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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T137/00—Fluid handling
  • Y10T137/8593—Systems
  • Y10T137/86493—Multi-way valve unit
  • Y10T137/86574—Supply and exhaust
  • Y10T137/86582—Pilot-actuated
  • Y10T137/86606—Common to plural valve motor chambers
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T137/00—Fluid handling
  • Y10T137/8593—Systems
  • Y10T137/86493—Multi-way valve unit
  • Y10T137/86574—Supply and exhaust
  • Y10T137/86582—Pilot-actuated
  • Y10T137/86614—Electric

Definitions

• the invention relates to a pilot operated servo valve with four main power connections. Pilot operated electrohydraulic servo valves in two or more stages
• 4-way valves to control position, speed and force in cylinders for linear movements, or position, speed and torque in hydraulic motors for rotary movements.
• 4-way servo valves are in the known design as
• Plate construction valves executed, that is, they have a prismatic valve housing for assembly on a connection surface of a hydraulic block.
• the four main flow connections of the valve lie in a planar connection surface of the valve housing and their openings in the guide bore of a main control piston are symmetrical.
• Control chambers are arranged in end caps that are flanged to the valve housing on both sides. These control chambers are connected to a pilot servo valve via control holes!
• the symmetrical main control piston is hydraulically actuated by pressurizing its two end faces in the front control chambers.
• the known pilot operated 4-way servo valves all have a spring-centered rest position. In most cases, centering of the main control piston takes place via two opposite return springs, which are arranged in the front control chambers and act against each other. However, it is also known to achieve centering by means of a single spring. This single spring is then clamped in an end spring chamber between two spring plates. A pull rod of the main control piston is axially displaceable through the two spring plates. An axial end stop is assigned to each spring plate on this tie rod. In the rest position of the valve, the spring plates are pressed by the spring against their end stops on the pull rod. In this position, the two spring plates are also in the housing stop in the spring chamber.
• the main spool is accordingly fixed by the spring in its so-called center position. If the main control piston is moved from the center position in the direction of the spring chamber, the spring is compressed in the spring chamber by the first spring plate opposite the end face of the main control piston and exerts a spring force on the main control piston. However, if the main control piston is moved in the opposite direction, the spring is compressed by the pulling force exerted on the second spring plate by the pull rod, and exerts a spring force on the main control piston in the other direction.
• the known pilot-operated 4-way servo valves with valve housing for mounting on a connection surface of a hydraulic block are very space-consuming and require complicated bores in the hydraulic block for the four main flow connections.
• the invention is therefore based on the object of providing a pilot-controlled servo valve which can be integrated into a hydraulic block in a space-saving manner and which has a clearly defined center position without having to forego good dynamic behavior of the servo valve.
• the pilot operated 4-way servo valve has a control sleeve which can be mounted directly in a stepped bore of a hydraulic block.
• This control sleeve includes openings for a first, second and third lateral work connection in the hydraulic block.
• the confluence with the control sleeve for the fourth main power connection is arranged at the front end of the control sleeve such that this fourth main power connection opens axially into the control sleeve.
• the hydraulic block, in which the control sleeve is inserted then has three lateral block bores for the first, second and third main flow connection. Regarding the arrangement of the block bore for the fourth main power connection, however, there is the greatest possible freedom.
• This block bore for the fourth main flow connection can, for example, be carried out directly in the axial extension of the stepped bore for the control sleeve, which has not hitherto been possible in conventional pilot-operated servo valves with more than two main connections. Bridge formation in the hydraulic block between individual Main power connections are also no longer required.
• the servo valve according to the invention thus achieves a much more compact design of the control blocks than is the case with conventional servo valves. Even in more complex hydraulic controls, the servo valve according to the invention can be integrated into a hydraulic block in a space-saving manner together with various additional valves, for example 2-way built-in valves. A direct installation in the cylinder cover of larger cylinders is also possible.
• the main control piston of the valve according to the invention is arranged axially displaceably in the control sleeve.
• One of the two piston faces of the main control piston is axially opposite the fourth axial working connection.
• the second piston end face of the main control piston forms in a spring chamber in the extension of the control sleeve a pressure compensation surface of the piston which hydrostatically counteracts the first piston end face.
• the spring chamber is hydraulically connected to the fourth main flow connection by a pressure relief channel in the main control piston. This pressure relief duct also connects an auxiliary connection chamber to the fourth main power connection.
• a return spring is clamped in the spring chamber and engages with the main control piston via spring plates in such a way that it opposes the hydraulic actuating force in the control chambers with a spring force proportional to the piston stroke in both stroke directions of the piston and defines a pressure-centered center position for the main control piston in unpressurized control chambers.
• a pilot valve with regulator is hydraulically connected to the two control chambers.
• a position sensor of the main control piston delivers a feedback signal for the controller of the pilot valve.
• the asymmetrical hydrostatic load on the main control piston is compensated for by appropriate dimensioning of the pressure compensation surface of the main control piston.
• This hydrostatic compensation reduces the actuation forces required for the main control piston, which means that the actuation areas in the control chambers can be made smaller. This results in smaller control oil volumes, which means that shorter actuating times can be achieved with the same pilot valve.
• This hydrostatic compensation for the The main control piston also enables the problem-free use of a one-sided return spring for spring centering of the main control piston in both stroke directions. This ensures the same deflection for each stroke direction with the same signal. Furthermore, the central position of the main control piston is reliably determined by the return spring which acts directly mechanically on the main control piston.
• the connections of the servo valve are preferably assigned as follows: the first main flow connection is hydraulically connected to a first displacement chamber of a consumer and thus forms a first working connection (A), the second main flow connection is hydraulically connected to a tank and thus forms a tank connection (T) , The third main flow connection is hydraulically connected to a second displacement chamber of a consumer and thus forms a second working connection (B), the fourth main flow connection is hydraulically connected to a pump and thus forms a pump connection (P).
• the pump connection (P) can axially into the
• hydraulic is generally under pump
• Displacement chambers for example a rotary or linear drive
• the control edges assume the following position: the first axial hydraulic connection is closed by the first control edge, the second axial hydraulic connection is released, the third axial hydraulic connection is released, the fourth axial hydraulic connection is closed by the fourth control edge.
• the working ports (A) and (B) are thus connected to the tank port (T) in the spring-centered central position of the main control piston.
• the two displacement chambers of a connected consumer are both pressure-relieved when the main control piston is centered in the spring.
• the four control edges of the main control piston preferably have a zero overlap. This results, for example, in an excellent positioning accuracy when the valve is used in a position control loop of a hydraulic cylinder, and an excellent dynamic behavior when the valve is used for pressure control.
• other arrangements of the control edges are also possible. For example, in the spring-centered central position of the main control piston, all connections could be closed by the control edges.
• the spring centering is preferably designed as follows.
• the main control piston has an axial extension shaft in the spring chamber.
• a first and second spring plate are axially displaceable on this extension shaft.
• the return spring presses the first spring plate against a stop surface on the main control piston and the second spring plate against a stop surface at the free end of the extension piston.
• the spring chamber is then dimensioned such that, in this rest position, both spring plates bear axially in the spring chamber.
• FIG. 1 shows a longitudinal section through an inventive servo valve
• FIG. 2 shows an enlarged section of FIG. 1.
• the servo valve according to the invention is designated as such with the reference number 10.
• a control sleeve 12 is inserted into a stepped bore 14 of a hydraulic block 16 (only indicated).
• the control sleeve 12 forms an axial guide bore into which a main control piston 18 is axially slidably fitted.
• the servo valve 10 shown in the figures is a 4-way servo valve and has a pump connection (P), a tank connection (T), and a first working connection (A) and a second working connection (B).
• the pump connection (P) is in hydraulic connection with a pressure line (not shown).
• the tank connection (T) is in hydraulic connection with an unpressurized line (not shown).
• the working connections (A) and (B) are in hydraulic connection with a first or second displacement chamber of a hydraulic linear or rotary drive (not shown).
• Three block bores 22, 20, 24 in the hydraulic block 16 for the tank connection (T) 22, the first working connection (A) 20 and the second working connection (B) 24 are arranged transversely to the stepped bore 14 and open laterally into the stepped bore 14.
• the control sleeve 12 forms an annular opening 22 ', 20', 24 'in the area of the corresponding block bores 22, 20, 24.
• Each of these orifices 22 ', 20', 24 ' has a plurality of transverse bores 25 through the wall of the control sleeve 12, which each produce a hydraulic connection with the guide bore of the main control piston 18.
• a fourth block bore 26 for the pump connection (P) is arranged in a coaxial extension of the stepped bore 14.
• the control sleeve 12 has an end opening 26 '.
• a first axial hydraulic connection 28 connects the end opening 26 'for the pump connection (P) with the side opening 20' for the working connection (A); a second axial hydraulic connection 30 the mouth 22 'for the tank connection
• the axial distance is due to the arrangement of the annular openings 22', 20 ', 24' between the second and third (30 and 32) axial hydraulic connection larger than the axial distance between the first and second (28 and 30), respectively the third and fourth 32 and 34) axial hydraulic connection.
• the main control piston 18 has a first coaxial piston collar 38 which is assigned to the working connection (A) and is axially displaceable in the first and second axial hydraulic connections 28 and 30. It also has a second coaxial piston collar 40, which is assigned to the working connection (B) and is axially displaceable in the third and fourth axial hydraulic connections 32 and 34.
• the first piston collar 38 forms a first control edge 28 ′ assigned to the first hydraulic connection 28 and a second control edge 30 ′ assigned to the second hydraulic connection 30. Both control edges 28 ', 30' have a zero overlap.
• the second piston collar 40 forms a third control edge 32 ′ assigned to the third hydraulic connection 32 and a fourth control edge 34 ′ assigned to the fourth hydraulic connection 34.
• Both control edges 32 ', 34' also have a zero overlap.
• the auxiliary connection chamber 36 is annular in the control sleeve around the main control piston 18. It is axially sealed on one side by the piston collar 40 and on the other side by a piston collar 42.
• the auxiliary connection chamber 36 is connected to the pump connection (P) via an axial piston bore 44 and a piston transverse bore 46 through the main control piston 18.
• the main control piston can accordingly connect the first working connection (A) via its coaxial piston collar 38 and the second working connection (B) via its coaxial piston collar 40 with the pump connection (P) or the tank connection (T), the respective flow of the hydraulic fluid via the four control edges 28 ', 30', 32 ', 34' is regulated.
• the main control piston 18 is loaded hydrostatically asymmetrically via its pressurized piston end face 48.
• a hydrostatic pressure compensation of the main control piston takes place by continuing the coaxial piston bore 44 to the second end of the main control piston 18, where it opens into a pressure compensation or spring chamber 52 via a piston cross bore 50.
• the spring chamber 52 is arranged in an axial extension of the control sleeve 12 in a valve cover 54.
• This valve cover 54 is fastened on the hydraulic block 16 and fixes the control sleeve 12 in the stepped bore 14.
• the second end of the main control piston 18, axially sealed by a sealing insert 56, is inserted into the spring chamber 52 and forms a pressure compensation extension 58 therein.
• the pressure compensation chamber 52 the latter has a pressure compensation surface 60 which hydrostatically counteracts the first piston end face 48.
• the pressure compensation surface 60 is equal to the piston end surface 48, so that there is complete hydrostatic pressure compensation of the pump pressure.
• the main control piston 18 is actuated via a machined coaxial actuating piston collar 62, by correspondingly pressurizing its annular first or second actuating surface 64, 66.
• a first annular control chamber 68 is located in the control sleeve between the piston collar 42 and the actuating surface 64 and between the sealing insert 56 and the Actuating surface 66 formed a second annular control chamber 68.
• the first control chamber 68 is connected via a pilot control connection 72 in the valve cover 54 to the working connection (A ') and the second control chamber 70 is connected via a pilot control connection 74 in the valve cover 54 to the working connection (B') of a flanged 4-way pilot control - Servo valve 76 connected.
• the actuating surfaces 64, 66 are designed so large that the flow forces arising when the control edges 28 ', 32' or 30 ', 34' flow over them are surely overcome. As a result, the control oil volumes are very small and very short positioning times can be achieved.
• a return spring 78 is axially clamped between a first and second spring plate 80 and 82.
• An extension shaft 84 is rigidly connected to the second end of the main control piston 18.
• the spring plates 80 and 82 are guided axially displaceably on this shaft 84.
• the shaft 84 has an axial stop surface 86 for the second spring plate 82 at its free end.
• the second piston end face 60 forms an axial stop surface for the first spring plate 80.
• the return spring 78 presses the first spring plate 80 against the stop surface 60 and the second spring plate 82 against the stop surface 86.
• the first spring plate 80 is also in the housing stop on the sealing insert 56 and the second spring plate 82 is in the housing stop on an axially opposite stop surface 88 of the valve cover 54. Both spring plates 80 and 82 are therefore in the housing stop, and the main control piston 18 is located between the extension shaft 84 the two spring plates 80 and 82 clamped, which are spring-loaded in opposite directions by the return spring 78. In other words, the main control piston 18 is in a spring-centered rest position, which is also referred to as the center position.
• the main control piston 18 by pressurizing the first
• Control chamber 68 moves from its central position in the direction of the spring chamber 52, the return spring 78 is compressed in the spring chamber 52 by the first spring plate 80 abutting the end face 60 of the main control piston 18. As a result, it exerts a spring force on the main control piston 18 which opposes this movement and whose module is proportional to the stroke of the main control piston 18.
• the extension shaft 84 exerts a tensile force on the second spring plate, so that the return spring 78 is now compressed in the spring chamber 52 by the second spring plate 82.
• This spring force opposes the movement of the main control piston 18 and its module is proportional to the stroke of the main control piston 18.
• the use of a single return spring 78 which works as a compression spring for both stroke directions, ensures that the main control piston 18 is exactly the same in both directions is subjected to the same restoring force.
• the extension shaft 84 is screwed into the main control piston and is secured by a pin 90.
• the axial piston bore 44 is continued in the extension shaft 84 up to the transverse bore 46.
• Another transverse bore 92 is located directly above the end face 60 of the main control piston 18. This second transverse bore 92 has to ensure pressure equalization above and below the spring plate 80 for the purpose. In the second spring plate 82, this pressure compensation is achieved through holes 94 in the spring plate 82.
• the main control piston is integrated into a closed position control loop via a position sensor 96.
• a shaft 98 of the position sensor 96 is mechanically connected to the extension shaft 84 of the main control piston.
• the output signal of the position sensor 96 (which corresponds to the position of the main control piston 18) is compared in a control amplifier 100 with a target value (S), and the pilot control valve 76 is activated in relation to the determined target / actual value difference.
• the pilot control valve 76 then regulates the control oil pressure in the two control chambers 68 and 70 of the main stage and, against the action of the return spring 78, determines the piston stroke, so that a closed, electro-hydraulic control circuit is formed.
• the main control piston 18 is also shown in FIG. 1 in the spring-centered rest or center position.
• the control edges 28 ', 30', 32 ', 34' are arranged on the main control piston 18 such that in this central position:
• the first control edge 28 closes the first hydraulic connection 28 between the pump connection (P) and the working connection (A);
• the second control edge 30 releases the second hydraulic connection 30 between the tank connection (T) and the working connection (A);
• the third control edge 32 releases the third hydraulic connection 30 between the tank connection (T) and the working connection (B);
• the fourth control edge 34 closes the fourth hydraulic connection between the working connection (B) and auxiliary connection chamber 36, and thereby prevents the hydraulic connection via the axial piston bore 44 between the working connection (B) and the pump connection (P).

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

Applications Claiming Priority (3)

Publications (2)

Family

ID=19731505

Family Applications (1)

Country Status (11)

Families Citing this family (21)

Family Cites Families (5)

• 1994
  • 1994-11-16 LU LU88558A patent/LU88558A1/de unknown
• 1995
  • 1995-11-13 JP JP51572996A patent/JP3638286B2/ja not_active Expired - Fee Related
  • 1995-11-13 AT AT95937068T patent/ATE224012T1/de not_active IP Right Cessation
  • 1995-11-13 RU RU97110059/06A patent/RU2153105C2/ru not_active IP Right Cessation
  • 1995-11-13 CN CN95196278A patent/CN1070584C/zh not_active Expired - Fee Related
  • 1995-11-13 AU AU39285/95A patent/AU3928595A/en not_active Abandoned
  • 1995-11-13 US US08/817,302 patent/US5896890A/en not_active Expired - Fee Related
  • 1995-11-13 EP EP95937068A patent/EP0828945B1/fr not_active Expired - Lifetime
  • 1995-11-13 CA CA002205441A patent/CA2205441C/fr not_active Expired - Fee Related
  • 1995-11-13 WO PCT/EP1995/004454 patent/WO1996015373A1/fr active IP Right Grant
  • 1995-11-13 DE DE59510375T patent/DE59510375D1/de not_active Expired - Lifetime

Non-Patent Citations (1)

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