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Publication numberUS3585547 A
Publication typeGrant
Publication dateJun 15, 1971
Filing dateJul 15, 1969
Priority dateJul 15, 1969
Publication numberUS 3585547 A, US 3585547A, US-A-3585547, US3585547 A, US3585547A
InventorsKassir Abdul R, Sciortino Salvatore A, Sturman Oded E
Original AssigneeBell Aerospace Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Electromagnetic force motors having extended linearity
US 3585547 A
Abstract  available in
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

Umted States Patent [72] Inventors dedE.Sturman [56] Referencescited 2:3} K 88 G b l Sal A UNITED STATES PATENTS u ml n a m Va ore 6 362,135 /1887 w1166n.,.,,... 335/230 21] A No z'fw 2,941,130 6/1960 Fischeletal. 335/236x i z M51969 3,154,723 /1964 BOl'dehel 335/227x t d J nfls'ml 3,435,393 3/1969 MeiSel 335/237 lig 1 cmnm R'E.26;749 1/1970 Montagu 335/229 [54] ELECTROMAGNETIC FORCE MOTORS HAVING Primary Examiner-G. Harris Attorney-Nilsson and Robbins ELECTROMAGNETIC FORCE MOTORS HAVING EXTENDED LINEARITY BACKGROUND OF THE INVENTION 1. Field of the Invention The field of art to which the invention pertains includes the field of torque motors.

2. Description of the Prior Art The use of force motors in the prior art has long been known. One example of the utility of force motors is in the positioning of the pilot valve such as a flapper or spool of an hydraulic servo valve. The force motor in such applications is used as an element of a control system and is adapted by its operating characteristics to convert an electrical input signal into a desired mechanical position of the spool valve. Force motors also have a wide variety of other uses, for example, in automatic control systems for industrial machinery.

Such force motors which utilize a large percentage of the airgap for armature motion are typically faced with nonlinearity over all but a small part of the airgap. In various of the prior art applications it has long been desirable to provide force motors which bear a linear relationship to the applied input signal and wherein the force exerted upon the armature remains substantially linear as it approaches the pole faces. This would permit displacement of the armature over the entire gap.

A variety of schemes have been proposed to accomplish such linearization, forexample, reducing the effective length of the cross-sectional area of a part of the armature and keeping that portionalways saturated magnetically, as illustrated in the U.S. Pat. No. 3,07l,l74.Another linearization scheme provides recesses on the face of the armature and a plurality of mating teeth on the face of the pole pieces, for example, as shown in U.S. Pat. No. 2,930,945.

Each of the foregoing devices attempts to utilize magnetic saturation to obtain linearization by carefully formulating the configuration of the magnetically permeable material that defines the flux path. Although each of these devices operate for the purpose intended, problems sometimes arise in manufacturing to the close tolerances required to obtain acceptable devices. There is a need, therefore, for a simple means for attaining magnetic saturation appropriate to the linearization of the force versus input signal characteristic of the force motor.

SUMMARY OF THE INVENTION The present invention provides an improvement in electromagnetic force motors in which linearity of the force versus input signal characteristic is extended. A motor is provided of the electromagnetic force type, that is, having a pair of pole pieces spaced apart by frame members to provide an airgap therebetween, an armature within the airgap and permanent magnet means defining a magnetic circuit. The improvement of this invention comprises providing at least one discrete member of magnetically saturable material between the frame member and permanent magnet means and having an induction/magnetic force characteristic different from the induction/magnetic force characteristic of the frame member. Polarizing flux from the permanent magnet, is sufficient to magnetically saturate the discrete member, but would be insufiicient to magnetically saturate that member if constituted of the frame material. In particular embodiments, a plurality of magnetically saturable discrete members is provided to completely separate the frame members from the permanent magnets. The present invention is an improvement over the invention disclosed in U.S. Pat. No. 3,517,360.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic, cross-sectional view of an electromagnetic force motor utilizing the present invention; and

FIG. 2 is a cross-sectional view of the apparatus illustrated in FIG. 1, taken online 2-2 of FIG. I, in the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the FlGS. there is illustrated in schematic manner an electromagnetic force motor constructed in'accordance with the present invention. The force motor includes frame members 10 and 12 which are formed to define oppositely disposed pairs of pole pieces l4, l6 and 18, 20. An armature 22 is supported about a pivot point 24 between the pole pieces. Although not shown in the schematic drawing herein, the armature can support a flapper so as to serve as the first stage of a control valve, all as well known to the art. Further, a coil 25 is positioned about the armature 22 and is adapted to receive an electrical input signal which thereby causes the armature to take a physical position, displaced from the Null position (illustrated), depending upon the strength of the applied input signal and the polarity thereof.

In prior art torque motors, a pair of permanent magnets would be secured between the frame members, directly contacting the frame members. In the present invention, permanent magnets 26 and 28 are also affixed to the frame members l0 and 12, so as to bridge the frame members and provide magnetic flux for the torque motor. However, in the present invention the permanent magnets 26 and 28 are separated from the frame members 10 and, 12 by means of inserts 30,. 32, 34 and 36, as hereinafter described. The inserts and permanent magnets are secured between the edges of the frame members 10 and 12 by means of machine screws 38 and nuts 40 therefor extending through the edges of the frame members, as shown in the drawings.

The inserts 30, 32, 34 and 36 are of magnetically permeable material having a predetermined induction/magnetic force characteristic which is different from the induction/magnetic force characteristic of the material of which the frame members l0 and 12 are constituted. The induction/magnetic force characteristic of each of the inserts 30, 32, 34 and 36 is such that the magnetic flux from the permanent magnet 10 and 12 is sufficient to magnetically saturate the inserts at a preselected armature 22 position within the airgap between the poles 14, 16 and I8, 20, but is insufficient at that armature position for magnetic saturation if the inserts were constructed of the same material as the frame members 10 and 12. In other words, the inserts 30, 32, 34 and 36 are constructed of material which passes its maximum magnetic induction at a particular position of the armature 22 in the air-,

gap displaced from its Null position.

With prior art torque motors, as the armature approaches one of the pole faces, the reluctance due to the gap decreases, resulting in an increase in flux from the permanent magnet, which increase is proportional to the square of the armature displacement. At the same time, a linearly increased amount of such nonlinear flux passes through the gap. The total result is a flux increase that is nonlinear with respect to armature displacement. However, when the present invention is utilized, as a result of saturation of the inserts 30, 32, 34 and 36, a decrease in reluctance does not effect an increase in flux. Since the gap is decreasing in length the number of flux lines passing therethrough does increase; however, this increase is in linear proportion to such decreasing gap length, i.e., in

. linear proportion to armature displacement.

What we claim is:

1. In an electromagnetic force motor having a pair of pole pieces spaced apart to provide an airgap therebetween;

an armature positioned with a portion thereof in said airgap,

said armaturebeing adapted to move in said airgap from a null position thereof thereby more closely approaching one of said pole pieces;

a magnetic circuit in said motor including said pole pieces and said armature and including permanent magnetic means for providing polarizing flux and a frame member securing said pole pieces to said permanent magnet means;

electrical signal receiving means disposed on said magnetic circuit to establish magnetic flux therein of a strength proportional to a received electrical signal;

the improvement of apparatus for extending the linearity of the force versus input signal characteristic of said force motor, comprising: I at least one discrete member of magnetically saturable material disposed between said frame member and said permanent magnetic means and having an induction/magnetic force characteristic different from the induction/magnetic force characteristic of said frame member so as to define a magnetic saturation path thereat; said permanent magnet polarizing flux being sufficient to magnetically saturate said discrete member at a preselected armature position other than its null position within said airgap but being insufficient, at said preselected armature position to magnetically saturate frame member material of the same configuration as said discrete member.

2. The invention as defined in claim 1 in which said frame member is formed integral with said pole pieces.

3. The invention as defined in claim 1 wherein a plurality of said discrete members are disposed between said frame member and said permanent magnetic means. i

4. The invention as defined in claim 3 wherein each of said discrete members has the same induction/magnetic force characteristic.

5. The invention as defined in claim 3 wherein said discrete members completely separate said frame member from said permanent magnetic means.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3585547 Dated June 1 lnventor(s) Oded E Sturman et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 33, "3,071,174" should read 3,071,714

Signed and sealed this 11th day of April 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCI-IALK Attesting Officer Commissioner of Patents FORM PO-1050 [10-69) USCOMM-DC wan-Pan US. GOVERNMENY PRINT NG QFFICE I911 0-306-834

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3673529 *May 13, 1971Jun 27, 1972Babcock Electronics CorpMagnetic actuator
US3950718 *Nov 26, 1974Apr 13, 1976Matsushita Electric Works, Ltd.Electromagnetic device
US4467304 *Dec 28, 1982Aug 21, 1984Minnesota Mining And Manfacturing CompanySaturable tandem coil transformer relay
US5407131 *Jan 25, 1994Apr 18, 1995Caterpillar Inc.Fuel injection control valve
US5421521 *Aug 12, 1994Jun 6, 1995Caterpillar Inc.Fuel injection nozzle having a force-balanced check
US5449119 *May 25, 1994Sep 12, 1995Caterpillar Inc.Magnetically adjustable valve adapted for a fuel injector
US5474234 *Mar 22, 1994Dec 12, 1995Caterpillar Inc.Electrically controlled fluid control valve of a fuel injector system
US5479901 *Jun 27, 1994Jan 2, 1996Caterpillar Inc.Electro-hydraulic spool control valve assembly adapted for a fuel injector
US5488340 *May 20, 1994Jan 30, 1996Caterpillar Inc.Hard magnetic valve actuator adapted for a fuel injector
US5494219 *Jun 2, 1994Feb 27, 1996Caterpillar Inc.Fuel injection control valve with dual solenoids
US5494220 *Aug 8, 1994Feb 27, 1996Caterpillar Inc.Fuel injector assembly with pressure-equalized valve seat
US5597118 *May 26, 1995Jan 28, 1997Caterpillar Inc.Direct-operated spool valve for a fuel injector
US5605289 *Dec 2, 1994Feb 25, 1997Caterpillar Inc.Fuel injector with spring-biased control valve
US5628293 *Aug 31, 1995May 13, 1997Caterpillar Inc.Electronically-controlled fluid injector system having pre-injection pressurizable fluid storage chamber and direct-operated check
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US5720318 *May 26, 1995Feb 24, 1998Caterpillar Inc.Solenoid actuated miniservo spool valve
US5738075 *May 28, 1997Apr 14, 1998Caterpillar Inc.Hydraulically-actuated fuel injector with direct control needle valve
US5752308 *Jul 3, 1995May 19, 1998Caterpillar Inc.Method of forming a hard magnetic valve actuator
US5758626 *Oct 5, 1995Jun 2, 1998Caterpillar Inc.Magnetically adjustable valve adapted for a fuel injector
US6085991 *May 14, 1998Jul 11, 2000Sturman; Oded E.Intensified fuel injector having a lateral drain passage
US6148778 *May 14, 1998Nov 21, 2000Sturman Industries, Inc.Air-fuel module adapted for an internal combustion engine
US6161770 *May 4, 1998Dec 19, 2000Sturman; Oded E.Hydraulically driven springless fuel injector
US6173685Mar 22, 2000Jan 16, 2001Oded E. SturmanAir-fuel module adapted for an internal combustion engine
US6257499Jul 17, 2000Jul 10, 2001Oded E. SturmanHigh speed fuel injector
US6575137Jun 11, 2002Jun 10, 2003Caterpillar IncPiston and barrel assembly with stepped top and hydraulically-actuated fuel injector utilizing same
EP0085535A1 *Jan 26, 1983Aug 10, 1983DEERE & COMPANYSolenoid
EP0214911A1 *Sep 4, 1986Mar 18, 1987S.A.M.M.- Société d'Applications des Machines MotricesTorque motor with a hydraulic potentiometer for a servo distributor
U.S. Classification335/227, 335/236, 335/230
International ClassificationH01F7/14, H01F7/08
Cooperative ClassificationH01F7/14
European ClassificationH01F7/14
Legal Events
Mar 4, 1982ASAssignment
Effective date: 19820222