Hydraulic-pneumatic suspension system

• US 20050067239A1
• Filed: 08/05/2004
• Published: 03/31/2005
• Est. Priority Date: 08/16/2003
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Bauer, Wolfgang, Schwegler, Heinz
• Granted Patent: US 7,219,779 B2
• Time in Patent Office: Days
• US Class Current: 188/297
• CPC Class Codes: B60G 17/056 Regulating distributors or valves for hydropneumatic systemsB60G17/044 - B60G17/048, B60G17/0416 take precedence; Fluid interconnection systems to control vehicle inclination B60G21/06, B60G21/10; valves per se F16K
• CPC Class Codes: B60G 21/06 fluid
• CPC Class Codes: B60G 2202/154 with an accumulator
• CPC Class Codes: B60G 2202/413 Hydraulic actuator
• CPC Class Codes: B60G 2202/414 using electrohydraulic valves
• CPC Class Codes: B60G 2500/02 Supply or exhaust flow rates; Pump operation

Abstract

A hydro-pneumatic suspension system includes one or more hydraulic suspension cylinders mounted between the vehicle body and the axle. Each cylinder includes a piston chamber and rod chamber, each of which are connected to an accumulator and which can be connected to a pressure source and a tank by valve systems. The valve system for the rod chamber includes a first solenoid valve and a hydraulically and electrically actuated proportional pressure adjusting valve. The proportional valve is exposed to rod chamber pressure and to tank pressure. The rod chamber pressure can be applied on the proportional valve either directly as control pressure or can be detected with a sensor, and can be used to control the proportional valve. Such a system can influence the dependency of the suspension stiffness on the axle load and can be used to adjust the stiffness to ballast conditions and operating or driving states.

Claims

1. A hydro-pneumatic suspension system having at least one a hydraulic suspension cylinder, the cylinder having a piston chamber and a rod chamber each connected to at least one accumulator and valve systems for controlling communication between said chambers and a pressure source and a tank, characterized by:

a rod chamber valve system for controlling communication between the rod chamber and the pressure source and the tank, the rod chamber valve system comprises a first solenoid valve and an electrically controlled proportional valve for adjusting the pressure in the rod chamber.

2. The suspension system of claim 1, further comprising:

a pressure sensor for sensing the pressure in the rod chamber, the proportional valve being controlled as a function of a signal from said pressure sensor.

3. The suspension system of claim 1, wherein:

the proportional valve is responsive to pressure of the rod chamber and to tank pressure.

4. The suspension system of claim 1, wherein:

the first solenoid valve includes a check valve function in a closed position which prevents a fluid outflow from the rod chamber.

5. The suspension system of claim 1, wherein:

the first solenoid valve includes a bidirectional check valve function in a closed position which prevents fluid flow in both directions.

6. The suspension system of claim 1, further comprising:

a flow limiting flow restriction connected between the first solenoid valve and the proportional valve.

7. The suspension system of claim 1, wherein:

the proportional valve is an electromagnetically controlled proportional pressure control valve.

8. The suspension system of claim 7, wherein:

the proportional pressure control valve has a un-energized tank position wherein it connects a rod chamber port to a tank port, and an energized position wherein it connects a pressure source port to a rod chamber port.

9. The suspension system of claim 8, wherein:

a return spring is biased to urge the proportional pressure control valve to the tank position.

10. The suspension system of claim 9, wherein:

rod chamber pressure acts upon the proportional pressure control valve in a same direction as a force of the return spring, and tank pressure acts upon the proportional pressure control valve in a same direction as an electromagnetic force.

11. The suspension system of claim 1, wherein:

the proportional valve is an electromagnetically controlled proportional pressure limiting valve.

12. The suspension system of claim 11, wherein:

the proportional pressure limiting valve includes an energized position wherein it connects a rod chamber port to a tank port and an un-energized position blocking said connection.

13. The suspension system of claim 11, wherein:

the proportional pressure limiting valve includes a return spring which urges the proportional pressure limiting valve into a blocking position.

14. The suspension system of claim 13, wherein:

tank pressure acts upon the proportional pressure control valve in a same direction as the force of the return spring, and rod chamber pressure acts upon the proportional pressure control valve in a same direction as an electromagnetic force.

15. The suspension system of claim 11, further comprising:

a first line extending between the solenoid valve and the proportional pressure limiting valve, and a pressure line connecting the first line to the pressure source.

16. The suspension system of claim 15, wherein:

the pressure line includes a flow restriction therein.

17. The suspension system of claim 15, wherein:

a second solenoid valve is arranged in the pressure line, the second solenoid valve having a closed position which prevents a fluid outflow from the pressure source.

18. The suspension system of claim 1, wherein:

the pressure source includes a load sensing pump with a control port, and a control line connects the control port to the first solenoid valve and to the proportional valve.

19. The suspension system of claim 18, wherein:

the control line is connected to the tank via a flow restriction.

20. The suspension system of claim 18, further comprising:

a shuttle valve has a first inlet connected to the control line, a second inlet connected to a piston chamber load sensing line and an outlet connected to the control port of the load sensing pump.