Working fluid circuit with line pressure control for vehicle active suspension system

• US 5,160,161 A
• Filed: 02/21/1991
• Issued: 11/03/1992
• Est. Priority Date: 02/23/1990
• Status: Expired due to Fees

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Tsukamoto, Masahiro, Kawabata, Kazunobu
• Primary Examiner(s): Mitchell, David M.
• Assistant Examiner(s): DICKSON, PAUL N
• Application Number:
  US07/658,610
• Time in Patent Office: 621 Days
• Field of Search: 280/707, 280/709, 280/714, 364/424.05
• US Class Current: 280/5.501
• CPC Class Codes: B60G 17/017 characterised by their use when the vehicle is stationary, e.g. during loading, engine start-up or switch-off
• CPC Class Codes: B60G 2400/10 Acceleration; Deceleration
• CPC Class Codes: B60G 2400/252 vertical
• CPC Class Codes: B60G 2500/30 Height or ground clearance
• CPC Class Codes: B60G 2600/08 Failure or malfunction detecting means
• CPC Class Codes: B60G 2600/26 Electromagnets; Solenoids

Abstract

An active suspension system for an automotive vehicle is provided. This suspension system includes generally a hydraulic circuit which supplies pressurized fluid to hydraulic cylinders for controlling vehicle height and attitude. The hydraulic circuit includes a line pressure holding unit and a line pressure control unit. The line pressure holding unit is operable to hold the line pressure when the line pressure is lowered below a preselected pressure level after stopping supply of the pressurized fluid to the hydraulic cylinders. The line pressure control unit restricts a flow rate of the pressurized fluid to the hydraulic cylinders to build up the line pressure gradually until the line pressure reaches the preselected pressure level after starting the supply of pressurized fluid to the hydraulic cylinders to allow smooth adjustment of vehicle height and attitude.

Claims

1. An active suspension system for an automotive vehicle, comprising:

suspension assemblies disposed between a vehicle body and suspension members which respectively support vehicle wheels rotatably, each of the suspension assemblies including a fluid cylinder with adjustable cylinder pressure for active suspension control;

a fluid power source unit which supplies fluid pressurized above a preselected pressure level required for the active suspension control to the fluid cylinders;

a fluid circuit including supply and return lines which communicate between the fluid cylinders and said fluid power source unit for circulating the pressurized fluid therebetween;

line pressure holding means responsive to a line pressure provided to the fluid cylinders lower than a preselected pressure level for holding the line pressure in said fluid circuit;

a pressure sensor which detects the line pressure to provide a signal indicative thereof;

an abnormal operation sensor which detects malfunction of system operation to provide a signal indicative thereof;

valve means including an orifice and a fail-safe valve, the orifice being disposed in the supply line which provides fluid flow at a first flow rate, the fail-safe valve being arranged parallel to said orifice for providing fluid flow at a second flow rate higher than the first flow rate, said fail-safe valve having first and second valve positions, the first valve position being to block the fluid flow at the second flow rate and the second valve position being to allow the fluid flow at the second flow rate, said fail-safe valve means being adapted to establish the first valve position when system operation starts; and

a controller responsive to the signal from said abnormal operation sensor to provide a first control signal to the fail-safe valve for blocking the supply line of said fluid circuit downstream from said line pressure holding means and connecting the blocked supply lines upstream and downstream from said fail-safe valve with the return line respectively, said controller being further responsive to the signal from said pressure sensor to determine an operation status of said line pressure holding means to provide a second control signal to the fail-safe valve to change from the first valve position to the second valve position when operation of the line pressure holding means is released.

2. An active suspension system for an automotive vehicle, comprising:

suspension assemblies disposed between a vehicle body and suspension members which respectively support vehicle wheels rotatably, each of the suspension assemblies including a fluid cylinder with adjustable cylinder pressure for active suspension control;

a fluid power source unit which supplies fluid pressurized above a preselected pressure level required for the active suspension control to the fluid cylinders;

a fluid circuit, including supply and return lines which communicate between the fluid cylinders and said fluid power source unit for circulating the pressurized fluid therebetween;

line pressure holding means responsive to line pressure provided to the fluid cylinders lower than a preselected pressure level, for providing an enclosed loop downstream from said fluid power source which includes the fluid cylinders to hold the line pressure in the enclosed loop;

a vehicle height sensor which detects a vehicle height level to provide a signal indicative thereof;

a controller responsive to the signal from said vehicle height sensor to determine a change rate of the vehicle height level and provide a signal indicating that operation of said line pressure holding means is released when the change rate is less than a preselected threshold rate;

valve means including an orifice and a directional control valve arranged parallel to each other in the supply line, the orifice providing fluid flow at a first flow rate, the directional control valve providing fluid flow at a second flow rate higher than the first flow rate, the directional control valve having first and second valve positions, the first valve position being to block the fluid flow at the second flow rate, the second valve position being to allow the fluid flow at the second flow rate, the directional control valve being adapted to establish the first valve position when system operation starts and being responsive to the signal from said controller to change from the first valve position to the second valve position.

3. An active suspension system for an automotive vehicle, comprising:

suspension assemblies disposed between a vehicle body and suspension members which respectively support vehicle wheels rotatably, each of the suspension assemblies including a fluid cylinder with adjustable cylinder pressure for active suspension control;

a fluid power source unit which supplies fluid, pressurized above a preselected pressure level required for active suspension control, to the fluid cylinders;

a fluid circuit including supply and return lines which communicate between the fluid cylinders and said fluid power source unit for circulating the pressurized fluid therebetween;

pressure control valves each disposed between said fluid power source and the fluid cylinder for controlling fluid pressure supplied from said fluid power source to the fluid cylinder for effecting the active suspension control;

line pressure holding means, responsive to line pressure provided to the fluid cylinders lower than a preselected pressure level, for providing an enclosed loop downstream from said fluid power source which includes the fluid cylinders, to hold the line pressure in the enclosed loop;

a first sensor detecting a first pressure upstream from said pressure control valves to provide a signal indicative thereof;

a second sensor detecting a second pressure downstream from said pressure control valves to provide a signal indicative thereof;

valve means, disposed between said line pressure holding means and the fluid cylinders, for providing fluid flow from said fluid power source unit to the fluid cylinders at a first flow rate and a second flow rate higher than the first flow rate; and

a controller providing a first control signal to said valve means when system operation starts for blocking the fluid flow at the second flow rate and allowing the fluid flow at the first flow rate, said controller being responsive to respective signals from said first and second sensors to determine an operational status of said line pressure holding means to provide a second control signal to said valve means for allowing fluid flow at the second flow rate when operation of said line pressure holding means is released.

4. An active suspension system for an automotive vehicle, comprising:

suspension assemblies disposed between a vehicle body and suspension members which respectively support vehicle wheels rotatably, each of the suspension assemblies including a fluid cylinder with adjustable cylinder pressure for active suspension control;

a fluid power source unit which supplies fluid pressurized above a preselected pressure level required for active suspension control to the fluid cylinders;

a fluid circuit, including supply and return lines which communicate between the fluid cylinders and said fluid power source unit for circulating the pressurized fluid therebetween;

line pressure holding means responsive to line pressure provided to the fluid cylinders lower than a preselected pressure level, for providing an enclosed loop downstream from said fluid power source which includes the fluid cylinders, to hold the line pressure in the enclosed loop;

an orifice disposed in the supply line for providing fluid flow at a first flow rate and

a directional control valve having an inlet port communicating with a portion of the supply line upstream from said orifice and an outlet port communicating with a portion of the supply line downstream from said orifice, said directional control valve being responsive to a line pressure in the supply line introduced through the inlet port which is greater than said preselected pressure level to establish fluid communication between the inlet and outlet ports for providing fluid flow at a second flow rate higher than the first flow rate.

5. An active suspension system as set forth in claim 4, wherein:

said directional control valve is arranged downstream from said line pressure holding means.

6. An active suspension system as set forth in claim 5, further comprising:

a fail-safe valve disposed downstream from said directional control valve, the fail-safe valve being responsive to a signal indicating malfunction of system operation to block the supply line of said fluid circuit downstream from said line pressure holding means and connecting the blocked supply lines upstream and downstream from said fail-safe valve with the return line respectively.

7. An active suspension system as set forth in claim 4, wherein:

said directional control valve includes a poppet and a spring urging the poppet to block fluid communication between the inlet and outlet ports under a line pressure introduced through the inlet port of less than the preselected pressure level and to allow fluid communication between the inlet and outlet ports under a line pressure introduced through the inlet port greater than the preselected pressure level.

8. An active suspension system for an automotive vehicle, comprising:

suspension assemblies disposed between a vehicle body and suspension members which respectively support vehicle wheels rotatably, each of the suspension assemblies including a fluid cylinder with adjustable cylinder pressure for active suspension control;

a fluid power source unit which supplies fluid pressurized above a preselected pressure level required for active suspension control to the fluid cylinders;

a fluid circuit including supply and return lines which communicate between the fluid cylinders and said fluid power source unit for circulating the pressurized fluid therebetween;

line pressure holding means responsive to line pressure provided to the fluid cylinders lower than a preselected pressure level, for providing an enclosed loop downstream from said fluid power source, which includes the fluid cylinders, to hold the line pressure in the enclosed loop; and

a directional control valve, disposed in the supply line, having an orifice therein which provides fluid flow at a first flow rate, said directional control valve including first and second valve positions, the first valve position being to provide fluid flow at a second flow rate higher than the first flow rate, the second valve position being to block the fluid flow at the second flow rate and allow the fluid flow at the first flow rate through the orifice, said directional control valve being responsive to a pressure difference between portions of the return line upstream and downstream of said line pressure holding means, said directional control valve establishing the first valve position when the pressure difference is substantially equal to zero.

9. An active suspension system as set forth in claim 8, wherein:

said line pressure holding means includes a check valve disposed in the supply line which allows fluid flow from said fluid power source to said suspension assemblies and blocking back flow to said fluid power source and a pilot-operated check valve disposed in the return line which allows fluid flow in the return line to said fluid power source and blocks back flow to said suspension assemblies, said pilot-operated check valve being also responsive to line pressure in the supply line downstream from said check valve which is less than said preselected pressure level to block the fluid flow in the return line to said fluid power source, said directional control valve establishing the first valve position when online pressures upstream and downstream of the pilot-operated check valve are equal to each other.

10. An active suspension system as set forth in claim 9, further comprising:

a fail-safe valve disposed downstream from said directional control valve, the fail-safe valve being responsive to a signal indicating malfunction of system operation to block the supply line of said fluid circuit downstream from said line pressure holding means and connecting the blocked supply lines upstream and downstream from said fail-safe valve with the return line respectively, said pilot-operated check valve being responsive to line pressure in the supply line downstream from said fail-safe valve which is less than said preselected pressure level to block fluid flow from the return line to said fluid power source.