JPH0238121A - Suspension device for vehicle - Google Patents

Abstract

PURPOSE:To ensure the proper physical feeling of a drop in cornering boundary by setting the lateral acceleration at a low level when one of conditions to determine the cornering boundary changes toward a direction for causing a drop in the boundary. CONSTITUTION:A body 11 is provided with a plurality of hydraulic cylinders 12 and the piston rod 15 in each thereof retains each wheel 10. Also, each hydraulic chamber 14 thereof is communicated with a gas spring 21. In addition, each of high-pressure pipes 31F and 31R is connected to the hydraulic cylinder 12, thereby supplying and discharging a hydraulic fluid via control with a control unit 45. In this case, the control unit 45 controls the supply and discharge of the hydraulic fluid so that the roll angle of a body will be positive when the lateral acceleration of the body detected with a sensor 61 is equal to or more than the predetermined value. Furthermore, when at least one of conditions to determine a cornering boundary changes toward the drop thereof, the aforesaid predetermined value is made to drop following the change.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a suspension system for a vehicle, and more particularly, to a suspension system for a vehicle, by supplying and discharging working fluid to and from a cylinder installed between the vehicle body and the wheels. The present invention relates to a suspension device that controls roll angle.

(Prior art) For example, as shown in Japanese Patent Publication No. 59-14385, a cylinder is installed between the vehicle body and the wheels, and the vehicle height can be adjusted freely by controlling the supply and discharge of working fluid to the cylinder. Modifiable vehicle suspension systems are known. In the suspension device configured in this way, it is also possible to freely control the vehicle body roll angle when the vehicle turns. In other words, by supplying working fluid to the outer cylinder during a turn, or conversely discharging the working fluid from the inner cylinder (of course, these operations may also be performed at the same time), the vehicle height of the outer wheel can be reduced. It is also possible to make the wheels higher than the inner wheels to apply a so-called reverse roll, in which the vehicle body leans toward the center of the turn.

In addition, as mentioned above, by changing the supply and discharge of working fluid between the inner cylinder and the outer cylinder, the roll angle can be freely controlled, such as zero or even positive roll. becomes possible.

When controlling the vehicle body roll angle as described above, if a relatively large force is applied in the lateral direction of the vehicle body, the roll angle will be positive, and the roll angle will be controlled so that it increases as the force increases. is common. In other words, by doing this, the driver will have the same experience as when driving a vehicle with a general suspension system that does not perform roll angle control, and will be able to reach the cornering limit, that is, the lateral force that can be safely turned. You will be able to feel the upper limit. Such control includes an acceleration sensor that detects the lateral acceleration of the vehicle body, and an acceleration sensor that receives the output of this sensor and adjusts the vehicle body roll angle to a positive value when the acceleration is equal to or greater than a predetermined value. supply of working fluid to the cylinder;
This can be realized by including a controller that controls discharge.

(Problem to be Solved by the Invention) By the way, the cornering limit varies not only by the centrifugal force acting on the vehicle body, but also by the condition of the road surface, the loading condition of the vehicle, and even the condition of the tires. If the roll angle is controlled only based on the acceleration detected by the sensor, the vehicle may roll in the opposite direction even though it is close to the cornering limit, or the roll angle may be zero, making it difficult for the driver to feel the cornering limit. The problem arises that there is no.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a suspension device for a vehicle that can solve such problems.

(Means for Solving the Problems) A suspension device for a vehicle according to the present invention supplies a working fluid to a cylinder installed between a vehicle body and a wheel.
By discharging the vehicle, the vehicle height is changed, and the vehicle is equipped with an acceleration sensor and a controller as described above, and roll angle control is performed so that a positive roll occurs when the acceleration in the lateral direction of the vehicle body exceeds a predetermined value. In the suspension system, a detection means is provided for detecting at least one condition that determines the cornering limit, such as the aforementioned road surface condition, and inputting a signal indicating the condition to the controller, and the controller is configured to detect at least one condition that determines the cornering limit, such as the road surface condition described above, The present invention is characterized in that the predetermined value is modified to a smaller value when the value changes in the lowering direction.

(Function) In the above configuration, if the cornering limit is lowered depending on the road surface condition, etc., a positive roll will be applied while the lateral force is still small, and the driver will feel that the cornering limit is lower. become able to.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 2 shows a suspension system for a vehicle according to an embodiment of the present invention, and FIG. 1 shows a hydraulic circuit used in this suspension system. In addition, in the figure,
The main elements corresponding to the right front wheel, left front wheel, right rear wheel, and left rear wheel are numbered rFRJ rFLJ, respectively.
The symbols rRRJ and rRLJ are shown with added symbols, but in the following explanation, those symbols will be added only when it is particularly necessary.

As shown in FIG. 2, a hydraulic cylinder 12 is fixed to the vehicle body 11 for each wheel, and a hydraulic chamber j4 is defined by a piston 13 that is slidably inserted into the hydraulic cylinder 12. has been done. A piston rod 15 integrated with the piston 13 holds a wheel 1o. A gas spring 21 is communicated with the hydraulic pressure chamber 14 via a hydraulic passage. The gas spring 2I has a gas chamber 25 defined by a diaphragm 23 as a movable partition wall and a liquid chamber 27, and the liquid chamber 27 is communicated with the hydraulic pressure chamber 14. In addition, as shown in detail in FIG. 1, in this embodiment, the gas spring 21
Two of them are provided on each circumference, and they are connected to the hydraulic cylinder 12 in a parallel relationship with each other. An orifice 29 is provided in each of the hydraulic passages 18 that communicate with each of these gas springs 21 . The unit consisting of such a combination of the hydraulic cylinder 12, the gas spring 21, and the orifice 29 has a basic function as a suspension device, with the buffering action of the gas spring 21 and the damping action of the orifice 29. Become.

The above-mentioned hydraulic cylinder 12 has a high pressure pipe 31F or 3
1R is connected, and hydraulic fluid is supplied to and discharged from the hydraulic cylinder 12 through this piping.

A hydraulic circuit for supplying and discharging this hydraulic fluid will be described below with reference to FIG. 1. The vane pump 32 driven by the engine pumps up the hydraulic fluid 44 from the reservoir tank 33 and pumps the hydraulic fluid 44 through the common high-pressure pipe 34 to the high-pressure pipes 31F and 31H for the front wheels and the rear wheels. The common high pressure pipe 34 is provided with a filter 35, a check valve 3B, a main accumulator 37 for accumulating pressure, and a hydraulic pressure gauge 38 in this order from the upstream side. Further, in the pump 32, an in-pump relief valve 30 is provided that circulates the discharged hydraulic fluid 44 to the suction side when the discharge side pressure increases abnormally.

The high pressure pipe 31F for the front wheel is the high pressure pipe 81FR1 for the right front wheel.
It is branched into a high-pressure pipe 31FL for the left front wheel, and these pipes 3LF R and 'alF L are communicated with the respective hydraulic pressure chambers 14 of the front right wheel hydraulic cylinder 12FR and the front left wheel hydraulic pressure cylinder 12FL, respectively. Further, a pilot passage 39F branches off from the high pressure pipe 31F, and this pilot passage 89F is connected to a front wheel electromagnetic on-off valve 50F.

The high-pressure piping 31FH for the right front wheel includes, in order from the upstream side, a pressure guarantee valve 51FR, a flow control valve 52FR, a pressure-operated on-off valve 53FR, and a relief valve 54FR.

A hydraulic pressure gauge 55FR is provided. On the other hand, a pressure guarantee valve 51FL is also installed in the high pressure piping 31FL for the left front wheel from the upstream side.
, flow rate control valve 52FL, pressurized on-off valve 53'FL,
A relief valve 54FL and a hydraulic pressure gauge 55FL are provided. Further, the pilot passage 39F on the downstream side of the above-mentioned electromagnetic on-off valve 50F is branched into two systems, one for each operating pressure inlet 58FR1 for each pressure-operated on-off valve 53F R, 53F L.
Connected to 56FL. and relief valve 54F
Each of the relief ports R, 54F and L is connected to the reflux pipe 40F. Further, the hydraulic fluid return ports of the pressure guarantee valves 51FR, 51FI and the electromagnetic on-off valve 50F are also connected to the above-mentioned return pipe 40F. A return accumulator 59F that performs a pressure accumulating function is attached to this recirculation passage 40F.

Exactly the same elements as the front wheel elements described above are also provided on the rear wheel high pressure pipe 31R side. In FIG. 1, the front wheel element and the rear wheel element, which are equivalent to each other, are distinguished by the symbols rFJ and rRJ added next to their respective numbers.

The front wheel side reflux pipe 40F and the rear wheel side reflux pipe 40R are connected to a common reflux pipe 41 that reaches the reservoir tank 33. The common reflux pipe 41 and the common high pressure pipe 34 are communicated through a relief pipe 42, and an unload relief valve 43 is interposed in the relief pipe 42.

Next, the operation of the suspension device having the above configuration will be explained. The operations of the unload relief valve 43, the electromagnetic on-off valve 50, and the flow rate control valve 52 are controlled by a control unit 45 (see FIG. 2) consisting of, for example, a microcomputer. This control unit 45 includes the hydraulic pressure gauge 38, a hydraulic pressure gauge 55 provided for each hydraulic cylinder 12, and each wheel 10FR, 10FL, 10RR, 1
an acceleration sensor 57 that detects the springboard speed every 0RL;
Similarly, each wheel is 10FR.

A vehicle height sensor 58 that detects the vehicle height (that is, cylinder stroke) every 10FL, 10RR, and 10RL, a road surface condition sensor 60 that detects the approximate friction coefficient of the road surface, and a lateral acceleration that detects the lateral acceleration applied to the vehicle body 11. The output of the sensor 61 is input (in Fig. 2, the oil pressure gauge 5
5. Regarding the acceleration sensor 57 and vehicle height sensor 58, only those corresponding to the left rear wheel LORL are shown).

As the road surface condition sensor BO, for example, one that emits light towards the road surface and performs the above detection based on the intensity of the reflected light is used, and in this embodiment, the road surface friction coefficient is relatively small or large. A device is used that detects whether

First, the control unit 45 controls the electromagnetic on-off valve 5.
0 is closed, the hydraulic fluid 44 flowing through the pilot passage 39 is returned to the recirculation passage 40 at this electromagnetic on-off valve 50 even if the pump 32 and the like are operating normally.

Pressure-operated on-off valve 53 connected to pilot passage 39
is normally kept closed and opens only when a predetermined operating pressure is received at the operating pressure receiving port 56. Therefore, when the supply of the hydraulic fluid 44 to the working pressure receiving port 5B is cut off as described above, it is in the closed state. In this way, the on-off valve 53
When closed, the suspension device exhibits properties based on the elastic modulus of the gas spring 21 and the throttling resistance of the orifice 29. That is, this suspension device becomes a so-called passive suspension.

On the other hand, when the electromagnetic on-off valve 50 is opened by the control unit 45 while the bomb 32 etc. are operating normally, the pressure of the hydraulic fluid 44 is applied to the operating pressure inlet 56 of the pressurized on-off valve 53. This opens the on-off valve 53. In this way, when the on-off valve 53 is opened and the flow rate control valve 52 is opened to the opening specified by the control unit 45, for example, when the piston 13 is displaced upward (to the left in FIG. 1), When the hydraulic fluid 44 is supplied into the hydraulic cylinder 12, the supplied hydraulic fluid 4
As a result of the movement of the piston 13 being suppressed by 4, the dynamic spring constant of the suspension device changes in the direction of increasing. By supplying and discharging the hydraulic fluid into the hydraulic cylinder I2 in this way, the throttle resistance of the orifice 29 and the gas spring 2
The same effect as changing the elastic modulus of 1 is obtained, and the suspension device functions as a so-called active suspension device. It is also possible to control the vehicle height for each axis by controlling the amount of hydraulic fluid in the hydraulic cylinder 12.

As described above, the control unit 45 includes a hydraulic pressure gauge 55 provided for each hydraulic cylinder 12, an acceleration sensor 57 provided for each axis layer, a vehicle height sensor 58, a road surface condition sensor 60, and a lateral acceleration sensor 61. The cylinder internal pressure, sprung boat speed, vehicle height, road friction coefficient (
The supply and discharge of the hydraulic fluid 44 is controlled based on whether the hydraulic fluid 44 is relatively small or large) and the lateral acceleration. Further, when the pressure in the high pressure pipe 34 indicated by the system oil pressure gauge 38 exceeds a set value, the control unit 45 opens the unload relief valve 43. As a result, the hydraulic fluid 44 is returned to the reservoir tank 33, and an abnormal rise in pressure within the high pressure pipe 34 is prevented.

Next, roll angle control of the vehicle body 11 will be explained.

When the lateral acceleration sensor 61 detects acceleration in the left-right direction of the vehicle body, that is, when the vehicle is turning, the control unit 45 activates the two hydraulic cylinders 12 (1) on the outer wheel side.
2FR and 12RR, or 12FL and 12RL), a large amount of hydraulic fluid 44 is supplied to make the vehicle height on the outside higher than that on the inside. Thereby, it is possible to apply a so-called reverse roll in which the vehicle body 11 leans toward the turning center, contrary to the conventional general suspension device. In such a reverse roll state, the center of gravity of the vehicle moves toward the center of turning, so the steering stability is improved compared to a normal roll state.

However, as shown in FIG. 3A, for example, the control unit 45 controls the supply and discharge of the hydraulic fluid 44 so that the above-mentioned reverse roll is applied only in a region where the lateral acceleration is relatively small. The roll angle control characteristics shown in FIG. 3A are realized when the road surface condition sensor 60 detects that the road surface friction coefficient is relatively large, and the lateral acceleration is about 0.
Below 3G, it is a reverse roll, when about 0.3 to 0.4G, the roll angle is zero, and when it is about 0.4G or more, it is a normal roll. In this way, when the lateral acceleration is large, a positive roll is performed, and as the acceleration increases, the positive roll angle is You will get a feeling similar to that of driving a new vehicle, and you will be able to feel the cornering limits.

On the other hand, the control unit 45 includes a road surface condition sensor 60
If it is detected that the road surface friction coefficient is relatively small, the lateral acceleration versus roll angle control characteristics are changed as shown in FIG. 3B. In other words, in this case, the lateral acceleration is approximately 0.2
This is a positive roll. If the road surface friction coefficient is small, the cornering limit is low, so in this case, by shifting the positive roll area as described above, the driver can experience positive roll from a time when the lateral acceleration is lower, indicating that the cornering limit is near. You will be able to feel it.

Note that when the road surface condition sensor 60 detects that the road surface friction coefficient is relatively small, the hydraulic fluid 4 is adjusted so that the front roll rigidity is higher than when the road surface friction coefficient is relatively large.
It is also possible to control the supply and discharge of 4, thereby increasing understeer and improving steering stability.

Furthermore, in the above embodiment, the approximate road surface friction coefficient is detected by the optical sensor 60, and the lateral acceleration vs. roll angle characteristic is changed accordingly. It is also possible to indirectly detect the cornering limit, and since the conditions that determine the cornering limit include the loaded state of the vehicle, etc., it is possible to change the above characteristics according to one or more of these various conditions. You may also do so.

(Effects of the Invention) As explained in detail above, the suspension device of the present invention reduces the lateral acceleration when the conditions for determining the cornering limit change in the direction of lowering the cornering limit when controlling the vehicle body roll angle. Since the device is configured to enter the normal roll state from an early age, the driver can accurately feel the cornering limit from the roll feeling, thereby improving stability when turning.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a hydraulic circuit used in a suspension device according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing the suspension device, and FIGS. 3A and 3B are realized in the suspension device. It is a graph showing lateral acceleration versus roll angle characteristics for each road surface condition. 10... Wheels 11... Vehicle body 12...
・Hydraulic cylinder 13...Piston 14...Hydraulic pressure chamber 15 of the hydraulic cylinder 15...Piston rod 18...Hydraulic pressure passage 21
...Gas spring 81...High pressure piping 32...
・Pump 37.59...Accumulator 38.55...Hydraulic pressure gauge 39...Pilot passage 40...Recirculation passage 44...Hydraulic fluid 45...Control unit 5o...Solenoid on-off valve 51 ... Pressure guarantee valve 52 ... Flow rate control valve 53 ... Pressure-operated on-off valve 56 ... Operating pressure inlet 57 ... Acceleration sensor 58 ... Vehicle height sensor 6
0...Road surface condition sensor 61...Lateral acceleration sensor Fig. 3A OVL degree [(31 Fig. 3B 0.1 0.2 0.3 0.4 0.5 0.6 load lah Haoii degree [[shi]

Claims (1)

[Claims] In a vehicle suspension device configured to change the vehicle height by supplying and discharging working fluid to and from cylinders installed between the vehicle body and wheels, the lateral acceleration of the vehicle body is an acceleration sensor that detects the acceleration, and an acceleration sensor that receives the output of the sensor and controls the supply and discharge of working fluid to the cylinder so that the vehicle body roll angle takes a positive value when the acceleration is equal to or higher than a predetermined value. a controller is provided, and detection means is provided for detecting at least one condition that determines a cornering limit and inputting a signal indicative of the condition to the controller, the controller detecting a direction in which the condition lowers the cornering limit. 1. A suspension device for a vehicle, wherein the predetermined value is corrected to a smaller value when the predetermined value changes.