CA1248410A - Power transmission - Google Patents
Power transmissionInfo
- Publication number
- CA1248410A CA1248410A CA000525243A CA525243A CA1248410A CA 1248410 A CA1248410 A CA 1248410A CA 000525243 A CA000525243 A CA 000525243A CA 525243 A CA525243 A CA 525243A CA 1248410 A CA1248410 A CA 1248410A
- Authority
- CA
- Canada
- Prior art keywords
- pump
- pressure
- compensator
- load
- load sensing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B1/00—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders
- F04B1/12—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinder axes coaxial with, or parallel or inclined to, main shaft axis
- F04B1/26—Control
- F04B1/30—Control of machines or pumps with rotary cylinder blocks
- F04B1/32—Control of machines or pumps with rotary cylinder blocks by varying the relative positions of a swash plate and a cylinder block
- F04B1/324—Control of machines or pumps with rotary cylinder blocks by varying the relative positions of a swash plate and a cylinder block by changing the inclination of the swash plate
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Control Of Positive-Displacement Pumps (AREA)
- Reciprocating Pumps (AREA)
- Fluid-Pressure Circuits (AREA)
Abstract
Abstract of the Disclosure A variable displacement pump system including a pressure compensator for operating a pump adjusting mechanism to vary the displacement by applying hydraulic fluid to the pump adjusting mechanism and a spring biased piston applying a yielding force to the pump adjusting mechanism opposing the pressure compensator. A load sensing valve senses the pressure of the load to which fluid is supplied from the pump through a system valve and applies this load pressure to work in unison with the spring biased piston for purposes of urging the pump towards its maximum displacement.
Description
12~8410 This invention relates to variable displacement pump systems.
Backqround and SummarY of the Invention It is known to provide a variable displacement pump with a pressure compensatOr for operating a pump adjusting mechanism to vary the displacement of the pump and a spring biased piston which yieldingly opposes the pressure compensator.
It is also known to provide a load sensing valve which functions to vary the displacement of the pump and a spring biased piston which yieldingly opposes the load sensing compensator valve. The load sensing compensator is active as the primary pump control except when the pressure of the pump i5 at the limit set by the pressure compensator at which time the pressure compensator overrides the load sensing compensator. In addition, it is known to apply the fluid pressure delivered to a system or directional valve to work in unison with the spring biased piston.
One of the problems with such a system is that under heavy loads and when the connecting lines are short, the system tends to become unstable causing hydraulic pulsations and resultant oscillating movement of the load or device being controlled.
Accordingly, an objective of the present invention is to provide a variable displacement pump system which is more stable.
i24~34~0 In accordance with the invention, the load pressure as taken from a load sensing port or the system valve is connected to deliver this load pressure to the spring biased piston rather than using the output pressure of the pump to the spring biasing piston.
Description of the Drawinqs FIG. 1 is a schematic of a prior art system.
FIG. 2 is a schematic of a system embodying the invention.
Description It is believed that the variable displacement pump control system embodying the invention may best be understood by reference to FIG. 1 which is a hydraulic schematic of a prior art system such as that shown in United States patent 3,554,093.
As shown in Fig. 1, the variable displacement pump 10 may be of the variable swash plate type shown in the aforesaid patent and comprises a swash plate 11 that is movable to vary the displacement of axial pistons. A spring biased piston 12 yieldingly urges the swash plate 11 to a maximum displacement position. A larger yoke positioning piston 13 acts on the swash plate 11 in opposition to the spring biased piston 12.
Fluid from the pump 10 is directed to a load such as a hydraulic actuator through a line 14 to a system or directional valve 15, through a line 16 to the spring biased piston 12, and ~248410 through a line 17 to a pressure compensator 18. The pressure compensator 18 functions via the pilot valve 22 in a manner well known in the art to vary the displacement as the pressure increases above a limit set by the spring force on pilot valve 22. A load sensing compensator 19 is connected at one end by a line 20 downstream of the system valve to the pressure of fluid being delivered to the load by the system valve 15. The pump pressure via line 17-17a connects pump pressure to the opposite end of the postioning spool 13. The load sensing compensator ~9 is connected through lines 17b, 17c so that it functions to control the pressure applied to positioning spool 13. If the pressure of the pump is below the limit set by pilot 22, then the load sensing spool l9a of the load sensing compensator 19 controls the pump through the lines 17c, 17b to the positioning piston 13 to vary the di.splacement in a manner to deliver exactly the load flow required at a pump pressure above theload pressure, for example, 200 to 300 p.s.i. above the above load pressure.
This 200 to 300 p.s.i. difference is achieved by the spring preload in the load compensator 19.
It has been found that such a system is unstable under high loads resulting in pulsating of the fluid and oscillating of the device being controlled, particularly when flows are small.
Referring to FIG. 2, in accordance with the invention, the line 16 is eliminated and a line 21 extends from the line 20 downstream of system valve 14 to the spring biased piston 12 to deliver load pressure to the biasing piston 12.
~2484~
It has been found that such a system overcomes the problem of stability of the prior art system of FIG. 1.
Although the system has been described as used in connection with a variable displacement pump of the swash plate type, it will be understood by persons skilled in the art that it is also applicable to other types of pumps having differing pump adjusting mechanism for varying the displacement such as eccentric adjust~ent variable vane pumps and pumps using a rotating group housed in a tiltable yoke assembly.
Backqround and SummarY of the Invention It is known to provide a variable displacement pump with a pressure compensatOr for operating a pump adjusting mechanism to vary the displacement of the pump and a spring biased piston which yieldingly opposes the pressure compensator.
It is also known to provide a load sensing valve which functions to vary the displacement of the pump and a spring biased piston which yieldingly opposes the load sensing compensator valve. The load sensing compensator is active as the primary pump control except when the pressure of the pump i5 at the limit set by the pressure compensator at which time the pressure compensator overrides the load sensing compensator. In addition, it is known to apply the fluid pressure delivered to a system or directional valve to work in unison with the spring biased piston.
One of the problems with such a system is that under heavy loads and when the connecting lines are short, the system tends to become unstable causing hydraulic pulsations and resultant oscillating movement of the load or device being controlled.
Accordingly, an objective of the present invention is to provide a variable displacement pump system which is more stable.
i24~34~0 In accordance with the invention, the load pressure as taken from a load sensing port or the system valve is connected to deliver this load pressure to the spring biased piston rather than using the output pressure of the pump to the spring biasing piston.
Description of the Drawinqs FIG. 1 is a schematic of a prior art system.
FIG. 2 is a schematic of a system embodying the invention.
Description It is believed that the variable displacement pump control system embodying the invention may best be understood by reference to FIG. 1 which is a hydraulic schematic of a prior art system such as that shown in United States patent 3,554,093.
As shown in Fig. 1, the variable displacement pump 10 may be of the variable swash plate type shown in the aforesaid patent and comprises a swash plate 11 that is movable to vary the displacement of axial pistons. A spring biased piston 12 yieldingly urges the swash plate 11 to a maximum displacement position. A larger yoke positioning piston 13 acts on the swash plate 11 in opposition to the spring biased piston 12.
Fluid from the pump 10 is directed to a load such as a hydraulic actuator through a line 14 to a system or directional valve 15, through a line 16 to the spring biased piston 12, and ~248410 through a line 17 to a pressure compensator 18. The pressure compensator 18 functions via the pilot valve 22 in a manner well known in the art to vary the displacement as the pressure increases above a limit set by the spring force on pilot valve 22. A load sensing compensator 19 is connected at one end by a line 20 downstream of the system valve to the pressure of fluid being delivered to the load by the system valve 15. The pump pressure via line 17-17a connects pump pressure to the opposite end of the postioning spool 13. The load sensing compensator ~9 is connected through lines 17b, 17c so that it functions to control the pressure applied to positioning spool 13. If the pressure of the pump is below the limit set by pilot 22, then the load sensing spool l9a of the load sensing compensator 19 controls the pump through the lines 17c, 17b to the positioning piston 13 to vary the di.splacement in a manner to deliver exactly the load flow required at a pump pressure above theload pressure, for example, 200 to 300 p.s.i. above the above load pressure.
This 200 to 300 p.s.i. difference is achieved by the spring preload in the load compensator 19.
It has been found that such a system is unstable under high loads resulting in pulsating of the fluid and oscillating of the device being controlled, particularly when flows are small.
Referring to FIG. 2, in accordance with the invention, the line 16 is eliminated and a line 21 extends from the line 20 downstream of system valve 14 to the spring biased piston 12 to deliver load pressure to the biasing piston 12.
~2484~
It has been found that such a system overcomes the problem of stability of the prior art system of FIG. 1.
Although the system has been described as used in connection with a variable displacement pump of the swash plate type, it will be understood by persons skilled in the art that it is also applicable to other types of pumps having differing pump adjusting mechanism for varying the displacement such as eccentric adjust~ent variable vane pumps and pumps using a rotating group housed in a tiltable yoke assembly.
Claims
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE
IS CLAIMED ARE DEFINED AS FOLLOWS:
1.
A variable displacement hydraulic pump control system comprising a variable displacement pump including a pump adjust-ing mechanism comprising a hydraulic positioning piston means and spring biased piston means yieldingly opposing said positioning piston means, load sensing spool compensator means, said pump having an outlet and an inlet, first passage means connecting the outlet of the pump to one end of said load sensing spool compensator means for sensing the pressure at the outlet of the pump which is being delivered to a load, second passage means extending between said load sensing spool compensator means and said positioning piston means for moving said pump adjusting mechanism in response to activation of said load sensing spool compensator means, a system valve, third passage means between the outlet of said pump and said system valve, fourth passage means extending between the other end of said load sensing spool compensator means and said system valve, and fifth passage means between said fourth passage means downstream of said system valve and said spring biased piston means.
2.
The variable displacement pump control system set forth in claim 1 including pressure compensated piston means having one end connected to said first passage means, said pressure compensated means being connected in said second passage means and responsive to pressure in said second passage means to change the pressure to said positioning means and thereby vary the displacement of the pump adjusting mechanism when the pressure exceeds a predetermined amount.
IS CLAIMED ARE DEFINED AS FOLLOWS:
1.
A variable displacement hydraulic pump control system comprising a variable displacement pump including a pump adjust-ing mechanism comprising a hydraulic positioning piston means and spring biased piston means yieldingly opposing said positioning piston means, load sensing spool compensator means, said pump having an outlet and an inlet, first passage means connecting the outlet of the pump to one end of said load sensing spool compensator means for sensing the pressure at the outlet of the pump which is being delivered to a load, second passage means extending between said load sensing spool compensator means and said positioning piston means for moving said pump adjusting mechanism in response to activation of said load sensing spool compensator means, a system valve, third passage means between the outlet of said pump and said system valve, fourth passage means extending between the other end of said load sensing spool compensator means and said system valve, and fifth passage means between said fourth passage means downstream of said system valve and said spring biased piston means.
2.
The variable displacement pump control system set forth in claim 1 including pressure compensated piston means having one end connected to said first passage means, said pressure compensated means being connected in said second passage means and responsive to pressure in said second passage means to change the pressure to said positioning means and thereby vary the displacement of the pump adjusting mechanism when the pressure exceeds a predetermined amount.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US80852785A | 1985-12-13 | 1985-12-13 | |
| US808,527 | 1985-12-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1248410A true CA1248410A (en) | 1989-01-10 |
Family
ID=25199037
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000525243A Expired CA1248410A (en) | 1985-12-13 | 1986-12-12 | Power transmission |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0226125B1 (en) |
| JP (1) | JPH0819922B2 (en) |
| CN (1) | CN1007542B (en) |
| CA (1) | CA1248410A (en) |
| DE (1) | DE3678538D1 (en) |
| IN (1) | IN166532B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5183393A (en) * | 1992-02-10 | 1993-02-02 | Schaffner Larey D | Power limiter control for a variable displacement axial piston pump |
| US7797092B2 (en) * | 2006-11-06 | 2010-09-14 | Caterpillar Inc | Method and system for controlling machine power |
| CN101865143B (en) * | 2010-07-08 | 2012-05-23 | 中国航天科技集团公司第六研究院第十一研究所 | Device for automatically adjusting power of turbine pump |
| CN111911381B (en) * | 2020-07-26 | 2022-12-06 | 中国航发贵州红林航空动力控制科技有限公司 | Nozzle differential pressure valve mechanism with damping piston |
| CN113266319B (en) * | 2021-07-01 | 2023-06-23 | 龙信阀业集团有限公司 | Gas lift valve suitable for pressure-variable gas lift process |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2502546A (en) * | 1947-03-28 | 1950-04-04 | Denison Eng Co | Hydraulic apparatus |
| US3067693A (en) * | 1958-12-24 | 1962-12-11 | United Aircraft Corp | Control means for variable delivery pump |
| SE323286B (en) * | 1967-12-04 | 1970-04-27 | Sperry Rand Corp | |
| US4072442A (en) * | 1975-07-04 | 1978-02-07 | Takeshi Horiuchi | Variable delivery hydraulic pump |
-
1986
- 1986-12-02 IN IN870/CAL/86A patent/IN166532B/en unknown
- 1986-12-03 DE DE8686116785T patent/DE3678538D1/en not_active Expired - Fee Related
- 1986-12-03 EP EP86116785A patent/EP0226125B1/en not_active Expired - Lifetime
- 1986-12-11 JP JP61295683A patent/JPH0819922B2/en not_active Expired - Fee Related
- 1986-12-12 CN CN87105369A patent/CN1007542B/en not_active Expired
- 1986-12-12 CA CA000525243A patent/CA1248410A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| EP0226125B1 (en) | 1991-04-03 |
| IN166532B (en) | 1990-05-26 |
| EP0226125A2 (en) | 1987-06-24 |
| JPS62253980A (en) | 1987-11-05 |
| CN86108529A (en) | 1987-06-17 |
| DE3678538D1 (en) | 1991-05-08 |
| CN1007542B (en) | 1990-04-11 |
| EP0226125A3 (en) | 1989-07-05 |
| JPH0819922B2 (en) | 1996-03-04 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |