JPH0379416A - Active suspension - Google Patents

Abstract

PURPOSE:To define the time for maintaining power as low as possible, and to prevent battery-up by sustaining the supply of one end power after an engine is stopped so as to continue car height control, and by releasing power supply when an opening/closing mechanism in a working fluid back-path is switched to a closed state. CONSTITUTION:In an active suspention, a working fluid from a fluid pressure supplier B supplied to each fluid pressure cylinder A individually placed between a car body and each wheel, is separately controlled by a control valve C based on a command value. A check valve is provided on a supply path between the fluid pressure supplier B and a control valve C, while a back-path opening/ closing mechanism E is provided on a back-path, which is closed when the supply pressure to the control valve C is lowered within set values. On a controller that gives a command value to the control valve C by a car height controller F, a power maintaining means G is provided so as to sustain power supply from a battery after an engine is stopped, whereby the means F is released by a power releasing means I when the change-over of the opening/closing mechanism E to a closed state is detected by a detecting means H.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an active suspension for a vehicle, and more particularly to an active suspension that improves the timing of turning off the power after the engine is stopped.

[Prior Art] This type of active suspension is described, for example, in Japanese Patent Application Laid-Open No. 1-122717 published by the present applicant.

One aspect of this active suspension includes a hydraulic cylinder arranged on each wheel, a hydraulic pressure supply device that supplies working pressure to the hydraulic cylinder, and the working pressure is controlled according to a command value from an attitude change suppression control device. It is equipped with a pressure control valve (proportional electromagnetic pressure reducing valve), and among the line pressure pipe and drain pipe that connect the pressure control valve and the hydraulic pressure supply device, a check valve is interposed in the line pressure pipe, and a check valve is installed in the drain pipe. A pilot operated check valve is installed. In addition, after the engine is stopped, power is supplied to the attitude change suppression control device for a predetermined period of time.
Command values can be output.

The pilot-operated check valve has a supply pressure P to the pressure control valve,
is the pilot pressure, and when the supply pressure P exceeds the set pressure, it becomes "open" and the return pressure becomes atmospheric pressure, allowing the cylinder pressure to be controlled by the pressure control valve.

Further, as shown in Fig. 7, when the engine is boiled and the oil pump is stopped, the supply pressure P gradually decreases to the set pressure PM (for example, the operating neutral pressure) after a period of to. The pilot-operated check valve becomes "closed" and cooperates with the check valve in the line pressure line to maintain the cylinder pressure at the set pressure PN (=supply pressure=control pressure=return pressure). During this time, when the command value becomes zero (that is, the cylinder pressure also becomes zero), the vehicle height value changes suddenly, but the attitude change suppression control device waits for a predetermined period of time even after the engine is stopped. outputs a command value corresponding to the neutral pressure P to the pressure control valve to control the cylinder pressure and prevent sudden changes in vehicle height.

In the above configuration, the time t0 when the supply pressure P3 becomes equal to the set pressure PM is equal to the pressure stored in the pressure accumulator on the supply side,
It is determined by the oil leakage (leakage) Wk after the engine is turned off. That is, the decreasing curve of the supply pressure P3 between t0 and t5 in FIG. , is the pressure that indicates the initial state of the oil stored in the accumulator.

The volume, Pt is the pressure changed due to leakage for L hours, and "■.・t" is the amount of oil leaked.

The main leakage of this oil is from gaps in the oil passage, such as the gap between the body insertion hole of the pressure control valve and the spool, and the amount of leakage is determined by the viscosity of the oil as shown in Figure 8. Varies depending on This viscosity further changes depending on the environment, that is, the temperature, as shown in Figure 9. Therefore, the time t and D for which the supply pressure P3 falls to the set pressure P, increases (varies) depending on the environmental temperature as shown in Figure 10. (9 hours in the same figure jD=Lsir
+ indicates 9 hours at high temperature L1) = L tip indicates 1 hour at medium temperature = t□8 indicates low temperature).

Until this time to elapses, the engine is off and power is supplied to the load from the battery, so
That time 1. Although it is desirable that the temperature be as short as possible, since vehicles are used in a wide variety of environments, it is necessary to cover a wide temperature range from low temperatures (-30°C or lower) to high temperatures (60°C or higher).

Therefore, the power supply maintenance time was set so that the power supply to the attitude change suppression control device could be performed at least until the maximum time t, □ at the low temperature that can be assumed has elapsed.

[Problem to be solved by the invention]

However, with such an active suspension, after the engine is turned off until the maximum time t□8 elapses,
Because the configuration was configured to continuously supply power from the battery, for example, when the environmental temperature is high, the viscosity of the oil is relatively low.
Before a certain period of time t, □ elapses after the engine is turned off, the supply pressure P3 drops to the set pressure PM and seals the cylinder pressure, so after this sealing, power is wasted and the battery may run out. There was an unresolved issue of growing sex. In particular, in situations where the vehicle is repeatedly driven for short periods of time, the battery may not be sufficiently charged, and in such a case, there is a greater possibility that the battery will run out. To prevent this, it is possible to install a device with a larger capacity, but this would increase cost and weight, so this preventive measure was not appropriate.

This invention was made by focusing on the above-mentioned unresolved problem, and when the supply pressure P drops to the set pressure PN, the oil on the load side is sealed to maintain the cylinder internal pressure. The problem to be solved is to stop the power supply from the battery at a certain point in time, thereby eliminating wasteful consumption of battery power and preventing the battery from running out.

[Means to solve the problem]

In order to solve the above problems, in each invention of this application, the first
As shown in the figure, a fluid pressure cylinder interposed between the vehicle body and the wheels, a control valve that controls the working fluid from the fluid pressure supply device supplied to the fluid pressure cylinder according to a command value, and A fluid pressure supply device, a check valve inserted in a supply path between 1 and the control valve, and a check valve inserted in a return path between the fluid pressure supply device and the control valve to set the supply pressure to the control valve. In the active suspension including a return path opening/closing mechanism that closes when the return path decreases to a specified value, and a control device that provides a command value to the control valve, the control device at least maintains power supply from the vehicle battery even after the engine is stopped. a vehicle height control means for supplying a command value to the control valve to control the vehicle height value even after the engine is stopped while the power supply maintenance means maintains the power supply; closing operation detection means for detecting switching from an open state to a closed state; and a power source for canceling the power supply maintenance state of the power supply maintenance means when the closing operation detection means detects switching to the closed state. The main part is that it has a release means.

[Effect]

The main functions of each invention of this application are as follows. When the engine stops, the power supply maintenance means maintains the power supply from the vehicle battery to the control jB device. During this maintenance, the vehicle height control means outputs a command value to the control valve to prevent sudden changes in the vehicle height. , which controls the cylinder pressure. On the other hand, when the engine stops, the fluid discharged from the fluid pressure supply device disappears, so the supply pressure to the control valve decreases, and the high pressure fluid remaining in the fluid path and accumulator gradually flows through the return path opening/closing mechanism. Return to pressure supply device. Therefore, when the supply pressure to the control valve gradually decreases and reaches a preset pressure value, the return path opening/closing mechanism switches from the open state to the closed state. As a result, the working fluid on the load side including the control valve and the fluid pressure cylinder is contained by the check valve and the return passage opening/closing mechanism, and the cylinder internal pressure is maintained at a set value.

At this time, the closing operation detecting means detects the switching of the return path opening/closing mechanism to the closed state, and energizes the power release means.

Therefore, the power release means forcibly releases the power supply state of the power supply maintenance means. In other words, even if the time it takes for the supply pressure to the control valve to drop to the set value after the engine is stopped varies depending on the environmental temperature, etc., the power is turned off when the supply pressure reaches the set value. In other words, the power release timing can be optimized, and unnecessary consumption of battery power can be prevented.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 2 to 6.

In FIG. 2, 10FL to 10RR indicate front right to rear right wheels, 12 indicates a wheel side member connected to each wheel 10FL to 10RR, and 14 indicates a vehicle body side member.

A hydraulic active suspension 16 is provided between each wheel side member 12 and the vehicle body side member 14.

The active suspension 16 includes a hydraulic pressure supply device 18 as a fluid pressure supply device, a working pressure holding means 20 interposed on the load side of the hydraulic pressure supply device 18, and a front side on the load side of the working pressure holding means 20. Accumulators 24, 24 equipped corresponding to the rear wheel side, and the accumulators 24, 24
The vehicle is provided with pressure control valves 26FL to 26RR and hydraulic cylinders (fluid pressure cylinders) 28FL to 28RR, which are provided on the load side of the vehicle and are provided corresponding to the wheels 10FL to 10RR, respectively. The active suspension 16 also uses an acceleration detector 30, vehicle height detectors 31FL to 31RR, and a pressure switch 32, and applies a command current I to the pressure control valves 26FL to 26RR based on the detection signals of the respective detectors 30 to 32.

. . , and a control device 33 that provides . Further, a coil spring 39 is provided between the wheel side member 12 and the vehicle body side member 14, which has a relatively low spring constant and supports the static load of the vehicle body.

The hydraulic supply device 1 includes a reservoir tank 40 for storing hydraulic oil, and a hydraulic pump 4 whose rotational drive source is an engine.
2 and a relief valve 44 for setting a predetermined line pressure. A line pressure pipe 48s for supplying hydraulic oil and a drain pipe 48r for returning hydraulic oil are connected to the tank 40, and the line pressure pipe 48s leads to the next stage working pressure holding means 20 via a hydraulic pump 42. Pipeline 48S
.

A relief valve 44 is connected to a position on the discharge side between 48r and 48r.

The operating pressure holding means 20 is operated by a check valve (check valve) 50 inserted into the line pressure pipe 48s and a pilot operation which sets the downstream line pressure of the check valve 50 inserted into the drain pipe 48r as a pilot pressure P. It has an operating check valve (return passage opening/closing mechanism) 52 of the form.

As shown in FIG. 3, the operable check valve 52 has a cylindrical valve housing 52A. This valve housing 5
An insertion hole 52Aa is bored inside the 2A, and an input boat 52i, an output boat 52o, and a conduit 48s are connected to the conduit 48r in communication with the insertion hole 52Aa.
A pilot boat 52p connected to the poppet 52B is provided, and a poppet 52B and a spool 52C opposing the poppet 52B are both slidably disposed in the insertion hole 52Aa. The poppet 52B is biased by a coil spring 52E in a direction in which it comes into contact with a valve seat 52D formed between the input port 52i and the output boat 52o, and the spool 52B
Pilot boat 5 is on the opposite side of poppet 52B of 2C.
A pilot pressure P from 2p is given. Here, the relief pressure of the poppet 52B is PPI (in this embodiment, the same as the operating neutral pressure Ps of the pressure control valves 26FL to 26RR) is PPI, the effective area of the spool 52C is A, the spring constant of the coil spring 52E is k, and the poppet When the amount of displacement is X, the preset pressure F of the coil spring 52E is
0 is represented by the following formula (1).

F o = P p + - A -- (1) Now, the relationship between pilot pressure P and input pressure P is P, ≧
In the case of P, the spool 52C is separate from the poppet 52B, and no force is transmitted to the poppet 52B.
2B only functions as a relief valve. That is, the pressure P of the input port 52i.

Pl ・A=P, ・Equilibrium under the condition of A, P
If i > P□, it is open in relief state, and P! ≦P
, it is in a closed state.

On the other hand, when Pi<P, the force (Pp Pi)A acting on the spool 52C pushes the poppet 52B, and the poppet 52B and the spool 52C move as if they were integrated. Therefore, generated by the input pressure Pi,
Since the forces acting on the poppet 52B and the spool 52C cancel out inwardly, the poppet 52B is balanced in the state expressed by equation (2) below.

-X-PP to FO+ A - Old
P r+) Since A> O, PP>PPI(”P
M), the check valve is open, and P, ≦PPI(-P
M), it is in the closed state.

On the load side of the working pressure holding means 2o, a line pressure pipe 4
8s has 10FL front wheel, 10FR1 rear wheel 10RL.

10RR, each pipe line 48s is connected to a large-capacity, high-pressure gas-filled accumulator 24, and further branched corresponding to the left and right wheels to connect pressure control valves 26FL to 26.
Leading to RR's supply boat. Furthermore, the operating check valve 52 and the return boats of the pressure control valves 26FL to 26RR are connected back and forth as shown in the figure.

The left and right sides are branched and connected, respectively.

In addition, each of the pressure control valves 26FL to 26RR has a valve housing with a built-in spool that is slidable in the insertion hole, and a feedback pressure that is applied to one end of the spool and a pilot pressure that is applied to the other end of the spool that can be adjusted. It is formed of a conventionally well-known three-point proportional electromagnetic pressure reducing valve (see, for example, the above-mentioned Japanese Patent Application Laid-open No. 1-122717) having a proportional solenoid. Of the three ports, the supply boat and return boat are connected to hydraulic piping 48s and 48r, and the output port is connected to hydraulic piping 6.
0 to the pressure chambers of the hydraulic cylinders 28FL to 28RR. By adjusting the command current I (command value) supplied to the proportional solenoid, the spool position is controlled, and the control pressure P output from the output port is controlled.
can be controlled.

Here, the relationship between the command current 1 (IFL-IRI) and the control pressure P is as shown in FIG. When the command current ■ is zero, the control pressure P is also zero, and when the command current I increases from this state, the control pressure P increases in proportion to this, and the maximum command value 1. When , the maximum control pressure P corresponds to the set line pressure.

Furthermore, each of the hydraulic cylinders 28FL to 28R11 has a cylinder tube 28a, as shown in FIG. 2, and a lower pressure chamber is formed in the cylinder tube 28a, which is separated by a piston 28c. The lower end of the cylinder tube 28a is attached to the wheel side member 12, and the upper end of the piston rod 28b is attached to the vehicle body side member 14. In addition, each hydraulic cylinder 28FL~
The pressure chamber of 28RR is for absorbing hydraulic vibration in the unsprung resonance region (for example, 5 to lO&) via the throttle valve 62.
It is connected to a small capacity accumulator 63.

On the other hand, the acceleration detector 30 is installed at a predetermined position on the vehicle body, detects accelerations of the vehicle body in the lateral, longitudinal, and vertical directions, and sends an acceleration signal G of positive and negative analog voltage values corresponding to these accelerations to the control device 33. It is designed to output to . In addition, the vehicle height detectors 31FL to 31RR are comprised of potentiometers attached to the hydraulic cylinders 28FL to 28RR at the front to rear right wheel 10FL to 10RR (7) positions, and are configured to adjust the height of the vehicle according to the stroke amount of the sprung and unsprung parts. A vehicle height signal HFL-H□ having an analog voltage value is supplied to the control device 33. Further, in this embodiment, the pressure switch 32 includes an operating check valve 52 and pressure control valves 26FL to 26R.
The flow path pressure of the drain pipe 48r between R is detected, and a switch signal SS that is turned on when this pressure reaches a set pressure PM (operating neutral pressure) is output to the control device 33. Note that the set pressure at which the switch signal SS is turned on may be set slightly lower than the operating neutral pressure PH to ensure that the on-state operation is performed when internal pressure is sealed, which will be described later.

The control device 33 includes a microcomputer 6 for arithmetic processing.
6, and on the input side of this microcomputer 66, the acceleration detection signal G and the vehicle height detection signal H, L-H□ are input to A/
A/D conversion 68° 70A to 70D for D conversion and pressure command value VFL on the output side of the microcomputer 66.
“D/A converter 72A~?2 that converts Veil into D/A
D and the outputs of the D/A converters 72A to 72D as target values, a current (command current) according to the target value I FL
-r** to the pressure control valves 26FL to 26RR, respectively. The microcomputer 66 includes an interface circuit 76, an arithmetic processing unit 78. It has a storage device 80,
When activated, the arithmetic processing unit 78 performs arithmetic operations and control 'B (see FIG. 6), which will be described later, according to procedures stored in advance in the storage device 80.

Further, the control device 33 of this embodiment has a first switch for switching. Second transistor 82,83 and normally open contact 84A
and a relay 84 having an excitation coil 84B. Among them, the base of the first transistor 82 is connected to the positive side of the battery 88 via the ignition switch 86, the base of the second transistor 83 is connected to the interface circuit 76 of the microcomputer 66, and the transistor switching signal ST is The emitters of the supplied transistors 82 and 83 are both connected to ground, and the collectors are both connected to the battery 88 via the excitation coil 84B of the relay 84.

The normally open contact 84A is inserted in a path from the battery 88 to the power supply terminals of each part of the control device 33.

Further, the load side of the ibnirasilane switch 86 is also connected to the interface circuit 76, and the ignition switch signal IC is supplied to the microcomputer 66. Note that 90 is a charging device.

Next, the operation of this embodiment will be explained.

Now, when the ignition switch 86 is turned on, the first transistor 82 in the control device 33 becomes conductive.
Current flows from the battery 88 to the excitation coil 84B of the relay 84, and the coil 84B becomes excited. This results in
The contact 84A closes, power is supplied from the battery to each power supply terminal of the control device 33, and the control device 33 is activated. Energized by this activation, the arithmetic processing unit of the microcomputer 66 starts the processing shown in FIG.

The process shown in FIG. 6 will be explained. First, step ■ in the same figure.
Then, the arithmetic processing unit 78 calculates the vehicle height command value V for the front passenger to the rear right side.
Initialize by setting the neutral value ■8 to H, L to ■H1llI. This neutral value (8) is a command value that provides the target vehicle height H1 under the standard load.

Next, the process proceeds to step (2), where the arithmetic processing unit 78 reads the ignition switch signal IC via the interface circuit 76, checks whether the ignition switch 86 is on, and determines whether the engine is stopped. If this judgment is that the engine is operating, the process moves to step (3), and the arithmetic processing unit 78 instructs to turn on the transistor switching signal ST to a logic H level via the interface circuit 76. As a result, the second transistor 83 also becomes conductive.

Next, the process proceeds to step (2), where the arithmetic processing unit 78 reads the vehicle height detection signal HFL-H□ which has been converted into a digital quantity via the interface circuit 76, temporarily stores the value as the actual vehicle height value, and then proceeds to step (2). to move to.

In step (3), the arithmetic processing unit 78 calculates the actual vehicle high value HF.
It is determined whether L-H11, matches the target vehicle height value H, (specifically, it has a predetermined width), and if "NO", then step (r) HFL-HR11> Hs
J or not is determined. In this judgment, in the case of rYEsJ, the actual vehicle high value HFL""Hlll exceeds the target vehicle height value H3, so in step
, L-VHRR by a minute value ΔV, step ■
On the other hand, in the case of "NO", the opposite is true, so in step (2), the pressure command values VH, L-VHRR are increased by a minute value ΔV, and then the process moves to step (2). In addition, based on the judgment in step ① above, the actual vehicle high price
If ll matches the target vehicle height value H3, also step ■
Process.

In step (2), the arithmetic processing unit 78 reads the A/D-converted acceleration detection signal G via the interface circuit 76, and temporarily stores the value as the acceleration acting on the vehicle body. This acceleration G is actually the acceleration in the longitudinal, lateral, and vertical directions of the vehicle body. Therefore, the next step [phase]
Now, based on the acceleration G, the attitude control command value vSFL~VS
Calculate RR.

Specifically, for the acceleration Gx in the longitudinal direction,
The deviation from the neutral value (detected value when the acceleration is zero) is multiplied by 8 for the longitudinal control gain, and for the lateral acceleration G7, the deviation is multiplied by the lateral control gain Kv, and the vertical control gain is multiplied by 8. For the acceleration G2 in the direction, the deviation is integrated to calculate a value corresponding to the vertical speed, this integral value is multiplied by 2 for the vertical direction control gain to obtain the individual value, and then they are added. Command value in the direction that resists posture change ■S, L
- Find VS+B for each axis position.

Next, move to step
□ and the attitude system Il command value VS□ to ■S□ are added to each axis position to calculate the pressure command value vrt to ■□ of each axis position consisting of a voltage value, and the process moves to step @. In step @, the arithmetic processing unit 78 individually outputs the pressure command values VFL to ■□ to the D/A converters 72A to 72D via the interface circuit 76.

As a result, the pressure command values VFL~■□ converted into analog quantities by the D/A converters 72A~72D are
4A to 74D as a target value, and the circuit 74A
~74D supplies the command current IFL""IR* corresponding to the pressure command value VFL-Vllll+ to the corresponding pressure control valves 26FL-26RR, respectively.

Next, in step (2), it is determined whether or not the control has ended, and if the control has not ended, the process returns to step (2) and the above processing is repeated.

On the other hand, when the ignition switch 86 is turned off while the above-mentioned control is being performed, the first transistor 82 in the control device 33 is turned off, that is, it becomes non-conductive, but the second transistor 83 becomes conductive. Since the contact 84A of the relay 84 maintains the closed (on) state, the power supply to the control device 33 also continues. Therefore, the arithmetic processing unit 78 can continue the process shown in FIG. 6 even after the engine has stopped, and since the switch signal IG is at zero level when the ignition switch 86 is in the OFF state, the arithmetic processing unit 78 makes rYESJ, that is, the judgment to stop the engine, in step (3). put down.

Therefore, the arithmetic processing unit 78 performs the processing in steps [phases].
Then, the pressure switch signal SS is read through the interface circuit 76, and the judgment in step (2) is made. This determination is whether the pressure switch 32 is on or not. Therefore, if rNo, that is, the pressure switch 32 is off, it is determined that the operating check valve 52 is not yet closed, and the process moves to step (2).

In step (2), the arithmetic processing unit 78 reads the latest pressure command values (2) FL to (2) stored in the storage device 80 at that time, and then proceeds to step O9 (3). In step @, it is checked whether the read pressure command value VFL~■□ matches the neutral value VH (the value corresponding to the neutral pressure Ps in this embodiment), and if rYES, go to step ■Determine whether FL~Vllll>VNJ (this determination is made by giving vH a predetermined range).If this determination is YESJ, the command was higher than the neutral value V8, so At step ■, command value V, L-V■
is decreased by a minute value ΔV, and the process moves to step [phase]. On the other hand, when the determination in step (2) is "NO", this is the opposite of the above, and therefore, in step 0, the command value VFL~■□ is increased by the minute value Δ■, and the process moves to step [phase].

In step [phase], step ■.

The pressure command value VFL''VRI adjusted in step (2) is output in the same manner as in step @, and then the process returns to step 0 and the above-described process is repeated.

On the other hand, while repeating the pressure control after stopping the engine as described above, when the operating check valve 52 closes and the cylinder pressure is sealed, back pressure is built up in the pressure control valves 26FL to 26RR, and the pressure in the drain pipe 48r increases to the set value. P, and the pressure switch 15 is turned on. This allows step ■
Then, the determination of rYEsJ is made, and the arithmetic processing unit 78 performs the process of step @. In this process, the transistor switching signal ST, which had been kept "on", is turned "off" to zero level. As a result, the second transistor 83 becomes non-conductive and the excitation state of the relay 84 is released, so the relay contact 84A is turned off and the battery 84 is turned off.
The power supply path from 8 to the control device 33 is cut off, and the control of the control device 33 is also terminated.

Next, the overall operation will be explained.

Assuming that the vehicle is currently running with the engine in operation, the control device 33 performs step (1) in FIG. 6, as described above.
While repeating the process of ~■, perform vehicle height control and step ■ regarding steps ■~■.

Perform attitude control regarding [phase]. That is, the actual vehicle height value HyL'=H□ at each width position is adjusted to the target vehicle height value H5, and if the vehicle body posture changes due to turning, acceleration/deceleration, driving on rough roads, etc., control is performed to appropriately suppress this fluctuation.

Even when the vehicle stops from this state and enters an idling state, the same vehicle height and attitude control as when the vehicle is running is performed.

It is assumed that the engine is stopped in this stopped state. As a result, the ignition switch 86
is turned off, the first transistor 82 in the control device 33 becomes non-conductive, but the second transistor 83
The power supply state is maintained by the conduction of , and the control device 33 performs steps 0 to (2I) in FIG. Therefore, even after the engine has stopped, the pressure command value VFL~■
By gradually bringing □ closer to the neutral value vN, the actual vehicle height value is gradually adjusted to the value determined by the neutral value ■8. In other words, when the engine stops, the operation of the control device 33 immediately stops, causing the pressure command value VFL~■□ to become zero, and before the operating check valve 52 closes, the cylinder pressure plummets and the vehicle height value suddenly changes. The situation is definitely eliminated.

On the other hand, in the hydraulic pressure supply device 18, when the engine is stopped, the driving of the hydraulic pump 42 is also stopped, so the discharge pressure thereof is rapidly reduced. This decrease is initially compensated for by the high pressure oil accumulated in the line pressure pipe 48s and the accumulator 24.24 or the hydraulic cylinders 28FL to 28RH, but these oils are consumed and the pressure control valves 26PL to 28RH are used.
6RR, as it gradually returns to the oil tank 40 via the operating check valve 52, 1, each pressure control valve 26
The supply pressure to F+, ~26RR decreases. When this supply pressure (pilot pressure PP) reaches the set value Pr+(=neutral value p)l), at that point the operating check valve 52 shifts from the open state to the closed state, and the pressure control valve 26FL Build up back pressure to ~26RR and check valve 50
And a path from the operating check valve 52 to the load side is sealed. In this sealed state, the supply pressure = control pressure = return pressure for the control valves 26FL to 26RR, and each pressure is approximately equal to the set value P, so the hydraulic cylinder 28FL
All internal pressures of ~28RR are maintained at the set value P, and the vehicle height value is also maintained.

In addition, the operating check valve 52 closes and back pressure builds up.
When the value reaches the set value Ps, the pressure switch 32 is turned on, so that the control in steps (2) and (2) in FIG. 6 described above is carried out. That is, the second transistor 83 of the control device 33 becomes non-conductive immediately after the operating check valve 52 closes, so that the second transistor 83 of the control device 33 becomes non-conductive.
The power supply to is cut off, and the control device 33 ends the control.

After this, the vehicle height is maintained in the state where the internal pressure is maintained as described above.

In this way, in this embodiment, even if the supply pressure reduction time (see tD in FIGS. 7 and 10) is longer or shorter due to different environmental temperatures, the automatic check valve 52 is automatically The power supply will be canceled automatically. therefore,
It is possible to reliably avoid a situation where power is supplied even after the operating check valve 52 is closed, as in the conventional case, and wasteful consumption of battery power can be prevented. Therefore, even if the vehicle is repeatedly driven for a short period of time, battery life is significantly reduced and there is no need to increase battery capacity, which not only reduces costs but also improves fuel efficiency by avoiding weight increase. .

In this embodiment, the processing of steps [phase] to (2) in FIG.

D/A converters 72A to 72D and drive circuits 74A to 7
4D constitutes vehicle height control means, and the second transistor 83
．． Relay 84. Ignition switch 86. and the sixth
The processing of steps (2) and (2) in the figure constitutes a power supply maintenance means. In addition, the pressure switch 32 and the step [phase] in FIG.
The process of ■ constitutes the closing operation detection means, and the step of FIG.
The process corresponds to the power release means.

In addition, the pressure switch 3 of the closing operation detection means in each invention
The mounting positions of the valves 2 and 2 are not necessarily limited to those of the embodiment described above (for example, the check valve 50 and the accumulator 2 in the line pressure pipe 48s of FIG.
4, the supply pressure to the control valves 26FL to 26RR is detected, and when the supply pressure falls below the set value and the pressure switch 32 is turned off, the operating check valve 5
2 may be determined to be in the closed state. Further, this closing operation detection means may directly detect the position of the poppet 52B of the operated check valve 52 shown in FIG. 3 to detect the closed state. The position of the shaft taken out from the valve housing 52A may be detected electrically or optically, and the state (closed state) in which the valve seat 52B is in contact with the valve seat 52D may be detected.

Furthermore, in addition to the configuration described in the above-described embodiments, for example, an engine rotation speed detector may be used to determine whether or not the engine has stopped in the power source maintenance means of each invention, and the determination may be made based on the engine rotation speed.

Furthermore, the active suspension in each invention is not necessarily limited to one using oil as in the above-mentioned embodiments, but can also be implemented, for example, by a suspension using air pressure, or by controlling the flow rate of fluid. This method can also be applied to a suspension system configured to change the speed of the cylinder. Moreover, without using a microcomputer for the control device 33,
An equivalent function can also be performed using an analog circuit.

[Effects of the Invention] As explained above, in the active suspension of the present invention, the power supply is maintained once after the engine is stopped, and in this state, the return path opening/closing mechanism determines when to switch from the open state to the closed state. Since the power supply is canceled when this is detected, the power supply is forcibly stopped when the return passage opening/closing mechanism is in the closed state, which eliminates the need to control the cylinder internal pressure, that is, when the cylinder internal pressure is sealed. , unlike the conventional configuration that always maintains power supply for a certain period of time after the engine stops, the power supply time is reduced to the minimum necessary, and power supply continues even after cylinder pressure is filled (internal pressure control is not effective). Wasteful power supply from the vehicle battery is reliably eliminated, and the probability of the battery dying is further reduced.Therefore, there is no need to worry about the battery dying and increasing the battery capacity, leading to cost reduction. This also has the effect of suppressing the increase in vehicle weight and improving fuel efficiency.

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to the claims of each invention, Fig. 2 is a schematic configuration diagram showing an embodiment of the invention, Fig. 3 is a sectional view showing the structure of the operated check valve, and Fig. 4 is the control characteristics of the pressure control valve. Figure 5 is a partially block circuit diagram showing the configuration of the control device, Figure 6 is a schematic flowchart showing an example of processing performed by the control device, and Figure 7 is the supply pressure after the engine is stopped. Figure 8 is a graph showing the relationship between oil viscosity and leakage amount, Figure 9 is a graph showing the relationship between temperature and viscosity, and Figure 10 is a graph showing the relationship between oil viscosity and viscosity. It is a timing chart explaining the merits and demerits of supply pressure. In the figure, 12 is a wheel side member, 14 is a vehicle body side member, 16 is an active suspension, 18 is a hydraulic pressure supply device (fluid pressure supply device), 26FL to 26RR are pressure control valves (control valves),
28FL to 28RR are hydraulic cylinders (fluid pressure cylinders)
, 32 is a pressure switch, 33 is a control device, 48s is a line pressure line (supply line), 48r is a drain line (return line),
50 is a check valve (return valve), 52 is an operating check valve (return path opening/closing mechanism), 66 is a microcomputer, 83 is a second transistor, 84 is a relay, 86 is an ignition switch, and 88 is an on-board battery.

Claims (4)

[Claims] (1) A fluid pressure cylinder interposed between the vehicle body and the wheels, a control valve that controls the working fluid from the fluid pressure supply device supplied to the fluid pressure cylinder according to a command value, and the fluid pressure A check valve inserted in the supply path between the supply device and the control valve, and a check valve inserted in the return path between the fluid pressure supply device and the control valve, when the supply pressure to the control valve drops to a set value. In an active suspension comprising a return path opening/closing mechanism that closes the control valve, and a control device that provides a command value to the control valve, the control device includes at least a power supply maintenance means that maintains power supply from the vehicle battery even after the engine is stopped. While the power supply maintaining means maintains the power supply, the vehicle height control means provides a command value for controlling the vehicle height value to the control valve even after the engine is stopped, and the return passage opening/closing mechanism changes from the open state to the closed state. and a power release means that releases the power supply maintaining state of the power supply maintaining means when the closing action detecting means detects the switching to the closed state. This active suspension is characterized by: (2) The closing operation detection means is means for detecting return pressure on the upstream side of the return path opening/closing mechanism, and determining switching to the closed state when this return pressure reaches the set value. The active suspension according to item (1). (3) Claim (1), wherein the closing operation detection means is means for detecting the supply pressure to the control valve, and determining whether to switch to the closed state when the supply pressure reaches the set value. Active suspension as described. (4) The active suspension according to claim 1, wherein the closing operation detecting means is configured to detect a mechanical displacement accompanying transition of the return path opening/closing mechanism to the closed state.