US3857541A - Servovalve with oscillation filter - Google Patents

Servovalve with oscillation filter Download PDF

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US3857541A
US3857541A US00369789A US36978973A US3857541A US 3857541 A US3857541 A US 3857541A US 00369789 A US00369789 A US 00369789A US 36978973 A US36978973 A US 36978973A US 3857541 A US3857541 A US 3857541A
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spool
servovalve
chambers
drilling
chamber
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D Clark
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Moog Inc
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Moog Inc
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Priority to GB3506873A priority patent/GB1375517A/en
Priority to JP9479873A priority patent/JPS5610484B2/ja
Priority to DE19732343552 priority patent/DE2343552A1/de
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    • 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
    • F15B13/0438—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 of the nozzle-flapper type
    • 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
    • Y10T137/8659—Variable orifice-type modulator
    • Y10T137/86598—Opposed orifices; interposed modulator
    • 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

  • ABSTRACT [21 Appl. N0.: 369,789 The pressure variations in the spool end chambers ofa two-stage electrohydraulic servowalve having a second-stage sliding-spool type hydraulic amplifier. re-
  • the present invention relates to the field of electrohydraulic servovalves, and especially those which are prone to oscillate under certain operating conditions.
  • two-stage servovalves comprise a permanent magnet torque motor having a movable armature member; a first-stage hydraulic amplifier, be it of the nozzle-flapper type, the movable jet pipe type, or the deflector jet type, having a movable control member connected to the armature; and a second-stage, sliding-spool type hydraulic amplifier.
  • Such valves usually incorporate mechanical feedback in the form of a spring member that creates torque or force on the armature proportional to spool position.
  • such servovalves generally incorporate a bushing or sleeve member that ports hydraulic fluid to the second-stage spool.
  • the above known servovalves are sometimes used in systems where very high valve dynamic response is re quired, such as material test machines, motion simulators, vibration exciters, etc.
  • the servovalves for these systems have moderately high flow control, such as to gallons per minute (gpm) at 1000 pounds per square inch (psi) (38 to 58 litres per minute at 70 bars) and system supply pressures are often 4000 psi (280 bars) or higher.
  • gpm gallons per minute
  • psi pounds per square inch
  • system supply pressures are often 4000 psi (280 bars) or higher.
  • the use of high control flow with high supply pressure provokes servovalve instability tendencies, such as high amplitude resonance or even selfoscillation.
  • (5) may operate with signal input commands that are well beyond the normal bandwidth of the position servo to achieve high load excitation frequencies. Although the amplitude ratio at high frequencies may be much reduced from that at low frequencies it is still possible to get meaningful load response at higher frequencies by increasing the amplitude of the command signal.
  • Resonant frequency characteristics of a servovalve are peculiar to each specific valve design. Thus, for duplicates of a given valve design, the resonance may vary in amplitude from individual valve to valve, but the characteristic resonant frequency is the same. Different servovalve designs may produce different characteristic resonant frequencies.
  • Typical resonances of a servovalve having an armature supported on a flexure tube include, for example: 550 to 750 lI-Iertz (I-Iz) first-stage armature/flapper resonance on net stiffness of the flexure tube and magnetic circuit; 3.0 to 3.5 kiloI-Iertz (KI-I2) first-stage armature/flapper resonance on the mechanical stiffness of the flexure tube; still higher first-stage resonant frequencies as the armature/flapper vibrates in harmonic modes; 3.0 to 3.5 KHz resonance of the bushing and spool'masses on the retained stiffness of a bushing locating pin and net compliance of fluid in the spool end chambers; and beat frequencies as the spool and bushing move in and out of phase.
  • I-Iz lI-Iertz
  • KI-I2 kiloI-Iertz
  • the present invention provides a solution to the oscillatory problem of an electrohydraulic servovalve, especially one operating in the elevated pressure range of 3000 to 4000 psi and with low viscosity hydraulic fluid where heretofore the problem was particularly acute, different from and more effective than the aforementioned prior art attempts to solve the problem.
  • acoustic frequency type passive hydraulic resonant filters are provided in association with the spool end chambers.
  • the filter for each spool end chamber is a-wave tube having a characteristic length and having a diameter sufficient to give effective filtering.
  • the length of the wave tube equals one-quarter the wave length of the servovalves characteristic resonant frequency to be attenuated.
  • the addition of the filter does not affectthe normal servovalve response in its lower frequency range.
  • Such a resonance filter in the-form of a wave tube is simply and cheaply added, achieved by providing connected drillings in the valve body without complex machining.
  • the diameter of the drilled composite wave tube is not critical. Its location and length is compatible with the basic valve envelope.
  • the filter attenuates the oscillation tendency right at the second-stage and so isolates valve oscillations from the driven load.
  • the main object of the present invention is to provide an effective solution to the problem of servovalve oscillation, especially when operating at a high pressure level and with low viscosity hydraulic fluid.
  • FIG. 1 is a substantially central longitudinal sectional view through an electrohydraulic servovalve constructed in accordance with the principles of the present invention and illustrating a preferred embodiment thereof, this view being taken generally on line ll of FIG. 2.
  • FIG. 2 is a vertical transverse sectional view thereof taken on line 2-2 of FIG. 1.
  • FIG. 3 is a horizontal sectional view thereof taken on line 33 of FIG. 1, and illustrates the longitudinal extents of the elongated tubular cavities of wave tubes formed by drillings in the valve body components which provide the acoustic filter means constituting the improvement of the present invention.
  • FIG. 4 is a vertical transverse sectional view of the valve body, taken on line 44 of FIG. 1 and showing in elevation the inside face of the left end cap forming one component of the valve body.
  • FIG. 5 is another vertical transverse sectional view of the valve body, taken on line 5-5 of FIG. 1, and showing in elevation the inside face of the right end cap forming another component of the valve body.
  • FIG. 6 is a vertical longitudinal sectional view of the left end cap, taken generally on line 6-6 of FIG. 4.
  • FIG. 7 is a vertical longitudinal sectional view of the right end cap, taken generally on line 7-7 of FIG. 5.
  • FIG. 8 is a horizontal sectional view of the valve body and other elements housed therein, taken generally on line 88 of FIG. 2.
  • FIG. 9 is a composite of separate graphs depicting the flow and pressure characteristics of fluid in a wave tube associated with a spool end chamber, also schematically depicted.
  • the electrohydraulic servovalve illustrated in the drawings is a two-stage servovalve shown as comprising a permanent magnet torque motor 10 including a movable armature member 11, a first-stage hydraulic amplifier 12 preferably of the nozzle-flapper type including a movable control member 13 connected to the armature, and a second-stage, sliding spool type hydraulic amplifier 14 including a valve body 15 housing a bushing assembly 16 in which a valve spool 17 is slidably arranged.
  • Valve body 15 is shown as comprising three components including an intermediate body block 18, a left end cap 19, and a right end cap 20.
  • Block 18 has a horizontal bore 21 therethrough extending from its vertical left end face 22 to its vertical right end face 23.
  • Left end cap 19 has a flat annular inner end face 24, surrounding an inwardly axially projecting cylindrical tu-' bular neck 25, in turn surrounding an annular recess 26, leaving a central axially extending post 28,'the end face 29 of which is slightly outside the plane of annular face 24 and serves as a stop for the left end of valve spool 17.
  • Left end cap 19 is secured to body block 18 by a pair of screws 30.
  • Neck 25 projects into the left end of body bore 21 and is sealed thereto by O-ring 27.
  • right end cap 20 has a flat annular inner face 31, surrounding an inwardly axially projecting cylindrical tubular neck 32, in turn surrounding an annular recess 33, leaving a central axially extending post 34, the end face 35 of which is slightly outside the plane of annular face 31 and serves as a stop for the right end of valve spool 18.
  • Right end cap 20 is secured to body block 18 by a pair of screws 36.
  • Neck 32 projects into the right end of body bore 21 and is sealed thereto by O-ring 37.
  • Bushing assembly 16 is arranged in body bore 21. While this assembly may be constructed in any suitable form the same preferably comprises as shown a stack of brazed-together tubular parts including a left end part 38, a left intermediate part 39, a center part 40, a
  • Center bushing part 40 is shown as provided with a chordal slot 43 into which the inner end 44 of a bushing pin 45 projects, this pin being housed within body block 18 and extending generally radially with respect to the bushing assembly.
  • This pin 45 has a sealed connection with body block 18 provided by O-ring 46 and is retained in position by a surrounding sleeve fitting 48 having a threaded connection with the body block. Pin 45 serves to prevent axial movement of bushing assembly 16 relative to body block 18.
  • Bushing assembly 16 is shown as formed so that jointly with the surrounding wall of body bore 21, there are provided a left annular pressure chamber 50, a left annular outer control chamber 51, a central annular return chamber 52, a right annular outer control chamber 53, and a right annular pressure chamber 54.
  • Left end radial metering passages 55 connect chamber 50 to the cylindrical bore 56 extending horizontally through the bushing assembly.
  • Left and right center radial metering passages 57 and 58 respectively, arranged at the axial ends of center bushing port 40 connect chamber 52 to bore 56.
  • Right end radial metering passages 59 connect chamber 54 to bore 56.
  • Left radial control passages 60 connect chamber 51 to bore 56, and right radial control passages 61 connect chamber 53 to bore 56.
  • Intermediate bushing parts 39 and 41 are shown sealed to the wall of body bore 21 by a pair of O-rings 62 on opposite sides of left control chamber 51 and a pair of O-rings 63 on opposite sides of right control chamber 53.
  • Left end bushing part 38 is of smaller external diameter than adjacent bushing part 39 and projects into the bore of left end cap neck and is sealed thereto by O-ring 64.
  • right end bushing part 42 is of smaller external diameter than adjacent bushing part 41 and projects into the bore of right end cap neck 32 and is sealed thereto by O-ring 65.
  • Valve spool 17 is shown as including a left lobe 67, a center lobe 68 and a right lobe 69. These lobes are cylindrical in form and slidably engage the wall of bushing bore 56.
  • Left lobe 67 is connected to center lobe 68 by an integral concentric left stem 70 and this center lobe is connected toright lobe 69 by an integral concentric right stem 71.
  • the opposing end faces of lobes 67 and 68 are radial and spaced apart in axial distance corresponding to that between the adjacent edges of metering passages 55 and 57, and with the periphery of stem 71) and the surrounding portion of bore 56 jointly provide a left annular inner control chamber 72.
  • lobes 68 and 69 are ra' dial and spaced apart an axial distance corresponding to that between the adjacent edges of metering passages 58 and 59, and with the periphery of stem 71 and the surrounding portion of bore 56 jointly provide a right annular inner control chamber 73.
  • passages 60 communicate inner and outer left control chambers 72 and 51, respectively, and passages 61 communicate inner and outer right control chambers 73 and 53, respectively.
  • Chamber 51 communicates with a first control port C in the base of body block 20.
  • Chamber 53 communicates with a second control port C also in the base of the body block.
  • These control ports are adapted to be connected with a load such as a piston and cylinder actuator (not shown).
  • the base of body block 18 is also shown as provided with a pressure port P and a return port R.
  • Port R is shown as communicating with central chamber 52.
  • Port P is shown as communicating with a horizontal hole 74 extending through body block 18 alongside bushing bore 21 at a lower level.
  • the end of hole 74 adjacent end cap 19 is externally sealingly plugged by a sleeve plug member 75 which internally supports a fixed orifice member 7.
  • the other end of hole 74 adjacent end cap 20 is externally sealingly plugged by a sleeve member 78 which internally supports a fixed orifice member 79.
  • Extending between sleeve plug members 75 and 78 is a tubular filter screen 80 having a transverse dimension less that that of hole 74 to provide an annular space 81 around this screen.
  • Pressurized hydraulic fluid applied to port P fills hole 74 including space 81 and occupies pressure chambers 50 and 54 which communicate with this space as shown in FIG. 8.
  • left spool lobe 67 blocks communication between left pressure chamber 50 and left inner control chamber 72
  • right spool lobe 69 blocks communication between right pressure chamber 54 and right inner control chamber 73
  • center spool lobe 68 blocks communication between return chamber 52 with both of these control chambers 72 and 73.
  • Pressurized fluid can also How through filter screen 80 into the interior thereof and thence outwardly through fixed orifices 76 and 79. Downstream of orifice 76the bore 82 of sleeve plug 75 communicates with the inner open end of a horizontal dead-ended passage 83 provided in end cap 19. This passage 83 has a branch passage 84 which communicates with cap recess 26. An O-ring 85 seals the connection between bore 82 and passage 83.
  • the left cap recess 26 and the outer left end faces of spool bushing assembly 16 and valve spool 17 define a left spool end chamber 91
  • the right cap recess 33 and the outer right end faces of this bushing assembly and valve :spool define a right spool end chamber 92.
  • These spool end chambers 91 and 92 are operatively associated with the firststage hydraulic amplifier 12 in the following manner.
  • This amplifier 12 is shown as including a nozzle block 93 having a flat bottom surface 94 engaging the flat top surface 95 of valve body block 18. Screws 96 secure these blocks together.
  • Nozzle block 93 has a vertical central opening 98 extending therethrough and projecting into this opening from diametrically opposite positions are the tips of left and right nozzles 99 and 100, respectively. These nozzles are suitably supported horizontally on nozzle block 93 in fixed and spaced relation to each other.
  • the lower end portion of control member 13, acting as a flapper, extends in the space between these nozzles and jointly with their tips provide a pair of differentially variable orifices.
  • left nozzle 99 communicates with left spool end chamber 91, while the bore or passage of right nozzle 100 communicates with right spool end chamber 92.
  • left nozzle 99 communicates with a chamber 101 in nozzle block 93 from which a passage 102 extends to surface 94.
  • passage 102 communicates with a passage 103 in body block 18 which extends between surface 95 and end face 22.
  • the end of passage 103 communicates with one end ofa passage 104 in left end cap 19 which leads to cap recess 26 and hence left spool end chamber 91.
  • An O-ring 105 seals the interface joint between surfaces 94 and 95 around the connected passages 102 and 103, and an O-ring 106 seals the interface joint between surfaces 22 and 24 around the connected passages 103 and 104.
  • right nozzle 100 communicates with a chamber 108 in nozzle block 93 from which a passage 109 extends to surface 94.
  • passage 109 communicates with a passage 110 in body block 18 which extends between surface 95 and end face 23.
  • the end of passage 110 communicates with one end of a passage 111 in right end cap 20 which leads to cap recess 33 and hence right spool end chamber 92.
  • An O-ring 112 seals the interface joint between surfaces 94 and 95 around the connected passages 109 and 110, and an O-ring 113 seals the interface joint between surfaces 23 and 31 around the connected passages 110 and 111.
  • Opening 98 in nozzle block 93 is shown as communicating with the upper end of a tubular union member 114 the upper end of which is sealingly connected to this nozzle block by O-ring 115 and to body block 18 by O-ring 116.
  • the lower end of member 114 extends into a radial hole in the center part 40 of bushing assembly 16 and is sealingly connected thereto by O-ring 118.
  • This member 114 has a drain orifice 119 (FIG. 2) on its side wall which communicates the sum chamber 120 formed by the connected opening 98 and interior of member 114 with annular return chamber 52. Orifice ll9-reduces the effect of any pressure surges that may occur in the return side of the hydraulic system, including chamber 52, upon sump chamber 120 and the fluid flow passages or bores of nozzles 99 and 100 discharging into such sump chamber.
  • Torque motor is a polarized electrical force motor of well-known construction. As illustrated, it includes upper and lower pole pieces 121 and 122, respectively, between which permanent magnets 123 extend and house a pair of coils 124 which surround opposite arm portions of armature 11. The tips of this armature extend intoair gaps formed between the opposing ends of flange portions of the pole pieces 121 and 122.
  • the assembly of pole pieces, permanent magnets and coils is mounted on the top of nozzle block 93 and is securedthereto by a plurality of screws 125.
  • Horizontal armature 11 is shown sealingly mounted intermediate its ends on the upper end of an upright flexure tube member 126.
  • This member includes a thin walled tubular section capable of flexing or deflecting which surrounds flapper 13 in slightly spaced relation, and also includes an enlarged attaching base sealingly connected to the top of nozzle block 93 by O-ring 128 and fasteners 129.
  • the annular clearance surrounding that portion of flapper 13 arranged within flexure tube member 126 communicates with the upper end of opening 98 in nozzle block 93 and forms part of sump chamber 120.
  • flexure tube member 126 supports armature 11 so as to allow pivotal movement thereof while isolating the elements of electrical torque motor 10 arranged externally of the flexure tube from the elements communicatively associated with and wetted by hydraulic fluid on the interior of this tube.
  • a vertically disposed feedback spring member 131 is cantilever-mountedat its upper end on the lower end of flapper 13 and its lower end has a substantially frictionless connection with valve spool 17 by virtue of a ball enlargement 132 having rolling contact with the walls of an annular groove 133 provided in center lobe 68 of this valve spool.
  • An electrical connector 134 operatively associated with coils 124 in a well-known manner is provided for electrical signal command input to the servovalve.
  • a motor cap 135 covers torque motor 10 and is sealingly mounted on valve body block 18 by an O-ring 136 and screws 138.
  • the servovalve as a unit may be mounted on any suitable support (not shown) by fasteners (not shown) extending through vertical mounting holes 139 provided in valve body block 18 adjacent its four corners as shown in FIG. 3.
  • electrohydraulic servovalve described hereinabove is well known to those skilled in the art. Suffice it to say here than an electrical command input signal to the servovalve will produce a proportionate hydraulic response incontrol ports C and C which may be utilized to drive a load. Such input signal energizes coils 124 to induce electromagnetically pivotal movement of armature lland hence flapper 13. Movement of this flapper relative to nozzles 99 and produces differentially variable orifices through which these nozzles discharge fluid. This adjusts the pressures in spool end chambers 91 and 92 to apply a differential pressure against the ends of valve spool 17 and cause the same to displace axially.
  • valve spool 17 Displacement of valve spool 17 will establish communication between one of the control ports C and C with either pressure port P or return port R. For a given input signal, the valve spool will displace until feedback spring member 131 bends to create a torque on armature 11 substantially counterbalancing the electrically induced torque thereon. Hence spool displacement will be proportional to signal input.
  • acoustic filter means is provided for each of the spool end chambers 91 and 92 to provide a wave tube having an open end communicating with its companion spool end chamber and having a length to provide a characteristic anti-resonant frequency.
  • the wave tube Prefera' bly the end of the wave tube remote from the spool end chamber with which it is associated is closed.
  • the wave tube preferably has a length substantially equal to one-quarter the wave length of the characteristic resonant frequency to be attenuated.
  • the volume of the wave tube should be at least one-half of the volume of the spool end chamber with which it is associated. Preferably, such volumes are substantially equal to each other.
  • the wave tube designated 91 is associated with left spool end chamber 91 and the wave tube designated 92' is associated with right spool end chamber 92.
  • Such wave tubes 91 and 92 are preferably achieved by drillings provided in the body of the servovalve.
  • intermediate body block 18 is shown as provided with a pair of parallel horizontally spaced holes 140 and 141 extending horizontally from left end 22 to right end face 23. These holes are arranged at a level above the bushing bore 21 on opposite sides of the centrally disposed horizontal sections of passages 103 and 110 which are aligned.
  • Left end cap 19 has an upwardly and outwardly inclined drilled recess 142 which at its lower end communicates with annular cap recess 26, as shown in FIG. 6. The upper end of this recess intercepts the inner end of a horizontal recess 143 drilled from cap end face 24 and communicating with the left end of hole 140 in block end face 22.
  • Right end cap 20 has a horizontal dead-end recess 144 drilled from cap end face 31 and which is aligned with and communicates with the right end of hole 140 in block end face 23.
  • An O-ring 145 seals the interface joint between the ends of recess 143 and hole 140, and an O-ring'146 seals the interface joint between the ends of recess 144 and hole 140.
  • right end cap 20 has an upwardly and outwardly inclined drilled recess 148 which at its lower end communicates with annular cap recess 33, as shown in FIG. 7.
  • the upper end of this recess intercepts the inner end of a horizontal recess 149 drilled from cap end face 31 and communicating with the right end of hole 141 in block end face 23.
  • Left end cap 19 has a horizontal dead-end recess 150 drilled from cap end face 24 and which is aligned with and communicates with the left end of hole 141 in block end face 22.
  • An O-ring 151 seals the interface joint between the ends of recess 149 and hole 141, and an O-ring 152 seals the interface joint be tween the ends of recess 150 and hole 141.
  • the end-connected drillings 143, 140 and 144 provide wave tube 91 for left spool end chamber 91 of the requisite length and diameter, open at one end and communicating with this chamber via inclined passage 142 and closed at its other end remote from this chamber.
  • the end-connected drillings 149, 141 and 150 provide wave tube 92 for right spool end chamber 92 of the requisite length and-diameter, open at one end and communicating with this chamber via inclined passage 148 and closed at its other end remote from this chamber.
  • the same type servovalve, when provided with the wave tubes 91 and 92' of the present invention filtered out the 3.3 KI-lz pressure variations in the spool end chambers.
  • the required tube length (one-fourth wavelength) is:
  • the 1,050 m/sec velocity of propagation of sound in oil is based on a bulk modulus of 10,000 kg/cm and a fluid density of 0.88.
  • each wave tube 91', 92 was about 8.0 cm
  • tube 91 was composed of the sum of 6.5 cm for the length of hole 140, plus'0.5 cm for the length of blind end recess 144 and 1.0 cm for the length of recess 143
  • tube 92' was composed of the sum of 6.5 cm for the length of hole 141, plus 0.5 cm for the length of blind end recess and 1.0 cm for the length of recess 149.
  • the diameter of each of the various passages 140, 141, 143, 144, 149, 150 was 3.2 mm.
  • acoustic filter means in the form of these wave tubes 91' and 92 provides antiresonance of a characteristic frequency by creating a pressure node at each spool end chamber.
  • FIG. 9 The effects of flow and pressure in a wave tube is graphically illustrated in FIG. 9.
  • the spool end chamber connected to the open end of a closed end wave tube having a length equalto one-quarter the wavelength, )1 of the characteristic resonant frequency of the servovalve to be attenuated.
  • Intermediate is a graph representing the envelope of the resonant pres sure peaks, P(x), as a function of distance, x along the length of the tube according to the following equation;
  • Q is at the left or open end of the wave tube.
  • acoustic wave tube filter will produce similar anti-resonance for a characteristic frequency.
  • the foregoing embodiment of the present invention utilizes a closedend wave tube having a length equal to one-quarter wavelength (A A) of the characteristic resonant frequency. It is known that other closed-end wave tubes having lengths corresponding to odd integer multiples of the one-quarter wavelength will produce essentiallyidentical antiresonance for the same characteristic resonant frequency. Thus, closed-end wave tubes of lengths A A, A, /4 )t, etc. could equally well be utilized. Such variations may be better suited to the size and detail design of a specific servovalve.
  • acoustic wave tube that will produce similar anti-resonance for a characteristic frequency is an openended wave tube having a length equal to one-half wavelength )t).
  • open-ended wave tubes having integer multiples of one-half wavelength will produce essentially indentical anti-resonance for the same characteristic resonant frequency.
  • open-ended wave tubes of lengths A, )t, 3/2 )t, etc. could equally well be utilized.
  • an electrohydraulic servovalve including a body having a compartment in which a valve spool is slidably arranged leaving chambers at opposite ends of said spool, said servovalve being prone to oscillate at one or more characteristic resonant frequencies resulting in pressure variations in such spool end chambers, the improvement thereof which comprises acoustic filter means for each of said spool end chambers and severally arranged to provide a wave tube having an open end communicating with its corresponding one of said spool end chambers and having a length to provide anti-resonance for one characteristic frequency.
  • An electrohydraulic servovalve wherein said body comprises a block and first and second end caps at opposite ends of said block, said first and second end caps severally in part defining first and second spool end chambers, one of said wave tubes includes a first intermediate drilling extending through said block, a first connecting drilling in such first end cap connecting one end of said first intermediate drilling with said first spool end chamber and a first deadended drilling in said second end cap communicating with the other end of said first intermediate drilling, and the other of said wave tubes includes a second intermediate drilling extending through said block, a second connecting drilling in said second end cap connecting one end of said second intermediate drilling with said second spool end chamber and a second deadended drilling in said first end cap communicating with the other end of said second intermediate drilling.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Servomotors (AREA)
US00369789A 1973-06-14 1973-06-14 Servovalve with oscillation filter Expired - Lifetime US3857541A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US00369789A US3857541A (en) 1973-06-14 1973-06-14 Servovalve with oscillation filter
GB3506873A GB1375517A (ja) 1973-06-14 1973-07-23
JP9479873A JPS5610484B2 (ja) 1973-06-14 1973-08-23
DE19732343552 DE2343552A1 (de) 1973-06-14 1973-08-29 Elektrohydraulisches servoventil

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Application Number Priority Date Filing Date Title
US00369789A US3857541A (en) 1973-06-14 1973-06-14 Servovalve with oscillation filter

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Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4161161A (en) * 1976-03-15 1979-07-17 Societe D'etudes De Machines Thermiques S.E.M.T. Device for damping pressure waves in an internal combustion engine fuel injection system
FR2443595A1 (fr) * 1978-12-07 1980-07-04 Deere & Co Pompe ou moteur a debit variable
US4265272A (en) * 1979-10-01 1981-05-05 Eaton Corporation Transient start-up eliminator for pressure piloted valve
US4343329A (en) * 1978-12-06 1982-08-10 Textron Inc. Bistable fuel valve
USRE31107E (en) * 1978-12-07 1982-12-21 Deere & Company Feedback shaft extending between swashplate and displacement control valve
US4538633A (en) * 1983-02-18 1985-09-03 Parker-Hannifin Corporation Optical-hydraulic control system
US4646785A (en) * 1981-03-18 1987-03-03 Manfred Ruedle Spool valve
US4922963A (en) * 1989-02-27 1990-05-08 Hsc Controls Inc. Hydraulic servovalve
US5697401A (en) * 1995-07-14 1997-12-16 Ebara Corporation Hydraulic servovalve
US6755205B1 (en) * 2002-09-12 2004-06-29 Woodward Governor Company Method to stabilize a nozzle flapper valve
US20130221253A1 (en) * 2012-02-14 2013-08-29 Liebherr-Aerospace Lindenberg Gmbh Servo valve
CN103615431A (zh) * 2013-12-04 2014-03-05 中国航空工业第六一八研究所 用于液压作动器伺服阀的散热力矩马达罩
CN109083879A (zh) * 2018-08-09 2018-12-25 杭州电子科技大学 一种抑制喷嘴挡板式电液伺服阀前置级气穴现象的方法
US20190277314A1 (en) * 2018-03-08 2019-09-12 Hamilton Sundstrand Corporation Valve body for a servovalve
US20190331256A1 (en) * 2018-04-26 2019-10-31 Hamilton Sundstrand Corporation Servovalve
US10900587B2 (en) 2018-03-29 2021-01-26 Hamilton Sunstrand Corporation Valves
US11209026B2 (en) * 2019-03-29 2021-12-28 Hamilton Sundstrand Corporation Servo valves
US11852174B1 (en) * 2021-08-25 2023-12-26 Hamilton Sundstrand Corporation Filter assembly for a servovalve

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JPS59165890U (ja) * 1983-04-22 1984-11-07 長尾　秀喜 全油圧式クロ−ラ−クレ−ン
JPS6022549U (ja) * 1983-07-21 1985-02-16 油谷重工株式会社 油圧ショベル用アタッチメント
JPS6110357U (ja) * 1984-06-22 1986-01-22 油谷重工株式会社 油圧シヨベルのクレ−ン装置
JPS6110356U (ja) * 1984-06-22 1986-01-22 油谷重工株式会社 油圧シヨベルのクレ−ン装置
AT386054B (de) * 1985-09-06 1988-06-27 Vni I Pk I Promy Gidroprivodov Elektrohydraulischer verstaerker-umformer
US4922217A (en) * 1988-06-17 1990-05-01 Hsc Controls, Inc. Torque motor with magnet armature
WO2018198355A1 (ja) * 2017-04-28 2018-11-01 ピー・エス・シー株式会社 フィードバックばねを用いた気体圧サーボ弁
CN112549492B (zh) * 2020-10-10 2023-09-12 浙江长海包装集团有限公司 一种加工复合包装膜的挤出机的过滤装置

Citations (2)

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US3095906A (en) * 1959-03-05 1963-07-02 Moog Servocontrols Inc Flow control servo valve with dynamic load pressure feedback
US3347252A (en) * 1965-06-18 1967-10-17 United Aircraft Corp Fluid signal generator

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3095906A (en) * 1959-03-05 1963-07-02 Moog Servocontrols Inc Flow control servo valve with dynamic load pressure feedback
US3347252A (en) * 1965-06-18 1967-10-17 United Aircraft Corp Fluid signal generator

Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4161161A (en) * 1976-03-15 1979-07-17 Societe D'etudes De Machines Thermiques S.E.M.T. Device for damping pressure waves in an internal combustion engine fuel injection system
US4343329A (en) * 1978-12-06 1982-08-10 Textron Inc. Bistable fuel valve
FR2443595A1 (fr) * 1978-12-07 1980-07-04 Deere & Co Pompe ou moteur a debit variable
US4229144A (en) * 1978-12-07 1980-10-21 Deere & Company Feedback shaft extending between swashplate and displacement control valve
USRE31107E (en) * 1978-12-07 1982-12-21 Deere & Company Feedback shaft extending between swashplate and displacement control valve
US4265272A (en) * 1979-10-01 1981-05-05 Eaton Corporation Transient start-up eliminator for pressure piloted valve
US4646785A (en) * 1981-03-18 1987-03-03 Manfred Ruedle Spool valve
US4538633A (en) * 1983-02-18 1985-09-03 Parker-Hannifin Corporation Optical-hydraulic control system
US4922963A (en) * 1989-02-27 1990-05-08 Hsc Controls Inc. Hydraulic servovalve
US5697401A (en) * 1995-07-14 1997-12-16 Ebara Corporation Hydraulic servovalve
US6755205B1 (en) * 2002-09-12 2004-06-29 Woodward Governor Company Method to stabilize a nozzle flapper valve
US20130221253A1 (en) * 2012-02-14 2013-08-29 Liebherr-Aerospace Lindenberg Gmbh Servo valve
US9702478B2 (en) * 2012-02-14 2017-07-11 Liebherr-Aerospace Lindenberg Gmbh Servo valve
CN103615431A (zh) * 2013-12-04 2014-03-05 中国航空工业第六一八研究所 用于液压作动器伺服阀的散热力矩马达罩
CN103615431B (zh) * 2013-12-04 2015-12-09 中国航空工业第六一八研究所 用于液压作动器伺服阀的散热力矩马达罩
US20190277314A1 (en) * 2018-03-08 2019-09-12 Hamilton Sundstrand Corporation Valve body for a servovalve
US10900587B2 (en) 2018-03-29 2021-01-26 Hamilton Sunstrand Corporation Valves
US20190331256A1 (en) * 2018-04-26 2019-10-31 Hamilton Sundstrand Corporation Servovalve
EP3562013B1 (en) * 2018-04-26 2021-11-03 Hamilton Sundstrand Corporation Servovalve
US11226056B2 (en) 2018-04-26 2022-01-18 Hamilton Sundstrand Corporation Servovalve
CN109083879A (zh) * 2018-08-09 2018-12-25 杭州电子科技大学 一种抑制喷嘴挡板式电液伺服阀前置级气穴现象的方法
US11209026B2 (en) * 2019-03-29 2021-12-28 Hamilton Sundstrand Corporation Servo valves
US11852174B1 (en) * 2021-08-25 2023-12-26 Hamilton Sundstrand Corporation Filter assembly for a servovalve

Also Published As

Publication number Publication date
DE2343552A1 (de) 1975-01-09
GB1375517A (ja) 1974-11-27
JPS5015978A (ja) 1975-02-20
JPS5610484B2 (ja) 1981-03-09

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