JPH07102769B2 - Fluid pressure active suspension - Google Patents

Description

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

2. Description of the Related Art As one of active suspensions for vehicles such as automobiles, a fluid pressure actuator disposed between each wheel and a vehicle body, a working fluid supply / discharge means for supplying / discharging a working fluid to / from each actuator, and a vehicle Conventionally, there has been known a fluid pressure type active suspension including a control means for controlling the working fluid supply / discharge means in accordance with the traveling state.

In such a fluid pressure type active suspension, in order to effectively prevent roll of the vehicle body during turning of the vehicle without response delay, for example, it is described in JP-A-62-299418 and JP-A-63-279915. As described above, the lateral acceleration of the vehicle body is estimated based on the vehicle speed and the steering angle, or the rate of change of the lateral acceleration of the vehicle body is estimated based on the vehicle speed and the steering angular velocity, and the operation is performed based on the estimated lateral acceleration or the rate of change thereof. It has already been proposed to control the fluid supply / drainage means.

However, when a vehicle turns on a road surface having a low coefficient of friction such as an icy road surface, the turning lateral force of the wheels is greater than that when the vehicle turns on a normal road surface. , The estimated lateral acceleration of the vehicle body becomes larger than the actual lateral acceleration,
The rate of change of the estimated lateral acceleration also becomes larger than the rate of change of the actual lateral acceleration, and as a result, the control of the supply and discharge of the working fluid to the actuator based on the estimated lateral acceleration and the rate of change becomes excessive, which causes the vehicle body to move with steering. May cause unpleasant rolls or reverse rolls. Further, there is a problem that the supply / discharge flow rate of the working fluid to / from the actuator increases due to the excessive control, and the energy consumption increases.

Further, in order to solve such a problem, when the vehicle turns while traveling on a road surface having a low friction coefficient, it may be considered to stop the supply / discharge of the working fluid to / from the actuator. In that case, the actual acceleration of the vehicle body ( There is a problem in that the roll of the vehicle body due to the centrifugal force) cannot be suppressed at all, so that the steering stability is deteriorated when the vehicle turns on a road surface having a low friction coefficient.

In view of the above-mentioned problems in the conventional active suspension configured to control the supply and discharge of the working fluid to the actuator based on the estimated lateral acceleration or the rate of change of the estimated lateral acceleration, the present invention provides a vehicle with a friction coefficient of Even when turning while traveling on a small road surface, it is possible to suppress rolls of the vehicle body as effectively as possible while preventing unpleasant rolls and reverse rolls, and avoid excessive consumption of working fluid. It is an object to provide an improved hydraulic active suspension.

According to the present invention, a fluid pressure actuator disposed between each wheel and a vehicle body and a working fluid supply / discharge system for supplying / discharging a working fluid to / from the actuator are provided. Means and
A means for obtaining a friction coefficient of a road surface, a means for detecting an acceleration of the vehicle body, a means for detecting a vehicle speed, a means for obtaining a steering angle or a steering angular velocity, a first control amount and a vehicle speed based on the acceleration of the vehicle body, A control means for controlling the working fluid supply / discharge means according to a steering angle or a vehicle speed and a second control quantity based on the steering angular speed, the control means depending on the friction coefficient of the road surface. Is achieved by a fluid pressure type active suspension configured to reduce the second controlled variable as the road surface friction coefficient decreases without changing substantially.

Effects of the Invention According to the above-described configuration, the supply and discharge of the working fluid to and from the fluid pressure actuator are performed by the first control amount based on the acceleration of the vehicle body and the second control amount based on the vehicle speed and the steering angle or the vehicle speed and the steering angular velocity. When the vehicle is turning, the pressure inside the turning outer wheel side actuator is increased and, conversely, the pressure inside the turning inner wheel side actuator is reduced, so that the vehicle is running on a road surface with a high friction coefficient. When the vehicle turns, the roll of the vehicle body is effectively suppressed without a response delay.

Further, the turning lateral force of the wheel when turning the vehicle becomes smaller as the friction coefficient of the road surface is lower, and the actual acceleration of the vehicle body changes according to the friction coefficient of the road surface. The first control amount does not become excessive even if the friction coefficient of the road surface decreases, but the second control amount based on the vehicle speed and the steering angle or the vehicle speed and the steering angular velocity, that is, the control amount based on the predicted lateral acceleration is the road surface. The lower the coefficient of friction of, the more excess. According to the present invention, the control means does not substantially change the first control amount depending on the friction coefficient of the road surface, and the lower the friction coefficient of the road surface, the second speed based on the vehicle speed and the steering angle or the vehicle speed and the steering angular speed. Since the control amount is reduced, even when the vehicle turns while traveling on a road surface having a small coefficient of friction, an unpleasant roll of the vehicle body caused by excessive control of supply and discharge of the working fluid to the actuator And the reverse roll are prevented, the roll of the vehicle body is effectively suppressed based on the actual acceleration of the vehicle body, and the consumption amount of the working fluid of the amount corresponding to the reduction amount of the second control amount is reduced.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Embodiment 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.
The fluid circuits of the active suspension shown in the figure are actuators 1FR, 1FR provided corresponding to the right front wheel, left front wheel, right rear wheel and left rear wheel of the vehicle, which are not shown in the figure, respectively.
FL, 1RR, 1RL, and these actuators have working fluid chambers 2FR, 2FL, 2RR, 2RL, respectively.

Further, in the figure, reference numeral 4 denotes a reserve tank for storing hydraulic oil as a working fluid, and the reserve tank 4 has a suction passage 10 provided with a filter 8 for removing foreign matter on the suction side of the pump 6 from the suction side. It is connected with. Pump 6
The working fluid leaking inside is stored in the reserve tank 4
The drain flow path 12 for collecting is connected to. The pump 6 is rotationally driven by the engine 14, and the rotational speed of the engine 14 is detected by the rotational speed sensor 16.

A high pressure flow path 18 is connected to the discharge side of the pump 6. A check valve 20 which allows only the flow of the working fluid from the pump to each actuator is provided in the middle of the high-pressure flow path 18, and the working fluid discharged from the pump is provided between the pump 6 and the check valve 20. An attenuator 22 is provided which absorbs the pressure pulsation and reduces the pressure change. One end of the front wheel high pressure flow path 18F and the rear wheel high pressure flow path 18R is connected to the high pressure flow path 18, and accumulators 24 and 26 are connected to these high pressure flow paths, respectively. Each of these accumulators is filled with a high-pressure gas to absorb the pressure pulsation of the working fluid and to accumulate the pressure. The high-pressure flow passages 18F and 18R have a high-pressure flow passage 18FR for the right front wheel, a high-pressure flow passage 18FL for the left front wheel, and a high-pressure flow passage for the right rear wheel, respectively.
18RR and one end of the high pressure flow path 18RL for the left rear wheel are connected.
Filters 28FR, 28FL, 28RR, 28RL are provided in the middle of the high pressure flow paths 18FR, 18FL, 18RR, 18RL, and the other ends of these high pressure flow paths are pressure control valves 32, 34, 36, respectively.
38 pitt operated 3 port switching control valves 40, 42,
It is connected to the P ports of 44 and 46.

The pressure control valve 32 includes a switching control valve 40, a flow passage 50 that connects the high pressure flow passage 18FR and the low pressure flow passage 48FR for the right front wheel, and a fixed throttle 52 and a variable throttle 54 provided in the middle of the flow passage. It has become. Low pressure passage 48FR for R port of switching control valve 40
Is connected, and the connection flow path 56 is connected to the A port. The switching control valve 40 is a spool valve that takes in the pressure Pp in the flow passage 50 between the fixed throttle 52 and the variable throttle 54 and the pressure Pa in the connection flow passage 56 as pilot pressure, and the pressure Pp is higher than the pressure Pa. Sometimes it is switched to a switching position 40a that connects and connects the ports P and A, and when the pressures Pp and Pa are equal to each other, it is switched to a switching position 40b that blocks the communication of all ports. When the pressure Pp is lower than the pressure Pa, the ports are switched. It is adapted to switch to a switching position 40c where R and port A are communicatively connected. Further, the variable throttle 54 changes the effective passage cross-sectional area of the throttle by controlling the current supplied to its solenoid 58, and thereby changes the pressure Pp in cooperation with the fixed throttle 52.

Similarly, the pressure control valves 34 to 38 are pilot-operated three-port switching control valves 42, 44, 46 corresponding to the switching control valve 40 of the pressure control valve 32, and the flow channels 60, 62, 62 corresponding to the flow channel 50.
64, fixed diaphragms 66, 68, 70 corresponding to the fixed diaphragm 52, and variable diaphragms 72, 74, 76 corresponding to the variable diaphragm 54. The variable diaphragms 72 to 76 are solenoids 78, 80, 82, respectively. have.

Further, the switching control valves 42, 44, and 46 are configured similarly to the switching control valve 40, and the R ports of the switching control valves 42, 44, and 46 are low-pressure passage 48FL for the left rear wheel, low-pressure passage 48RR for the right rear wheel, and left rear One end of the wheel low-pressure flow path 48RL is connected, and one end of each of the connection flow paths 84, 86, 88 is connected to the A port. The switching control valves 42 to 46 are spool valves that take in the pressure Pp in the flow passages 60 to 64 between the corresponding fixed throttle and the variable throttle and the pressure Pa in the corresponding connecting flow passages 84 to 88 as pilot pressures. And when the pressure Pp is higher than the pressure Pa, the switching positions 42a, 44a, 46 for connecting the port P and the port A in communication.
Switching positions 42b, 44b, 46b that switch to a and shut off communication of all ports when pressures Pp and Pa are equal to each other
, And when the pressure Pp is lower than the pressure Pa, the port R
And switching positions 42c, 44c, 46c that connect the port and port A for communication
It is designed to switch to.

Each actuator, as shown schematically in FIG.
1FR, 1FL, 1RR, 1RL are cylinders 106FR, 106FL,
Working fluid chambers 2FR, 2FL, 2RR, 2 in cooperation with 106RR and 106RL and their corresponding cylinders
It is composed of pistons 108FR, 108FL, 108RR, 108RL that define RL, each connected to a vehicle body not shown in the drawing by a cylinder, and not shown in the drawing by the tip of the rod portion of the piston. It is connected to the suspension arm. Although not shown in the figure, a suspension spring is mounted between the upper seat fixed to the rod portion of the piston and the lower seat fixed to the cylinder.

Cylinder of each actuator 106FR, 106FL, 106R
One ends of drain flow paths 110, 112, 114, and 116 are connected to R and 106RL. The other ends of the drain flow channels 110, 112, 114, 116 are connected to the drain flow channel 118, and the drain flow channel is connected to the reserve tank 4 via the filter 120,
As a result, the working fluid leaking from the working fluid chamber is returned to the reserve tank.

The working fluid chambers 2FR, 2FL, 2RR, 2RL have throttles 124, 1 respectively
Accumulators 132, 134, 136, 1 through 26, 128, 130
38 is connected. Also piston 108FR, 108FL, 108R
Flow paths 140FR, 140FL, 140RR, 140RL for R and 108RL, respectively.
Is provided. These flow passages connect the corresponding flow passages 56, 84 to 88 and the working fluid chambers 2FR, 2FL, 2RR, 2RL in communication with each other, and filters 142FR, 142FL, 142R are provided on the way, respectively.
It has R and 142 RL. Actuators 1FR, 1FL,
Vehicle height sensors 144FR, 144FL, 144RR, 144RL for detecting vehicle heights XFR, XFL, XRR, XRL of portions corresponding to the respective wheels are provided at positions close to 1RR, 1RL.

Pilot operated shutoff valves 150, 152, 154, 156 are provided in the middle of the connection flow paths 56, 84 to 88, respectively, and these shutoff valves respectively correspond to the corresponding pressure control valves 40, 42, 44 ,.
When the pressure difference between the pressure in the high pressure flow passages 18FR, 18FL, 18RR, 18RL upstream of 46 and the pressure in the drain flow passages 110, 112, 114, 116 is below a predetermined value, the valve closed state is maintained. It is like this. Further, the portions of the connection flow paths 56, 84 to 88 between the corresponding pressure control valve and the shutoff valve are respectively connected to the flow paths 158, 160, 16 respectively.
2,164 corresponding pressure control valve flow paths 50, 60, 62, 64
Is connected to the downstream side of the variable throttle. Relief valves 166, 168, 17 are provided in the middle of the flow paths 158-164, respectively.
0, 172 are provided, and these relief valves take in the pressure on the upstream side of the corresponding flow passages 158, 160, 162, 164, that is, the side of the corresponding connection flow passage as a pilot pressure, and When the pressure exceeds a predetermined value, the valve is opened to remove a part of the working fluid in the corresponding connection flow passage 50,
It leads to 60-64.

The shutoff valves 150 to 156 are high pressure flow paths 18FR, 18FL, 18R, respectively.
The valve closed state may be maintained when the differential pressure between the pressure in R and 18RL and the atmospheric pressure is equal to or less than a predetermined value.

The other ends of the low pressure passages 48FR and 48FL are connected to one end of the low pressure passage 48F for the front wheels, and the other ends of the low pressure passages 48RR and RL are connected to one end of the low pressure passage 48R for the rear wheels. . The other ends of the low pressure flow paths 48F and 48R are connected to one end of the low pressure flow path 48 so as to communicate with each other. The low-pressure flow path 48 has an oil cooler 174 in the middle and is connected to the reserve tank 4 at the other end via a filter 176. A portion of the high pressure passage 18 between the check valve 20 and the attenuator 22 is connected to the low pressure passage 48 by a passage 178. A relief valve 180, which is set to a predetermined pressure in advance, is provided in the flow path 178.

In the illustrated embodiment, the high-pressure flow passage 18R and the low-pressure flow passage 48R are connected to each other by a flow passage 188 having a filter 182, a remaining portion 184, and a normally open type flow rate adjustable solenoid on-off valve 186 in the middle. There is. The solenoid opening / closing valve 186 is configured so that the solenoid 190 is excited and the exciting current is changed to open the valve and adjust the flow rate of the working fluid passing through the valve. The high-pressure flow path 18R and the low-pressure flow path 48R are connected to each other by a flow path 194 having a pilot operated on-off valve 192 on the way. The on-off valve 192 takes in the pressure on both sides of the throttle 184 as pilot pressure, maintains the closed valve position 192a when there is no differential pressure on both sides of the throttle 184, and when the pressure on the high-pressure flow path 18R side with respect to the throttle 184 is high. It is adapted to switch to the valve opening position 192b. Thus, the throttle 184, the electromagnetic on-off valve 186, and the on-off valve 192 cooperate with each other to selectively connect the high-pressure flow path 18R and the low-pressure flow path 48R, and thus the high-pressure flow path 18 and the low-pressure flow path 48, to the high-pressure flow path. A bypass valve 196 that controls the flow rate of the working fluid flowing to the lower pressure passage is configured.

Further, in the illustrated embodiment, the high pressure flow path 18R and the low pressure flow path 4
The 8R is provided with pressure sensors 197 and 198, respectively, and these pressure sensors detect the pressure Ps of the working fluid in the high-pressure passage and the pressure Pd of the working fluid in the low-pressure passage, respectively. There is. In addition, the connection channels 56, 84, 86,
88 are pressure sensors 199FR, 199FL, 199RR, 199RL respectively.
Are provided, and the pressures inside the working fluid chambers 2FR, 2FL, 2RR, and 2RL are detected by these pressure sensors, respectively. Further, the reserve tank 4 has a temperature sensor 195 for detecting the temperature T of the working fluid stored in the tank.
Is provided.

The electromagnetic on-off valve 186 and the pressure control valves 32-38 are controlled by the electric control device 200 shown in FIG. The electric control device 200 includes a microcomputer 202. The microcomputer 202 may have a general structure as shown in FIG. 2, and includes a central processing unit (CPU) 204 and a read only memory (ROM) 206.
, A random access memory (RAM) 208, an input port device 210, and an output port device 212, which are connected to each other by a bidirectional common bus 214.

The input port device 210 has an engine 14
Signal indicating the working fluid temperature T from the temperature sensor 195, signals indicating the pressure Ps in the high pressure passage and pressure Pd in the low pressure passage respectively from the pressure sensors 197 and 198, and the pressure sensor 199FL. , 199FR, 199RL, 199RR, the pressure Pi in the working fluid chambers 2FL, 2FR, 2RL, 2RR (i = 1,
2,3,4) signal, ignition switch (IG
SW) 216 signal indicating whether or not the ignition switch is on, vehicle height sensor 144FL, 144FR, 144RL, 1
From 44RR, signals indicating vehicle heights Xi (i = 1, 2, 3, 4) of portions corresponding to the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel are respectively input.

Further, the input port device 210 outputs a signal indicating the vehicle speed V from the vehicle speed sensor 234 and a longitudinal acceleration G from the longitudinal G (acceleration) sensor 236.
Signal indicating a, lateral acceleration Gl from lateral G (acceleration) sensor 238
, A signal indicating the steering angle θ from the steering angle sensor 240, a signal indicating whether the ABS and TRCS are operating from the anti-lock brake system (ABS) 244 and the traction control system (TRCS) 246, respectively, the vehicle height A signal indicating whether the vehicle height control mode set by the setting switch 248 is the high mode or the normal mode is input.

As is well known, ABS is a system that controls the braking force on a wheel when slip between the wheel and the road surface is detected during vehicle control, and TRCS is a slip between the wheel and road surface during vehicle acceleration. This is a system for controlling the driving force of the wheels when is detected.

The input port device 210 appropriately processes the signal input thereto, and the CPU 204 based on the program stored in the ROM 206.
The processed signal is output to the CPU and the RAM 208 in accordance with the instruction. ROM206 is shown in FIGS. 3 and 6A to 6C.
Control flow shown in FIG. 4, FIG. 5 to FIG. 7 and FIG.
Map shown in Fig. 19, standard friction coefficient of road surface μ ₀
Is stored, and the CPU processes signals based on each control flow. Output port device 212 is CPU204
In accordance with the instruction of, the control signal is output to the electromagnetic on-off valve 186 via the drive circuit 220, and the pressure control valve 32 to the drive circuit 222 to 228.
38, specifically, output control signals to the solenoids 58, 78, 80, 82 of the variable diaphragms 54, 72, 74, 76, respectively, and drive circuit 230
A control signal is output to the display device 232 via the.

Next, the operation of the illustrated embodiment will be described with reference to the flow chart shown in FIG.

The control flow shown in FIG. 3 is started by closing the ignition switch 216. Also the third
In the flow chart shown in the figure, the flag Fc relates to whether or not the pressure Ps of the working fluid in the high-pressure passage has become equal to or higher than the threshold pressure Pc for completely opening the shutoff valves 150 to 156. 1 indicates that the pressure Ps has become equal to or higher than the pressure Pc, and the flag Fs corresponds to a standby pressure Pbi (i = 1, 2, 3, 4) of the pressure control valves 32 to 38 described later. It is related to whether or not the standby pressure current Ibi (i = 1, 2, 3, 4) is set, and 1 indicates that the standby pressure current is set.

First, in step 10, a main relay not shown is turned on, and then step 20 is proceeded to.

In step 20, the memory contents stored in the RAM 208 are cleared, the friction coefficient μ of the road surface is set to μ ₀ , all flags are reset to 0, and then the process proceeds to step 30.

In step 30, a signal indicating the rotation speed N of the engine 14 detected by the rotation speed sensor 16, a signal indicating the temperature T of the working fluid detected by the temperature sensor 195, and a pressure sensor.
A signal indicating the pressure Ps in the high-pressure channel detected by 197,
A signal indicating the pressure Pd in the low pressure passage detected by the pressure sensor 198, the pressure Pi in the working fluid chambers 2FL, 2FR, 2RL, 2RR detected by the pressure sensors 199FL, 199FR, 199RL, 199RR
Signal indicating whether the ignition switch 216 is in the ON state, vehicle height sensor 144FL, 144FR, 144R
L, a signal indicating vehicle height Xi detected by 144RR, a signal indicating vehicle speed V detected by vehicle speed sensor 234, a signal indicating longitudinal acceleration Ga detected by longitudinal G sensor 236, lateral G
A signal indicating the lateral acceleration Gl detected by the sensor 238, a signal indicating the steering angle θ detected by the steering angle sensor 240, A
A signal indicating whether ABS and TRCS are operating is read from BS244 and TRCS246, respectively, and a signal indicating whether the mode set by vehicle height setting switch 248 is the high mode or the normal mode is read. After step
Proceed to 40.

In step 40, it is determined whether or not the ignition switch is in the off state, and when it is determined that the ignition switch is in the off state, the process proceeds to step 200 and the ignition switch is in the on state. When the determination is made, the process proceeds to step 50.

In step 50, it is determined whether or not the engine is operating by determining whether or not the engine speed N detected by the engine speed sensor 16 and read in step 30 exceeds a predetermined value. When it is determined that the engine is not operating, the process proceeds to step 90, and when it is determined that the engine is operating, the process proceeds to step 60.

The determination as to whether or not the engine is operating may be made by determining as to whether or not the power generation voltage of a generator driven by the engine, which is not shown in the figure, is equal to or higher than a predetermined value.

In step 60, the operation of the timer for the time Ts from the time when the operation of the engine is started to the time when the standby pressure Pbi of the pressure control valves 32 to 38 is set in step 150 described later is started, Then proceed to step 70.
In this case, if the timer Ts has already been operated, the timer continues to count.

In step 70, according to Ib = Ib + ΔIbs, the current Ib supplied to the solenoid 190 of the solenoid valve 186 of the bypass valve 196 is stored in the ROM 206 according to the map corresponding to the graph shown in FIG. It is calculated, and then the process proceeds to step 80.

In step 80, the current calculated in step 70
The bypass valve 196 is driven in the valve closing direction by energizing the solenoid 190 of the electromagnetic opening / closing valve 186, and then the process proceeds to step 90.

In step 90, it is judged whether or not the average value Ps of the pressure in the high-pressure flow path is equal to or more than the threshold value Pc, and when it is judged that Ps ≧ Pc is not satisfied, the routine proceeds to step 120. , Ps
If it is determined that ≧ Pc, the process proceeds to step 100.

In step 100, the flag Fc is set to 1, and then the process proceeds to step 110.

In step 110, in order to control the ride comfort of the vehicle and the attitude control of the vehicle body, as described in detail later with reference to FIGS. 6A to 6C and FIGS. 7 to 19, step 30 is performed. By performing active calculation based on various signals read in, the current Iui supplied to the solenoids 58, 78, 80, 82 of the variable throttles 54, 72 to 76 of each pressure control valve is calculated. Then proceed to step 170.

In step 120, it is judged whether the flag Fc is 1 or not, and it is judged that Fc = 1, that is, the pressure Ps of the working fluid in the high-pressure passage becomes equal to or higher than the threshold pressure Pc. After that, when it is determined that the value is lower than this value, the routine proceeds to step 110, where it is determined that Fc = 1 is not established, that is, it is determined that the pressure Ps has never exceeded the threshold pressure Pc. Is performed, the routine proceeds to step 130.

In step 130, it is determined whether or not the flag Fs is 1, and when it is determined that Fs = 1, the process proceeds to step 170, and it is determined that Fs = 1 is not established. If so, proceed to step 140.

In step 140, it is determined whether or not the time Ts has elapsed. When it is determined that the time Ts has not elapsed, the process proceeds to step 170, and it is determined that the time Ts has elapsed. When is performed, the process proceeds to step 150.

In step 150, the operation of the Ts timer is stopped, and the pressure Pi read in step 30 is the standby pressure.
Based on the map corresponding to the graph shown in FIG. 5 stored in the RAM 208 as Pbi and stored in the ROM 206, the connection flow paths 56, 84 to 88 are provided between each pressure control valve and the check valve.
The pressure of the working fluid inside is the standby pressure Pbi, that is, the working fluid chamber 2F detected by the corresponding pressure sensor.
Variable throttles 72, 54, 7 of pressure control valves 34, 32, 38, 36 in order to bring the pressure substantially equal to the pressure Pi in L, 2FR, 2RL, 2RR.
Current Ibi applied to solenoids 78, 58, 82, 80 of 6, 74
(I = 1, 2, 3, 4) is calculated, and the subsequent step
Proceed to 160.

In step 160, the flag Fs is set to 1, and then the process proceeds to step 170.

In step 170, it is judged whether or not the current Ib calculated in step 70 is the reference value Ibo or more, and Ib
If it is determined that ≧ Ibo is not satisfied, step 30
Returning to, when it is determined that Ib ≧ Ibo, the process proceeds to step 180.

In step 180, it is judged whether the pressure Ps of the working fluid in the high-pressure passage read in step 30 is the reference value Pso (<Pc) or more, and Ps ≧ Pso is not satisfied. When the determination is made, the process returns to step 30, and when the determination that Ps ≧ Pso is made, the process proceeds to step 190.

In step 190, the current Ibi calculated in step 150 or the current Iui calculated in step 110 is output to the solenoids 58, 78 to 82 of the variable throttles of the pressure control valves. The pressure control valve is driven to control its control pressure, and then the process returns to step 30,
30 to 190 are repeated.

In step 200, the bypass valve 196 is opened by stopping the energization of the solenoid 190 of the solenoid opening / closing valve 186, and then the process proceeds to step 210.

In step 210, the main relay is turned off, which terminates the control flow shown in FIG. 3 and stops energizing the electric control device 200 shown in FIG. It

The pressure control by the bypass valve at the time of starting the operation described above does not form an essential part of the present invention, and the details of this pressure control are disclosed in Japanese Patent Application Laid-Open No. 63-307189. See issue. Further, the pressure control by the bypass valve when the operation is stopped may be performed as described in Japanese Patent Application No. 63-307190 filed by the applicant of the present application.

Next, the active calculation performed in step 110 will be described with reference to FIGS. 6A to 6C and FIGS. 7 to 19.

First, in step 300, the heave target value Rxh, the pitch target value Rxp, and the roll target value Rxr based on the target attitude of the vehicle body are calculated based on the maps corresponding to the graphs shown in FIGS. 7 to 9, respectively. Then, proceed to Step 310.

Incidentally, in FIG. 7, the solid line and the broken line show the patterns when the vehicle height control mode set by the vehicle height setting switch is the normal mode and the high mode, respectively.

In step 310, the vehicle height X _{1 at the} positions corresponding to the left front wheel, right front wheel, left rear wheel, and right rear wheel read in step 30.
Based on X ₄ to X ₄ , displacement mode conversion is calculated for heave (Xxh), pitch (Xxp), roll (Xxr), and warp (Xxw) according to the following formula, and then the process proceeds to step 320.

_{Xxh = (X 1 + X 2} ) + (X 3 + X 4) Xxp = - (X 1 + X 2) + (X 3 + X 4) Xxr = (X 1 -X 2) + (X 3 -X 4) Xxw = (X ₁ -X ₂₎ - Te is at the (X ₃ -X ₄₎ step 320, performs the operation of the deviation of the displacement modes according to the following equation, the process proceeds to thereafter step 330.

Exh = Rxh-Xxh Exp = Rxp-Xxp Exr = Rxr-Xxr Exw = Rxw-Xxw In this case, Rxw may be 0, or Xxw calculated in step 310 immediately after the activation of the active suspension or the past It may be the average value of Xxw calculated in several cycles of. If | Exw | ≦ W ₁ (a positive integer), Exw = 0.

In step 330, displacement feedback control PID compensation calculation is performed according to the following equation, and then step 3
Proceed to 40.

Cxh = Kpxh · Exh + Kixh · Ixh (n) + Kdxh {Exh (n) -Exh (n-n 1)} Cxp = Kpxp · Exp + Kixp · Ixp (n) + Kdxp {Exp (n) -Exp (n-n 1)} cxr = Kpxr · Exr + Kixr · Ixr (n) + Kdxr {Exr (n) -Exr (n-n 1)} Cxw = Kpxw · Exw + Kixw · Ixw (n) + Kdxw {Exw (n) -Exw (n-n 1)} Note at a above formulas, Ej (n) (j = xh, xp, xr, xw) are the current Ej, Ej (n-n ₁₎ is Ej of n ₁ cycles before. Ij (n) and Ij (n-1) are Ij at the present time and one cycle before, respectively, and Tx is a time constant, and Ij (n) = Ej (n) × Tx + Ij (n-1), and Ijmax is predetermined. As a value, | Ij | ≦ Ijmax. Further, the coefficients Kpj, Kij, and Kdj (j = xh, xp, xr, xw) are a proportional constant, an integral constant, and a differential constant, respectively.

In step 340, the inverse transformation of the displacement mode is calculated according to the following equation, and then the process proceeds to step 350.

Px ₁ = 1/4 ・ Kx ₁ (Cxh−Cxp + Cxr + Cxw) Px ₂ = 1/4 · Kx ₂ (Cxh−Cxp−Cxr−Cxw) Px ₃ = 1/4 · Kx ₃ (Cxh + Cxp + Cxr−Cxw) Px ₄ = 1 / 4 · Kx ₄ (Cxh + Cxp−Cxr−Cxw) Kx ₁ , Kx ₂ , Kx ₃ and Kx ₄ are proportional constants.

In step 350, based on the maps corresponding to the graphs shown in FIG. 10 and FIG. 11, the correction amounts Pga and Pgl of the pressure in the front-rear direction and the lateral direction of the vehicle are calculated, respectively. Proceed to 360.

In step 360, the pitch (Cgp) is calculated according to the following formula.
The PD compensation calculation of the G feedforward control is performed for the roll and the roll (Cgr), and then the process proceeds to step 370.

Cgp = Kpgp · Pga + Kdgp {Pga (n) −Pga (n−n ₁ )} Cgr = Kpgr · Pgl + Kdgr {Pgl (n) −Pgl (n−n ₁ )} In the above equations, Pga (n) And Pgl (n) are the current Pga and Pgl, respectively, and Pga (n−n ₁ ) and Pgl (n−).
n ₁ ) is Pga and Pgl before n ₁ cycles, respectively. Also
Kpgp and Kpgr are proportional constants, and Kdgp and Kdgr are differential constants.

In step 370, the predicted lateral acceleration, that is, l is calculated from the steering angle θ and the vehicle speed V based on the map corresponding to the graph shown in FIG. 12, and then the process proceeds to step 380.

In step 380, the steering angle velocity is calculated in accordance with = θ−θ ′, where θ ′ is the steering angle read in step 30 one cycle before in the flowchart of FIG. 3, and from this steering angle velocity and vehicle speed V Change rate of predicted lateral acceleration based on the map corresponding to the graph shown in FIG. 13, that is, Is calculated, and then the process proceeds to step 390.

In step 390, it is determined whether or not the ABS is operating. When it is determined that the ABS is not operating, the process proceeds to step 410, and it is determined that the ABS is operating. If so, proceed to step 400.

In step 400, the friction coefficient μ ′ of the road surface is estimated and calculated based on the map corresponding to the graph shown in FIG. 14, and then the process proceeds to step 470.

In step 410, it is determined whether or not TRCS is operating. When it is determined that TRCS is not operating, the process proceeds to step 430, and it is determined that TRCS is operating. If so, proceed to step 420.

In step 240, the friction coefficient μ ′ of the road surface is estimated and calculated based on the map corresponding to the graph shown in FIG. 15, and then the process proceeds to step 470.

The maps corresponding to the graphs shown in FIG. 14 and FIG. 15 may be set appropriately according to the control performance of ABS and TRCS, respectively.

In step 430, the rate of change in the predicted lateral acceleration calculated in step 380 It is determined whether the absolute value of is less than the reference value Cgl (a positive constant), When it is determined that it is not, the process proceeds to step 490, If it is determined that the value is, the process proceeds to step 440.

At step 440, the lateral acceleration deviation ΔGl is calculated according to ΔGl = 1-Gl, and then the routine proceeds to step 450.

In step 450, the correction value Δμ of the friction coefficient of the road surface is calculated based on the map corresponding to the graph shown in FIG. 16, and then the process proceeds to step 460.

In step 460, the friction coefficient of the road surface is corrected and calculated according to μ ′ = μ−Δμ, and then the process proceeds to step 470.

In step 470, the road friction coefficient μ is
Alternatively, the road surface friction coefficient μ ′ estimated and calculated in 420 or the road surface friction coefficient μ ′ corrected and calculated in step 460.
Is rewritten, and then the process proceeds to step 480.

In step 480, based on the maps corresponding to the graphs shown in FIGS. 17 and 18, respectively,
Rate of change of lateral acceleration of the calculation formula in 490 The front wheel gain K ₁ f and the rear wheel gain K ₁ r are calculated, and then the process proceeds to step 490.

In step 490, the inverse conversion operation in G mode is performed according to the following equation, and then the process proceeds to step 500.

Kg ₁ , Kg ₂ , Kg ₃ , and Kg ₄ are proportional constants, respectively, and K ₂ f
And K ₂ r are constants as distribution gains between the front and rear wheels.

In step 500, based on the pressure Pbi calculated in step 150 and the result calculated in steps 340 and 490, each pressure control according to Pui = Pxi + Pgi + pbi (i = 1, 2, 3, 4) The target control pressure Pui of the valve is calculated,
Then proceed to step 510.

In step 510, the target current to be supplied to each pressure control valve is calculated according to the following equation, and then the process proceeds to step 520.

I ₁ = Ku ₁ Pu ₁ + Kh (Pse-Ps) -Kl · Pd-α I ₂ = Ku ₂ Pu ₂ + Kh (Pse-Ps) -Kl · Pd-α I ₃ = Ku ₃ Pu ₃ + Kh (Pse-Ps ) −Kl ・ Pd I ₄ ＝ Ku ₄ Pu ₄ ＋ Kh (Pse−Ps) −Kl ・ Pd where Ku ₁ , Ku ₂ , Ku ₃ , Ku ₄ are proportional constants for each wheel, and Kh and Kl are high pressures, respectively. A correction coefficient for the pressure in the flow passage and a pressure in the low pressure passage, α is a correction constant between the front and rear wheels, and Pse is a reference pressure in the high pressure passage.

In step 520, the temperature correction coefficient Kt is calculated based on the temperature T of the working fluid read in step 30 and the map corresponding to the graph shown in FIG. 19, and Iti = Kt · Ii ( i = 1,2,3,4), the temperature correction calculation of the target current is performed, and then the process proceeds to step 530.

In step 530, the current warp (the amount of twist around the longitudinal axis of the vehicle body) according to Iw = (It ₁ −It ₂ ) − (It ₃ −It ₄ ).
Is calculated, and then the process proceeds to step 540.

In step 540, the deviation of the current warp is calculated according to the following equation using Riw as the target current warp, and then the process proceeds to step 550.

Eiw = Riw-Iw The target current warp Riw in the above equation may be zero.

In step 550, the current warp target control amount is calculated according to Eiwp = KiwpEiw using Kiwp as a proportional constant, and then the process proceeds to step 560.

In step 560, the inverse conversion of the current warp is calculated according to the above equation, and then the process proceeds to step 570.

Iw ₁ = Eiwp / 4 Iw ₂ = -Eiwp / 4 Iw ₃ = -Eiwp / 4 Iw ₄ = Eiwp / 4 In step 570, the following formula is used based on the result calculated in steps 520 and 560. Then, the final target current Iui to be supplied to each pressure control valve is calculated, and then the process proceeds to step 170 in FIG.

Iui = Ii + Iwi (i = 1, 2, 3, 4) Thus, according to this embodiment, the friction coefficient μ of the road surface is obtained in steps 390 to 470, and the gains K ₁ f and K ₁ are obtained in step 480. r is set to be smaller as the road surface friction coefficient is smaller based on the maps corresponding to the graphs shown in FIGS. 17 and 18, respectively, and depending on the road surface friction coefficient, it is based on the actual lateral acceleration of the vehicle body. The feedforward control amount based on the predicted rate of change in lateral acceleration is reduced as the friction coefficient of the road surface is smaller without changing the control amount. Therefore, not only can the vehicle roll be effectively controlled without a response delay when the vehicle turns while traveling on a normal road surface, but also when the vehicle turns while traveling on a road surface having a small friction coefficient. It is possible to surely avoid excessive control of the roll of the vehicle, and to effectively suppress the roll of the vehicle body based on the actual lateral acceleration of the vehicle body.

In the above embodiment, the friction coefficient of the road surface is estimated and calculated based on the information from ABS and TRCS.
The coefficient of friction of the road surface may be determined in any manner known in the art.

Further, in the above-mentioned embodiment, when ABS and TRCS are in the non-operating state, the friction coefficient of the road surface estimated during the operation of these ABS is corrected based on the deviation ΔGl between the estimated lateral acceleration and the actual lateral acceleration. However, the standard friction coefficient μ of the road surface is set to μ ₀ when a predetermined time has elapsed from the time when ABS and TRCS became inactive, and this is corrected based on the deviation ΔGl. It may be configured to be calculated.

Further, in the above embodiment, the feedforward control is performed based on the rate of change of the lateral acceleration based on the vehicle speed and the steering angular velocity, but the feedforward control based on the predicted lateral acceleration based on the vehicle speed and the steering angle is performed. The gain may be set to be smaller as the road friction coefficient becomes smaller.

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

EFFECTS OF THE INVENTION As is apparent from the above description, according to the present invention, the supply and discharge of the working fluid to and from the fluid pressure actuator is controlled by the first control amount and the vehicle speed and the steering angle or the vehicle speed and the steering angular velocity based on the acceleration of the vehicle body. Based on the second control amount (control amount based on the predicted lateral acceleration), the control means changes the friction coefficient of the road surface substantially without changing the first control amount depending on the friction coefficient of the road surface. It is configured to reduce the second control amount based on the vehicle speed and the steering angle or the vehicle speed and the steering angular velocity, so that the vehicle body rolls when the vehicle turns on a road surface having a high friction coefficient. Not only can it be effectively suppressed without delay, but also when the vehicle turns while traveling on a road surface with a low friction coefficient,
It is possible to prevent unpleasant rolls and reverse rolls of the vehicle body due to excessive supply and discharge control of the working fluid to the actuator, and to consume the working fluid in an amount corresponding to the reduction amount of the second control amount. Can be reduced.

Further, according to the present invention, since the first control amount is not substantially changed depending on the friction coefficient of the road surface, it is possible to effectively suppress the roll of the vehicle body based on the actual acceleration of the vehicle body. Compared with the case where the roll control of the vehicle body is stopped when the vehicle turns while traveling on a road surface with a small road surface, or the first control amount is reduced as the friction coefficient of the road surface is lower, It is possible to improve the steering stability of the vehicle when turning while traveling on a small road surface.

[Brief description of drawings]

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 electric control device of the embodiment shown in FIG. FIG. 3 is a flow chart showing a control flow achieved by the electric control device shown in FIG.
Fig. 5 is a graph showing a map used to calculate the current Ib supplied to the bypass valve at the start of operation of the active suspension. Fig. 5 is the pressure Pi in the working fluid chamber of each actuator and the pressure Pi 6A to 6C are flow charts showing a routine of the active calculation performed in step 110 of the flow chart shown in FIG. 3, and FIG. 7 is a vehicle speed V. Graph showing the relationship between the target displacement Rxh and the 8th
Figure is a graph showing the relationship between longitudinal acceleration Ga and target displacement Rxp. Figure 9 is a graph showing the relationship between lateral acceleration Gl and target displacement Rxr. Figure 10 is a graph showing longitudinal acceleration Ga and pressure. A graph showing the relationship between the corrected amount Pga and Fig. 11 shows the lateral acceleration Gl.
And FIG. 12 is a graph showing the relationship between the vehicle speed V and the steering angle θ and the predicted lateral acceleration l, and FIG. 13 is a graph showing the relationship between the vehicle speed V and the steering angular speed. Lateral acceleration change rate A graph showing the relationship between, and FIGS. 14 and 15 are graphs showing the relationship between the longitudinal acceleration Ga and the friction coefficient μ of the road surface,
FIG. 16 is a graph showing the relationship between the deviation ΔGl of lateral acceleration and the correction value Δμ of the friction coefficient of the road surface, and FIGS. 17 and 18 are the friction coefficient μ of the road surface and the rate of change of the predicted lateral acceleration, respectively. FIG. 19 is a graph showing the relationship between the gains K ₁ f and K ₁ r of the feedforward control based on the above, and FIG. 19 is a graph showing the relationship between the temperature T of the working fluid and the correction coefficient Kt. 1FR, 1FL, 1RR, 1RL ... Actuator, 2FR, 2FL, 2R
R, 2RL …… Working fluid chamber, 4 …… Reservoir tank, 6 …… Pump, 8 …… Filter, 10 …… Suction passage, 12 …… Drain passage, 1
4 …… Engine, 16 …… Revolution sensor, 18 …… High pressure flow path, 20
...... Check valve, 22 …… Attenuator, 24, 26 …… Accumulator, 32, 34, 36, 38 …… Pressure control valve, 40, 42, 44, 46
...... Switching control valve, 48 ...... Low pressure passage, 52 ...... Fixed throttle, 54
...... Variable throttle, 56 ...... Connection flow path, 58 ...... Solenoid, 66, 6
8, 70 …… Fixed aperture, 72, 74, 76 …… Variable aperture, 78, 80, 8
2 ... Solenoid, 84, 86, 88 ... Connection flow path, 110-118 ...
… Drain flow path, 120 …… Filter, 124-130 …… Restrictor, 132
~ 138 …… Accumulator, 144FR, 144FL, 144RR, 144RL
...... Vehicle height sensor, 150 to 156 ...... Shut-off valve, 166 to 172 ...... Relief valve, 174 ...... Oil cooler, 176 ...... Filter, 180 ......
Relief valve, 182 ... Filter, 184 ... Throttle, 186 ... Electromagnetic on-off valve, 190 ... Solenoid, 192 ... On-off valve, 196 ... Bypass valve, 197F, 197R, 198 ... Pressure sensor, 199FR, 199F
L, 199RR, 199RL …… Pressure sensor, 200 …… Electric control device, 202 …… Microcomputer, 204 …… CPU, 206 …… R
OM, 208 …… RAM, 210 …… input port device, 212 …… output port device, 216 …… IGSW, 220 ～ 230 …… driving circuit, 232 ……
Display, 234 …… Vehicle speed sensor, 236 …… Front and rear G sensor, 238…
… Lateral G sensor, 240 …… Steering angle sensor, 244 …… ABS, 246…
… TRCS, 248 …… Vehicle height setting switch, 250-256 …… Variable diaphragm, 258-264 …… Drive circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Yutani, 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Inventor, Toshio Onuma 1, Toyota Town, Aichi Prefecture Toyota Motor Corporation ( 72) Inventor Koichi Kokubo, 2-1-1 Asahi-cho, Kariya city, Aichi prefecture, Aisin Seiki Co., Ltd. (72) Inventor, Satoshi Naganawa 2-1-1, Asahi-cho, Kariya city, Aichi prefecture (56) References JP-A-62-286814 (JP, A) JP-A-62-286813 (JP, A) JP-A-63-173711 (JP, A)

Claims (1)

[Claims] 1. A fluid pressure actuator arranged between each wheel and a vehicle body, a working fluid supply / discharge means for supplying / discharging a working fluid to / from the actuator, a means for obtaining a friction coefficient of a road surface, and the vehicle body. Means for detecting the acceleration, a means for detecting the vehicle speed, a means for obtaining the steering angle or the steering angular velocity, and a first control amount based on the acceleration of the vehicle body and a second speed based on the vehicle speed and the steering angle or the vehicle speed and the steering angular velocity. Control means for controlling the working fluid supply / discharge means in accordance with the control amount of the road surface, and the control means does not substantially change the first control amount depending on the friction coefficient of the road surface. A hydraulic active suspension configured to reduce the second controlled variable as the coefficient decreases.