Hydraulic damper of adjustable damping force type

A hydraulic damper of adjustable damping force type includes a cylinder containing hydraulic liquid, a piston working in the cylinder and partitioning the interior thereof into two liquid chambers and having thereon a damping force generating mechanism, a piston rod connected to the piston and extending through one of the liquid chambers to the outside of the cylinder, a coaxial bore formed in the piston rod, a liquid passage communicating the two liquid chambers independently from the damping force generating mechanism and including at least a portion of the bore in the piston rod, an adjusting rod inserted into the coaxial bore and rotatable from the outside of the damper, and a rotary valve secured to the adjusting rod and having a plurality of circumferentially spaced and radially extending orifices for selectively changing the effective passage area of the liquid passage. A check valve on the inner circumference of the rotary valve rotates integrally therewith in the circumferential direction. Circumferentially spaced and radially extending orifices are formed in the check valve at the locations aligned and have orifices in the rotary valve with the passage areas smaller than corresponding orifices in the rotary valve. The check valve opens to permit the liquid flow through selected orifices during either one of contraction and extension strokes of the damper and closes during the other of the contraction and extension strokes of the damper.

BACKGROUND OF THE INVENTION 
This invention relates to a hydraulic damper of the adjustable damping 
force type particularly adapted for use in a vehicle such as an 
automobile. 
Various proposals have been made with respect to hydraulic dampers of the 
adjustable damping force type since it is preferable to change the damping 
force characteristics of the hydraulic dampers in a suspension system of a 
vehicle such an an automobile in response to the running condition of the 
vehicle, such as running on a rough road, running on a paved road at a 
relatively low speed, running at a high speed and the like, which can 
improve driving comfort and steering stability. 
This invention relates to a hydraulic damper of the adjustable damping 
force type including a cylinder containing hydraulic liquid therein, a 
piston working in the cylinder and partitioning the interior thereof into 
two liquid chambers, a piston rod connected to the piston and extending 
through one of the liquid chambers to the outside of the cylinder, a 
coaxial bore formed in the piston rod, a liquid passage for communicating 
the two liquid chambers and including at least a portion of the bore, an 
adjusting rod inserted into the coaxial bore and adapted to be operated 
rotatably from the outside of the damper, and a rotary valve secured to 
the adjusting rod and having a plurality of circumferentially spaced and 
radially extending orifices having different diameters for selectively 
changing the effective passage area of the liquid passage, thereby 
adjusting the damping force. 
One prior art hydraulic damper of the aforementioned kind further comprises 
a check valve which is resiliently displaceable in the axial direction. 
The check valve opens, e.g. during the contraction stroke of the damper, 
to increase the effective passage area and closes during the extension 
stroke of the damper, thereby reducing the effective passage area. 
However, when the check valve is axially displaceably provided the overall 
axial length of the damper tends to increase and, when the check valve is 
provided to cooperate with the rotary valve an axial force will act on the 
rotary valve, particularly when the check valve is in the closed condition 
thus increasing the force required to operate the check valve. Further, 
the check valve usually consists of a valve body and a coil spring for 
biasing the valve body against a valve seat, thus increasing the number of 
parts and complicating the manufacturing and assembling operation, thereby 
increasing costs. 
SUMMARY OF THE INVENTION 
The object of the present invention is to solve the aforementioned 
problems, and according to the invention there is provided a hydraulic 
damper of the aforementioned kind, wherein a check valve is provided on 
the rotary valve to rotate integrally therewith in the circumferential 
direction. The check valve opens to permit the liquid to flow through a 
selected orifice during either one of the contraction and extension 
strokes of the damper and closes during the other of the contraction and 
extension strokes of the damper. The check valve has small diameter 
orifices at locations aligned with reflective orifices in the rotary 
valve. 
According to a preferred embodiment, the check valve radially inwardly 
displaces against a resilient force during the contraction stroke of the 
damper to permit the liquid flow determined by either one of the first 
orifices of the rotary valve and, during the extension stroke of the 
damper, the check valve is urged against the inner circumference of an 
orifice tube by its own resilient force and the hydraulic pressure acting 
on the check valve and restricts the liquid flow in the liquid passage by 
either one of the second orifices.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1-FIG. 5 shows a hydraulic damper according to the first embodiment of 
the invention and, which comprises a cylinder 1 containing hydraulic 
liquid therein, a piston 5 working in the cylinder 1 and partitioning the 
interior of the cylinder 1 into two liquid chambers A and B, and a piston 
rod 2 secured to the piston 5 and extending through the liquid chamber A 
and to the outside of the damper through one end (not shown) of the 
cylinder 1. The hydraulic damper may be of a single tube type wherein a 
free piston (not shown) is slidably provided in the cylinder 1 to 
partition the liquid chamber B from a gas chamber (not shown), or may be 
of a dual tube type wherein an outer tube (not shown) coaxially encircles 
the cylinder 1 to define an annular reservoir chamber containing therein 
pressurized gas and hydraulic liquid. 
An coaxial bore 3 is formed in the piston rod 2, and at least one radial 
hole 4 communicates permanently the liquid chamber A with the bore 3. A 
damping force generating valve mechanism consisting of through holes 6 and 
7 axially extending through the piston 5, a disc valve 8 normally 
preventing liquid flow through the holes 6 (FIG. 1 shows only one hole 6, 
but a plurality of circumferentially spaced holes 6 is PG,6 provided), and 
a disc valve 9 normally preventing liquid flow through the holes 7 is 
provided on the piston 5 to generate a main damping force during both the 
extension and contraction strokes of the damper. 
A tubular member 10 is screw-threadingly connected to one end of the piston 
rod 2 and acts also to secure the piston 5 to the piston rod 2. Two 
diametrically opposed holes 11 are formed in the circumferential wall of 
the tubular member 10. A guide tube 12 is secured to the inner 
circumference of the tubular member 10 by such as force fitting and the 
like. An annular groove 13 is formed in the other circumference of the 
guide tube 12 to act as a liquid passage, and two diametrically opposed 
holes 14 are formed in the circumferential wall of the guide tube 12 at 
locations corresponding with respective holes 11 in the tubular member 10. 
An adjusting rod 15 extends through the bore 3 in the piston rod 2, and one 
end of the adjusting rod 15 extends into the guide member 12 and the other 
end (not shown) sealingly extends through the bore 3 to the outside of the 
damper and is connected to a suitable operating device (not shown) such as 
an electric motor or the like. A rotary valve 16 is secured to the 
adjusting rod 15 by such as caulking or the like with the outer 
circumference thereof being slidingly and rotatably guided by the inner 
circumference of the guide member 12. As shown in FIGS. 2-4, the rotary 
valve 16 consists generally of a circumferential wall 16A and an end wall 
16B, and generally crosswise radially extending grooves 16C are formed in 
the inner surface of the end wall 16B. The grooves 16C define therebetween 
rand surfaces 16D which act to guide the sliding movement of a check valve 
22 as will be explained hereinafter. There are formed in the 
circumferential wall 16A of the rotary valve 16 relatively large diameter 
orifices 17A for generating a damping force during the contraction stroke 
of the damper and relatively small diameter orifices 17B for generating a 
damping force during the extension stroke of the damper. The orifices 17A 
are diametrically opposed, and the orifices 17B are also diametrically 
opposed and angularly spaced from respective orifices 17A by 60 degrees. 
The orifices 17A and 17B are referred generically as orifices 17. The 
rotary valve 16 is selectively rotated between three equally angularly 
spaced positions, i.e. a soft position S-S wherein the large diameter 
orifices 17A generally align with respective holes 14 in the guide member 
12, a medium position M-M wherein the small diameter orifices 17B align 
generally with respective holes 14 and a hard position H-H wherein the 
holes 14 in the guide member 12 are closed by the circumferential wall of 
the rotary valve 16. These three positions are spaced by 60 degrees from 
each other. 
Further, holes 18 are formed in the end wall 16B of the rotary valve 16 at 
locations corresponding to respective grooves 16C. Two diametrically 
opposed and radially inwardly projecting ridge 19 and 19 are formed in the 
circumferential wall 16A of the rotary valve 16 to act as stops for 
circumferentially locating the check valve 22 as will be explained 
hereinafter. 
A generally cylindrical valve seat 20 is fitted in the inner circumference 
of the rotary valve 16 by such as force fitting and the like. Relatively 
large holes 21 are formed in the valve seat 20 at locations corresponding 
to respective orifices 17. Rotation or movement in the circumferential 
direction of the valve seat 20 with respect to the rotary valve 16 is 
prevented by stops 19. 
The check valve 22 is disposed on the inner circumference of the valve seat 
20 to cooperate therewith. The check valve 22 consists of a pair of 
generally semi-circular arcuate valve bodies 22A and a coil spring 22B 
acting between valve bodies 22A. In the closed condition of the check 
valve 22 as shown in FIG. 2, there is some amount of clearance between 
each circumferential end of the valve bodies 22A and the stops 19 and, in 
the valve open condition shown in FIG. 5, the radially inward movement of 
the valve bodies 22A is restricted by the stops 19. There are provided in 
each of the valve bodies 22A a relatively large diameter orifice 23A and a 
relatively small diameter orifice 23B at locations corresponding to or 
generally aligning with the orifices 17A and 17B, respectively, in the 
rotary valve 16. The orifices 23A and 23B are referred to generically as 
orifices 23. The effective passage area of the orifices 23 is smaller than 
that of the orifices 17. The orifices 23 act to generate a damping force 
during the extension stroke of the damper. 
A bottom cap 24 is secured to the tubular member 10 by such as caulking or 
the like and acts to locate the guide member 12 in the tubular member 10 
and to separate the interior of the guide member 12 from the liquid 
chamber B. A pair of spring guides 25 projects in the axial direction from 
the inner surface of the bottom cap 24. 
An annular liquid passage 26 is formed between the bore 3 and the adjusting 
rod 15 and is communicated permanently with the liquid chamber A through 
the hole 4 in the piston rod 2. Further, the liquid passage 26 is also 
communicated with the interior of the rotary valve 16 through holes 18. 
The operation of the first embodiment of the invention will now be 
explained. 
Firstly, the adjusting rod 15 is operated from the outside of the damper to 
rotate the rotary valve 16 together with the check valve 22 such that the 
orifices 17A and 23A in the rotary valve 16 and the check valve 22 
generally oppose the holes 14 and 11 in the guide member 12 and the 
tubular member 10, respectively, thereby setting the soft position S-S. 
During the extension stroke of the damper, the liquid in the liquid chamber 
A flows into the liquid chamber B through the hole 4 and the passage 26 in 
the piston rod 2, the holes 18 in the rotary valve 16, orifices 23A in the 
check valve 22, holes 21, orifices 17A in the rotary valve 16, holes 14 
and annular passage 13 in the guide member 12, and holes 11 in the tubular 
member 10. The liquid passed through holes 18 presses the valve bodies 22A 
of the check valve 22 radially outwardly against the inner surface of the 
valve seat 20. The passage area of orifices 23A is smaller than that of 
orifices 17A, thus a damping force generates from the resistance of liquid 
passing through orifices 23A. When the speed of the piston 5 exceeds a 
predetermined level, the disc valve 8 opens to generate a predetermined 
damping force. 
During the contraction stroke of the damper, the pressure in the liquid 
chamber B as compared with the liquid chamber A increases and, as the 
result, the liquid in the chamber B flows into the chamber A through the 
holes 11, the annular passage 13, the holes 14, orifices 17A, holes 21, 
orifices 23A, holes 18, the passage 26 and the hole 4. However, at this 
condition, the liquid passed through holes 21 in the valve seat 20 presses 
the valve bodies 22A radially inwardly against the spring force of the 
spring 22B to form the condition shown in FIG. 5. Thus, the liquid passed 
through the holes 21 mainly flows from the space between the valve seat 20 
and the valve bodies 22A to the holes 18 in the rotary valve 16 through 
grooves 16C in the rotary valve 16. The orifices 17A act to define the 
damping force under this condition. When the speed of the piston 5 exceeds 
a predetermined level, the disc valve 9 opens to determine the damping 
force at this condition. 
Next, when the rotary valve 16 is rotated by 60 degrees in the clockwise 
direction with respect to FIG. 2 to set the medium position M-M so that 
the orifices 17B align with the holes 14 in the guide member 12, the 
damper acts similarly to the above discussed soft condition S-S. 
Further, when the rotary valve 16 is rotated by 60 degrees in the clockwise 
direction from the medium condition M-M to the hard condition H-H, no 
liquid flows between the chambers A and B through the passage 26, and the 
damping force is determined by disc valve 8 or 9. 
According to the invention, the check valve 22 is disposed to move in the 
radially inward and outward directions, thus, it is possible to reduce the 
axial length of the damper. 
Further, even though a hydraulic pressure acts on the check valve 22 during 
the extension stroke of the damper, the hydraulic pressure simply acts to 
tightly engage the valve bodies of the check valve against the valve seat 
20 in the radially outward direction, and the valve bodies 22A and the 
valve seat 20 rotate integrally with the rotary valve 16, so that no axial 
force acts on the rotary valve, and thus, the torque required for rotating 
the rotary valve can be minimized. 
Further, the check valve 22 consists of two arcuate valve bodies 22A and a 
spring 22B, and thus, assembling operation is easy and the manufacturing 
cost is low. 
FIG. 6 shows the second embodiment of the invention. The check valve 22 in 
the first embodiment is modified to an integral valve member 31 having a 
pair of generally arcuate valve portions 31A, and a generally U-shaped 
resilient connecting portion connecting first ends of the valve portions 
31A. The valve member 31 is preferably formed of a sheet metal. As shown 
in FIG. 6, one of the stops 19 in the first embodiment is omitted, and 
orifices 32A and orifices 32B are provided in the valve portions 31A. The 
operation of the second embodiment is similar to that of the first 
embodiment. 
FIG. 7 shows the third embodiment of the invention. The check valve in this 
embodiment consists of an integrally formed, generally C-shaped resilient 
member 46 preferably formed of a sheet metal. The check valve 46 is 
radially outwardly pressed by its own resiliency against a valve seat 44 
of a generally C-shaped configuration. The check valve 46 and the valve 
seat 44 are located on the inner circumference of a rotary valve 41 having 
a radially inwardly projecting and axially extending stop 42 on the inner 
circumference thereof. The stop 42 extends into the opening defining the 
C-shape in each of the check valve 46 and the valve seat 44. Only one 
large diameter orifice 43A and one small diameter orifice 43B are formed 
in the rotary valve 41 which are respectively spaced circumferentially 
from the stop 42 by 60 degrees. Corresponding orifices 47A and 47B and 
holes 45 are formed in the check valve 46 and the valve seat 44. Shown at 
numeral 48 in FIG. 7 is a guide integrally projecting from the bottom cap 
24. 
According to this embodiment, the orifices 47A and 47B are provided 
adjacent to opposite free ends of the check valve 46, and thus, it is 
possible to equalize the lift and the valve closing force of the check 
valve 46 between the soft and medium conditions. 
It will be understood that it is possible to provide two or more orifices 
47A or 47B at axially spaced positions. 
Accordingly to the fourth embodiment shown in FIG. 8, the guide member 12 
in the first embodiment is omitted, and the rotary valve 16 is directly 
inserted in the tubular member 10. The bottom cap 24 is located in an 
annular groove 10B in the inner circumference of the tubular member 10 and 
slidably engages with the rotary valve 16. As compared with the first 
embodiment, it is possible to increase the diameter of the rotary valve 
16, thus, the orifices 17 and 23 can easily be formed. 
In the embodiments aforementioned, the rotary valve is disposed in a 
tubular member which is connected to the tip end of the piston rod, but 
the check valve may be provided midway of the length of the piston rod. 
As described heretofore, according to the invention, it is possible to 
reduce the axial length of the adjustable damping force generating 
mechanism, thereby decreasing the overall axial length of the hydraulic 
damper. Further, it is possible to prevent unbalanced hydraulic force 
acting on the rotary valve, thereby reducing the operating force necessary 
to rotate the rotary valve. Further, the check valve is assembled on the 
inner circumference of the rotary valve thereby improving the assembly 
operation, and the construction is simple, thereby improving productivity 
and reducing costs.