US3473547A

US3473547A - Electromechanical driver for hydraulic valve and the like

Info

Publication number: US3473547A
Application number: US668142A
Authority: US
Inventors: James L Coakley
Original assignee: Abex Corp
Current assignee: PepsiAmericas Inc
Priority date: 1967-09-15
Filing date: 1967-09-15
Publication date: 1969-10-21
Anticipated expiration: 1986-10-21
Also published as: DE1764973A1; FR1575978A; GB1192689A

Description

Oct. 21, `1969 J. coAKLEY 3,473,547

ELECTROMECHANICAL DRIVER FOR HYDRAULIC VALVE AND THE LIKE oct. 21, 1969 J, L, COAKLEY 3,473,254?

ELECTROMECHA'NICAL DRIVER FOR HYDRAULIC VALVE AND THE LIKE A Filed Sept. 15. 1967 5 Sheets-Sheet 2 INVENTOR.

Bmg/

Oct. 2l, 1969 J. coAKLEY ELECTROMECHANICAL DRIVER FOR HYDRAULIC VALVE AND THE LIKE Filed Sept. l5, 1967 3 Sheets-Sheet 5 L V uw BWM United States Patent O U.S. Cl. 137-83 8 Claims ABSTRACT F THE DISCLOSURE An electromechanical transducer or driver is disclosed which is suitable for positioning a movable control member of a valve or the like for regulating the flow or other operational characteristics thereof. The driver includes a magnetic core and a working gap in magnetic series circuit with the core; a control signal responsive winding flux linked to the core which esta-blishes a ow of flux through the gap directed from one pole to the other and generates a magnetomotive force across the gap proportional to the ampere turns of the winding; and an armature mounted in the gap for reluctance varying shear motion normal to the flux direction in the gap in response to an electrical control signal dependent mechanical force applied thereto, the armature being connectable to a movable valve control member for regulating the flow characteristics thereof in response to control signals applied to the winding.

In one preferred form of this invention the armature is designed with constant width and thickness to provide a constant rate of change of permeance with displacement along its direction of motion, thereby rendering the force applied to the armature a function of only one variable, namely, the square of the current input to the winding.

In another preferred form of this invention a pair of electromechanical drivers are provided and operated in a push-pull configuration to make the force applied to the armature a linear function of the current level produced in the winding by the control signal.

This invention relates to electromechanical transducers or drivers for positioning movable control members, and more particularly to an improved electromechanical transducer or driver of the shear type uniquely adapted for positioning the movable control member of a hydraulic valve.

Electromechanical transducers or drivers of the type suitable for controlling hydraulic valves, broadly considered, typically |include three principal elements, namely, a magnetic core, a control winding, and an armature. The core is provided with a gap within which is mova'bly mounted the armature for providing a mechanical output in response to the flux changes in the gap generated by the application of a signal to the control winding.

Electromechanical drivers of the above type having in common the structural and operational features enumerated, can be divided into two principal categories, Inamely, the tractive type or the shear type, depending on the characteristic motion of their armatures relative to the direction of the flux within the gap. Drivers of the tractive type employ armatures which move parallel to the directionvof the flux in the gap, either toward or away from a given pole, in response to forces of magnetic attraction, hence, the name tractive driver. Drivers of the other type, that is, the shear type, utilize armatures which move i-n a direction normal to the direction of the flux in the gap, hence, the term shear driver. It is this latter type of driver, the shear type, to which this invention relates.

The electromechanical drivers of the shear type which are to be found in the prior art generally suffer from one or more structural or operational deficiencies which seriously limit their application, the exact deficiency depending on the details of the particular driver involved. For example, some prior art drivers are not susceptible to linearization of their mechanical outputs, or if susceptible, are only so with the aid of rather elaborate compensation arrangements.

In other prior art shear drivers, the relationship of the armature to the gap is such that iiux must travel the entire length of the armature giving rise to the need for a massive armature if saturation is to be avoided. The problem with drivers of this type is that the large mass of the armature increases its inertia with the result that frequency response is lowered.

It is also not uncommon in certain of the prior art shear-type drivers, particularly those in which the armature is mounted for rotation on a pivot-type support, for frictional problems to develop. These give rise to lubrication diiculties, increase the response time of the device, and render it insensitive to signal variations below that necessary to overcome the static friction of the suspension system.

Finally, many of the prior art drivers of the shear type require the use of permanent magnets, in addition to the conventional control Winding, for establishing the necessary magnetic flux for proper operation. This has the obvious drawback of added cost and complexity.

It has been a principal objective of this invention to provide a shear-type electromechanical driver for a hydraulic valve which has enhanced inertial and frictional characteristics, does not require permanent magnets, and is readily susceptible to linear operation. This objective has been accomplished in accordance with certain of the principles of this invention by incorporating into the design of an electromechanical driver for hydraulic valve a ve1y unique and unobvious concept in which a control winding, single gap magnetic core, and armature cooperate in a highly novel fashion to impart motion to a movable valve control member, and thereby control the flow pattern of the valve in accordance with input control signals to the Winding.

More specifically, the electromechanical driver design of this invention contemplates providing a magnetic core having a pair of pole pieces defining a Working gap, and a control Winding for establishing a control signal responsive fiux which flows from one pole to another in a predetermined direction. Additionally, the driver includes an armature mounted in the gap for rectilinear reluctance varying shear motion. The armature traverses the working gap in a direction normal to the flux in response to an applied mechanical force which varies with the input current to the control winding. The armature is connected to a movable control member of the hydraulic valve being operated, and positions the member for controlling the flow pattern of the valve in response to rectilinear movement of the armature produced by the mechanical force generated by the control signal input to the winding.

With the structure of this invention, the armature can be mounted directly to the movable valve control member, thereby eliminating the frictional effects of a separate rotational or pivotal mounting arrangement typical of many prior art shear-type drivers. Additionally, with this invention, the flux passes transversely through the armature, rather than along its length. It is not, therefore, necessary to have a large armature cross-section to prevent saturation. Consequently, armature mass is kept to a minimum, reducing inertial effects and correspondingly enhancing frequency response. Finally, with this invention, the effective working gap in the region occupied by the armature is, except for fringing effects at the edges of the armature, the sum of the two gaps formed by the armature and the respective poles between which it is positioned. Since this sum is independent of the exact vertical position of the armature within the working gap, the driver is substantially insensitive to null shifts due to geometry changes produced by temperature and pressure iluctuations.

A further and equally important feature of the driver of this invention is that there are no gaps in the core other than working gaps, that is, gaps not traversed in shear by a reluctance varying armature. Consequently, there are no fixed gaps in the core having a constant reluctance. In a core so designed, that is, with only working gaps, the magnetomotive force across the gap, which in part determines the mechanical force on the armature and, hence, armature displacement, is not dependent on position of the armature within the gap, but rather only on the ampere turns of the winding. With the magnetomotive force dependent only on ampere turns, the mechanical force can, by incorporating certain further design principles of the invention, be made dependent only upon the input current. In addition, by incorporating certain other design principles of this invention, the mechanical force can be linearized.

In accordance with certain of the additional principles of this invention, in a preferred embodiment the armature is designed with constant width to provide constant rate of change of permeance with displacement along its direction of motion. With an armature so designed the mechanical force on the armature is made to function only of the square of the input current. This has the advantage of rendering the change in force on the armature for a given change in input current nearly constant, and thus, independent of armature position within the gap.

In accordance with certain other principles and objectives of this invention an electromechanical driver has been provided which has a linear output. This has been achieved by connecting the armatures of a pair of drivers to the valve control element and operating the driver in a push-pull conguration. Such push-pull operation can be obtained in a number of ways, for example, by mounting auxiliary bias windings on the cores for providing steady state ux levels having directions which respectively add and subtract from the ilux generated in the cores in response to identical control signal inputs to the control windings.

Another objective of this invention, which is appropriately used when the armature of the electromechanical transducer is utilized to drive a jet-pipe of a jet-pipe type valve, has been to hydraulically isolate the armature, windings, and core from the nozzle or discharge end and receiver of the jet-pipe valve. This objective has been accomplished by a two-step design procedure which includes mounting the driver and jet-pipe such that the nozzle or discharge end of the jet-pipe is directed away from the driver, and surrounding the jet-pipe with an annular, radially extending baiile. The bale prevents back spray, which is produced when the uid jet is directed against the receiver, from penetrating the region behind the bale containing the armature, core and winding.

Other objectives and advantages of this invention Will be more readily apparent from a detailed description of the invention taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a schematic view in perspective of a pair of the electromechanical transducers of this invention showing their use as drivers for a jet-pipe valve;

FIGURE 2 is a front elevational view in cross-section of atwo-stage servovalve which embodies a pair of the electromechanical transducers of this invention for driving a jet-pipe valve constituting the iirst servovalve stage;

and

FIGURE 3 is a side elevational view in cross-section of the servovalve of FIGURE 2.

One preferred form of an electromechanical transducer or driver embodying certain of the principles of this invention and suitable for controlling a hydraulic valve is depicted in FIGURE 1, and is generally indicated by the reference numeral 12. Referring to FIGURE 1, the electromechanical driver 12 is seen to include a laterally movable armature 18 operatively coupled to a pivotal jet-pipe 20 of a hydraulic jet-pipe valve 14. In operation, electrical inputs in the form of control signals are input on

lines

16A and 16B to the driver 12, and operate to produce a mechanical output in the form of a displacement of the movable armature 18. The displacement of the armature 18, which constitutes the mechanical output of the electromechanical driver 12, is transmitted to the jet-pipe 20, which constitutes the input of the hydraulicjet-pipe valve 14. Movement of the jet-pipe 20, in turn, causes variations to be produced in the hydraulic flow characteristics of the receiving ports 22A and 22E of the valve 14. These flow variations constitute the output of the hydraulic jet-pipe valve 14. Thus, an electrical control signal input to the driver 12 on lines 16A and 1 6B, via

movement of the armature 18 and jet-pipe 20, provides a hydraulic output at

receiver ports

22A and 22B, thereby completing the electrohydraulic transducing function characteristic of an electromechanically driven valve.

The electromechanical driver 12, considered in more detail, includes `a pair of identical

force motor sections

24A and 24B. The corresponding elements of the

rnotor sections

24A and 24B bear identical reference numerals, except that the elements of the motor section 24A are suixed by the letter A, while thel elements of motor section 24B are sufxed by the letter B. Since the motor sections 24A :and 24B are identical, only one motor section, namely, motor section 24A, is described.

Motor section 24A includes a control winding 26A which is responsive to the control signals input on line 16A. The control winding 26A is wound on one section of 'a substantially C-shaped magnetic core 27A, preferably fabricated of soft iron. The iron core 27A is continuous, except for a sole working gap 28A dened by an upper pole piece 29A and a lower pole piece 30A, thereby providing a single loop magnetic circuit path which includes the series circuit `arrangement of the iron core 27A and the gap 28A.

Positioned between the

pole pieces

29A and 30A is one side 18A of the armature 18 constituting the output of the motor section 24A. The armature section 18A is flxedly mounted to the jet-pipe 20` and by reason of such mounting is constrained to move in the gap 28A in the X-Z plane which is substantially normal to an imaginary line directed parallel to the Y :axis connecting

pole pieces

29A and 30A. Such movement of the armature section 18A in a plane normal to an imaginary line joining the

polt pieces

29A and 30A, herein termed shear motion, constitutes movement normal to the direction of the magnetic llux in the gap 28A, and is effective to change the reluctance of the gap. This shear motion of armature section 18A is to be distinguished from tractive motion wherein the total gap reluctance is not appreciably changed which is characterized by movement of an armature along the Y axis in a direction toward or away from the pole pieces, that is, in a direction parallel to the magnetic ilux in the gap.

The armature section 18A is rectangular and is uniform throughout its entire length -as measured along the Z axis in both thickness as measured along the Y `axiis and depth as measured along the X axis. With such a rectangular shape 'and thickness uniformity, movement of the armature section 18A in shear :within the gap 28A produces ra change in reluctance of the gap per unit change of the armature position in the Z direction which is constant in magnitude. While the reluctance of gap 28A is changed by movement of the armature section 18A in shear in the Z direction, the reluctance of the gap is notappreciably changed by movement of the armature in the Y direction. Therefore, exact positioning of the armature section 18A in the Y direction with respect to the

pole pieces

29A and 30A is not necesary. In fact, it has been found that the operation of the motor section 24A is little affected by the Y coordinate position of the arrnature section 18A, the reluctance of the gap 28A for any Z coordinate position :of the armature being essentially the same regardless of the karmature Y coordinate position. This result is attributable tothe fact that the portion of the total Working, gap 28A in the region occupied by the armature is, except for fringing effects at the edges of the |armature, equal to the sum of the individual gaps 28A-1 and 28A-2 between the armature Section 18A rand the

poles

29A and 30A, respectively, and this sum does not change with movement of the armature'18A in the Y direction notwithstanding the individual gaps 28A-1 and 28A-'2 may change.

It is to be noted that the core 27A has no gaps other than of the type herein defined as a working gap wherein the gap is traversed in shear by za reluctance-varying armature such as gap 28A traversed in shear by reluctance-varying armature section 18A. Consequently, there are no xed gaps in the core fhaving a constant reluctance. In a core so designed, that is, with only working gaps, such as core 27A with working gap 28A, the magnetomotive force across the gap, in this case gap 28A, which in part determines the mechanical force on the armature, in this inst'ance armature section 18A, is not dependent on the exact position of the armature in the gap in the direction of its motion, herein the Z direction, but rather on the ampere turns of the winding, namely, winding 26A. v

With the magnetomotive force of gap 28A dependent only on the ampere turns of winding 26A, the mechanical force applied to the armature section 18A in the positive Z direction can be made dependent only upon the input current to the winding by designing the armature with constant Width'and thickness Ato provideconstant rate of change of permeance with displacement along its direction of motion as in the preferred embodiment. Specifically, Wit-h the armature section 18A so designed the mechanical force on the larmature is rendered a function ofonly a single variable, namely, the square of the input current in the winding 26A. This mechanical force is proportional to the sum of (a) the square of the magnetomotive force across the gapl and- (b) the derivative of the permeance of the total working gap with respect to position of the armature in the Z direction. lSince the latter factor, the derivative of the perme'ance, is constant due to Z directionv armature uniformity, the mechanical force is a function only of the former factor, the square of the magnetomotive force which in this case is correlated to the square ofthe ampere turns of the winding and, hence, to the square of the current because nol tlxed -gaps exist, the only gaps present being of the variable reluctance, working type. y

The hydraulic jet-pipe valve` 14, considered in more detail, includes the hollow jet-pipe 20. The jet-pipe is responsive to movement of the armature 18, constituting the driver 12 output, and thereby constitutes the input for the hydraulic jet-pipe valve 14. The jet-pipe 20 has its upper pressure iluid inlet end 32 secured to a stationary support 31. This mounting permits the jet-pipe 20, which is resilient, to pivot in the Y-Z plane, in turn constraining the armature section 18A to traverse the gap 28A essentially in the X-Y plane. The lower outlet end or nozzle 34 'of the jet-pipe `20 is positioned in operative relationship to the

receiver ports

22A and 22B of a reciver 36, and operates in vconjunction therewith in a manner well known in the art. A passage 38 in the support 31 provides pressure uid to the inlet '32, of the jetpipe 20. Stationarily mounted slightly above the outlet end or nozzle 34 of jet-pipe 20 iand centrally disposed thereabout, is an annular, radially extending batlle 40. The baille 40 functions to substantially hydraulically isolate the region below the baille including the nozzle 34 of the jet-pipe 20 and the

receiver ports

22A and 22B from the region above the baille including the armature 18A and gap 28A.

The motor 12, including

sections

24A and 24B, may be operated in two principal modes with one of the modes having alternative submodes. In accordance with one of the principal modes of operation, herein termed the non-simultaneous signal mode, the

motor sections

24A and 24B are operated on an alternative basis, the particular motor section operated at any given instant being dependent -upon the direction of motion that is desired to impart to the armature 18 and, hence, to the jet-pipe 20. In the other principal mode of operation, herein termed the simultaneous signal mode, the

motor sections

24A and 24B are operated simultaneously in either a pushpull configuration, herein termed the push-pull simultaneous signal submode, or in a biased configuration, herein termed the biased simultaneous signal submode. In each of the foregoing submodes, the mechanical force on the armature of the driver is a linear function 0f the electrical control signal input thereto.

Considering in more detail the nonsimultaneous signal mode of operation, motion is imparted to the armature 18 and, hence, to the jet-pipe 20, in the positive Z direction by lapplying -an increasing strength signal on line 16A to the control winding 26A of motor section 24A. This produces an increase in the magnetic ilux llowing in the core 27A and, hence, an increase in the ilux passing through the gap 28A. The increased magnetic flux passing through the gap 28A exerts a force on the armature section 18A in the positive Z direction, causing the armature section 18A to move in shear transversely through the gap in the positive Z direction. Movement of the armature section 18A in the positive Z direction in turn moves the jet-pipe 20 in the positive Z direction, enabling the nozzle 34 to more fully communicate with the receiver port 22A, and thereby alter the ow characteristics in the jet-pipe valve receiver 36.

Motion is imparted to the armature 18 and, hence, to the jet-pipe 20, in the negative Z direction by applying an increasing magnitude signal on input line 16B to the control winding 26B of the motor section 24B. This results in the production of an increase in magnetic flux in the core 27B and, hence, an increased magnetic llux in the gap 28B. The increased magnetic ilux passing through the gap 28B exerts a force on the armature section 18B in a negative Z direction, causing the armature section 18B to move in shear transversely through the gap in the negative Z direction. This motion of the armature section 18B, in turn, moves the jet-pipe 20 in the negative Z direction, enabling the nozzle 34 to more fully communicate with ythe receiver port 22B, and thereby alter the ilow characteristics in the receiver 36 of the jet-pipe valve.

When the direction of movement of the armature 18 and, hence, jet-pipe 20, is changed from the positiveZ direction to the negative Z direction by the application of a signal to the input line 16B of Winding 26B of motor 24B producing negative Z direction forces on the armature section 18B, the control signal applied to input line 16A of winding 26A of motor section 24A terminates, resulting in a termination of the positive Z direction forces applied to the armature section 18A, enabling armature 18 to move under the laction of the restoring force of the jet-pipe 20 in the negative Z direction. Similarly, when the direction of movement of the armature 18 and, hence, jet-pipe 20 is changed from the negative Z direction to the positive Z direction by the application of -a signal to the input line 16A of winding 26A of motor 24A, which produces a positive Z direction force on the armature 18A, the control signal .applied to input line 16B of winding 26B of motor section 24B terminates, resulting in a term- -ination of forces on the armature section 18B, enabling armature section 18B to move under the action of the restoring force of the jet-pipe 20 in the positive Z direction.

When the driver 12 is operated in a push-pull conguration, which consititutes one of the two simultaneous signal submodes in which a linear mechanical force is provided, inputs are applied simultaneously to both of

lthe control windings

26A and 26B on

lines

16A and 16B. When input currents to both

control windings

26A and 26B are equal there is no net mechanical force on the armature. The Icurrent level at this condition is normally referred to as quiescent current. When a mechanical force is to be developed on the armature, then equal current changes in both windings from the quiescent level are made. However, the direction of the change is different in the two coils. That is, the current in one coil increases and the current in the other coil decreases. For example, assuming the magnitude of the quiescent current to the force motor or driver 12 is 10 units and the control current input on line 16A to the control winding 26A is increased by 2 units to l2 units, then the control current to the winding 26B on line 16B is decreased by 2 units to 8 units. The 2 unit increase in input to the motor section 24A on line 16A causes an increase in the net ux in the gap 28A, in turn causing a larger force to be applied to the armature section 18A. This increased force moves the armature section 18A further into the gap 28A, in turn moving the jet-pipe 20 in the positive Z direction enabling the nozzle 34 to more fully communicate with the receiver port 22A. The accompanying 2 unit decrease in input to the winding 26B of motor section 24B on line 16B causes a lesser flux to pass through the gap 23B, producing a lesser force on the armature section 18B, allowing the armature section 18B and, hence, the jetpipe 20 to move in the positive Z direction under the restoring force of the jet-pipe 20, thereby contributing to the change in position of the nozzle 34 to -a position more fully -communicating with receiver port 22A.

In like manner, if the control current input to the -

windings

26A and 26B of

motor sections

24A and 24B on

lines

16A and 16B, respectively, decrease and increase, respectively, causing lesser and greater net fluxes in

cores

27A and 27B, and gaps 28A and 28B, respectively, lesser and greater lforces are produced on the

armatures

18A and 18B, respectively. The application of decreasing and increasing forces to the

armatures

18A and 18B cause the jet-pipe 20 to move in the negative Z direction, permitting the nozzle 34 of Ithe jetpipe to more fully communicate with the receiver port 22B.

In the other simultaneous signal submode in which a linear mechanical force is provided, namely, the bias submode, the

motor sections

24A and 24B are provided with otherwise optional excitation windings (shown in phantom) to establish bias fluxes. Specically, independent windings are provided on the

cores

27A and 27B of

motor sections

24A and 24B which are provided with quiescent or steady state electrical signals for producing steady state flux levels equal in magnitude in

cores

27A and 27B and, hence, in gaps 28A and 28B. For example, the excitation winding of motor section 24A is provided with a steady state signal of 10 units producing a clockwise directed ilux in the core 27A and gap 28A, while the excitation winding of motor section 24B is provided with a steady state signal of l units for producing a counterclockwise flux path through the core 27B and gap 28B. The polarity of the bias signals depends on the direction in which the excitation windings are wound, which may be arbitrarily selected.

With clockwise and counterclockwise biasing fluxes present in the

cores

27A and 27B and gaps 28A and 28B, identical magnitude and polarity variations in control signals input on

lines

16A and 16B of

windings

26A and 26B produce variations in the net force applied to the

armatures

18A and 18B of opposite direction. For example, assume the input on

lines

16A and 16B of

control windings

26A and 26B each increase from 5 units to 7 units. Further assume that the

control windings

26A and 26B are wound to produce clockwise directed flux in the

cores

27A and 27B when input with the stated signals. With these assumptions, the increase in input signal to winding 26A from 5 units to 7 units produces a change in clockwise flux in core 27A which is additive to the existing clockwise ilux established by the excitation winding of core 27A, Whereas the same increase in input signal to winding 26B produces a clockwise flux which is subtrative from the counterclockwise flux produced by the excitation winding of core 27B. Prior to any armature movement, the additive effect of the flux in motor section 24A increases the net ilux in the gap 2SA from l5 units to 17 units, resulting in a larger force on the armature 18A. This larger force tends to move the armature 18A further into the gap 28A, in turn tending to move nozzle 34 of the jet-pipe 20` in more complete communication with the receiver port 22A. The subtractive effect of the clockwise ux in motor section 24B tends to decrease the net flux in the core 27B and gap 28B from 5 units to 3 units, causing a lesser force to be applied to the armature 18B. The lesser force applied to the armature 18B permits the resilient jet-pipe 20 and, hence, the nozzle 34 to move into more complete communication with receiver port 22A. Thus, the additive and subtractive eifects produced in the

motor sections

24A and 24B by identical increases of two units in the input signals on

lines

16A and 16B to the

control windings

26A and 26B contribute to moving the jet-pipe 20 to the new position with the nozzle 34 in more complete communication with the receiver port 22A.

In a similar manner, if the input signals on

lines

16A and 16B decrease by an identical amount as, for example, from 5 units to 3 units, the resulting changes in the net force applied to the

armatures

18A and 18B are opposite in direction. Specifically, should the inputs to the

motor sections

24A and 24B on

lines

16A and 16B decrease by two units, there is a net decrease in clockwise flux flowing through the core 27A and gap 28A, namely, from l5 units to 13 units. Consequently, a lesser force is applied to the armature section 18A in a direction tending to move it into the gap 28A. Thus, the nozzle 34 is free to move to a position wherein the nozzle 34 more fully communicates with receiver port 22B.

On the other hand, the 2 unit decrease in input to motor section 24B on line 16B produces a net increase in -ux llowing in the core 27B and the gap 28B, namely, from 5 units to 7 units, which is elective to apply a greater force to the armature section 18B `in a direction tending to draw it further into the gap 28B. Such an increased force on the armature 18B moves the nozzle 34 of the jet-pipe 20 in a direction tending to cause it to communicate more fully with receiver port 22B. Thus, identical decreases in inputs to the

motor sections

24A and 24B, although productive of subtractive and additive elects in the flux levels of the

cores

27A and 27B and gaps 28A and 28B, results in the application of additive force to the armature 18 and, hence, to the jet-pipe 20.

lIt is again noted at this point that the preceding two submodes of the simultaneous signal mode provide a mechanical force on the armature which is a linear function of the current in the control windings.

A preferred application of the electromechanical transducer 12 of this invention is as a component in an electrohydraulic servovalve used for controlling the flow rate and direction of lluid through a hydraulic motor. IReferring to FIGURES 2 and 3, an electrohydraulic servovalve 50 is shown which includes a jet-pipe valve 63 of the general type shown in FIGURE 1 as its iirst stage, and a spool valve generally indicated by the reference numeral 60 as its second stage. The jet-pipe valve 63 constituting the first servovalve stage is driven Iby an electromechanical transducer or force motor 65 of the type shown in FIGURE l whichis responsive to an electrical control signal for providing a mechanical input to the hydraulic jet-pipe valve 63. The first. stage hydraulic jet-pipe valve 63 in turn provides a hydraulic input to the second stage or spool valve 60 for controlling the ilow rate and direction of pressure fluid from a pressure line 51 to a reversible direction fluid motor y54.

The electromechanical transducer 65 which, Ias indicated previously, is similar to the electromechanical transducer 12 of FIGURE 1, includes a pair of

identical force motors

65A and 65B.

vSince force motors

65A and 65B are identical, only force motor 65A is described. Thisforce motor includes an iron core 62A continuous except for a working gap 66A formed by pole pieces 67A and 68A. The iron core 62A of force motor 65A includes upper Iand lower angled members 70A and 71A, upper and lower

horizontal members

72A and 73A and vertical member 74A.

Core members

70A, 71A, 72A, 73A and 74A are connected by

suitable fasteners

76A and 77A threadedly engaged in a vertical housing side wall or support member 78A. A nonmagnetic gap spacer 80A interposed between the upper and lower angled core sections 71A and 70A establishes the gap dimension. The force motor 65A further includes a control winding 85A on the core 62A and an 'armature 88A mounted .within the gap 66A formed by pole pieces 67A and 68A. The armature 88A is mounted to a resilient jet-tube 90 for movement in a direction essentially normal to an imaginary line connecting the pole pieces 67A and 67B. Also provided on the core 62A is an optional bias winding (shown in phantom) which is useful if the force motor 65A is operated in the bias submode. v n.

The .hydraulic jet-pipe valve 63 which, as indicated previously, is similar to the hydraulic jet-pipe valve of FIGURE l, includes the jet-pipe 9 0 having an upper pressure fluid inlet end 91 anda'lowe'r outlet end or nozzle 92. The jet-pipe 90 is `enclosed within a housing 89 which includes the side wall 78A, a side wall 78B, a rear wall 79, a front wall 82, and a top 93. The upper pressure inlet end 91 of the jet-pipe 90 is secured to the housing top 93 in any suitable manner as, for example, by a press tvin a blind hole 187. Intermediate the inlet pressure end 91 and nozzle 92 of the jet-pipe 90 is secured the armature 88 (se FIGURE 3).The mounting of the upper pressure inlet end 91 of the jet-pipe 90 to the horizontal support member 93 permits the resilient jet-pipe 90 to laterally deflect a limited amount, in turn permitting the armature sections 88A and 88By to traverse the working gaps 66A and 66B in yshear in the Z direction essentially normal to an imaginary line joining their associated pole pieces 67A and 68A, and 67B and 68B, respectively.

A bale 100 having an annular configuration is centrally disposed about the jet-pipe 90 with its lower surface 94 substantially flush with the nozzle 9.2. The baille 100 is integral with a hollow tubular support member 101 positioned in the lower portionof the jet-'pipe housing 89. A receiver plug 103 having receiver ports 104A and 104B is mounted immediately `below the nozzle 92.

The spool valve L60 includes a body or housing 110 having a cylindrical bore 111 formed therein which is sealed by end caps 108. Mounted within the bore 111 is a stationary sleeve 112 provided with

circumferential grooves

113, 114, 115 and `116. The sleeve 112 is positioned by retaining rings 109. Centrally disposed within the sleeve 112 is a bore 118 having five

radial passages

120, 121, 122, 123 and 124. The passages 120-124 communicate with the pressure line 51, a motor port 55, a drain line 126, a motor port 56 andthe pressure line 51, respectively, via the groove 113 and a body passage 130, the groove 114 and a body passage 131, a body passage 132, the groove 115 and a body passage 133, and the groove 116 and a body passage 134, respectively.

Stop lplugs 140 and 141 positioned in opposite ends of a bore 118 formed in sleeve 112 cooperate with opposite ends 142 and 143 of a spool 119 to form

cavities

144 and 145.

Cavities

144 and 145 communicate with the receiver ports 104A and 104B via body and

sleeve passages

147 and 149, and 148 and 150, respectively. The pressure differential of the fluid in

cavities

144 and 145 controls the position of the spool 119. This pressure differential is determined by the position of the nozzle 92 with respect to the receiver ports 104A and 104B, which in turn is determined by the forces acting on the armature sections 88A and 88B, which in turn is dependent upon the electrical signals input to the force motor windings A and 85B.

Axially displaced lands 155, 156, 157 and 158 are formed on the valve spool 119 and in conjunction with

peripheral spool grooves

159, 160 and 161 cooperate with the sleeve passages 1Z0-124, sleeve grooves 113-116 and body passages 130-134 to selectively interconnect or disconnect the pressure line 51, drain line 126 and motor ports 55 and 56.

With the spool 119 centered in the position shown in FIGURE 2, lands 156 and 157

block passages

121 and 123. This prevents the admission or exhaust of fluid from the motor ports 55 and 56, and thereby arrests the motion of, and locks, uid motor 54.

When the valve spool shifts to the left, which occurs when the nozzle 92 is shifted to the right for more fully communicating with the receiver port 104B, pressure line 51 communicates with motor port 56 via body passage 134, sleeve groove 116, sleeve passage 124, spool groove 161, sleeve passage 123, sleeve groove 115 and body passage 133, While the drain line 126 communicates with the motor port 55 via body port 132, sleeve passage 122, spool groove 160, sleeve passage 121, sleeve groove 114 and body passage 131. With the motor ports 55 and 56 .and the pressure and

drain lines

51 and 126 so connected, the motor 54 rotates in a first direction and at a speed determined by the degree to which the valve spool has shifted leftwardly.

When the valve spool 119 shifts to the right of the centered position shown in FIGURE 2, which occurs when the nozzle 92 of the jet-pipe 90 more fully communicates with receiver port 104A, pressure line 51 communicates with motor port 55 via -body port 130, sleeve groove 113, sleeve passage 120, spool groove 159, sleeve passage 121, sleeve groove 114, and body passage 131, while the drain line 126 communicates with the motor passage 56 via body passage 132, sleeve passage 122, spool groove 160, sleeve passage 123, sleeve groove 115, and body passage 133. With the pressure and drain lines 51v and 126 so connected to the motor ports 55 and 56, the motor 54 is driven in a second direction and at a rate determined by the extent to which the valve spool 119 has shifted rightwardly.

A feedback spring shown in FIGURE 3 interconnects the valve spool 119 and the jet-pipe 90 for mechanically feeding back spool motion to return the jetpipe 90 to its centered position when the spool has reached a position corresponding to the level of the electrical signal input to the electromechancial driver or force motor 65. The feedback spring 170 has an angled lower portion 171 and a horizontal upper portion 172 connected by an intermediate vertical portion 173. The lower angled portion 171 loosely lits within a hole 174 formed in the sleeve 112 and is secured at its extremity to the valve spool 119. The central vertical portion 173 of the feedback arm is loosely fitted in a vertical hole 175 formed in the body 110. The upper portion 172 of the feedback spring 170 is loosely fitted in a recess 176 for-med in a v rear housing wall 79 and a hole 177 formed in the hollow baffle support member 101. The upper portion 172 of feedback spring 170 is connected at its extremity to the jet-pipe 90 at a point intermediate the armature 88 and the nozzle 92.

A uid path from the high pressure line 51 to the inlet end 91 of the jet-pipe 90 is provided by the body pasage 134, a body passage 180, a body cavity 181 within which a iilter screen 182 is positioned, a body passage 183, a passage 184 formed in the rear housing wall 79, and blind holes 186, 187 and 188 formed in the housing top 93. A plug 185 seals blind hole 188.

In operation when the electrical control signal inputs to the windings 85A and 85B of

force motors

65A and 65B are such as to result in a net force on the armature 88 moving it to the left as viewed in FIGURE 2, the jetpipe 90 moves leftwardly more fully communicating nozzle 92 with receiver port 104A. This directs more pressure iluid into the cavity 144 via body passage 147 and sleeve passage 149. The increased flow of iluid in cavity 144 urges the valve spool 119 rightwardly. The velocity at which the valve spool 119 is initially driven in a rightwardly direction is dependent on the extent to which the nozzle 92 communicates with the receiver port 104A which in turn is dependent upon the net force on the armature 88 and, hence, on the electrical control signal input to the force motor 65. Regardless of the extent to which the valve spool 119 is ultimately driven by a given magnitude control signal as the valve spool 119 begins to move rightwardly from the centered position the pressure line 51 is interconnected to the motor port 55 and the drain line 126 is interconnected to the motor port 56 driving the motor in a first direction. As the valve spool 119 continues moving to the right the flow through the motor 54 increases, driving the motor at an ever-increasing speed.

The rightward motion of the spool 119 is also effective via the feedback spring 170, to exert a counterbalancing or feedback force on the jet-pipe 90 in a direction such as to restore the jet-pipe 90 to its center position. The feedback via spring 170 is such that as the valve spool 119 reaches the rightmost limit of travel associated with the particular magnitude signal input to the force motor 65, the feedback force applied to the jet-pipe 90 is equal and opposite to the net force on the armature 88 established by the electrical input signal. With the feedback force equal and opposite to the armature force, the jetpipe 90 returns to its centered position, equalizing the uid pressures in receiving port 104A and 104B, and thereby terminating spool 119 motion. In actual practice, the jet-pipe returns to a position just short of its centered position wherein it develops a very small pressure drop needed to support flow forces and the feedback spring force.

Although the jet-pipe 90 is centered and the pressure equalized in receiving ports 104A and 104B, the spool 119 dos not return to its centered position because there is no net force acting on it. With the spool so positioned, the jet-pipe remains centered under the counterbalancing force of the feedback spring 170 and the force of the armature 88. The spool 119 stays in its rightward position and the jet-pipe centered until the electrical input signal to the force motor 65 is altered.

If the signal to the motor 65 is increased such that there is an increase in the force on the armature 88, the armature force temporarily overcomes the feedback force applied to the jet-pipe by the spring 170 and the jet-pipe is shifted temporarily to the left more fully communicating the nozzle 92 with the receiver port 104A. This admits more fluid to the cavity 144 via the passages 147 and 149, in turn driving the spool 119 rightwardly. Further rightward movement of the spool 119 admits agreater flow of pressure fluid into the motor port 55 driving the motor at even a greater rate.

The additional rightward motion of the valve spool 119 eventually reaches a point where the additional feedback force provided by the spring 170 overcomes the additional armature 88 force provided by the increased magnitude signal whereupon the feedback force again balances and counteracts the armature force causing the jet- 12 pipe to return to its centered position. In the centered position the fluid pressure at receiver ports 104A and 104B is again equalized maintaining the valve spool 119 in its new position.

Should the magnitude of the electrical control signal input to the force motor 65 now decrease, the net armature force temporarily drops below the feedback force provided by the spring 170, allowing the jet-pipe 90 to move rightwardly more fully communicating nozzle 92 with the receiver port 104B. This produces a greater fluid pressure in receiver port 104B, allowing fluid to enter the cavity and correspondingly exhaust from cavity 144. This shifts the valve spool leftwardly. As the valve spool shifts leftwardly the land 156 seals off more of the sleeve passage 121 reducing the ilow rate of pressure uid to the motor port 55, causing the motor to run at a slower speed. The valve spool 119 continues moving leftwardly until the feedback force applied to the jet-pipe 90 again equals the force applied to the armature 88 by the thenexisting control signal. When this occurs the jet-pipe 90 becomes centered, equalizing the pressures in receiver ports 104A and 104B, and arresting the spool motion. The motor continues running at a reduced speed corresponding to the new spool position.

The production of the force necessary to move the armature v88 for positioning the jet-pipe 90 in response to a control signal input to the force motor 65 may be achieved in any of the various manners described with respect to the electromechanical transducer 12 of FIGURE 1. Specifically, it is possible, using a single control winding 85A and 85B in each

motor

65A and 65B, to operate in push-pull configuration. It is also possible using a single control winding 85A and 85B in each of the force motors 65A and `65B to selectively apply the control signals on an alternative basis to the windings, producing a force whose direction is dependent upon the particular force motor winding to which the signal is input. Alternatively, it is possible to incorporate into the force motors `65A and 65B, in addition to windings 85A and 85B separate excitation windings (shown in phantom) for establishing bias ilux levels in the cores.

I claim:

1. An electrohydraulic transducer comprising:

a hydraulic valve having a movable control member for regulating the low characteristics of said valve, and

a force motor including (a) a magnetic core having a control signal responsive control winding mounted thereon and a working gap therein defined by a pair of pole pieces through which magnetic ilux passes in a predetermined direction and across which exists a magnetomotive force proportional to the arnpere turns of said winding, said pole pieces and working gap being in a series magnetic circuit having no nonworking gaps or other appreciable additional reluctance, and

(b) an armature mounted in said working gap for reluctance varying motion normal to said predetermined direction in response to a control signal dependent force applied thereto, said armature being connected to said valve control member for moving said member in response to said control signals and thereby regulating the ow characteristics of said valve.

2. The electrohydraulic transducer of claim 1 wherein said armature is configured to provide a constant change in reluctance per unit change in displacement of said armature in said gap for rendering variations of said force solely dependent upon variations of the current in said winding produced by said control signal.

3. The electrohydraulic transducer of claim 2 wherein said hydraulic valve is a jet-pipe Valve, said movable control member s a jet-pipe mounted for pivotal motion toward and away from said gap, and said armature is mounted on said jet-pipe and constrained thereby for movement normal to said predetermined direction.

4. An electrohydraulic transducer comprising: a hydraulic valve having a movable control member for regulating the flow characteristics of said valve, a pair of force motors each including:

(a) a magnetic core having a control signal responsive control winding mounted thereon and' a working gap therein defined by a pair of pole pieces through which magnetic flux passes in a predetermined direction and across which exists a magnetomotive force equal to the ampere turns of said winding, said pole pieces and working gap being in a series magnetic circuit having no nonworking gaps or other appreciable additional reluctance, and

5. The electrohydraulic transducer of claim 4 wherein said armatures are configured to provide a constant change in reluctance per unit change in displacement of said armatures in their respective gaps for rendering variations of said electrical force solely dependent upon variations of the current in their associated control windings produced by their respective control signals.

6. The electrohydraulic transducer of claim 5 wherein said working gaps are disposed opposite each other, said hydraulic valve is a jet-pipe valve, said movable control member is a jet-pipe mounted for pivotal motion, and

said armatures are each mounted on said jet-pipe and constrained thereby for movement normal to said prede- 5 termined direction.

7. The electrohydraulic transducer of claim 6 further including an annular baille disposed about said jet-pipe intermediate said armatures and the free nozzle end of said jet-pipe for hydraulically isolating the regions located 10 on opposite sides of said bafe.

8. The eleetrohydraulic transducer of claim 6 wherein each of said force motors further include bias windings for providing steady state bias uxes in their associated cores having directions which, respectively, are additive and subtractive relative to the iluxes generated in said cores in response to identical control signals input to said control windings, thereby linearizing the relationship between said control signals and the net electrical force applied to said jet-pipe by said armature.

References Cited UNITED STATES PATENTS 2,768,637 10/1956 Sweeney 137-83 2,858,849 11/1958 Grilith 137-83 XR 2,990,839 7/1961 Ray 137-83 XR 3,017,864 l/l962 Atchley 91-3 3,180,346 4/1965 Duif 91-3 XR HENRY T. KLINKSIEK, Primary Examiner U.S. Cl. X.R.