JP2805387B2 - Active suspension system for vehicles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an active suspension device for a vehicle, which is used in a vehicle such as an automobile, and alleviates an impact force at the time of riding over a projection or the like by a hydraulic actuator.

2. Description of the Related Art Conventionally, a so-called active suspension device that absorbs and reduces vertical vibration of a vehicle has been proposed. In this active suspension device, for each wheel, a hydraulic actuator is interposed between the wheel and the vehicle body, a hydraulic chamber of the hydraulic actuator is connected to an accumulator via an orifice, and an oil pump is connected to a hydraulic chamber of each hydraulic actuator. A control valve composed of a proportional solenoid valve is arranged in the middle of an oil passage for supplying hydraulic oil. When the active suspension controls the vertical vibration of the vehicle, the controller controls the operation of the above-described control valve based on the vibration input information from the vehicle height sensor and the sprung G sensor. While reducing vibration
For relatively high-frequency vibrations that cannot be followed by the control valve, the orifices act to attenuate the vibrations.

For example, the relative distance between the wheel and the vehicle body by the height sensor,
That is, when the vehicle height is smaller than the target vehicle height, that is, when trying to sink, the hydraulic oil is discharged from the hydraulic chamber of the hydraulic actuator according to the amount of sinking, and conversely, at the time of bumping, the operating oil is pushed according to the amount of bumps. In addition, a spring function can be provided to the hydraulic actuator. As described above, when the supply / discharge amount of the hydraulic oil is adjusted with respect to the vehicle height change, the spring constant can be equivalently controlled.

(Problems to be Solved by the Invention) In such a conventional active suspension device, the vertical vibration of the vehicle body caused by the undulation of the road surface can be favorably suppressed.

However, the above-mentioned active suspension device does not only operate when the road surface has undulations, but also when the shock actuator generates a full stroke when a shocking vibration is generated which is generated when riding over a bump or running along a pavement. The spring constant of the suspension unit is set in advance so that the collision between the cylinder of the actuator and the vehicle body can be prevented, so that a good ride comfort can be secured on a relatively wide range of road surface conditions including rough roads. Is set to

For this reason, the riding comfort on a good road surface (good road) where there is no impact vibration input such as over a bump,
It has not been fully satisfactory.

The present invention has been made in order to solve such a problem, and an active suspension device for a vehicle that improves the ride comfort by optimally controlling the supply and discharge of the hydraulic pressure of the hydraulic support means when traveling on a good road. The purpose is to provide.

(Means for Solving the Problems) In order to achieve the above-mentioned object, an active suspension device for a vehicle according to the present invention includes a hydraulic support means interposed between a vehicle body and each wheel to support the vehicle body; A vibration input for detecting a vibration input object in front of the vehicle in a vehicle active suspension device including a hydraulic control means for controlling supply and discharge of hydraulic pressure to each hydraulic support means and suppressing transmission of vibration from wheels to the vehicle body. Detecting means, the hydraulic control means, when the vibration input detecting means does not detect a vibration input object larger than a predetermined size, while limiting the divergence of the stroke amount, the stroke amount usually exceeds the maximum stroke amount The invention is characterized in that the supply and discharge of the hydraulic pressure are controlled so that the equivalent spring constant of the hydraulic support means is reduced so as to be variable and the amount of sloshing is promoted.

(Operation) According to the active suspension device described above, on a good road where the vibration input detecting means does not detect a vibration input object such as a protrusion, the hydraulic control means actively changes the equivalent spring constant of the hydraulic support means to a small value. To give a relaxed, soft ride.

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

FIG. 1 shows the configuration of a hydraulic active suspension system for a motor vehicle. FIG. 1 shows a suspension unit 12 as a hydraulic support means provided on each of the wheels, that is, the left and right front wheels and the left and right rear wheels. A suspension spring 13 of the suspension unit 12 and a single-acting hydraulic cylinder Hydraulic actuator consisting of 14
Is interposed between the vehicle body 7 and the wheels 8. The first
In the figure, a suspension unit combined with one wheel is representatively shown.

The control valve 17 of the suspension unit 12 is interposed between an oil passage 16 communicating with the hydraulic chamber 15 of the hydraulic actuator 14 and a supply oil passage 4 and a discharge oil passage 6 described later.
One end of the branch passage 16a is connected to the middle of the oil passage 16, and an accumulator 20 is connected to the other end of the branch passage 16a. A gas is sealed in the accumulator 20, and a so-called gas spring action is exerted by the compressibility of the gas. A restrictor 19 is provided in the middle of the branch path 16a, and the restrictor 19 regulates the amount of hydraulic oil flowing between the accumulator 20 and the hydraulic chamber 15 of the hydraulic actuator 14, whereby A desired vibration damping effect is exhibited.

The other end of the supply oil passage 4 described above is connected to the discharge side of the oil pump 1, and the suction side of the oil pump 1 is
It communicates with the inside of the reserve tank 3 via the oil passage 2. Therefore, when the oil pump 1 is driven, the working oil stored in the reserve tank 3 is discharged to the supply oil passage 4 side. In the supply oil passage 4, an oil filter 9, a check valve 10, and an accumulator 11 for maintaining line pressure are arranged in this order from the oil pump 1 side. Check valve 10
Allows only the flow of hydraulic oil from the oil pump 1 side to the suspension unit 12 side. The check valve 10 allows high-pressure hydraulic oil to be stored in the accumulator 11.

The control valve 17 is of a type that changes its valve opening in proportion to the value of the supplied current. The control valve 17 is connected between the supply oil passage 4 and the discharge oil passage 6 in accordance with the valve opening. , The supply and discharge of the hydraulic pressure to and from the hydraulic actuator 14 can be controlled. The configuration is such that the greater the current value supplied to the control valve 17, the greater the hydraulic pressure in the hydraulic actuator 14, that is, the generated supporting force. The hydraulic oil discharged from the control valve 17 to the discharge oil passage 6 is returned to the reservoir tank 3 described above.

The control valve 17 is electrically connected to the output side of the controller 30 constituting the hydraulic control means, and its operation is controlled by a drive signal from the controller 30. Therefore, on the input side of the controller 30, various sensors for controlling the suspension unit 12, for example, a sprung G sensor 31, which is provided for each wheel and detects the vertical acceleration acting on the vehicle body, A vehicle height sensor 32 for detecting a stroke amount of the suspension unit 12 and a vibration input detecting means, and detecting a projection or the like on a road surface in front of the vehicle and outputting an output signal value according to the size of the projection or the like. A preview sensor 33 for outputting, a vehicle speed sensor 34 for detecting a traveling speed of the vehicle, a steering angle sensor 35 for detecting a steering angle of the vehicle, and the like are connected.

As the preview sensor 33, for example, an ultrasonic sensor is used, and this sensor 33 is attached to the front part of the vehicle body in front of the vehicle body and obliquely downward (see FIG. 2).

The operation of the above-described control valve 17 is controlled by the controller 3 based on the detection signal of each sensor, as will be described later in detail, and the supply and discharge of the hydraulic pressure to and from the hydraulic actuator 14 are thereby controlled. In addition to the supply / discharge control of the hydraulic pressure to the hydraulic actuator 14, the vibration input to the vehicle body from the road surface is absorbed by the hydraulic chamber 15 of the hydraulic actuator 14 communicating with the accumulator 20 through the throttle 19. And it is designed to be attenuated.

Next, the functions of the vehicle active suspension according to the present embodiment according to the traveling state will be described with reference to FIGS.
This will be described with reference to FIGS. 5 and 6.

A series of control starts with the controller 30 reading the output signal of the ultrasonic reflected wave input from the preview sensor 33 in step S10 in FIG.

Next, the controller 30 determines from the output signal of the preview sensor 33 read in step S10 whether a protrusion or the like larger than a predetermined size is detected (step S10).
S12).

If the determination result of step S12 is affirmative (Yes), the normal control of step S30 defined next is executed, the routine ends, and the routine returns.

In the present embodiment, the normal control refers to the subsequent step S2
This control is a control system that is contrasted with the reverse spring control described in detail 2 and converges when the vehicle body vibration is generated by an external force. When this is embodied by the active suspension device shown in FIG. 1, the equivalent spring constant of the suspension unit 12 is compared with the equivalent spring constant in the reverse spring control so as to be able to cope with a relatively wide range of road surface conditions including a rough road. Then, the hydraulic pressure is controlled by the control valve 17.

Next, if the determination result of step S12 is negative (No), the vehicle speed V vehicle speed sensor 34 detects the steering angle sensor 35 reads the steering theta _H detected is executed (step S1
Four).

Then, the controller 30 determines whether or not the absolute value | θ _H | of the vehicle speed V and the steering angle θ _H is within the reverse spring control region shown in FIG. 4 (Step S16).

The above-described determination is performed in order to prohibit the reverse spring control during the high-speed running and the steering angle operation, and to prevent a decrease in running stability.

The above-described reverse spring control region is a region for prohibiting reverse spring control defined by the vehicle speed V and the steering angle absolute value | θ _H |, where the vehicle speed V increases from the value 0 (zero) to the upper limit of the vehicle speed. Value V ₀
Until, steering angle absolute value | θ _H | is, ₀ from the value θ ₀ value θ and the value 0
A straight line that decreases at a constant rate to a value θ ₁ between
It is a region surrounded by a straight line composed of V = V ₀ .

If the determination result in step S16 is negative, the normal control in step S30 described above is executed, the routine ends, and the routine returns.

If the determination result in step S16 is affirmative, the process proceeds to step S18, where the suspension stroke amount L detected by the vehicle height sensor 32 is read.

Here, the reason why the suspension stroke amount L is read is that, as will be described in detail later, since the reverse spring control is a control of a so-called divergent system, the suspension stroke amount L facilitated by the execution of the reverse spring control is The purpose is to monitor and to set certain limits on its operation so that the whole system does not diverge further.

Next, the suspension stroke amount L is, whether or not it is within a predetermined small stroke L ₀ determination is executed (step S20).

If the determination result of step S20 is negative, step S30
Is executed, the routine ends, and the routine returns. Therefore, unless a new external force is input,
The vehicle body vibration generated at that time is attenuated as it is by a vibration damping effect that functions under normal control.

If the determination result in step S20 is affirmative, the reverse spring control in step S22 is executed next. At this time, an equivalent circuit of a stroke feedback system as shown in FIG. 5 is formed in the controller 30. That is, the difference between the target stroke amount L _I and the actual stroke amount L _A is calculated by the subtracting circuit 30a, to the control gain K is multiplied by the amplifier circuit 30b, than is the hydraulic control of the control valve 17 is executed . This equivalent circuit is characterized by constituting a control of a divergence system, and the control gain K is set so as to equivalently lower the spring constant by at least the amount of canceling the friction of the suspension unit 12. is required.

Explaining the above with the actual operation of the suspension unit 12, when the hydraulic actuator 14 contracts, it further contracts beyond the position (lowest point) where it stops under normal control, and
When the hydraulic actuator 14 extends, an operation that extends further beyond the position (top point) where it stops under normal control,
That is, an operation for promoting the suspension stroke is performed.

Since the control is a divergent system, it is naturally necessary to set a certain limit on the operation of the system. This is step S2
This is a restriction by the predetermined upper limit value L0 of the suspension stroke amount L executed in the determination of ₀ .

Based on the control amount calculated in this way, the controller 30 controls the supply and discharge of the hydraulic pressure applied to the hydraulic actuator 14 by changing the current value for driving the control valve 17, and makes the equivalent spring constant of the suspension unit 12 extremely soft. Change it into something.

The effect produced at this time can be shown by FIG. That is, by changing the equivalent spring constant of the suspension unit 12 to a small value, the suspension stroke amount L increases, and the vibration period also increases.
A soft and comfortable ride can be obtained.

 Thus, the routine ends, and the process returns.

According to the above-described embodiment, the vehicle speed V and the steering angle absolute value |
theta _H | is, the vehicle speed V and the steering angle absolute value | but opposite spring control is executed only when it is in the predetermined two region defined by, | theta _H
Instead, the vehicle speed V and the steering angle absolute value | θ _H |
Independent predetermined upper limit values may be set to limit reverse spring control. Furthermore, a lower limit value is set for the vehicle speed V, and the effect of the reverse spring control is very low, for example,
Reverse spring control at less than 3 mil per hour may be prohibited.

Further, according to the above-described embodiment, in order to limit the divergence, the suspension stroke amount L is set to the predetermined upper limit value L ₀ , and when L exceeds L ₀ , the reverse spring control is prohibited. The means for restricting the divergence is not limited to the above-described means, but may be, of course, performed by means such as providing a limit to another variable.

(Effects of the Invention) As described in detail above, according to the active suspension device of the present invention, on a good road where the vibration input detecting means does not detect a protrusion or the like, the hydraulic control means positively increases the equivalent spring constant of the hydraulic support means. By changing the control system to a divergent system called a so-called reverse spring control to make the ride soft and comfortable, the ride comfort on a good road can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining a schematic configuration of an active suspension device for a vehicle according to the present invention. FIG. 2 is a diagram showing a situation where a preview sensor 33 in FIG. FIG. 3 is a flowchart showing a procedure of reverse spring control executed by the controller 30 in FIG. 1, FIG. 4 is a graph showing a reverse spring control area defined by the vehicle speed and the steering angle absolute value, and FIG. FIG. 6 is a block diagram showing a configuration of an equivalent circuit in the reverse spring control in the controller 30 shown in FIG. 1, and FIG. 6 is a vehicle height sensor shown in FIG.
32 is a graph showing the time change of the vehicle height fluctuation detected. 7 ... body, 8 ... wheels, 12 ... suspension unit (hydraulic support means), 14 ... hydraulic actuator, 17 ...
... control valve, 20 ... accumulator, 30 ... controller (hydraulic control means), 31 ... sprung vertical G sensor, 32
... vehicle height sensor, 33 ... preview sensor (vibration input detecting means), 34 ... vehicle speed sensor, 35 ... steering angle sensor.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akihiko Togashi 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Naohiko Kishimoto 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (72) Inventor Hiroaki Yoshida 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (56) References JP-A-2-162108 (JP, A) JP 1984-63219 (JP, A)

Claims (1)

(57) [Claims] 1. A hydraulic transmission means interposed between a vehicle body and each wheel for supporting the vehicle body, and controlling the supply and discharge of hydraulic pressure to and from each hydraulic support means to transmit vibration from the wheels to the vehicle body. And an oil pressure control means for suppressing the vibration, the vibration input detection means for detecting a vibration input object in front of the vehicle, the hydraulic control means, the vibration input detection means is larger than a predetermined size When a large vibration input object is not detected, the divergence of the stroke amount is limited, and the equivalent spring constant of the hydraulic support means is reduced so that the stroke amount can be changed to exceed the normal maximum stroke amount. Active suspension device for a vehicle, characterized in that the supply and discharge of hydraulic pressure are controlled as described above.