JP3062992B2 - Hydraulic shock absorber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic shock absorber having a function of adjusting the height of a vehicle mounted on a suspension system of a vehicle such as a vehicle.

[0002]

2. Description of the Related Art Generally, in a vehicle such as an automobile, a hydraulic shock absorber is mounted between a sprung portion and a unsprung portion of a suspension device to attenuate vibration of the suspension spring, thereby improving ride comfort and steering stability. Like that.

[0003] Meanwhile, in a vehicle having a relatively large loading weight such as a van or a wagon vehicle, the vehicle height changes greatly due to a change in the loading load due to the getting on and off of the occupant and the loading and unloading of luggage, and the riding comfort and steering stability. Performance may be reduced. Therefore, there is a demand for a suspension device that can automatically maintain a constant vehicle height regardless of the magnitude of the loaded load.

Therefore, conventionally, for example, Japanese Patent Application Laid-Open No. 60-261
No. 713, an oil tank and a reservoir filled with high-pressure gas, pump means for supplying the oil liquid in the oil tank into the cylinder by expansion and contraction of the piston rod, and a pump in accordance with the position of the piston rod Means and relief means for relieving the pressurized oil in the cylinder to the oil tank, the pump means is operated by utilizing the vibration of the suspension device during running, and the inside of the cylinder is appropriately pressurized to extend the length of the piston rod. There has been proposed a so-called self-pumping type hydraulic shock absorber in which a constant vehicle height is automatically maintained by adjusting the constant.

[0005]

However, in the above-described self-pumping type hydraulic shock absorber, when the loaded load is large and the pressure in the cylinder is high due to the pumping, the self-pumping hydraulic shock absorber is pushed up from the road surface during traveling. When the piston rod is shortened by a large force in response to the pressure, the pressure in the cylinder excessively increases, and a large load is applied to a seal portion of the hydraulic shock absorber and a joint portion of each member, which causes an oil liquid leak. At the same time, there is a problem that the impact due to the thrust is transmitted to the vehicle body without being sufficiently attenuated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an automobile height-adjustable hydraulic shock absorber that prevents an excessive increase in pressure in a cylinder.

[0007]

In order to solve the above-mentioned problems, a hydraulic shock absorber according to the present invention has a case in which an oil liquid is stored therein, and the inside of the case is divided into one end chamber and the other end chamber. A partition member, a cylinder inserted into the other end chamber to form a reservoir chamber between the case inner wall and the other end chamber;
A piston defining a base valve for providing communication between the cylinder and the reservoir chamber provided at one end of said cylinder, said cylinder being slidably fitted in the cylinder into two chambers at, one end A hollow piston rod connected to the piston and having the other end extended to the outside of the case communicates with the two chambers provided in the piston in the cylinder, and controls the flow of the oil liquid between the two chambers. An oil liquid passage having a damping force generating mechanism for generating a damping force, and one end connected to the partition member and the other end slidably fitted to a pump tube provided in a hollow portion of the piston rod. A pump rod forming a pump chamber in the tube, a first pump passage provided in the pump rod for communicating the one end chamber with the pump chamber, and a first pump passage provided in the first pump passage. A first check valve that allows only the flow of the oil liquid from the one end chamber to the pump chamber, a second pump passage provided in the piston rod for communicating the pump chamber with the inside of the cylinder, and a second pump passage. A second check valve, which is provided between the pump tube and the pump rod, and is provided between the pump tube and the pump rod, and the piston rod is provided in accordance with their relative positions. Is extended to a first predetermined position, a first passage means for communicating the pump chamber with the inside of the cylinder, and when the piston rod further extends to a second predetermined position,
A second passage means for communicating the inside of the cylinder with a first pump passage, wherein the partition member is provided on the other end chamber side.
The hydraulic fluid in the reservoir chamber, characterized in that a pressure reducing valve to escape to the end chamber side that.

[0008] With this configuration, the pump rod moves forward and backward in the pump tube in accordance with the expansion and contraction of the piston rod, whereby the oil liquid in one end chamber is introduced into the pump chamber via the first pump passage and the first check valve. As well as
The oil liquid in the pump chamber is supplied to the cylinder chamber via the second check valve and the second pump passage, the pressure in the cylinder is increased, and the piston rod is extended. When the piston rod has been extended to the first predetermined position, the pump chamber and the cylinder chamber are communicated by the first passage means to stop increasing the pressure in the cylinder chamber. When the piston rod has been extended to the second predetermined position, The cylinder chamber and the first pump passage are communicated by the two passage means, the pressure oil in the cylinder chamber is returned to the one end chamber, the pressure in the cylinder is reduced, and the piston rod is shortened.
Further, when the pressure in the cylinder and the reservoir chamber on the other end chamber side reaches a predetermined pressure, the pressure reducing valve opens to open the reservoir chamber.
Pressure oil is allowed to escape to one chamber side.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings.

As shown in FIGS. 1 to 6, a hydraulic shock absorber 1 of the present embodiment has a partition member 3 fitted in a case 2 in which an oil liquid is stored. Inside the case 2 is a bottom side chamber 2a (one end chamber) and an opening side chamber 2b.
(The other end chamber).

A cylinder member 4 slightly smaller in diameter than the case 2 is inserted into the bottom side chamber 2a, and an annular chamber 5 is formed between the case 2 and the cylinder member 4.
Is connected to the inside of the cylinder member 4 by a passage 6 provided at the lower end of the cylinder member 4. Cylinder member 4
A free piston 7 is slidably fitted therein, and the inside of the cylinder member 4 is defined by an oil chamber 4 a on the partition member 3 side and a gas chamber 4 b communicated with the annular chamber 5 by the passage 6. ing. An oil liquid is sealed in the oil chamber 4a, and a high-pressure gas is sealed in the gas chamber 4b and the annular chamber 5.

A cylinder 8 having a diameter slightly smaller than that of the case 2 is inserted into the opening side chamber 2b, and a seal member 9 is attached to the opening of the case 2 so that an annular reservoir is provided between the case 2 and the cylinder 8. A chamber 10 is formed. A base valve 11 is attached to an end of the cylinder 8 on the partition member 3 side, and the inside of the cylinder 8 and the reservoir chamber 10 are communicated by an oil passage 12 provided in the base valve 11.
As shown in FIG. 3, the base valve 11 has a check valve 13 for allowing the flow of the oil liquid from the reservoir chamber 10 of the oil passage 12 into the cylinder 8, and an orifice 14 for constantly communicating the oil passage 12.
Is provided. An oil liquid is sealed in the cylinder 8, and an oil liquid and a high-pressure gas are sealed in the reservoir chamber 10.

As shown in FIG. 3, the partition member 3 includes an oil chamber 4a of the bottom chamber 2a and an opening chamber 2b (in the reservoir chamber 10 ).
Is provided with an oil passage 44 for communicating with the oil passage. When the pressure of the oil liquid on the side of the opening side chamber 2b reaches a predetermined pressure, the oil passage 44 is opened and the pressure oil on the side of the opening side chamber 2b is supplied to the oil chamber 44.
A pressure reducing valve 45 for escaping to 4a is provided. The pressure reducing valve 45 has a valve seat formed by expanding an opening of the oil passage 44 on the oil chamber 4a side, and a check ball 46 is inserted into the opening. The check valve 46 is pressed against the valve seat with a predetermined set load by a disk valve 47 attached to the end.
Normally, as shown in FIG. 4A, the oil passage 44 is closed by the check ball 46, and when the pressure difference between the opening side chamber 2b and the oil chamber 4b reaches a predetermined pressure, FIG. As shown in FIG. 5, the disc valve 47 is bent to open and release the pressure oil in the opening side chamber 2b to the oil chamber 4b.

An annular piston 15 is slidably fitted in the cylinder 8. The piston 15 allows the inside of the cylinder 8 to pass through a cylinder upper chamber 8 a on the opening side of the case 2 and a base valve 11. Two chambers, a cylinder lower chamber 8b, which communicate with the reservoir chamber 10, are defined. A substantially cylindrical piston bolt 16 is inserted through the piston 15, and a piston nut 17 is screwed to the tip of the piston bolt 16 and fixed. One end of a piston rod 18 having a hollow portion 18a is screwed into a screw portion 16a on the base end side of the piston bolt 16, and the other end of the piston rod 18 is connected to the seal member 9 and the rod guide 19.
To extend outside the case 2 and the cylinder 8.

The piston 15 has an oil liquid passage 20 and a contraction-side passage 21 for communicating the cylinder upper chamber 8a and the cylinder lower chamber 8b.
(Oil liquid passage) is provided. A normally-closed disk valve 22 (damping force generating mechanism) that is bent and opened by a predetermined pressure on the cylinder upper chamber 8a side to allow the flow of the oil liquid in the oil liquid passage 20 to generate a damping force. Is provided. The notch 22a is provided in the valve seat of the disc valve 22.
An orifice passage (a damping force generating mechanism) is formed by which the notch 22a constantly communicates between the cylinder upper and lower chambers 8a and 8b and controls the flow of oil between these two chambers to generate a damping force. Have been. Also, the piston 15 has
A normally-closed disk valve 23 (damping force generation mechanism) is provided which bends and opens by a predetermined pressure on the side of the cylinder lower chamber 8b to allow the flow of the oil liquid in the contraction side passage 21 to generate a damping force. .

The piston rod 18 has a hollow portion 18a
A stepped pump tube 24 composed of a large diameter portion 24a and a small diameter portion 24b having a slightly smaller diameter is inserted, and the end of the small diameter portion 24b is pressed against a holding spring 25 provided at the bottom of the hollow portion 18a. Then, the end on the side of the large-diameter portion 24a abuts on the piston bolt 16 and is fixed. An annular oil passage 26 is formed between the hollow portion 18a and the pump tube 24, and communicates with the cylinder upper chamber 8a via a passage 26a provided on the side wall of the piston rod 18. Here, the oil passage 26 and the passage 26
a constitutes a second pump passage.

A base end of a tubular pump rod 28 is connected to the partition member 3 and the base valve 11 via a retainer 27. The connecting portion between the pump rod 28 and the retainer 27 is formed in a spherical shape and is slidable with each other, so that the displacement of the pump rod 28 due to the operation of the hydraulic shock absorber 1 is allowed by absorbing the inclination. Has become. The distal end of the pump rod 28 extends along the center axis of the cylinder 8, is inserted into the piston bolt 16, and is further inserted through the large-diameter portion 24a of the pump tube 24 so as to slide into the small-diameter portion 24b. Mated. A pump chamber 29 is formed in the small-diameter portion 24b by the tip of the pump rod 28, and a first pump passage is constituted by an oil passage 30 in the pump rod 28 and a passage 31 provided in the retainer 27. The pump chamber 29 and the oil chamber 4a communicate with each other. At the end of the small diameter portion 24b of the pump tube 24, an oil passage extends from the pump chamber 29.
A check valve 32 (second check valve) that allows only the flow of the oil liquid to the pump chamber 26 is provided. At the tip of the pump rod 28, the oil chamber 4 a of the oil passage 30 is connected to the pump chamber 29. There is provided a check valve 33 (first check valve) that allows only the flow of the oil liquid through the check valve 33.

As shown in FIG. 6, the check valve 32 has a substantially U-shaped retainer 34 at the distal end of the small diameter portion 24b of the pump tube 24.
Is fixed, and a valve spring 36 is interposed between the valve body 35 and the retainer 34 which are separated from and seated in the opening of the small-diameter portion 24b.
The valve body 35 is pressed against the opening of the small diameter portion 24a by the pressure on the side 26 to close the valve, and the valve body 35 is closed by the pressure on the pump chamber 29 side.
Is pushed up from the opening of the small diameter portion 24b against the elastic force of the valve spring 36 to open the valve. In the figure,
Reference numeral 37 denotes a stopper for restricting the movement of the valve element 35.

As shown in FIG. 5, the check valve 33 has a substantially U-shaped retainer 38 attached to the tip of the pump rod 28.
A valve spring 40 is interposed between a valve body 39 which is separated from and seated on the distal end opening of the pump rod 28 and a retainer 38, and a pump chamber 29 is provided.
The valve body 39 is pressed against the opening of the pump rod 28 by the pressure of the oil passage 30 to close the valve, and the valve body 39 is pressed by the pressure of the oil passage 30 side.
Is pushed up from the opening of the pump rod 28 against the elastic force of the valve spring 40 to open the valve.

[0020] Piston bolt 16 and pump tube 24
Between the large diameter portion 24a and the pump rod 28
An annular passage 41 communicating with 8b is formed. The pump rod 28 is formed with a notch 42 extending from the distal end fitted to the pump tube 24 to a predetermined portion in the axial direction, and the notch 42 allows the pump rod 28 and the small-diameter portion 24b of the pump tube 24 to be formed. Is formed with a gap 42a. The gap 42a and the annular passage 41 constitute a first passage means, and the notch 42 is formed when the extension length of the piston rod 18 is shorter than a predetermined standard range (the first predetermined range which is the lower limit of the standard range). Position), the small diameter portion 24b of the pump tube 24
The gap 42a is not overlapped with the large diameter portion 24a, and the communication between the gap 42a and the annular passage 41 is cut off. Also, when the piston rod 18 extends to a predetermined standard range (when it extends to a first predetermined position that is the lower limit of the standard range),
The pump tube 24 moves together with the piston rod 18 so that the large diameter portion 24a overlaps the notch 42, and the gap 42a is formed in the annular passage 41.
To the cylinder upper and lower chambers 8a and 8b.

An oil passage is provided on the side wall of the pump rod 28.
An orifice passage 43 is provided in connection with 30 . The orifice passage 43 and the annular passage 41 constitute second passage means. The orifice passage 43 is provided with a notch 42 oil chamber.
The end of the piston rod 18 is located at a position from the pump chamber 29 with respect to the end on the 4a side (the lower end in the figure), and the extension length of the piston rod 18 is equal to or less than a predetermined standard range (the second predetermined upper limit of the standard range). (The position below), the pump tube 24 is located at a position overlapping with the small diameter portion 24b of the pump tube 24, and the communication between the orifice passage 43 and the annular passage 41 is interrupted. When the extension length of the piston rod 18 exceeds a predetermined standard range (when it exceeds a second predetermined position, which is the upper limit of the standard range), the orifice passage 43 overlaps the large diameter portion 24a of the pump tube 24. The orifice passage 43 communicates with the annular passage 41 and communicates with the cylinder upper and lower chambers 8a and 8b.

The hydraulic shock absorber 1 includes a piston rod
18 is connected to the vehicle body side (not shown)
A bracket 50 attached to the lower end of the vehicle is connected to a wheel side (not shown), so that the bracket 50 is mounted on a vehicle suspension system. In the drawing, 51 is a rebound stopper, and 52 is a spring receiver for receiving a suspension spring (not shown).

Next, the operation of the present embodiment configured as described above will be described.

During the extension stroke of the piston rod 18, the oil liquid in the cylinder upper chamber 8a is pressurized with the movement of the piston 15, and this pressure oil flows through the oil liquid passage 20 to the cylinder lower chamber 8b, and the notch A damping force is generated by the orifice formed by 22a. At this time, the piston rod 18 is
The amount of oil liquid that has exited the reservoir chamber 10 due to gas expansion.
Then, the check valve 13 is opened through the oil passage 12 of the base valve 11 to replenish the cylinder lower chamber 8b. Further, when the piston speed increases and the hydraulic pressure on the cylinder upper chamber 8a side reaches a predetermined pressure, the disc valve 22 opens to suppress an excessive increase in the damping force.

During the compression stroke of the piston rod 18, the oil in the cylinder lower chamber 8b is pressurized with the movement of the piston 15, and this pressure oil flows through the oil liquid passage 20 to the cylinder upper chamber 8a, and the notch A damping force is generated by the orifice formed by 22a. At this time, the piston rod 18 is
The amount of oil that has penetrated into the orifice 14 of the base valve 11
And flows into the reservoir chamber 10 through the oil passage 12 to compress the gas. Also, when the piston speed increases and the hydraulic pressure in the cylinder lower chamber 8b reaches a predetermined pressure, the disc valve 23
Is opened to allow the oil liquid to flow through the contraction side passage 21, thereby suppressing an excessive increase in the damping force.

Next, the vehicle height adjusting function of the hydraulic shock absorber 1 will be described. When the vehicle is empty (at standard vehicle height), the gas chamber 4b of the bottom side chamber 2a and the reservoir chamber 10 have the same pressure, and the extension length of the piston rod 18 is within a predetermined standard range. In this state, the notch 42 of the pump rod 28 overlaps the large-diameter portion 24a of the pump tube 24, and the pump chamber 29 is separated from the cylinder upper and lower chambers 8a, 8a by the gap 42a and the annular passage 41.
No pumping operation is performed because it is connected to 8b.

When the load on the vehicle increases and the vehicle height becomes lower than the standard vehicle height and the extension length of the piston rod 18 becomes shorter than the standard range, the notch 42 of the pump rod 28 Closed with 24b. In this state, when the piston rod 18 expands and contracts due to the vibration of the suspension device during traveling, the pump tube 24
The pressure in the pump chamber 29 decreases due to the retraction of the pump rod 28 in the small-diameter portion 24b, and the check valve 33 opens to open the oil passage.
The oil liquid in the oil chamber 4a is introduced into the pump chamber 29 through 30. During the contraction stroke, the pump rod 28 advances to pressurize the inside of the pump chamber 29, and the check valve 32 opens to open the pump chamber 29.
The oil liquid inside is supplied to the cylinder upper chamber 8a through the oil passage 26 and the passage 26a, and pressurizes the cylinder upper and lower chambers 8a, 8b and the reservoir chamber 10 to extend the piston rod 18. In this way, the vehicle height is increased by repeating the pumping operation using the vibration during traveling. When the vehicle height reaches the standard vehicle height and the extension length of the piston rod falls within the standard range (when it reaches the first predetermined position), the pump rod
The notch 42 of 28 overlaps the large diameter portion 24a of the pump tube 24, and the pump chamber 29 is communicated with the cylinder upper and lower chambers 8a and 8b, so that the pumping operation is released.

When the load on the vehicle is reduced and the vehicle height is higher than the standard vehicle height, and the extension length of the piston rod 18 is longer than the standard range (when it is longer than the second predetermined position), the pump rod 28 notches 42 and orifice passage 43
Overlaps with the large diameter portion 24a of the pump tube 24, and the pump chamber 29
Are communicated with the cylinder upper and lower chambers 8a and 8b to release the pumping operation, and the cylinder upper and lower chambers 8a and 8b
The pressure oil in the cylinder upper and lower chambers 8a and 8b is returned to the oil chamber 4a via the oil passage 30 via the orifice passage 43 and the orifice passage 43, and the cylinder upper and lower chambers 8a and 8b and the reservoir chamber 10 are depressurized to reduce the vehicle height. Goes down. When the vehicle height falls to the standard vehicle height and the extension length of the piston rod 18 falls within the standard range, the orifice passage 43 of the pump rod 28 overlaps with the small diameter portion 24b of the pump tube 24 and is closed, and the cylinder upper and lower chambers 8a and 8b are closed. The return operation of the pressure oil in the inside stops.

As described above, by repeatedly performing the pumping operation and the returning operation by using the vibration of the suspension device during traveling, the vehicle height can be adjusted to be constant regardless of the loaded load.

Further, when the pressure in the opening side chamber 2b rises rapidly and reaches a predetermined pressure by the above-described pumping operation, the pressure reducing valve 45 of the partition member 3 opens to open the inside of the opening side chamber 2b (in the reservoir chamber 10). Is released to the oil chamber 4b through the oil passage 44. This can prevent an excessive increase in pressure in the working chamber. When the load is large and the pressure in the cylinder 8 is high by pumping, the piston rod is pushed up from the road surface during running.
Even when 18 is shortened by a large force, the pressure reducing valve 45 is opened to release the pressure oil in the opening side chamber 2b to the oil chamber 4b, thereby preventing an excessive rise in pressure in the opening side chamber 2b. The load on the seal part of the hydraulic shock absorber 1 and the joint part of each member can be reduced, and the impact on the vehicle body due to the thrust can be reduced.

[0031]

As described above in detail, according to the hydraulic shock absorber of the present invention, the pressure in the cylinder is increased by the pumping operation due to the expansion and contraction of the piston rod, the piston rod is extended, and the piston rod is moved to the first predetermined position. When extended, the pumping operation is released by the first passage means,
Further, when the piston rod is extended to the second predetermined position, the pressure oil in the cylinder chamber is returned to the one end chamber by the second passage means, and the piston rod is shortened. Is automatically adjusted between the first extended position and the second predetermined position. As a result, the height of the vehicle can be automatically adjusted to be constant regardless of the magnitude of the loaded load by using the vibration of the suspension device when the vehicle is running. Further, the pressure in the other end chamber by a push-up or the like from the road surface during traveling of the vehicle is rapidly boosted reaches a predetermined pressure, re the pressure reducing valve is in the other end chamber side opening
Since the pressure oil in the reservoir chamber is released to the one end chamber, it is possible to prevent an excessive increase in the pressure in the cylinder and the reservoir chamber.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of one embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of the apparatus of FIG.

FIG. 3 is an enlarged view of a base valve and a partition member mounting portion of the device of FIG. 1;

FIG. 4 is a view showing an open / closed state of a pressure reducing valve of the apparatus of FIG. 1;

FIG. 5 is an enlarged view of a check valve of the pump rod of the apparatus of FIG. 1;

FIG. 6 is an enlarged view of a check valve of the pump tube of the apparatus of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic shock absorber 2 Case 3 Partition member 2a Bottom side chamber (one end chamber) 2b Opening side chamber (other end chamber) 8 Cylinder 8a Cylinder upper chamber 8b Cylinder lower chamber 10 Reservoir 11 Base valve 15 Piston 18 Piston rod 20 Oil liquid passage 21 Compression side oil liquid passage (oil liquid passage) 22 Disk valve (damping force generation mechanism) 22a Notch (damping force generation mechanism) 23 Disk valve (damping force generation mechanism) 24 Pump tube 24a Large diameter section 26 Oil passage (second pump) Passage) 26a Passage (second pump passage) 28 Pump rod 29 Pump chamber 30 Oil passage (first pump passage) 31 Passage (first pump passage) 32 Check valve (second check valve) 33 Check valve (second (1 check valve) 41 annular passage (first and second passage means) 42a gap (first passage means) 43 orifice passage (second passage means) 45 pressure reducing valve

Continuation of the front page (56) References JP-A-60-261713 (JP, A) JP-A-7-139574 (JP, A) JP-B 48-13151 (JP, B1) JP-B 48-36485 (JP) , B1) JP-B-43-10832 (JP, B1) JP-B-49-9292 (JP, Y1) US Patent 4,200,269 (US, A) US Patent 3,939,978 (US, A) German Patent Application Publication 3630757 (DE, A 1) German Patent Application Publication 1430945 (DE, A1) German Patent Application Publication 1908156 (DE, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16F 9/00-9 / 58 B60G 17/044

Claims (1)

(57) [Claims] A reservoir in which an oil liquid is stored; a partition member for partitioning the inside of the case into one end chamber and another end chamber; and a reservoir inserted into the other end chamber and between the inner wall of the case. A cylinder that forms a chamber, a base valve that is provided at one end of the cylinder in the other end chamber and communicates with the inside of the cylinder and a reservoir chamber, and that is slidably fitted into the cylinder and slidably fits inside the cylinder. A piston defined in two chambers, a hollow piston rod having one end connected to the piston and the other end extending out of the case, and communicating with the two chambers provided in the piston in the cylinder; An oil liquid passage having a damping force generating mechanism for controlling the flow of oil liquid between the two chambers to generate a damping force, and a pump tube having one end connected to the partition member and the other end provided in the hollow portion of the piston rod. A pump rod slidably fitted to the pump tube to form a pump chamber in the pump tube; a first pump passage provided in the pump rod for communicating the one end chamber with the pump chamber; A first check valve provided in the passage and allowing only the flow of the oil liquid from the one end chamber to the pump chamber; a second pump passage provided in the piston rod for communicating the pump chamber with the inside of the cylinder; A second check valve provided in the second pump passage and allowing only the flow of the oil liquid from the pump chamber into the cylinder; and a second check valve provided between the pump tube and the pump rod. A first passage means for communicating the pump chamber with the inside of the cylinder when the piston rod extends to a first predetermined position, and further, when the piston rod extends to a second predetermined position, And a second passage means for communicating the serial cylinder and the first pump passage,
A hydraulic shock absorber, wherein the partition member is provided with a pressure-reducing valve for allowing oil in the reservoir chamber on the other end chamber side to escape to the one end chamber side.