JPH0450018A - Vehicle height adjusting device - Google Patents

Abstract

PURPOSE:To maintain a vehicle height at a vehicle height down position properly by inhibiting hydraulic oil from flowing into a jack chamber with a blow valve preset so that its opening pressure may be higher than sealing pressure of hydraulic oil after a passenger sets a vehicle height down position and gets off a vehicle. CONSTITUTION:When a switching valve 51 is changed over to a vehicle height up position in driving on a rough road, hydraulic oil flows into a vehicle height adjusting part 30 from a pump chamber A through an oil passage 31 by the piston compression process of a rear cushion 1, and flows into a switching valve mechanism 50 through a valve mechanism 40 which generates compression side attenuation force. Finally, the second blow valve 84 of a vehicle height up preventing device 80 is opened, and hydraulic oil flows into the jack chamber B of a rear cushion 1. Since sealing oil which flows to the jack chamber side from a sliding clearance around the switching valve 51 is set so that its opening pressure may be higher than sealing pressure of hydraulic oil, the second blow valve 84 does not open, so that it cannot flow into the jack chamber B.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a vehicle height adjustment device for a vehicle hydraulic shock absorber.

[Prior art and problems to be solved] Hydraulic shock absorbers for motorcycles are usually installed between the front and rear wheels of the vehicle and the axle, and adjust the vehicle height by adjusting the distance between the vehicle body and the axle. It is equipped with a vehicle height adjustment device. In this vehicle height adjustment device, as shown in FIG. 8 or 9, a pump chamber A in a cylinder of a rear wheel hydraulic shock absorber, that is, a rear suspension 1, which performs a self-pumping action while traveling, is located in a first pump chamber A. The oil passage 3I is connected to a switching valve mechanism 50 for switching between the vehicle height down position and the vehicle height amplifier position, and downstream of this switching valve mechanism, the oil passage 3I is branched into two, and the rear suspension It is connected to a jack chamber B of a hydraulic jack part 10 provided on the upper outer periphery of the front wheel and a jack chamber C of a hydraulic jack part 25 provided in the upper part of the inner cylinder of the front wheel shock absorber, that is, the front fork. The switching valve mechanism 50 is provided with a rotary switching valve 51, and a tappet 55 and a second check valve 56 are provided downstream of and adjacent to the switching valve.
This check valve prevents hydraulic oil from flowing from the two hydraulic jack chambers B and C into the pump chamber A. A second oil passage 36 branched from the first oil passage 31 upstream of the switching valve mechanism 50 is provided with a first check valve 39 to prevent pressure oil from flowing in the direction of the oil reservoir. .

While the two-wheeled vehicle is running, when the switching valve 51 is set to the vehicle height up position, the hydraulic oil discharged from the pump chamber A flows into the jacking chambers B and C attached to the hydraulic shock absorber, pushing down the suspension spring, The piston rod fixed to one end of the suspension spring is pulled out of the cylinder, pushing the vehicle upwards and increasing the vehicle height. Furthermore, when the switching valve 51 is set to the vehicle height down position, the hydraulic oil returns from the jack chambers B and C to the oil reservoir chamber, reducing the vehicle height. Then, when the occupant stops the vehicle and gets out of the vehicle, the weight on the vehicle body side is reduced accordingly.

Particularly, in the case of a vehicle such as a motorcycle, which has a light body and a large proportion of occupants, this reduction is large. Furthermore, when the side stand is set up, a considerable portion of the weight of the vehicle is shared with the side stand, making the vehicle even lighter. However, in order to prevent cavitation, hysteresis, etc. of the hydraulic shock absorber, the hydraulic oil is pressurized into the gas chamber E adjacent to the oil reservoir chamber communicating with the oil chamber A in the hydraulic shock absorber via a partition member. The hydraulic oil is pressurized by filling it with gas. The pressurized gas sealed in the gas chamber always pressurizes the hydraulic oil in the cylinder oil chamber A, jack chambers B and C of the hydraulic shock absorber, and the pipes communicating these.

As mentioned above, when the weight on the vehicle body side is reduced, the load on the plunger in the jack chamber B of the rear suspension, which receives the weight on the vehicle body via the suspension spring and has a particularly large shared load, is reduced. At this time, the switching valve 51 in the vehicle height down position closes the oil passage to the jack chamber B by the second check valve 53 (Fig. 9), but in reality, the switching valve 51 and this switching valve are A sliding gap exists between the matching hole in the vehicle body 52, and a hydraulic oil passage with sealing pressure is formed between the jack chamber B and the oil reservoir chamber on the upstream side of the switching valve mechanism 50. communicate through the sliding gap, the sealing pressure of the hydraulic oil is greater than the load applied to the jack piston, which has been reduced as described above, and the hydraulic oil gradually flows into the jack chamber B, causing the jack piston to as a result, the vehicle height increases. If the vehicle height increases when the motorcycle is stopped, not only will it be difficult for the next rider to get on the vehicle, but when riding in the city, after riding, the oil in the jack chamber B will be affected by the rider's weight and the weight of the vehicle itself. You will have to wait until the vehicle is returned to the oil sump and the vehicle height is reduced to its normal height.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vehicle height adjustment device for a hydraulic shock absorber for a vehicle, which has a device for preventing vehicle height from increasing when the vehicle is stopped, in order to eliminate the above-mentioned drawbacks.

[Means for Solving the Problems] In order to achieve the above object, in the vehicle height adjustment device for a hydraulic shock absorber for a vehicle according to the present invention, the pump chamber and the jack chamber are communicated via an oil passage. forming an oil passage that branches from the oil sump chamber and communicates with the oil sump chamber, and further branches the oil passage that communicates the pump chamber and the jacking chamber into two from the downstream side of the oil sump chamber, each of which communicates with the jacking chamber; A blow valve is installed in one oil path, and a check valve is installed in the other oil path in a direction that prevents the flow of hydraulic oil from the pump chamber, and the opening pressure of the blow valve is set to the sealed pressure of the hydraulic oil. The present invention is equipped with a vehicle height increase prevention device when the vehicle is stopped, which is characterized by the above settings.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to embodiments shown in the drawings.

FIG. 1 shows an overall view of a self-pump vehicle height adjustment device that can simultaneously adjust the vehicle height of a motorcycle rear cushion, which is a vehicle hydraulic shock absorber, and a front fork.

The rear wheel hydraulic shock absorber 1 has a cylinder 3 with a member 2 attached to the vehicle body at one end, a piston 4 slidably mounted in the cylinder 3, and a piston 4 that is attached to the vehicle body. A piston rod 6 having a member 5 protruding to the opposite side from the member 2 and having a free end for mounting the axle, and a spring receiver 7 provided at the end on the piston rod side;
A suspension spring 9 is stretched between it and a spring receiver 8 provided at the cylinder side end. The piston 4 is provided with a damping force generator as usual.

The rear wheel side jack part 10, which forms part of the self-pump type vehicle height adjustment device, has a sleeve 11 fixed to the outer periphery of the cylinder 3 of the rear cushion 1, and a plunger case 12 is fixed to this sleeve. A plunger 13 is slidably mounted between the inner peripheral surface of the plunger case and the outer peripheral surface of the sleeve, and a collar 8a is simultaneously slidably mounted between the end of the plunger 13 and the spring receiver 8. . In this way, the rear wheel side hydraulic jack chamber B is formed between the plunger case 12 and the upper end surface of the plunger 13.

The front fork 20, which is a hydraulic shock absorber for the front wheel, consists of an axle-side outer cylinder 21 and a vehicle-body-side inner cylinder 22 that can slide inside this outer cylinder 21, and includes a seat pipe ( a spring receiver (not shown) at the upper end (not shown);
A suspension spring 24 is stretched between the inner cylinder 22 and a spring receiver 23 at the upper end.

Further, the jack part 25 of the front fork 20, which constitutes a part of the self-pump type vehicle height adjustment device, is connected to a plunger case 26 attached to a fork bolt 22a fixed to the upper end of the inner cylinder 22, and inside this plunger case. A plunger 28 that is slidably fitted and has a through hole 27, and a rod 2 that projects outward from the plunger.
It consists of 9. As a result, a front wheel side hydraulic jacking chamber C is formed between the plunger case 26 and the plunger 28. The spring receiver 23 described above is attached to the tip of the rod 29.

A first oil passage 31 is provided which connects the pump chamber A in the cylinder of the rear suspension 1 to the hydraulic jack chamber B of the jack part 10 of the rear shock 1 and the hydraulic jack chamber C of the jack part 25 of the front fork 20. A vehicle height adjustment section 30 is provided in the first oil passage 31, and is actually disposed at the rear lower part of the seat of the motorcycle and can be operated while riding the motorcycle.

As shown in FIG. 3, the main body 32 of the vehicle height adjustment section 30 includes:
An oil tank 34 containing a free piston 33 is screwed onto the vehicle body 32, and the vehicle body 32 also serves as a lid member for the oil tank. One chamber E partitioned by a piston 33 serving as a partition wall member is filled with gas, and the other chamber forms an oil reservoir chamber.

In FIG. 1, an oil passage 31b of a pipe joint 35 of a car body 32, which is connected to a pump chamber A in a cylinder of a reaction pump l via an oil passage 31a, is connected to an oil passage 31c. , a valve mechanism 40 that generates a compression-side damping force is provided. Since this valve mechanism is not directly related to the gist of the present invention, detailed explanation will be omitted. On the other hand, a second oil passage 36 (Figs. 2 and 3), which intersects the first oil passages 31b and 31c at right angles and communicates with the oil reservoir below, is seated on the seat 37 by a spring 38. a first check valve 39 energized to permanently close the opening to the oil sump chamber;
is provided.

Furthermore, a -th oil passage 3 heading downstream from the valve mechanism 40
1d is led to the switching valve mechanism 50 via an oil passage 31e that reaches the hydraulic jack chamber B of the reaction shock 1. This switching valve mechanism 50 has a rotatable switching valve 51, and within this switching valve 51, two orthogonal oil passages 31h and 311 (see FIG. 2 or 3) are provided. The position of the switching valve 51 in FIGS. 1 and 2 is the vehicle height up position, and FIG. 3 is the vehicle height down position.

The switching valve 51 has a sliding gap in the hole in the main body 32 so that it can take two positions, a vehicle height up position and a vehicle height down position, by rotating 90 degrees and returning 90 inches. It is loaded with

When the vehicle height is up (FIGS. 1 and 2), one of the boats at both ends of the orthogonal oil passage 31h bored in the switching valve 51 is positioned on the upstream side of the first oil passage 31. 31
e, and the other boat is set to face the downstream side 31k of the first oil passage 31. As can be seen from FIG. 2, the opening surface of the boat is located at the bottom of the circumferential groove that is recessed inward from the outer circumferential surface of the switching valve 51. This groove is 180
It is provided over an angle of more than 1°. When the vehicle is in the lowered position (FIG. 3), one boat in the oil passage 31h faces the third oil passage 54 communicating with the oil sump chamber, and the other boat faces the relief oil passage 66. Set.

In the other orthogonal oil passage 31i in the switching valve 51, an orifice 31j is formed in one boat, and this orifice is checked with a chrysanthemum washer 52a whose outer periphery is caulked and fixed to the other boat opening surface of the oil passage 31i. It is always closed by a spring 52a biased between the valve 53 and the valve 53. Oil road 3
11, when set in the vehicle height up position (Figs. 1 and 2), the orifice 31j faces the third oil passage 54 communicating with the oil sump chamber, and the boat on the opposite side of the orifice is in the relief position. It faces the oil passage 66. When set to the vehicle height down position (FIG. 3), the orifice 31j faces the downstream side 31k of the first oil passage 31, and the boat on the opposite side to the orifice faces the upstream side 31e. A valve seat 59 is located at the downstream step of the small diameter cylindrical hole 75 in the downstream 31 of the first oil passage 31.
(FIG. 2a) is formed, and a third check valve 56 is pressed against this valve seat by a spring 57. Inside the small-diameter cylindrical hole 75 is a cylindrical tappet 5 that slides into a circumferential groove 51a formed over 180° on the outer periphery of the switching valve 51 at one end and opens and closes the third check valve 56 at the other end.
5 (Fig. 4) is slidably inserted. Tappet 5
5 is an oil passage 31 passing through the center, as is clear from FIG.
1, and a branch path 31m that is perpendicular to this oil path 31N and opens to the cutout surface 55a of the tappet 55. Furthermore, as shown in FIG. 1, the first oil passage 31 includes an oil passage 31g from the pipe joint 5, which is provided in the horizontally branched oil passage 31n.
It is connected to the hydraulic jack chamber B of the rear wheel cushion 1 via the pipe joint 58a and further through a device 80 for preventing vehicle height increase when stopped according to the present invention, which will be described later. Further, the front fork 2 on the front wheel side is connected to the oil passage 31g' through a pipe joint 58' from the oil passage 31n communicating with the front wheel side oil passage 31g.
It is connected to the hydraulic jack chamber C of 0.

As shown in FIGS. 2 and 3, the oil passage 31 is also connected to a first blow valve 70 via a horizontal oil passage 68, and this first blow valve is connected to an oil passage 69.54. It is connected to the oil sump chamber via. In the blow valve 70, the ball 73 held in the guide holder by the spring 7I always closes the valve seat, but if the hydraulic fluid downstream of the third check valve 56 abnormally increases in pressure when the vehicle height is raised, the spring It is provided as a safety circuit that opens against resistance and returns to the oil sump chamber.

Also, when the internal pressure of the hydraulic jack chambers B and C of the jack parts 10 and 25 exceeds a predetermined value when the vehicle height is raised, the oil in the cylinder oil chamber A of the rear shock 1 is transferred to the oil tank 3.
In order to return the oil to the oil sump chamber A of FIG. are provided in each bypass flow path. In this relief valve 60, high-pressure oil in the jack chamber is moved through an oil passage 64 against a spring, thereby opening bypass passages 66 and 65 that communicate with the oil sump chamber. Hydraulic oil is returned to the oil sump chamber.

Referring to FIGS. 1 and 5, a device 80 for preventing an increase in vehicle height when the vehicle is stopped according to the present invention will be explained.

A conduit 31g leading from the vehicle height adjustment section 30 to the rear suspension side hydraulic jack chamber B is connected to the plunger case 12 for the jack section 10 via a pipe joint 58a,
Two oil passages 81 and 82 are then led to the jack chamber B.
It is branched into. A fourth check valve 83 is arranged in one oil passage 81, and a second blow valve 84 is arranged in the other oil passage 82.

The fourth check valve 83 has a valve seat 86 having a through hole 85 and a guide holder 87 that fits into the protrusion of this valve seat. A hole is provided for accommodating a spring 89 for urging the valve seat 86 to seat in the opening. It communicates through the hole 90 and an annular gap 91 around the small diameter section. When assembling, these parts can be assembled together and the guide holder 87 can be easily installed by screwing into the hole that forms the oil passage 8I.

The second blow valve 84 provided in the oil passage 82 branched from the fourth change valve 83 has a cylindrical guide holder 93 having a through hole at the bottom, and a slide that is slidably fitted into the guide holder 93. A holder 94, a ball 95 held by the slide holder 94, a valve seat 96 having a valve seat for the ball 95, and a hole in the slide holder 94 for urging the ball 95 toward the valve seat 96. A spring 97 is inserted between the inner end of the guide holder 94a and the end surface of the guide holder 93. In the hole 94a of the slide holder 94, a plurality of diagonal through holes 98 are provided in the head 94b that holds the ball 95, and the hole 94a in the slide holder 94 is connected to the area around the head 94b through these through holes. It communicates with the annular gap.

Valve seat 96 has a hole 99 in which ball 95 is seated, and this hole 99 communicates with oil passage 82 via a plurality of radial transverse holes 100 and an annular gap 101 around the small diameter portion. The second blow valve 84 can be assembled into one piece in the same manner as the fourth check valve 83, and can be easily incorporated by rotating and fitting the valve seat 96 into the hole that forms the oil passage.

The arrangement of the vehicle height adjusting device for the hydraulic shock absorber according to the present invention as described above is shown in FIG. 6.7 as a schematic hydraulic circuit in comparison with FIG. 7.8 showing the prior art.

The operation of the hydraulic shock absorber vehicle height adjustment device configured as described above during driving will be briefly explained mainly with reference to Fig. 6.7.
(Fig. 7). While driving, hydraulic oil flows from the pump chamber A through the first oil passage 31 into the vehicle height adjustment section 30 due to the compression stroke of the piston 4 of the rear pump, and in the vehicle height adjustment section, the hydraulic oil flows into the second oil passage 36. Since the first check valve 39 is closed, the air flows into the switching valve mechanism 50 via the valve mechanism 40 that generates the compression damping force. In the vehicle height down position, the oil passage to the jack part is closed by the second check valve 53 in the switching valve 51, so the third oil passage 5
4 and flows into the oil sump chamber. In the extension stroke, the pressure in the pump chamber A is reduced, so the first check valve 39 is opened by suction, and the hydraulic oil flows from the oil reservoir chamber into the pump chamber A through the opened first check valve 39. The oil flows in to compensate for the volume of oil removed from the piston rod.

When starting to drive on rough terrain, set the switching valve 51 to the vehicle height amplifier position (
(Fig. 6), the compression stroke of the piston of the reaction pump 1 causes the hydraulic oil to flow from the pump chamber A to the oil passage 31.
It flows into the vehicle height adjustment section 30 via the vehicle height adjustment section, and in the vehicle height adjustment section, it passes through the valve mechanism 40 that generates the compression damping force, and then flows into the switching valve mechanism 5.
Flows into 0. The bed 5 passes through the oil passage in the switching valve 51.
5 through the central oil passage 31N (Fig. 4), and then press the third check valve 56 against the spring to open the oil passage 31.
g, flows into the jack part 25 of the front fork 20, and also flows into the oil passage 81 provided in the jack part IO of the rear cushion 1, but since the fourth check valve 83 is closed, the oil further branches out. Flows into road 82,
Press the second nib blow valve 84.

The opening pressure of this blow valve is set to be higher than the sealing pressure of the hydraulic oil given by the gas pressure in the oil tank, but the high-pressure hydraulic oil due to the compression stroke of the piston of the reaction I is affected by the force of the spring 97. Because we can overcome
The second nib blow pulp 84 is easily opened and flows into the jacking chamber B of the reaction cushion. During the extension stroke of the reaction cushion 1, the third check valve 56 is sucked and the oil in the jack part cannot flow back, but the first check valve 39 opens, so the oil in the oil reservoir chamber flows into the pump chamber A. The oil flows to compensate for the volume of oil that has escaped from the piston rod.

A self-pumping action is performed by repeating the compression and extension strokes of the shock cushion 1, and each suspension spring is gradually compressed by the jack chambers B and C, but the vehicle body is balanced by the suspension springs 9 and 24. Therefore, the suspension spring load increases, pushing up the vehicle body and increasing the vehicle height.

When switching from rough terrain to city driving, the switching valve 51
When the vehicle height is lowered, the oil in the jack chambers B and C is pushed up by the changeover valve 5I through the tappet 55 due to the weight of the occupants and the vehicle body, and passes through the opened third check valve 56, It passes through the notch surface and the through hole, pushes open the second check valve 53 in the switching valve, and flows into the oil reservoir chamber through the third oil passage 54. This reduces the vehicle height.

As mentioned above, after the vehicle stops, the rider gets off the motorcycle and
When the side stand is upright, the load applied via the suspension spring to the plunger of the jack chamber B on the rear wheel side, which has a particularly large shared load, is reduced by the weight of the occupant and the body size of the vehicle that is applied to the side stand, and the load applied to the plunger of the jack chamber B on the rear wheel side, which has a particularly large shared load, is reduced, and the load applied to the plunger of the jack chamber B of the oil tank is reduced by the weight of the occupant and the body size of the vehicle that is applied to the side stand. The pressure of the sealed oil in the vehicle height adjustment hydraulic circuit, which is constantly pressurized, exceeds the reduced load that the plunger in the jack chamber B receives, so the sealed oil flows between the switching valve 51 and its fitting hole. If there is no device for preventing the vehicle height from increasing when the vehicle is stopped according to the present invention, it will flow toward the jack chambers B and C through the sliding gap between them. The liquid flows into chamber B and pushes up the plunger to increase the vehicle height. However, according to the device for increasing the vehicle height at stop of the present invention, when the vehicle is at the vehicle height down position when the vehicle is stopped, the sliding gap around the switching valve 51 increases. Since the fourth check valve 83 in the oil passage 81 is closed, the sealed oil flowing from the oil passage to the jacking chamber side flows further into the branched oil passage 82 and reaches the nib blow pulp 84, but the opening pressure of this valve is higher than that. Since the spring 97 is set to a pressure higher than the sealing pressure of the hydraulic oil, the second nib blow pulp 84 does not open and cannot flow into the jacking chamber B.

(Effects of the Invention) In the vehicle height adjustment device for a vehicle hydraulic shock absorber of the present invention, the oil passage that communicates between the pump chamber and the jack chamber is branched to form an oil passage that communicates with the oil reservoir chamber, and the oil passage that communicates with the pump chamber and the jack chamber is branched. An oil passage communicating with the jacking chamber is branched into two from the downstream side of the oil reservoir chamber,
A blow valve is installed in one oil path, and a check valve is installed in the other oil path in a direction that prevents the flow of hydraulic oil from the pump chamber, and the opening pressure of the blow valve is set to the sealing pressure of the hydraulic oil. Since the vehicle height prevention device when the vehicle is stopped is characterized by the above settings, when the changeover valve is set to the vehicle height down position and the occupant gets off the vehicle, the plunger in the jack chamber As the load applied to the valve is reduced, the hydraulic oil with a constant sealing pressure tries to flow from the upstream oil sump chamber to the jack chamber, but since the valve is located downstream of the oil sump chamber, the valve opening pressure A blow valve set above the pressure prevents the flow into the jacking chamber. Therefore, the vehicle height remains set at the vehicle height down position. Moreover, when hydraulic oil is supplied to the jack chamber from the pump chamber of the hydraulic shock absorber, the pressure of the hydraulic oil becomes considerably higher than the sealing pressure of the hydraulic oil due to the pumping action, so the hydraulic oil from the pump chamber flows into the jack chamber. There is no problem with that. Additionally, a check valve installed in parallel with the blow valve helps return high-pressure oil in the jack chamber to the oil reservoir chamber without resistance when the vehicle is switched from the vehicle height up position to the vehicle height down position.

[Brief explanation of the drawing]

Figure 1 is an overall view of the rear cushion and front fork of a motorcycle equipped with a vehicle height adjustment device having a vehicle height increase prevention device when stopped according to the present invention, in which the switching valve of the vehicle height adjustment device is switched to the vehicle height up position. Figure 2 is a partial cross-sectional view of the vehicle height adjustment section taken along the line Figure 3 is an enlarged view of the vicinity of the three check valves, and Figure 3 is a sectional view of the vehicle height adjustment section similar to Figure 2, but Figure 4 shows the switching valve in the vehicle height down position. FIG. 5 is a perspective view of a tappet used in the switching valve mechanism, FIG. 5 is a cross-sectional view of the device for preventing the vehicle height from increasing when the vehicle is stopped according to the present invention, taken along the line V-■ in FIG. 1, and FIG. FIG. 7 is a schematic hydraulic circuit diagram for a car cushion and front fork equipped with a vehicle height adjustment device having a vehicle height increase prevention device when stopped according to the present invention, and shows a state in which the vehicle height is increased. Figure 8 is a schematic hydraulic circuit diagram similar to that shown in Figure 6, switched to the vehicle height down position, and Figure 8 is a schematic hydraulic circuit diagram for a hydraulic shock absorber with a conventional vehicle height adjustment device, switched to the vehicle height up position. FIG. 9, which shows the switched state, is a schematic hydraulic circuit diagram similar to FIG. 8 when the vehicle height is switched to the lowered position.

Claims (1)

[Claims] (1) The oil chamber in the cylinder of the hydraulic shock absorber, which is disposed between the vehicle body and the axle side and in which the piston rod slides, is connected to the pressurized gas chamber by a partition member via a flow path. A suspension system is provided between the vehicle body and the axle, which communicates with the oil sump chamber and forms a pump chamber in which pressure oil is supplied to the oil chamber in the cylinder in the hydraulic shock absorber by the expansion and contraction action of the hydraulic shock absorber. A hydraulic jack section is provided on one member of the hydraulic shock absorber that serves as the upper or lower mass member of the spring, and pressurized oil is supplied from the pump chamber to the jack chamber of the jack section, and from the jack chamber to the oil sump chamber. In a vehicle height adjustment device for a vehicle hydraulic shock absorber that discharges pressure oil and adjusts the relative distance between the vehicle body and the axle, the pump chamber and the jack chamber are communicated via an oil path,
An oil passage branching from this oil passage and communicating with the oil sump chamber is formed, and an oil passage communicating between the pump chamber and the jack chamber is formed.
The oil sump chamber is branched into two from the downstream side and communicates with the jack chamber, one oil passage is interposed with a blow valve, and the other oil passage is arranged in a direction to prevent the flow of hydraulic oil from the pump chamber. Vehicle height adjustment of a hydraulic shock absorber for a vehicle equipped with a vehicle height prevention device when the vehicle is stopped, characterized in that a check valve is installed and the opening pressure of the blow valve is set to be higher than the sealing pressure of hydraulic oil. Device.