JPH0751364Y2 - 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 hydraulic active suspension of a vehicle equipped with a four-wheel steering device.

2. Description of the Related Art A steering device for a vehicle such as an automobile is disclosed in, for example, JP-A-60-13.
A so-called vehicle speed-sensitive four-wheel steering system in which the front-rear wheel steering angle ratio changes according to the vehicle speed as described in Japanese Patent No. 5368, and steering angle changes as described in, for example, Japanese Patent Laid-Open No. 55-91458. So-called steering angle responsive four-wheel steering devices in which the front-rear wheel steering angle ratio changes accordingly have been known in the past.With these four-wheel steering devices, compared to the case of a vehicle in which only the front two wheels are steered. Therefore, the small turning performance of the vehicle in the low vehicle speed range is improved, and the steering stability in the middle and high speed ranges is improved.

However, when an abnormality occurs in the four-wheel steering system, the front-rear wheel steering angle ratio is not properly controlled, which deteriorates the steering stability of the vehicle, resulting in unstable running of the vehicle. Become.

In view of the above-mentioned problems in a vehicle equipped with a four-wheel steering device, the present invention suppresses deterioration of the steering stability of the vehicle even if an abnormality occurs in the four-wheel steering device, thereby improving the vehicle performance. It is an object of the present invention to provide a fluid pressure type active suspension configured so as to ensure stable running stability.

According to the present invention, a fluid pressure type active suspension of a vehicle equipped with a four-wheel steering system is provided.
A fluid pressure actuator arranged between each vehicle and a vehicle body, a working fluid supply / discharge means for supplying / discharging a working fluid to / from the actuator, and a control unit for controlling the working fluid supply / discharge means according to a running state of the vehicle. By having a control means for controlling the roll rigidity on the front wheel side and the rear wheel side, and means for detecting an abnormality of the four-wheel steering device, and the control means detects an abnormality of the four-wheel steering device. Sometimes this is accomplished with a fluid pressure active suspension configured to increase the ratio of roll stiffness on the front wheel side to the rear wheel side.

Effect of the Invention According to the above-mentioned configuration, when an abnormality of the four-wheel steering system is detected, the working fluid supply / discharge means is controlled so that the ratio of the roll rigidity of the front wheel side to the rear wheel side is increased. Since the steering characteristic of is shifted to the understeer direction,
Deterioration of the steering stability due to the inadequate control of the front-rear wheel steering angle ratio is suppressed, and good traveling stability of the vehicle is secured.

Hereinafter, embodiments of 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 pilot 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.

A low-pressure passage 48FR is connected to the R port of the switching control valve 40, and a connection passage 56 is connected to the A port. The switching control valve 40 has a flow path 50 between the fixed throttle 52 and the variable throttle 54.
This is a spool valve that takes in the internal pressure Pp and the pressure Pa in the connection flow path 56 as pilot pressure. When the pressure Pp is higher than the pressure Pa, the port P is switched to the switching position 40a which connects and connects the port P and the port A. When the pressures Pp and Pa are equal to each other, the switching position is switched to the switching position 40b that shuts off the communication of all ports, and when the pressure Pp is lower than the pressure Pa, the switching position is switched to the switching position 40c that connects the ports R and A to each other. ing. 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, each of the pressure control valves 34 to 38 is a pilot-operated three-port switching control valve 42, 44, 46 corresponding to the switching control valve 40 of the pressure control valve 32, and the flow passages 60, 62, 62 corresponding to the flow passage 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 in the same manner as 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 front wheel, low-pressure passage 48RR for the right rear wheel, and left rear wheel, respectively. Is connected to one end of the low-pressure flow path 48RL, and one end of each of the connection flow paths 84, 86, and 88 is connected to the A port. Further, the switching control valves 42 to 46 are spool valves for taking 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 pressure. 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 respectively working fluid chambers 2FR, 2FL,
Cylinder for defining 2RR and 2RL 106FR, 106FL, 106RR, 106
RL and piston 10 that fits in the corresponding cylinder
8FR, 108FL, 108RR, 108RL, each connected to a vehicle body not shown in the figure by a cylinder, and connected to a suspension arm not shown in the figure at the tip of the rod portion of the piston. There is. 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,
A vehicle height sensor for detecting the vehicle heights XFR, XFL, XRR, and XRL of the parts corresponding to the wheels, respectively, at positions close to 1RR and 1RL.
144FR, 144FL, 144RR, 144RL are provided.

Pilot-operated shut-off valves 150, 152, 154, 156 are provided in the middle of the connection flow paths 56, 84-88, respectively, and these shut-off valves respectively correspond to 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 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 path 18R and the low-pressure flow path 48R are connected to each other by a flow path 188 having a filter 182, a throttle 184, and a normally open type flow rate adjustable electromagnetic on-off valve 186 in the middle. There is. The solenoid opening / closing valve 186 is configured so that its solenoid 190 is excited and its 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 in the middle. 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. Valve open position 192
It is designed to switch to b. Thus, the throttle 184, the solenoid on-off valve 186, and the on-off valve 192 cooperate with each other so that the high pressure passage 18R
And the low-pressure flow path 48R, and thus the high-pressure flow path 18 and the low-pressure flow path 48, are selectively connected to form a bypass valve 196 for controlling the flow rate of the working fluid flowing from the high-pressure flow path to the low-pressure flow path.

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 provided with pressure sensors 199FR, 199FL, 199RR, 199RL, respectively, and these pressure sensors detect the pressures in the working fluid chambers 2FR, 2FL, 2RR, 2RL, respectively. Further, the reserve tank 4 is provided with a temperature sensor 195 for detecting the temperature T of the working fluid stored in the tank.

The vehicle to which the illustrated embodiment is applied incorporates a so-called vehicle speed-sensitive four-wheel steering device in which the steering angle ratio of the front and rear wheels changes according to the vehicle speed, as shown in the fourteenth embodiment. Particularly, in the four-wheel steering system of the illustrated embodiment, the changeover switch provided in the vehicle interior changes the normal mode Wmn from a reverse phase to an in-phase in a relatively high and low vehicle speed range and a reverse mode in a relatively high vehicle speed range. It is configured to switch to the sports mode Wms that changes from phase to phase.

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
Signal indicating the steering angle θ from the steering angle sensor 240, a signal indicating whether the four-wheel steering device is operating normally from the control device of the four-wheel steering device 242, and a steer characteristic of the mode change switch 244. A signal indicating whether the control mode is the A mode or the B mode, the vehicle height setting switch 248
A signal indicating whether the vehicle height control mode set in this way is the high mode or the normal mode is input.

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. ROM 206 is shown in FIG. 3 and FIGS. 6A to 6C.
The control flow shown in the figure and the maps shown in FIGS. 4 and 5 and FIGS. 7 to 13 are stored, and the CPU processes signals based on each control flow. There is. The output port device 212 outputs a control signal to the electromagnetic on-off valve 186 via the drive circuit 220 according to the instruction of the CPU 204, and the drive circuit 222 to
Control signals are output to the pressure control valves 32 to 38 via 228, specifically, the solenoids 58, 78, 80 and 82 of the variable throttles 54, 72, 74 and 76, respectively, and to the display 232 via the drive circuit 230. Is output.

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 contents stored in the RAM 208 are cleared and all the 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
, A signal indicating whether or not the ignition step 216 is in the ON state, vehicle height sensors 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 signal indicating whether or not the four-wheel steering device 242 is operating normally, a signal indicating whether the control mode of the steer characteristic set by the mode changeover switch 244 is the A mode or the B mode, a vehicle height setting switch A signal indicating whether the mode set by 248 is the high mode or the normal mode is read, and then the process proceeds to step 40.

In step 40, it is determined whether or not the ignition switch is in the off state. When it is determined that the ignition switch is in the off state, the process proceeds to step 200, in which 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 pressure Ps in the high-pressure passage is the threshold value Pc or more, and when it is judged that Ps ≧ Pc is not established, the routine proceeds to step 120, where Ps ≧ When it is determined that it is 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, as described in detail later with reference to FIGS. 6A to 6C and FIGS. 7 to 13, in order to control the riding comfort of the vehicle and the attitude control of the vehicle body, 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 the Pbi and stored in the ROM 206, the connection flow paths 56, 84 between the pressure control valves and the shutoff valves.
The pressure of the working fluid within ~ 88 is the standby pressure Pbi, that is, the working fluid chamber detected by the corresponding pressure sensor.
The variable throttles 72, 54 of the pressure control valves 34, 32, 38, 36, in order to make the pressure substantially equal to the pressure Pi in 2FL, 2FR, 2RL, 2RR,
Current Ib applied to solenoids 78, 58, 82, 80 of 76, 74
i (i = 1, 2, 3, 4) is calculated, and then the process proceeds to step 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 determined whether or not the pressure Ps of the working fluid in the high-pressure flow passage read in step 30 is equal to or higher than the reference value Pso, and it is determined that Ps ≧ Pso is not satisfied. If so, the process returns to step 30, and if it is determined that Ps ≧ Pso, 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 solenoid 190 of the solenoid valve 186 is
The bypass valve 196 is opened by stopping the power supply to the valve, 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 start of the operation described above does not form an essential part of the present invention, and the details of the pressure control are described in Japanese Patent Application No. Sho 63-307189 filed by the same applicant as the present applicant. 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 13.

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 constant), 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 )} In the above equations, Ej (n) (j = xh, xp, xr, xw) is the current Ej, and Ej (n−n ₁ ) is n ₁ cycles before. It is Ej. Further, Ij (n) and Ij (n-1) are Ij at the present time and one cycle before, respectively, and Tx is a time constant, 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, it is determined whether or not there is an abnormality in the four-wheel steering device 242. When it is determined that there is an abnormality, the process proceeds to step 370, and no abnormality has occurred. When the determination is made, the process proceeds to step 350.

In step 350, it is judged whether or not the control mode of the steer characteristic set by the mode changeover switch is the B mode, and when it is judged that it is the B mode, the routine proceeds to step 370. When it is determined that the mode is not the B mode, the process proceeds to step 360.

In step 360, the gains Kxrf and Kxrr in the arithmetic expression executed in step 38 described later, and the gain K ₁ f in the arithmetic expression executed in step 420 described later And K ₁ r and gains K ₂ f and K ₂ r are respectively set to the gains of the A mode as follows, and then step 380 is performed.
Go to.

Kxrf ＝ Kxrfa Kxrr ＝ Kxrra K ₁ f ＝ K ₁ fa K ₁ r ＝ K ₁ ra K ₂ f ＝ K ₂ fa K ₂ r ＝ K ₂ ra In step 370, each gain is the same as in step 360. The gain of B mode is set as follows, and then the process proceeds to step 380.

Kxrf ＝ Kxrfb Kxrr ＝ Kxrrb K ₁ f ＝ K ₁ fb K ₁ r ＝ K ₁ rb K ₂ f ＝ K ₂ fb K ₂ r ＝ K ₂ rb Note that the ratio of each gain set in steps 360 and 370 is It has a magnitude relationship as shown in the table below.

K ₁ fa / K ₁ ra <K ₁ fb / K ₁ rb K ₂ fa / K ₂ ra <K ₂ fb / K ₂ rb In step 380, the calculation of the inverse transformation of the displacement mode is performed according to the following formula. Once done, proceed to step 390.

_{Px 1 = 1/4 · Kx} 1 (Cxh-Cxp + Kxrf · Cxr + Cxw) Px 2 = 1/4 · Kx 2 (Cxh-Cxp-Kxrf · Cxr + Cxw) Px 3 = 1/4 · Kx 3 (Cxh + Cxp + Kxrr · Cxr + Cxw) Px 4 = 1/4 · Kx ₄ (Cxh + Cxp−Kxrr · Cxr + Cxw) Kx ₁ , Kx ₂ , Kx ₃ and Kx ₄ are proportional constants.

In step 390, 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. Go to 400.

In step 400, the pitch (Cgp) is calculated according to the following formula.
And PD of G feedback control for roll (Cgr)
Compensation calculation is performed, and then the process proceeds to step 410.

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 410, the steering angle velocity is calculated according to = 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 Based on the map corresponding to the graph shown in FIG. 12, the change rate of the predicted lateral G, that is, Is calculated, and then the process proceeds to step 380.

In step 420, the inverse G-mode conversion is calculated according to the following equation, and then the process proceeds to step 430.

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

In step 430, based on the pressure Pbi stored in the RAM 208 in step 150 and the result calculated in steps 380 and 420, Pui = Pxi + Pgi + Pbi (i = 1, 2, 3, 4) The target control pressure Pui of the pressure control valve is calculated,
Then proceed to step 440.

In step 440, 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 450.

I ₁ = Ku ₁ Pu ₁ + Kh (Psr-Ps) -Kl · Pd-α I ₂ = Ku ₂ Pu ₂ + Kh (Psr-Ps) -Kl · Pd-α I ₃ = Ku ₃ Pu ₃ + Kh (Psr-Ps ) −Kl ・ Pd I ₄ ＝ Ku ₄ Pu ₄ ＋ Kh (Psr−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 Psr is a reference pressure in the high pressure passage.

In step 450, 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. 13, and Iti = Kt · Ii ( i = 1, 2, 3, 4), and the target current temperature correction calculation is performed, and then the process proceeds to step 460.

In step 460, the current warp (twist amount around the longitudinal axis of the vehicle body) is calculated according to Iw = (It ₁ −It ₂ ) − (It ₃ −It ₄ ), and then the process proceeds to step 470.

In step 470, 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 480.

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

In step 480, the current warp target control amount is calculated according to Eiwp = KiwpEiw with Kiwp as a proportional constant, and then the process proceeds to step 490.

In step 490, the inverse conversion of the current warp is calculated according to the following equation, and then the process proceeds to step 500.

Iw ₁ = Eiwp / 4 Iw ₂ = -Eiwp / 4 Iw ₃ = -Eiwp / 4 Iw ₄ = Eiwp / 4 In step 500, based on the results calculated in steps 450 and 490, the following formula 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 = Iti + Iwi (i = 1, 2, 3, 4) Thus, according to the illustrated embodiment, if an abnormality occurs in the four-wheel steering system, a yes determination is made in step 340, and a step 370 is performed. , The roll gains Kxrf and Kxrr of the displacement feedback control, the gains K ₁ f and K ₁ r of the predicted lateral acceleration change rate of the acceleration feedback control, and the gains K ₂ f and K ₂ r of the lateral acceleration change rate are respectively B. The mode gain is switched and set. Therefore, the ratio of the roll rigidity of the front wheel side to the rear wheel side is increased, and the steer characteristic of the vehicle is shifted in the understeer direction, so that the deterioration of the steering stability due to the abnormality of the four-wheel steering system is suppressed.

Further, according to the embodiment shown in the drawing, the A mode and the B mode are stored for each gain, and these gains can be switched and set by operating the mode changeover switch. Therefore, depending on the preference of the vehicle occupant. The steer characteristics of the vehicle can be changed.

It should be noted that in the above-described embodiment, each gain is calculated in steps 360 and 3
In step 70, the A mode or the B mode is selectively switched and set. However, in order to smoothly perform the switching setting of these gains, each gain is set to B in steps 360 and 370. The gain of the mode may be gradually changed to the gain of the A mode, and the gain of the A mode may be gradually changed to the gain of the B mode.

Although the present invention has been described in detail 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.

As is apparent from the above description, according to the present invention, when an abnormality of the four-wheel steering system is detected, the working fluid supply / discharge means increases the ratio of the roll rigidity of the front wheel side to the rear wheel side. The steering characteristic of the vehicle is shifted in the understeering direction, and the deterioration of the steering stability caused by the inadequate control of the front / rear wheel steering angle ratio is suppressed to improve the vehicle's good running stability. Can be secured.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a fluid circuit of an 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
The graph shows the relationship between the longitudinal acceleration Ga and the target displacement amount Rxp. Fig. 9 shows the relationship between the lateral acceleration Gl and the target displacement amount Rxr. Fig. 10 shows the longitudinal acceleration Ga and the pressure. A graph showing the relationship between the corrected amount Pga and Fig. 11 shows the lateral acceleration Gl.
Fig. 12 is a graph showing the relationship between the pressure and the correction amount Pgl of the pressure. Fig. 13 is a graph showing the relationship between
And FIG. 14 is a graph showing the relationship between the vehicle speed V and the front / rear wheel steering angle ratio K of four-wheel steering. 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 …… Restrictor, 186 …… Electromagnetic on-off valve, 190 …… Solenoid, 192 …… Open / close valve, 196 …… Bypass valve, 197, 198, 199FR, 199FL, 199RR, 199RL …… Pressure sensor, 200 …… electric control device, 202 …… microcomputer, 204 …… CPU, 206 …… ROM, 208 …… RAM, 210 …… input port device, 212 …… output port device, 216 …… IGSW , 220
~ 230 …… Drive circuit, 232 …… Display unit, 234 …… Vehicle speed sensor,
236 …… front and rear G sensor, 238 …… lateral G sensor, 240 …… steering angle sensor, 242 …… four-wheel steering device, 244 …… mode changeover switch, 248 …… vehicle height setting switch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Yonekawa 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor, Kunihito Sato 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor Masaki Kasai 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Takami Sugiyama 2-1, Asahi Town, Kariya City Aichi Prefecture Aisin Seiki Co., Ltd. (72) Inventor Ogawa Nobuyuki 2-chome, Asahi-cho, Kariya city, Aichi, Aisin Seiki Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. A fluid pressure type active suspension of a vehicle equipped with a four-wheel steering system, a fluid pressure actuator arranged between each wheel and a vehicle body, and a working fluid for supplying and discharging a working fluid to and from the actuator. An abnormality of the four-wheel steering device is detected, and a supply / discharge means, a control means for controlling the roll rigidity on the front wheel side and the rear wheel side by controlling the working fluid supply / discharge means in accordance with the traveling state of the vehicle. Means for increasing the ratio of the roll rigidity of the front wheel side to the rear wheel side when the abnormality of the four-wheel steering device is detected, the fluid pressure type active suspension.