JPH06320930A - Fluid pressure active suspension - Google Patents

Abstract

PURPOSE:To make the smooth running off a vehicle possible by preventing the abrupt fluctuation of engine load even in a case where target pressure in an actuator, repeats its abrupt increase and decrease. CONSTITUTION:A hydraulic active suspension has an actuator 26 having a working fluid chamber 28; a pump 18 driven by an engine 16; working fluid supply passages 20,32 to connect the pump 18 to the working fluid chamber 28; working fluid discharge passages 32, 14; a target pressure operation unit 60 to compute target pressure in the working fluid chamber according to the running state of a vehicle; a servo valve 22 to control the supply and discharge of the working fluid according to the target pressure; and a supply pressure controllers 58, 60 to control the pressure in the supply passage 20 according to the target pressure. The supply pressure controller regulates the decrease rate of pressure to be above a fixed value in reducing the pressure in the supply passage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension of a vehicle such as an automobile, and more particularly to a fluid pressure type active suspension.

[0002]

2. Description of the Related Art As one of fluid pressure type active suspensions for vehicles such as automobiles, for example, Japanese Unexamined Patent Publication No. 4-151 is known.
As described in Japanese Patent No. 317, an actuator that is provided corresponding to each wheel and that increases or decreases the vehicle height of a corresponding portion by supplying and discharging the working fluid to and from the working fluid chamber,
A working fluid supply source including a pump driven by an engine, a working fluid supply passage that connects and connects the working fluid supply source and the working fluid chamber, a working fluid discharge passage that communicates with the working fluid chamber at one end, and Target pressure calculation means for calculating a target pressure in the working fluid chamber according to the running state, and control of supply and discharge of the working fluid to and from the working fluid chamber according to the target pressure, provided in the middle of the working fluid supply passage and the working fluid discharge passage Control valve, a line pressure regulating valve for selectively connecting a portion of the working fluid supply passage upstream of the control valve and a portion of the working fluid discharge passage downstream of the control valve, and controlling the line pressure regulating valve A hydraulic active suspension having line pressure control means for controlling the pressure (line pressure) in the working fluid supply passage upstream of the control valve according to the target pressure is already known. There.

According to such an active suspension, by controlling the line pressure regulating valve, the line pressure, that is, the pressure in the working fluid supply passage on the upstream side of the control valve is accurately adjusted to the pressure actually consumed in the actuator. Since it is adjusted to the minimum required value corresponding to, the loss of horsepower consumed by the pump can be reduced, the load on the engine can be reduced, and the fuel consumption can be improved.

[0004]

However, in the conventional active suspension as described above, when the target pressure relatively rapidly increases and decreases, such as when the vehicle travels in slalom or on a winding road, a pump is used. There is a problem that the load of the vehicle repeatedly increases and decreases relatively rapidly, and thus the load of the engine also repeatedly increases and decreases relatively rapidly, and thus the vehicle cannot travel smoothly.

In view of the above problems in the conventional fluid pressure type active suspension, the present invention does not drastically change the load of the engine even when the vehicle travels in slalom or on a winding road. The object of the present invention is to provide an improved fluid pressure type active suspension so that the vehicle can travel smoothly.

[0006]

SUMMARY OF THE INVENTION According to the present invention, the above-described object is to increase the vehicle height of the corresponding portion by supplying and discharging the working fluid to and from the working fluid chamber provided corresponding to each wheel. An actuator that increases or decreases, a working fluid supply source including a pump driven by an engine, a working fluid supply passage that connects the working fluid supply source and the working fluid chamber to each other, and one end that communicates with the working fluid chamber. A working fluid discharge passage, a target pressure calculating means for calculating a target pressure in the working fluid chamber according to a traveling state of the vehicle, and a working pressure supply means provided in the middle of the working fluid supply passage and the working fluid discharge passage, depending on the target pressure. Supply / discharge control means for controlling the supply / discharge of the working fluid to / from the working fluid chamber, and a supply pressure for controlling the pressure in the working fluid supply passage upstream of the supply / discharge control means according to the target pressure. And control means, said supply pressure control means is achieved by hydraulic active suspension configured to regulate the rate of decrease of pressure above a predetermined value when the reducing the pressure of the working fluid supply passage.

[0007]

According to the above-mentioned structure, the supply pressure control means for controlling the pressure in the working fluid supply passage upstream of the supply / discharge control means in accordance with the target pressure in the working fluid chamber is the pressure in the working fluid supply passage. When the target pressure is sharply reduced, the pressure in the working fluid supply passage is not sharply reduced because the pressure reduction rate is regulated to a predetermined value or more. The load of the pump does not change rapidly even when the target pressure repeatedly increases and decreases relatively rapidly, such as when traveling in slalom or winding roads, which reduces the change in engine load as compared to the past. This allows the vehicle to run smoothly.

According to the second aspect of the present invention, the pressure in the working fluid supply passage is detected by the supply pressure detecting means, and, for example, an abnormality such as a working fluid leak from the working fluid supply passage or a sudden increase in the target pressure. When the pressure in the working fluid supply passage becomes lower than the target pressure due to the rise, the supply / discharge stopping means stops the supply / discharge of the working fluid to / from the working fluid chamber by the supply / discharge control means. Since the pressure is lower than the pressure in the fluid chamber, it is possible to reliably prevent the working fluid in the working fluid chamber from flowing back to the working fluid supply passage via the supply / discharge control means and the resulting disturbance of the posture of the vehicle body. become.

[0009]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram showing a fluid circuit of one embodiment of a fluid pressure type active suspension according to the present invention, and FIG. 2 is a block diagram showing an electronic control unit for controlling the servo valve and the like shown in FIG. Is.

In FIG. 1, reference numeral 10 indicates a reservoir for storing oil as a working fluid. One end of the connection passage 12 and one end of the working fluid discharge passage 14 are connected to the reservoir 10. The other end of the connection passage 12 is connected to the suction side of a constant volume pump 18 driven by the engine 16. The working fluid supply passage 2 is provided on the discharge side of the pump 18.
One end of 0 is connected. The other end of the working fluid supply passage 20 and the other end of the working fluid discharge passage 14 are connected to the P port and the R port of a 3-port / 3-position switching type servo valve 22, respectively. In the middle of each working fluid discharge passage 14, a communication connection portion 14 with a working fluid discharge passage from another wheel is provided.
A check valve 24 is provided closer to the servo valve 22 than a. The check valve allows only the flow of the working fluid from the servo valve 22 toward the reservoir 10.

The A port of the servo valve 22 is connected at one end thereof to the working fluid chamber 28 of the actuator 26, and the other end of a connection passage 32 having a shutoff valve 30 in the middle thereof. The servo valve 22 connects a switching position 22a that cuts off the communication of all ports, a switching position 22b that connects and connects the ports P and A, and a port R and a port A by a control signal supplied to the solenoid 24. It is switched to the switching position 22c which is connected for communication, whereby the supply / discharge of the working fluid to / from the working fluid chamber 28 is controlled.

As shown in the figure, the actuator 26 is a kind of cylinder piston device, and is arranged between the suspension member supporting the wheels and the vehicle body, though not shown in the figure, and the working fluid is supplied to the working fluid chamber 28. The vehicle height of the corresponding portion is increased or decreased by being supplied or discharged. The gas-liquid spring device 3 is provided in the working fluid chamber 28 by the passage 34.
6 is connected, and a diaphragm 38 is provided in the middle of the passage 34. Thus, the gas-liquid spring device 36 acts as a suspension spring or an auxiliary suspension spring, and the throttle 38 produces a damping force.

The shutoff valve 30 is a pilot pressure control device 40.
The pilot pressure Pc controlled by is taken in, and when the pilot pressure Pc exceeds a predetermined valve opening value, the valve is opened, and when the pilot pressure is below a predetermined valve closing value, the valve is closed. The pilot pressure control device 40 includes a connection passage 42 that connects the working fluid supply passage 20 and the reservoir 10 to each other.
And a fixed throttle 44 and a variable throttle 46 provided in the middle of the passage, and the pressure between the fixed throttle and the variable throttle is supplied to the shutoff valve 30 as a pilot pressure Pc.

A check valve 50 which allows only the flow of the working fluid from the filter 48 and the pump 18 toward the servo valve 22 is provided in the middle of the working fluid supply passage 20. In addition, the working fluid supply passage 20 on the downstream side of the check valve 50 has an accumulator 52 for accumulating the working fluid in the passage.
Are connected in communication with each other, and a pressure sensor 54 for detecting the pressure (line pressure) Ps of the working fluid in the supply passage 20 is provided.

In the illustrated embodiment, the working fluid supply passage 20 downstream of the check valve 50 and the working fluid discharge passage 14 downstream of the check valve 24 are connected to each other by a relief passage 56. A relief valve 58 is provided in the relief passage 56. The relief valve 58 is a solenoid valve that takes in the pressure in the relief passage 56 on the upstream side as a pilot pressure.
The valve opening amount is increased / decreased and the valve opening amount is increased / decreased by the control signal supplied to 8a, whereby the pressure in the working fluid supply passage 20 and the accumulator 52, that is, the line pressure Ps can be increased / decreased.

The servo valve 22, the check valve 24, the actuator 26, the shutoff valve 30, the connection passage 32, and the gas-liquid spring device 3 are provided.
6, the diaphragm 38, etc. are provided corresponding to each wheel. Further, in FIG. 2, the servo valves corresponding to the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel are 22fr, 22fl, 22rr, and 22 respectively.
It is indicated by rl.

Servo valve 22, pilot pressure controller 4
0 and the relief valve 58 are adapted to be controlled by an electronic control unit 60 shown in detail in FIG. The electric control device 60 includes a microcomputer 62.
The microcomputer 62 may be of a general configuration as shown in FIG. 2 and may include a central processing unit (C
PU) 64, read only memory (ROM) 66,
It has a random access memory (RAM) 68, an input port device 70, and an output port device 72, which are connected to each other by a bidirectional common bus 74.

The input port device 70 includes a pressure sensor 54.
A signal indicating the pressure Ps in the supply passage 20, a signal indicating the lateral acceleration of the vehicle body from a lateral acceleration sensor 76 not shown in FIG. 1, a signal indicating the longitudinal acceleration of the vehicle body from the longitudinal acceleration sensor 78, and a signal from the shift sensor 80. A signal indicating a shift position of a shift lever of an automatic transmission, a signal indicating a vehicle speed from a vehicle speed sensor 82, a signal indicating a steering angle from a steering angle sensor 84 are input, and a group of sensors 86 such as a vehicle height sensor inputs the other signals of the vehicle. A signal related to the running state is input.

The input port device 70 appropriately processes a signal input thereto, and in accordance with an instruction of the CPU 64 based on a program stored in the ROM 66, a CPU and a RAM.
The processed signal is output to 68. R
The OM 66 stores the control program shown in FIG. The CPU 64 is adapted to perform various calculations and signal processing as described later based on the flowchart shown in FIG. The output port device 72 follows the instructions of the CPU 64 and passes through the drive circuits 88 to 94 to the servo valves 22fr and 22r.
A control signal is output to the corresponding variable throttle of l, 22rr, and 22rl, and the pilot pressure control device 40 is driven through the drive circuit 96.
The control signal is output to the variable throttle 44 of FIG. 1, and the control signal is output to the relief valve 58 via the drive circuit 98.

The control by the control unit 60 is started by closing an ignition switch (not shown),
It will be finished shortly after the ignition switch is opened. At the start of operation of the active suspension, the pilot pressure control device 40 is controlled prior to step 10 to gradually increase the pilot pressure Pc, whereby the shut-off valve 30 is gradually opened until it is fully opened. If necessary, the details of such control are described in, for example, Japanese Patent Application No. 2-1
See 99883.

First, in step 10, the pressure sensor 54
A signal indicating the line pressure Ps detected by the lateral acceleration sensor 76, a signal indicating the lateral acceleration of the vehicle body detected by the lateral acceleration sensor 76,
A signal indicating the longitudinal acceleration of the vehicle body detected by the longitudinal acceleration sensor 78, a signal indicating the shift position of the shift lever of the automatic transmission detected by the shift sensor 80, a signal indicating the vehicle speed detected by the vehicle speed sensor 82, and a steering angle sensor A signal indicating the steering angle detected by 84 is input, and a signal regarding another running state of the vehicle detected by a group of sensors 86 such as a vehicle height sensor is read, and then the process proceeds to step 20.

In step 20, the working fluid chamber 28 of each actuator 26 for controlling the posture of the vehicle body and the riding comfort of the vehicle based on the signal read in step 10.
The target pressure Pai (i = fr, rl, rr, rl) within is calculated,
In step 30, the maximum value Pmax of the target pressures Pai calculated in step 20 is selected. The calculation of the target pressure in step 20 does not form the subject of the present invention, and any calculation can be performed as long as it is calculated according to the running state of the vehicle so that the posture of the vehicle body and the riding comfort of the vehicle are controlled well. Aspects may be implemented.

In step 40, the maximum value P of the target pressure is set.
A target value Psa of the line pressure Ps is calculated by adding a margin α (a positive constant) to max. If it is determined that Psa ≧ Ps, the line pressure command value P is determined in step 60.
When c is set to the target value Psa, the count value T1 of the timer is reset to 0, and when it is determined that Psa ≧ Ps is not satisfied, the count value T1 of the timer is ΔT1 (a positive constant) in step 70. ) Is incremented.

In step 80, it is judged whether or not the count value T1 of the timer is greater than or equal to the reference value T1c (a positive constant), and if it is judged that T1 ≥ T1c is not satisfied, the line pressure is determined. When the command value Pc of is held at the previous value, the process proceeds to step 100, and when it is determined that T1 ≥ T1c, the command value Ps is Δ at step 90.
After P (a positive constant) is decremented, the process proceeds to step 100.

At step 100, the control signal is output to the relief valve 58 to control the line pressure Ps to the command value Pc, and at step 110, the line pressure Ps.
Is the maximum value Pma of the target pressure selected in step 30.
It is determined whether or not x is less than or equal to x, that is, whether or not the working fluid in the working fluid chamber is in the reverse flow to the supply passage 20 when the servo valve 22 is switched to the switching position 22b, and Ps ≤ When it is determined that the value is Pmax, the count value T2 of the timer is ΔT2 in step 120.
(Positive constant) After being incremented, the routine proceeds to step 150, and when it is determined that Ps ≤ Pmax is not established, the count value T2 of the timer is reset to 0 at step 130 and then the routine proceeds to step 140.

In step 140, the target current supplied to each servo valve 22 is calculated based on the target pressure Pai calculated in step 20, and each servo valve is controlled by the target current. , The pressure in the working fluid chamber of each actuator is controlled to the target pressure calculated in step 20, whereby active control such as attitude control of the vehicle body and ride comfort control of the vehicle is executed, and then the process returns to step 10. .

In step 150, it is judged whether or not the count value T2 of the timer is equal to or greater than the reference value T2c,
When it is determined that T2 ≥ T2c is not satisfied, in step 160, a command signal for controlling the vehicle height of the portion corresponding to each servo valve to the standard vehicle height is output, and then the process returns to step 10. When it is determined that T2 ≧ T2c, the variable throttle 44 of the pilot pressure control device 40 is used.
The control signal is output to the pilot pressure P
c is reduced, which causes the shutoff valve 30 to close, and FIG.
The control according to the flowchart shown in FIG.

Thus, according to the illustrated embodiment, in step 20, each actuator 26 is based on the running state of the vehicle.
The target pressure Pai in the working fluid chamber 28 is calculated, the maximum value Tmax of the target pressure is selected in step 30, and the target value Psa of the line pressure is calculated in step 40. When it is determined in step 50 that the target value Psa of the line pressure is equal to or greater than the actual line pressure Ps, the command value Pc is updated to the target value Psa in step 60,
When it is determined that the target value Psa of the line pressure is less than the actual line pressure Ps, the command value Pc is gradually reduced after a predetermined time elapses in steps 70 to 90, and the line pressure Ps in step 100. Is controlled to the command value Pc.

Therefore, when the maximum value Pmax of the target pressure increases, the line pressure Ps increases in accordance with the increase, and when the maximum value of the target pressure decreases, the rate of decrease of the line pressure Ps is restricted to a predetermined value. Therefore, it is possible to prevent the load on the pump 18 and the engine 16 from being suddenly reduced due to the rapid decrease in the line pressure, thereby ensuring smooth running of the vehicle.

For example, when the maximum value Pmax of the target pressure fluctuates as shown by the broken line in FIGS. 4 and 5 by traveling in slalom, the line pressure Ps is controlled to increase or decrease according to the maximum value Pmax of the target pressure. In the conventional active suspension described above, the line pressure Ps repeatedly changes relatively rapidly as shown by the phantom line in FIG. 5, which causes the pump and engine loads to repeat relatively rapidly. It fluctuates.

On the other hand, according to the illustrated embodiment, since the command value Pc of the line pressure is gradually reduced when the maximum value Pmax of the target pressure is reduced, the line pressure Ps is shown by a solid line in FIG. As described above, the reduction rate of the line pressure Ps is reduced as compared with the case of the conventional active suspension, so that the variation becomes gentle, and thus the variation rate of the load of the pump and the engine can be reduced. it can.

Also according to the illustrated embodiment, step 11
At 0, it is judged whether or not the line pressure Ps is less than or equal to the maximum value Pmax of the target pressure, and the line pressure Ps is maximum value Pma.
When x is less than or equal to x, the active control is not performed, so that it is possible to reliably prevent the disturbance of the vehicle body posture due to the backflow of the working fluid in the working fluid chamber to the working fluid supply passage 20 through the servo valve.

Further according to the illustrated embodiment, the line pressure Ps
Even if it is determined that is equal to or less than the maximum value Pmax, the shut-off valve 30 is not closed unless the determination is continued for a predetermined time or longer. Therefore, the positive determination in step 110 indicates, for example, noise of the pressure sensor. It is possible to reliably prevent the shutoff valve 30 from being closed and the active control being stopped despite the temporary detection abnormality resulting from the above.

In the above embodiment, steps 70 to 90 are executed whenever the negative determination is made in step 50. However, the negative determination is made in step 50. deviation ΔP between the target value Psa _nk target value Psa _n and k cycle before the line pressure of the current line pressure when the
Sa may be calculated, and when the deviation ΔPsa is greater than or equal to the reference value Pse (negative constant), the process may proceed to step 60, and when the deviation ΔPsa is less than the reference value Pse, the process may proceed to step 70.

Further, in the above embodiment, the pump 18 is a constant volume type pump, but this pump may be a variable displacement type pump, in which case the target value Psa of the line pressure is In the process of decreasing, the relief valve 58 may be opened and the discharge flow rate of the pump may be decreased.

Further, in the above-mentioned embodiment, the control valve for controlling the supply / discharge of the working fluid to / from the working fluid chamber of each actuator is a flow control valve, but this control valve may be a pressure control valve. .

Although the present invention has been described above in detail with reference to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments are also possible within the scope of the present invention. It will be apparent to those skilled in the art that it is possible.

[0039]

As is apparent from the above description, according to the above-described structure of claim 1 of the present invention, the supply pressure control means determines the pressure reduction rate when the pressure in the working fluid supply passage is reduced. Since it is designed to regulate above the value,
Even when the target pressure in the working fluid chamber drops sharply, the pressure in the working fluid supply passage does not drop sharply, so the target pressure is relatively sharp, as when the vehicle is running on slalom or winding roads. Even if the pump load is repeatedly increased and decreased, the load of the pump does not fluctuate abruptly, so that the fluctuation of the load of the engine can be reduced and the vehicle can run smoothly compared to the conventional case.

According to the second aspect of the present invention described above, the pressure in the working fluid supply passage is equal to or lower than the target pressure due to an abnormality such as a working fluid leak from the working fluid supply passage or a rapid increase in the target pressure. Then, since the supply / discharge control means stops the supply / discharge of the working fluid to / from the working fluid chamber by the supply / discharge control means, the pressure in the working fluid supply passage is lower than the pressure in the working fluid chamber. It is possible to reliably prevent the working fluid from flowing back to the working fluid supply passage through the supply / discharge control means and the resulting disturbance of the posture of the vehicle body.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a fluid circuit of one embodiment of a fluid pressure type active suspension according to the present invention.

FIG. 2 is a block diagram showing an electronic control device for controlling a servo valve and the like.

FIG. 3 is a flowchart showing a control routine achieved by the electronic control device shown in FIG.

FIG. 4 is a time chart showing an example of changes in a maximum target pressure Pmax and a line pressure Ps when the vehicle travels in a slalom manner in the illustrated embodiment.

FIG. 5 is a maximum value Pma of the target pressure when the vehicle travels in slalom with the conventional active suspension.
6 is a time chart showing an example of changes in x and line pressure Ps.

[Explanation of symbols]

 10 ... Reservoir 16 ... Engine 18 ... Pump 20 ... Working fluid supply passage 22 ... Servo valve 26 ... Actuator 28 ... Working fluid chamber 30 ... Shutoff valve 32 ... Connection passage 36 ... Gas-liquid spring device 38 ... Throttle 40 ... Pilot pressure control device 52 ... Accumulator 58 ... Relief valve 60 ... Electronic control unit 62 ... Microcomputer

Claims (2)

[Claims] 1. A working fluid supply including an actuator which is provided corresponding to each wheel and which increases and decreases the vehicle height of a corresponding portion by supplying and discharging the working fluid to and from a working fluid chamber, and a pump driven by an engine. Source, a working fluid supply passage that connects and connects the working fluid supply source and the working fluid chamber, a working fluid discharge passage that communicates with the working fluid chamber at one end, and the working fluid according to a running state of the vehicle. Target pressure calculating means for calculating a target pressure in the chamber, and supply / discharge for controlling the supply / discharge of the working fluid to / from the working fluid chamber according to the target pressure, provided in the middle of the working fluid supply passage and the working fluid discharge passage. And a supply pressure control means for controlling the pressure in the working fluid supply passage on the upstream side of the supply / discharge control means according to the target pressure. Hydraulic active suspension configured to regulate the rate of decrease of pressure above a predetermined value when the reducing pressure of the body supply passage. 2. The fluid pressure type active suspension according to claim 1, wherein the supply pressure detecting means for detecting the pressure in the working fluid supply passage and the pressure in the working fluid supply passage are equal to or less than the target pressure. A fluid pressure type active suspension, which sometimes has a supply / discharge stopping means for stopping the supply / discharge of the working fluid to / from the working fluid chamber by the supply / discharge control means.