Pressure flow compensating control circuit

• US 4,821,514 A
• Filed: 09/11/1987
• Issued: 04/18/1989
• Est. Priority Date: 06/09/1987
• Status: Expired due to Fees

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Schmidt, Randy P., Brandau, Steven G., Stephenson, Dwight B., Miller, James A.
• Primary Examiner(s): Look, Edward K.
• Application Number:
  US07/096,418
• Time in Patent Office: 585 Days
• Field of Search: 417/213, 417/218, 417/219, 417/220, 417/221, 417/222, 60/445, 60/450, 60/452, 137/596, 137/596.13
• US Class Current: 60/452
• CPC Class Codes: F04B 49/08 Regulating by delivery pressure
• CPC Class Codes: F16H 61/433 Pump capacity control by fluid pressure control means
• CPC Class Codes: F16H 61/46 Automatic regulation in accordance with output requirements
• CPC Class Codes: F16H 61/468 for achieving a target input torque

Abstract

A control circuit and specific embodiments thereof are provided using a four-port infinitely variable pilot operated pressure-compensator spool valve and a three-port infinitely variable pilot operated load sense spool valve in series to regulate the output pressure of a variable displacement radial piston pump. The valves are so constructed that both must be correctly positioned to put the pump into full stroke, while either valve can de-stroke the pump. The three-port valve is pilot controlled between the load sense pressure and the outlet pressure, while the four-port valve is controlled between the pump inlet and outlet pressures. A check valve and orifice are positioned between the two control valves and the crankcase control line of the pump to assist in stabilizing the pump output. A relief valve is provided on the crankcase line to minimize output spikes. In an alternative embodiment, a single three-port valve is controlled between the inlet and outlet pressures of the pump. A relief valve is provided to vent spikes in the crankcase pressure, allowing down-sizing of the crankcase orifice.

Claims

1. A control circuit for a variable displacement pump having an inlet, an outlet connected to a load and a control line, said circuit comprising:

a load sense valve having a first port connected to the pump control line, a second port connectible to the pump inlet and a third port connected to the pump outlet, said load sense valve having one position connecting said first port to said second port and another position connecting said first port to said third port;

a load sense line having a pressure therein representative of the pressure supplied to the load;

means for controlling the position of said load sense valve based on the pressure differential between said pump outlet and said load sense line;

a pressure-compensator valve having a first port connected to said load sense valve second port, a second port connected to said load sense valve first port, a third port connected to said pump inlet and a fourth port connected to said pump outlet, said pressure-compensator valve having one position connecting its first and third ports while blocking communication between its second and fourth ports, and having another position blocking communication between its first and third ports while connecting its second and forth ports;

means for controlling the position of said pressure-compensator valve based on the pressure differential between said pump inlet and outlet;

flow limiting orifice means connecting said pump control line and said load sense valve first port;

check means connected in parallel to said orifice means, said check means allowing flow therethrough from said pump control line towards said load sense valve first port, while blocking flow therethrough from said load sense valve first port towards said pump control line; and

a relief valve for connecting said load sense valve first port to said pump inlet when the pressure differential therebetween exceeds a predetermined maximum.

2. The circuit of claim 1, wherein each of said valves is infinitely variable.

3. The circuit of claim 1, wherein each of said valves comprises a pilot operated spool valve.

4. The circuit of claim 1, wherein said pump is a radial piston pump, and said circuit further comprises second flow limiting orifice means connecting said pump inlet and control line.

5. The circuit of claim 1, further comprising flow limiting means for slowing the rate of response of said pressure-compensator valve control means.

6. A control valve for a variable displacement pump having an inlet, an outlet connected to a load and a control line, and wherein a load sense line is provided having a pressure therein representative of the load on the pump, said valve comprising:

a valve body having formed therein;

(i) first, second and third spool bores, one end of said first spool bore being connected to said load sense line;

(ii) first, second and third cross-bores interconnecting said first and second spool bores, said third cross-bore being connected to said pump outlet;

(iii) a fourth cross-bore connected to said second spool bore; and

(iv) fifth and sixth cross-bores, said fifth cross-bore connecting said fourth cross-bore with said third spool bore and said pump inlet, and said sixth cross-bore connecting said second cross-bore with said third spool bore and said pump control line;

a load sense spool in said first spool bore and having first and second lands formed thereon, said first land serving selectively to at least partially block said first spool bore between said first and second cross-bores and said second land serving selectively to at least partially block said first spool bore between said second and third cross-bores, one end of said load sense spool being exposed to the pressure in said load sense line and the other end of said load sense spool being exposed to the pressure at said pump outlet;

a pressure-compensator spool in said second spool bore and having first, second and third lands formed thereon, said first land serving selectively to at least partially block said second spool bore between the fourth and first cross-bores, said second land serving selectively to at least partially block said second spool bore between said first and second cross-bores, and said third land serving selectively to at least partially block said second spool bore between said second and third cross-bores, one end of said pressure-compensator spool being exposed to the pressure at said pump inlet and the other end of said load sense spool being exposed to the pressure at said pump outlet;

a relief spool in said third spool bore and having a land formed thereon serving to selectively to at least partially block said third spool bore between said fifth and sixth cross-bores; and

check-orifice means in said sixth cross-bore for allowing free flow therethrough from said pump inlet towards said second cross-bore and for allowing limited flow therethrough from said second cross-bore towards said pump inlet.

7. The control valve of claim 6, further comprising a seventh cross-bore connecting said third cross-bore to said pump outlet.

8. The control valve of claim 6, wherein said pressure-compensator spool has a flow limiting passage formed therein for conveying the pressure at said pump outlet from said third cross-bore to said pressure-compensator spool other end.

9. The control valve of claim 6, wherein said check-orifice means comprises a multi-legged body movable between a position allowing free flow through said sixth cross-bore and a position allowing only restricted flow between said legs and said sixth cross-bore.

10. The control valve of claim 6, further comprising spring means in each of said spool bores for biasing the respective spools.

11. The control valve of claim 10, wherein said spring means in said second spool bore is adjustable.

12. A control circuit for a variable displacement pump having an inlet, an outlet connected to a load and a control line, said circuit comprising:

pressure-compensator valve having a first port connected to the pump control line, a second port connected to the pump inlet and a third port connected to the pump outlet, said valve having one position connecting said first port to said second port and another position connecting said first port to said third port;

control means for controlling the position of said valve based upon the pressure differential between only said pump inlet and outlet pressure; and

relief means for connecting said first port to said pump inlet when the pressure differential therebetween exceeds a predetermined minimum.

13. The circuit of claim 12 wherein said valve is infinitely variable.

14. The circuit of claim 12 further comprising flow limiting means for slowing the rate of response of said control means.

15. The circuit of claim 12, wherein said pump is a radial piston pump and said circuit further comprises flow limiting orifice means connecting said pump inlet and control line.

16. A control valve for a variable displacement pump having an inlet, an outlet connected to a load and a control line, said valve comprising:

a valve body having;

(i) first and second spool bores formed therein; and

(ii) first, second, third and fourth cross-bores formed therein, said first, second and third cross-bores interconnecting said spool bores, and said first cross-bore being connected to said pump inlet, said third cross-bore to said pump control line and said fourth cross-bore to both said pump outlet and said first spool bore;

a pressure-compensator spool in said first spool bore and having first, second and third lands formed thereon, said first land serving selectively to at least partially block said first spool bore between said first and second cross-bores, said second land serving selectively to at least partially block said first spool bore between said second and third cross-bores, and said third land serving to at least partially block said first spool bore between said third and fourth cross-bores, the ends of said pressure-compensator spool being exposed to the pressure at the pump inlet and outlet, respectively; and

a relief spool in said second spool bore and having a land formed thereon serving selectively to at least partially block said second spool bore between said first and second cross-bores.

17. The control valve of claim 16, further comprising fifth, sixth and seventh cross-bores, said fifth, sixth and seventh cross-bores connecting said first, third and fourth cross-bores to said pump inlet, control line and outlet, respectively.

18. The control valve of claim 16, wherein said pressure-compensator spool has a flow limiting passage formed therein for conveying the pressure at said pump outlet from said fourth cross-bore to the end of said pressure-compensator spool exposed thereto.

19. The control valve of claim 16, further comprising spring means in each of said spool bores for biasing the respective spools.

20. The control valve of claim 19, wherein said spring means in said first spool bore is adjustable.