JPH04328010A - Fluid pressure type active suspension - Google Patents

Abstract

PURPOSE:To control the posture of an automobile body appropriately without over-control or under-control in accordance with changes of the acceleration of the body, irrespective of the pressure in a gas-liquid spring. CONSTITUTION:An active suspension is provided with an actuator 36, a gas- liquid spring 42 connected to the actuator, a pressure control valve 22 supplying/ discharging operating fluid to/from the actuator, a pressure sensor 68 for detecting the pressure in the gas-liquid spring 42, a sensor for detecting or estimating the acceleration of an automobile body, and a control device for computing the change rate of the acceleration and controlling the pressure control valve in accordance with a control amount based on the change rate of the acceleration. The control device is composed so that the control amount based on the change rate of acceleration decreases as the pressure in the gas- liquid spring increases.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to suspensions for vehicles such as automobiles, and more particularly to hydraulic active suspensions.

0002

2. Description of the Related Art As one type of hydraulic active suspension for vehicles such as automobiles, for example, Japanese Patent Laid-Open No. 2-274
As described in Publication No. 606, an actuator is provided corresponding to each wheel and increases or decreases the vehicle height of the corresponding part by supplying and discharging working fluid to a working fluid chamber;
A working fluid supply/discharge means for supplying and discharging working fluid to and from the working fluid chamber, a longitudinal acceleration detecting means for detecting the longitudinal acceleration of the vehicle body, a lateral acceleration detecting means for detecting the lateral acceleration of the vehicle body, and an estimation of the lateral acceleration of the vehicle body. A means for determining the rate of change of the displacement, a control amount proportional to longitudinal acceleration, a control amount based on the change rate of longitudinal acceleration, a control amount proportional to lateral acceleration, a control amount based on the change rate of lateral acceleration, and a change in estimated lateral acceleration. A hydraulic active suspension is already known which has a control device that performs feedforward control of a working fluid supply/discharge means by PD compensation using a control amount based on a control amount.

According to such an active suspension, not only a control amount proportional to the longitudinal acceleration and a control amount proportional to the lateral acceleration of the vehicle body, but also a control amount based on the change rate of the longitudinal acceleration and a control amount based on the change rate of the lateral acceleration are provided. Since the working fluid supply and discharge means is controlled by a control amount based on the rate of change of the estimated lateral acceleration, it is possible to effectively control not only the roll of the vehicle body during steady turns but also the roll of the vehicle body during transient turns. .

0004

[Problems to be Solved by the Invention] However, as described above, in an active suspension that performs feedforward control of the pressure in the working fluid chamber of the actuator in accordance with a control amount proportional to acceleration and a rate of change in acceleration, as shown in FIG. As shown in the figure, the response frequency of the active suspension changes depending on the pressure Pi within the gas-liquid spring device. Further, the elasticity of the gas-liquid spring device changes non-linearly as the pressure inside the gas-liquid spring device changes, as shown in FIG. 7, due to the nature of gas polytrope changes. Since the pressure in the actuator's working fluid chamber fluctuates over a relatively wide range, if feedforward control is performed using linear PD compensation without considering the nonlinearity described above, the actual feed to the actuator's working fluid chamber will vary. The forward control amount does not reach an appropriate value, which may cause the vehicle to heave up or roll.

For example, the standard pressure in the working fluid chambers of the left and right actuators (pressure when the vehicle is stationary)
When the linear PD feedforward control amount is tuned according to the nearby dynamic characteristics (responsiveness of the active suspension), when a transient turn with high lateral acceleration is performed in that state, the actuator on the outer wheel side of the turn The pressure in the working fluid chamber increases, resulting in an overresponse to PD compensation, and conversely, the actuator on the inner wheel side of the turn becomes insufficient in response to PD compensation, as the pressure in its working fluid chamber decreases. As a result, as shown by the broken line in the time chart of Fig. 8, the vehicle height increases on both the outer wheel and the inner wheel of the turn, resulting in a heave-up in which the vehicle height of all four wheels increases. Or, the vehicle body may roll due to a difference in the amount of increase in the left and right vehicle heights.

In view of the above-mentioned problems in conventional hydraulic active suspensions, the present invention appropriately adjusts the posture of the vehicle body in accordance with changes in acceleration of the vehicle body, regardless of the pressure within the gas-liquid spring device. The objective is to provide an improved hydraulic active suspension that can be controlled.

[0007]

[Means for Solving the Problems] According to the present invention, the above-mentioned object is achieved by supplying and discharging a working fluid to a working fluid chamber provided corresponding to each wheel, thereby increasing the vehicle height of the corresponding portion. an actuator that increases and decreases; a gas-liquid spring device that communicates with the working fluid chamber; a working fluid supply/discharge means that supplies and discharges working fluid to and from the working fluid chamber; and a pressure within the gas-liquid spring device or equivalent thereto. pressure detection means for detecting a state quantity;
The vehicle comprises an acceleration detection means for detecting or estimating the acceleration of the vehicle body, and a control device for calculating a rate of change in the acceleration and controlling the working fluid supply/discharge means in accordance with a control amount based on the rate of change in the acceleration. The control device is achieved by a hydraulic active suspension configured to reduce the control amount based on the rate of change of acceleration as the pressure detected by the pressure detection means increases.

[0008]

[Operation] According to the above configuration, the control device is configured to reduce the control amount based on the rate of change of acceleration as the pressure detected by the pressure detection means is higher, and therefore the pressure in the gas-liquid spring device is reduced. The higher the value, the smaller the control amount based on the rate of change in acceleration, and conversely, the lower the pressure in the gas-liquid spring device, the more the control amount based on the rate of change in acceleration.

Therefore, when the pressure inside the actuator's working fluid chamber is high, the resulting excessive control is offset or suppressed by a decrease in the control amount based on the rate of change in acceleration, and conversely, when the pressure inside the actuator's working fluid chamber is low, In this case, the lack of control caused by this is offset or suppressed by an increase in the control amount based on the rate of change of acceleration, so that the pressure in the actuator's working fluid chamber can be properly fed forward regardless of the pressure in the gas-liquid spring device. It is controlled by a control amount, and the attitude of the vehicle body is appropriately controlled according to changes in the acceleration of the vehicle body.

[0010] The invention will now be described in detail by way of example with reference to the accompanying drawings.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram showing a fluid circuit of one embodiment of a hydraulic active suspension according to the present invention.

In FIG. 1, reference numeral 10 indicates a reservoir for storing oil as a working fluid. One end of a connection passage 12 and one end of a working fluid discharge passage 14 are connected to the reservoir 10 . The other end of the connecting passage 12 is connected to the suction side of a pump 18 driven by an engine 16. Pump 18 is a variable displacement pump in the illustrated embodiment, and one end of working fluid supply passage 20 is connected to its discharge side. The other end of the working fluid supply passage 20 and the other end of the working fluid discharge passage 14 are connected to the P port and the R port of a pilot-operated 3-port 3-position switching control valve 24 of the pressure control valve 22, respectively. There is. A check valve 15 is provided in the middle of each working fluid discharge passage 14 on the side closer to the pressure control valve 22 than the communication connection part 14a with the working fluid discharge passage from other wheels, and this check valve Only the flow of working fluid from the control valve 22 toward the reservoir 10 is allowed.

The pressure control valve 22 consists of a switching control valve 24, a connection passage 26 that communicates and connects the working fluid supply passage 20 and the reservoir 10, and a fixed throttle 28 and a variable throttle 30 provided in the middle of the passage. ing. A of the switching control valve 24
A connection passage 32 is connected to the port. The switching control valve 24 is a spool valve that takes in the pressure Pp in the passage 26 between the fixed throttle 28 and the variable throttle 30 and Pa in the connecting passage 32 as pilot pressure, and when the pressure Pp is higher than the pressure Pa, the port P and port A are switched to the switching position 24a for communicating and connecting the pressures Pp and P.
When a are equal to each other, the switch is switched to the switching position 24b which cuts off communication between all ports, and Pp becomes the pressure Pa.
When it is lower, it is switched to a switching position 24c that connects port R and port A in communication. Further, the variable throttle 30 changes the effective passage cross-sectional area of the throttle by controlling the current applied to its solenoid, thereby changing the pressure Pp in cooperation with the fixed throttle 28. Note that a throttle 34 is provided in the middle of the passage for guiding the pilot pressure.

The other end of the connecting passage 32 is connected to a working fluid chamber 38 of an actuator 36 provided corresponding to the wheel. As shown in the figure, the actuator 36 is a type of cylinder-piston device, and although not shown in the figure, it is disposed between the suspension member that supports the wheels and the vehicle body, and supplies and discharges working fluid to and from the working fluid chamber 38. By doing so, the vehicle height of the corresponding area can be increased or decreased. A gas-liquid spring device 42 is connected to the working fluid chamber 38 via a passage 40.
are connected to each other, and a throttle 44 is provided in the middle of the passage 40. The gas-liquid spring device 42 is provided with a pressure sensor 45 that detects the pressure within the gas-liquid spring device. The gas-liquid spring device 42 thus acts as a suspension spring or an auxiliary suspension spring, and the restriction 44 is adapted to generate a damping force.

A cutoff valve 46 is provided in the middle of the connection passage 32. Shutoff valve 46 is connected to pilot pressure control device 48
The valve is configured to take in a pilot pressure Pc controlled by the above, open when the pilot pressure Pc exceeds a predetermined valve opening value, and close when the pilot pressure falls below a predetermined valve closing value. The pilot pressure control device 48 is a connecting passage 5 that communicates and connects the working fluid supply passage 20 and the reservoir 10.
0, a fixed throttle 52 and a variable throttle 54 provided in the middle of the passage, and the pressure between the fixed throttle and the variable throttle is supplied to the cutoff valve 46 as pilot pressure Pc.

A check valve 58 is provided in the middle of the working fluid supply passage 20 to allow only the flow of working fluid from the filter 56 and the pump 18 toward the pressure control valve 22. Further, an accumulator 60 is connected to the working fluid supply passage 20 on the downstream side of the check valve 58 .

A check valve 15, a pressure control valve 22, a connecting passage 32, a throttle 44, a cutoff valve 46, an actuator 36, a gas-liquid spring device 42, a pressure sensor 45, etc. are provided corresponding to each wheel. In addition, in FIG. 2, the pressure control valves and pressure sensors corresponding to the right front wheel, left front wheel, right rear wheel, and left rear wheel are 22fr, 22fl, 22rr, 22rl, and 4, respectively.
5fr, 45fl, 45rr, and 45rl.

Pressure control valve 22 is controlled by an electrical control device 76 shown in FIG. Electrical control device 76 includes a microcomputer 78 . The microcomputer 78 may have a general configuration as shown in FIG.
A CPU) 80, a read-only memory (ROM) 82, a random access memory (RAM) 84, an input port device 86, and an output port device 88, which are connected to each other by a bidirectional common bus 90. There is.

The input port device 86 receives the lateral acceleration Gx (
A signal indicating the longitudinal acceleration Gy of the vehicle body (with the front direction of the vehicle being positive) from the longitudinal acceleration sensor 64, and a corresponding gas-liquid spring device 42 from the pressure sensors 45fr to 45rl. The pressure inside Pfr, Pfl, P
rr, Prl, a signal indicating the vehicle speed V from the vehicle speed sensor 70, a signal indicating the steering angle θ (with the right turning direction being positive) from the steering angle sensor 72, and a group of sensors such as a vehicle height sensor. A signal related to the running state of the vehicle is inputted from the sensor 74.

[0020] The input port device 86 appropriately processes the signals input thereto, and according to the instructions of the CPU 80 based on the program stored in the ROM 82, the CPU and RAM
The processed signal is output to 84. R
The OM 82 stores control programs, maps shown in FIGS. 4 and 5, and the like. The CPU 80 is designed to perform various calculations and signal processing as described later based on the signal flow shown in FIG. 3 regarding the roll and pitch control of the vehicle body. The output port device 88 outputs a control signal to the variable throttle 54 of the pilot pressure control device 48 via the drive circuit 92 according to instructions from the CPU 80, and outputs a control signal to the variable throttle 54 of the pilot pressure control device 48 via the drive circuits 94 to 97 to the pressure control valves 22fr, 22rl, 22rr, 22r.
A control signal is output to the corresponding variable diaphragm.

Control by the control device 76 is initiated by closing an ignition switch (not shown);
It ends a while after the ignition switch is opened. Further, at the start of operation of the active suspension, the pilot pressure control device 48 is controlled to gradually increase the pilot pressure Pc, thereby gradually opening the shutoff valve 46 until it is fully open. If necessary, for details of such control, please refer to, for example, Japanese Patent Application No. 199883 filed by the same applicant as one of the applicants of this application.

Next, the signal flowchart of FIG. 3 and FIG.
The operation of the illustrated embodiment will be described with reference to the flowchart of FIG. 5 and the maps of FIGS. 5 and 6.

As shown in FIG. 3, the lateral acceleration Gx of the vehicle body detected by the lateral acceleration sensor 62 and the longitudinal acceleration Gy of the vehicle body detected by the longitudinal acceleration sensor 64.
High frequency components are removed by low-pass filters 100 and 102, respectively, and the filtered lateral acceleration and longitudinal acceleration are multiplied by preset tuning gains by coefficient multipliers 104 and 106, respectively.

The lateral acceleration and longitudinal acceleration multiplied by the tuning gain are input to each wheel converter 108, and the converter converts the roll stiffness distribution ratio of the front wheels into Kfg (a positive constant less than 1) in the matrix shown in the figure. It is converted into acceleration signals for controlling the actuators of the right front wheel, left front wheel, right rear wheel, and left rear wheel. The lateral acceleration multiplied by the tuning gain is further multiplied by the tuning gain by a coefficient unit 110, and then inputted to the converter 112 for each wheel.
It is converted into an acceleration signal for controlling the left rear wheel actuator.

The acceleration signals from each wheel transducer 108 and 112 are input to the plus terminal and minus terminal of an adder 114, respectively, and the output thereof is supplied to a differentiator 116.
The difference with the output of the adder 114 n1 cycles ago is calculated as a time differential value by the differentiator. Differentiator 116
The output is multiplied by a tuning gain by a coefficient unit 118 and then input to an adder 120 .

The steering angle θ detected by the steering angle sensor 72 is differentiated by a differentiator 122 to obtain a steering angular velocity θd.
ot is calculated, and based on the steering angular velocity θdot and the vehicle speed V detected by the vehicle speed sensor 70, the estimator 124 calculates the differential value Ghd of the estimated lateral acceleration of the vehicle body from a map corresponding to the graph of FIG. The output of the estimator 124 is multiplied by a tuning gain by a coefficient unit 126, and then input to each wheel converter 128, which converts the roll stiffness distribution ratio of the front wheels into a matrix shown in the figure as Ksg (a positive constant less than 1). Right front wheel, left front wheel, right rear wheel,
The signal is converted into a signal for controlling the actuator of the left rear wheel, and is further input to the adder 120.

[0027] Also, pressure sensors 45fr, 45fl, 45
Signals indicating the pressures Pfr, Pfl, Prr, and Prl in each gas-liquid spring device detected by rr and 45rl are input to the gain calculator 130, and the gain calculator 130 calculates the pressures based on the map corresponding to the graph shown in FIG. The weight gain Kdf is
r, Kdfl, Kdrr, and Kdrl are calculated, and their values are output to the coefficient unit 134.

A map corresponding to the graph shown in FIG. 5 is provided for each wheel, and in FIG. 5, i is fr corresponding to the right front wheel, left front wheel, right rear wheel, and left rear wheel. ,fl,rr
, rl, and Poi means the pressure (standard pressure) in the working fluid chamber of the actuator when the vehicle is at rest. In the illustrated embodiment, the gain Kdi is equal to the pressure Pi
is set to be 1 when is the standard pressure Poi.

The output of the adder 120 is multiplied by a gain Kdi by a coefficient unit 134, and the output of the coefficient unit 134 and the output of each wheel converter 108 are added by an adder 132. A feedforward control amount based on the acceleration of is calculated.

[0030] Target pressures in the working fluid chambers of each actuator for controlling the posture of the vehicle body and ride comfort of the vehicle according to the running condition of the vehicle, and pressure control valves 22fr, 22fl for achieving these target pressures. , 22rr, 22r
The control current supplied to the solenoid of the variable throttle of l is controlled at a rate of change of the actual acceleration of the vehicle body or of the estimated acceleration so that roll of the vehicle body during transient turns and pitching of the vehicle body during acceleration/deceleration are reduced or prevented. It may be implemented in any manner as long as the pressure control valve is controlled according to the rate of change.
For example, it may be carried out as described in Japanese Patent Laid-Open No. 2-175405 filed by the same applicant as one of the applicants of the present application.

Thus, according to this embodiment, the difference device 11
The rate of change (differential value) of lateral acceleration and the rate of change of longitudinal acceleration calculated by 6 and multiplied by the gain by the coefficient unit 118, and the rate of change of the longitudinal acceleration estimated by the estimator 124, multiplied by the gain by the coefficient unit 126, and calculated by the converter 128 for each wheel. and the rate of change of the estimated lateral acceleration distributed to are added by an adder 120,
The output is multiplied by a gain Kdi by a coefficient unit 134, and the output is added by an adder 132 to a control amount proportional to the lateral acceleration and a control amount proportional to the longitudinal acceleration,
The addition result is output as a feedforward control amount based on the acceleration of the vehicle body relative to the pressure control valve of each wheel.

In this case, the gain Kdi is set to be smaller as the pressure Pi in the gas-liquid spring device increases as shown in FIG. The higher the pressure in the spring device, the lower the value; conversely, the lower the pressure Pi, the higher the value.

Therefore, for example, when a vehicle turns, excessive control due to an increase in the pressure in the gas-liquid spring device 42 on the outer wheel side of the turn causes the control amount based on the rate of change of the actual lateral acceleration and the rate of change of the estimated lateral acceleration to be reduced. On the inside wheel side of the turn, the lack of control caused by the decrease in the pressure in the gas-liquid spring device is offset or suppressed by the decrease in the control amount based on the rate of change of the actual lateral acceleration. This is offset or suppressed by an increase in the control amount based on the rate of change of the lateral acceleration, so that the pressure in the actuator fluid chamber 38 of the actuator 36 is controlled by an appropriate feedforward control amount regardless of the pressure in the gas-liquid spring device. As a result, heave-up and roll of the vehicle body during transient turns, as shown by the solid line in FIG. 8, can be avoided.

Similarly, when the vehicle accelerates or decelerates, excessive control due to an increase in the pressure within the gas-liquid spring device 42 is offset or suppressed by a decrease in the control amount based on the rate of change in longitudinal acceleration, and the air pressure is reduced. The lack of control caused by a decrease in the pressure inside the gas-liquid spring device is offset or suppressed by an increase in the control amount based on the rate of change in the longitudinal acceleration, and this allows the actuator to operate regardless of the pressure inside the gas-liquid spring device. 3
The pressure within the working fluid chamber 38 of No. 6 is controlled by an appropriate feedforward control amount, thereby avoiding pitching of the vehicle body during acceleration and deceleration.

In the above-described embodiment, the feedforward control amount based on both the rate of change in lateral acceleration and the rate of change in estimated lateral acceleration is increased or decreased in accordance with the pressure within the gas-liquid spring device. However, only the feedforward control amount based on one of these may be increased or decreased depending on the pressure within the gas-liquid spring device.

Further, in the above embodiment, the gain Kdi
is set as a gain for the sum of the feedforward control amount based on the rate of change in longitudinal acceleration, the feedforward control amount based on the rate of change in lateral acceleration, and the feedforward control amount based on the rate of change in estimated lateral acceleration. However, gains are set individually for the control amount based on the rate of change in longitudinal acceleration, the control amount based on the rate of change in lateral acceleration, and the control amount based on the rate of change in estimated lateral acceleration. It may be set so that the higher the internal pressure, the lower the pressure.

Furthermore, in the above-described embodiment, the feedforward control amount based on the rate of change in longitudinal acceleration is also increased or decreased in accordance with the pressure within the gas-liquid spring device. The feedforward control amount based on the gas-liquid spring device does not have to be increased or decreased depending on the pressure inside the gas-liquid spring device, and the vertical acceleration of the vehicle body is detected, and the feedforward control amount based on the vertical acceleration also depends on the pressure inside the gas-liquid spring device. It may be increased or decreased depending on the situation.

Further, in the above embodiment, the pressure Pi in the gas-liquid spring device is directly detected by the pressure sensors 45fr to 45rl, but the pressure in the working fluid chamber of the actuator is detected. It may be estimated from the detection results of a pressure sensor or the detection results of a lateral acceleration sensor and a longitudinal acceleration sensor.

Furthermore, in the embodiments described above, the means for controlling the pressure within the working fluid chamber of each actuator is a pressure control valve, but this means may also be a flow rate control valve.

Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited to such embodiments, and various other embodiments may be made within the scope of the present invention. It will be obvious to those skilled in the art that this is possible.

[0041]

As is clear from the above explanation, according to the present invention, the higher the pressure inside the gas-liquid spring device, the smaller the control amount based on the rate of change in acceleration; As the pressure decreases, the amount of control based on the rate of change in acceleration increases, so if the pressure in the working fluid chamber of the actuator is high, the overcontrol caused by this is offset or suppressed by a decrease in the amount of control based on the rate of change in acceleration. Conversely, when the pressure in the working fluid chamber of the actuator is low, the lack of control caused by this is offset or suppressed by an increase in the amount of control based on the rate of change in acceleration, so that regardless of the pressure in the gas-liquid spring device. By controlling the pressure in the working fluid chamber of the actuator with an appropriate feedforward control amount, it is possible to appropriately control the attitude of the vehicle body in accordance with changes in the acceleration of the vehicle body.

[Brief explanation of drawings]

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

FIG. 2 is a block diagram showing the electrical control device of the embodiment shown in FIG. 1;

FIG. 3 is a signal flowchart showing the calculations and signal processing accomplished by the electrical control device shown in FIG. 2;

FIG. 4 is a graph showing the relationship between the vehicle speed V, the differential value θdot of the steering angular velocity, and the differential value Ghd of the estimated lateral acceleration.

FIG. 5 is a graph showing the relationship between the pressure Pi in the gas-liquid spring device and the gain Kdi.

[Figure 6] Frequency and active suspension response (
2 is a graph showing the relationship between the control current Ii supplied to the control valve and the pressure Pi within the gas-liquid spring device.

FIG. 7 is a graph showing the relationship between the pressure within the gas-liquid spring device and the elasticity of the gas-liquid spring device.

FIG. 8 is a time chart showing changes in the vehicle height of the left and right front wheels when a vehicle equipped with a conventional active suspension runs in a slalom at high lateral acceleration.

[Explanation of symbols]

10...Reservoir 16...Engine 18...Pump 20... Working fluid supply passage 22...Pressure control valve 32...Connection passage 36...actuator 38... Working fluid chamber 42...Air-liquid spring device 44...Aperture 45...Pressure sensor 46...Shutoff valve 48...Pilot pressure control device 60...Accumulator 62...Lateral acceleration sensor 64...Longitudinal acceleration sensor 70...Vehicle speed sensor 72...Steering angle sensor 76...Electric control device 78...Microcomputer 80...CPU 82...ROM 84...RAM 86...Input port device 88...Output port device

Claims (1)

[Claims] an actuator that is provided corresponding to each wheel and increases or decreases the vehicle height of the corresponding portion by supplying and discharging a working fluid to a working fluid chamber; a gas-liquid spring device that communicates with the working fluid chamber; A working fluid supply/discharge means for supplying and discharging a working fluid to and from the chamber, a pressure detecting means for detecting the pressure in the gas-liquid spring device or a state quantity equivalent thereto, and an acceleration detecting means for detecting or estimating the acceleration of the vehicle body. and a control device that calculates the rate of change of the acceleration and controls the working fluid supply/discharge means according to a control amount based on the rate of change of the acceleration,
The control device is a hydraulic active suspension configured to reduce a control amount based on the rate of change of the acceleration as the pressure detected by the pressure detection means increases.