EP0010116A1 - Improvements in or relating to hydraulic actuator controls - Google Patents
Improvements in or relating to hydraulic actuator controls Download PDFInfo
- Publication number
- EP0010116A1 EP0010116A1 EP78300539A EP78300539A EP0010116A1 EP 0010116 A1 EP0010116 A1 EP 0010116A1 EP 78300539 A EP78300539 A EP 78300539A EP 78300539 A EP78300539 A EP 78300539A EP 0010116 A1 EP0010116 A1 EP 0010116A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- pilot
- spool
- valve
- main
- force
- 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.)
- Withdrawn
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B13/00—Details of servomotor systems ; Valves for servomotor systems
- F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
- F15B13/04—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor
- F15B13/042—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure
- F15B13/043—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure with electrically-controlled pilot valves
- F15B13/0435—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure with electrically-controlled pilot valves the pilot valves being sliding valves
Definitions
- the present invention relates to hydraulic actuator controls and more particularly to a device for controlling hydraulic actuator means responsively to an electrical input signal comprising a main valve having a fluid pressure operated main spool.for controlling the fluid supply to the actuator means, a pilot valve having a pilot spool for regulating the fluid pressure for operating the main spool, and an electrical force motor for producing a force dependent upon the electrical input signal and for applying such force to the pilot spool in opposition to a fluid pressure acting on the pilot spool.
- An object of the invention is to dispense with the closed servo loop including the flow sensor.
- Another object is to use the position of the main spool as an indication of the rate of fluid flow to the actuator means.
- the regulated fluid pressure for operating the main spool is also applied to the pilot spool in opposition to said force, whereby the position of the main spool, which is displaced by said regulated fluid pressure against a return spring, is determined by the electrical input signal.
- the rate of fluid flow to the actuator means is determined by the position of the main spool. Since the latter is itself determined by the electrical input signal in the device according to the invention, the magnitude of the electrical input signal can be used to obtain a measure of control of the speed of the actuator means without the need to provide a flow sensor and the associated closed servo loop.
- the fluid flow control device comprises a main control valve 20 and a pilot valve 19 for controlling the main valve 20.
- the main and pilot valves are arranged in separate valve blocks which are bolted together with the respective fluid ports in communication with one another to provide the desired hydraulic connections as hereinafter described.
- the main control valve 20 has a main spool 21 provided with lands 22, 23 and 24 for controlling communication between three inlet/outlet ports 27, 28 and 29 and two service ports 25 and 26 connected by lines 32 and 33 to a hydraulic actuator 100.
- a supply line 31 is connected to the inlet port 28 and the outlet ports 27 and 29 are connected by a line 30 to tank.
- the spool 21 is biassed towards its central neutral or null position by return springs 34 and 35 which are conveniently disposed in control chambers 36 and 37 at opposite ends of the spool 21.
- the main spool 21 is displaced from its neutral position by the application of a pressure difference between the chambers 36 and 37 by means of the pilot valve 19.
- the pilot valve 19 has a valve spool 40 which is provided with three lands 41,42 and 43 controlling fluid communication between a central inlet port 44 and drain ports 45 and 46 on the one hand, and control ports 47 and 48 on the other hand.
- the inlet port 44 is connected by a line 49 to the outlet of a pressure reducing valve 50 which serves to maintain a constant pressure in the line 49.
- the inlet to the pressure reducing valve 50 is connected to a supply line 51 which can, if desired, be connected to the same external supply as the line 31.
- the pressure reducing valve 50 can be arranged in the same valve block as the pilot valve 19 or in a separate port plate on which the valve blocks are directly or indirectly mounted.
- the pilot spool 40 can be displaced from its neutral position by means of a linear force motor 52 which is adapted to produce a force directly proportional to the electrical current applied thereto.
- the armature of the force motor 52 is supported on diaphragms which act as centering springs for the pivot spool 40..
- the control ports 47 and 48 are connected by respective control lines 53 and 54 to the control chambers 36 and 37 of the main control valve 20.
- the pilot valve 19 has annular feedback chambers 55 and 56 at the sides of the lands 41 and 43 facing the respective ends of the spool 40.
- the chambers 57 and 58 at the ends of the spool 40 are connected to a drain line 59 as are the drain ports 45 to 46.
- Pressures are applied to the feedback chambers 55 and 56 from the control chambers 36 and 37 of the main valve 20 via lines 70 and 71 which are connected respectively to the lines 53 and 54.
- the drawing shows the main spool 21 displaced to the right from the neutral or null position by the force motor 52 having been energized to displace the pilot spool 40 to the right, as shown, to connect the inlet port 44 to the control port 47 and the control port 48 to the drain port 46.
- the resulting pressure difference between the control chambers 36 and 37 is balanced by the increased compression of the spring 35, whereby this pressure difference is proportional to the displacement of the main spool 21 from its null position.
- This pressure difference is also applied to the pilot feedback chambers 55 and 56 in opposition to the force of the force motor 52 which is dependent on the magnitude of the energizing current.
- the pilot spool 40 is returned to its null position when the feedback force due to this pressure difference balances the applied force from the force motor.
- the rate of supply of hydraulic fluid to the actuator 100 is dependent on and generally substantially proportional to the displacement of the main spool 21 from neutral and therefore proportional to the magnitude of the energizing current fed to the force motor 52.
- the force motor 52 is energized in the opposite direction to connect the pilot inlet port 44 to the control port 48 and the control port 47 to the drain port 45 whereby the main spool 21 is displaced to the left from its null position.
- Bernoulli forces which exerted on the spool 21 by the fluid being controlled and which are themselves dependent on the rate of fluid flow and the valve pressure drop.
- the Bernoulli forces may or may not be significant, dependent upon the design of the main valve and the forces of the springs 34 and 35.
- the pilot valve 19 can be exactly the same construction as the flow control pilot valve of the control device described and illustrated in British Patent Specification No. 1,406,326.
- the main valve 20 can be of identical construction to that of the device of this prior patent.
- the device of the present invention can be made from the parts designed for the device of the prior patent. The only modifications are the omission of the flow sensor and an associated shuttle valve and the provision of extra drillings to provide the lines 70 and 71.
Abstract
A device for controlling a hydraulic actuator (100) has a fluid pressure operated main valve (20) controlled by a pilot valve (19). The force of a force motor (52) acting on the pilot spool (40) is opposed by a feedback force produced by the pressure difference applied by the pilot valve (19) to the main valve control chambers (36 and 37) and also applied to feedback chambers (55 and 56) of the pilot valve.
Description
- The present invention relates to hydraulic actuator controls and more particularly to a device for controlling hydraulic actuator means responsively to an electrical input signal comprising a main valve having a fluid pressure operated main spool.for controlling the fluid supply to the actuator means, a pilot valve having a pilot spool for regulating the fluid pressure for operating the main spool, and an electrical force motor for producing a force dependent upon the electrical input signal and for applying such force to the pilot spool in opposition to a fluid pressure acting on the pilot spool.
- Such a device is described in British Patent Specification No. 1,406,326 which discloses the use of a flow sensor for producing a pressure difference dependent upon the rate of fluid flow to the actuator means and for applying such pressure difference to the pilot spool in opposition to said force. By suitably designing the flow sensor as described in British Patent Specification No. 1,135,042, an accurate correlation between the magnitude of the electrical input signal and the speed of the actuator means over a wide range of flow rates can be obtained.
- However there are occasions when it is more important to avoid the risk of instability arising through the presence of a closed servo loop (including the flow dependent feedback from the flow sensor to the pilot spool) than it is to obtain an accurate correlation between input and output.
- An object of the invention is to dispense with the closed servo loop including the flow sensor.
- Another object is to use the position of the main spool as an indication of the rate of fluid flow to the actuator means.
- According to the present invention, the regulated fluid pressure for operating the main spool is also applied to the pilot spool in opposition to said force, whereby the position of the main spool, which is displaced by said regulated fluid pressure against a return spring, is determined by the electrical input signal.
- For a given hydraulic supply pressure to the main valve and a given load on the actuator means, the rate of fluid flow to the actuator means is determined by the position of the main spool. Since the latter is itself determined by the electrical input signal in the device according to the invention, the magnitude of the electrical input signal can be used to obtain a measure of control of the speed of the actuator means without the need to provide a flow sensor and the associated closed servo loop.
- The invention is further described, by way of example, with reference to the accompanying drawing which is a flow diagram of a fluid flow control device in accordance with the invention.
- The fluid flow control device comprises a
main control valve 20 and apilot valve 19 for controlling themain valve 20. The main and pilot valves are arranged in separate valve blocks which are bolted together with the respective fluid ports in communication with one another to provide the desired hydraulic connections as hereinafter described. - The
main control valve 20 has amain spool 21 provided withlands outlet ports service ports lines hydraulic actuator 100. Asupply line 31 is connected to theinlet port 28 and theoutlet ports line 30 to tank. Thespool 21 is biassed towards its central neutral or null position byreturn springs control chambers spool 21. Themain spool 21 is displaced from its neutral position by the application of a pressure difference between thechambers pilot valve 19. - The
pilot valve 19 has avalve spool 40 which is provided with threelands central inlet port 44 anddrain ports 45 and 46 on the one hand, andcontrol ports inlet port 44 is connected by aline 49 to the outlet of apressure reducing valve 50 which serves to maintain a constant pressure in theline 49. The inlet to thepressure reducing valve 50 is connected to asupply line 51 which can, if desired, be connected to the same external supply as theline 31. Thepressure reducing valve 50 can be arranged in the same valve block as thepilot valve 19 or in a separate port plate on which the valve blocks are directly or indirectly mounted. Thepilot spool 40 can be displaced from its neutral position by means of alinear force motor 52 which is adapted to produce a force directly proportional to the electrical current applied thereto. The armature of theforce motor 52 is supported on diaphragms which act as centering springs for thepivot spool 40.. Thecontrol ports respective control lines control chambers main control valve 20. - The
pilot valve 19 hasannular feedback chambers lands 41 and 43 facing the respective ends of thespool 40. Thechambers spool 40 are connected to adrain line 59 as are the drain ports 45 to 46. Pressures are applied to thefeedback chambers control chambers main valve 20 vialines lines - The drawing shows the
main spool 21 displaced to the right from the neutral or null position by theforce motor 52 having been energized to displace thepilot spool 40 to the right, as shown, to connect theinlet port 44 to thecontrol port 47 and thecontrol port 48 to thedrain port 46. The resulting pressure difference between thecontrol chambers spring 35, whereby this pressure difference is proportional to the displacement of themain spool 21 from its null position. This pressure difference is also applied to thepilot feedback chambers force motor 52 which is dependent on the magnitude of the energizing current. Thepilot spool 40 is returned to its null position when the feedback force due to this pressure difference balances the applied force from the force motor. - For a given supply pressure applied to the
inlet port 28 and a given load on theactuator 100 the rate of supply of hydraulic fluid to theactuator 100 is dependent on and generally substantially proportional to the displacement of themain spool 21 from neutral and therefore proportional to the magnitude of the energizing current fed to theforce motor 52. - To move the actuator in the other direction, the
force motor 52 is energized in the opposite direction to connect thepilot inlet port 44 to thecontrol port 48 and thecontrol port 47 to the drain port 45 whereby themain spool 21 is displaced to the left from its null position. - It should be mentioned that the forces of the
springs main spool 21 to the null position are supplemented by the so-called Bernoulli forces which exerted on thespool 21 by the fluid being controlled and which are themselves dependent on the rate of fluid flow and the valve pressure drop. The Bernoulli forces may or may not be significant, dependent upon the design of the main valve and the forces of thesprings - The
pilot valve 19 can be exactly the same construction as the flow control pilot valve of the control device described and illustrated in British Patent Specification No. 1,406,326. Likewise themain valve 20 can be of identical construction to that of the device of this prior patent. Thus the device of the present invention can be made from the parts designed for the device of the prior patent. The only modifications are the omission of the flow sensor and an associated shuttle valve and the provision of extra drillings to provide thelines - The provision of means for applying a feedback pressure difference to the
pilot spool 40 of thepivot valve 19 must not be confused with the application of the pressure drop across theactuator 100 to the pivot spool to obtain a pressure feedback for operation in the so-called "pressure control mode" as is also described in the aforementioned British Patent Specification No. 1,406,326. The application of a pressure difference to thefeedback chambers main spool 21.
Claims (4)
1. A device for controlling hydraulic actuator means responsively to an electrical input signal comprising a main valve having a fluid pressure operated main spool for controlling the fluid supply to the actuator means, a pilot valve having a pilot spool for regulating the fluid pressure for operating the main spool, and an electrical force motor for producing a force dependent upon the electrical input signal and for applying such force to the pilot spool in opposition to a fluid pressure acting on the pilot spool, characterised in that the regulated fluid pressure for operating the main spool (21) is also applied to the pilot spool (40) in opposition to said force, whereby the position of the main spool, which is displaced by said regulated fluid pressure against a return spring (34 or 35) is determined by the electrical input signal.
2. A device according to claim 1 characterised (1) in that a pressure reducer (50) providing the pilot fluid fed to the pilot jvalve (19) is disposed )in the same valve block as the pilot valve, the main valve (20) being in a separate valve block.
3. A device according to claim 1 characterised in that the pressure reducer (50) is arranged in a port plate on which the valve blocks are directly or indirectly mounted.
4. A device according to claim 1, 2 or 3 characterised in that the force of the return spring (1) see request to correct of November 30,1978 (34 or 35) is supplemented by Bernoulli forces acting on the main spool (21).
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP78300539A EP0010116A1 (en) | 1978-10-25 | 1978-10-25 | Improvements in or relating to hydraulic actuator controls |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP78300539A EP0010116A1 (en) | 1978-10-25 | 1978-10-25 | Improvements in or relating to hydraulic actuator controls |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0010116A1 true EP0010116A1 (en) | 1980-04-30 |
Family
ID=8186009
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP78300539A Withdrawn EP0010116A1 (en) | 1978-10-25 | 1978-10-25 | Improvements in or relating to hydraulic actuator controls |
Country Status (1)
Country | Link |
---|---|
EP (1) | EP0010116A1 (en) |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2800143A (en) * | 1952-07-21 | 1957-07-23 | North American Aviation Inc | Hydraulic regulating valve |
US3454031A (en) * | 1968-02-12 | 1969-07-08 | Ford Motor Co | Fluid pressure control system |
FR2121840A1 (en) * | 1971-01-14 | 1972-08-25 | Metz Gmbh Carl | |
DE2136873A1 (en) * | 1971-07-23 | 1973-02-01 | Servo Technik Gmbh | HYDRAULIC CONTROL UNIT |
FR2275716A1 (en) * | 1974-05-31 | 1976-01-16 | Yuken Kogyo Co Ltd | PROPORTIONAL ELECTROMAGNETIC VALVE FOR STEERING AND ACCELERATOR CONTROL |
-
1978
- 1978-10-25 EP EP78300539A patent/EP0010116A1/en not_active Withdrawn
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2800143A (en) * | 1952-07-21 | 1957-07-23 | North American Aviation Inc | Hydraulic regulating valve |
US3454031A (en) * | 1968-02-12 | 1969-07-08 | Ford Motor Co | Fluid pressure control system |
FR2121840A1 (en) * | 1971-01-14 | 1972-08-25 | Metz Gmbh Carl | |
DE2136873A1 (en) * | 1971-07-23 | 1973-02-01 | Servo Technik Gmbh | HYDRAULIC CONTROL UNIT |
FR2275716A1 (en) * | 1974-05-31 | 1976-01-16 | Yuken Kogyo Co Ltd | PROPORTIONAL ELECTROMAGNETIC VALVE FOR STEERING AND ACCELERATOR CONTROL |
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Legal Events
Date | Code | Title | Description |
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PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
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STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION HAS BEEN WITHDRAWN |
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AK | Designated contracting states |
Designated state(s): DE FR SE |
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18W | Application withdrawn | ||
RIN1 | Information on inventor provided before grant (corrected) |
Inventor name: WALTERS, RONALD BERNARD |