JPH06247127A - Active type suspension - Google Patents

Abstract

PURPOSE:To reduce the consuming energy of a pump, and to accomplish to suppress the car height reduction and the posture variation in a pump capacity stortage condition, to prevent the car height reduction in a long time parking condition, and to suppress a sudden posture variation at the engine starting in the condition the car height is reduced near the lower limit car height, without using an expansive valve. CONSTITUTION:To the suction side of a high pressure side pump b which discharge an operting fluid to a high pressure storage mechanism e, a low pressure storage mechanism k to store the exhaust fluid of a control valves f is provided, and a high pressure side pump drive control means n to drive and discharge the high pressure side pump b until the fluid pressure of the high pressure storage mechanism e exceeds a stop object pressure, when the fluid pressure is made less than an object set pressure, is provided. And a low pressure side pump drive control means h which compares the average fluid pressure value of both storage mechanisms k and e, and a preset neutral pressure area, and drives and discharges a lower pressure side pump p when the average value is less than the neutral lower limit pressure, while stops the drive and discharge of the lower pressure side pump p when the average value exceeds the neutral upper limit pressure, is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active suspension for keeping the posture of a vehicle body in an optimum state.

[0002]

2. Description of the Related Art Conventionally, as an active suspension,
For example, the one described in JP-A-4-135906 is known.

This conventional active suspension includes a fluid supply device having components such as a pump, a tank, a relief valve, an accumulator, a filter, and an oil cooler, and a pressure holding portion having components such as an operating check valve and a relief valve. An actuator provided between each of the front, rear, left and right wheels and the vehicle body, a pressure control unit including a pressure control valve for controlling the hydraulic pressure of each actuator, and between the pressure control unit and the pressure holding unit. It is composed of a provided fail-safe valve.

When the vehicle is traveling, the pump is always driven and, if necessary, the pressure control unit supplies an optimum amount of oil to the actuator or discharges the oil from the actuator to the tank side to optimize the posture. Keep on. At this time, in the pressure holding portion, the excess oil supplied from the pump is leaked from the relief valve to the tank side.

When an abnormality occurs in the electric system,
The fail-safe valve closes, and in cooperation with the operate check valve, the hydraulic pressure is maintained at a predetermined low pressure on the actuator side, and the traveling is guaranteed as a general mechanical suspension state.

[0006]

However, in the above-mentioned conventional apparatus, the problems to be solved as listed below remain.

The pump of the above-mentioned device is set to have a capacity capable of coping with the maximum fluid pressure consumption of the active suspension such as when traveling on a rough road. This is because when the pump capacity is insufficient, the fluid pressure in the line drops sharply, the vehicle height drops, and the amount of posture change such as roll or pitch that occurs when an external force is applied becomes large. This is because problems will occur. For this reason, during normal running without continuous rough road running, the excess oil amount is always leaked from the relief valve for use, resulting in a large amount of energy consumption and deterioration of fuel efficiency.

Since the line discharge pressure to the tank is atmospheric pressure (1 atm), if the operation of the pump and the pressure control unit is stopped when an abnormality occurs, the fluid of the actuator is discharged until the atmospheric pressure is reached, The vehicle height will drop significantly. Therefore, in order to prevent this decrease in vehicle height, an expensive fail-safe valve and an operate check valve for holding a predetermined amount of fluid are required in the fluid actuator, which causes an increase in cost and weight.

Since the discharge line pressure is set to 1 atm, if left for a long period of time, the vehicle height will drop due to hydraulic pressure leakage from each part. Then, when the engine is started after the vehicle height is reduced in this way, the vehicle height suddenly rises with the restart of the oil supply.
Therefore, in order to prevent such a problem, a flow control valve is needed (for example, "New Model Car F
GY32-1 "Nissan Motor Co., Ltd., Issued August 1991, C-50 to 73), resulting in cost and weight increase.

The present invention has been made by paying attention to the above-mentioned conventional problems. The energy consumption of the pump is reduced, and further, the vehicle height is lowered and the posture is changed when the pump capacity is insufficient, and the vehicle is parked for a long time. It is an object of the present invention to prevent the vehicle height from decreasing when the vehicle is running down and to suppress the sudden change in posture when the engine is started in a state where the vehicle height has dropped to around the minimum vehicle height without using an expensive valve.

[0011]

In the present invention, therefore, a low pressure storage mechanism for storing the working fluid pressure is provided on the discharge side of the control valve, and the hydraulic pressure of the high pressure storage mechanism for supplying the working fluid to the control valve is The above-described object is achieved by stopping the discharge drive of the pump when the pressure falls below a target set pressure that is set according to the vehicle body posture, and when the stop target pressure is exceeded.

That is, as shown in the claim correspondence diagram of FIG. 1, the active type suspension according to claim 1 is interposed between the vehicle body and each wheel, and the gap between the two can be changed. And a high-pressure storage mechanism having a high-pressure storage means c for storing the discharge working fluid supplied from the high-pressure side pump b to the fluid actuator a at high pressure and a check valve d for preventing backflow from the high-pressure side storage means c to the high-pressure side pump b. e, a control valve f interposed between the high-pressure storage mechanism e and the fluid actuator a to individually control the working fluid supply amount to each fluid actuator a and the working fluid discharge amount from each fluid actuator a, The attitude control means g for controlling the operation of the control valve f based on the input relating to the attitude change of the vehicle body, and the fluid pressure of the high pressure storage mechanism e are related to the attitude of the vehicle body at that time. The fluid pressure of the high-pressure storage mechanism e is detected in order to control to a target pressure range that is a pressure range that is equal to or higher than the maximum fluid pressure required by the fluid actuator a at that time set according to the input pressure. If the detected pressure exceeds the stop target pressure that is the upper limit pressure of the target pressure range, the discharge drive of the high-pressure side pump b is stopped if it is less than the target set pressure that is the lower limit pressure. The high-pressure side pump drive control means n is connected to the suction side of the high-pressure side pump b, the discharge side of the control valve, and the discharge side of the low-pressure side pump p whose discharge pressure is lower than that of the high-pressure side pump b, and the high-pressure storage means e
Low pressure storage mechanism k having a low pressure storage means h for storing the working fluid at a predetermined pressure lower than the low pressure, and a check valve j for preventing backflow from the low pressure storage means h to the low pressure side pump p.
And an average value of the fluid pressure of the low pressure storage mechanism j and the fluid pressure of the high pressure storage mechanism e are detected, and the average value is compared with a preset neutral pressure range which is a pressure range equal to or higher than the fluid pressure capable of supporting the vehicle weight. If the average value is less than the neutral lower limit pressure that is the lower limit value of the neutral pressure range, the low-pressure side pump p is driven to discharge, while if the average value exceeds the neutral upper limit pressure that is the upper limit pressure of the neutral pressure range, the low-pressure side pump is discharged. p
And a low-pressure side pump drive control means r for stopping the discharge drive of.

[0013]

When the vehicle is in operation, the attitude control means g controls the operation of the control valve f to optimally adjust the pressure of the fluid actuator a to control the attitude of the vehicle. As an example of this attitude control, when traveling on a good road or when the vehicle is stopped, the pressures of the four front, rear, left and right fluid actuators a are maintained at pressures corresponding to the vehicle weight to maintain the vehicle attitude flat. In addition, when an external force that causes roll, pitch, or bouncing is applied to the above state due to turning, acceleration / deceleration, or traveling on a rough road, the external force is generated based on the operation of the control valve f by the attitude control means g. The fluid is supplied to and discharged from the fluid actuator a so as to oppose to, and the vehicle posture is kept flat.

In this attitude control, the control valve f supplies the working fluid stored in the high-pressure storage mechanism e when supplying the working fluid to the fluid actuator a, and conversely, from the fluid actuator a. Is discharged toward the low pressure accumulator k.

By such control operation of the control valve f, the working fluid in the high-pressure storage mechanism e is supplied to the fluid actuator a, and the fluid pressure in the high-pressure storage mechanism e decreases, while
The working fluid discharged from the control valve f is stored in the low pressure storage mechanism k, and the fluid pressure in the low pressure storage mechanism k rises.

When the fluid pressure of the high-pressure storage mechanism e becomes less than the target set value which is the lower limit of the target pressure range set above the maximum output fluid pressure of the control valve f required at that time, the high-pressure side pump The drive control means n drives the high-pressure side pump b to discharge, sucks the working fluid of the low-pressure storage mechanism k and discharges it to the high-pressure storage mechanism e. As a result, at the same time as the fluid pressure of the high-pressure storage mechanism e increases, the fluid pressure of the low-pressure storage mechanism k decreases, and when the fluid pressure of the high-pressure storage mechanism e exceeds the stop target pressure, the high-pressure side pump drive control is performed. Means n is high-pressure side pump b
The ejection drive of is stopped. Thus, the high-pressure side pump b
Consumes the working fluid stored in the low-pressure storage mechanism k having a pressure higher than the atmospheric pressure, and therefore consumes less energy than the case where the working fluid having the atmospheric pressure is sucked and pressurized.

Further, even if the frequency of operation of the fluid actuator a becomes high and the capacity of the high pressure storage mechanism e becomes insufficient, the high pressure side pump b sucks the working fluid of the low pressure storage mechanism k. Since the fluid is discharged to the high-pressure storage mechanism e, the fluid pressure of the high-pressure storage mechanism e does not drop below the intermediate pressure between the fluid pressure of the low-pressure storage mechanism k and the fluid pressure of the high-pressure storage mechanism e. Therefore, even if the capacity becomes insufficient, the high-pressure storage mechanism e
The decrease in vehicle height and the lack of pressure to withstand external force, which are the same as when the internal fluid pressure decreases to atmospheric pressure, do not occur.

When the vehicle is parked for a long time, the working fluid leaked from the control valve f is stored in the low pressure storage mechanism k, so that the fluid pressure of the entire system communicating with the fluid actuator a becomes an average value of the entire system. Therefore, the fluid actuator a
As a result, the vehicle weight can be held, and the fluid actuator a cannot hold the weight at all unlike the conventional case. Further, if the operation of the high-pressure side pump b and the control valve f is stopped when an abnormality occurs, the fluid pressure of the entire system can be similarly maintained at a pressure higher than the atmospheric pressure. It should be noted that this pressure is determined by the capacities of the storage means c and h of both storage mechanisms e and k.

Next, at the time of starting the engine after the vehicle is stopped for a long time, if necessary, that is, the fluid pressure of the high-pressure storage mechanism e is less than the target set pressure (this target set pressure is a low value when the vehicle is stopped). ), The high-pressure side pump drive control means n drives the high-pressure side pump b to discharge to increase the fluid pressure in the high-pressure storage mechanism e. Further, the control valve f is operated as necessary to supply and discharge the working fluid, but the fluid pressure in the fluid actuator a does not rise from atmospheric pressure as in the conventional case, but until then, the high pressure storage mechanism e. Also, since the fluid pressure stored in the entire system communicated with the fluid actuator a such as the low-pressure storage mechanism k rises, it is difficult to cause a rapid posture change as in the conventional case. Therefore, it is possible to eliminate the conventional flow control valve.

Further, when the total amount of working fluid in each storage mechanism e, k and each actuator a decreases due to fluid leakage from the fluid actuator a, the following operation is performed. That is, when the total amount of working fluid decreases,
The average value of the fluid pressure of the high-pressure storage mechanism e and the fluid pressure of the low-pressure storage mechanism k decreases. Then, when this average value falls below a preset neutral lower limit pressure, the low pressure side pump drive control means r drives the low pressure side pump p to discharge. Therefore, the low pressure storage mechanism k is replenished with the working fluid. The discharge drive of the low-pressure side pump p is stopped when the average value exceeds the neutral upper limit pressure. The low-pressure side pump can be used when the working fluid is supplied to each storage mechanism or fluid actuator when the vehicle is offline or when the vehicle is repaired.

[0021]

Embodiments of the present invention will be described with reference to the drawings. First, the configuration will be described. FIG. 2 is a hydraulic system diagram showing an active suspension according to the first embodiment of the present invention. 1 _FR , 1 _FL , 1 _RR and 1 _RL are hydraulic cylinders interposed between a vehicle body and each wheel. (Fluid actuator) 2, a front pressure control unit, and 3 a rear pressure control unit. In this embodiment, oil is used as the working fluid.

The front pressure control unit 2 is provided with a right side pressure control valve 2a and a left side pressure control valve 2b for supplying / discharging oil to / from each of the hydraulic cylinders 1 _FR and 1 _FL . A valve 2c, a switching cock 2d, an accumulator 2e, and fail-safe check valves 2f, 2f are provided.

The rear pressure control unit 3 is also provided with a right pressure control valve 3a and a left pressure control valve 3b for supplying / discharging oil to / from each of the hydraulic cylinders 1 _RR , 1 _RL , and A check valve 3c, a switching cock 3d, an accumulator 3e, and fail-safe check valves 3f, 3f are provided.

The operation of each control valve 2a, 2b, 3a, 3b is controlled by a computer (posture control means) not shown. Further, since the configuration described above is the same as the device described in the document presented in the related art, detailed description will be omitted.

A high pressure line (high pressure storage mechanism) 4 and a low pressure line (low pressure storage mechanism) 5 are connected to each of the pressure control units 2 and 3. That is, as shown,
A low pressure pump 5a driven by a motor M _L to suck oil from the reservoir tank T and a high pressure pump 4a driven by a motor M _H to suck oil on the discharge side (low pressure line 5) of the low pressure pump 5a They are provided in series in order. A main check valve 4b, a high pressure accumulator (high pressure storage means) 4c, and a line pressure filter 4d are provided on the discharge side of the high pressure pump 4a, and a front main accumulator (high pressure storage means) 4e and a rear main accumulator ( High pressure storage means) 4f is provided,
These constitute a high pressure line 4 connected to the suction side of each pressure control unit 2, 3.

On the other hand, a discharge check valve 5b and an intake check valve 5c are provided between the pumps 4a and 5a, and are connected between the valves 5b and 5c and the discharge side of the pressure control units 2 and 3. A low-pressure accumulator (low-pressure storage means) 5d and a line filter 5e are provided to perform storage, and the low-pressure line 5 is constituted by these.

Next, the motors M _{H of} the pumps 4a and 5a,
The driving / stopping of M _L is performed by a pump controller (high-pressure side pump drive control means, low-pressure side pump drive control means) 8. That is, FIG. 3 is a circuit diagram showing the pump controller 8. The pump controller 8 includes a target pressure calculation circuit 8a, a target neutral pressure setting circuit 8b, an adder 8c, a first comparator 8d and a second comparator 8d. It is composed of a comparator 8e.

The target pressure calculation circuit 8a includes a vehicle speed sensor,
Longitudinal acceleration sensor, vertical acceleration sensor, steering angle sensor,
The hydraulic cylinders 1 _FR , 1 _FL , 1 _FL , 1 _FL , 1
1 _RR , 1 _RL (hereinafter, when four cylinders are collectively referred to, the reference numeral is simply 1), the target set pressure P _H0 corresponding to the maximum required hydraulic pressure and the target set pressure P _H0
This is a circuit for calculating the stop target pressure P _H1 which is set slightly higher than _H0 . The range between the two pressures P _H0 and P _H1 is the target pressure range P _T. Incidentally, the target set pressure P _H0 is obtained by adding an external force estimation pressure and a high pressure correction pressure estimated by a signal from the vehicle state detection sensor group 9 on the basis of a predetermined pressure P _V0 near a target neutral pressure P _C described later. The calculation formula is as follows.

P _H0 = P _V0 + K ₁ v + K ₂ | g | + K ₃ |
G | + K ₄ | θ | + ... where K is a coefficient, g is longitudinal acceleration, G is vertical acceleration,
θ is a steering angle.

The high pressure side pressure sensor 6 provided in the high pressure line 4 and the target pressure calculation circuit 8a are connected to the input side of the first comparator 8d. Then, the target set pressure P _H0 and the stop target pressure P _H1 calculated by the target pressure calculation circuit 8a are calculated.
If, by comparing the detected oil pressure p _H of the high-pressure side pressure sensor 6, detects a hydraulic p _{while H} outputs a signal to the ejection drive the high-pressure pump 4a is less than the target set pressure P _H0, detecting hydraulic p _H Is higher than the target stop pressure P _H1, a signal for stopping the discharge drive of the high pressure pump 4a is output.

[0031] The adder 8c is on the input side, the low-pressure side pressure sensor 7 provided in the low-pressure line 5 and the high-pressure side pressure sensor 6 is connected, detects the hydraulic pressure p _H of the two sensors 6 and 7,
p _L is added and a signal indicating the average oil pressure p _{H + L} is output.

The target neutral pressure setting circuit 8b is a circuit for outputting a signal indicating the target neutral pressure P _C set to be slightly higher than the hydraulic pressure with which each cylinder 1 can support the vehicle weight when the vehicle is stopped.

The second comparator 8e compares the average oil pressure p _{H + L} with the target neutral pressure P _C, and the average oil pressure p _{H + L} is a value obtained by subtracting a predetermined pressure K _C from the target neutral pressure P _C. (Hereafter,
If it is less than the neutral lower limit value P _KL ), a signal for driving the low pressure pump 5a to be discharged is output, while the average hydraulic pressure p _{H + L} is a value obtained by adding a predetermined pressure K ′ _C to the target neutral pressure P _C (this). _Is thereafter higher than the neutral upper limit value P _KH ), a signal for stopping the discharge drive of the low pressure pump 5a is output. The neutral lower limit pressure P
The range between _KL and the neutral upper limit value P _KH is the neutral pressure region P _N.

The control operation of the pump controller 8 described above will be described with reference to the flowchart of FIG.

Step 101 is a step of reading signals from the vehicle state detection sensor group 9 and the pressure sensors 6 and 7. Step 102 is a step of calculating the target set pressure P _H0 , the target stop pressure P _H1 and the average oil pressure p _{H + L.} Step 103 is a step of determining whether the detected oil pressure p _H of the high-pressure side is higher than the stop target pressure P _H1, YE
If S, the process proceeds to step 106, and if NO, the process proceeds to step 104. Step 104 is a step of determining whether or not the detected hydraulic pressure p _H on the high pressure side is less than the target set pressure P _H0.
If S, the process proceeds to step 105, and if NO, the process proceeds to step 107. Step 105 is a step of processing the switching SW _H for the high pressure pump to zero. Step 106 is a switching S for the high pressure pump.
This is a step of processing W _H to 1. Step 107
Is a step of determining whether or not the average oil pressure p _{H + L} is higher than the neutral upper limit value P _KH . If YES, the process proceeds to step 110, and if NO, the process proceeds to step 108. Step 108
Is a step of determining whether or not the average oil pressure p _{H + L} is less than the neutral lower limit value P _KL . If YES, the process proceeds to step 109, and if NO, the process proceeds to step 111. Step 109
Is 0 for the switching SW _L for the low pressure pump.
Is the step of processing. Step 110 is a step of processing the switching SW _L for the low pressure pump to 1. Step 111 is a switching SW
_{In the} step of determining whether or not _H is 0, YES is taken to step 112, and NO is taken to step 113. In step 112, the high pressure pump 4a is driven to discharge, that is, the motor M _H is driven. Step 113 is a step of stopping the discharge drive of the high pressure pump 4a, that is, stopping the drive of the motor M _H. Step 114 is a step of determining whether or not the switching SW _L is 0,
If YES, the process proceeds to step 115, and if NO, step 116
Proceed to. Step 115 is the low pressure pump 5a.
Is a driving step for driving the motor M _L , that is, for driving the motor M _L. Step 116 stops the discharge drive of the high pressure pump 5a, that is, the motor M
_This is the step of stopping the driving of _L. Next, the operation of the embodiment will be described. As shown in FIG. 5, the hydraulic pressure required by the hydraulic cylinder 1 may be a value close to a neutral value for both the upper limit hydraulic pressure and the lower limit hydraulic pressure when the external force is small, such as when parking or when going straight on a good road. When the external force is large, such as when turning rapidly at high speed, the upper limit oil pressure increases, while the lower limit oil pressure decreases.

Therefore, when the pump controller 8 determines on the basis of the signal obtained from the vehicle state detection sensor group 9 that the external force hardly acts, such as when traveling on a good road or when the vehicle is stopped, as shown in FIG. Then, the target set pressure P _H0 of the high pressure line 4 is set to be low. Then, the pressure control units 2 and 3 maintain the hydraulic pressures of the four hydraulic cylinders 1 in the front, rear, left, and right at a pressure substantially equivalent to the vehicle weight, and keep the vehicle posture flat.

On the other hand, when an external force such as roll, pitch, or bouncing is applied to the vehicle body by turning, accelerating or decelerating, or traveling on a bad road, the vehicle body tends to lean left, right, front, back, or up and down. In such a case, the pump controller 8
It is determined that the external force is large based on the input signal, and as shown in FIG. 6, the target set pressure P _H0 of the high pressure line 4 is set high. Then, the pressure control units 2 and 3 operate by operating the pressure control valves 2a, 2b, 3a, and 3b so that the hydraulic pressure of the hydraulic cylinder 1 opposes an external force to control the vehicle in a flat posture. Ensure stability.

In such control, an example of control in the case of roll is shown in FIG. That is, in this figure, the horizontal axis represents the amount of displacement of the hydraulic cylinder 1, and the vertical axis represents the external force converted into hydraulic pressure. When a roll occurs, the hydraulic pressure of the outer wheel side hydraulic cylinder 1 is increased to control the hydraulic cylinder 1 to the neutral side, while the hydraulic pressure of the inner wheel side hydraulic cylinder 1 is lowered to control the neutral side.

Next, the control operation of the pump controller 8 will be described in detail. When each pressure control valve 2a, 2b, 3a, 3b is operated in accordance with the control as described above, oil moves from the high pressure line 4 to each cylinder 1 or low pressure line 5, or from each cylinder 1 to the low pressure line. Go to 5. Along with this, the hydraulic pressure in the high-pressure line 4 decreases, while the hydraulic pressure in the low-pressure line 5 increases. Thus detected hydraulic p _H of the high-pressure line 4, drops to less than the target set pressure P _H0 being set in response to an external force at that time, the high pressure pump 4a starts to discharge driven based on the control operation of the pump controller 8 ( (See FIG. 6). As a result, the oil in the low pressure line 5 is returned to the high pressure line 4, and the hydraulic pressure in the high pressure line 4 increases, and at the same time, the hydraulic pressure in the low pressure line 5 decreases. Then, when the detected hydraulic pressure p _H on the high pressure side exceeds the stop target pressure P _H1 , the discharge drive of the high pressure pump 4a is stopped.

Further, in this embodiment, since the high pressure line 4-hydraulic cylinder 1-low pressure line 5 is closed, the hydraulic pressure of the high pressure line 4 rises due to the discharge driving of the high pressure pump 4a. , Low pressure line 5
6, the hydraulic pressure P _L1 of the actual low pressure line 5 increases as the target set pressure P _H0 or the target stop pressure P _H1 increases, as indicated by the dotted line in FIG. _L0 becomes low respectively.

As described above, the hydraulic pressure in the low-pressure line 5 decreases as the high pressure pump 4a is driven. However, when there is no leak in the hydraulic cylinder 1 or the like, the oil in both the lines 4 and 5 and the hydraulic cylinder 1 is reduced. Since there is no change in the total amount of P, the average oil pressure P _{H + L} detected by the pressure sensors 6 and 7 does not fall below the neutral lower limit pressure P _KL . On the other hand, when oil leaks to the reservoir tank T due to a leak in the hydraulic cylinder 1 and the total amount of oil in the lines 4 and 5 and the hydraulic cylinder 1 decreases, the average hydraulic pressure P _{H + L} is the neutral lower limit pressure P _KL. Less than Therefore, the pump controller 8 controls the low pressure pump 5
a is discharged to drive the oil in the reservoir tank T to the low pressure line 5 until the average oil pressure P _{H + L} exceeds the neutral upper limit pressure P _KH.
Will be replenished. By the way, FIG. 9 shows each pump 4a, 5a.
3 shows the drive control characteristics of the.

In this case, the rising and falling speeds of the hydraulic pressure in the lines 4 and 5 and the discharge drive time of the pumps 4a and 5a are determined by the storage capacity of the high pressure accumulator 4c and the low pressure accumulator 5d. The operation time can be shortened by increasing the capacity. By the way, it is possible to replace the conventional pump, front / rear main accumulator, and return accumulator.

Further, the capacity of the low pressure pump 5a is such that a minute leak in the low pressure line 5 (the discharge check valve 5
A low-capacity pump is sufficient because it is used only for replenishment of the leak in (b) and the leak of each cylinder 1) and for oil replenishment during vehicle offline and vehicle repair.

The power consumption when the high pressure pump 4a is discharged is constantly reduced by the amount stored in the low pressure line 5. That is, FIG. 8 shows the pump discharge flow rate Q, the pump discharge pressure, and the power consumption (Q × P).
Is the vertical axis and the external force input (hydraulic cylinder operating frequency) is the horizontal axis for comparison between the conventional and the present embodiment. The solid line represents the conventional pump power consumption (Q _max × P _max + α) Represents the required flow rate Q, the dotted line represents the power consumption [Q × (P _H −P _L ) + α _p ] of the embodiment, and the alternate long and short dash line represents the required upper limit oil pressure P _H and the required lower limit oil pressure P _L. As shown in this figure, the oil pressure corresponding to the required lower limit oil pressure P _L is held in the low pressure line 5, and this oil pressure and the required flow rate Q
From the relationship with, the pump power consumption [Q × (P _H -P _L )
+ Α _p ] is not constant as in the conventional case, but becomes maximum in the intermediate range of the magnitude of the external force.

By the way, when the operating frequency of each hydraulic cylinder 1 becomes extremely high and the capacity of the high pressure pump 4a becomes insufficient, the hydraulic pressures of the high pressure line 4 and the low pressure line 5 become substantially equal, and the hydraulic pressure of the hydraulic cylinder 1 also becomes high. It becomes the same pressure as this. Therefore, in the hydraulic cylinder 1, the hydraulic pressure does not drop below the hydraulic pressure capable of holding the vehicle weight, and even when the operating frequency is extremely high, the hydraulic pressure sharply decreases and the vehicle height decreases or the external force is increased as in the conventional case. There is no anxiety that the amount of change (roll amount, pitch amount) will increase when receiving the force.

Next, a description will be given of long-time parking and abnormal occurrence. Each of the pumps 4a,
When the drive of 5a and the operation of each pressure control unit 2, 3 are stopped, the low pressure line 5 on the discharge side of each pressure control valve 2a, 2b, 3a, 3b is closed by the discharge check valve 5b, so that a leak occurs. Almost none, each hydraulic cylinder 1
Is held at an intermediate pressure (average hydraulic pressure pH _{+ L} ) in both lines 4 and 5. This intermediate pressure is an intermediate pressure sufficient to maintain the vehicle weight based on the capacity ratios of the high pressure accumulator 4c and the low pressure accumulator 5d and the high and low line pressure settings. No operating check valve is required.

Since the hydraulic pressure of the hydraulic cylinder 1 can be set to an intermediate pressure capable of holding the vehicle weight in this way, even if the high pressure pump 4a starts driving when the engine is restarted, each pressure control unit The oil supply / discharge amount by 2 is small, and a sudden posture change does not occur, so that the conventional flow control valve is unnecessary.

As described above, the active suspension of the first embodiment has the effects listed below.

In this embodiment, the pumps 4a and 5a are not always driven to discharge, but are driven to be discharged only when the hydraulic pressure of the high-pressure line 4 drops below the target set pressure P _H0. Is greatly reduced as shown in FIG. 8 to improve fuel economy, and each pump 4
The life of a and 5a also becomes long. Incidentally, conventionally, the pump capacity (flow rate Q) is set to a capacity (Q _max ) that can guarantee the required upper limit oil pressure of the hydraulic cylinder 1, and the power consumption is always the maximum regardless of the operating frequency of the hydraulic cylinder 1. Has become.

Each pump 4a, 5 as described in
Since "a" is not constantly driven, oil does not leak through the relief valve as in the conventional case, and the total flow rate of oil is reduced, which significantly reduces the amount of heat generation. Moreover, the oil circulates in a long path from the high-pressure line 4 to the low-pressure line 5 via the pressure control units 2 and 3 or the hydraulic cylinder 1, so that the heat radiation amount is large. As described above, the oil cooler is unnecessary, or the capacity of the oil cooler can be reduced. By the way, conventionally, as shown in FIG. 5, a large amount of leakage occurs from the relief valve when parking or stopping or traveling on a good road, which occupies about 80% of vehicle traveling, and consumes hydraulic energy as heat generation energy. Cage,
A large capacity oil cooler is required.

Even if the capacities of the pumps 4a and 5a are insufficient, the hydraulic pressure of the hydraulic cylinder 1 does not drop below the average hydraulic pressure p _{H + L of the} lines 4 and 5, so the vehicle weight should be maintained. The height of the vehicle cannot be lowered and the change in posture cannot be suppressed at all. Also, when the vehicle is parked for a long time, or when the operations of both pumps 4a and 5a and both pressure control units 2 and 3 are stopped, such as when an abnormality occurs, the hydraulic pressure of the hydraulic cylinder 1 similarly causes the hydraulic pressure in both lines 4 and 4 to rise. It is possible to prevent the vehicle height from being lowered without being lowered to the atmospheric pressure by being held at the average oil pressure p _{H + L} of 5. And the above action is
It can be obtained without using an expensive fail valve or operate check valve as in the past. That is, with the inexpensive structure, the above-described vehicle height lowering and posture change suppressing effects can be obtained. In addition, since the low pressure pump 5a is for replenishing the leak, it may have a small capacity, but the high pressure pump 4a is also less likely to cause a problem due to insufficient capacity as described above. Can be reduced to reduce weight and cost.

As described above, when parking for a long time,
Since the hydraulic cylinder 1 is maintained at the average hydraulic pressure p _{H + L} of both lines 4 and 5, the engine is restarted and both pumps 4
a and 5a become drivable, and when the hydraulic control of the hydraulic cylinder 1 is started by both pressure control units 2 and 3, the hydraulic pressure of the hydraulic cylinder 1 changes from the average hydraulic pressure p _{H + L.} There is little change in body posture. Therefore, the flow control valve is not necessary, and the cost can be reduced.

Next, other embodiments will be described. In describing these embodiments, the description of the same configurations, functions and effects as those of the first embodiment will be omitted, and only the differences will be described. In the drawings for explaining these other embodiments, the same reference numerals as those in the first embodiment indicate the same components.

FIG. 10 and FIG. 11 are hydraulic system diagrams showing an active suspension of a second embodiment of the present invention. This second embodiment is a high-capacity variable structure in which driving force is constantly input from the engine. In this example, the pressure pump 24a and the low pressure pump 25a are used, and the target pressure range P _T and the neutral pressure range P _N are basically set mechanically.

That is, the high pressure pump 24a
Is a high pressure side pressure sensor (high pressure side pump drive control means) 2 having a piston that operates by receiving the hydraulic pressure of the high pressure line 4.
As shown in FIG. 11, the driving pattern is such that the ejection drive is carried out or stopped in conjunction with No. 6, and the maximum ejection amount is less than the target set pressure P _{H0 and} the range of the target pressure range P _T. The higher the pressure is, the lower the discharge amount becomes, and the target stop pressure P _H0
The discharge amount is zero. That is, in this embodiment, the state in which the ejection amount is greater than 0 is the ejection driving state, and the state in which the ejection amount is 0 is the driving stop state. Further, returning to FIG. 10, the high pressure side pressure sensor 26 is provided with a high pressure pressure correction solenoid 28. The high pressure correction solenoid 28 constitutes a part of the high pressure side pump drive control means, and is driven by a signal corresponding to the external force estimated based on the signal obtained from the vehicle state detection means 9 to set a target. The structure is such that the operation of the high pressure side pressure sensor 26 is corrected so that the pressure P _H0 and the target stop pressure P _H0 change similarly to the first embodiment (see FIG. 6).

On the other hand, the low pressure pump 25a has a first pressure sensor (low pressure side pump drive control means) 27a having a piston which operates by receiving the hydraulic pressure of the high pressure line 4,
The discharge drive is configured to be linked with the resultant force of the output of the second pressure sensor (low-pressure side pump drive control means) 27b having a piston that operates by receiving the hydraulic pressure of the low-pressure line 5, that is, FIG. As shown in FIG.
When the average value of the hydraulic pressure received by 27b is less than the neutral lower limit pressure P _L0 , the discharge drive is performed at the maximum flow rate, and the discharge drive is performed inversely proportional to the hydraulic pressure so that the flow rate decreases as the pressure increases in the neutral pressure range P _N. , And the flow rate is 0 at a pressure higher than the neutral upper limit pressure P _L1 .

In this embodiment, the safety valve 29a releases oil to the low pressure line 5 when the oil pressure in the high pressure line 4 becomes higher than a predetermined value, and the safety valve 29b that releases oil to the reservoir tank T when the oil pressure in the low pressure line 5 becomes higher than the predetermined value. And are provided.

12 and 13 are system diagrams showing an active suspension according to a third embodiment of the present invention. In this embodiment, a high pressure pump 34a and a low pressure pump 35a having a structure with an unload function are provided. This is the example used. That is, the unload valves 36 and 37 are provided on the discharge side of the pumps 34a and 35a. The unload valves 36 and 37 have a structure for connecting and disconnecting the discharge side and the suction side of the pumps 34a and 35a in accordance with the hydraulic pressures of the lines 4 and 5, respectively. The pumps 34a and 35a are shown in FIG.
Drive as shown in 2. By the way, in the present embodiment, the state of the discharge amount of 0 is a state in which there is no hydraulic pressure difference between the suction side and the discharge side even when the pumps 34a and 35a are driven, and in this state, the discharge drive is performed. However, it is assumed that the ejection drive is stopped.

The unload valve 36 receives the hydraulic pressure of the high pressure line 4 in the valve opening direction, and the suction force of the high pressure correction solenoid 28 in the valve closing direction.
As a result, the target pressure range P _T changes as in the first embodiment.

On the other hand, the unload valve 37 is structured so as to receive the resultant force of the hydraulic pressures of the lines 4 and 5 in the valve opening direction, whereby the same operation as in the first embodiment is performed.

Although the embodiment has been described above, the specific structure is not limited to this embodiment, and the present invention includes a design change and the like without departing from the scope of the invention.

[0062]

As described above, in the active suspension according to the present invention described in each claim, the low pressure storage mechanism for storing the discharge fluid of the control valve is provided, and the high pressure side pump operates the low pressure storage mechanism. High-pressure side pump drive control means for sucking fluid and discharging it to the high-pressure storage mechanism, and when the fluid pressure of the high-pressure storage mechanism drops below a target set pressure, discharge-drives the high-pressure side pump until it exceeds the stop target pressure. In addition, a low-pressure side pump that discharges the working fluid is provided in the low-pressure storage mechanism, and if the average value of the fluid pressure of both storage mechanisms is less than the neutral lower limit pressure, the low-pressure side pump is driven to discharge, while the average value Since the low pressure side pump drive control means for stopping the discharge drive of the low pressure side pump is provided when the pressure exceeds the neutral upper limit pressure, the following effects can be obtained.

Since the high-pressure side pump discharges the working fluid of the low-pressure storage mechanism to the high-pressure storage mechanism, the width of pressurization is smaller than when pressurized from the atmospheric pressure, and the energy consumption is reduced as compared with the prior art. It is possible to improve fuel efficiency and durability of the high pressure side pump.

When the operation of the high-pressure side pump or the control valve is stopped during parking for a long time or when an abnormality occurs, the fluid pressure of the fluid actuator can be maintained at an intermediate pressure between the high-pressure storage mechanism and the low-pressure storage mechanism, which is expensive. The vehicle height can be prevented from lowering and the posture change can be suppressed at low cost without using a special fail valve or an operation check valve.

Even if the capacity of the high-pressure side pump is insufficient, the fluid pressure of the fluid actuator does not drop significantly, and problems due to insufficient capacity are less likely to occur. Therefore, the capacity of the high-pressure side pump is reduced to reduce weight and cost. Is possible. In addition, since the fluid actuator is held at the intermediate pressure between both storage mechanisms during long-term parking, it is possible to prevent sudden changes in vehicle body posture when the engine is restarted without using an expensive flow control valve. The cost can be reduced.

Even if there is a fluid leak from the fluid actuator or the like, the working fluid can be appropriately replenished as needed at any time.

The low-pressure side pump can be used when the working fluid is supplied to each storage mechanism or fluid actuator when the vehicle is offline or when the vehicle is repaired.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to claims showing an active suspension of the present invention.

FIG. 2 is a hydraulic system diagram showing an active suspension of the first embodiment.

FIG. 3 is a circuit diagram showing a configuration of a pump controller of the first embodiment.

FIG. 4 is a flowchart showing a control flow of the pump controller of the first embodiment.

FIG. 5 is a hydraulic characteristic diagram showing a necessary upper limit hydraulic pressure and a lower limit hydraulic pressure when an external force is input.

FIG. 6 is a characteristic diagram showing drive / drive stop characteristics of each pump of the first embodiment.

FIG. 7 is an explanatory diagram showing an operation example during rolling of the first embodiment.

FIG. 8 is an operation characteristic diagram showing a required flow rate, power consumption, etc. of the high pressure pump in the first embodiment.

FIG. 9 is a characteristic diagram showing drive characteristics of each pump of the first embodiment.

FIG. 10 is a hydraulic system diagram showing an active suspension of a second embodiment.

FIG. 11 is a characteristic diagram showing a feedback drive characteristic of each pump of the second embodiment.

FIG. 12 is a hydraulic system diagram showing an active suspension of a third embodiment.

FIG. 13 is a characteristic diagram showing a feedback drive characteristic of each pump of the third embodiment.

[Explanation of symbols]

 a fluid actuator b high-pressure side pump c high-pressure storage means d check valve e high-pressure storage mechanism f control valve g attitude control means h low-pressure storage means j check valve k low-pressure storage mechanism n high-pressure side pump drive control means p low-pressure side pump r low-pressure side Pump drive control means

Claims (1)

[Claims] 1. A fluid actuator, which is interposed between a vehicle body and each wheel, and is capable of changing the distance between the two, and a high-pressure storage for storing a discharge working fluid supplied from a high-pressure side pump to the fluid actuator at a high pressure. Means and a high pressure storage mechanism having a check valve for preventing backflow from the high pressure storage means to the high pressure side pump, and a working fluid supply amount to each fluid actuator interposed between the high pressure storage mechanism and the fluid actuator. And a control valve that individually controls the amount of working fluid discharged from each fluid actuator, an attitude control unit that controls the operation of this control valve based on an input relating to a change in the attitude of the vehicle body, and a fluid pressure of the high-pressure storage mechanism, A target that is set according to the input relating to the posture of the vehicle body at that time and that is a pressure range above the maximum fluid pressure required by the fluid actuator at that time The fluid pressure of the high pressure storage mechanism is detected in order to control the high pressure side region, and if the detected pressure is less than the target set pressure which is the lower limit pressure of the target pressure range, the high pressure side pump is driven to discharge while the detected pressure is the target pressure. High-pressure side pump drive control means for stopping the discharge drive of the high-pressure side pump when the stop target pressure which is the upper limit pressure of the region is exceeded, and a suction side of the high-pressure side pump, a discharge side of the control valve and a pressure lower than the high-pressure side pump. Connected to the discharge side of the low-pressure side pump having a discharge pressure of, a low-pressure storage means for storing the working fluid at a predetermined pressure lower than the high-pressure storage means, and a backflow from the low-pressure storage means to the low-pressure side pump are prevented. A low pressure storage mechanism having a check valve, and an average value of the fluid pressure of the low pressure storage mechanism and the fluid pressure of the high pressure storage mechanism is detected, and the pressure range is equal to or higher than the fluid pressure capable of supporting the average value and the vehicle weight. Preset If the average value is less than the neutral lower limit pressure which is the lower limit value of the neutral pressure region, the low pressure side pump is driven to discharge, while the average value is the upper limit pressure of the neutral pressure region. An active suspension comprising: a low-pressure side pump drive control means for stopping discharge drive of the low-pressure side pump when the neutral upper limit pressure is exceeded.