JPS61268509A - Device for controlling active type suspension - Google Patents

Abstract

PURPOSE:To improve riding quality by controlling a directional selector valve for a fluid-pressure cylinder by means of a load signal which is applied to a car body from said fluid-pressure cylinder and a stroke controlling signal for said fluid-pressure cylinder. CONSTITUTION:Relative displacement between the upper and lower positions of spring in a wheel position, from a stroke sensor 9 provided between the cylinder tube 1a of a fluid-pressure cylinder 1 and a body-side member 2, is inputted, as a stroke signal, into a control device 10, while the signal of a transmitted load which is transmitted from a load sensor 12 installed on a piston rod 1b, to the body-side member 2, is also inputted into the control device 10. The control device 10 controls a directional selector valve 4 so as to change the stroke of a fluid-pressure cylinder 1 to a target stroke, based on the stroke signal of the stroke sensor 9. It also controls the directional selector valve 4 in the direction of reducing load based on the load transmitting signal of the load sensor 12. Thus, by controlling two systems of a load controlling system and a stroke controlling system, the riding quality can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an active suspension control device that actively suppresses rocking of a vehicle body by controlling a suspension.

[Conventional technology]

As a conventional active suspension control device, for example, there is one described in Japanese Patent Application Laid-Open No. 58-79438 (first conventional example).

As shown in FIG. 3(a), the device has a cylinder tube 1 of a double-acting hydraulic cylinder 1 attached to a wheel side member.
a is attached, the piston rod 1b of this hydraulic cylinder 1 is attached to the vehicle body side member 2, and a coil spring 3 is installed between the cylinder tube la and the vehicle body side member 2. It supports the side member 2. Upper and lower pressure chambers A of hydraulic cylinder 1
and B are oil pressure a! via a center bypass type electromagnetic directional control valve 4. In addition to being connected to X5, both pressure chambers A
.

An orifice 6 is connected between B.

Another conventional example is "Autocar J" published in the UK on September 1, 1983.
llaymarket publishing Ltd
There is also one such as that described in (Published by, Inc.) (Second Conventional Example).

As the schematic configuration of the device is shown in FIG. 3 [b], the cylinder tube 1a of the single-acting hydraulic cylinder 1 is attached to the vehicle body side member 2, and the piston rod 1b is attached to the wheel side member. , and the vehicle body side member 2 is supported by a gas spring 7, and this gas spring 7 and the pressure chamber of the hydraulic cylinder l are communicated via an orifice 8.

Therefore, the electromagnetic directional control valve 4 of the first conventional example and the second conventional example is controlled by the relative displacement (stroke) between the unsprung portion and the unsprung portion.
The stroke sensor 9 detects the stroke, and the control device 10 controls the directional control valve 4 based on the stroke detection signal, thereby controlling the stroke fluctuation of the vehicle body to be small.

The control method in this case is as schematically shown in FIG.
When the steering wheel is turned, the accelerator pedal is depressed, the brake pedal is depressed, etc., which cause a change in the attitude of the vehicle, lateral acceleration or longitudinal acceleration occurs in the vehicle body (block ■). This causes relatively low-frequency (approximately 3 Hz or less) attitude changes in the vehicle body, such as rolling, pitching, and bouncing (
block ■). In this way, when a change in attitude occurs in the vehicle body, this is detected by the stroke sensor 9 (
Block ■) calculates the deviation between the stroke detection value and a preset target stroke (set to zero in normal conditions without changes in vehicle attitude), and adjusts the electromagnetic directional control valve 4 according to the deviation. (block ■) to control actuator 1 (block ■), thereby,
Control is performed to minimize changes in vehicle body posture.

On the other hand, when a relatively high frequency (10 to 30 Hz) vibration input is applied due to an unsprung blade due to unevenness of the road surface (block ■), the road surface input is transmitted from the coil spring 3 in the first conventional example. (Block ■) Both pressure chambers A are input to the vehicle body.

Based on the throttling action of the orifice 6 provided between B, the piston rod 1b (block ■) is also input to the vehicle body.

In addition, in the second conventional example, based on the spring action of the gas spring 7 (block ■) and the throttling action of the orifice 8 provided between the gas spring 7 and the pressure chamber, manual force is applied to the vehicle body from the cylinder tube 1a. Ru.

[Problem that the invention seeks to solve]

However, in the above-mentioned conventional active suspension control devices, since both the first conventional example and the second conventional example generate damping force with an orifice having a constant characteristic, the damping force is generated by a relatively high frequency (10 to 3011z) road surface. The actuator 1 acts in the same way as a conventional shock absorber in response to human power, and the excitation force from under the spring is input to the vehicle body through the orifice, so the excitation force cannot be actively reduced, and the There was a problem that the ride comfort of the vehicle was not sufficiently improved. Therefore, this invention was made by focusing on the above-mentioned conventional problem, and it is possible to reduce the load applied to the vehicle body from the fluid pressure cylinder and the load of the fluid pressure cylinder. The above problem can be solved by controlling the fluid pressure in both the upper and lower pressure chambers of the fluid pressure cylinder using two systems, the load control system and the stroke control system, by operating a directional control valve based on the stroke and reducing vibration input. It aims to solve the problem.

[Means for solving problems]

This invention was made by focusing on such conventional problems, and provides a fluid pressure cylinder that is interposed between the sprung portion and the unsprung portion of a vehicle and absorbs vibration input from the wheel side to the vehicle body side. In an active suspension control device, the pressure in both the upper and lower pressure chambers of the fluid pressure cylinder is controlled by a control valve. a detection means, a first valve control circuit that controls the switching valve to reduce the transmitted load based on the load detection signal from the load detection means, and a stroke detection signal corresponding to the actual stroke of the fluid pressure cylinder. The present invention is characterized by comprising a stroke detection means for outputting an output, and a second valve control circuit that controls the switching valve so that the actual stroke matches the target stroke based on the stroke detection signal from the stroke detection means.

[Effect]

In this invention, the load transmitted to the vehicle body from the fluid pressure cylinder interposed between the sprung masses of the vehicle is detected by the load detection means, and the stroke of the fluid pressure cylinder is detected by the stroke detection means. and controls the direction switching valve based on the stroke detection signal of the stroke detection means to suppress relatively low frequency (approximately 38 Z or less) vehicle body vibration, and also controls the direction switching based on the load detection signal of the load detection means. By controlling relatively high frequency (10 to 30 Hz) vehicle body vibration, it is possible to reliably absorb not only relatively low frequency vibration input but also relatively high frequency vibration input. .

〔Example〕

The present invention will be explained below based on illustrated embodiments.

FIG. 1 and FIG. 2 are diagrams showing an embodiment of the present invention. In FIG. 1, parts that are the same as those of the conventional device are given the same reference numerals.

First, to explain the configuration, 1 shown in FIG. 1 is a hydraulic cylinder as a fluid pressure cylinder interposed between the unsprung portion and the unsprung portion of the vehicle, and the lower end of the cylinder tube 1a rotates the wheel 11. The piston rod 1b is rotatably attached to a wheel-side member (not shown) that can support the piston rod, and the upper end of the piston rod 1b is rotatably attached to the vehicle body-side member 2.

A coil spring 3 is disposed concentrically with the piston rod 1b between the cylinder tube la and the vehicle body side member 2.
is interposed.

The cylinder tube 1a of the hydraulic cylinder 1 is divided into a lower pressure chamber A and a lower pressure chamber B by a piston lc attached to the lower end of a piston rod 1b extending inside the cylinder tube 1a. .

B is communicated with a hydraulic power source 5 as a fluid pressure source via an electromagnetic directional control valve 4 with four points and three positions. The neutral position of the directional switching valve 4 is of a center bypass type, and switching is controlled by a control signal from a control device 10 supplied to the electromagnetic solenoid.

Further, between the cylinder tube 1a and the vehicle body side member 3, a stroke sensor 9 is provided, for example, a potentiometer, and is a stroke detection means for detecting the relative displacement (stroke) between the sprung masses and the sprung masses at each wheel position. The stroke sensor 9 outputs a stroke detection signal with a voltage corresponding to the stroke from the neutral state at each wheel position. Further, the piston rod 1b is provided with a load sensor 12, which is a load detection means constituted by a piezoelectric element, for example. Outputs a load detection signal with a voltage depending on the magnitude.

The stroke detection signal of the stroke sensor 9 and the load detection signal of the load sensor 12 are transmitted to a first valve control circuit and a second valve control circuit.
The control device 10 is provided with a valve control circuit. The first valve control circuit has a bypass filter that receives a load detection signal from the load sensor 12 and cuts a frequency component of, for example, less than 3 Hz from the signal, and the magnitude of the frequency component that has passed through the bypass filter is A control signal corresponding to the change in direction is sent from this first valve control circuit to the directional control valve 4. The second valve control circuit also includes a low-pass filter that receives a stroke detection signal from the stroke sensor 9 and cuts off frequency components of, for example, 311z or higher among the signal components, and a signal component that passes through this low-pass filter. It has a comparison circuit that compares the actual stroke at each wheel position with the target stroke (zero in a normal state where there is no change in the attitude of the vehicle), and a control signal corresponding to the difference as a result of the comparison is transmitted to the second It is sent to the directional control valve 4 from the valve control circuit.

Thus, the directional control valve 4 has an excitation current value corresponding to the magnitude of the control signal from the first valve control circuit and an excitation current corresponding to the magnitude of the control signal from the second valve control circuit. A total excitation current obtained by adding the current values is supplied, and the directional switching valve 4 is controlled to switch according to the magnitude of the total excitation current.

Next, the operation will be explained based on FIG.

Assume that the vehicle is traveling straight at a constant speed on a flat, good road, that there is almost no vibration input to the wheels from the road surface, and that the vehicle body is not experiencing any changes in attitude such as rolling, pitching, or bouncing. Therefore, in this state,
The relative displacement between the sprung and unsprung portions of the hydraulic cylinder 1 interposed between each wheel and the vehicle body, that is, the stroke, substantially matches the target stroke (usually set to zero).

Therefore, since the stroke detection signal sent from the stroke sensor 9 to the control device 10 is a signal indicating that the actual stroke substantially matches the target stroke, the control device 10 may output a control signal depending on the stroke detection signal. No output. Furthermore, since there is no vibration manual force transmitted from the wheel side to the vehicle body side member 2 via the hydraulic cylinder 1, the load detection signal sent from the load sensor 12 to the control device 10 is approximately constant without any fluctuation in the load. Since the signal indicates a value, the control device 10 does not output a control signal depending on the load detection signal.

Therefore, the directional control valve 4 is maintained at the initial neutral position, and the upper and lower pressure chambers A and B of the hydraulic cylinder l are maintained in a state of being cut off from the hydraulic power source 5. B are maintained independently and at approximately equal pressures.

From this state, when you turn the steering wheel, press the brake pedal, or accelerator pedal, etc., which cause the vehicle to change its attitude (block [phase]), the vehicle body experiences lateral acceleration and longitudinal acceleration in response to these actions. (block ■), which causes relatively low-frequency vibrations such as rolling, pitching, and bouncing (31
It resonates below 1z, usually around IHz. ) occurs (block @), causing a change in attitude of the vehicle.

In this manner, when a change in attitude occurs in the vehicle, the stroke of the hydraulic cylinder 1 is detected by the stroke sensor 9 (block 0), and a stroke detection signal corresponding to the actual stroke is output. The stroke detection signal is supplied to a low-pass filter (for example, cut-off frequency is 3Hz or higher) of the second valve control circuit that constitutes a part of the control device 10 (block ■), where a relatively high-frequency signal of 311z or higher is input. The vibration component is removed and only a relatively low frequency vibration component of less than 3 Hz passes through, and the second valve control circuit outputs a control signal to the directional control valve 4 based on the low frequency vibration component.

That is, for example, when the steering wheel is rotated clockwise to shift to a right-turning state, rolling occurs in the vehicle body, and the hydraulic cylinders 1 that suspend the front left wheel and the rear left wheel respectively contract, thereby changing the vehicle height at the front and rear left wheel positions. hydraulic cylinder 1 that suspends the front right wheel and the rear right wheel.
are extended, increasing the vehicle height at the front and rear right wheel positions.

In this way, when a posture change occurs in the vehicle body, it is detected by the four stroke sensors 9 installed in relation to each wheel, and the stroke detection signal is supplied to the second valve control circuit of the control device 10. . Therefore, the second valve control circuit controls the hydraulic pressure source 5 for the front and rear right wheel side hydraulic cylinders l.
The directional control valve 4 is switched to the upper position (block [phase]) in FIG. For the side hydraulic cylinder 1, a hydraulic source 5
The directional control valve 4 is switched to the lower position in FIG. 1 (block 0) so as to introduce the hydraulic pressure into the lower pressure chamber B and discharge the corresponding hydraulic pressure from the lower pressure chamber A (block 0).

As a result, in the front and rear right wheel side hydraulic cylinders 1, the hydraulic pressure source 5
The discharge side of the hydraulic pressure source 5 communicates with the lower pressure chamber A, and the hydraulic pressure of the lower pressure chamber A increases due to the hydraulic pressure from the hydraulic pressure source 5, and the hydraulic pressure of the lower pressure chamber B decreases, so that the piston rod 1b is pushed down (block [Phase]), the vehicle height at the front and rear right wheel positions is lowered. On the contrary, in the front and rear left wheel side hydraulic cylinders 1, the discharge side of the hydraulic pressure source 5 and the lower pressure chamber B are communicated, and the hydraulic pressure in the lower pressure chamber B increases and decreases due to the hydraulic pressure from the hydraulic pressure source 5. Since the oil pressure in the pressure chamber A decreases and the piston rod 1b is pushed down (block [phase]), the vehicle height at the front and rear left wheel positions increases. Therefore, due to the action of the hydraulic cylinder 1, it is possible to suppress the increase in vehicle height at the front and rear right wheel positions, while suppressing the decrease in vehicle height at the front and rear left wheel positions. By suppressing rocking, changes in the posture of the vehicle can be effectively suppressed.

Furthermore, when the vehicle is traveling straight at a constant speed on a flat, good road, when the excitation force caused by riding over a convex part of the road surface is input from the wheels 11 to the hydraulic cylinder 1 (block O), this causes the hydraulic cylinder 1 to is pressed upward, and the excitation force is transmitted from the cylinder tube 1a to the vehicle body side member 2 via the hydraulic oil in both the upper and lower pressure chambers A and B and the piston rod lb (block [phase]). At the same time, on the other hand, it is transmitted from the cylinder tube 1a to the vehicle body side member 2 via the coil spring 3 (block [phase]).

In this way, when the excitation force from the road surface is input to the hydraulic cylinder 1, the load transmitted to the vehicle body side member 2 via the piston rod 1b is detected by the load sensor 12 (block @), and the load is A corresponding stroke detection signal is output. The multiplex detection signal is supplied to a bypass filter (for example, cutoff frequency is less than 3Hz) of the first valve control circuit that constitutes a part of the control device 10 (block [phase]), where the Relatively low frequency vibration components are removed and only relatively high frequency vibration components of 3 Hz or higher pass through, and the first valve control circuit outputs a control signal to the directional control valve 4 based on the high frequency vibration components.

That is, for example, when the wheel 11 rides on a convex part of the road, the load transmitted to the vehicle body side member 2 via the piston rod 1b increases in accordance with the road surface input, which is detected by the load sensor 12, and the load is increased. The load detection signal is transmitted to the control device 10
is supplied to a first valve control circuit. Therefore, the first valve control circuit switches the directional control valve 4 to the lower position in FIG. 1 so that the hydraulic pressure from the hydraulic source 5 is introduced into the lower pressure chamber B, and the corresponding hydraulic pressure is discharged from the lower pressure chamber A. (
block ■).

As a result, the discharge side of the oil pressure source 5 and the lower pressure chamber B are communicated with each other, and the oil pressure in the lower pressure chamber B increases due to the oil pressure from the oil pressure source 5, and the oil pressure in the lower pressure chamber A decreases, so that the piston rod 1b is pushed up (block@), so the vehicle height at each wheel position becomes higher. Therefore, due to the action of the hydraulic cylinder 1, the pressure difference between the upper and lower pressure chambers A and B is controlled to be small, and in this way, the vibration human force (3
It has a resonance point above Hz, especially at 10 to 30 Hz. ) is reduced.

As a result, among the vibration input from the road surface to the vehicle body side member 2,
As mentioned above, the load transmitted through the piston rod 1b is reduced, and only the load transmitted from the coil spring 3 is transmitted to the vehicle body side member 2, so the transmitted force is significantly increased compared to the conventional one. can be reduced.

Accordingly, in the present invention, relatively low-frequency changes in vehicle body posture and rocking are suppressed by a stroke control system based on the stroke detection signal from the stroke sensor 9, and relatively high-frequency road surface inputs are suppressed. This can be reduced by a transmission force control system based on the load detection signal from the load sensor 12. Therefore, by performing the above control, it is not only possible to suppress the shaking of the vehicle body that causes a change in the vehicle's attitude, but also to actively reduce the overhanging blade from under the spring due to unevenness of the road surface. ,
Both the ride comfort and driving feeling of the vehicle can be significantly improved.

In the case of the above embodiment, the cutoff frequency of the control loop of the stroke control system and the loop of the transmission force control system is 3.
Since the signal is divided by 112 low-pass filters and bypass filters, mutual interference between the re-control systems can be prevented.

Further, in the above embodiment, an example was described in which the hydraulic cylinder 1 using hydraulic oil or the like was applied as the fluid pressure cylinder, but the invention is not limited to this, and the hydraulic cylinder 1 may be operated by other fluid pressure such as air pressure. Of course, a fluid pressure cylinder can be applied. Further, in the above embodiment, a stroke sensor made of a potentiometer is used as a stroke detection means, but the invention is not limited to this, and any relative displacement detection means such as a differential transformer may be used. can.

Furthermore, although the case where a piezoelectric element is applied as the load detection means has been described, the present invention is not limited to this, and any load detection means such as a load cell or a strain gauge can be applied.

〔Effect of the invention〕

As described above, according to the present invention, a fluid pressure cylinder is provided between the sprung mass and the unsprung mass of a vehicle to absorb vibration input from the wheel side toward the vehicle body, and In an active suspension control device in which the pressure in both pressure chambers is controlled by a switching valve, a load detection means outputs a load detection signal corresponding to the load transmitted from the fluid pressure cylinder to the vehicle body; a first valve control circuit that controls the switching valve to reduce the transmitted load based on the load detection signal; a stroke detection means that outputs a stroke detection signal according to the stroke of the fluid pressure cylinder; and a second valve control circuit that controls the switching valve so that the actual stroke matches the target stroke based on the stroke detection signal of the active suspension control device. As a result, it is not only possible to suppress changes in vehicle body posture and lateral movement caused by relatively low-frequency vibration input, but also to suppress input to the vehicle when driving over rough road surfaces, bumps, etc., which could not be achieved with conventional devices. It is possible to actively reduce the force transmitted to the vehicle body based on the road surface input from under the springs, which has the effect of improving both the ride comfort and driving feeling of the vehicle.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram for explaining the control method according to the present invention, and FIGS. 3(a) and (b) are block diagrams of a conventional device, respectively. FIG. 4 is an explanatory diagram for explaining a conventional control method. 1...Hydraulic cylinder (fluid pressure cylinder), 1a
... Cylinder tube, 1b ... Piston rod, 2 ... Body side member, 3 ...
・Coil spring, 4... Directional switching valve, 5.
... Hydraulic pressure source (fluid pressure source), 9 ... Stroke sensor (stroke detection means), 10 ...
Control device, 12...Load sensor (load detection means)

Claims (1)

[Claims] Equipped with a fluid pressure cylinder that is interposed between the sprung mass and the unsprung mass of the vehicle and absorbs vibration input from the wheel side toward the vehicle body,
In an active suspension control device in which the pressure in both the upper and lower pressure chambers of the fluid pressure cylinder is controlled by a control valve, a load detection means outputs a load detection signal corresponding to the load transmitted from the fluid pressure cylinder to the vehicle body. and a first valve control circuit that controls the switching valve to reduce the transmitted load based on the load detection signal from the load detection means;
a stroke detection means for outputting a stroke detection signal corresponding to the actual stroke of the fluid pressure cylinder; and a second stroke detection means for controlling the switching valve so as to make the actual stroke match the target stroke based on the stroke detection signal from the stroke detection means. An active suspension control device comprising: a valve control circuit;