US3389719A - Electrohydraulic servovalve having minimum flow during quiescent operation - Google Patents

Electrohydraulic servovalve having minimum flow during quiescent operation Download PDF

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Publication number
US3389719A
US3389719A US49719665A US3389719A US 3389719 A US3389719 A US 3389719A US 49719665 A US49719665 A US 49719665A US 3389719 A US3389719 A US 3389719A
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US
United States
Prior art keywords
valve
shaft
armature
tube
servovalve
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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English (en)
Inventor
Robert K Van Ausdal
Donald V Healy
John P Anderson
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Bendix Corp
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Bendix Corp
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Filing date
Publication date
Application filed by Bendix Corp filed Critical Bendix Corp
Priority to US49719665 priority Critical patent/US3389719A/en
Priority to GB4524266A priority patent/GB1120288A/en
Priority to FR80265A priority patent/FR1500491A/fr
Application granted granted Critical
Publication of US3389719A publication Critical patent/US3389719A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • F15B13/0438—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

Definitions

  • An eleclrohydraulic servovalve including a torque motor with an armature and a flapper member attached at its center and movable with the armature for varying the flow of control fluid to one side or the other of a spool valve which, in turn, controls the application of fluid pres sure to a hydraulic motor.
  • the flapper member is attached to a shaft rotatable along the axis of rotation of the armature.
  • a spring-loaded poppet valve is attached at each end of the flapper member to block the flow of fluid to the spool valve in the absence of a control signal such that there will be minimum flow and minimum noise genera'ed when there is no input signal or an input signal below a specific level.
  • This invention relates to electrohydraulic servovalves, and more particularly to a dry type valve in which the electrical parts are sealed from the actuating fluid and in which there is a minimum of flow from the control orifices during quiescent or no-input signal operation.
  • FIGURE 1 is an isometric projection, partially cut away to show details of an electrohydraulic servovalve incorporating our invention.
  • FIGURE 2 is a sectional drawing of a valve structure shown schematically in FIGURE 1.
  • FIGURE 3 is a graph showing the transfer characteristic of a servovalve such as that shown in FIGURE 1 when no means was employed to correct for the dead band around the point of zero electrical input.
  • FIGURE 4 is a graph like that of FIGURE 3, but showing substantially improved response in the region of zero electrical input.
  • the electric motor assembly shown generally at numeral 10, includes a pair of bar magnets 12 and 14 mounted to introduce flux into a pair of ferromagnetic frame members 16.
  • the frame members 16 include arms 18 terminating in faces 20 and 22 opposite the ends of an armature 24 mounted for rotation on a support 26. Armature 24 passes through central openings in a pair of coils 28 and 30 which are held in place wilhin the enclosure made by the frame member 16.
  • the armature 24 is lightly held midway between the op posing faces of the magnetic frame members 16 for movemeat from the mid-position under the control of changes in flux in the magnetic system resulting from passage of current through the coils 28 and 39.
  • the support 26 for armature 24 is itself carried by an upstanding tubular support, hereinafter designated the torque tube 32, including an enlarged collar portio. 34 which is sealed to an opening in a wall 36 in the housing of the hydraulic assembly.
  • the upper end of torque tube 32 is closed by a central shaft member 38 sealed therein as by brazing or an interference fit.
  • the seal between shaft 38 and the torque tube 32 must be adequate to at least resist the drain or return hydraulic pressure and to prevent the ingress of hydraulic fluid from the hydraulic assembly to the motor assembly 19.
  • the tube 32 is preferably of a spring material, such as Inconel X or beryllium copper, having a thin wall in the order of 0.006 to allow rotational movement of the armature 24 around the axis of the tube 32 by twisting of the tube 32.
  • Shaft 38- includes a notched section 39 of reduced cross-sectional area whose function is to reduce resistance to forces tending to bend the shaft. The purpose of this is discussed below.
  • the hydraulic system used in combination with the motor assembly it provides the power for controlling a double-acting piston 5% which reciprocates within a cylinder 52.
  • Control pressure to one side or the other of piston is communicated through a pair of conduits 54 and 56 which communicate with a cylinder 58 containing a spool valve member 60 urged toward a centered position by means of a pair of springs 62 and Hydraulic fluid under pressure is supplied to spool valve cylinder 53 from a. reservoir 66 by means of a pump 68 which pumps the fluid through a conduit 70, which may contain a filter 72, and to a pair of inlet passageways 74 and 76.
  • conduit 78 Also connected to conduit is a passage which supplies hydraulic fluid under pressure to each of two identical branches of the servo system, one containing a valve 8?. in communication with a conduit 84 which is connected at one end with one end of the spool valve cylinder 58 and at its opposite end with a reservoir 86 which includes a filtering screen 88 and from thence through a short channel 90 to a chamber 92 containing the poppet valve mechanism referred to above.
  • the other branch contains a valve 94 which communicates with a conduit 96 connected at one end with the other end of the spool valve cylinder 58 and at its opposite end with a reservoir 98 having a filtering screen 186 and from thence through a channel 102 to a chamber 104 containing another poppet valve mechanism.
  • the end section 44 of bar 40 carries a contact member 196 which is somewhat pointed on one end to make a low friction contact with a spring retainer 108.
  • a spring bears against retainer 188, and the force exerted thereby is adjustable by means of a second spring retainer member 112 which is threadedly engaged with a sleeve 114 held in chamber 92.
  • the opposite end of contact member 106 is fiat and acts against the somewhat rounded contact surface of a poppet valve member 116.
  • poppet 116 seats against an annular seat on a member 118 aflixed within a sleeve member 120 held stationary within chamber 92.
  • Poppet 116 controls communication between a passageway within seat member 118 and a port 122 which communicates with an annular chamber 124.
  • a conduit 126 connects chamber 124 with the low pressure or return side of the hydraulic system.
  • a housing 130 includes a cylindrical sleeve member 132 having a reduced diameter portion 134 which cooperates with an interior wall of housing 130 to form an annular chamber 136. Ports 138 in portion 134 provide communication between the interior of member 132 and chamber 136 and from thence to conduit 84.
  • Axially slidable within sleeve 132 is a poppet valve member 140 which is urged against a seat 142 by means of a spring 144.
  • Poppet 146 includes a small orifice 146 and a plurality of larger ports 148. A larger orifice is located upstream of seat 142 and is formed in a plate 152 secured between seat member 142 and an annular spacer 154.
  • the purpose of the servo valve structure is to control the flow of hydraulic fluid to one side of actuating piston 59 in cylinder 52.
  • the opposite sides of the hydraulic system are symmetrical; therefore, if bar 40 is centered and both of the poppet valve members in chambers 92 and 104 are closed and hydraulic fluid is supplied from pump 68 through conduit 70 and filter 72 to conduits 74 and '76 and through passageway 80 and valves 82 and 94 to conduits 84 and 96, the fluid pressures acting against the opposite sides of spool valve 60 are equal and spool 60 is maintained in its centered position. So positioned, it blocks flow from passages 74 and 76 as Well as from passages 54 and 56. The fluid pressure on opposite sides of piston 51 remains stabilized, and piston 50 does not move.
  • Movement of poppet valve member 116 off its seat permits fluid to flow from the interior of seat member 118, through port 122, into chamber 124 and through conduit 126 to the low pressure side of the hydraulic system. This causes a reduction in the fluid pressure acting against the right end of spool valve 60, causing it to move toward the right against the pressure spring 64 and communicating high pressure fluid in passage 76 with conduit 56 and the right side of piston 50. Simultaneously, the left side of piston 50 is placed in communication with the low pressure side of the hydraulic system through conduits 54 and 78, thus causing piston 59 to move toward the left. Introduction of the opposite signal into windings 28 and 30 causes movement of bar 40 around its end 44 and opening of the poppet valve in chamber 104.
  • valves 82 and 24 are replaced by simple fixed restrictions or bleeds such as that in plate 152 (FIGURE 2).
  • FIGURE 3 where the electrical input is plotted on the horizontal axis and the differential chamber pressure on the vertical axis. The electrical input will be seen to vary over a range from approximately 10 to +10 milliamperes with only a negligible change in differential chamber pressure. The next increment of -10 ma. or +10 ma. produces substantial differential chamber pressures.
  • the slope through neutral is basically dependent on the ratio of the area of orifice 146 to the effective area of the port defined by poppet 116 and seat 118.
  • the point of transition from the steep slope to the normal slope is determined by the force exerted by spring 144 against piston 140 and which may be varied by adding to or subtracting from a number .of shims 156.
  • an electrohydraulic servovalve including a coil for receiving electrical signals
  • a hydraulic system including a housing and a source of actuating fluid
  • a flow control system within said housing including a pair of substantially parallel passageways connected to said source, valve means for closing each of said passageways, resilient means urging both said valve means in a closing direction, and an elongated motion-transmitting member connected to said valve means,
  • said armature comprising a non-rigid tube having one end sealed to said housing and a shaft sealed to the opposite end of said tube and extending through said tube, said shaft being coupled approximately midway along said motion-transmitting member to transmit torque from said armature to said member to open the opposite of said valve means, said shaft including a section having a reduced cross-sectional area for reducing its resistance to bending forces,
  • valve cylinder connected to said source
  • a spool valve positioned within said cylinder and means communicating the fluid pressure in said passageways to opposite ends of said spool valve to vary the position of said spool.
  • an electrohydraulic servovalve including a coil for receiving electrical signal-s;
  • a hydraulic system including a housing and a source of actuating fluid
  • a flow-control system Within said housing including a pair of substantially parallel passageways connected to said source, flow restriction means in each of said passageways, valve means for closing each of said passageways, resilient means maintaining both said valve means normally closed, and an elongated motion-transmitting member connected to said valve means,
  • said armature comprising a non-rigid tube having one end sealed to said housing and a shaft sealed to the opposite end of said tube and extending through said tube, said shaft being coupled approximately midway along said motion-transmitting member to transmit torque from said armature to said member to cause said member to efiectively be rotated around one of said valve means and to open one of said valve means, said shaft including a section having a reduced cross-sectional area for reducing its resistance to bending forces resulting from said rotation,
  • valve cylinder connected to said source
  • a spool valve positioned within said cylinder and means communicating the fluid pressure in said passageways to opposite ends of said spool valve to vary the position of said spool.
  • each of said flow-restriction means includes, in series, means defining a primary orifice and a piston carrying a poppet valve including an orifice of smaller effective area and means for urging said poppet valve in a closing direction such that when said poppet valve is closed, the effective area of said restriction is defined by said poppet valve orifice and when said poppet valve is opened in response to pressure differentials across said piston exceeding a predetermined value, the effective area of said restriction is defined by said primary orifice.
  • a servovalve comprising:
  • a flow-control system within said housing including a pair of substantially parallel passageways connected to said source, poppet valves for closing both of said passageways, resilient means maintaining both said poppet valves normally closed, and an elongated motion-transmitting member connected to said poppet valves;
  • said tube and shaft supporting said motion-transmitting member for permitting simultaneous opening of said poppet valves in response to increases in pressure from said source.
  • a servovalve comprising:
  • a flow-control system Within said housing including a pair of substantially parallel passageways connected to said sour-cc, valve means for closing both of said passageways and an elongated motion-transmitting mernber connected to said valve means;
  • said tube and shaft supporting said motion-transmitting member for permitting simultaneous opening of both of said valve means in response to increases in pressure from said source.
  • a servovalve comprising:
  • a flow-control system within said housing including a pair of substantially parallel passageways connected to said source, valve means for closing both of said passageways and an elongated motion-transmitting member connected to said valve means;
  • valve cylinder connected to said source
  • a spool valve positioned within said cylinder
  • a servovalve comprising:
  • a flow-control system within said housing including a pair of substantially parallel passageways connected to said source, poppet valve for closing both of said passageways, resilient means urging both of said poppet valves in a closing direction, and an elongated motion-transmitting member connected to said poppet valves;
  • said shaft being coupled approximately midway along said motion-transmitting member to transmit torque from said motor means to said member to cause said member to rotate around one of said poppet valves and open the other of said poppet valves, said shaft including a section having a reduced cross-section for reducing its resistance to bending forces resulting from said rotation.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Servomotors (AREA)
US49719665 1965-10-18 1965-10-18 Electrohydraulic servovalve having minimum flow during quiescent operation Expired - Lifetime US3389719A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US49719665 US3389719A (en) 1965-10-18 1965-10-18 Electrohydraulic servovalve having minimum flow during quiescent operation
GB4524266A GB1120288A (en) 1965-10-18 1966-10-10 Hydraulic servo valve having minimum flow during quiescent operation
FR80265A FR1500491A (fr) 1965-10-18 1966-10-17 Servo-soupape électro-hydraulique perfectionnée

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US49719665 US3389719A (en) 1965-10-18 1965-10-18 Electrohydraulic servovalve having minimum flow during quiescent operation

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US3389719A true US3389719A (en) 1968-06-25

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US (1) US3389719A (fr)
FR (1) FR1500491A (fr)
GB (1) GB1120288A (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3756262A (en) * 1971-04-09 1973-09-04 Sperry Rand Corp Power transmission

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3756262A (en) * 1971-04-09 1973-09-04 Sperry Rand Corp Power transmission

Also Published As

Publication number Publication date
FR1500491A (fr) 1967-11-03
GB1120288A (en) 1968-07-17

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