main valve member 59. Upper ends of the
oil holes 59a communicate with the oil hole 71b of the upper piston
member 71 through the space 64 of the upper piston member 71, and
lower ends of the oil holes 59a communicate with the oil hole 72c
of the lower piston member 72 through the space 65 of the lower
piston member 72.
[0074] A gap 67 extending in the rod axis direction is formed
between the upper piston member 71 and the lower piston member 72
by a ring-shaped distance collar 66 fitted to the outer
circumferences of the upper piston member 71 and the lower piston
member 72. The compression-side inlet check valve 54 and the
extension-side inlet check valve 55 are provided in the gap 67. The
compression-side inlet check valve 54 and the extension-side inlet
check valve 55 are biased by a plate spring 68 interposed between
the valves 54 and 55, in a direction in which the oil hole 72b of
the lower piston member 72 and the oil hole 71a of the upper piston
member 71 are closed, respectively.
[0075] Next, a configuration of the solenoid 90 will be
described.
[0076] The solenoid 90 has a cylindrical case 91 of which the inner
circumference of the lower end opening engages with the outer
circumference of the valve seat member 58. Two bottomed cylindrical
cores 92 and 93, an annular coil 94, a plunger 95 accommodated in
the cores 92 and 93, a hollow operating rod 96 that passes through
an axial center of the plunger 95, and the like are accommodated in
the case 91. The operating rod 96 has both ends in the up-down
direction being supported by the cylindrical guide bushes 97 and 98
so as to be movable in the up-down direction. A pilot valve 110
that includes the pilot valve body 99 and the fail-safe valve 103
is provided in an outer circumference of a lower end of the
operating rod 96 that faces an inside of the concave portion 58b of
the valve seat member 58. Thus, the damping force variable device
50 includes the solenoid 90 which is an actuator that generates
thrust in the valve-closing direction (toward the lower end side)
with respect to the pilot valve 110.
[0077] The pilot valve body 99 is fitted to the inner circumference
of the concave portion 58b of the valve seat member 58 so as to be
movable in the up-down direction. The pilot valve body 99 opens and
closes the oil hole 58c by selectively sitting on a tapered valve
seat 58e formed on an upper end of the oil hole 58c that is formed
at the axial center of the valve seat member 58. In addition to
generating the damping force with the aid of the main valve 60, the
damping force may be generated by the pilot valve 110 that includes
the pilot valve body 99 and the fail-safe valve 103.
[0078] Here, a space 100 partitioned by the pilot valve body 99 is
formed in the concave portion 58b of the valve seat member 58.
Moreover, a spring 101 that biases the pilot valve body 99 in the
valve-opening direction (toward the upper end side in FIG. 4) is
accommodated in the space 100.
[0079] Here, the space 100 formed in the valve seat member 58
communicates with the pilot chamber 61 through the oil holes 58c
and 58d of the valve seat member 58 and an oil hole (not
illustrated) formed in the main valve member 59. Moreover, an oil
hole 99a is formed in the pilot valve body 99. The oil hole 99a is
normally open to the space 100.
[0080] A recessed space 102 is formed between the valve seat member
58 and an end surface of the core 92 of the solenoid 90. The
fail-safe valve 103 that selectively opens and closes the oil hole
99a of the pilot valve body 99 is provided in the space 102. The
fail-safe valve 103 is held on an outer circumference of the
operating rod 96 so as to be movable in the rod axis direction and
is biased in the valve-closing direction (toward the lower end side
in FIG. 4) by the spring 104 accommodated in the space 102. A
spring constant of the spring 104 is set to be smaller than a
spring constant of the spring 101 that biases the pilot valve body
99 in the valve-opening direction.
[0081] An oil hole 58f is formed in the valve seat member 58 so as
to pass in the up-down direction. The space 102 communicates with
the space 64 of the upper piston member 71 through the oil hole
58f, a cylindrical passage 105 formed between the valve stopper 57
and the valve seat member 58, and a cylindrical passage 106 formed
between the upper piston member 71 and the rod portion 58a of the
valve seat member 58.
[0082] In the damping force variable device 50 having such a
configuration, the oil hole 72b of the lower piston member 72, the
gap 67, the space 64 of the upper piston member 71, and the oil
hole 71b of the upper piston member 71 form the main passage 150
during a compression-side stroke. The compression-side inlet check
valve 54, the main valve 60, and the compression-side outlet check
valve 56 are provided in the main passage 150.
[0083] Moreover, the oil hole 71a of the upper piston member 71,
the gap 67, the oil holes 59a of the main valve member 59, the
space 65 of the lower piston member 72, and the oil hole 72c of the
lower piston member 72 form the main passage 160 during an
extension-side stroke. The extension-side inlet check valve 55, the
main valve 60, and the extension-side outlet check valve 53 are
provided in the main passage 160.
[0084] The oil hole 60a of the main valve 60, the pilot chamber 61,
the oil hole (not illustrated) formed in the main valve member 59,
the oil holes 58d and 58c formed in the valve seat member 58, the
space 100 formed by the pilot valve body 99 and the valve seat
member 58, the oil hole 99a formed in the pilot valve body 99, the
space 102 formed in the core 92 of the solenoid 90, the oil hole
58f formed in the valve seat member 58, the passage 105 formed
between the valve stopper 57 and the valve seat member 58, the
passage 106 connected to the passage 105, and the space 64 of the
upper piston member 71 form the pilot passage 170 during the
compression-side stroke and the extension-side stroke.
[0085] Here, the pilot passage 170 can be divided into an
upstream-side pilot passage 171 and a downstream-side pilot passage
172, for example. In the normal state, the upstream-side pilot
passage 171 includes the oil hole 60a of the main valve 60, the
pilot chamber 61, the oil hole (not illustrated) formed in the main
valve member 59 to communicate with the pilot chamber 61, the oil
hole 58d, and the oil hole 58c, for example. The downstream-side
pilot passage 172 includes the space 100 formed by the pilot valve
body 99 and the valve seat member 58, the oil hole 99a formed in
the pilot valve body 99, the space 102 formed in the core 92 of the
solenoid 90, the oil hole 58f formed in the valve seat member 58,
the passage 105 formed between the valve stopper 57 and the valve
seat member 58, the passage 106 connected to the passage 105, and
the space 64 of the upper piston member 71.
[0086] In case of the failure described later, the upstream-side
pilot passage 171 includes the oil hole 60a of the main valve 60,
the pilot chamber 61, the oil hole (not illustrated) formed in the
main valve member 59 to communicate with the pilot chamber 61, the
oil hole 58d, the oil hole 58c, the space 100 formed by the pilot
valve body 99 and the valve seat member 58, and the oil hole 99a
formed in the pilot valve body 99. Moreover, in case of the
failure, the downstream-side pilot passage 172 includes the space
102 formed in the core 92 of the solenoid 90, the oil hole 58f
formed in the valve seat member 58, the passage 105 formed between
the valve stopper 57 and the valve seat member 58, the passage 106
connected to the passage 105, and the space 64 of the upper piston
member 71, for example.
[0087] The pilot valve 110 including the pilot valve body 99 and
the fail-safe valve 103 is provided in the pilot passage 170. In
the normal state, an internal pressure of the pilot chamber 61 and
the passage between the pilot chamber 61 and the pilot valve 110 is
adjusted by opening and closing of the pilot valve body 99 in
relation to the valve seat member 58. In case of the failure, the
internal pressure of the pilot chamber 61 and the passage between
the pilot chamber 61 and the pilot valve 110 is adjusted by opening
and closing of the fail-safe valve 103 in relation to the pilot
valve body 99. In any case, the internal pressure of the pilot
chamber 61 and the passage between the pilot chamber 61 and the
pilot valve 110 is adjusted by opening and closing of the pilot
valve 110.
[0088] Moreover, the communication passage 72d that allows the
pilot chamber 61 and the rod-side oil chamber S2 to communicate
with each other guides a portion of the oil in the pilot chamber 61
toward the rod-side oil chamber S2 during the compression-side
stroke. That is, when the communication passage 72d is provided,
increase in the pressure in the pilot chamber 61 is suppressed as
compared to when the communication passage 72d is not provided.
[0089] On the other hand, during the extension-side stroke, a
portion of the oil inside the rod-side oil chamber S2 flows from
the rod-side oil chamber S2 into the pilot chamber 61 through the
communication passage 72d.
[0090] (Operation of Front Fork 10) Next, operation during the
compression-side stroke and the extension-side stroke of the first
leg 10a having such a configuration will be described with
reference to FIGS. 5 and 6. FIG. 5 is a longitudinal
cross-sectional view illustrating the flow of the oil during the
compression-side stroke of the damping force variable device 50 of
the first leg 10a of the front fork 10 which is the damping force
variable shock absorber according to the first embodiment. FIG. 6
is a longitudinal cross-sectional view illustrating the flow of the
oil during extension-side stroke of the damping force variable
device 50 of the first leg 10a of the front fork 10 which is the
damping force variable shock absorber according to the first
embodiment. FIGS. 5 and 6 illustrate a portion of the inner tube 21
for the sake of convenience.
[0091] (Compression-Side Stroke)
[0092] First, the operation during the compression-side stroke will
be described with reference to FIG. 5.
[0093] When the front wheel 213 of a two-wheeled motor vehicle 200
moves upward and downward following unevenness on a road surface
during riding the two-wheeled motor vehicle 200, the outer tube 20
and the inner tube 21 that suspend the front wheel do telescopic
motion. In compression-side stroke in which the inner tube 21 moves
upward in relation to the outer tube 20, the oil in the piston-side
oil chamber 51 is compressed by the piston 70 and pressure therein
increases.
[0094] Moreover, the oil in the piston-side oil chamber 51 flows
into the rod-side oil chamber S2 through the main passage 150
during compression-side stroke.
[0095] Specifically, as indicated by solid-line arrows in FIG. 5,
the oil flows from the piston-side oil chamber 51 to pass through
the oil hole 72b of the lower piston member 72 to push and open the
compression-side inlet check valve 54 while resisting biasing force
of the plate spring 68 to flow into the gap 67. Moreover, the oil
flowing into the gap 67 pushes and opens the main valve 60 with
pressure thereof while resisting force in the valve-closing
direction (toward the upper end side) of back pressure of the plate
spring 68 and the pilot chamber 61. Moreover, the oil passes from
the gap 67 through the oil hole 71b of the upper piston member 71
via the space 64 to push and open the compression-side outlet check
valve 56 to flow into the rod-side oil chamber S2. In this case,
with flow resistance of the oil when passing through the main valve
60, a compression-side damping force is generated in the first leg
10a.
[0096] On the other hand, a portion of the oil flowing from the
piston-side oil chamber 51 into the gap 67 through the oil hole 72b
of the lower piston member 72 joins the oil flowing in the main
passage 150 through the pilot passage 170. Moreover, a portion of
the oil flowing through the pilot passage 170 flows from the pilot
chamber 61 into the rod-side oil chamber S2 through the
communication passage 72d.
[0097] Specifically, as indicated by broken-line arrows in FIG. 5,
a portion of the oil flowing from the piston-side oil chamber S1
toward the gap 67 through the oil hole 72b of the lower piston
member 72 passes through the oil hole 60a of the main valve 60 from
the passage 63 on the outer circumference of the main valve 60 to
flow into the pilot chamber 61.
[0098] As indicated by the broken-line arrows in FIG. 5, a portion
of the oil flowing into the pilot chamber 61 flows from the pilot
chamber 61 into the space 100 of the valve seat member 58 through
the oil hole (not illustrated) of the main valve member 59, the oil
holes 58d and 58c of the valve seat member 58, and the gap between
the pilot valve body 99 and the valve seat 58e. Moreover, the oil
flowing into the space 100 of the valve seat member 58 passes
through the oil hole 99a of the pilot valve body 99 to push and
open the fail-safe valve 103 to flow into the space 102 of the core
92.
[0099] Here, the fail-safe valve 103 may be designed so as to be
opened by being spaced from the pilot valve body 99 immediately
when oil flows due to a function of the check valve only by setting
biasing force of the spring 104 low. Alternatively, a flow
resistance may occur between the fail-safe valve 103 and the pilot
valve body 99 when the fail-safe valve 103 is opened by being
spaced from the pilot valve body 99 while resisting the biasing
force of the spring 104 by setting the biasing force of the spring
104 to a certain value.
[0100] The oil flowing into the space 102 passes through the oil
hole 58f of the valve seat member 58 and the passages 105 and 106
to flow into the space 64 of the upper piston member 71 to join the
oil flowing through the main passage 150. The joined oil flows into
the rod-side oil chamber S2.
[0101] On the other hand, as indicated by a one-dot-chain-line
arrow in FIG. 5, a remaining portion of the oil flowing into the
pilot chamber 61 flows into the gap 75 between the inner tube 21
and the piston 70 through the communication passage 72d. Since the
gap 75 communicates with the rod-side oil chamber S2, the remaining
portion of the oil flowing into the pilot chamber 61 flows into the
rod-side oil chamber S2. In this connection, a passage including
the communication passage 72d and the gap 75 is referred to as a
bypass passage 180.
[0102] As a result, the internal pressure (the back pressure) of
the pilot chamber 61 during compression-side stroke decreases, and
thus force that presses the main valve 60 in the valve-closing
direction (toward the upper end side) decreases. When the
communication passage 72d is provided, the damping force during
compression-side stroke is low as compared to when the
communication passage 72d is not provided. Thus, it is possible to
adjust the damping force to be relatively low as an initial setting
during compression-side stroke.
[0103] Here, an opening degree of the main valve 60 that generates
a main damping force in the damping force variable device 50 of the
first leg 10a of the front fork 10 is influenced by the internal
pressure (the back pressure) of the pilot chamber 61. Thus, the
internal pressure of the pilot chamber 61 may be adjusted by
methods other than the method of allowing the oil flowing into the
pilot chamber 61 to flow into the rod-side oil chamber S2 with the
aid of the communication passage 72d.
[0104] By driving the solenoid 90 to move the operating rod 96 and
the pilot valve body 99 provided on an outer circumference at the
lower end of the operating rod 96 in the rod axis direction to
change the opening degree of the pilot valve body 99 in relation to
the valve seat member 58, it is possible to adjust the flow
resistance of the oil passing through the gap between the pilot
valve body 99 and the valve seat member 58 and thereby to adjust
the internal pressure of the pilot chamber 61 and the passage
between the pilot chamber 61 and the pilot valve 110. That is, the
solenoid 90 and the pilot valve body 99 control the internal
pressure of the pilot chamber 61 and the passage between the pilot
chamber 61 and the pilot valve 110.
[0105] In this manner, by adjusting the back pressure of the pilot
chamber 61 with the aid of the solenoid 90 and thereby adjusting
the opening of the main valve 60, it is possible to adjust the
damping force generated by the flow resistance of the oil passing
through the main valve 60. Specifically, when the opening degree of
the pilot valve body 99 in relation to the valve seat member 58 is
decreased, the back pressure of the pilot chamber 61 increases, the
opening degree of the main valve 60 decreases, and thus the damping
force increases. On the other hand, when the opening degree of the
pilot valve body 99 in relation to the valve seat member 58 is
increased, the back pressure of the pilot chamber 61 decreases, the
opening degree of the main valve 60 increases, and thus the damping
force decreases.
[0106] Moreover, by incorporating the spring 101 into a biasing
means that biases the pilot valve body 99 in the valve-opening
direction, it is possible to freely set the valve-opening pressure
of the pilot valve body 99 by adjusting a spring constant of the
spring 101. Further, when the biasing means includes oil pressure,
it is possible to continuously change the valve-opening pressure of
the pilot valve body 99. In the present embodiment, since the
biasing means includes the spring 101 and the oil pressure, it is
possible to continuously change the valve-opening pressure of the
pilot valve body 99 and to broaden the setting width.
[0107] Here, in the compression-side stroke, an amount of the oil
corresponding to a volume of the piston rod 26 advancing into the
inner tube 21 is delivered from the rod-side oil chamber S2 in the
inner tube 21 to the annular oil chamber S3 illustrated in FIG. 2
through the communication hole 21a. In this case, since an increase
in volume .DELTA.V1 (supply amount) of the annular oil chamber S3
is larger than an increase in volume .DELTA.V2 of the piston rod
26, a deficit ".DELTA.V1-.DELTA.V2" in a supply amount of the oil
supplied to the annular oil chamber S3 is supplied from the oil
storage portion Ro to the rod-side oil chamber S2. Supply of a
deficit amount of the oil is performed by the supply and discharge
portion 40 illustrated in FIG. 3, which is formed in the bottom
portion of the partition wall member 27 so as to enable oil to be
supplied and discharged between the oil storage portion Ro and the
rod-side oil chamber S2.
[0108] (Extension-Side Stroke)
[0109] Next, the operation during extension-side stroke will be
described with reference to FIG. 6.
[0110] In the extension-side stroke in which the inner tube 21
moves downward in relation to the outer tube 20, the oil in the
rod-side oil chamber S2 is compressed by the piston 70 and the
pressure thereof increases.
[0111] Then, the oil in the rod-side oil chamber S2 flows into the
piston-side oil chamber 51 through the main passage 160 during the
extension-side stroke.
[0112] Specifically, as indicated by solid-line arrows in FIG. 6,
the oil flows from the rod-side oil chamber S2 to pass through the
oil hole 71a of the upper piston member 71 to push and open the
extension-side inlet check valve 55 while resisting the biasing
force of the plate spring 68 to flow into the gap 67. Moreover, the
oil flowing into the gap 67 pushes and opens the main valve 60 with
the pressure thereof while resisting the force in the valve-closing
direction of the plate spring 68 and the back pressure of the pilot
chamber 61 to flow from the gap 67 through the oil holes 59a of the
main valve member 59 and the oil hole 72c of the lower piston
member 72 to push and open the extension-side outlet check valve 53
to flow into the piston-side oil chamber S1. In this case, with the
flow resistance of the oil when passing through the main valve 60,
an extension-side damping force is generated in the damping force
variable device 50.
[0113] On the other hand, a portion of the oil flowing from the
rod-side oil chamber S2 into the gap 67 through the oil hole 71a of
the upper piston member 71 passes through the pilot passage 170
including the pilot chamber 61 similarly to the case of the
compression-side stroke. A operation method and a function of the
pilot valve body 99 and the fail-safe valve 103 in relation to the
flow of the oil in the pilot passage 170 in the extension-side
stroke are the same as those of the compression-side stroke. The
oil flowing through the pilot passage 170 joins the oil flowing
through the main passage 160. Here, the flow of the oil in the
pilot passage 170 is depicted by broken-line arrows in FIG. 6. The
joined oil flows into the piston-side oil chamber S1.
[0114] Moreover, a portion of the oil in the rod-side oil chamber
S2 flow from the rod-side oil chamber S2 into the pilot chamber 61
through the communication passage 72d. That is, the flow of the oil
in the rod-side oil chamber S2 branches into two passages, the oil
flowing along the main passage 160 indicated by the solid-line
arrows in FIG. 6 and the oil flowing along the bypass passage 180
indicated by a one-dot-chain-line arrow in FIG. 6, near the
compression-side outlet check valve 56a.
[0115] The oil flowing through the bypass passage 180 flows into
the communication passage 72d through the gap 75 between the piston
70 and the inner tube 21 to flow into the pilot chamber 61.
[0116] Here, pressure of the oil flowing into the pilot chamber 61
through the main passage 160 is reduced by flow resistance of a gap
between the extension-side inlet check valve 55 and the upper
piston member 71 and flow resistance of the oil hole 60a in
relation to internal pressure of the rod-side oil chamber S2. On
the other hand, pressure of the oil flowing into the pilot chamber
61 through the bypass passage 180 is reduced by flow resistance of
the communication passage 72d in relation to the internal pressure
of the rod-side oil chamber S2. Thus, in the first leg 10a, by
controlling the sum of the flow resistance of the gap between the
extension-side inlet check valve 55 and the upper piston member 71
and the flow resistance of the oil hole 60a to be equal to the flow
resistance of the communication passage 72d, an increase in the
internal pressure of the pilot chamber 61 due to the oil flowing
into the pilot chamber 61 through the bypass passage 180 can be
suppressed.
[0117] Here, the opening degree of the main valve 60 that generates
the main damping force in the damping force variable device 50 of
the first leg 10a of the front fork 10 is influenced by the
internal pressure (the back pressure) of the pilot chamber 61
similarly to the compression-side stroke.
[0118] By driving the solenoid 90 to move the operating rod 96 and
the pilot valve body 99 provided on the outer circumference at the
lower end of the operating rod 96 in the rod axis direction to
change the opening degree of the pilot valve body 99 in relation to
the valve seat member 58, it is possible to adjust the flow
resistance of the oil passing through the gap between the pilot
valve body 99 and the valve seat member 58 and thereby to adjust
the internal pressure of the pilot chamber 61 and the passage
between the pilot chamber 61 and the pilot valve 110. That is, the
solenoid 90 and the pilot valve body 99 control the internal
pressure of the pilot chamber 61 and the passage between the pilot
chamber 61 and the pilot valve 110.
[0119] In this manner, by adjusting the back pressure of the pilot
chamber 61 with the aid of the solenoid 90 and thereby adjusting
the opening of the main valve 60, it is possible to adjust the
damping force generated by the flow resistance of the oil passing
through the main valve 60. Specifically, when the opening degree of
the pilot valve body 99 in relation to the valve seat member 58 is
decreased, the back pressure of the pilot chamber 61 increases, the
opening degree of the main valve 60 decreases, and thus the damping
force increases. On the other hand, when the opening degree of the
pilot valve body 99 in relation to the valve seat member 58 is
increased, the back pressure of the pilot chamber 61 decreases, the
opening degree of the main valve 60 increases, and thus the damping
force decreases.
[0120] Moreover, by incorporating the spring 101 into the biasing
means that biases the pilot valve body 99 in the valve-opening
direction, it is possible to freely set the valve-opening pressure
of the pilot valve body 99 by adjusting the spring constant of the
spring 101. Further, when the biasing means includes oil pressure,
it is possible to continuously change the valve-opening pressure of
the pilot valve body 99. In the present embodiment, since the
biasing means includes the spring 101 and the oil pressure, it is
possible to continuously change the valve-opening pressure of the
pilot valve body 99 and to broaden the setting width.
[0121] Here, in the extension-side stroke, an amount of oil
corresponding to the volume of the piston rod 26 exiting from the
inner tube 21 is delivered from the annular oil chamber S3
illustrated in FIG. 2 to the rod-side oil chamber S2 through the
communication hole 21a. In this case, since a decrease in volume
.DELTA.V3 (discharge amount) of the annular oil chamber S3 is
larger than a decrease in volume .DELTA.V4 of the piston rod 26, a
surplus ".DELTA.V3-.DELTA.V4" out of the discharge amount of oil
discharged from the annular oil chamber S3 is discharged from the
rod-side oil chamber S2 to the oil storage portion Ro. Discharge of
a surplus amount of the oil is performed by the supply and
discharge portion 40 illustrated in FIG. 3, which is formed in the
bottom portion of the partition wall member 27 so as to enable the
oil to be supplied and discharged between the oil storage portion
Ro and the rod-side oil chamber S2.
[0122] (In Case of Failure)
[0123] Here, the operation in case of the failure in which the
solenoid 90 breaks down due to some causes and does not operate
normally will be described. FIG. 7 is a drawing illustrating an
enlarged longitudinal cross-section of a main part of the pilot
valve 110 of the damping force variable device 50 of the first leg
10a of the front fork 10 which is the damping force variable shock
absorber according to the first embodiment.
[0124] In case of the failure in which the solenoid 90 does not
operates normally, the thrust (electromagnetic force) that moves
the pilot valve 110 in the valve-closing direction (toward the
lower end side) while resisting the spring 101 that biases the
pilot valve 110 in the valve-opening direction (toward the upper
end side) is not generated. Here, the spring constant of the spring
101 that biases the pilot valve 110 in the valve-opening direction
is set to be larger than the spring constant of the spring 104 that
biases the pilot valve body 99 in the valve-closing direction as
described above.
[0125] Thus, the pilot valve 110 moves in the valve-opening
direction by the biasing force of the spring 101 together with the
fail-safe valve 103 that is in contact with the pilot valve body
99. As illustrated in FIG. 7, when the pilot valve 110 including
the pilot valve body 99 and the fail-safe valve 103 is moved to its
full extent in the valve-opening direction (when the spring 104 is
in a full compression state) in case of the failure or the like,
the fail-safe valve 103 is fixed with an inner circumference
thereof sandwiched between the pilot valve body 99 and the spring
104 with a spring receiving seat 103a interposed. In particular, in
case of the failure, since the solenoid 90 breaks down and does not
operate normally, the thrust toward the lower end side applied by
the solenoid 90 disappears. Moreover, the biasing force toward the
lower end side applied by the spring 104 is weaker than the biasing
force toward the upper end side applied by the spring 101. Thus,
the pilot valve body 99 is substantially biased in the
valve-opening direction by the elastic force of the spring 101 and
the oil pressure of the oil. That is, the biasing means that biases
the pilot valve body 99 in the valve-opening direction is the
spring 101 and the oil pressure.
[0126] As described above, since the pilot valve body 99 is biased
in the valve-opening direction by the spring 101 as well as the oil
pressure, it is possible to easily create a state in which the
pilot valve body 99 is moved in the valve-opening direction to the
full extent in case of the failure.
[0127] In this state, the pilot valve body 99 is in a fully open
state in relation to the valve seat member 58. Therefore, supposing
that the fail-safe valve 103 is opened by being spaced from the
pilot valve body 99 immediately when the oil flows due to the
function of the check valve only as in the normal case, the
internal pressure of the pilot chamber 61 and the passage between
the pilot chamber 61 and the pilot valve 110 decreases abruptly,
and thus the opening degree of the main valve 60 increases
abruptly. Therefore, since the flow resistance of the oil passing
through the main valve 60 decreases, the damping force in the
compression-side stroke and the extension-side stroke decreases
abruptly. Consequently, riding stability of the two-wheeled motor
vehicle is impaired.
[0128] In the present embodiment, in the state illustrated in FIG.
7, in case of the failure, the pilot valve body 99 and the
fail-safe valve 103 move toward the upper end side to their full
extent. In this case, an inner circumference of the fail-safe valve
103 is fixed by being sandwiched between a supporting portion 99b
of the pilot valve body 99 and the spring 104 with the spring
receiving seat 103a interposed. Moreover, when the internal
pressure of the pilot chamber 61 and the passage between the pilot
chamber 61 and the pilot valve 110 exceeds a predetermined value,
an outer circumference of the fail-safe valve 103 is deformed as
depicted by dot lines in FIG. 7 and is away from the pilot valve
body 99.
[0129] In this case, with the flow resistance of the gap between
the fail-safe valve 103 and the pilot valve body 99, an abrupt
decrease in the internal pressure of the pilot chamber 61 and the
passage between the pilot chamber 61 and the pilot valve 110 is
suppressed, and a certain degree of the internal pressure can be
maintained. As a result, an abrupt increase in the opening degree
of the main valve 60 is suppressed. Thus, the first leg 10a can
maintain a certain level of the damping force in both the
compression-side stroke and the extension-side stroke in case of
the failure. In this case, by changing rigidity of the fail-safe
valve 103 and an oil-pressure receiving area of the fail-safe valve
103, it is possible to change the internal pressure of the pilot
chamber 61 and the passage between the pilot chamber 61 and the
pilot valve 110 in case of the failure and to arbitrarily adjust
the certain level of the damping force of the main valve 60 in case
of the failure.
[0130] In case of the failure, during the compression-side stroke,
similarly to the normal case described above, as indicated by the
broken-line arrows in FIG. 5, a portion of the oil flowing from the
piston-side oil chamber S1 into the gap 67 through the oil hole 72b
of the lower piston member 72 flows from the passage 63 on the
outer circumference of the main valve 60 into the pilot chamber 61
through the oil hole 60a of the main valve 60. Moreover, during the
extension-side stroke, as indicated by the broken-line arrows in
FIG. 6, a portion of the oil flowing from the rod-side oil chamber
S2 into the gap 67 through the oil hole 71a of the upper piston
member 71 flows from the passage 63 on the outer circumference of
the main valve 60 into the pilot chamber 61 through the oil hole
60a of the main valve 60.
[0131] The flow in the pilot passage 170, of a portion of the oil
flowing into the gap 67 is the same for both the compression-side
stroke and the extension-side stroke. Thus, the subsequent flow in
the pilot passage 170 will be described with reference to the
compression-side stroke in FIG. 5.
[0132] As indicated by the broken-line arrows in FIG. 5, a portion
of the oil flowing into the pilot chamber 61 flows from the pilot
chamber 61 into the space 100 of the valve seat member 58 through
the oil hole (not illustrated) of the main valve member 59 and the
oil holes 58d and 58c of the valve seat member 58. The pilot valve
body 99 is in a fully open state in relation to the valve seat
member 58.
[0133] Moreover, the oil flowing into the space 100 of the valve
seat member 58 passes through the oil hole 99a of the pilot valve
body 99 to push and open the fail-safe valve 103 while resisting
the biasing force of the spring 104 to flow into the space 102 of
the core 92. An abrupt decrease in the internal pressure of the
pilot chamber 61 and the passage between the pilot chamber 61 and
the pilot valve 110 is prevented by the flow resistance of the oil
when passing through the fail-safe valve 103. As a result, an
abrupt increase in the opening degree of the main valve 60 is
prevented. Thus, an abrupt decrease of the damping force during the
compression-side stroke and extension-side stroke is prevented by
the flow resistance of the oil passing through the main valve 60,
and therefore the riding stability of the two-wheeled motor vehicle
is secured.
[0134] The oil flowing into the space 102 flows into the space 64
of the upper piston member 71 through the oil hole 58f of the valve
seat member 58 and the passages 105 and 106. During the
compression-side stroke, as indicated by the broken-line arrows in
FIG. 5, the oil flowing into the space 64 joins the oil flowing
through the main passage 150 to flow into the rod-side oil chamber
S2. During the extension-side stroke, as indicated by the
broken-line arrows in FIG. 6, the oil flowing into the space 64
joins the oil flowing through the main passage 160 to flow into the
piston-side oil chamber S1.
[0135] During the compression-side stroke, a remaining portion of
the oil flowing into the pilot chamber 61 flows into the gap 75
between the inner tube 21 and the piston 70 through the
communication passage 72d as indicated by the one-dot-chain-line
arrow in FIG. 5 as described above. Since the gap 75 communicates
with the rod-side oil chamber S2, the remaining portion of the oil
flowing into the pilot chamber 61 flows into the rod-side oil
chamber S2.
[0136] During the compression-side stroke, the internal pressure
(back pressure) of the pilot chamber 61 also decreases in case of
the failure, and the force that presses the main valve 60 in the
valve-closing direction (toward the upper end side) decreases. When
the communication passage 72d is provided, the damping force during
compression-side stroke is low as compared to when the
communication passage 72d is not provided. Thus, it is possible to
adjust the damping force to be relatively low as an initial setting
during the compression-side stroke.
[0137] During the extension-side stroke, the oil flows into the
pilot chamber 61 through the communication passage 72d in case of
the failure. However, by controlling the sum of the flow resistance
of the gap between the extension-side inlet check valve 55 and the
upper piston member 71 and the flow resistance of the oil hole 60a
to be equal to the flow resistance of the communication passage
72d, the increase in the internal pressure of the pilot chamber 61
due to the oil flowing into the pilot chamber 61 through the bypass
passage 180 can be suppressed.
[0138] As described above, in the first leg 10a of the front fork
10 which is the damping force variable shock absorber according to
the first embodiment, when the damping force is adjusted by
solenoid-based electronic control using one damping force
adjustment mechanism which includes one main valve 60, one pilot
chamber 61, and one pilot valve 110, since the oil flows through
the same main valve 60, pilot chamber 61, and pilot valve 110 for
both the compression-side stroke and the extension-side stroke, the
damping force is adjusted in the same manner for both the
compression-side stroke and the extension-side stroke. Moreover, in
case of the failure, the first leg 10a of the front fork 10 can
maintain the certain level of the damping force for both the
compression-side stroke and the extension-side stroke. In this
case, in the first embodiment, since the communication passage 72d
is provided, it is possible to adjust the damping force during the
compression-side stroke only to be relatively low as an initial
setting and to perform different adjustments during the
compression-side stroke and the extension-side stroke as initial
settings while maintaining compact structure of one damping force
adjustment mechanism which includes one main valve 60, one pilot
chamber 61, and one pilot valve 110 including one pilot valve body
99 and one fail-safe valve 103.
Second Embodiment
[0139] FIG. 8 is a drawing illustrating a longitudinal
cross-section of a damping force variable device 51 of a first leg
10a of a front fork 10 which is a damping force variable shock
absorber according to a second embodiment. FIG. 8 illustrates a
portion of the inner tube 21 for the sake of convenience. Moreover,
the same constituent elements as those of the first embodiment will
be denoted by the same reference numerals and redundant description
thereof will be omitted or simplified.
[0140] As illustrated in FIG. 8, the communication passage 72d of
the damping force variable device 51 allows the pilot chamber 61
and the piston-side oil chamber S1 to communicate with each other.
In this case, as illustrated in FIG. 8, one end of the
communication passage 72d is open to a side surface of the lower
piston member 72 below the sliding sealing member 73.
[0141] One end of the communication passage 72d is open to the gap
76 formed between the inner tube 21 and the piston 70 on the lower
end side than the sliding sealing member 73. The gap 76
communicates with the piston-side oil chamber S1 (see FIG. 2).
[0142] Here, the communication passage 72d is not limited to a
configuration in which the communication passage 72d allows the
pilot chamber 61 and the piston-side oil chamber S1 to communicate
with each other. The communication passage 72d may allow a passage
between the pilot chamber 61 and the pilot valve 110 to communicate
with the piston-side oil chamber S1. The passage between the pilot
chamber 61 and the pilot valve 110 is the same as that of the first
embodiment. In this connection, the passage including the
communication passage 72d and the gap 76 is referred to as a bypass
passage 181.
[0143] Next, operation during the compression-side stroke and the
extension-side stroke of the first leg 10a having such a
configuration will be described with reference to FIGS. 9 and 10.
FIG. 9 is a longitudinal cross-sectional view illustrating the flow
of the oil during the compression-side stroke of the damping force
variable device 51 of the first leg 10a of the front fork 10 which
is the damping force variable shock absorber according to the
second embodiment. FIG. 10 is a longitudinal cross-sectional view
illustrating the flow of the oil during the extension-side stroke
of the damping force variable device 51 of the first leg 10a of the
front fork 10 which is the damping force variable shock absorber
according to the second embodiment. FIGS. 9 and 10 illustrate a
portion of the inner tube 21 for the sake of convenience.
[0144] In the damping force variable device 51, the flow of the oil
during the compression-side stroke and the extension-side stroke
except the flow of the oil through the communication passage 72d is
the same as the flow of the oil described with reference to FIGS. 5
and 6, for example. In this example, the flow different from the
flow of the oil described above will be mainly described.
[0145] (Compression-Side Stroke)
[0146] First, the compression-side stroke will be described with
reference to FIG. 9.
[0147] As indicated by broken-line arrows in FIG. 9, a portion of
the oil flowing from the piston-side oil chamber 51 to the gap 67
through the oil hole 72b of the lower piston member 72 flows from
passage 63 on the outer circumference of the main valve 60 into the
pilot chamber 61 while passing through the oil hole 60a of the main
valve 60. Moreover, as indicated by an one-dot-chain-line arrow in
FIG. 9, a portion of the oil in the piston-side oil chamber 51
flows from the piston-side oil chamber 51 into the pilot chamber 61
through the communication passage 72d. That is, the flow of the oil
in the piston-side oil chamber 51 branches into two passages, the
oil flowing along the main passage 150 indicated by solid-line
arrows in FIG. 9 and the oil flowing along the bypass passage 181
indicated by the one-dot-chain-line arrow in FIG. 9, near the
extension-side outlet check valve 53.
[0148] The oil flowing into the pilot chamber 61 flows from the
pilot chamber 61 into the space 100 of the valve seat member 58
through the oil hole (not illustrated) of the main valve member 59,
the oil holes 58d and 58c of the valve seat member 58, and the gap
between the pilot valve body 99 and the valve seat 58e. The oil
flowing into the space 100 of the valve seat member 58 passes
through the oil hole 99a of the pilot valve body 99 to push and
open the fail-safe valve 103 while resisting the biasing force of
the spring 104 to flow into the space 102 of the core 92. The oil
flowing into the space 102 flows into the space 64 of the upper
piston member 71 through the oil hole 58f of the valve seat member
58 and the passages 105 and 106 to join the oil flowing through the
main passage 150. The joined oil flows into the rod-side oil
chamber S2.
[0149] Here, pressure of the oil flowing into the pilot chamber 61
through the main passage 150 is reduced by flow resistance of a gap
between the compression-side inlet check valve 54 and the lower
piston member 72 and the flow resistance of the oil hole 60a in
relation to internal pressure of the piston-side oil chamber 51. On
the other hand, pressure of the oil flowing into the pilot chamber
61 through the bypass passage 181 is reduced by the flow resistance
of the communication passage 72d in relation to the internal
pressure of the piston-side oil chamber 51. Thus, in the first leg
10a, by controlling the sum of the flow resistance of the gap
between the compression-side inlet check valve 54 and the lower
piston member 72 and the flow resistance of the oil hole 60a to be
equal to the flow resistance of the communication passage 72d, the
increase in the internal pressure of the pilot chamber 61 due to
the oil flowing into the pilot chamber 61 through the bypass
passage 181 can be suppressed.
[0150] (Extension-Side Stroke)
[0151] Next, the extension-side stroke will be described with
reference to FIG. 10.
[0152] As indicated by broken-line arrows in FIG. 10, a portion of
the oil flowing from the rod-side oil chamber S2 into the gap 67
through the oil hole 71a of the upper piston member 71 converges
with the oil flowing in the main passage 160 through the pilot
passage 170. Moreover, as indicated by an one-dot-chain-line arrow
in FIG. 10, a portion of the oil flowing through the pilot passage
170 flows from the pilot chamber 61 into the piston-side oil
chamber 51 through the communication passage 72d. That is, a
portion of the oil flowing through the pilot passage 170 flows into
the piston-side oil chamber 51 through the bypass passage 181.
[0153] As a result, the internal pressure (the back pressure) of
the pilot chamber 61 during the extension-side stroke decreases and
thus force that presses the main valve 60 in the valve-closing
direction (toward the upper end side) decreases. When the
communication passage 72d is provided, the damping force during the
compression-side stroke is low as compared to when the
communication passage 72d is not provided. Thus, it is possible to
adjust the damping force to be relatively low as an initial setting
during the extension-side stroke.
[0154] (In Case of Failure)
[0155] The flow of the oil in case of the failure is basically the
same as the flow of the oil in the damping force variable shock
absorber according to the first embodiment. In this example, the
flow different from the flow of the oil in case of the failure
according to the first embodiment will be mainly described.
[0156] In the compression-side stroke and the extension-side
stroke, as described above, a portion of the oil flowing from the
gap 67 into the pilot chamber 61 flows from the pilot chamber 61
into the space 100 of the valve seat member 58 through the oil hole
(not illustrated) of the main valve member 59 and the oil holes 58d
and 58c of the valve seat member 58 as indicated by the broken-line
arrows in FIGS. 9 and 10. The pilot valve body 99 is in a fully
open state in relation to the valve seat member 58.
[0157] The oil flowing into the space 100 of the valve seat member
58 passes through the oil hole 99a of the pilot valve body 99 to
push and open the fail-safe valve 103 while resisting the biasing
force of the spring 104 to flow into the space 102 of the core 92.
With the flow resistance of the oil when passing through the
fail-safe valve 103, an abrupt decrease in the internal pressure of
the pilot chamber 61 and the passage between the pilot chamber 61
and the pilot valve 110 is prevented. As a result, an abrupt
increase in the opening degree of the main valve 60 is prevented.
Thus, an abrupt decrease of the damping force during the
compression-side stroke and the extension-side stroke is prevented
by the flow resistance of the oil passing through the main valve
60, and therefore the riding stability of the two-wheeled motor
vehicle is secured.
[0158] The oil flowing into the space 102 flows into the space 64
of the upper piston member 71 through the oil hole 58f of the valve
seat member 58 and the passages 105 and 106. During the
compression-side stroke, as indicated by the broken-line arrows in
FIG. 9, the oil flowing into the space 64 joins the oil flowing
through the main passage 150 to flow into the rod-side oil chamber
S2. During the extension-side stroke, as indicated by the
broken-line arrows in FIG. 10, the oil flowing into the space 64
joins the oil flowing through the main passage 160 to flow into the
piston-side oil chamber S1.
[0159] During the compression-side stroke, the oil flows into the
pilot chamber 61 through the communication passage 72d in case of
the failure. However, by controlling the sum of the flow resistance
of the gap between the compression-side inlet check valve 54 and
the lower piston member 72 and the flow resistance of the oil hole
60a to be equal to the flow resistance of the communication passage
72d, the increase in the internal pressure of the pilot chamber 61
due to the oil flowing into the pilot chamber 61 through the bypass
passage 181 can be suppressed.
[0160] On the other hand, during the extension-side stroke, a
remaining portion of the oil flowing into the pilot chamber 61
flows into the gap 76 between the inner tube 21 and the piston 70
through the communication passage 72d as indicated by the
one-dot-chain-line arrow in FIG. 10 as described above. Since the
gap 76 communicates with the piston-side oil chamber S1, the
remaining portion of the oil flowing into the pilot chamber 61
flows into the piston-side oil chamber S1.
[0161] During the extension-side stroke, the internal pressure
(back pressure) of the pilot chamber 61 also decreases in case of
the failure, and the force that presses the main valve 60 in the
valve-closing direction (toward the upper end side) decreases. When
the communication passage 72d is provided, the damping force during
the extension-side stroke is low as compared to when the
communication passage 72d is not provided. Thus, it is possible to
adjust the damping force to be relatively low as an initial setting
during the extension-side stroke.
[0162] As described above, in the first leg 10a of the front fork
10 which is the damping force variable shock absorber according to
the second embodiment, when the damping force is adjusted by
solenoid-based electronic control using one damping force
adjustment mechanism which includes one main valve 60, one pilot
chamber 61, and one pilot valve 110, since the oil flows through
the same main valve 60, pilot chamber 61, and pilot valve 110 for
both the compression-side stroke and the extension-side stroke, the
damping force is adjusted in the same manner for both the
compression-side stroke and the extension-side stroke. Moreover, in
case of the failure, the first leg 10a of the front fork 10 can
maintain a certain damping force for both the compression-side
stroke and the extension-side stroke. In this case, in the second
embodiment, since the communication passage 72d is provided, it is
possible to adjust the damping force during the extension-side
stroke only to be relatively low as an initial setting and to
perform different adjustments during the compression-side stroke
and the extension-side stroke as initial settings while maintaining
compact structure of one damping force adjustment mechanism which
includes one main valve 60, one pilot chamber 61, and one pilot
valve 110 including one pilot valve body 99 and one fail-safe valve
103.
[0163] Meanwhile, in the first leg 10a of the front fork 10, the
damping force variable device 50 of the first embodiment and the
damping force variable device 51 of the second embodiment are
provided inside the piston 70. However, the present invention is
not limited to this, but the damping force variable device 50 of
the first embodiment and the damping force variable device 51 of
the second embodiment may naturally be provided outside the piston
70.
[0164] In the abovementioned embodiments, although examples in
which the damping force variable shock absorber is applied to the
front fork that suspends the front wheel of the two-wheeled motor
vehicle in relation to the vehicle body have been illustrated, the
present invention can be also applied to other types of shock
absorbers of the two-wheeled motor vehicle, including a rear
cushion that suspends a rear wheel of the two-wheeled motor vehicle
in relation to the vehicle body.
[0165] Here, hydraulic circuits when the damping force variable
shock absorber is applied to other types of shock absorbers of the
two-wheeled motor vehicle will be described. FIGS. 11 to 14 are
hydraulic circuit diagrams when the damping force variable shock
absorber of the present invention is applied to other types of
shock absorbers.
[0166] In FIGS. 11 to 14, the flow of the oil during the
compression-side stroke is depicted by solid lines and the flow of
the oil during the extension-side stroke is depicted by broken
lines. FIGS. 11 to 14 illustrate the hydraulic circuits when the
communication passage 72d corresponding to the first embodiment is
provided. That is, the communication passage 72d allows the pilot
chamber (not illustrated) or the passage between the pilot chamber
(not illustrated) and the pilot valve (not illustrated) to
communicate with the rod-side oil chamber S2.
[0167] (Damping Force Variable Shock Absorber 11 of FIG. 11)
[0168] As illustrated in FIG. 11, a damping force variable shock
absorber 11 includes a cylinder 190 in which oil is enclosed, a
piston 70 slidably fitted into the cylinder 190, a piston rod 26
having one end connected to the piston 70 and the other end
extended outside the cylinder 190, a rod-side oil chamber S2
partitioned by the piston 70 and provided closer to the other end
in the axial direction of the cylinder 190 than the piston 70, a
piston-side oil chamber 51 provided closer to one end in the axial
direction of the cylinder 190 than the piston 70, and a damping
force variable device 50 that controls flow of the oil enclosed in
the cylinder 190 so that damping force can be varied. The oil
functions as fluid, the rod-side oil chamber S2 functions as a
rod-side fluid chamber, and the piston-side oil chamber 51
functions as a piston-side fluid chamber.
[0169] The damping force variable device 50 includes a main valve
60 that opens and closes to control the flow of the oil caused by
sliding of the piston 70 in the cylinder 190 to generate the
damping force, a pilot chamber (not illustrated) into which a
portion of the flow of the oil is introduced so that internal
pressure is applied to the main valve 60 in a valve-closing
direction, a pilot valve (not illustrated) that opens and closes to
adjust internal pressure of the pilot chamber (not illustrated),
and a communication passage 72d that allows the pilot chamber (not
illustrated) or a passage (not illustrated) between the pilot
chamber (not illustrated) and the pilot valve (not illustrated) to
communicate with the rod-side oil chamber S2. Although the pilot
chamber and the pilot valve are not illustrated, these elements are
provided on a pilot passage 170 similarly to those illustrated in
the first leg 10a of the front fork 10.
[0170] Moreover, the damping force variable device 50 includes a
compression-side inlet check valve 54 provided on a main passage
150 on an upstream side of the main valve 60 and the pilot passage
170, a compression-side outlet check valve 56 provided on the main
passage 150 on a downstream side of the main valve 60 and the pilot
passage 170, an extension-side inlet check valve 55 provided on a
main passage 160 on the upstream side of the main valve 60 and the
pilot passage 170, an extension-side outlet check valve 53 provided
on the main passage 160 on the downstream side of the main valve 60
and the pilot passage 170, and an oil storage chamber Re that
communicates with a place which is on the downstream side of the
main valve 60 and the pilot passage 170 and an upstream side of the
compression-side outlet check valve 56 and the extension-side
outlet check valve 53. The oil storage chamber Re functions as a
fluid storage chamber.
[0171] In the damping force variable shock absorber 11, the damping
force variable device 50 and the oil storage chamber Re are
provided outside the piston 70 and further outside the cylinder 190
in which the piston 70 slides. The oil storage chamber Re has a
function of supplying and discharging predetermined oil. The oil
storage chamber Re may include a pouch-shaped bladder filled with
gas, for example. Moreover, the communication passage 72d
communicates with the pilot chamber (not illustrated) on the pilot
passage 170 or a passage between the pilot chamber (not
illustrated) and the pilot valve (not illustrated) and the rod-side
oil chamber S2.
[0172] Moreover, the oil storage chamber Re communicates with a
passage that branches on the downstream side of the main valve 60
and the pilot passage 170. Since the oil storage chamber Re
communicates on the downstream side of the main valve 60 and the
pilot passage 170, the oil damped by the main valve 60 is
introduced into the oil storage chamber Re. That is, pressure of
the rod-side oil chamber S2 depends on almost only pressure of an
air chamber (not illustrated) present in the oil storage chamber Re
and does not change depending on set passage resistance of the main
valve 60. Thus, delay in change in the damping force during
reversal from a compression-side stroke to an extension-side stroke
can be prevented.
[0173] (1-1) Compression-Side Stroke
[0174] When a rear wheel of a two-wheeled motor vehicle moves
upward and downward following unevenness on a road surface during
riding the two-wheeled motor vehicle, the damping force variable
shock absorber that suspends the rear wheel is extended and
compressed. In the compression-side stroke in which the piston rod
26 moves upward in relation to the cylinder 190, the oil in the
piston-side oil chamber 51 is compressed by the piston 70 and
pressure therein increases. Then, the oil in the piston-side oil
chamber 51 is guided to the damping force variable device 50.
[0175] The oil guided to the damping force variable device 50 flows
into the rod-side oil chamber S2 through the main passage 150
during the compression-side stroke. At this time, with flow
resistance of the oil when passing through the main valve 60,
compression-side damping force is generated in the damping force
variable shock absorber. Here, a position at which the main passage
150 and the pilot passage 170 illustrated in FIG. 5 join
corresponds to a position at which reference numerals of the main
valve 60 and the pilot passage 170 are described on the damping
force variable shock absorber 11 illustrated in FIG. 11.
[0176] Moreover, a portion of the oil flowing in the pilot passage
170 flows into the rod-side oil chamber S2 through the
communication passage 72d.
[0177] Moreover, in the compression-side stroke, an amount of the
oil corresponding to volume of the piston rod 26 advancing into the
cylinder 190 is supplied from the piston-side oil chamber 51 to the
oil storage chamber Re. In this way, a change in volume in the
cylinder 190 resulting from the piston rod 26 advancing into the
cylinder 190 is compensated.
[0178] (1-2) Extension-Side Stroke
[0179] In the extension-side stroke in which the piston rod 26
moves downward in relation to the cylinder 190, the piston 70 moves
downward inside the cylinder 190 together with the piston rod 26.
Thus, the oil in the rod-side oil chamber S2 is compressed by the
piston 70 and pressure thereof increases. Then, the oil in the
rod-side oil chamber S2 is guided to the damping force variable
device 50.
[0180] The oil guided to the damping force variable device 50 flows
into the piston-side oil chamber S1 through the main passage 160
during the extension-side stroke. At this time, with flow
resistance of the oil when passing through the main valve 60,
extension-side damping force is generated in the damping force
variable shock absorber. Here, a position at which the main passage
160 and the pilot passage 170 illustrated in FIG. 6 join
corresponds to the position at which the reference numerals of the
main valve 60 and the pilot passage 170 are described on the
damping force variable shock absorber 11 illustrated in FIG.
11.
[0181] Moreover, a portion of the oil in the rod-side oil chamber
S2 flows into the pilot passage 170 through the communication
passage 72d via the pilot chamber (not illustrated), for
example.
[0182] Moreover, in the extension-side stroke, an amount of the oil
corresponding to volume of the piston rod 26 exiting from the
cylinder 190 is supplied from the oil storage chamber Re to the
piston-side oil chamber S1. As a result, a change in volume in the
cylinder 190 resulting from the piston rod 26 exiting from the
cylinder 190 is compensated.
[0183] The damping force variable shock absorber 11 illustrated in
FIG. 11 shows the communication passage 72d that communicates with
the pilot chamber (not illustrated) on the pilot passage 170 or the
passage between the pilot chamber (not illustrated) and the pilot
valve (not illustrated) and the rod-side oil chamber S2 and
corresponds to the first embodiment of the first leg 10a of the
front fork 10. In this case, the same operational effects as
operational effects of the damping force variable shock absorber
illustrated in the first embodiment can be obtained. However, the
present invention is not limited to this, and the second embodiment
may naturally be applied to the damping force variable shock
absorber 11 as the communication passage 72d which communicates
with the pilot chamber (not illustrated) on the pilot passage 170
or the passage between the pilot chamber (not illustrated) and the
pilot valve (not illustrated) and the piston-side oil chamber S1.
In this case, the same operational effects as operational effects
of the damping force variable shock absorber illustrated in the
second embodiment can be obtained.
[0184] (Damping Force Variable Shock Absorber 12 of FIG. 12)
[0185] As illustrated in FIG. 12, a damping force variable shock
absorber 12 includes a cylinder 190 in which oil is enclosed, a
piston 70 slidably fitted into the cylinder 190, a piston rod 26
having one end connected to the piston 70 and the other end
extended outside the cylinder 190, a rod-side oil chamber S2
partitioned by the piston 70 and provided closer to the other end
in the axial direction of the cylinder 190 than the piston 70, a
piston-side oil chamber S1 provided closer to one end in the axial
direction of the cylinder 190 than the piston 70, and a damping
force variable device 50 that controls flow of the oil enclosed in
the cylinder 190 so that damping force can be varied. The oil
functions as fluid, the rod-side oil chamber S2 functions as a
rod-side fluid chamber, and the piston-side oil chamber S1
functions as a piston-side fluid chamber.
[0186] The damping force variable device 50 includes a main valve
60 that opens and closes to control the flow of the oil caused by
sliding of the piston 70 in the cylinder 190 to generate the
damping force, a pilot chamber (not illustrated) in to which a
portion of the flow of the oil is introduced so that internal
pressure is applied to the main valve 60 in a valve-closing
direction, a pilot valve (not illustrated) that opens and closes to
adjust internal pressure of the pilot chamber (not illustrated),
and a communication passage 72d that allows the pilot chamber (not
illustrated) or a passage (not illustrated) between the pilot
chamber (not illustrated) and the pilot valve (not illustrated) to
communicate with the rod-side oil chamber S2. Although the pilot
chamber and the pilot valve are not illustrated, these elements are
provided on a pilot passage 170 similarly to those illustrated in
the first leg 10a of the front fork 10.
[0187] Moreover, the damping force variable device 50 includes a
compression-side inlet check valve 54 provided on a main passage
150 on an upstream side of the main valve 60 and the pilot passage
170, a compression-side outlet check valve 56 provided on the main
passage 150 on a downstream side of the main valve 60 and the pilot
passage 170, an extension-side inlet check valve 55 provided on a
main passage 160 on the upstream side of the main valve 60 and the
pilot passage 170, an extension-side outlet check valve 53 provided
on a main passage 160 on the downstream side of the main valve 60
and the pilot passage 170, and an oil storage chamber Re that
communicates with a place which is on the downstream side of the
main valve 60 and the pilot passage 170 and an upstream side of the
compression-side outlet check valve 56 and the extension-side
outlet check valve 53. The oil storage chamber Re functions as a
fluid storage chamber.
[0188] In the damping force variable shock absorber 12, the damping
force variable device 50 and the oil storage chamber Re are
provided inside the piston 70 in the cylinder 190. The present
invention is not limited to this, and the oil storage chamber Re
may be provided outside the piston 70 in the cylinder 190.
Moreover, the oil storage chamber Re may be provided in an
axle-side attachment member (not illustrated) or near the axle-side
attachment member (not illustrated) by being extended from a
passage that passes through the piston rod 26. Moreover, the
communication passage 72d communicates with the pilot chamber (not
illustrated) on the pilot passage 170 or a passage between the
pilot chamber (not illustrated) and the pilot valve (not
illustrated) and the rod-side oil chamber S2.
[0189] Moreover, the oil storage chamber Re communicates with a
passage that branches on the downstream side of the main valve 60
and the pilot passage 170. Since the oil storage chamber Re
communicates on the downstream side of the main valve 60 and the
pilot passage 170, the oil damped by the main valve 60 is
introduced into the oil storage chamber Re. That is, pressure of
the rod-side oil chamber S2 depends on almost only pressure of an
air chamber (not illustrated) present in the oil storage chamber Re
and does not change depending on set passage resistance of the main
valve 60. Thus, delay in change in the damping force during
reversal from a compression-side stroke to an extension-side stroke
can be prevented.
[0190] (2-1) Compression-Side Stroke
[0191] The oil in the piston-side oil chamber 51, of which the
pressure is increased by the piston rod 26 moving upward in
relation to the cylinder 190 flows into the rod-side oil chamber S2
through the main passage 150 during compression-side stroke. At
this time, with flow resistance of the oil when passing through the
main valve 60, compression-side damping force is generated in the
damping force variable shock absorber. Here, the position at which
the main passage 150 and the pilot passage 170 illustrated in FIG.
5 join corresponds to a position at which reference numerals of the
main valve 60 and the pilot passage 170 are described on the
damping force variable shock absorber 12 illustrated in FIG.
12.
[0192] Moreover, a portion of the oil flowing in the pilot passage
170 flows into the rod-side oil chamber S2 through the
communication passage 72d.
[0193] Moreover, in the compression-side stroke, an amount of the
oil corresponding to volume of the piston rod 26 advancing into the
cylinder 190 is supplied from the piston-side oil chamber 51 to the
oil storage chamber Re. In this way, a change in volume in the
cylinder 190 resulting from the piston rod 26 advancing into the
cylinder 190 is compensated.
[0194] (2-2) Extension-Side Stroke
[0195] The oil in the rod-side oil chamber S2, of which the
pressure is increased by the piston rod 26 moving downward in
relation to the cylinder 190 flows into the piston-side oil chamber
51 through the main passage 160 during the extension-side stroke.
At this time, with the flow resistance of the oil when passing
through the main valve 60, extension-side damping force is
generated in the damping force variable shock absorber. Here, a
position at which the main passage 160 and the pilot passage 170
illustrated in FIG. 6 join corresponds to the position at which the
reference numerals of the main valve 60 and the pilot passage 170
are described on the damping force variable shock absorber 12
illustrated in FIG. 12.
[0196] Moreover, a portion of the oil in the rod-side oil chamber
S2 flows into the pilot passage 170 through the communication
passage 72d via the pilot chamber (not illustrated), for
example.
[0197] Moreover, in the extension-side stroke, an amount of the oil
corresponding to volume of the piston rod 26 exiting from the
cylinder 190 is supplied from the oil storage chamber Re to the
piston-side oil chamber S1. As a result, a change in volume in the
cylinder 190 resulting from the piston rod 26 exiting from the
cylinder 190 is compensated.
[0198] The damping force variable shock absorber 12 illustrated in
FIG. 12 shows the communication passage 72d that communicates with
the pilot chamber (not illustrated) on the pilot passage 170 or the
passage between the pilot chamber (not illustrated) and the pilot
valve (not illustrated) and the rod-side oil chamber S2 and
corresponds to the first embodiment of the first leg 10a of the
front fork 10. In this case, the same operational effects as
operational effects of the damping force variable shock absorber
illustrated in the first embodiment can be obtained. However, the
present invention is not limited to this, and the second embodiment
may naturally be applied to the damping force variable shock
absorber 12 as the communication passage 72d which communicates
with the pilot chamber (not illustrated) on the pilot passage 170
or the passage between the pilot chamber (not illustrated) and the
pilot valve (not illustrated) and the piston-side oil chamber S1.
In this case, the same operational effects as operational effects
of the damping force variable shock absorber illustrated in the
second embodiment can be obtained.
[0199] (Damping Force Variable Shock Absorber 13 of FIG. 13)
[0200] As illustrated in FIG. 13, a damping force variable shock
absorber 13 includes a cylinder 190 in which oil is enclosed, a
piston 70 slidably fitted into the cylinder 190, a piston rod 26
having one end connected to the piston 70 and the other end
extended outside the cylinder 190, a rod-side oil chamber S2
partitioned by the piston 70 and provided closer to the other end
in an axial direction of the cylinder 190 than the piston 70, the
piston-side oil chamber S1 provided closer to one end in the axial
direction of the cylinder 190 than the piston 70, an oil storage
chamber Re that communicates with the piston-side oil chamber S1,
and a damping force variable device 50 that controls flow of the
oil enclosed in the cylinder 190 so that damping force can be
varied. The oil functions as fluid, the rod-side oil chamber S2
functions as a rod-side fluid chamber, the piston-side oil chamber
S1 functions as a piston-side fluid chamber, and the oil storage
chamber Re functions as a fluid storage chamber.
[0201] The damping force variable device 50 includes a main valve
60 that opens and closes to control the flow of the oil caused by
sliding of the piston 70 in the cylinder 190 to generate the
damping force, a pilot chamber (not illustrated) into which a
portion of the flow of the oil is introduced so that internal
pressure is applied to the main valve 60 in a valve-closing
direction, a pilot valve (not illustrated) that opens and closes to
adjust internal pressure of the pilot chamber (not illustrated),
and a communication passage 72d that allows the pilot chamber (not
illustrated) or a passage (not illustrated) between the pilot
chamber (not illustrated) and the pilot valve (not illustrated) to
communicate with the rod-side oil chamber S2. Although the pilot
chamber and the pilot valve are not illustrated, these elements are
provided on the pilot passage 170 similarly to those illustrated in
the first leg 10a of the front fork 10.
[0202] Moreover, the damping force variable device 50 includes a
compression-side inlet check valve 54 provided on the main passage
150 on an upstream side of the main valve 60 and the pilot passage
170, a compression-side outlet check valve 56 provided on the main
passage 150 on a downstream side of the main valve 60 and the pilot
passage 170, an extension-side inlet check valve 55 provided on the
main passage 160 on an upstream side of the main valve 60 and the
pilot passage 170, and an extension-side outlet check valve 53
provided on the main passage 160 on a downstream side of the main
valve 60 and the pilot passage 170.
[0203] As illustrated in FIG. 13, the oil storage chamber Re is not
provided in the damping force variable device 50 but is provided so
as to communicate directly with the piston-side oil chamber S1. In
this case, the damping force variable device 50 and the oil storage
chamber Re are provided outside the piston 70 and furthermore
outside the cylinder 190. An orifice or a check valve (not
illustrated), for example, is provided in an inlet of the oil
storage chamber Re to adjust an amount of introduced oil in order
to allow an amount of oil corresponding to volume of the piston rod
26 advancing into the cylinder 190 to be introduced into the oil
storage chamber Re. Moreover, the communication passage 72d
communicates with the pilot chamber (not illustrated) on the pilot
passage 170 or a passage between the pilot chamber (not
illustrated) and the pilot valve (not illustrated) and the rod-side
oil chamber S2.
[0204] (3-1) Compression-Side Stroke
[0205] The oil in the piston-side oil chamber 51, of which the
pressure is increased by the piston rod 26 moving upward in
relation to the cylinder 190 is guided into the damping force
variable device 50.
[0206] The flow of the oil in the damping force variable device 50
except the flow of the oil introduced into the oil storage chamber
Re is the same as the flow described in (1-1) Compression-Side
Stroke. Here, the position at which the main passage 150 and the
pilot passage 170 illustrated in FIG. 5 join corresponds to a
position at which reference numerals of the main valve 60 and the
pilot passage 170 are described on the damping force variable shock
absorber 13 illustrated in FIG. 13.
[0207] Moreover, a portion of the oil flowing in the pilot passage
170 flows into the rod-side oil chamber S2 through the
communication passage 72d.
[0208] Moreover, in the compression-side stroke, an amount of the
oil corresponding to volume of the piston rod 26 advancing into the
cylinder 190 is supplied from the piston-side oil chamber 51 to the
oil storage chamber Re. In this way, a change in volume in the
cylinder 190 resulting from the piston rod 26 advancing into the
cylinder 190 is compensated.
[0209] (3-2) Extension-Side Stroke
[0210] The oil in the rod-side oil chamber S2, of which the
pressure is increased by the piston rod 26 moving downward in
relation to the cylinder 190 is guided to the damping force
variable device 50. Moreover, the oil in the oil storage chamber Re
is supplied to the piston-side oil chamber S1. As a result, a
change in volume in the cylinder 190 resulting from the piston rod
26 exiting from the cylinder 190 is compensated.
[0211] The flow of the oil in the damping force variable device 50
except the flow of the oil delivered from the oil storage chamber
Re is the same as the flow described in (2-2) Extension-Side
Stroke. Here, a position at which the main passage 150 and the
pilot passage 170 illustrated in FIG. 6 join corresponds to a
position at which reference numerals of the main valve 60 and the
pilot passage 170 are described on the damping force variable shock
absorber 13 illustrated in FIG. 13.
[0212] Moreover, a portion of the oil in the rod-side oil chamber
S2 flows into the pilot passage 170 through the communication
passage 72d via the pilot chamber (not illustrated), for
example.
[0213] Moreover, in the extension-side stroke, an amount of the oil
corresponding to volume of the piston rod 26 exiting from the
cylinder 190 is supplied from the oil storage chamber Re to the
piston-side oil chamber S1. As a result, a change in volume in the
cylinder 190 resulting from the piston rod 26 exiting from the
cylinder 190 is compensated.
[0214] The damping force variable shock absorber 13 illustrated in
FIG. 13 shows the communication passage 72d that communicates with
the pilot chamber (not illustrated) on the pilot passage 170 or the
passage between the pilot chamber (not illustrated) and the pilot
valve (not illustrated) and the rod-side oil chamber S2 and
corresponds to the first embodiment of the first leg 10a of the
front fork 10. In this case, the same operational effects as
operational effects of the damping force variable shock absorber
illustrated in the first embodiment can be obtained. However, the
present invention is not limited to this, and the second embodiment
may naturally be applied to the damping force variable shock
absorber 13 as the communication passage 72d which communicates
with the pilot chamber (not illustrated) on the pilot passage 170
or the passage between the pilot chamber (not illustrated) and the
pilot valve (not illustrated) and the piston-side oil chamber S1.
In this case, the same operational effects as operational effects
of the damping force variable shock absorber illustrated in the
second embodiment can be obtained.
[0215] (Damping Force Variable Shock Absorber 14 of FIG. 14)
[0216] As illustrated in FIG. 14, a damping force variable shock
absorber 14 includes a cylinder 190 in which oil is enclosed, a
piston 70 slidably fitted into the cylinder 190, a piston rod 26
having one end connected to the piston 70 and the other end
extended outside the cylinder 190, a rod-side oil chamber S2
partitioned by the piston 70 and provided closer to the other end
in the axial direction of the cylinder 190 than the piston 70, a
piston-side oil chamber 51 provided closer to one end in the axial
direction of the cylinder 190 than the piston 70, an oil storage
chamber Re that communicates with the piston-side oil chamber 51,
and a damping force variable device 50 that controls flow of the
oil enclosed in the cylinder 190 so that damping force can be
varied. The oil functions as fluid, the rod-side oil chamber S2
functions as a rod-side fluid chamber, the piston-side oil chamber
51 functions as a piston-side fluid chamber, and the oil storage
chamber Re functions as a fluid storage chamber.
[0217] The damping force variable device 50 includes a main valve
60 that opens and closes to control the flow of the oil caused by
sliding of the piston 70 in the cylinder 190 to generate the
damping force, a pilot chamber (not illustrated) into which a
portion of the flow of the oil is introduced so that internal
pressure is applied to the main valve 60 in a valve-closing
direction, a pilot valve (not illustrated) that opens and closes to
adjust internal pressure of the pilot chamber (not illustrated),
and a communication passage 72d that allows the pilot chamber (not
illustrated) or a passage (not illustrated) between the pilot
chamber (not illustrated) and the pilot valve (not illustrated) to
communicate with the rod-side oil chamber S2. Although the pilot
chamber and the pilot valve are not illustrated, these elements are
provided on the pilot passage 170 similarly to those illustrated in
the first leg 10a of the front fork 10.
[0218] Moreover, the damping force variable device 50 includes a
compression-side inlet check valve 54 provided on a main passage
150 on an upstream side of the main valve 60 and the pilot passage
170, a compression-side outlet check valve 56 provided on the main
passage 150 on a downstream side of the main valve 60 and the pilot
passage 170, an extension-side inlet check valve 55 provided on a
main passage 160 on the upstream side of the main valve 60 and the
pilot passage 170, and an extension-side outlet check valve 53
provided on the main passage 160 on the downstream side of the main
valve 60 and the pilot passage 170.
[0219] In the damping force variable shock absorber 14, some
features of the damping force variable shock absorber 14 are
incorporated into the piston 70. That is, the damping force
variable device 50 in which the oil storage chamber Re is not
included is provided inside the piston 70 in the cylinder 190. The
oil storage chamber Re is provided outside the piston 70 and
further outside the cylinder 190 in which the piston 70 slides.
Moreover, the communication passage 72d communicates with the pilot
chamber (not illustrated) on the pilot passage 170 or a passage
between the pilot chamber (not illustrated) and the pilot valve
(not illustrated) and the rod-side oil chamber S2.
[0220] That is, the damping force variable shock absorber 14 is the
same as the damping force variable shock absorber 12 illustrated in
FIG. 12 except that the oil storage chamber Re is not provided
inside the piston 70. Moreover, the oil storage chamber Re of the
damping force variable shock absorber 14 has the same configuration
as that of the oil storage chamber Re illustrated in FIG. 13.
[0221] (4-1) Compression-Side Stroke
[0222] A specific flow of the oil except a flow of the oil
introduced into the oil storage chamber Re is the same as the flow
described in (2-1) Compression-Side Stroke. Here, a position at
which the main passage 150 and the pilot passage 170 illustrated in
FIG. 5 join corresponds to a position at which reference numerals
of the main valve 60 and the pilot passage 170 are described on the
damping force variable shock absorber 14 illustrated in FIG.
14.
[0223] Moreover, a portion of the oil flowing in the pilot passage
170 flows into the rod-side oil chamber S2 through the
communication passage 72d.
[0224] Moreover, in the compression-side stroke, an amount of the
oil corresponding to volume of the piston rod 26 advancing into the
cylinder 190 is supplied from the piston-side oil chamber S1 to the
oil storage chamber Re. In this way, a change in volume in the
cylinder 190 resulting from the piston rod 26 advancing into the
cylinder 190 is compensated.
[0225] (4-2) Extension-Side Stroke
[0226] The specific flow of oil except the flow of oil delivered
from the oil storage chamber Re is the same as the flow described
in (2-2) Extension-Side Stroke. Here, a position at which the main
passage 150 and the pilot passage 170 illustrated in FIG. 6 join
corresponds to a position at which reference numerals of the main
valve 60 and the pilot passage 170 are described on the damping
force variable shock absorber 14 illustrated in FIG. 14.
[0227] Moreover, the oil in the oil storage chamber Re is supplied
to the piston-side oil chamber S1. As a result, a change in volume
in the cylinder 190 resulting from the piston rod 26 exiting from
the cylinder 190 is compensated.
[0228] Moreover, a portion of the oil in the rod-side oil chamber
S2 flows into the pilot passage 170 through the communication
passage 72d via the pilot chamber (not illustrated), for
example.
[0229] Moreover, in the extension-side stroke, an amount of the oil
corresponding to volume of the piston rod 26 exiting from the
cylinder 190 is supplied from the oil storage chamber Re to the
piston-side oil chamber S1. As a result, a change in volume in the
cylinder 190 resulting from the piston rod 26 exiting from the
cylinder 190 is compensated.
[0230] The damping force variable shock absorber 14 illustrated in
FIG. 14 shows the communication passage 72d that communicates with
the pilot chamber (not illustrated) on the pilot passage 170 or the
passage between the pilot chamber (not illustrated) and the pilot
valve (not illustrated) and the rod-side oil chamber S2 and
corresponds to the first embodiment of the first leg 10a of the
front fork 10. In this case, the same operational effects as
operational effects of the damping force variable shock absorber
illustrated in the first embodiment can be obtained. However, the
present invention is not limited to this, and the second embodiment
may naturally be applied to the damping force variable shock
absorber 14 as the communication passage 72d which communicates
with the pilot chamber (not illustrated) on the pilot passage 170
or the passage between the pilot chamber (not illustrated) and the
pilot valve (not illustrated) and the piston-side oil chamber S1.
In this case, the same operational effects as operational effects
of the damping force variable shock absorber illustrated in the
second embodiment can be obtained.
[0231] In FIGS. 11 to 14, although the damping force variable shock
absorbers which include the communication passage 72d corresponding
to the first embodiment have been illustrated, the damping force
variable shock absorbers which include the communication passage
72d corresponding to the second embodiment may naturally be
applied. In this case, the damping force variable shock absorbers
have a circuit diagram which shows that the communication passage
72d allows the position at which the reference numerals of the main
valve 60 and the pilot passage 170 are described to communicate
with the piston-side oil chamber S1.
[0232] In the damping force variable shock absorbers 12 and 14
illustrated in FIGS. 12 and 14, the damping force variable device
50 and the solenoid 90 are provided inside the piston 70. Thus, the
damping force variable device 50 and the solenoid 90 can be
incorporated in the piston 70 in a compact structure and can be
applied to a rear cushion of a two-wheeled motor vehicle, for
example.
[0233] In the damping force variable shock absorbers 11 and 13
illustrated in FIGS. 11 and 13, the damping force variable device
50 and the solenoid 90 are provided outside the piston 70. Thus, by
arranging the damping force variable device 50 and the solenoid 90
outside the piston 70, the damping force variable device 50 and the
solenoid 90 can be disposed at an arbitrary position, and the
degree of freedom of the layout thereof can be increased.
Therefore, the degree of freedom of the arrangement of the solenoid
90 which is an actuator and the layout of harnesses can be
increased.
[0234] In the present invention, FIGS. 11 to 14 illustrate an
inverted damping force variable shock absorber in which the
cylinder 190 is on an upper side and the piston rod 26 is on a
lower side. However, the present invention is not limited to this
but can be similarly applied to an erected damping force variable
shock absorber in which the cylinder 190 is on the lower side and
the piston rod 26 is on the upper side. The damping force variable
shock absorbers illustrated in FIGS. 11 to 14 may naturally be
applied to a front fork and a rear cushion regardless of whether
the damping force variable shock absorber is an erected type or an
inverted type.
[0235] In the abovementioned embodiments, although the present
invention is applied to an inverted front fork in which an outer
tube is attached to a vehicle body side and an inner tube is
attached to an axle side, the present invention can be similarly
applied to an upright front fork in which an inner tube is attached
to a vehicle body side and an outer tube is attached to an axle
side.
[0236] In the present embodiment, although the damping force
variable shock absorber is applied to a two-wheeled motor vehicle,
the present invention can be similarly applied to a damping force
variable shock absorber that suspends a vehicle wheel of an
optional vehicle other than the two-wheeled motor vehicle.
[0237] In summary, the embodiments generally provide a damping
force variable shock absorber including: a cylinder in which fluid
is enclosed; a piston slidably fitted into the cylinder; a piston
rod having one end connected to the piston and the other end
extended outside the cylinder; a rod-side fluid chamber partitioned
by the piston and provided closer to the other end in an axial
direction of the cylinder than the piston; a piston-side fluid
chamber provided closer to one end in the axial direction of the
cylinder than the piston; and a damping force variable device that
controls flow of the fluid enclosed in the cylinder so that damping
force can be varied. The damping force variable device includes: a
main valve that opens and closes to control the flow of the fluid
caused by sliding of the piston in the cylinder, thereby generating
damping force; a pilot chamber into which a portion of the flow of
the fluid is introduced so that internal pressure is applied to the
main valve in a valve-closing direction; a pilot valve that opens
and closes to adjust the internal pressure of the pilot chamber;
and a communication passage that allows the pilot chamber or a
passage between the pilot chamber and the pilot valve to
communicate with the rod-side fluid chamber.
[0238] Alternatively, there may be provided a damping force
variable shock absorber including: a cylinder in which fluid is
enclosed; a piston slidably fitted into the cylinder; a piston rod
having one end connected to the piston and the other end extended
outside the cylinder; a rod-side fluid chamber partitioned by the
piston and provided closer to the other end in an axial direction
of the cylinder than the piston; a piston-side fluid chamber
provided closer to one end in the axial direction of the cylinder
than the piston; and a damping force variable device that controls
flow of the fluid enclosed in the cylinder so that damping force
can be varied. The damping force variable device includes: a main
valve that opens and closes to control the flow of the fluid caused
by sliding of the piston in the cylinder, thereby generating
damping force; a pilot chamber into which a portion of the flow of
the fluid is introduced so that internal pressure is applied to the
main valve in a valve-closing direction; a pilot valve that opens
and closes to adjust the internal pressure of the pilot chamber;
and a communication passage that allows the pilot chamber or a
passage between the pilot chamber and the pilot valve to
communicate with the piston-side fluid chamber.
[0239] More specifically, the embodiments provide a damping force
variable shock absorber including: an outer tube provided on a
vehicle body side; an inner tube slidably inserted in an inner
circumference of the outer tube; a first bush provided on an inner
circumference on the axle side of the outer tube; a second bush
provided on an outer circumference on a vehicle body side of the
inner tube; an annular fluid chamber surrounded by the outer tube,
the inner tube, the first bush, and the second bush; a bottomed
cylindrical partition wall member, a portion of which is provided
in the inner tube; a piston rod having a smaller cross-sectional
area than a cross-sectional area of the annular fluid chamber, and
having an end close to the vehicle body side attached to the outer
tube, the piston rod being slidably inserted in the partition wall
member; a piston provided in an end on the axle side of the piston
rod and slidably provided in an inner circumference of the inner
tube; a fluid storage chamber partitioned by the partition wall
member in the inner tube and formed closer to the vehicle body side
than the partition wall member; a fluid chamber partitioned by the
partition wall member in the inner tube and formed closer to the
axle side than the partition wall member; a rod-side fluid chamber
partitioned by the piston in the fluid chamber and formed closer to
the vehicle body side than the piston; a piston-side fluid chamber
partitioned by the piston in the fluid chamber and formed closer to
the axle side than the piston; a communication hole formed in the
inner tube so as to allow the annular fluid chamber and the
rod-side fluid chamber to communicate with each other; a check
valve provided in the partition wall member so as to allow only
flow of fluid from the fluid storage chamber to the rod-side fluid
chamber; a throttle provided in the partition wall member so as to
restrict the flow of the fluid between the fluid storage chamber
and the rod-side fluid chamber; and a damping force variable device
that controls the flow of the fluid enclosed in the outer tube and
the inner tube so that damping force can be varied. The damping
force variable device includes: a main valve that opens and closes
to control the flow of the fluid caused by sliding of the piston in
the inner tube, thereby generating damping force; a pilot chamber
into which a portion of the flow of the fluid is introduced so that
internal pressure is applied to the main valve in a valve-closing
direction; a pilot valve that opens and closes to adjust the
internal pressure of the pilot chamber; and a communication passage
that allows the pilot chamber or a passage between the pilot
chamber and the pilot valve to communicate with the rod-side fluid
chamber.
[0240] Alternatively, there may be provided a damping force
variable shock absorber including: an outer tube provided on a
vehicle body side; an inner tube slidably inserted in an inner
circumference of the outer tube; a first bush provided on an inner
circumference on the axle side of the outer tube; a second bush
provided on an outer circumference on a vehicle body side of the
inner tube; an annular fluid chamber surrounded by the outer tube,
the inner tube, the first bush, and the second bush; a bottomed
cylindrical partition wall member, a portion of which is provided
in the inner tube; a piston rod having a smaller cross-sectional
area than a cross-sectional area of the annular fluid chamber, and
having an end close to the vehicle body side attached to the outer
tube, the piston rod being slidably inserted in the partition wall
member; a piston provided in an end on the axle side of the piston
rod and slidably provided in an inner circumference of the inner
tube; a fluid storage chamber partitioned by the partition wall
member in the inner tube and formed closer to the vehicle body side
than the partition wall member; a fluid chamber partitioned by the
partition wall member in the inner tube and formed closer to the
axle side than the partition wall member; a rod-side fluid chamber
partitioned by the piston in the fluid chamber and formed closer to
the vehicle body side than the piston; a piston-side fluid chamber
partitioned by the piston in the fluid chamber and formed closer to
the axle side than the piston; a communication hole formed in the
inner tube so as to allow the annular fluid chamber and the
rod-side fluid chamber to communicate with each other; a check
valve provided in the partition wall member so as to allow only
flow of fluid from the fluid storage chamber to the rod-side fluid
chamber; a throttle provided in the partition wall member so as to
restrict the flow of the fluid between the fluid storage chamber
and the rod-side fluid chamber; and a damping force variable device
that controls the flow of the fluid enclosed in the outer tube and
the inner tube so that damping force can be varied. The damping
force variable device includes: a main valve that opens and closes
to control the flow of the fluid caused by sliding of the piston in
the inner tube, thereby generating damping force; a pilot chamber
into which a portion of the flow of the fluid is introduced so that
internal pressure is applied to the main valve in a valve-closing
direction; a pilot valve that opens and closes to adjust the
internal pressure of the pilot chamber; and a communication passage
that allows the pilot chamber or a passage between the pilot
chamber and the pilot valve to communicate with the piston-side
fluid chamber.
* * * * *