Vehicle height adjust control apparatus and method

• US 6,219,601 B1
• Filed: 10/05/1998
• Issued: 04/17/2001
• Est. Priority Date: 01/16/1998
• Status: Expired due to Term

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Harada, Kenji, Tabata, Masaaki, Hashimoto, Yoshiyuki, Kanatani, Masaki, Shono, Shoichi, Sato, Atushi
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Marc-Coleman, Marthe Y.
• Application Number:
  US09/166,076
• Time in Patent Office: 925 Days
• Field of Search: 701/36, 701/37, 701/38, 701/39, 280/5.T, 364/424.05
• US Class Current: 701/37
• CPC Class Codes: B60G 17/016 characterised by their responsiveness, when the vehicle is travelling, to specific motion, a specific condition, or driver input B60G17/017 takes precedence
• CPC Class Codes: B60G 17/018 characterised by the use of a specific signal treatment or control method
• CPC Class Codes: B60G 2500/02 Supply or exhaust flow rates; Pump operation
• CPC Class Codes: B60G 2500/30 Height or ground clearance
• CPC Class Codes: B60G 2600/182 Active control means
• CPC Class Codes: B60G 2800/164 Heaving; Squatting
• CPC Class Codes: B60G 2800/914 Height Control System

Abstract

A vehicle height adjust control apparatus and method adjusts an actual vehicle height to a target vehicle height using a microcomputer that controls an electric motor, leveling valves and an accumulator valve on the basis of the actual vehicle height detected by vehicle height sensors, so as to eliminate any deviation of the actual vehicle height from the target vehicle height. If a hydraulic fluid temperature detected by a fluid temperature sensor is very low or very high, the microcomputer suspends the vehicle height adjusting control and the supply of hydraulic fluid to an accumulator by stopping the operation of the electric motor and a hydraulic pump and/or switching the valves to a closed state. The suspending control thereby prevents very high and low viscosities of the hydraulic fluid, or very low and high fluidities thereof, which prevent an undesirable increase of the load on the hydraulic pump and an undesirable decrease of the ejecting performance thereof.

Claims

1. A vehicle height adjust control apparatus comprising:

a hydraulic actuator that increases and decreases a vehicle height using hydraulic fluid;

a hydraulic pump that ejects the hydraulic fluid;

a control valve provided in a fluid passage between the hydraulic pump and the hydraulic actuator that opens and closes the fluid passage;

a vehicle height detector that detects a vehicle height;

supply/discharge control means for controlling operation of the hydraulic pump and the opening and closing of the control valve so as to eliminate a deviation of the vehicle height detected by the vehicle height detector from a predetermined target vehicle height; and

delay control means provided in the supply/discharge control means for outputting an instruction to switch the control valve from an open state to a closed state at the lapse of a predetermined delay time following output of an instruction by the supply/discharge control means to switch the hydraulic pump from an operating state to a stopped state.

2. A vehicle height adjust control apparatus according to claim 1, further comprising:

a fluid temperature detector that detects a temperature of the hydraulic fluid; and

delay time correction means provided in the supply/discharge control means for increasing the predetermined delay time upon detection of a decrease in the temperature of the hydraulic fluid by the fluid temperature detector.

3. A vehicle height adjust control apparatus according to claim 1, further comprising:

a hydraulic pressure detector that detects a pressure of the hydraulic fluid supplied from the hydraulic pump to the hydraulic actuator; and

delay time correction means provided in the supply/discharge control means for increasing the predetermined delay time upon detection of an increase in the pressure of the hydraulic fluid detected by the hydraulic pressure detector.

4. A vehicle height adjust control apparatus comprising:

a hydraulic actuator that increases and decreases a vehicle height using hydraulic fluid;

supply/discharge means for enabling supply of the hydraulic fluid to the hydraulic actuator and discharge of the hydraulic fluid from the hydraulic actuator, the supply/discharge means having an electromagnetic on-off valve that controls passage of the hydraulic fluid;

a vehicle height detector that detects a vehicle height;

supply/discharge control means for controlling operation of the supply/discharge means so as to eliminate a deviation of the vehicle height detected by the vehicle height detector from a predetermined target vehicle height; and

duty ratio control means provided in the supply/discharge control means for controlling a duty ratio of the supply/discharge control means, wherein the duty ratio control means sets the duty ratio of voltage applied to the electromagnetic on-off valve immediately after voltage application thereto is started to a ratio that is greater than a subsequent applied duty ratio of voltage.

5. A method of adjusting vehicle height, comprising:

providing a hydraulic actuator that increases and decreases a vehicle height using hydraulic fluid;

providing a hydraulic pump that ejects the hydraulic fluid into the hydraulic actuator;

providing a control valve in a fluid passage between the hydraulic pump and the hydraulic actuator that opens and closes the fluid passage;

detecting a vehicle height;

controlling operation of the hydraulic pump and the opening and closing of the control valve so as to eliminate a deviation of the detected vehicle height from a predetermined target vehicle height; and

delaying the switching of the control valve from an open state to a closed state until after lapse of a predetermined delay time following an instruction to switch the hydraulic pump from an operating state to a stopped state.

6. A vehicle height adjust control apparatus comprising:

a hydraulic actuator that increases and decreases a vehicle height using hydraulic fluid;

supply/discharge means for enabling supply of the hydraulic fluid to the hydraulic actuator and discharge of the hydraulic fluid from the hydraulic actuator, the supply/discharge means having an electromagnetic on-off valve that controls passage of the hydraulic fluid;

a vehicle height detector that detects a vehicle height;

supply/discharge control means for controlling operation of the supply/discharge means so as to eliminate a deviation of the vehicle height detected by the vehicle height detector from a predetermined target vehicle height; and

duty ratio control means provided in the supply/discharge control means for controlling a duty ratio of the supply/discharge control means, wherein the duty ratio control means increases the duty ratio of voltage applied to the electromagnetic on-off valve when an output voltage of a battery provided for applying voltage to the electromagnetic on-off valve is decreased.

7. A vehicle height adjust control apparatus comprising:

a hydraulic actuator that increases and decreases a vehicle height using hydraulic fluid;

supply/discharge means for enabling supply of the hydraulic fluid to the hydraulic actuator and discharge of the hydraulic fluid from the hydraulic actuator, the supply/discharge means having an electromagnetic on-off valve that controls passage of the hydraulic fluid;

a vehicle height detector that detects a vehicle height;

supply/discharge control means for controlling operation of the supply/discharge means so as to eliminate a deviation of the vehicle height detected by the vehicle height detector from a predetermined target vehicle height;

a fluid temperature detector that detects a temperature of the hydraulic fluid; and

duty ratio control means provided in the supply/discharge control means for controlling a duty ratio of the supply/discharge control means, the duty ratio control means increasing the duty ratio of voltage applied to the electromagnetic on-off valve with detection of an increase in the temperature of the hydraulic fluid detected by the fluid temperature detector.