JP2846011B2 - Vehicle suspension device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a fluid cylinder disposed between a vehicle body-side member and each wheel-side member, and a working fluid for a hydraulic chamber of the fluid cylinder. The present invention relates to a vehicle suspension device including an actuator that changes suspension characteristics by controlling supply and discharge.

[Conventional technology]

Conventionally, as shown in, for example, JP-A-63-130418, the supply and discharge of working fluid to and from a fluid cylinder provided between a vehicle body-side member and each wheel-side member are controlled in accordance with the running state of the vehicle. There is known an active suspension device which changes the suspension characteristics by changing the amount of fluid in a fluid cylinder. This conventional active suspension device includes a flow control valve for controlling the supply and discharge of a working fluid to and from a hydraulic chamber of the fluid cylinder, an acceleration detecting means for detecting a vertical acceleration of the vehicle body, and a detection signal of the acceleration detecting means. And a control unit for multiplying an output signal of the integration unit by a predetermined gain coefficient to obtain a control amount of a flow control valve for controlling the fluid cylinder. When it is confirmed that the vehicle body is bouncing in response to a signal or the like, a control signal corresponding to the control amount obtained by the control means is output to the flow control valve to supply and discharge the working fluid to and from the fluid cylinder. The bounce of the vehicle body is reduced by performing feedback control.

In the above active suspension device,
An accumulator for storing the working fluid supplied to the fluid cylinder is provided, the working fluid is supplied from the pump driven by the engine into the accumulator to accumulate the pressure, and the working fluid stored in the accumulator is supplied through the flow control valve. By supplying the working fluid to the fluid cylinder, the supply pressure of the working fluid is maintained at a predetermined value regardless of the running state of the vehicle.

[Problems to be solved by the invention]

The conventional active suspension device has detecting means for detecting the accumulated pressure in the accumulator, and when it is confirmed by the detecting means that the accumulated pressure has become equal to or less than a preset reference value, the accumulator is not charged. Is configured to supply a working fluid to the pressure generator and start accumulating pressure. Therefore, when the pressure accumulation is started and the power of the engine is consumed, for example, when the vehicle is accelerating, there is a problem that the feeling of acceleration of the vehicle is impaired and the traveling feeling of the vehicle is deteriorated. That is, in order to supply the working fluid from the pump to the accumulator to increase the accumulated pressure, a considerable amount of power is required. There was a problem of giving.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and supplies a working fluid from a pump driven by an engine to an accumulator by operating a switching valve without giving a driver an uncomfortable feeling. It is an object of the present invention to provide a vehicle suspension device capable of controlling the accumulated pressure in the vehicle to maintain an appropriate value.

[Means for solving the problem]

The invention according to claim 1 provides a suspension cylinder by controlling a fluid cylinder disposed between a vehicle body-side member and each wheel-side member and supply and discharge of a working fluid to and from a hydraulic chamber of the fluid cylinder. In a vehicle suspension device having a flow control valve to be changed, a pump driven by an engine, a switching valve for supplying a fluid discharged from the pump to an accumulator to adjust the accumulation pressure, and a storage valve of the accumulator. Accumulating pressure detecting means for detecting pressure, accelerating state detecting means for detecting an accelerating state of the vehicle, and accumulating pressure of the accumulator according to a detection signal output from the accumulating pressure detecting means, based on a predetermined threshold value. Determining means for determining whether or not the pressure is smaller than the threshold value. If the determination means determines that the accumulated pressure is smaller than a threshold value, the switching is performed. Activating the accumulator to start accumulating pressure, and changing means for changing the accumulating control state of the accumulator according to the detection signal of the accelerating state detecting means. When it is confirmed that the vehicle is accelerating according to the detection signal of the means, the threshold value for judging whether or not the accumulator value of the accumulator is at the level at which the accumulator starts accumulating is determined by the judgment means. The pressure accumulation control state of the accumulator is changed by selecting a value smaller than that at the time of acceleration.

According to a second aspect of the present invention, in the vehicle suspension device according to the first aspect, the change means is prohibited from operating when accelerating from the pressure accumulation state.

[Action]

According to the present invention having the above configuration, when it is confirmed that the vehicle is in the accelerating state in response to the detection signal of the accelerating state detecting means, it is determined whether or not the accumulator value of the accumulator is the level at which the accumulator starts accumulating in the determining means As a threshold for judging whether or not the value is smaller than when the load is low,
Alternatively, the accumulation of pressure can be prevented from being performed when the engine is under a high load by stopping the accumulation of pressure control by the control means.

〔Example〕

FIG. 1 shows a schematic configuration of a vehicle suspension device according to the present invention. Fluid cylinders 3 are provided between a vehicle body 1 of the vehicle and front wheels 2F and rear wheels 2R. The fluid cylinder 3 includes a cylinder body 3a having a lower end connected to a vehicle-side member, and a cylinder body 3a.
And a piston 3b which is inserted therein and forms a hydraulic chamber 3c inside the cylinder body 3a. On the upper surface of the piston 3b, a piston rod 3d whose upper end is supported by the vehicle body 1 is projected.

A communication passage 4 communicating with a gas spring 5 is connected to the hydraulic chamber 3c of the fluid cylinder 3. The gas spring 5 is divided into a gas chamber 5f and a hydraulic chamber 5g by a diaphragm 5e. The hydraulic chamber 5g is connected to the communication passage 4 and a passage provided in a piston 3b of the fluid cylinder 3 through a passage provided in the piston 3b. It communicates with the hydraulic chamber 3c of the fluid cylinder 3.

A hydraulic pump 8 driven by an engine (not shown) is provided at a front end of the vehicle body 1, and a hydraulic pipeline 10 having a flow control valve 9 is connected to the hydraulic pump 8. The flow control valve 9 controls the supply and discharge of hydraulic oil to and from the fluid cylinder 3 to adjust the flow rate of hydraulic oil.

Further, the vehicle body 1 includes a pressure sensor 12 for detecting an accumulated pressure of an accumulator 22 for accumulating hydraulic oil supplied from a hydraulic pump 8, a hydraulic pressure sensor 13 for detecting a hydraulic pressure of a hydraulic chamber 3c of each fluid cylinder 3, and The displacement of the vehicle height for each wheel 2F, 2R,
That is, a vehicle height sensor 14 that detects a cylinder stroke,
A vertical acceleration sensor 15 for detecting the vertical acceleration of the vehicle, that is, an acceleration on the springs of the wheels 2F and 2R, a steering angle sensor 16 for detecting the steering angle of the steering wheel, and a vehicle speed sensor 17 for detecting the traveling speed of the vehicle. Is provided. One vertical acceleration sensor 15 is provided above each of the left and right front wheels 2F, and one is provided at the center of the left and right rear wheels 2R in the vehicle width direction.

The detection signals of the sensors 12 to 17 are input to a controller 18 having a CPU and the like inside. By outputting a control signal corresponding to the detection signal from the controller 18 to the flow control valve 9, the flow rate of the hydraulic oil supplied to and discharged from each fluid cylinder 3 is controlled, and the variable control of the suspension characteristics is performed. It has become.

FIG. 2 shows a hydraulic circuit for controlling the supply and discharge of hydraulic oil to and from the fluid cylinder 3. In this hydraulic circuit,
A hydraulic pump 8 driven by the engine 20 is provided. An accumulator 22 is provided in a discharge pipe 21 of the hydraulic pump 8, and a downstream portion thereof is a pipe 23 for the front wheel 2F.
F and a pipe 23R for the rear wheel 2R. Front wheel 2F above
Pipe 23F has a downstream portion branched into left and right pipes 23FL and 23FR, and these two pipes 23FL and 23FR are connected to the hydraulic chambers 3c of the corresponding fluid cylinders 3FL and 3FR, respectively. Further, the pipe 23R for the rear wheel 2R has a downstream portion that is a pipe 2R for the left rear wheel.
3RL and a pipe 23RR for the right rear wheel.
L and 23RR are connected to the hydraulic chambers 3c of the corresponding fluid cylinders 3RL and 3RR, respectively.

Each gas spring connected to each of the above fluid cylinders 3FL to 3RR
5FL to 5RR have four gas spring members 5a, 5b, 5c, and 5d, respectively.
The gas spring members 5a to 5d are connected to the communication path 4 via branch communication paths 4a to 4d, respectively. Further, in the branch passages 4a to 4d of the gas spring members 5a to 5d,
Orifices 25a to 25d are provided, respectively, and a basic function as a suspension device is achieved by a damping action of the orifices 25a to 25d and a buffer action of gas sealed in the gas chamber 5f of each of the gas spring members 5a to 5d. It is configured as follows.

In the communication passage 4 located between the first gas spring member 5a and the second gas spring member 5b of each of the gas springs 5FL to 5RR, a damping force switching valve 26 that switches the damping force by adjusting the passage area is provided. Is provided. The damping force switching valve 26 has two positions, an open position for opening the communication passage 4 and a throttle position for reducing the passage area of the communication passage 4.

The discharge pipe 21 of the hydraulic pump 8 has an accumulator 22
An unload relief valve 28 is provided in the vicinity of. As will be described later, the unload relief valve 28 is opened according to a control signal output from the controller 18 when the accumulated pressure of the accumulator 22 detected by the pressure sensor 12 falls below a predetermined value. Is switched to the closed position and the hydraulic oil discharged from the hydraulic pump 8 is supplied to the accumulator 22. When the accumulated pressure reaches a set value, the hydraulic oil is switched to the open position and the discharged oil is returned to the reserve tank 29. It is configured as follows. The hydraulic oil stored in the accumulator 22 in this way is supplied to each fluid cylinder 3 according to the stored pressure.

Since the hydraulic circuit of the fluid cylinder 3 provided for each wheel has the same configuration, the configuration of the hydraulic circuit for the left front wheel will be described below. Piping 23FL for the above left front wheel
The flow control valve 9 is provided with three positions: a stop position shown for closing all ports, a supply position for opening the pipe 23FL to the supply side, and a discharge position for communicating the pipe 23FL to the return passage 32. And a pair of pressure compensating valves 9a
Built-in. The pressure compensating valve 9a is provided to maintain the hydraulic pressure of the fluid cylinder 3 at a predetermined value when the flow control valve 9 is at the supply position or the discharge position.

On the fluid cylinder 3 side of the flow control valve 9, a pilot pressure responsive on-off valve 33 for opening and closing the pipe 23FL for the left front wheel is provided. The on-off valve 33 is an electromagnetic valve 3 disposed in a front wheel side pipe 23F communicating with the discharge pipe 21 of the hydraulic pump 8.
When the valve 4 is opened, the hydraulic pressure of the solenoid valve 34 is introduced as a pilot pressure. When the pilot pressure is equal to or higher than a predetermined value, the valve is opened to open the pipe 23FL, and the flow control valve 9 operates the fluid cylinder 3. This enables oil supply / discharge control.

In FIG. 2, reference numeral 35 denotes a relief valve which opens when the hydraulic pressure chamber 3c of the fluid cylinder 3 abnormally rises and returns the hydraulic oil in the hydraulic pressure chamber 3c to the return passage 32. Also sign
36 is an ignition key interlocking valve connected to the discharge pipe 21 of the hydraulic pump 8 near the accumulator 22;
When the ignition key is in the off state, the operating oil is opened to return the hydraulic oil stored in the accumulator 22 to the reserve tank 29 to release the high pressure state. Reference numeral 37 denotes a pump relief valve that returns the discharge pressure oil to the reserve tank 29 to reduce the pressure when the discharge pressure of the hydraulic pump 8 abnormally increases, and reference numeral 38 denotes a return accumulator provided in the return passage 32. , Fluid cylinder 3
Pressure is accumulated when the hydraulic oil is discharged from the engine.

FIGS. 3A and 3B are block diagrams showing the control function of the suspension characteristics by the controller 18. FIG. To the controller 18, the detection signal X _FL outputted from the vehicle height sensors 14, X _FR, X _RL, a control system A for controlling the vehicle height to a target vehicle height based on the X _RR, detection signals X _FL, X _FR , X _RL , X
Car obtained from _RR height displacement velocity signals _{Y FL, Y FR, Y RL} , a control system B for controlling the vehicle height displacement rate based on Y _RR, detection signals G of vertical acceleration output from the vertical acceleration sensor 15 _FL ,
G _FR, the control system C to reduce the vertical vibration of the vehicle based on G _R
And a control system D for controlling the vehicle body torsion based on the hydraulic pressure detection signals P _FL , P _FR , P _RL , and P _RR output from the hydraulic pressure sensors 13 of the respective fluid cylinders 3. Have been.

The control system A, the detection signal X _FL of the vehicle height sensor 14 for detecting a vehicle height displacement at the installation portions of the left and right front wheels 2F, together with summing X _FR, the installation portion of the wheel 2R right and left rear to this value Detection signals X _RL , X of the vehicle height sensor 14 for detecting the vehicle height displacement amount
A bounce component calculation unit 40 that adds the total value of _RR to calculate the bounce component of the vehicle, and a total value X _FL of the detection signals on the front wheel side
A pitch component calculator 41 for subtracting the total value X _RL + X _RR of the detection signals of the rear wheels from + X _FR to calculate a pitch component of the vehicle;
And a roll component arithmetic unit 42 for calculating the roll component of the vehicle by adding the difference X _RL -X _RR of the detection signal of the rear-wheel side differential X _FL -X _FR for the front wheel of the detection signal.

Further, in the control system A, reference numeral 43 is the bounce and bounce component of the vehicle which is inputted from the ingredient calculation unit 40, the target average vehicle inputted from the target average vehicle height setting section 40a high T _H
If, based on the gain coefficient K _B1 set in advance, a bounce control section for determining a control amount to the flow rate control valve 9 in the bounce control for each wheel. Reference numeral 44 denotes a pitch control unit that obtains a control amount of each flow control valve 9 in pitch control based on the vehicle pitch component input from the pitch component calculation unit 41 and a preset gain coefficient K _P1. . Reference numeral 45 denotes a roll component of the vehicle input from the roll component calculation unit 42 and a target roll displacement amount setting unit 42.
and the target roll displacement amount T _R that is input from a, based on the gain coefficient K _RF1, K _RR1 that is set in advance, the roll control so that the actual vehicle height is the value corresponding to the target roll displacement amount T _R Is a roll control unit that obtains the control amount of each flow control valve 9 in.

Then, each control amount obtained by each of the control units 43, 44, 45 is, after its sign is reversed for each wheel as necessary,
The bounce, pitch and roll components are added, and control signals Q _FL1 and Q of the control system A for controlling the vehicle height displacement are added.
Output as _FR1 , _QRL1 , and _QRR1 . Incidentally, between the each car height sensor 14 and the arithmetic unit 40, 41 and 42, the detection signal X _FL of the vehicle height sensor 14, X _FR, X _RL, the dead zone X _H where X _RR is set in advance beyond The dead band devices 70 that output signals only when the power supply is turned off are provided.

The control system B differentiates the values of the detection signals X _FL , X _FR , X _RL , and X _RR output from the vehicle height sensor 14 to obtain vehicle height displacement speed signals Y _FL , Y _FR , Y _RL , Y a differentiator 46 for determining the _RR, the total value Y _FL + from Y _FR, sum Y _RL + Y _RR and by subtracting the pitch component of the vehicle height shift of the signal for the rear wheels of the front wheel vehicle height displacement velocity signals The roll component of the vehicle is obtained by adding the difference Y _RL −Y _RR of the vehicle height displacement speed signal on the rear wheel side to the difference Y _FL −Y _FR of the vehicle height displacement speed signal on the front wheel side and the pitch component calculation unit 47a that calculates the roll component of the vehicle. And a roll component calculation unit 47b that obtains

In the control system B, reference numeral 48 denotes a control amount of each flow rate control valve 9 in pitch control based on a vehicle pitch component input from the pitch component calculation unit 47a and a preset gain coefficient K _P2. Is a pitch control unit that obtains Reference numeral 49 denotes a vehicle roll component input from the roll component calculation unit 47b, and a preset gain coefficient.
It is a roll control unit that calculates the control amount of each flow control valve 9 in roll control based on K _RF2 and K _RR2 . The control amounts of the pitch and roll obtained by the two control units 48 and 49 are added as necessary after the sign is reversed for each wheel, and the control amount of the control system B for controlling the vehicle height displacement speed is added. The signals are output as signals Q _FL2 , Q _FR2 , _QRL2 , and _QRR2 .

Moreover, both sensors the control system C is the detection signal G _FL, G _FR of the vertical acceleration sensor 15, a bounce arithmetic unit 50 sums the G _R seek bounce component of the vehicle, located to the left and right front wheels 2F side
Average value calculation unit 51a for calculating the average value of 15 detection signals G _FL and G _FR
When a pitch component arithmetic unit 51 for obtaining the pitch component of the vehicle the value of the detection signal G _R of the sensor 15 located to the rear wheel 2R side from the average value obtained in the average value calculating unit 51a subtracts, left front wheel And a roll component calculation unit 52 that calculates the roll component of the vehicle by subtracting the value of the detection signal _GFR of the sensor 15 on the right front wheel side from the detection signal _GFL of the sensor 15 on the right side.

In this control system C, reference numeral 53 bounces obtaining a bounce component of the vehicle determined by the bounce component calculating section 50, based on the gain coefficient K _B3 that is set in advance, the control amount of each flow control valve 9 in the bounce control It is a control unit. Reference numeral 54 denotes a pitch control unit that obtains a control amount of each flow control valve 9 in pitch control based on the vehicle pitch component obtained by the pitch component calculation unit 51 and a preset gain coefficient K _P3. . _Reference numeral 55 denotes a roll control amount for _obtaining a control amount of each flow control valve 9 in the roll control based on the roll component of the vehicle obtained by the roll component calculation unit 52 and the preset gain coefficients K _RL3 and K _RR3. It is.

The control amounts of the bounce, pitch, and roll obtained by the control units 53, 54, and 55 are added, after the sign is reversed for each wheel, if necessary, and the control amount is controlled to control the vertical vibration of the vehicle. It is output as the control signals G _FL3 , Q _FR3 , G _RL3 , and Q _RR3 of the system C. In addition, each of the above vertical acceleration sensors 15,
Between each operation unit 50, 51, the detection signal G _FL of the acceleration sensor 15, G _FR, only when exceeding the dead zone X _G where G _R is set in advance, the dead zone 80 for outputting a signal Each is arranged.

The control system D for suppressing the torsion of the vehicle includes a total hydraulic pressure value P _FL + P _FR and a hydraulic pressure difference P _FL according to the detection signals P _FL and P _FR of the hydraulic pressure sensor 13 provided on the front wheel 2F side. The hydraulic pressure ratio calculating section 60a on the front wheel 2F side for calculating the ratio to −P _FR and the total hydraulic pressure value P _RL according to the detection signals P _RL and P _RR of the hydraulic pressure sensor 13 provided on the rear wheel 2R side. Warp control unit 6 including a hydraulic pressure ratio calculation unit 60b on the rear wheel 2R side that calculates the ratio of + P _RR and the hydraulic pressure difference P _RL −P _RR
It has 0.

And from the liquid pressure ratio determined by the liquid pressure ratio calculating section 60a of the front wheel 2F side, subtracting the value obtained by multiplying the gain coefficient W _F to the liquid pressure ratio determined by the rear wheel 2R side of the liquid pressure ratio calculating section 60b. Then the above subtraction result, the value obtained by multiplying the gain coefficient W _A, gain factor
After multiplying by W _C , by inverting one of the positive and negative sides of the front wheel 2F, the control amount on the front wheel side in the warp control for suppressing the torsion of the vehicle body is obtained, and without multiplying the gain coefficient W _C , the rear wheel 2R by inverting one polarity of, determine the control amount of the rear wheel 2R side, and outputs a control signal _{Q FL4, Q FR4, Q RL4} , Q RR4 corresponding to these control amounts.

As described above, the vehicle height displacement components Q _FL1 , Q _FR1 , Q _FL1 , Q _FL1 ,
Q _RL1 , Q _RR1 and vehicle high displacement velocity components Q _FL2 , Q _FR2 , Q _RL2 , Q
_RR2 , the vertical acceleration components Q _FL3 , Q _FR3 , Q _RL3 , Q _RR3 and the pressure components Q _FL4 , Q _FR4 , Q _RL4 , Q _RR4 are added, so that the total control amounts Q ₁ , Q ₂ , Q ₃ and Q ₄ are obtained. The total control amount Qn (n = 1 to 4) is
To each fluid cylinder 3F according to the running state of the vehicle.
The flow rate of hydraulic oil for L to RR is controlled.

FIG. 4 is a block diagram showing a control function of the controller 18 for controlling the accumulated pressure of the accumulator 22 for supplying the working oil to the fluid cylinder 3. The controller 18 has a judging means 90 for judging whether or not the accumulated pressure of the accumulator 22 is smaller than a preset threshold value in accordance with the detection signal of the accumulated pressure detecting means comprising the pressure sensor 12.
When the determination means 90 determines that the accumulated pressure is smaller than a threshold value, the unload relief valve
The control means 91 outputs a control signal for starting the pressure accumulation by operating the switching valve consisting of 28, and the output signal output from the load detection means 92 such as a throttle valve sensor for detecting the load state of the engine 20. There is provided a changing means 93 for changing the pressure accumulation control state of the control means 91 by selecting the threshold value.

That is, in the determination means 90, the accumulator 22
Is determined to be less than the threshold value, and when it is confirmed that the hydraulic oil stored in the accumulator 22 has been consumed and the internal pressure has been reduced, the control means 91 sends the unload relief valve A control signal for switching 28 to the closed position is output to supply the discharge oil of the hydraulic pump 8 into the accumulator 22, and the accumulated pressure is increased to a preset upper limit value. The threshold is provided with two values, large and small, according to the load state of the engine 20.
If it is confirmed that the load of the
A small threshold value in the engine and engine 20
When it is confirmed that the load of the data is small, a large threshold value is selected, and the above-described determination is performed according to the selected threshold value.

A control operation for controlling the accumulated pressure of the accumulator 22 in the above configuration will be described with reference to a flowchart shown in FIG. When this control operation starts, first step
In S1, the accumulated pressure P of the accumulator 20 is read in accordance with the detection signal output from the accumulated pressure detection means including the pressure sensor 12, and in step S2, the engine is operated in accordance with the detection signal output from the load detection means 92. 20
Load EL of load. Next, in step S3, it is determined whether or not the flag F indicating the control state of the pressure accumulation operation and the control state of the suspension characteristics is 1, that is, whether or not the pressure accumulation is currently performed with the suspension characteristics being in the variable control state.

If YES is determined in step S3 and it is confirmed that the pressure accumulation is performed in the variable control state, in step S4, the accumulated pressure P of the accumulator 22 is set to a preset upper limit value, for example, 160 kg / It is determined whether it is cm ² or more. As a result of this determination, when it is confirmed that the accumulated pressure P has reached the upper limit, in step S5,
After outputting a control signal to switch the switching valve including the unload relief valve 28 to the open position and terminate the pressure accumulation, the flag F is set to 0 in step S6 to indicate that the pressure accumulation is not currently performed. I do. If it is determined in step S4 that the accumulated pressure P is less than the upper limit of 160 kg / cm ² , the process returns to continue the accumulated pressure operation.

As a result of the determination in step S3, when it is confirmed that the pressure accumulation is not performed in the variable control state,
In step S7, it is determined whether or not the flag F is 2, that is, whether or not the variable control of the suspension characteristics is currently suspended to accumulate pressure. As a result of this determination, when it is confirmed that the pressure accumulation is performed in the variable control halt state, in step S8, the accumulation pressure P of the accumulator 22 is set to a preset variable control halt value. ,
For example, it is determined whether it is 120 kg / cm ² or more. As a result of this determination, when it is confirmed that the accumulated pressure P has become equal to or greater than the set value of 120 kg / cm ² , in step S9, a control signal for starting variable control of suspension characteristics is output. , The flag F is set to 1 to indicate that the pressure accumulation operation is currently being performed in the variable control state. Also, as a result of the determination in step S8, when it is confirmed that the accumulated pressure value P is less than the set value of 120 kg / cm ² , the process returns to continue the accumulated pressure operation in the variable control pause state.

If NO is determined in step S7 and it is confirmed that the flag F is 0, that is, that no pressure accumulation is currently performed, the load EL of the engine 2 is set in advance in step S11. reference value determines whether a low load condition less than EL _1. As a result of this determination, when it is confirmed that the engine 20 is in the low load state, in step S12, it is determined whether or not the accumulated pressure value P is less than the threshold value at the time of low load, for example, less than 120 kg / cm ² . Is determined.

As a result of the determination in step S12, the accumulated pressure value P of the accumulator 22 becomes equal to the threshold value 120 kg / cm ² at the time of low load
If it is confirmed that the pressure is less than the predetermined value, the control signal for closing the switching valve is output in step S13 to start the pressure accumulating operation. It indicates that the pressure accumulation operation is being performed in the variable control state of the control. As a result, the pressure accumulation operation is continued until it is determined in step S4 that the accumulated pressure P is equal to or more than the upper limit value 160 kg / cm ² . Note that, in step S12, the accumulated pressure P is 120 kg / cm ²
If it is determined that this is the case, and it is confirmed that the amount of hydraulic oil in the accumulator 22 has not decreased so much, the routine returns without performing the above-described pressure accumulation.

Also, as a result of the determination in step S11, when it is confirmed that the engine 20 is in the high load state, in step S15, the accumulated pressure value P is less than the threshold value at the time of high load, for example, less than 110 kg / cm ^2. Is determined. If the result of this determination indicates that the accumulated pressure value P of the accumulator 22 is less than the high load threshold value 110 kg / cm ² , in step S16, the flow control valve 9
Was moved to the all-port closed position to suspend the variable control of the suspension characteristics, and output a control signal to start the pressure accumulation by closing the switching valve, thereby starting the pressure accumulation operation in the suspended state of the variable control. After, step
In S17, the flag F is set to 2. As a result, the pressure accumulating operation is continued until it is determined in step S8 that the accumulated pressure P is equal to or more than the reference value 120 kg / cm ² . Note that in step S15, the accumulated pressure P becomes 1
If it is determined that the pressure is 10 kg / cm ² or more, and it is confirmed that an amount of hydraulic oil capable of performing the variable control of the suspension characteristics is stored in the accumulator 22, the process returns without performing the above-described pressure accumulation. .

As described above, the threshold value for determining that the accumulated pressure P in the accumulator 22 has decreased and the accumulated pressure has to be started is selected according to the load EL of the engine 20. At the time of a high load of 20, the above-described determination is performed by selecting a threshold value smaller than that at the time of a low load (110 kg / cm ² ), so that the pressure accumulation operation is frequently performed at a high load such as an acceleration of a vehicle. And the running filling can be maintained in a good state. That is, when the vehicle is accelerating, the acceleration state detecting means including the load state detecting means 92 determines that the vehicle is in the high load state, and the accumulated pressure P is the minimum load required for executing the variable control of the suspension characteristics. Since the pressure accumulation is not performed until the pressure falls below the threshold value, it is possible to prevent the power of the engine 20 from being consumed for the pressure accumulation operation during acceleration and the acceleration performance of the vehicle from being reduced,
It is possible to effectively prevent occurrence of a situation in which the driver feels strange.

On the other hand, when the load is low, such as during decelerating running, the running feeling does not decrease so much even if the power accumulating operation is performed frequently and the power of the engine 20 is consumed. For this reason,
As described above, a value (120 kg / cm ² ) larger than that at the time of high load is selected as the threshold value at the time of low load, and the accumulated pressure P in the accumulator 22 is the minimum necessary to execute the variable control of the suspension characteristics. By performing pressure accumulation before the value falls below a proper value, the accumulated pressure P can be maintained at an appropriate value.

In the above embodiment, when the accumulated pressure P of the accumulator 22 is determined to be smaller than the high load threshold (110 kg / cm ² ) in the high load state of the engine 20,
Since the flow control valve 9 is moved to the all port closed state to suspend the active suspension control,
It is possible to prevent the variable control of the suspension characteristics from being executed in response to the insufficient accumulated pressure P.

In the above embodiment, two types of thresholds are set as the thresholds for determining whether or not to start accumulating by supplying the discharge oil of the hydraulic pump 8 into the accumulator 22. According to the configuration, one of the two threshold values is selected in accordance with the above. However, by providing three or more types of threshold values and selecting a threshold value according to the load state from among the three threshold values, finer granularity can be obtained. It may be configured to execute a complicated pressure accumulation control.

In addition, when it is confirmed that the engine 20 is in a high load state according to the detection signal output from the load detection means 92, the switching valve including the unload relief valve 28 is unconditionally opened to stop the accumulation of pressure. However, the pressure accumulation operation may be prohibited until the engine 20 shifts to the low load state.

〔The invention's effect〕

As described above, the present invention provides that when the accumulated pressure of the accumulator falls below a preset threshold,
Since the pressure accumulation control state of the control means that starts the pressure accumulation by activating the switching valve is configured to be changed according to the load state of the engine, by preventing the pressure accumulation from being frequently performed when the engine is under a high load, The traveling feeling can be prevented from being deteriorated, and the variable control of the suspension characteristics can be appropriately performed by positively accumulating the pressure at a low load and increasing the accumulated pressure of the accumulator to a predetermined value. There is an advantage.

[Brief description of the drawings]

1 is a schematic layout diagram of a vehicle suspension device according to the present invention, FIG. 2 is a hydraulic circuit diagram for controlling a fluid cylinder, and FIGS. 3A and 3B show a control function of suspension characteristics by a controller. FIG. 4 is a block diagram showing a control function of the pressure accumulating operation by the controller, and FIG.
FIG. 5 is a flowchart showing the above-described pressure accumulation control operation. 1 ... body, 2L, 2R ... wheels, 3 ... fluid cylinder, 3c
... hydraulic chamber, 8 ... pump, 9 ... flow control valve, 12 ...
Pressure sensor (accumulated pressure detecting means), 22: accumulator, 28: unload relief valve (switching valve), 90: determining means, 91: control means, 92: load detecting means (acceleration state detecting means) , 93 ... Change means.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-216311 (JP, A) JP-A-1-249509 (JP, A) JP-A-2-126974 (JP, U) JP-A-62-1 38488 (JP, U) Japanese Utility Model 1-105740 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) B60G 17/04 B60G 17/015

Claims (2)

(57) [Claims] 1. A fluid cylinder disposed between a vehicle body-side member and each wheel-side member, and a flow rate for changing suspension characteristics by controlling supply and discharge of a working fluid to and from a hydraulic chamber of the fluid cylinder. In a vehicle suspension device including a control valve, a pump driven by an engine, a switching valve for supplying a fluid discharged from the pump to an accumulator and adjusting the accumulated pressure thereof, and detecting the accumulated pressure of the accumulator Accumulator detecting means for detecting an accelerating state of the vehicle, and whether the accumulator pressure of the accumulator is smaller than a preset threshold value in accordance with a detection signal output from the accumulator detecting means. Determining means for determining whether or not the pressure is lower than a threshold value when the determining means determines that the accumulated pressure is smaller than a threshold value; Control means for operating the accumulator to start accumulating pressure; and changing means for changing the accumulating control state of the control means in accordance with a detection signal of the load detecting means. When it is confirmed that the vehicle is accelerating according to the detection signal, a threshold value for judging whether or not the accumulator value of the accumulator is at a level at which the accumulator starts accumulating is set in the above-mentioned judging means when the vehicle is not accelerating. A suspension device for a vehicle, characterized in that a pressure accumulation control state of an accumulator is changed by selecting an accumulator having a smaller value. 2. The vehicle suspension device according to claim 1, wherein the operation of the change means is inhibited during acceleration from the pressure accumulation state.