WO1982001402A1 - Systeme de commande pour une vanne pilote - Google Patents

Systeme de commande pour une vanne pilote Download PDF

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Publication number
WO1982001402A1
WO1982001402A1 PCT/US1980/001339 US8001339W WO8201402A1 WO 1982001402 A1 WO1982001402 A1 WO 1982001402A1 US 8001339 W US8001339 W US 8001339W WO 8201402 A1 WO8201402 A1 WO 8201402A1
Authority
WO
WIPO (PCT)
Prior art keywords
spool
pilot
passageway
chamber
fluid
Prior art date
Application number
PCT/US1980/001339
Other languages
English (en)
Inventor
Tractor Co Caterpillar
Original Assignee
Mcmillan William D
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Mcmillan William D filed Critical Mcmillan William D
Priority to PCT/US1980/001339 priority Critical patent/WO1982001402A1/fr
Priority to BE0/206069A priority patent/BE890501A/fr
Publication of WO1982001402A1 publication Critical patent/WO1982001402A1/fr

Links

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
    • F15B13/0401—Valve members; Fluid interconnections therefor
    • F15B13/0402—Valve members; Fluid interconnections therefor for linearly sliding valves, e.g. spool valves

Definitions

  • This invention relates in general to a hydraulic control system and, more particularly, to a control system for a pilot operated valve that permits shifting of the valve spool in response to the position thereof in the valve body without providing additional pilot pressure.
  • Earthmoving vehicles such as wheel and track dozers and loaders
  • grading, clearing, and snow removal operations where it is desirable that the ground engaging implement or work tool follow the contour of the supporting surface.
  • such vehicles are equipped with an implement hydraulic circuit, which, when placed in the so called "float" mode, permits the work tool to rest on the supporting surface by virtue of the force of gravity acting thereon and thereby follow the supporting surface contour.
  • Hydraulic systems employed in this type of vehicle to control the raising and lowering of the work tool commonly include a pilot operated control valve having a control spool shiftable in response to a shifting force resulting from selectively directing pilot pressure thereto.
  • the work tool is controlled by shifting the spool in the control valve to either a power up or raise position, a neutral or hold position, or a power down or lower position.
  • the float position is commonly obtained by shifting the control circuit spool to a fourth position beyond power down.
  • This type of float requires additional spool travel in the lower direction over that required in the raised direction. In a pilot operated system this additional spool travel requires a considerable increase in shifting force above what is required to attain the power up or power down positions. Thus, a proportional amount of pilot supply pressure must be reserved for this additional shift, and the pilot pressure range alloted for raise and lower modulation is reduced.
  • Prior art pilot operated control systems employ pilot control pumps and control systems that provide added pilot pressure to obtain additional spool travel in response to shifting of an infinitely variable pilot valve.
  • shifting of the pilot valve results in a metering effect, in that the pilot pressure delivered to the control spool varies in a relationship directly proportional to the displacement of the pilot control valve, thereby providing a higher pilot supply pressure than the normal shift pressure to achieve the additional spool travel.
  • this is accomplished by providing a control system for a pilot operated valve including means for shifting the spool in the control valve by changing the magnitude of the shifting force acting thereon in response to the position of the spool in the valve without changing the magnitude of the pilot pressure.
  • the drawing is a schematic view of a hydraulic system including a pilot operated control valve having a control system constructed in
  • a hydraulic system for directing pressurized fluid to a fluid powered actuator or hydraulic jack 10 is illustrated generally by the numeral 12.
  • the hydraulic system includes an operating circuit 13 for supplying fluid at a preselected operating pressure to the actuator, and a control system 14 for controlling flow of the operating fluid to the actuator.
  • the actuator 10 includes a housing 16 having a cylindrical bore 18, a reciprocating or telescoping piston 20 disposed in the bore, and an elongate rod 21 secured at a first end 22 to the piston and including a second end 23 extending from the actuator housing for manipulation of a work implement or tool (not shown) .
  • the piston is slidably engaged in the bore and defines a head end chamber 24 and a rod end chamber 25 within the housing.
  • the operating circuit 13 includes a fluid reservoir 30 and a source of pressurized fluid or pump 32 which draws fluid from the reservoir via a conduit 33. Fluid from the pump is communicated to a pilot operated control valve 34 of the control system 14 via a conduit 35 and thereafter, selectively to either the head end chamber 24 or the rod end chamber 25 of the actuator 10 via conduits 36 and 37 respectively.
  • a relief valve 38 disposed in a conduit 39 intermediate the conduit 35 and the reservoir controls the maximum pressure in the operating circuit.
  • control system 14 includes, in addition to the pilot operated control valve 34, a reservoir 40, a source of pressurized pilot fluid or pilot pump 42 which draws pilot fluid
  • the pump delivers pilot fluid to the pilot control valve 44 via a conduit 45 at a preselected maximum pressure controlled by a relief valve 46 disposed in a conduit 47 intermediate the conduit 45 and the reservoir.
  • the pilot control valve 44 is in fluid communication with the pilot operated valve 34 via conduits 48, conduit 49 and shifting means 50, and with the reservoir via a conduit 51 and has three operating positions for conditioning the pilot operated valve. These positions include a first operating position 52 for extending the actuator, a second neutral position 54, and a third operating position 56 for retracting the actuator.
  • the pilot operated control valve 34 includes a body portion or a housing 60 having a first end 61, a second end 62, an open-ended bore 63 extending between the first and second ends, and a spool 64 reciprocally disposed in the bore.
  • the spool includes a plurality of lands 65, 66, 67, 68, 69 and is selectively positionable in response to fluid directed thereto by the pilot control valve 44 to a first operating position for extending the actuator, a second neutral position (as shown in the drawing), a third operating position for retracting the actuator, and a fourth or float position.
  • Each of the lands 65-68 preferably includes at least one slot 70 to provide a metering effect of the fluid flow therethrough and thus more precise control over the actuator.
  • the control valve housing 60 includes a plurality of annular chambers 72, 73, 74, 75, 76
  • the annular chambers 72 and 76 are fluid drain passages which are interconnected to the reservoir 30 via drain ports 80 and 81 and conduits 82 and 83 respectively.
  • the annular chamber 73 is in fluid communication with the head end chamber 24 of the actuator 10 via a passageway 84 and the conduit 36, and the annular chamber 75 is in fluid communication with the rod end chamber 25 of the actuator via a passageway 85 and the conduit 37.
  • the annular chamber 74 is in fluid communication with the annular chambers 73 and 75 via the bore and is in fluid communication with the pump 32 via the conduit 35 and a passageway 86.
  • a housing or end cap 90 is secured thereto and includes an open ended bore 91 having a radially extending end face 92.
  • An annular spacer 95 having an inwardly extending annular lip or stop portion 96 is slidably disposed in the chamber and urged into abutment with the first end of the valve > body by. spring biasing means 97.
  • a cylindrical guide member or spring retainer 98 having a cylindrical bore 99 extending therethrough and a radially outwardly extending flange portion 100 is reciprocally positioned coaxially within the annular spacer and in abutment with the spool 64.
  • An urging means 102 is provided in the end cap for continuously biasing the spool toward the neutral operating position.
  • the urging means 102 is a
  • the shifting means 50 includes a housing or end cap 110 secured thereto having an internal cavity 111 defined by a radially extending end face 112 and a stepped bore 113 having a first diameter and a second, larger diameter separated by a step or shoulder 114.
  • a piston 120 having first and second axially spaced end faces 121 and 122 is reciprocatingly disposed in the portion of the bore having the smaller diameter and cooperates with the second end of the valve body and. the housing in defining first and second chambers 123 and 124.
  • An annular recess 125 positioned intermediate the end faces of the piston 120 extends- circumferentially thereabout, and a fluid passageway 126 extending transversely through the piston interconnects diametrically opposed portions of the recess.
  • a recess 127 formed in the first end face 121 of the piston is in fluid communication via an axially extending passageway 128 with the transversely extending passageway 126 and includes a seat portion 129 adapted to receive a ball 130 and a retaining cap 131 having a plurality of vent passageways 132 extending therethrough.
  • the second end face 122 of the piston has a cavity 133 formed therein and includes a retaining lip 134 adapted to receive a transversely extending flange or head 135 secured to a stem 136 extending axially outwardly from the spool 64.
  • a seat 137 having a bearing 138 disposed therein intermediate the head portion of the stem and the piston, is formed in the cavity, and a second axially extending passageway 139 communicates the cavity with the passageway 126 extending transversely through the piston.
  • a cylindrical guide member or spring retainer 150 having a radially outwardly extending flange 151, is slidably disposed in the second chamber 124 over the stem 136 extending from the spool 64 and includes an axially outwardly facing flat surface portion 152.
  • Urging means 153 is provided in the housing 110 for continuously biasing the spool toward the neutral operating position.
  • the urging means 153 is a coiled metal compression spring coaxially disposed in the second chamber over the cylindrical guide member intermediate the radially outwardly extending flange thereof and the step 114 in the bore 113.
  • the first end chamber 123 is in fluid communication with the pilot control valve via a passageway 160 and the conduit 49.
  • the stepped bore 113 of the housing 110 is in fluid communication with the reservoir 40 via a drain port 161 and a conduit 162.
  • a make-up valve 163 is in fluid communication with the second chamber 124 and the reservoir 40 via a passageway 164 and a conduit 165 to permit additional fluid to be drawn into the second chamber should pressure lower than that in the reservoir be experienced thereat.
  • control system of the present invention has application wherever it is desirable to obtain additional valve spool travel in a pilot operated valve without increasing the magnitude of the pilot pressure.
  • One such application is in a track or wheel dozer or loader having a pilot operated control valve including a float position to permit the implement or work tool to follow the contour of the ground.
  • Extension of the actuator 10 to raise the implement is achieved by shifting the pilot control valve 44 to the first operating position 52. Pilot fluid is communicated via the conduit 48 and the passageway 94 to the chamber 93. The pilot fluid pressure exerted on the exposed end surface area of the spool 64 generates a force sufficient to shift the spool to the right as viewed in the drawing against the opposing force exerted by the spring 153. Pilot fluid in the chamber 123 is vented to the reservoir 40 via passageway 160, conduit 49, the pilot control valve, and conduit 51. Operating fluid from the pump 32 is directed by the conduit 35 and the passageway 86 via the annular chambers 74 and 73, the bore 63, passageway 84 and conduit 36 to the head end chamber 24 of the actuator.
  • Fluid in the rod end chamber 25 is forced into the rod end conduit 37, through the passageway 85 into the annular chambers 75 and 74 and the bore 63 in response to movement of the piston 20, whereupon it is communicated via the drain port 81 and the conduit 83 to the reservoir 30. Movement of the actuator can continue until the piston travels the full length of the bore,18; however, movement of the piston and extension of the actuator may be stopped at any intermediate position by the operator by returning the pilot control valve to the neutral position 54. Thereupon the force exerted by the spring 153 urges the spool in the control valve to its neutral position, and fluid in the chamber 93 is vented via the passageway 94 and the conduit 48 to the reservoir 40.
  • the operator shifts the pilot control valve 44 to its second operating position 56 whereupon fluid from the pilot pump 42 is communicated to the first chamber 123.
  • the pilot shifting pressure creates a shifting force on the first end face 121 of the piston 120. This force is opposed by the force of the spring 102 acting through the spool 64 and fluid trapped in the second chamber 124 acting upon the second end face 122 of the piston.
  • the trapped fluid in the second chamber also acts upon the exposed surface area of the spool and aides the shifting force acting on the first surface of the piston.
  • the excess fluid in chamber 124 that is being displaced will cause ball 130 to be moved from its seat, thus, the result is a shifting force
  • OMPI equal to the pilot pressure acting upon an area equivalent to the exposed spool surface area opposed by the force of the spring, which results in a net force sufficient to move the spool to the left as viewed in the drawing.
  • Pilot fluid in the housing 90 is vented to the reservoir 40 via passageway 94, conduit 48, the pilot control valve, and conduit 50 in response to shifting of the spool.
  • Operating fluid from the pump 32 is communicated to the rod end chamber 25 of the actuator via annular chambers 74 and 75, the bore 63, passageway 85, and conduit 37.
  • fluid in the head end chamber 24 of the actuator is forced via conduit 36, passageway 84, annular chambers 73, 72, the bore 63, port 80, and conduit 82 to the reservoir 30.
  • movement of the piston can continue until it has traveled the length of the actuator or until the control spool is returned to its neutral position by the operator shifting the pilot control valve to its neutral position.
  • the pilot control valve is placed in the second operating position 56.
  • the control and operating hydraulic systems function as hereinbefore described with reference to lowering the implement.
  • the fluid in the second chamber 124 communicated via passageways 139, 126 and 128, unseats the ball 130 in the cavity 127 in the first end face 121 of the piston 120, thereby permitting transfer of fluid from the second chamber to the first chamber.
  • the spool continues to move in this manner until the annular recess 125 extending circumferentially about the piston opens with the drain port 161.
  • pilot pressure When pilot pressure is removed from the first chamber 123, the force of the springs 97, 102 return the control spool and piston to the neutral position. Pilot fluid in the first chamber 123 is vented to the reservoir 40 in response to movement of the piston 120 via passageway 160 and conduit 49.
  • the second chamber 124 is recharged with fluid from the reservoir via the make-up valve 163, conduit 165, and passageway 164 in response to a lower pressure caused therein by cavitation of the second chamber.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fluid-Pressure Circuits (AREA)

Abstract

Les vehicules de terrassement utilisent des systemes hydrauliques (12) pour commander le soulevement et l'abaissement des organes de fonctionnement. Les systemes hydrauliques (12) de ce type comprennent normalement une vanne de commande (34) pourvue d'un tiroir (64) qui peut se deplacer sous l'action d'une force resultant de l'application selective d'une pression pilote. L'utilisation des systemes hydrauliques (12) en vue d'assurer des fonctions supplementaires par deplacement du tiroir (64) vers des positions necessitant une course additionnelle du tiroir (64) souleve des difficultes. Cette course additionnelle du tiroir (64) requiert un accroissement considerable de la force d'actionnement, ce qui se traduit par une reduction notable de la gamme de pressions de pilotage disponible pour moduler le soulevement et l'abaissement. Afin d'eliminer ce probleme, on prevoit un systeme de commandes (14) pour une vanne pilotee (34) qui comprend un appareil (50) permettant de deplacer le tiroir (64) de la vanne sur une course additionnelle en changeant la grandeur de la force de deplacement sans modifier la grandeur de la pression de pilotage qui est normalement reservee pour moduler le soulevement et l'abaissement.
PCT/US1980/001339 1980-10-09 1980-10-09 Systeme de commande pour une vanne pilote WO1982001402A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/US1980/001339 WO1982001402A1 (fr) 1980-10-09 1980-10-09 Systeme de commande pour une vanne pilote
BE0/206069A BE890501A (fr) 1980-10-09 1981-09-25 Systeme de commande pour une vanne actionnee par un pilote

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
PCT/US1980/001339 WO1982001402A1 (fr) 1980-10-09 1980-10-09 Systeme de commande pour une vanne pilote
WOUS80/01339801009 1980-10-09

Publications (1)

Publication Number Publication Date
WO1982001402A1 true WO1982001402A1 (fr) 1982-04-29

Family

ID=22154590

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1980/001339 WO1982001402A1 (fr) 1980-10-09 1980-10-09 Systeme de commande pour une vanne pilote

Country Status (2)

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BE (1) BE890501A (fr)
WO (1) WO1982001402A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3160174A (en) * 1961-03-28 1964-12-08 Parker Hannifin Corp Remote power shift circuits for spool valves and the like
US3621881A (en) * 1970-08-03 1971-11-23 Acf Ind Inc High-low pressure pilot valve mechanism
US3863672A (en) * 1973-09-06 1975-02-04 B W B Controls Inc Dual action pilot
US4160463A (en) * 1977-10-13 1979-07-10 Baker Cac, Inc. Flow line monitor pilot valve assembly

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3160174A (en) * 1961-03-28 1964-12-08 Parker Hannifin Corp Remote power shift circuits for spool valves and the like
US3621881A (en) * 1970-08-03 1971-11-23 Acf Ind Inc High-low pressure pilot valve mechanism
US3863672A (en) * 1973-09-06 1975-02-04 B W B Controls Inc Dual action pilot
US4160463A (en) * 1977-10-13 1979-07-10 Baker Cac, Inc. Flow line monitor pilot valve assembly

Also Published As

Publication number Publication date
BE890501A (fr) 1982-01-18

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