Hydrostatic drive, in particular hydrostatic fan drive

Patent metadata

Field	Value
Publication number	US-9587652-B2
Application number	US-201414445240-A
Country	US
Kind code	B2
Filing date	Jul 29, 2014
Priority date	Jul 30, 2013
Publication date	Mar 7, 2017
Grant date	Mar 7, 2017

Abstract

A hydrostatic fan drive is operated with a closed circuit and includes a variable-displacement pump with a swept volume that is configured to be adjusted by an adjustment device. The variable-displacement pump is connected by two working lines to a motor that is coupled fixedly in terms of torque to a fan impeller. The fan drive further includes a feed pressure pump and an adjustment pressure line by which the adjustment device is supplied with adjustment pressure medium. A pressure cut-off valve is connected to the adjustment pressure line. The pressure cut-off valve is configured to limit an adjustment pressure, as a function of a high pressure in the working line acting as high-pressure line, to a value such that a certain value of high pressure is not exceeded. The pressure cut-off valve is configured to exhibit pilot control to regulate a working pressure of the variable-displacement pump.

First claim

What is claimed is:

1. A hydrostatic drive, comprising:
a closed circuit including a variable-displacement pump with a swept volume configured to be adjusted by an adjustment device, the variable-displacement pump being configured to be connected via two working lines to a motor; and
an adjustment pressure supply configured to supply the adjustment device with adjustment pressure medium, the adjustment pressure supply having a pressure cut-off valve by which the maximum adjustment pressure is configured to be set as a function of a high pressure in one of the working lines,
whereby the swept volume of the variable-displacement pump is configured to be reduced,
wherein the pressure cut-off valve is pilot-controlled and has a high-pressure port connected to at least one of the working lines, an adjustment pressure port, and a leakage port,
wherein a pressure cut-off valve body of the pressure cut-off valve is loaded via the high-pressure port in a direction for opening a connection from the adjustment pressure port to the leakage port,
wherein a spring loads the pressure cut-off valve body in a closing direction,
wherein the pressure cut-off valve has a control pressure port via which the pressure cut-off valve body is configured to be loaded in an opening direction or in a closing direction, and
wherein the control pressure port is configured to be charged with control pressure medium via a pressure regulating valve.

2. The hydrostatic drive according to claim 1 , wherein the pressure cut-off valve is continuously adjustable.

3. The hydrostatic drive according to claim 1 , wherein the pressure regulating valve is connected at the inlet side to the adjustment pressure supply.

4. The hydrostatic drive according claim 3 , wherein the pressure cut-off valve body is configured to be loaded in an opening direction via the control pressure port.

5. The hydrostatic drive according to claim 4 , wherein, when the pressure regulating valve is in a main position, the control pressure port is charged with adjustment pressure medium, and wherein, when an actuator of the pressure regulating valve is energized, the control pressure port is relieved of pressure.

6. The hydrostatic drive according to claim 4 , wherein a control pressure acts on the pressure cut-off valve body via an annular surface formed on an encircling radial widening of the pressure cut-off valve body.

7. The hydrostatic drive according to claim 6 , wherein the spring of the pressure cut-off valve is accommodated in a spring chamber delimited by an annular face surface formed on the pressure cut-off valve body, wherein the pressure cut-off valve body has a longitudinal bore via which the spring chamber is connected to the leakage port and in which an end section of the plunger is arranged, the end section being configured to be brought to bear against the pressure cut-off valve body.

8. The hydrostatic drive according to claim 3 , wherein the pressure cut-off valve body is configured to be loaded in a closing direction via the control pressure port.

9. The hydrostatic drive according to claim 8 , wherein, when the pressure regulating valve is in a main position, the control pressure port is relieved of pressure, and wherein, when an actuator of the pressure regulating valve is energized, the control pressure port is charged with adjustment pressure medium.

10. The hydrostatic drive according to claim 8 , wherein the spring of the pressure cut-off valve is accommodated in a spring chamber delimited by a face surface formed on the pressure cut-off valve body, and wherein a control pressure acts on the pressure cut-off valve body via the face surface.

11. The hydrostatic drive according to claim 1 , wherein the variable-displacement pump is configured to be adjusted beyond a zero position, and wherein the two working lines are connected via a shuttle valve to the high-pressure control port of the pressure cut-off valve.

12. The hydrostatic drive according to claim 11 , wherein the pressure cut-off valve and the shuttle valve are accommodated in a common valve housing on which the control pressure port, the adjustment pressure port, the leakage port, and in each case one port for the two working lines are arranged.

13. The hydrostatic drive according to claim 12 , wherein the pressure cut-off valve body and a shuttle valve body of the shuttle valve are arranged in a valve bore of the valve housing, and wherein a plunger is disposed between the two valve bodies and configured to transmit to the pressure cut-off valve body a pressure force at the outlet of the shuttle valve, the pressure force acting counter to the force of the spring of the pressure cut-off valve.

14. The hydrostatic drive according to claim 13 , wherein the valve housing is of bushing-like or cartridge-like form, in which the valve bore, the pressure cut-off valve body, the shuttle valve body, the plunger, and the spring are arranged concentrically, and wherein the control pressure port, the adjustment pressure port, the leakage port, and the ports for the two working lines are formed as radial bores.

15. The hydrostatic drive according to claim 1 , wherein the hydrostatic drive is configured as a hydrostatic fan drive.

16. A hydrostatic variable-displacement pump, comprising:
an adjustment device configured to adjust a swept volume of the variable-displacement pump;
two working lines configured to connect the variable-displacement pump to a motor; and
an adjustment pressure supply configured to supply the adjustment device with adjustment pressure medium, the adjustment pressure supply having a pressure cut-off valve by which the maximum adjustment pressure is configured to be set as a function of a high pressure in one of the working lines,
whereby the swept volume of the variable-displacement pump is configured to be reduced,
wherein the pressure cut-off valve is pilot-controlled controlled and has a high-pressure port connected to at least one of the working lines, an adjustment pressure port, and a leakage port,
wherein a pressure cut-off valve body of the pressure cut-off valve is loaded via the high-pressure port in a direction for opening a connection from the adjustment pressure port to the leakage port,
wherein a spring loads the pressure cut-off valve body in a closing direction,
wherein the pressure cut-off valve has a control pressure port via which the pressure cut-off valve body is configured to be loaded in an opening direction or in a closing direction, and
wherein the control pressure port is configured to be charged with control pressure medium via a pressure regulating valve.

17. The hydrostatic variable-displacement pump according to claim 16 , wherein the hydrostatic variable-displacement pump is configured as an axial piston pump.

18. A hydrostatic drive, comprising:
a closed circuit including a variable-displacement pump with a swept volume configured to be adjusted by an adjustment device, the variable-displacement pump being configured to be connected via two working lines to a motor; and
an adjustment pressure supply configured to supply the adjustment device with adjustment pressure medium, the adjustment pressure supply having a pressure cut-off valve by which the maximum adjustment pressure is configured to be set as a function of a high pressure in one of the working lines,
whereby the swept volume of the variable-displacement pump is configured to be reduced,
wherein the pressure cut-off valve is pilot-controlled and has a high-pressure port connected to at least one of the working lines, an adjust

Assignees

• Bosch Gmbh Robert

Inventors

• Glaz Igor
• Loritz Steffen

Classifications

• E02F9/2285

  Pilot-operated systems · CPC title

• F15B2211/575

  Pilot pressure control · CPC title

• F15B2211/6333

  representing a state of the pressure source, e.g. swash plate angle · CPC title

• F16H61/431

  Pump capacity control by electro-hydraulic control means, e.g. using solenoid valves · CPC title

• F04D25/04

  the pump being fluid-driven {(pumps driven by exhaust gases F02B37/00, F02B39/00; turbochargers F02C6/12)} · CPC title