JPH1086623A - Car height adjusting device and work fluid pouring method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently vacuum the entire system when one way valves are arranged between a cylinder device and an accumulator. SOLUTION: A cut-off valve SL and a switch valve 35 are connected to a passage 12 connecting a chamber 4a in a cylinder 2 and an accumulator (ACC) 11 as a low pressure source. The switch valve 35 switches the state of the one way valve 35a that allows only the flow from the ACC 11 to the chamber 4a to the state of the one way valve 35b that allow only the flow in the opposite direction, and vice versa. Car height is kept unchanged by closing the cut-off valve SL. The car height is decreased by opening the cut-off valve SL and selecting the state of the one way valve 35b. When the cut-off valve SL is opened, and the state of the one way valve 35a is selected, the work fluid in the ACC 11 is sucked timely when the pressure in the chamber 4a is decreased due to the pumping work of the chamber 4a, which is caused by the telescopic motion of a cylinder device 1 during the running of the vehicle, increasing the height of the vehicle. During vacuuming and pouring work fluid, a closing valve MV, which is connected to a bypass passage 37, which bypasses the switch valve 35, is opened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle height adjusting device and a method for injecting a working fluid thereof.

[0002]

2. Description of the Related Art In a vehicle height adjusting device for adjusting a vehicle height so that an actual vehicle height becomes a target vehicle height, basically, a cylinder in a cylinder device is provided with one of a sprung weight and a unsprung weight. And the piston rod of the cylinder device is connected to the other of the sprung weight and the unsprung weight. Then, the vehicle height is increased by supplying the hydraulic fluid to the cylinder, and the vehicle height is decreased by discharging the hydraulic fluid from the cylinder.

In such a vehicle height adjusting device, a pump driven by an engine is separately provided, and a high pressure for supplying hydraulic fluid to a cylinder necessary for increasing the vehicle height is accumulated in an accumulator. There are things that you want to keep. However, it is not preferable to separately provide a high-pressure generating pump driven by the engine from the viewpoint of cost, weight, fuel efficiency, and the like.

In order to adjust the vehicle height without using a pump driven by an engine, the hydraulic fluid supply is performed by utilizing the expansion and contraction of a cylinder device due to a vehicle height displacement occurring during traveling, as is called a self-pumping type. There has been proposed a pump for obtaining a pump action for drainage. That is, as disclosed in Japanese Patent Application Laid-Open No. 7-174181, a pump rod slidably fitted in a piston rod is provided integrally with a cylinder, and a pump chamber is defined in the piston rod to travel. The volume of the pump chamber is changed due to expansion and contraction of the middle cylinder device.

[0005] In addition to the high-pressure chamber in the cylinder whose volume is changed by the piston rod, a low-pressure storage chamber is separately provided, and the hydraulic fluid is sucked from the low-pressure storage chamber into the pump chamber via the suction valve, and the pump is sucked. The working fluid in the room is discharged to a high-pressure chamber via a discharge valve to raise the vehicle height.
At a position where the vehicle height has risen to a predetermined reference vehicle height, a leveling port for communicating the high-pressure chamber and the low-pressure storage chamber is provided to restrict the vehicle height from rising above a predetermined value due to the pump action. That is, in the above-described vehicle height adjusting device, a constant vehicle height (target vehicle height) determined by the leveling port is obtained.

The above publication discloses that when the actual vehicle height is higher than a reference vehicle height (a constant target vehicle height) determined by a leveling port, a high-pressure chamber and a low-pressure storage chamber are provided so as to reduce the vehicle height promptly. Are communicated via a communication pipe with an on-off valve. Also, the above publication discloses an accumulator as a high-pressure source in order to quickly raise the vehicle height when the actual vehicle height is lower than a reference vehicle height (a constant target vehicle height) determined by a leveling port. It is also disclosed that hydraulic fluid is supplied to the high-pressure chamber from the hydraulic pump.

The accumulator and the high-pressure chamber in the cylinder are connected to each other via a one-way valve that allows only the flow from the high-pressure chamber to the accumulator by a switching connection circuit. The communication mode in which the high-pressure chamber and the accumulator are directly connected can be switched and selected.
When the communication mode is set, the hydraulic fluid is supplied from the accumulator to the high-pressure chamber, that is, high pressure is supplied, and the vehicle height is raised.
In the connected state via the one-way valve, the high-pressure chamber operates from the high-pressure chamber to the accumulator at the timing when the high-pressure chamber becomes high pressure due to the pressure fluctuation of the high-pressure chamber caused by the expansion and contraction of the cylinder device during traveling. The liquid is discharged, and a high pressure is stored in the accumulator.

[0008]

As described above, in a vehicle height adjusting device in which a cylinder device and an accumulator are connected by a switching type connection circuit having a one-way valve, when the hydraulic fluid is injected, Prior to injection, it is desirable to pre-evacuate a series of paths from the cylinder device to the accumulator.

The evacuation is performed from one of the cylinder device side and the accumulator side, and the working fluid is injected from the other side. However, the evacuation is
In consideration of the opening direction of the one-way valve, the operation is performed from the side where the one-way valve can be opened by the negative pressure generated by evacuation.

However, since the one-way valve is not opened unless a predetermined valve-opening differential pressure is applied, the path on the side where the hydraulic fluid is injected from the one-side valve is sufficiently evacuated rather than the side where the evacuation is performed. In this regard, some measure is desired in this regard.

The present invention has been made in view of the above circumstances, and has as its object to provide a cylinder device and an accumulator.
A vehicle height adjustment device and a method for injecting hydraulic fluid therefor, which can sufficiently evacuate the entire path from the cylinder device to the accumulator even when a one-way valve is interposed between the vehicle and the accumulator. It is in.

[0012]

Means for Solving the Problems To achieve the above object, a vehicle height adjusting device according to the present invention is configured as follows. That is, a cylinder device installed between the sprung weight and the unsprung weight, an accumulator connected to the cylinder device via a switching connection circuit having a one-way valve, and vehicle height detecting means. Control means for controlling the switching connection circuit so that the vehicle height detected by the vehicle height detection means is equal to a target vehicle height. By the pumping action due to the pressure fluctuation, the hydraulic fluid is circulated between the cylinder device and the accumulator through the one-way valve, so that either one of the vehicle height increase and the vehicle height decrease is adjusted. Communication means for forcibly connecting the cylinder device side and the accumulator side with the one-way valve in a specific mode other than the vehicle height adjustment. Yes It is to. Preferred embodiments based on the above solution are as described in claims 2 to 7 in the claims.

In order to achieve the above object, a method for injecting hydraulic fluid into a vehicle height adjusting device according to the present invention is as follows. That is, a vehicle height adjustment including a cylinder device installed between a sprung weight and an unsprung weight, and an accumulator connected to the cylinder device via a switching connection circuit having a one-way valve. A method for injecting hydraulic fluid into a device, wherein the cylinder device side and the accumulator side are forcibly connected to each other with the one-way valve as a boundary, and one of the cylinder device side and the accumulator side is provided. After evacuating from one side, the working fluid is injected from the other side.

[0014]

According to the first aspect of the present invention, the cylinder device side and the accumulator side are in a communication state as a specific mode, that is, the cylinder device side and the accumulator are in a specific mode.
The pressure on the pressure side can be kept at the same pressure state without being affected by the one-way valve opening differential pressure, and the evacuation prior to hydraulic fluid injection is performed over the entire path from the cylinder device to the accumulator. Can do well across.

According to the second aspect, the communication state in the specific mode can be ensured by utilizing the bypass passage and the on-off valve.

According to the third aspect, the opening / closing valve can be made inexpensive and simple by using a manually operated mechanical valve.

According to the fourth aspect, the open / close valve is an electromagnetic type operated in accordance with a manual switch, so that a communication state in a specific mode can be easily obtained.

According to the fifth aspect, the communication state in the specific mode can be obtained by effectively using the communication path for adjusting the vehicle height.

According to the sixth aspect of the present invention, there is provided a specific configuration for adjusting the vehicle height by lowering the set pressure of the accumulator. Further, according to the present invention, a specific configuration is provided for adjusting the vehicle height by increasing the set pressure of the accumulator.

According to the eighth aspect of the present invention, the entire path from the cylinder device to the accumulator is in a communicating state so as to have the same pressure state, and the entire path is sufficiently evacuated. Hydraulic fluid can be injected.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION

Description of FIG. 1 (First Example of Overall System Diagram)

In FIG. 1, reference numeral 1 denotes a cylinder device having a cylinder 2 and a piston rod 3. The cylinder 2
It has an inner / outer double structure having an inner cylinder 4 and an outer cylinder 5, and both ends of the opening are closed by a head flange 6 and a bottom flange 7. In the inner cylinder 4, the piston rod 3
The piston portion 8 is slidably fitted, and a rod portion 9 integral with the piston portion 8 extends through the head flange 6 in a liquid-tight manner to the outside of the cylinder.

The cylinder 2 has an unsprung weight (wheel-side member)
While the rod portion 9 of the piston rod 3 is
It is connected to the sprung mass (body side member). Thereby, when the vehicle height is changed, the piston rod 3 is moved up and down relatively to the cylinder 2, and the cylinder device 1 is expanded and contracted. It is also possible to connect the cylinder 2 to the unsprung weight while connecting the cylinder 2 to the unsprung weight.

The inside of the inner cylinder 4 of the cylinder 2 is filled with a working fluid (working oil). The interior of the inner cylinder 2 is defined by the piston 8 into two chambers, but a chamber without the rod 9 is indicated by reference numeral 4a, and a chamber with the rod 9 is indicated by reference 4b. The space between the inner cylinder 4 and the outer cylinder 5 is defined as a volume compensation chamber 10.
It is filled with working fluid and gas (usually nitrogen gas). When the cylinder device 1 expands and contracts, the volume change of the chamber 4a is
Only the volume of the rod portion 9 that enters and exits the chamber 4b corresponds to the volume of the chamber 4b.
b is larger than the volume change of the volume compensating chamber 1a, as will be described later.
Compensated by going in and out of 0.

When the hydraulic fluid is supplied from the outside into the cylinder 2, the cylinder device 1 is extended to raise the vehicle height,
When the hydraulic fluid is discharged from the cylinder 2 to the outside, the cylinder device 1 is contracted and the vehicle height is reduced (vehicle height adjustment).
In the embodiment, the above-described cylinder device 1 is provided for each of the left and right front wheels and the left and right rear wheels, so that the vehicle height can be adjusted independently for each wheel.

In the lower part of the cylinder 1, the chamber 4
A damping force generating mechanism 36 including a communication path that communicates a with the volume compensation chamber 10 is provided (the flow of the hydraulic fluid for generating the damping force is performed only in the cylinder 2).

Numeral 11 denotes an accumulator disposed outside the cylinder device 1. The pressure stored in the accumulator 11 is a small pressure, and the accumulator 11 and the cylinder 2 are connected to each other. When the communication is established, the hydraulic fluid is supplied from the cylinder 2 side to the accumulator 11 side, so that the vehicle height is reduced. More specifically, the pressure is small enough to ensure that the vehicle height can be reduced to a reference vehicle height (in the embodiment, the wheels are in a neutral position in the vertical direction) at least when the vehicle is stopped and the vehicle is idle. In other words, the accumulator 11 functions as a reservoir. In addition, accumulate
The chamber 11 is defined by a free piston 11a as a movable partition into two chambers 11b and 11c.
b is filled with the working fluid, and the other chamber 11c is filled with a gas for applying pressure.

The accumulator 11 and the chamber 4a in the inner cylinder 4 are connected via a switching connection circuit R. The switching connection circuit R has a passage 12, a shutoff valve SL, and a switching valve 35. The passage 12 is provided in the chamber 4 a of the cylinder device 1.
And the accumulator 11 are connected to each other.
, Sequentially from the accumulator 11 side in series with each other.
The shutoff valve SL composed of an electromagnetic on-off valve and the switching valve 35 are connected.

The switching valve 35 includes two one-way valves 35a and 35
b. In other words, when the switching of the one valve 35a is selected, the hydraulic fluid flows only from the accumulator 11 to the chamber 4a. When the switching of the one-way valve 35b is selected, the accumulator is opened from the chamber 4a.
The state is such that it flows only to the data 11. As will be apparent from the following description, the one valve 35a is selected when the vehicle height is adjusted using the self-pumping of the cylinder device 1 (the vehicle height rises only by the flow of the hydraulic fluid from the chamber 4a to the accumulator 11). ), The one-way valve 35b is selected in the communication mode,
Only the flow from the chamber 4a to the accumulator 11 occurs (the flow is based on the average pressure difference between the chamber 4a and the accumulator 11, and the vehicle height decreases).

The passage 12 is provided with a bypass passage 37 for bypassing the switching valve 35.
7 includes a mechanical switching valve M that is manually opened and closed.
V is connected. One end of the bypass passage 37 has a passage 1 between the switching valve 37 and the cylinder device 1.
2 and the other end is connected to the passage 12 between the shutoff valve SL and the switching valve 35.

In the system diagram having the above structure, the vehicle height can be increased, the vehicle height can be reduced, and the vehicle height can be maintained in accordance with the switching mode of the shutoff valve SL and the switching valve 35. To argue. Also, the injection of the hydraulic fluid will be described.

(1) Maintaining vehicle height

When the vehicle height is maintained, the shut-off valve SL is closed to shut off the cylinder 2 and the accumulator 11, so that the hydraulic fluid does not flow between the cylinder 2 and the outside. 1 functions as a normal damper (shock absorber) without a vehicle height adjustment function.

(2) Decrease in vehicle height

When the vehicle height decreases, the on-off valve MV is closed, the shut-off valve SL is opened, and the switching valve 35 is switched to the one-way valve 35b. Thus, the high-pressure hydraulic fluid from the chamber 4a is discharged to the low-pressure accumulator 11 via the one-way valve 35b and the shut-off valve SL. Since the hydraulic fluid flows to the accumulator 11 against the valve opening differential pressure of the one-way valve 35b, the size of the chamber 4a caused by the expansion and contraction of the cylinder device 1 is larger than when the one-way valve 35b does not exist. Even if pressure fluctuations occur rapidly, the large pressure fluctuations are alleviated and transmitted to the accumulator 11, so that large pressure fluctuations on the accumulator 11 are suppressed.

(3) Vehicle height rise

The vehicle height rise is performed by utilizing the pumping action of the chamber 4a caused by the expansion and contraction of the cylinder device 1 caused by the unevenness of the road surface during traveling. Therefore, when the vehicle is stopped, the vehicle height cannot be increased. Becomes Assuming that this is running,
When the vehicle height is rising, the on-off valve MV is closed and the shut-off valve SL
Is opened, and the switching valve 35 is set to the switching selection state of the one-way valve 35a. The one-way valve 35a is opened at the timing when the pressure in the chamber 4a becomes low due to the expansion and contraction of the cylinder device 1, and the working fluid in the accumulator 11 is sucked into the chamber 4a, and the vehicle height is increased by this amount. At the timing when the pressure in the chamber 4a increases, the operation of the one-way valve 35a causes the chamber 4a
As a result, the flow of the hydraulic fluid from the engine to the accumulator 11 is regulated, and as a result, the vehicle height is increased. During traveling, the pressure in the chamber 4a fluctuates due to the vehicle height displacement caused by unevenness of the road surface, and the pressure in the chamber 4a instantaneously changes.
However, since the pressure of the accumulator 11 is lower than the average pressure of the chamber 4a, the flow of the working fluid toward the accumulator 11 is ensured.

(4) Injection of hydraulic fluid

Prior to the injection of the working fluid, the entire system from the cylinder device 1 to the accumulator 11 is evacuated. During this evacuation, the shut-off valve SL and the switching valve M
V is opened, and the cylinder device 1 side and the accumulator 11 side communicate with each other with the switching valve (one-way valve) 35 as a boundary.
The communication state is set such that the pressures in all the paths are the same. In a state where the switching valve MV is open, for example, vacuum is drawn from the cylinder device 1 side. After evacuating to a predetermined negative pressure, the working fluid is injected from the accumulator 11 side. In addition, vacuuming is performed from the accumulator 11 side,
The hydraulic fluid can be injected from the cylinder device 1 side. After the working fluid is injected, the switching valve MV is closed.

In FIG. 1, reference numeral U denotes a control unit constituted by using a microcomputer as control means. The control unit U receives signals from sensors or switches S1 and S2. . Sensor S1
Is for detecting the vehicle height, and constitutes a vehicle height detecting means. The vehicle height sensor S1 is provided independently for the left and right front wheels, and for the left and right rear wheels, detects the vehicle height at an intermediate position in the vehicle width direction of a stabilizer connecting the left and right rear wheels. (The average vehicle height of the right and left rear wheels is detected by one vehicle height sensor), but the vehicle height of each wheel may be individually detected.

The switch S2 is manually operated,
The target vehicle height is set, and in the embodiment, either high (high vehicle height) or low (low vehicle height) is input, and the low vehicle height corresponds to the reference vehicle height. Vehicle height is set. The control unit U controls the shutoff valve SL and the switching valve 35 so that the vehicle height detected by the vehicle height sensor S1 becomes the target vehicle height set by the switch S2 (the switching valve MV is closed). ).

Modification of FIG.

The manual switching valve MV shown in FIG. 1 may be an electromagnetic switching valve. In this case, the manually operated ON / OFF switch is interposed in the energization circuit of the electromagnetic switching valve MV, and the manual switch is turned ON at the time of evacuation and injection of the hydraulic fluid, thereby opening the switching valve MV. State. When a signal from a manual switch S3 (specific mode selection means) is separately input to the control unit U and the switch S3 is operated during evacuation and injection of the hydraulic fluid, the control unit U causes the electromagnetic switching valve MV to operate. Control may be performed such that the valve is opened.

Description of FIG. 2 (second example of overall system diagram)

FIG. 2 is a modification of FIG. 1. The same components as those of FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. In the example of FIG. 2, a switching valve 38 is used instead of the switching valve 35 of FIG. 1, and the bypass passage 37 and the switching valve M in FIG.
It does not have V. The switching valve 38 is set so as to selectively switch between the one-way valve 38a and the communication passage 38b which allow only the flow from the accumulator 11 side to the cylinder device 1.

When the vehicle height is maintained, the shutoff valve SL is closed. When the vehicle height is low, the switching valve 38 is set to the state where the communication path 38b is selected for switching. When the vehicle height rises, the one-way valve 38a
Are in a state of being switched and selected. When the working fluid is injected (evacuated), the switching valve 35 is forcibly set to the switching selection state of the communication path 38b.

In the case of FIG. 2, the control unit U includes a vehicle height sensor S1 and a target vehicle height setting switch S for vehicle height control.
2 and a signal from a manual switch S3 for selecting a specific mode for evacuation and injection of the hydraulic fluid. That is, when the switch S3 is turned on, the switching valve 38 is forcibly switched to the communication path 38b. In the example of FIG. 2, the switching valve 38 is connected to the bypass passage 37 and the switching valve MV shown in FIG.
The function is also used.

Changing the set pressure of the accumulator

The set pressure of the accumulator 11 can be set to a high pressure that guarantees a high vehicle height that is higher than the target vehicle height. In this case, in the example of FIG.
One-way valve 35a is selected (the functions of one-way valves 35a and 35b have the opposite relationship to the case where accumulator 11 is set to a low pressure), and one-way valve 35b at the time of decrease in vehicle height.
Is selected. That is, when the vehicle height decreases,
When the pressure of the chamber 4a fluctuates due to the expansion and contraction of the cylinder device 1 during traveling, at the timing when the pressure increases, the hydraulic fluid flows from the chamber 4a to the accumulator 11 to lower the vehicle height.

In the example shown in FIG. 2, the direction of the one-way valve 38a is set in the opposite direction to that shown in FIG. 2 (the same direction as the one-way valve 35b shown in FIG. 1). 38
b is switched and selected, and when the vehicle height decreases, the one-way valve 38a which is set in the opposite direction to the case shown in FIG. 2 is selected.

Although the embodiment has been described above, the present invention is not limited to this and includes, for example, the following cases.

As the switching connection circuit R, an appropriately modified circuit can be used. Further, the target vehicle height may be a fixed value of only the reference vehicle height, or may be changed in three or more stages.

The cylinder device 1 may be of a type having no outer cylinder 5. In this case, for example, room 4
a through a free piston slidably fitted in
A volume compensation chamber 10 is defined in the chamber 4a. Further, as shown in the above-mentioned Japanese Patent Application Laid-Open No. 7-174181, the cylinder device 1 may have a separate pump chamber configured using a piston rod and a pump rod provided in the cylinder. Good.

The vehicle height adjustment during traveling may be performed only when the vehicle body posture is stable. For example, the vehicle height can be adjusted only when the vehicle is traveling straight and in steady running.

During parking, only the vehicle height lowering control (when the set pressure of the accumulator 11 is small) or only the vehicle height raising control (when the set pressure of the accumulator 11 is large) may be performed.

The selection of a specific mode at the time of evacuation and injection of the hydraulic fluid is performed by operating an appropriate port provided in the control unit U, for example, by grounding a predetermined port. (Instead of the switch S3).

The bypass passage 37 shown in FIG.
5 as well as by-passing the shutoff valve SL (at the time of evacuation and injection of hydraulic fluid,
The shutoff valve SL is also opened).

Each member such as a switching valve can be expressed by adding a name of a means to a higher concept expression of its function. Further, the present invention can be expressed as a control method.

The purpose of the present invention is not limited to what is explicitly specified, but also implicitly includes providing what substantially corresponds to what is described as preferred or advantageous.

[Brief description of the drawings]

FIG. 1 shows a first example of an overall system diagram to which the present invention is applied.

FIG. 2 shows a second example of the overall system diagram to which the present invention is applied.

[Description of sign]

 1: Cylinder device 2: Cylinder 3: Piston rod 11: Accumulator 12: Passage 35: Switching valve 35a: One-way valve 35b: One-way valve 37: Bypass passage 38: Switching valve 38a: One-way valve 38b Communication passage MV: Open / close valve S1: Vehicle height sensor S2: Target vehicle height setting switch S3: Specific mode selection switch U: Control unit R: Switching connection circuit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tadanobu Yamamoto 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd.

Claims (8)

[Claims] 1. A cylinder device installed between a sprung weight and an unsprung weight, an accumulator connected to the cylinder device via a switching connection circuit having a one-way valve, and a vehicle height. Detection means, and control means for controlling the switching connection circuit so that the vehicle height detected by the vehicle height detection means is equal to a target vehicle height, wherein the cylinder caused by expansion and contraction of the cylinder device during traveling By the pumping action due to the pressure fluctuation in the device, the cylinder device and the accumulator are connected via the one-way valve.
A vehicle height adjustment device that circulates hydraulic fluid between the vehicle and a vehicle height adjustment device to adjust either the vehicle height increase or the vehicle height decrease. And a communication means for forcibly connecting the cylinder device side and the accumulator side to each other with the one valve as a boundary at the time of driving. 2. The communication device according to claim 1, wherein the communication means includes a bypass passage that bypasses the one-way valve and connects the cylinder device side and the accumulator side, and an on-off valve that opens and closes the bypass passage. The vehicle height adjusting device, wherein the on-off valve is opened in the specific mode. 3. The vehicle height adjusting device according to claim 2, wherein the on-off valve is of a mechanical type that is manually opened and closed. 4. The vehicle according to claim 2, wherein the on-off valve is of an electromagnetic type, a manual switch that is manually operated, and the on-off valve is opened and closed in response to the operation of the manual switch. High adjustment device. 5. The switching connection circuit according to claim 1, wherein the switching connection circuit is set to be switched between a selected state of the one-way valve and a selected state of a communication path provided in parallel with the one-way valve, In the communication path selection state, a vehicle height adjustment is performed in a direction opposite to the vehicle height adjustment direction when the one-way valve is selected, and a selection means for manually selecting the specific mode is provided. Means for controlling the switching type connection circuit to forcibly bring the communication path into the selected state when the specific mode is selected by the selection means. 6. The accumulator according to claim 1, wherein the accumulator is set to a low pressure so as to ensure a low vehicle height that is equal to or less than the target vehicle height. The valve is set to allow the flow from the accumulator to the cylinder device. When the vehicle height rises, the one-way valve is switched and selected, and the pressure fluctuation in the cylinder device due to the expansion and contraction of the cylinder device during traveling causes The hydraulic fluid is sucked into the cylinder device from the accumulator at the timing when the pressure in the cylinder device becomes low, and when the vehicle height decreases, the switching connection circuit is switched from the one-valve switching selection state when the vehicle height increases. Switched, based on the differential pressure of the average pressure between the accumulator and the cylinder device,
A state in which hydraulic fluid flows from the cylinder device to the accumulator, and when the vehicle height is maintained, the switching connection circuit is switched to a state in which the cylinder device and the accumulator are shut off. Characteristic vehicle height adjustment device. 7. The accumulator according to claim 1, wherein the accumulator is set to a high pressure so as to ensure a high vehicle height that is higher than the target vehicle height. It is set so as to allow the flow from the cylinder device to the accumulator, and when the vehicle height decreases, the one-way valve is switched and selected, and the pressure fluctuation in the cylinder device due to the expansion and contraction of the cylinder device during traveling causes The hydraulic fluid is discharged from the cylinder device to the accumulator at the timing when the pressure in the cylinder device becomes high, and when the vehicle height rises, the switching type connection circuit is switched from the one valve switching selection state at the time of vehicle height reduction. Is switched, and based on the differential pressure of the average pressure between the accumulator and the cylinder device,
A state in which hydraulic fluid flows from the accumulator to the cylinder device, and when the vehicle height is maintained, the switching connection circuit is switched to a state in which the cylinder device and the accumulator are shut off. Characteristic vehicle height adjustment device. 8. A cylinder device provided between a sprung weight and an unsprung weight, and an accumulator connected to the cylinder device via a switching connection circuit having a one-way valve. A method for injecting hydraulic fluid into a vehicle height adjusting device, comprising: establishing a communication state in which the cylinder device side and the accumulator side are forcibly communicated with the one valve as a boundary, wherein the cylinder device side and the accumulator side are connected to each other. A method of injecting a working fluid into the vehicle height adjusting device, wherein the working fluid is injected from the other side after evacuation from one of the sides.