JPH07223420A - Vehicle height controller - Google Patents

Abstract

PURPOSE:To quickly relieve a vehicle buried under snow. CONSTITUTION:When a vehicle is stuck in a road shoulder where snow remains laying and a driver operates an escape operation switch, oil is discharged from an actuator suspending the vehicle so that the vehicle height is lowered by H from the present height (step S100). In this way, the vehicle height is gradually lowered by H step by step, and snow existing beneath the vehicle lower face without any clearance is gradually compressed. This drop of the vehicle by H is repeated until the average height H4W of the vehicle is lowered below the escape lower limit vehicle height H0 which is lower than the height HNORMAL in normal travel. After the snow beneath the vehicle lower face is compressed in this way, oil is supplied to the actuator, so that the vehicle height is raised to the vehicle hight Hup higher than the height HNORMAL (step S150). In this way, an enough clearance is secured between the vehicle lower face and the compressed snow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle height control device for adjusting a vehicle height via a fluid pressure actuator for suspending a vehicle.

[0002]

2. Description of the Related Art This type of vehicle height control device has the following advantages because the vehicle height can be adjusted by supplying and discharging a working fluid to and from a fluid pressure actuator. For example, the vehicle height can be constantly maintained by adjusting the vehicle height according to changes in the number of passengers, the load capacity, or the unevenness of the road surface, or the vehicle height can be lowered during high-speed traveling to improve stability. In addition, a vehicle height control device equipped with a vehicle height high switch and a vehicle height low switch has also been put into practical use, and by operating these switches, the vehicle height can be kept high according to the preference of the vehicle driver. It can also be maintained or kept low.

[0003]

However, in the conventional vehicle height control device, the following problems remain unsolved.

When traveling on a snowy road, the vehicle may enter the road shoulder, a parking zone, or the like from the traveling road due to an unexpected cause. For example, in order to avoid a collision with an oncoming vehicle that runs off the center line, the vehicle may be forced to enter a road shoulder, a parking zone, or the like.

Generally, the snowfall on the road is compacted by a passing vehicle, but the snow on the road shoulders or the like is often left as it is, or the removed snow is accumulated. Therefore, when a vehicle enters such a road shoulder or the like, the vehicle is buried in the snow, and the snow exists between the lower surface of the vehicle and the ground without any gap. On the other hand, the lower surface of the vehicle is not a uniform surface, although it is partially covered by a steel plate,
There are irregularities. For this reason, the snow on the lower surface of the vehicle may come into contact with the vehicle and cause resistance, and the vehicle may not be able to escape from the road shoulder or the like.

In such a case, the vehicle height can be increased by operating the vehicle height high switch, but it may not be possible to escape from the road shoulder or the like for the reason described below.
Even if the vehicle height is increased, the amount of vehicle height adjustment is limited due to the mechanical structure of the fluid pressure actuator and the like, and the vehicle is separated from the snow only by increasing the vehicle height. Therefore, even if the vehicle height is increased, the gap between the lower surface of the vehicle and the snow may be insufficient and the vehicle may not escape.

The present invention has been made to solve the above problems, and an object thereof is to promptly escape a vehicle buried in snow.

[0008]

In order to achieve such an object, the means adopted by the invention as defined in claim 1 is interposed between a vehicle and a wheel to suspend the vehicle and supply and discharge the working fluid. A vehicle height control device having a fluid pressure actuator for adjusting the vehicle height of the vehicle according to the above, and a control means for driving and controlling a control valve for supplying and discharging a working fluid of the fluid pressure actuator according to a predetermined control command. There is provided an escape operation command generating means for issuing an escape operation command as the predetermined control command, and the control means is configured to discharge the working fluid from the fluid pressure actuator when the escape operation command is issued. An escape operation primary control unit that drives and controls the control valve, and drive control of the control valve so that the working fluid is supplied to the fluid pressure actuator after the control of the escape operation primary control unit is completed. To have an operation time of the secondary control unit out to its gist the.

In this case, in the vehicle height control device according to the present invention, pressure detecting means for detecting the pressure of the working fluid in the fluid pressure actuator is provided, and the primary controller during the escape operation is operated from the fluid pressure actuator. Of the working fluid is carried out stepwise, and when the state of the pressure change of the working fluid detected by the pressure detecting means is different from the pressure change based on the vehicle height change due to the discharge of the working fluid, the discharge of the working fluid is terminated. I decided.

[0010]

According to the vehicle height control apparatus of the present invention having the above-mentioned structure, when the escape operation command is issued from the escape operation command generating means, the control means sets this command as a predetermined control command and the control valve according to this command. Are controlled as follows.

First, during the escape operation of the control means, the primary control section drives and controls the control valve so that the working fluid is discharged from the fluid pressure actuator. Therefore, the vehicle height is adjusted to be low and the vehicle descends. Therefore, even if snow is present on the lower surface of the vehicle without any gaps, the snow is compressed by the vehicle. After that, during the escape operation of the control means, the secondary control unit drives and controls the control valve so that the working fluid is supplied to the fluid pressure actuator, so that the vehicle height is adjusted to be high and the vehicle rises.
Therefore, since the vehicle rises following the compression of the snow, a sufficient gap is secured between the underside of the vehicle and the snow.

In the vehicle height control device according to the second aspect, the working fluid is discharged stepwise from the fluid pressure actuator, so that the vehicle is lowered through the drive control of the control valve by the primary controller during the escape operation. Gradually. Further, if the state of the pressure change of the working fluid in the fluid pressure actuator detected by the pressure detecting means is different from the vehicle height change due to the discharge of the working fluid, that is, the pressure change based on the vehicle descent, the working fluid by the primary control unit during the escape operation is used. End the discharge of. Therefore, the vehicle descends gradually in stages, so even if stones on the road surface are hidden in the snow, the underside of the vehicle will collide with these stones more rapidly than when the vehicle height is lowered at once. No interference or interference. On the other hand, when the underside of the vehicle interferes with a stone in the snow in this way, the vehicle is supported by the underside of the stone and does not drop further. Therefore, the change in the working fluid pressure in the fluid pressure actuator is based on the vehicle descent. Unlike pressure changes, pressure drops. However, in the vehicle height control device according to the second aspect, when such a situation is reached, the discharge of the working fluid is ended and the descent of the vehicle is stopped. Therefore, the vehicle weight is applied to the portion of the vehicle lower surface that interferes with the stone or the like. It is possible to reliably avoid damage to the lower surface of the vehicle.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of a vehicle height control device according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a fluid circuit of a vehicle height control device 10 of an embodiment. As shown, the vehicle height control device 10 includes a reservoir 11 that stores oil as a working fluid, and one end of a connection passage 12 and one end of a working fluid discharge passage 14 are connected to the reservoir 11. The other end of the connection passage 12 is connected to the suction side of a pump 18 driven by the engine 16. The pump 18 is a variable displacement pump in the illustrated embodiment, and one end of a working fluid supply passage 20 is connected to the discharge side thereof. The other end of the working fluid supply passage 20 and the other end of the working fluid discharge passage 14 are connected to the pressure control valve 2
2 is connected to the P port and the R port of the pilot control type 3-port 3-position switching type switching control valve 24, respectively. In the middle of each working fluid discharge passage 14, the check valve 15 is located closer to the pressure control valve 22 than the communication connection portion 14a where the working fluid discharge passages for other wheels join.
Is provided. Therefore, in the working fluid discharge passage 14, the check valve 15 allows only the flow of the working fluid from the pressure control valve 22 to the reservoir 11.

The pressure control valve 22 includes a switching control valve 24, a branch passage 26 that branches from the working fluid supply passage 20 to reach the reservoir 11, and a fixed throttle 2 provided in the middle of the passage.
8 and a variable throttle 30 that changes the effective passage cross-sectional area of the branch passage 26 by a built-in solenoid. The variable throttle 30 of the pressure control valve 22 is connected to an electronic control unit 100, which will be described later, and when the electronic control unit 100 controls the current to the solenoid, it cooperates with the fixed throttle 28 and is variable with the fixed throttle 28. Branch passage 26 to the throttle 30
The internal pressure Pp is changed. A connection passage 32 leading to an actuator 36 that is interposed between the vehicle and the wheel and suspends the vehicle is connected to the A port of the switching control valve 24. The switching control valve 24 of the pressure control valve 22 is a spool valve that takes in the pressure Pp as a pilot pressure through the fixed throttle 28 and the variable throttle 30 and the pressure Pa in the connection passage 32 through the throttle 34 of the passage. Yes, pressure Pp and pressure P
The direction of the oil flow is switched according to the balance with a, and the oil is supplied to and discharged from the actuator 36.

The other end of the connection passage 32 is connected to a working fluid chamber 38 of an actuator 36 provided corresponding to the wheel. As shown in the figure, the actuator 36 is a kind of cylinder piston device and is arranged between the suspension member supporting the wheels W and the vehicle body to suspend the vehicle, and the working fluid is supplied to and discharged from the working fluid chamber 38. As a result, the vehicle height of the corresponding portion is increased or decreased as follows.

Normally, if the vehicle is stationary and in a horizontal position, the electronic control unit 100 allows the variable throttle 30 to take the switching position 24b at which the switching control valve 24 blocks the communication of all ports regardless of the vehicle height. Controls the solenoid.
As described above, the pressure Pa in the connection passage 32 and the pressure Pp in the branch passage 26, which are the pressures in the working fluid chamber 38 when the vehicle is stationary and in the horizontal state, are set as the reference pressure P0.

When the vehicle height is set to a lower vehicle height (HLOW) than HNOMAL while maintaining a certain vehicle height, for example, the vehicle height during normal traveling (HNOMAL) and being in a horizontal state. In addition, the pressure Pp in the branch passage 26 is set to the reference pressure P by a pressure corresponding to the deviation between the target vehicle height HLOW and the actual vehicle height HNOMAL.
The variable diaphragm 30 is controlled so as to descend from zero. Then, the pressure Pa in the connection passage 32 becomes higher than the pressure due to the pressure drop of the pressure Pp, so that the switching control valve 24 switches to the switching position 24c for connecting the ports R and A to each other. Therefore, oil is discharged from the working fluid chamber 38 of the actuator 36, and the vehicle lowers from HNOMAL by the actuator 36. As the vehicle height decreases in this way, the deviation between the target vehicle height HLOW and the actual vehicle height after the decrease decreases, so that the pressure drop amount of the pressure Pp corresponding to the deviation decreases, that is, the pressure Pp. Is the reference pressure P
The variable diaphragm 30 is controlled so as to approach zero. When the actual vehicle height matches the target vehicle height HLOW, the pressure drop amount of the pressure Pp becomes 0, the pressure Pp returns to the reference pressure P0, the switching control valve 24 takes the switching position 24b, and the oil discharge thereafter is stopped. To be done.

On the other hand, when the vehicle height is increased, the target vehicle height (for example, vehicle height HHIGH
> HNOMAL) and a pressure P that corresponds to the difference between the actual vehicle height
By increasing the pressure p from the reference pressure P0, the switching control valve 24 is switched to the switching position 24a where the port P and the port A are connected for communication. Then, oil is supplied from the pump 18 to the working fluid chamber 38 to increase the vehicle height, and when the actual vehicle height matches the target vehicle height, the pressure Pp is returned to the reference pressure P0 and the switching control valve 24.
Is set as the switching position 24b, and the oil supply thereafter is stopped. Whether the vehicle height is set to HLOW or HHIGH is set by the driver using a vehicle height setting switch 128 (see FIG. 2) provided separately.

A gas-liquid spring device 42 is connected to the working fluid chamber 38 by a passage 40, and a throttle 44 is provided in the passage 40. The gas-liquid spring device 42 acts as a suspension spring or an auxiliary suspension spring, and the throttle 44 generates a damping force. Further, the actuator 36 is provided with a pressure sensor 37 that detects the oil pressure in the working fluid chamber 38. In addition, a vehicle height sensor 118 that detects the vehicle height of the vehicle is provided between the suspension member that supports the wheels W and the vehicle body.

Further, in the middle of the working fluid supply passage 20,
A check valve 58 is provided which allows only the flow of the working fluid from the filter 56 and the pump 18 toward the pressure control valve 22. Further, the working fluid supply passage 2 on the downstream side of the check valve 58
An accumulator 60 is connected to 0.

The pressure control valve 22, the connection passage 32,
The diaphragm 44, the actuator 36, the pressure sensor 37, the gas-liquid spring device 42, etc. are provided corresponding to each wheel. In addition, these constituent members of each wheel (right front wheel, left front wheel, right rear wheel, and left rear wheel) are respectively denoted by FR, FL, RR, RL.
Is added, for example, the pressure control valve 22 is 22F
It will be referred to as R, 2FL, 22RR, and 22RL.

Next, the electrical construction of the vehicle height control device 10 will be described. As shown in FIG. 2, the pressure control valve 22F
Each of R to 22RL is connected to the electronic control unit 100, and the variable throttle 30 included in each pressure control valve is controlled by the electronic control unit 100. Electronic control device 100
Includes a microcomputer 102 mainly composed of a central processing unit (CPU) 104. As is well known, the microcomputer 102 has a CPU 104.
, Read-on memory (ROM) 106, random access memory (RAM) 108, and input port device 11
0 and an output port device 112, which are connected to each other by a bidirectional common bus 114.

The input port device 110 includes an ignition switch (IGS) as various switches and sensors.
W) 116 and vehicle height sensors 118FL and 118F for each wheel
R, 118RL, 118RR and pressure sensor 37 for each wheel
FL, 37FR, 37RL, 37RR, a vehicle speed sensor 120 for detecting the vehicle speed, a vehicle height setting switch 128 for setting the above-mentioned vehicle height mode, and an escape for promptly escaping the vehicle from the snow when the vehicle is buried in the snow An escape operation switch 129 for instructing the start of operation is connected. Then, the electronic control unit 100 receives various signals from these switches and sensors, specifically, a signal indicating whether or not the ignition switch is in an ON state, each wheel (left front wheel, right front wheel, left rear wheel, and right wheel). Vehicle height Xi of the part corresponding to the rear wheel)
(I = FL, FR, RL, RR), a signal indicating the oil pressure Pi (i = FL, FR, RL, RR) in the working fluid chamber 38 of the actuator 36 of each wheel, and a signal indicating the vehicle speed V , A signal indicating whether the vehicle height control mode is the high mode or the low mode, and a command signal for starting the escape operation are input.

The input port device 110 appropriately processes the above-mentioned input signals, and in accordance with the instruction of the CPU 104 based on the program stored in the ROM 106, the CPU and the R
The processed signal is output to the AM 108. The ROM 106 stores various data in addition to the control flow shown in FIG. 3 and other control flows not shown, and the CPU is adapted to process signals based on each control flow. The output port device 112 is a CP
According to an instruction from U104, a control signal is output to the variable throttles 30 of the pressure control valves 22FR to 22RL via the drive circuits 132 to 138.

Next, the escape operation control (routine) performed by the electronic control unit 100 of the vehicle height control system 10 of this embodiment will be described with reference to the flowchart of FIG. In the escape operation routine shown in the figure, when the escape operation switch 129 is operated by the driver, the ON signal of the switch is interrupted as a start instruction signal for the escape operation.
Further, the escape operation switch 129 is operated in order to escape the vehicle from this state when the vehicle is buried in the snow when the vehicle enters the road shoulder or the like where the snow that has been left snowfall or the snow that has been removed is accumulated. It

When the escape operation routine is started by turning on the escape operation switch 129, the electronic control unit 100 first sets the target vehicle height to a vehicle height that is lower than the current vehicle height by ΔH (step). S100). As a result, the variable throttle 30 is controlled to reduce the pressure Pp in the branch passage 26 according to the deviation ΔH as described above, and after the switching control valve 24 is switched to the switching position 24c,
The vehicle descends by ΔH from the current vehicle height. In other words, the vehicle descends only by ΔH, and the snow that exists without gaps on the underside of the vehicle is
Compressed by ΔH by the descending vehicle.

Next, the vehicle height Xi (i = FL, FR, RL, RR) for each wheel is read from the vehicle height sensor 118 for each wheel (step S110), and the vehicle obtained from the read vehicle height for each wheel is read. It is determined whether the average vehicle height H4W of the vehicle has fallen below a predetermined escape lower limit vehicle height H0 (step S1).
20). This escape lower limit vehicle height H0 is a vehicle height that is defined as being able to sufficiently compress snow if the vehicle descends to this vehicle height, and is set lower than the vehicle height HNOMAL during normal traveling.

If a negative decision is made in step S120,
Even if the vehicle height is lowered from the current vehicle height by ΔH in step S100, the average vehicle height H4W of the vehicle is not below the escape lower limit vehicle height H0, and the vehicle descent is insufficient. On the other hand, if an affirmative decision is made in step S120, it means that the vehicle height has been made sufficiently low so that the average vehicle height H4W of the vehicle falls below the escape lower limit vehicle height H0. Therefore, when a negative determination is made in step S120, the vehicle height is further reduced in step S1.
Processing after 30 is performed.

Following the negative determination at step S120,
From the pressure sensor 37 of each wheel to the oil pressure Pi (i in the working fluid chamber 38 of the actuator 36 for each wheel
= FL, FR, RL, RR) is read (step S1)
30). Then, it is determined whether or not the read oil pressure Pi (i = FL, FR, RL, RR) of each wheel is equal to or lower than a predetermined lower limit pressure value PLOW (step S140). The lower limit pressure value PLOW is determined as follows. When the vehicle descends, if the lower surface of the vehicle interferes with the road surface itself hidden by snow or stones on the road surface, the vehicle is supported by this stone and does not descend further. The oil pressure in 38 drops. Therefore, the lower limit pressure value PLOW is defined as the lower limit value of the oil pressure that is lowered when the vehicle lower surface interferes with a stone or the like.

That is, in this step S140, prior to the further vehicle descent following the negative determination in step S120, it is determined whether or not the lower surface of the vehicle interferes with the road surface itself hidden by snow or stones on the road surface. And step S
If a negative determination is made at 140, there is no interference between the lower surface of the vehicle and the road surface, so that the vehicle descent should be continued in step S10.
Move to 0 and further lower the vehicle height by ΔH. For this reason,
Until the affirmative judgment is made in step S120 or the positive judgment is made in step S140, the vehicle height is gradually decreased by ΔH.

On the other hand, if the affirmative determination is made in step S120, the vehicle is sufficiently lowered, and if the affirmative determination is made in step S140, the lower surface of the vehicle and the road surface or the like interfere with each other.
It can be said that further vehicle descent is unnecessary. Therefore, if either of these determinations is made, the target vehicle height is set to a vehicle height Hup higher than the vehicle height HNOMAL during normal traveling by a predetermined amount (step S150). As a result, the variable diaphragm 30
As described above, the switching control valve 24 is controlled to increase the pressure Pp in the branch passage 26 in accordance with the deviation between the vehicle height that has already been lowered (escape lower limit vehicle height H0) and the target vehicle height Hup by the above processing. The oil is supplied from the pump 18 to the working fluid chamber 38 of the actuator 36 through the switching to the switching position 24a. Therefore, the vehicle height is Hup.
Until (> HNOMAL), the vehicle rises from the escape lower limit vehicle height H0 or the vehicle height when the vehicle bottom surface interferes with the road surface, etc., and a sufficient gap is secured between the vehicle bottom surface and the already compressed snow. It

Subsequent to step S150, it is determined whether or not the escape operation switch 129 has been turned off (step S160). If an affirmative decision is made here, further evacuation operation control is unnecessary according to the judgment of the driver, so this routine is once terminated, and the ON operation of the evacuation operation switch 129 from the next time is awaited. On the other hand, when a negative determination is made in step S160, the vehicle speed V is read from the vehicle speed sensor 120 (step S170), and it is determined whether or not the read vehicle speed V is equal to or higher than a predetermined vehicle speed V0 (for example, 10 km / h). (Step S180). If the determination is negative, the process proceeds to step S160, and if the determination is positive,
Since the vehicle has traveled at a speed equal to or higher than the predetermined vehicle speed V0, this routine is once ended, and the escape operation switch 129 for the next and subsequent times is ended.
Wait for the ON operation of. That is, steps S170 and 180
Then, by the processing up to step S160, it is determined from the transition of the vehicle speed V whether or not the vehicle has escaped from a road shoulder or the like where there is still snow left. When this routine is finished, a normal vehicle height control (not shown) such as whether the vehicle height is set to HLOW or HHIGH according to the operation of the vehicle height setting switch 128 is executed.

As described above, in the vehicle height control device 10 of the present embodiment, if the vehicle enters a road shoulder or the like where there is still snow left, the vehicle height is once lowered to compress the snow on the lower surface of the vehicle. After that, the vehicle is raised until the vehicle height becomes a vehicle height Hup higher than the vehicle height HNOMAL during the normal running. Therefore, according to the vehicle height control device 10 of the present embodiment, a sufficient gap can be reliably ensured between the lower surface of the vehicle and the snow, so that the vehicle buried in the snow can quickly escape.

Further, in the vehicle height control device 10 of this embodiment,
When lowering the vehicle during the escape operation, the vehicle is gradually lowered by ΔH. Therefore, according to the vehicle height control device 10 of the present embodiment, the vehicle lower surface, the road surface, etc. are lowered by only lowering the vehicle by ΔH stepwise as compared with the case where the vehicle is lowered by a predetermined amount at one time. The impact at the time of interference with the vehicle can be mitigated, and damage to the lower surface of the vehicle can be suppressed.

Further, in the vehicle height control device 10 of this embodiment,
While lowering the vehicle, the oil pressure Pi (i = FL, F in the working fluid chamber 38 in the actuator 36 of each wheel is
R, RL, RR). When any of the oil pressures Pi becomes lower than or equal to the lower limit pressure value PLOW, the lower surface of the oil interferes with the road surface itself hidden by snow or stones on the road surface as the vehicle descends, and the vehicle supports the stones on the lower surface. Since the vehicle is driven and does not descend further, further vehicle descent by the actuators 36 of the respective wheels is stopped. Therefore, according to the vehicle height control device 10 of the present embodiment, it is possible to reliably avoid damage to the lower surface of the vehicle due to stones hidden in the snow.

Further, a simple modification such as addition of an escape operation switch 129 or escape operation control is performed on a conventional vehicle height control device for setting the vehicle height to HLOW or HHIGH according to the operation of the vehicle height setting switch 128. Just because
It is possible to effectively use the existing device.

Although one embodiment of the present invention has been described above, the present invention is not limited to such an embodiment, and can be implemented in various modes without departing from the scope of the present invention. Of course.

For example, although the escape operation control start command is generated by the escape operation switch 129 that is manually operated, it may be performed as follows. A vehicle detection means for detecting that a vehicle has entered the road shoulder or the like where there is still snow left is formed by a reflection type optical sensor or temperature sensor provided on the bottom surface of the vehicle, and is provided from this vehicle detection means. It is also possible to start the escape operation control by the signal of. Alternatively, the switching control valve 24 of the pressure control valve 22 may be switched by a solenoid provided on the switching position 24a side and the switching position 24c side. In this case, the supply and discharge of oil to and from the actuator 36 may be performed by switching the energization by both solenoids. In addition, although the actuator 36 is configured to use oil as the working fluid, it is needless to say that the actuator 36 may be configured to use liquids other than oil or various gases as the working fluid.

Further, when the lower surface of the vehicle interferes with the road surface itself hidden by snow or stones on the road surface when the vehicle descends,
Upon ending the oil discharge and stopping the descent of the vehicle thereafter, in the present embodiment, the oil discharge is terminated when the oil pressure of any one of the wheels falls below a predetermined value (lower limit pressure value PLOW). did. However, when the rate of decrease of the oil pressure of any of the wheels becomes equal to or higher than a predetermined value, it is possible to finish the discharge of oil and stop the subsequent descending of the vehicle.

Further, although the vehicle height sensor 118 is used as the vehicle height detecting means for detecting the vehicle height in this embodiment, the vehicle height detecting means can be constructed without using the vehicle height sensor. Specifically, as shown in FIG. 4, the actuator 3
6 and the coil spring 39 may be used in parallel, and the vehicle height may be detected based on the pressure change in the actuator 36. In this case, since the vehicle height and the pressure can be associated with each other, the control of the variable throttle 30 is changed as described below, and the escape operation routine (FIG. 3) in the above embodiment is shown in FIG. It can be transformed as follows.

First, the vehicle height is the height during normal traveling (HNOMAL
), The variable throttle 30 is controlled so that the pressure Pp in the branch passage 26 becomes a predetermined pressure Pp0. This time,
If the pressure Pa in the connection passage 32 is equal to the pressure Pp, the switching control valve 24 takes the switching position 24b that shuts off the communication of all ports, and the vehicle height is maintained at HNOMAL.

However, the pressure Pp is the above-mentioned predetermined pressure Pp0.
If the variable throttle 30 is controlled to be lower, the pressure Pa
Is higher than the pressure Pp, the switching control valve 24 is switched to the switching position 24c that connects the port R and the port A to each other, and keeps this position until the pressure Pa and the pressure Pp become equal. Therefore, the working fluid chamber 38 of the actuator 36
Oil is discharged from the vehicle, and the vehicle height becomes lower than HNOMAL (HLOW) by the actuator 36. On the other hand, the variable throttle 30 is adjusted so that the pressure Pp becomes higher than the predetermined pressure Pp0.
Is controlled, the pressure Pa becomes lower than the pressure Pp. Therefore, the switching control valve 24 switches to the switching position 24a that connects the port P and the port A to each other, and the pressure Pa and the pressure Pp are switched.
Take this position until are equal. Therefore, oil is supplied from the pump 18 to the working fluid chamber 38 of the actuator 36, and the vehicle height is HNOMAL by the actuator 36.
It becomes a higher height (H HIGH).

Then, in order to escape the vehicle in the snow, as shown in FIG. 5, first, instead of step S100, the variable throttle 30 of the pressure control valve 22 is controlled so that the pressure P
p is made lower than the current pressure (Pa) by ΔP (step S1000). As a result, the switching control valve 24 is switched to the switching position 24c, and the pressure Pa in the connection passage 32 is ΔP.
Until the working fluid chamber 3 of the actuator 36
Oil is discharged from No. 8, and the vehicle height is lowered from the current vehicle height by the amount corresponding to this ΔP (ΔH). That is, the vehicle descends by ΔH, and the snow present on the lower surface of the vehicle without a gap is compressed by ΔH by the descending vehicle.

Following step S1000, steps S110, 120, and 130 of the above embodiment are performed.
Judgment of excess or deficiency of vehicle descent, stepwise descent of vehicle, etc. are performed.
Then, following step S130, the above step S
Instead of 140, it is determined whether or not any one of the step-down displacement ΔPOIL of each wheel obtained from the oil pressure of each wheel is equal to or lower than a predetermined step-down displacement lower limit value P0 (step S1).
400). This step-down displacement lower limit value P0 is the lower limit pressure value PLO.
Similar to W, it is specified as the lower limit value of the oil pressure that is lowered when the vehicle bottom surface interferes with stones.

After that, instead of step S150, the variable throttle 30 of the pressure control valve 22 is controlled to control the pressure Pp.
Is made higher than the predetermined pressure Pp0 by ΔPup (step S1500). As a result, the switching control valve 24 is switched to the switching position 2
4a, and oil is supplied from the pump 18 to the working fluid chamber 38 of the actuator 36 until the pressure Pa in the connection passage 32 becomes equal to this pressure Pp (Pp0 + ΔPup). Therefore, in the vehicle, the vehicle height is the predetermined pressure P.
From the vehicle height HNOMAL during normal driving corresponding to p0, this ΔP
Until the vehicle height Hup corresponding to up is reached, the vehicle rises from the escape lower limit vehicle height H0 or from the vehicle height when the vehicle bottom surface interferes with the road surface, etc., and between the vehicle bottom surface and already compressed snow. A sufficient gap is secured. This step S1500
Then, as in the above embodiment, steps S160, 1
70 and 180 are executed.

[0046]

As described in detail above, in the vehicle height control device according to the first aspect of the present invention, if the vehicle enters a road shoulder or the like where there is still snow left, the vehicle height is once lowered and the vehicle is lowered. Then, the snow on the lower surface of the vehicle is compressed, and then the vehicle height is increased to raise the vehicle. As a result, according to the vehicle height control device of claim 1, a sufficient gap can be secured between the lower surface of the vehicle and the snow by raising the vehicle following the compression of the snow, and the vehicle buried in the snow can be swiftly removed. Can be escaped to.

In the vehicle height control device according to the second aspect, when the vehicle is lowered in order to escape the vehicle buried in snow, the vehicle is gradually lowered in stages, and the fluid pressure actuator is operated during the vehicle descent. When the state of the pressure change of the working fluid is different from the vehicle height change due to the discharge of the working fluid, that is, the pressure change based on the vehicle descent, the discharge of the working fluid is ended and the vehicle descent thereafter is stopped. As a result,
According to the vehicle height control device of the second aspect, compared to the case where the vehicle is lowered by a predetermined amount at one time, not only the impact at the time of the interference between the vehicle lower surface and the road surface etc. can be alleviated, but also the vehicle lower surface interferes with the stone etc. Since the vehicle weight is not applied to the place, it is possible to reliably avoid damage to the lower surface of the vehicle.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a fluid circuit of a vehicle height control device 10 of an embodiment.

FIG. 2 is a block diagram showing an electrical configuration of a vehicle height control device 10.

FIG. 3 is a flowchart showing an escape operation routine performed by the vehicle height control device 10 of the present embodiment.

FIG. 4 is a schematic configuration diagram showing a main part of a fluid circuit of a modified example of the vehicle height control device 10.

FIG. 5 is a flowchart showing an escape operation routine performed by a vehicle height control device 10 of a modified example.

[Explanation of symbols]

 10 ... Vehicle height control device 12 ... Connection passage 14 ... Working fluid discharge passage 16 ... Engine 18 ... Pump 20 ... Working fluid supply passage 22 ... Pressure control valve 24 ... Switching control valve 24a ... Switching position 24b ... Switching position 24c ... Switching position 26 ... Branch passage 28 ... Fixed throttle 30 ... Variable throttle 32 ... Connection passage 34 ... Throttle 36 ... Actuator 37 ... Pressure sensor 38 ... Working fluid chamber 60 ... Accumulator 100 ... Electronic control device 102 ... Microcomputer 118 ... Vehicle height sensor 120 ... Vehicle speed sensor 128 ... Vehicle height setting switch 129 ... Escape operation switch

Claims (2)

[Claims] 1. A fluid pressure actuator interposed between a vehicle and a wheel to suspend the vehicle and adjust the vehicle height of the vehicle by supplying and discharging the working fluid, and a supply of the working fluid of the fluid pressure actuator. A vehicle height control device having a control means for driving and controlling a discharge control valve according to a predetermined control command, comprising an escape operation command generating means for issuing an escape operation command as the predetermined control command, The control means drives the control valve so that the working fluid is discharged from the fluid pressure actuator when the escape operation command is issued, and an escape operation primary control section, and an escape operation primary control section. And a secondary control section during escape operation for driving and controlling the control valve so that the working fluid is supplied to the fluid pressure actuator after completion of the control. 2. The vehicle height control device according to claim 1, further comprising a pressure detection unit that detects the pressure of the working fluid in the fluid pressure actuator, wherein the escape operation primary control unit is the fluid pressure actuator. The working fluid is discharged stepwise, and when the state of the pressure change of the working fluid detected by the pressure detecting means is different from the pressure change based on the vehicle height change due to the discharge of the working fluid, the discharge of the working fluid is terminated. A vehicle height control device that does.