Active suspension apparatus for a vehicle

• US 5,322,319 A
• Filed: 10/23/1992
• Issued: 06/21/1994
• Est. Priority Date: 09/17/1990
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Jidosha Kogyo Kabushiki Kaisha
• Original Assignee: Mitsubishi Jidosha Kogyo Kabushiki Kaisha
• Inventors: Morita, Takao, Tanaka, Tadao, Togashi, Akihiko, Kishimoto, Naohiro, Yoshida, Hiroaki
• Primary Examiner(s): Tyson, Karin L.
• Application Number:
  US07/965,707
• Time in Patent Office: 606 Days
• Field of Search: 280/707, 280/DIG. 1, 280/689, 280/772, 280/112.2, 280/6.12, 280/714, 280/709, 364/424.05
• US Class Current: 280/5.503
• CPC Class Codes: B60G 17/0165 to an external condition, e.g. rough road surface, side wind
• CPC Class Codes: B60G 2202/154 with an accumulator
• CPC Class Codes: B60G 2202/24 Fluid damper
• CPC Class Codes: B60G 2400/102 vertical
• CPC Class Codes: B60G 2400/204 Vehicle speed
• CPC Class Codes: B60G 2400/252 vertical
• CPC Class Codes: B60G 2400/41 Steering angle
• CPC Class Codes: B60G 2400/82 Ground surface
• CPC Class Codes: B60G 2401/176 Radio or audio sensitive means, e.g. Ultrasonic
• CPC Class Codes: B60G 2500/10 Damping action or damper
• CPC Class Codes: B60G 2500/22 Spring constant
• CPC Class Codes: B60G 2800/916 Body Vibration Control

Abstract

An active suspension apparatus is provided for a vehicle which includes an actuator being extensible and retractable and provided between a vehicle body and a wheel so that the force of the vehicle body to support the wheel is adjustable, a sprung G sensor or a vehicle height sensor for detecting a vibration input to the vehicle body, and a control valve and a controller for controlling the supporting force of the actuator in accordance with the vibration input detected by the sprung G sensor or the vehicle height sensor, and thereby restraining the stroke of the actuator. The suspension apparatus further comprises a forward road surface sensor for detecting the size of irregularities of a road surface in front of the vehicle, and the control valve and the controller are adapted to execute normal control such that the equivalent spring constant of the actuator is adjusted to a first spring constant when a surface irregularity of a size larger than a predetermined size is detected by the forward road surface sensor, and to execute inverse spring control such that the equivalent spring constant of the actuator is adjusted to a second spring constant lower than the first spring constant, and thereby lengthening the stroke of the wheel, when no surface irregularity of a size larger than the predetermined size is detected by the forward road surface sensor. As a result, the ride is greatly improved when the vehicle runs on a smooth road.

Claims

1. An active suspension apparatus for a vehicle having a body and a wheel, comprising:

an actuator being extensible and retractable and provided between the vehicle body and the wheel so that the force of the vehicle body to support the wheel is adjustable;

vibration input sensing means for detecting a vibrating input to the vehicle body;

control means for controlling the supporting force of said actuator by a normal control such that the relative displacement between the vehicle body and the wheel is restricted for damping vibrations of the vehicle body and an inverse spring control for preventing the running stability from being lowered during high-speed running and steering operations in accordance with the vibration input detected the vibration input sensing means and thereby restraining the stroke of the wheel; and

a forward road surface sensor for detecting the size of irregularities of a road surface in front of the vehicle, and said control means controlling the supporting force of said actuator by said inverse spring control such that the equivalent spring constant of a suspension is lowered, and thereby lengthening the stroke of the wheel, when surface irregularities of a size less than or equal to a predetermined size are detected by said forward road surface sensor and controlling the supporting force of said actuator by said normal control when surface irregularities of a size larger than said predetermined size are detected by said forward road surface sensor.

2. A suspension apparatus according to claim 1, wherein said vibration input sensing means comprises vehicle height sensing means for detecting a relative distance between the wheel and the vehicle body, and said inverse spring control is executed in a manner such that the supporting force of the actuator is controlled in accordance with the difference between a target relative distance and an actual relative distance which is detected by the vehicle height sensing means.

3. A suspension apparatus according to claim 2, wherein the target relative distance is corrected in accordance with the difference between the target and actual relative distances, and the supporting force of said actuator is controlled in such a manner that the actual relative distance is brought to be in conformity with the thus corrected target relative distance.

4. A suspension apparatus according to claim 2, wherein said control means fails to execute the inverse spring control when the relative distance detected by the vehicle height sensing means is longer than a predetermined relative distance.

5. A suspension apparatus according to claim 2, wherein said vehicle height sensing means detects the relative distance between the wheel and the vehicle body measuring the stroke of the actuator.

6. A suspension apparatus according to claim 3, wherein said vehicle height sensing means detects the relative distance between the wheel and the vehicle body measuring the stroke of the actuator.

7. A suspension apparatus according to claim 1, further comprising vehicle speed sensing means for detecting the speed of the vehicle, and wherein said control means fails to execute the inverse spring control when the vehicle speed detected by the vehicle speed sensing means is higher than a predetermined vehicle speed.

8. A suspension apparatus according to claim 1, further comprising steering angle sensing means for detecting the steering angle of the vehicle, and wherein said control means fails to execute the inverse spring control when the absolute value of the steering angle detected by the steering angle sensing means is larger than the value of a predetermined steering angle.

9. A suspension apparatus according to claim 8, further comprising vehicle speed sensing means for detecting the speed of the vehicle, and wherein said predetermined steering angle is set so as to decrease as the vehicle speed detected by the vehicle speed sensing means increases.

10. A suspension apparatus according to claim 1, wherein said control means includes a control valve for controlling oil pressure, and said actuator comprises a hydraulic actuator for increasing or decreasing the supporting force pressurized by oil pressure which is controlled by the control valve.

11. A suspension apparatus according to claim 1, wherein said forward road surface sensor comprises an ultrasonic sensor attached to the front portion of the vehicle body so as to be directed forward and diagonally downward with respect to the vehicle body.

12. The active suspension apparatus according to claim 1, wherein said control means executes said normal control adjusts an equivalent spring constant of said actuator to a first spring constant and executes said inverse spring control adjusts said equivalent spring constant of said actuator to a second spring constant lower than said first spring constant to lengthen the stroke of the wheels of the vehicle.

13. A method for controlling an active suspension apparatus for a vehicle, comprising the steps of:

(a) supplying a force from the vehicle by an actuator to support the wheels of the vehicle;

(b) detecting a vibration input to the vehicle body;

(c) detecting the size of irregularities of a road surface in front of the vehicle;

(d) controlling the supporting force of said actuator in accordance with said vibration input detected at said step (b) for thereby restraining the stroke of the wheels;

(e) executing inverse spring control for preventing the running stability from being lowered during high-speed running and steering operations to control the supporting force of said actuator based on said vibration input detected at said step (b) such that the equivalent spring constant of a suspension is lowered for thereby lengthening the stroke of the wheels when surface irregularities of a size less than or equal to a predetermined size are detected at said step (c); and

(f) executing normal control such that the relative displacement between the vehicle body and the wheel is restricted for damping vibrations of the vehicle body to control the supporting force of said actuator based on said vibration input detected at said step (b) when surface irregularities of a size larger than said predetermined size are detected at said step (c).

14. A method according to claim 13, further comprising the steps of detecting a relative distance between the wheel and the vehicle body and executing said inverse spring control such that the supporting force of said actuator is controlled in accordance with the difference between a target relative distance and an actual distance which is detected.

15. A method according to claim 14, further comprising the steps of correcting the target relative distance in accordance with the difference between the target and actual relative distances and controlling the supporting force of said actuator such that the actual relative distance is brought to be in conformity with the thus corrected target relative distance.

16. A method according to claim 14, wherein said inverse spring control fails to be executed when the relative distance detected is longer than a predetermined relative distance.

17. A method according to claim 14, wherein the relative distance detected is between the wheel and the vehicle body measuring the stroke of said actuator.

18. A method according to claim 13, further comprising the steps of detecting the speed of the vehicle and preventing said inverse spring control from being executed when the vehicle speed detected is higher than a predetermined vehicle speed.

19. A method according to claim 13, further comprising the steps of detecting the steering angle of the vehicle and preventing said inverse spring control from being executed when the absolute value of the steering angle detected is larger than the value of a predetermined steering angle.

20. A method according to claim 19, further comprising the steps of detecting the speed of the vehicle and setting said predetermined steering angle so as to decrease as the vehicle speed detected increases.

21. A method according to claim 13, further comprising the steps of controlling oil pressure by a control valve and increasing or decreasing the supporting force pressurized from oil pressure by a hydraulic actuator which is controlled by said control valve.

22. A method according to claim 13, wherein said step (c) further comprises the step of detecting the size of irregularities of said road surface forward and diagonally downward in front with respect to the vehicle body by an ultrasonic sensor attached to the front portion of the vehicle body.

23. A method according to claim 13, wherein said normal control adjusts an equivalent spring constant of said actuator to a first spring constant and said inverse spring control adjusts said equivalent spring constant of said actuator to a second spring constant lower than said first spring constant to lengthen the stroke of the wheels of the vehicle.