US3749128A

US3749128A - High frequency response servo valve

Info

Publication number: US3749128A
Application number: US00132276A
Authority: US
Inventors: D Sallberg; P Clark; W Parker; R Nicholson
Original assignee: Koehring Co
Current assignee: Schenck Pegasus Corp
Priority date: 1971-04-08
Filing date: 1971-04-08
Publication date: 1973-07-31
Anticipated expiration: 1990-07-31

Abstract

Metering means for hydraulic fluid including a metering sleeve and a spool valve within the sleeve movable to meter fluid through the sleeve in accordance with the position of diaphragm springs engaged therewith at the opposite ends thereof, a voice coil connected to one of the diaphragm springs and means for creating a permanent magnetic field about the coil whereby high frequency movement of the voice coil and therefore the spool valve is effected by varying the electric signal in the coil.

Description

United States Patent 1191 Sallberg et al.

HIGH FREQUENCY RESPONSE SERVO VALVE Inventors: David W. Sallberg jarrning t ori;

Peter 1. Clark, Troy; Wesley R. Parker; Robert D. Nicholson, both of Birmingham. all of Mich.

Assignee: Koehring Company, Milwaukee,

Wis.

Filed: Apr. 8, 1971 Appl. No.2 132,276

US. Cl. 137/625.6l, l37/625.65 Int. Cl. Fl6k 31/10, F15b 11/08 Field of Search 137/625.65, 596.17,

References Cited UNITED STATES PATENTS 7/1969 Andrews 137/625.61 9/1969 Boonshaft et aI 137/625.65 X 12/1951 Best 251/137 X 9/1960 Reen et al.....

1451 July31,1973

3,099,230 7 1963 Holzbock 137/83 3,001,549 9/1961 Nelson et a1... 137/625.27 2,582,088 1/1952 Walthers 137 501 x 2.669247 2/ 1954 Olah 137/84 FOREIGN PATENTS OR APPLICATIONS 196,517 6/1965 Sweden l37/625.64 1,197,897 7 1970 Great Britain 137/625.65

Primary Examiner-Henry T. Klinksiek Assistant Examiner-Robert J. Miller Attorney-Whittemore, I-Iulbert & Belknap [5 7 ABSTRACT 11 Claims, 3 Drawing Figures 52 54 12 Z 10 f 1 28 us 2s 4s f 88 g g 120 5s fig; 1 22 1043 24 122 1' so 102 94 r 32 7o} '72 18 I 76 I 46 I HIGH FREQUENCY RESPONSE SERVO VALVE BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to electrohydraulic servo valves and refers more specifically to a high frequency responsive electrohydraulic servo valve of the spool type wherein a voice coil movable in a permanent magnetic field is the motor means.

2. Description of the Prior Art In the past, electrohydraulic servo valves have often included a metering spool carrying centrally located opposed jets and a flapper valve positioned between the jets causing movement of the metering spool in accordance with the position of the flapper valve with respect to the jets. With such valves the motor means has usually been an electromagnet operable on the end of the flapper valve opposite the jets for pivoting the flapper valve about a pivot point produced by a torsion tube or the like. With such valve structure the frequency of response is limited due to the physical characteristics of the motor means, flapper valve and pivot structure and the response of the metering spool to the variation in pressures at the jets. High frequency response of such valves is not to be expected.

SUMMARY OF THE INVENTION In accordance with the invention, a high frequency response electrohydraulic servo valve is provided comprising metering'means including a metering sleeve and a spool valve movable axially within the sleeve, means for positioning the spool valve axially including a diaphragm spring at each end of the spool and engaged therewith, an adjustment screw between at least one diaphragm spring and the spool, and motor means for moving one of the diaphragm springs and therefore the spool at a relatively high frequency including a voice coil connected to the one diaphragm spring and means for producing a permanent magnetic field about the voice coil.

The diaphragm springs have openings extending therethrough and the motor means includes openings therethrough whereby the hydraulic pressures are equalized on the opposite sides of the diaphragm springs and in the motor means to facilitate the high frequency operation and provide a substantially completely wet electrohydraulic servo valve.

BRIEF DESCRIPTION OF THE DRAWINGS F IG. 1 is a longitudinal section view of an electrohydraulic servo valve constructed in accordance with the invention and taken substantially on the line ll in FIG. 2.

FIG. 2 is a cross section view of the electrohydraulic servo valve illustrated in FIG. I taken substantially on the line 22 in FIG. 1.

FIG. 3 is a partial cross section view of the electrohydraulic servo valve illustrated in FIG. 1 taken substantially on the line 3-3 in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The electrohydraulic servo valve as illustrated in FIGS. 1-3 includes the metering means 12 including metering sleeve 14 and metering spool 16 therein. Resilient diaphragm means 18 and 20 are provided at the opposite ends of the metering spool 16 for maintaining the metering spool 16 in a predetermined adjusted position within the sleeve 14. Motor means 22 is connected to the resilient means 20 for moving the metering spool 16 at a high frequency in accordance with an electrical signal passed through the voice coil 24 of the motor means.

More specifically, the metering means 12 includes a valve body 28 having a central passage 30 extending therethrough with metering annuluses 32 therein.

Passages

34 and 36 extend transversely through the valve body 28 and may be connected directly to a member such as a hydraulic cylinder (not shown) which it is desired to actuate in accordance with the fluid flow through the valve 10. Hydraulic fluid enters the valve 10 through the passage 38 therein and leaves the valve 10 to a sump or the like through the

passages

40 and 42.

Additional passages

44 and 46 are provided in the valve body 28 which are returned to the hydraulic fluid supply which may be the same supply to which the passage 42 is connected whereby the hydraulic pressure at the opposite ends of the valve 10 is equalized.

Annular recesses

48 and 50 are provided at the opposite ends of the body 28 to receive the resilient diaphragm means 18 and 20.

The metering means 12 further includes the end plate 52 secured to the end 54 of the body 28 by convenient means such as bolts 56 or the like. Plug 58 is provided in the end plate 52 and may be removed in use to permit adjustment of the adjusting screw 60 carried by the resilient diaphragm means 18.

The metering sleeve 14 is securely held in the passage 30 in the body member 28 by means of the annular nuts 62 and 64 at the opposite ends thereof. The metering sleeve 14, as shown, has annular sealing lands 66 thereon between which annular metering grooves 68 are provided in alignment with the metering annuluses 32 in the body 28.

Transverse openings

70, 711, 72, 73 and 74 are provided in the metering sleeve to meter fluid therethrough in conjunction with the metering spool 16.

Metering spool 16, as shown, has the three

metering lands

76, 78 and 80 thereon which are operable in conjunction with the metering sleeve 14 to meter fluid through the

passages

34, 36, 38 and 42 of the body 28.

Thus, on movement of the metering spool 16 to the left as shown in FIG. 1, hydraulic fluid will be metered through passage 38, passage 74 and passage 72 into the passage 36. At the same time, hydraulic fluid will be metered from the passage 34 through the passage 70, out through the passage 71 and through passage 40, passage 73 and passage 42. On movement of the spool valve 16 to the right, fluid is passed from the passage 38 into the passage 34 and at the same time hydraulic fluid is passed out through the passage 36 and passage 42.

The resilient diaphragm means 18 includes a diaphragm spring 86 which is secured around the periphery thereof in the recess 48 in body 28 by the annular nut 88. The diaphragm spring 86 has a central opening 90 extending therethrough through which the boss 92 extends. Boss 92 is secured to the diaphragm spring 86 by nut 94. The adjusting screw 60 is threaded through the boss 92. Both the adjusting screw 60 and the adjacent end of the metering spool 16 are provided with a conical recess therein to receive the conical ends of the force transfer member 96. As shown best in FIG. 2, the diaphragm spring 86 has openings 98 therethrough to equalize the pressure on the opposite sides of the diaphragm spring 86.

The resilient means at the opposite end of the metering spool 16 is the same as the resilient means 18, with the exception of the adjusting screw 60 which is not present in the resilient means 20. lnstead of the adjusting screw 60, a screw 100 extends through the boss of the resilient means 20 to which the trough 102 of the motor means 26 is secured by nut 106.

The motor means 22 includes the voice coil 24 carried by trough 102 which, as shown best in FIG. 3, has openings 108 therethrough to equalize the pressure on the opposite sides thereof. The permanent magnetic field of the motor means 22 is provided by the cylindrical permanent magnet 26. The permanent magnetic field from the magnet 26 is directed through the voice coil 24 by means of the soft

magnetic material members

110 and 112 positioned as shown. The permanent magnet 26 and the

members

110 and 112 are maintained in a predetermined position by the motor means cover plate 114 which may be secured to the body member 28 by convenient means such as bolts (not shown) in conjunction with the

spacers

116 and 118 and the annular spring 120.

In operation, the voice coil 24 is movable relative to the

members

110 and 112 in accordance with the electrical signal passed therethrough, since movement of the coil will be produced in accordance with the electrical signal in the voice coil and the magnetic field provided by the permanent magnet 26.

Openings

122 and 124 are provided in the member 110 to permit equalizing of the pressure in the space 126 between the

members

110 and 112 and the permanent magnet 26.

In operation of the high frequency response electrohydraulic servo valve, a hydraulic fluid input under pressure is connected to the passage 38, the

passages

34 and 36 are connected to a device it is desired to actuate in accordance with a high frequency electrical signal, and the

passages

42 and 46 are connected to the return line of the source of hydraulic fluid under pressure. The opposite ends of the voice coil 24 are connected to a source of high frequency electrical energy. The initial position of the metering spool 16 is adjusted by means of the adjusting screw 60.

Due to the high frequency electrical signal, the voice coil 24 is caused to move axially of the metering spool 16 at a corresponding frequency. Movement of the voice coil 24 causes movement of the resilient diaphragm spring in the resilient means 20 so that the metering spool 16 is moved similarly due to the force transfer members between the resilient means 18 and 20 and the metering spool 16. Since the pressure on the opposite sides of the resilient means 18 and 20 and the pressure on the opposite sides of the voice coil 24 are all equalized, rapid response of the metering spool 16 to a high frequency electrical signal which may be pro grammed or varied as desired is providedv While one embodiment of the present invention has been described in detail. it will be understood that other embodiments and modifications thereof are contemplated. It is the intention to include all modifications and embodiments of the invention as are defined by the appended claims within the scope of the invention.

What I claim as my invention is:

1. An electrohydraulic servo valve comprising a valve body having an elongated opening therethrough and including passages extending therein transversely of the opening therethrough through which hydraulic fluid is metered, a metering sleeve positioned within the opening through the valve body member having transverse openings therein through which hydraulic fluid is metered into and out of the passages, an elongated spool valve positioned within the metering sleeve for axial movement therein to meter the hydraulic fluid through the openings in the sleeve into and out of the passages, diaphragm biasing means positioned over the opposite ends of the opening through the valve body and supported by the valve body, separate force transfer members positioned between each diaphragm biasing means and a corresponding end of the spool valve without being connected to either the spool valve or biasing means to transfer only compressive forces therein between the spool and biasing means for moving the spool valve within the metering sleeve in accordance with the movement of the diaphragm biasing means, means for adjusting the initial compressive forces in the force transfer members, a voice coil secured to at least one of the diaphragm biasing means for movement therewith, permanent magnet means carried by the valve body positioned adjacent the voice coil for causing movement of the voice coil in accordance with an electrical signal passed through the voice coil, and means for equalizing the hydraulic pressure on both sides of the diaphragm biasing means and the voice coil.

2. Structure as set forth in claim 1 wherein the diaphragm biasing means are perforate to provide passage of hydraulic fluid therethrough and means are provided in the valve body for connecting the hydraulic fluid adjacent both of the diaphragm biasing means.

3. Structure as set forth in claim 1 wherein the permanent magnet means includes a cylindrical permanent magnet positioned concentrically of and positioned axially and radially outwardly of the voice coil, a soft iron core having a T-shaped longitudinal cross section the stem of which is positioned within the voice coil and the crossbar of which is engaged with one end of the cylindrical permanent magnet and a cylindrical soft' iron member positioned radially outwardly of and concentric with the voice coil one end of which is in engagement with the other end of the cylindrical pennanent magnet whereby the soft iron members and the cylindrical permanent magnet define a cylindrical chamber at one end of the voice coil, and passages in the stern of the one soft iron core providing communication between the other end of the voice coil and the cylindrical chamber at the one end of the voice coil whereby hydraulic fluid pressure is equalized on both ends of the voice coil.

4. Structure as set forth in claim 1 wherein the means for adjusting the initial compressive forces in the force transfer members comprises an adjusting screw carried by each of the diaphragm biasing means centrally thereof in engagement with the separate force transfer members.

5. An electrohydraulic servo valve comprising a valve body having an elongated opening therethrough and including passages therein transversely of the opening therethrough through which hydraulic fluid is metered, an elongated spool valve positioned within the opening for axial movement therein to meter the hydraulic fluid through the opening in the valve body into and out of the passages, diaphragm biasing means positioned over the opposite ends of the opening through the valve body and supported by the valve body, separate force transfer members positioned between each diaphragm biasing means and a corresponding end of the spool valve without being connected to either the spool valve or diaphragm biasing means to transfer only compressive forces therein between the spool valve and diaphragm biasing means for moving the spool valve within the opening in accordance with the movement of the diaphragm biasing means, means carried by the diaphragm biasing means and operable between the diaphragm biasing means and force transfer members for adjusting the initial bias between the diaphragm biasing means and spool valve, a voice coil secured to at least one of the diaphragm biasing means for movement therewith, permanent magnet means carried by the valve body positioned adjacent the voice coil for causing movement of the voice coil in accordance with an electrical signal passed through the voice coil, and means operably associated with the diaphragm biasing means and voice coil for equalizing the hydraulic pressure on both sides of the diaphragm biasing means and the voice coil. 7

6. Structure as set forth in claim 5, wherein the means for equalizing the hydraulic pressure on both sides of the diaphragm biasing means includes openings through the diaphragm biasing means and a passage in the valve body member for connecting hydraulic fluid adjacent both of the diaphragm biasing means.

7. Structure as set forth in claim 5, wherein the permanent magnet means includes a cylindrical permanent magnet positioned concentrically of and both axi ally and radially outwardly of the voice coil with respect to the spool valve, a soft iron core having a T- shaped longitudinal cross section the stem of which is positioned within the voice coil and the cross bar of which is engaged with one end of the cylindrical permanent magnet and a cylindrical soft iron member positioned radially outwardly of and concentric with the voice coil one end of which is in engagement with the other end of the cylindrical permanent magnet whereby the soft iron members and the cylindrical permanent magnet define a cylindrical chamber at one end of the voice coil and wherein the means for equalizing the hydraulic pressure on both sides of the voice coil includes passages in the stern of the one soft iron core providing communication between the other end of the voice coil and the cylindrical chamber at the one end of the voice coil.

8. Structure as set forth in claim 5, wherein the means for adjusting the initial bias between the spool valve and the diaphragm biasing means comprises adjusting screws carried by the diaphragm biasing means centrally thereof for movement transversely of the diaphragm biasing means in engagement with the ends of the force transfer members.

9. Structure as set forth in claim 8 and further including an opening in the valve body member adjacent one adjusting screw and plug means threadedly secured within the opening whereby the bias between the diaphragm biasing means and the spool may be adjusted on removal of the plug without further disassembly of the electrohydraulic servo valve.

10. An electrohydraulic servo valve comprising a cylindrical valve body member, a cylindrical opening extending axially through the valve body member, transverse passages passing through the valve body member in communication with the axial opening therethrough, a metering sleeve positioned in the opening for metering fluid between the transverse passages, a spool valve positioned within the metering sleeve for reciprocation therein to meter fluid into and out of the passages through the metering sleeve, circular perforate diaphragm biasing means secured to the opposite ends of the valve body member over the opening therein, a passage in the valve body member connecting the areas surrounding the diaphragm biasing means for equalizing hydraulic fluid pressure therein, an adjusting screw threadably received centrally of one of the biasing diaphragms, a second adjusting screw and a voice coil threadably received in and carried centrally of the other of said biasing diaphragms, separate force transfer members positioned between the opposite ends of the spool valve and the associated adjusting screws which are not secured to either the spool valve or adjusting screws so as to transfer only compressive forces therein between the biasing diaphragms and spool valve whereby the bias on the spool valve may be adjusted on adjustment of the adjusting screws, a valve body cap positioned over one end of the valve body member adjacent the one biasing diaphragm, and permanent magnet motor means positioned over the other end of the valve body member operably associated with the voice coil for movement of the voice coil and thus the spool valve in accordance with the electrical energy passed through the voice coil.

11. Structure as set forth in claim 10 wherein the permanent magnet motor means includes a cylindrical permanent magnet positioned concentrically of and both axially and radially outwardly of the voice coil with respect to the spool valve, a soft iron core having a T- shaped longitudinal cross section the stem of which is positioned within the voice coil and the crossbar of which is engaged with one end of the cylindrical permanent magnet and a cylindrical soft iron member positioned radially outwardly and concentrically of the voice coil one end of which is in engagement with the other end of the cylindrical permanent magnet whereby the soft iron members and the cylindrical permanent magnet define a cylindrical chamber at one end of the voice coil, and passages in the stem of the one soft iron core providing communication between the other end of the voice coil and the cylindrical chamber at the one end of the voice coil whereby hydraulic fluid pressure is equalized on both ends of the voice coil.

* t I I

Claims

3. Structure as set forth in claim 1 wherein the permanent magnet means includes a cylindrical permanent magnet positioned concentrically of and positioned axially and radially outwardly of the voice coil, a soft iron core having a T-shaped longitudinal cross section the stem of which is positioned within the voice coil and the crossbar of which is engaged with one end of the cylindrical permanent magnet and a cylindrical soft iron member positioned radially outwardly of and concentric with the voice coil one end of which is in engagement with the other end of the cylindrical permanent magnet whereby the soft iron members and the cylindrical permanent magnet define a cylindrical chamber at one end of the voice coil, and passages in the stem of the one soft iron core providing communication between the other end of the voice coil and the cylindrical chamber at the one end of the voice coil whereby hydraulic fluid pressure is equalized on both ends of the voice coil.

5. An electrohydraulic servo valve comprising a valve body having an elongated opening therethrough and including passages therein transversely of the opening therethrough through which hydraulic fluid is metered, an elongated spool valve positioned within the opening for axial movement therein to meter the hydraulic fluid through the opening in the valve body into and out of the passages, diaphragm biasing means positioned over the opposite ends of the opening through the valve body and supported by the valve body, separate force transfer members positioned between each diaphragm biasing means and a corresponding end of the spool valve without being connected to either the spool valve or diaphragm biasing means to transfer only compressive forces therein between the spool valve and diaphragm biasing means for moving the spool valve within the opening in accordance with the movement of the diaphragm biasing means, means carried by the diaphragm biasing means and operable between the diaphragm biasing means and force transfer members for adjusting the initial bias between the diaphragm biasing means and spool valve, a voice coil secured to at least one of the diaphragm biasing means for movement therewith, permanent magnet means carried by the valve body positioned adjacent the voice coil for causing movement of the voice coil in accordance with an electrical signal passed through the voice coil, and means operably associated with the diaphragm biasing means and voice coil for equalizing the hydraulic pressure on both sides of the diaphragm biasing means and the voice coil.

7. Structure as set forth in claim 5, wherein the permanent magnet means includes a cylindrical permanent magnet positioned concentrically of and both axially and radially outwardly of the voice coil with respect to the spool valve, a soft iron core having a T-shaped longitudinal cross section the stem of which is positioned within the voice coil and the cross bar of which is engaged with one end of the cylindrical permanent magnet and a cylindrical soft iron member positioned radially outwardly of and concentric with the voice coil one end of which is in engagement with the other end of the cylindrical permanent magnet whereby the soft iron members and the cylindrical permanent magnet define a cylindrical chamber at one end of the voice coil and wherein the means for equalizing the hydraulic pressure on both sides of the voice coil includes passages in the stem of the one soft iron core providing communication between the other end of the voice coil and the cylindrical chamber at the one end of the voice coil.

11. Structure as set forth in claim 10 wherein the permanent magnet motor means includes a cylindrical permanent magnet positioned concentrically of and both axially and radially outwardly of the voice coil with respect to the spool valve, a soft iron core having a T-shaped longitudinal cross section the stem of which is positioned within the voice coil and the crossbar of which is engaged with one end of the cylindrical permanent magnet and a cylindrical soft iron member positIoned radially outwardly and concentrically of the voice coil one end of which is in engagement with the other end of the cylindrical permanent magnet whereby the soft iron members and the cylindrical permanent magnet define a cylindrical chamber at one end of the voice coil, and passages in the stem of the one soft iron core providing communication between the other end of the voice coil and the cylindrical chamber at the one end of the voice coil whereby hydraulic fluid pressure is equalized on both ends of the voice coil.