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(19)Europaisches PatentamtEuropean Patent OfficeOffice europeen des brevets

(12)peen des brevets E P 0 7 2 7 8 6 8 B 1EUROPEAN PATENT SPECI FICAT ION

(45) Date of publication and mentionof the grant of the patent:22.12.1999 Bulletin 1999/51(21) Application number: 96102064.1(22) Date of filing: 13.02.1996

(51) Intel e H02K 26/00

(54) Torque motors with enhanced reliabilityDrehmomentmotor mit erhohter ZuverlassigkeitMoteur couple a fiabilite renforcee

(84) Designated Contracting States:DE FR GB(30) Priority: 15.02.1995 US 389141(43) Date of publication of application:21.08.1996 Bulletin 1996/34(73) Proprietor: J.H. BUSCHER, INC.Orchard Park, New York 14127 (US)(72) Inventors: Buscher, John H.East Amherst, New York 14051 (US)

DO00CO00CMIs-oa .LU

Bronke, Henry R.Colden, New York 14033 (US) Ernewein, Mark P.Hamburg, New York 14075 (US)(74) Representative: Fechner, Joachim, Dr.-lng.Im Broeltal 11853773 Hennef (DE)(56) References cited:WO-A-87/06051US-A-3 381 150US-A- 3 938 778

US-A-2 891 181US-A- 3 415 283

Note: Within nine months from the publication of the mention of the grant of the European patent, any person may givenotice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed ina written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art.99(1) European Patent Convention).

Printed byJouve, 75001 PARIS(FR)

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1 EP 0 727 868 B1 2DescriptionTECHNICAL FIELD[0001] This invention relates generally to electromag- snetic actuators, and more specifically, to improvedtorque motors, methods of assembly and applicationstherefor, such as in aviation where standards of motorreliability and performance are necessarily very high de-spite external vibration and temperature cycles being 10quite extreme.BACKGROUND OF THE INVENTION[0002] Torque motors may be characterized as actu- 15ators which are suitable for moving through displace-ments in the order of + 0. 127 mm (+0,005 inches), haveadjustable positional stiffness, move proportionally un-der command of an electrical signal, and do so repeat-edly regardless of signal polarity, for increasing or de- 20creasing signal amplitude.[0003] Typically, torque motors are constructed froma pair of pole pieces, an armature, flexural or pivotingmeans to locate the armature within the torque motorstructure, one or more coils, at least one magnet, and a 25motor housing. Such motors are useful in operatingvalves in controlling fluid flow; operating springs, clutch-es, braking systems; focusing lenses; in machine tools;industrial controls, to name but a few. In aviation appli-cations torque motors can be used in jet engines, for 30instance, in controlling fluid flow, in operating hydraulicsystems, and so on.[0004] In several of the foregoing applications, torquemotors are required to perform critical control opera-tions, such as actuators for servovalves for controlling 35fuel flow to jet aircraft engines. The environmental con-ditions under which such torque motors frequently op-erate can be very severe. Repetitive extreme tempera-ture cycles, and particularly, vibration generated by air-craft engines are common problems. Resistance to vi- 40bration is of great importance for such applications, bothfrom the standpoint of avoiding damage to the torquemotor, and the effect of vibration on motor performanceand reliability.[0005] In an effort to overcome the problem of exter- 45nal vibration manufacturers of torque motors, such asServotronics, Inc.; Moog, Inc., and HSC Controls haveutilized various techniques. For example, one methodhas been to loosely assemble the components of torquemotors, and employ a potting process of filling spaces sobetween coils and magnets and motor housing with cur-able polymeric fillers, such as epoxy resin, as disclosedby U.S. Patent No. 3,639,871 . While the potting methodis capable of imparting increased rigidity to the internalcomponents of the motor, this method has several dis- 55advantages. For one, it fails to provide desired levels ofrigidity of motor components relative to the motor hous-ing. Torque motors having aircraft applications must al-

so meet critical reliability indices. The problem is, it isdifficult to inspect or test the epoxy bond to motor struc-ture to determine if components imbedded in the poly-meric matrix meet the required higher reliability stand-ards associated with aviation applications. Moreover,the thermal coefficient of expansion of the polymer isusually different from that of the structure of the torquemotor, and Young's modulus of epoxy resins is smallcompared to that of motor components.[0006] Other problems are of an environmental andeconomic nature. For instance, use of adhesive resin-ous fillers require careful degreasing of bond surfaceson motor components. The prescribed method is bycleaning components with chlorofluorocarbon solvents.However, when used CFCs become discharged into theatmosphere, are broken down by sunlight to releasechlorine into the stratosphere, which in-turn has a cata-lytic and destructive effect on the global ozone shield.This increases the amount of harmful ultraviolet radia-tion reaching Earth's surface. Hence, as part of the na-tional and global strategies, use of most CFCs has beencurtailed. In fact, customer purchase orders for torquemotors frequently specify that manufacturers meet allsuch environmental regulations, which means eliminat-ing the use of CFCs during assembly. Finally, the appli-cation of polymeric fillers between component parts isa slow and inefficient process, and economically unat-tractive.[0007] Still, several manufacturers sandwich perma-nent magnets between pole pieces using threaded fas-teners to clamp components together. While the result-ing structure can be stiff this method fails to impart ad-equate structural damping and resistance to resonantmotion of the motor structure when it is subject to vibra-tion at or near the resonant frequency of the torque mo-tor structure. The amplitude of this movement can bevery large and will result in mechanical damage to motorcomponents. This is believed to be due to the lack offriction damping between component parts. Resonanceand concomitant wearing of parts due to relative motionbetween components will generate unwanted magneticdust-like particles which accumulate in air gaps betweenthe armature and pole pieces, which eventually leads tomotor failure by limiting motion of the armature.[0008] Others in the field have employed variousmethods for controlling vibration, including a combina-tion of threaded fasteners and polymeric filler/binder toimprove rigidity. In this method, the actuator assemblyis first bolted and then filled with a curable epoxy resinapplied to support the coil in the middle of the boltedassembly. Afurther method is to rely on protuberanceson the coils made from a flexible potting compound. Theprotuberances become compressed between structuralcomponents of the assembly under forces generated bythreaded screws. This method does not perform well be-cause the applied forces are sufficient to cause distor-tion of actuator parts, including distortion during heating/cooling cycles. Eventually, the interference effect of the

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3 EP 0 727 868 B1 4protuberances is reduced due to repeated thermal cy-cles.[0009] Still other manufacturers have used methodsfor reducing susceptibility to external vibration by meansof a rigid cast stainless steel tubular type housing with scoils secured by either close fit or an epoxy resinousfiller and magnets retained by soldering or brazing ontopole tips. This provides an assembly made up of fourmagnets, two at each end. The assembly of two mag-nets and two poles is then welded to the stainless steel 10housing.[0010] U.S. Patent 2,891,181 discloses means forbrazing magnets to pole pieces which, in turn, are weld-ed to the frame of a torque motor. There is, however, nomeans for adjusting the pole piece position, and there- 15fore the airgaps, after the pole is welded in place. U.S.Patent 4,01 7,706 (Moog) discloses a method of machin-ing airgaps to size by electro discharge machining(EDM). This does not allow for adjustable airgaps.[0011] Accordingly, there is need for improved torque 20motors with reduced susceptibility to external vibrationwhile also maximizing structural damping for greater re-liability and motor life expectancy. In addition, there isneed for improved methods of assembling torque mo-tors without polymeric fillers, potting techniques, assem- 25bly bolting or combinations thereof which impart addedstiffness, and sufficient damping to prevent large ampli-tude relative to motion of the torque motor assembly inthe event of resonant motion. 30SUMMARY OF THE INVENTION[0012] In accordance with the invention more reliabletorque motors are provided with reduced susceptibilityto external vibration while also maximizing structural 35damping. Greater motor dependability is achieved with-out reliance on forming rigid structures by the usual pot-ting techniques using resins and adhesives, bolting fas-teners, and the like. Instead, the inventors have discov-ered that torque motor assemblies can be held rigidly in 40place through frictional forces generated by inwardlycompressive forces produced by an outer generally thinwalled motor housing. Accordingly, the improved motorsare characterized by stiffness, which is extremely high,and a mass that is very low to provide a resonant fre- 45quency above the operating range, typically of jet air-craft engines, i.e., >1 kHz. Should vibrational forces ex-ceed such levels the improved motors have a large re-serve of damping from high clamping forces which re-mains in effect even in the event of some yielding by somotor components.[0013] It is therefore the principal object to provide forimproved, more reliable torque motors generally com-prising first and second flux conducting pole piecesspaced from one another to define air gaps; an armature 55suspended between the pole pieces with ends thereofextending into the air gaps; a motor output shaft meansrigidly affixed to the armature for movement therewith;

electromagnetic coil means positioned about the arma-ture; permanent magnetic means having first and sec-ond sections of opposed polarity disposed on oppositesides of the armature and in engagement with the polepieces; and an outer casing for housing the motor, com-ponents of the motor being held rigidly in place throughfrictional forces from compressive engagement by theouter casing.[001 4] The outer casing or shell for housing the motoris generally rounded, and more specifically, generallycircular or oval shaped, but more preferably cylindricallyshaped wherein the interior wall (ID) or a portion of theinterior wall surface of the casing or shell compressivelyengages with the peripheral edges of motor compo-nents.[0015] It is therefore, still a further object of the inven-tion to provide a torque motor having a press fit connec-tion between the interior wall portion of the outer casing,i.e., ID, and the peripheral edges of motor components.Substantial inwardly directed clamping forces are pro-duced by means of an interference fit between motorcomponents, usually pole pieces, electromagnetic coilsand permanent magnets, through direct and/or indirectengagement by the outer casing. The relatively thinwalled, small diameter tubular construction of the outercasing engaging motor components compresses theminwardly as a result of the interference fit, particularlywhen achieved with the aid of elevations in the casingwall projecting inwardly against the permanent mag-nets. The compressive engagement generated throughthe interference fit bythe generallythin walled outer cas-ing, especially when employed with inwardly directedsurface elevations produces a significantly stronger,more rigid structure on a weight to stiffness basis rela-tive to that achieved when assembled as a solid struc-ture potted with polymeric resins. As an alternative tosurface elevations on the ID of the thin walled outer cas-ing, the magnets may have elevations or outwardly ex-tending bumps for engagement with the ID of the thinwalled outer casing. Hence, the invention as disclosedherein enables elimination of the resin and adhesive fill-ers customarily used heretofore.[0016] It is still a further object to provide torque mo-tors comprising first and second substantially C-shapedpole pieces with terminal end portions of the first polepiece oppositely spaced from terminal end portions ofthe second pole piece to define air gaps therebetween.An armature is suspended between the pole pieces withend portions thereof extending into the air gaps. The ar-mature is supported by a flexural spring suspension toallow angular displacement between the air gaps. Ad-vantageously, the pole pieces and armature have open-ings adjacent to the air gaps keyed for receiving meansfor measuring the width of the gaps, e.g., feeler gaugemeans, and fasteners for setting the width of the airgaps. Motor output shaft means preferably extendstransversely from the armature within a flexible fluid de-livery tube which also provides flexural suspension of

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5 EP 0 727 868 B1 6the armature. Electromagnetic coil means are posi-tioned about the armature for establishing magnetic fluxin the armature of selected polarity and strength. Multi-ple permanent magnets have first and second portionsof opposed polarity with each portion disposed on op-posite sides of the armature and in engagement with thepole pieces. The motor is housed by means of an outercasing having a generally thin walled rounded configu-ration wherein the components of the motor are rigidlyheld in place by clamping forces produced by the outercasing.[0017] While the foregoing torque motor may be gen-erally oval shaped, a cylindrically shaped outer casingwith interior surface elevations is preferred for maximiz-ing rigidity and resistance to vibration through interfer-ence fit with the motor assembly. The improved torquemotors also preferably include useful motor assemblyjig means positioned adjacent to the peripheral edge ofthe motor components and outer casing. The assemblyjig is installed before the outer housing for restraininglongitudinal/vertical movement of the motor compo-nents during press fit placement of the outer casing.[001 8] The present invention includes a wide range ofuseful applications for the actuators, such as in control-ling fluid flow in hydraulic systems, fuel flow controls,braking systems, and so on. However, because of theiruniquely high reliable performance the torque motorsare especially well suited for aviation, and other appli-cations wherever severe to extreme operating condi-tions due to vibration and rapid heating/cooling cyclesmay exist. In this regard, the torque motors as disclosedherein are especially useful in combination with ser-vovalves generally, and more specifically, in combina-tion with hydraulic fuel valves, and other applications re-quiring virtual fail safe performance, such as in jet air-craft engines.[0019] In accordance with the invention, methods arealso provided for reducing the susceptibility of torquemotors to external vibration while also maximizing struc-tural damping effect. That is to say, it is yet a further ob-ject of the invention to provide in addition to more relia-ble torque motors and applications therefor, usefulmethods for assembling torque motors by the steps of:

(iii) assembling the outer casing of step (ii) onto thetorque motor of step (i) by slidably press fitting thecasing therearound to apply clamping forces direct-ly or indirectly on the torque motor components to5 positively retain them in place by frictional forceswithout requiring adhesives, resins or fastenermeans.[0020] It will be understood that in some configura-10 tions of torque motors where the foregoing method ofassembly employs but a single magnet and coil, for ex-ample, the space ordinarily occupied by a second coil;second, third or fourth magnet, and so on, may requiretwo or more non-functional or dummy components inis place thereof. Otherwise, the assembly will not have thedesired compressive fit with the outer casing.[0021] It is still a further object to provide improvedmethods for assembling torque motors wherein the polepieces and armature have openings adjacent to the air20 gaps, which openings are keyed to receive means formeasuring the width of the air gaps and for receivingfasteners for adjusting the width by elevating or loweringthe pole pieces. Such methods are especially useful ineliminating the inefficient process of trial assembly fre-25 quently employed heretofore wherein each motor wasassembled twice by the steps comprising a first trial as-sembly; measuring the air gaps between the armatureand pole pieces, disassembly of the torque motor; ma-chining and cleaning the parts to achieve the desired air30 gap width, followed by a second/reassembly of the mo-tor.[0022] For purposes of this invention the term widthwith respect to air gaps is intended to mean the distancebetween the pole face and armature surface.35 BRIEF DESCRIPTION OF THE DRAWINGS[0023] For a further understanding of the inventionand its characterizing features reference should now be40 made to the accompanying drawings wherein:

FIG. 1 is a perspective view of a cylindrically shapedtorque motor mounted to a servovalve housing withmotor components broken away to show the interior45 of the motor assembly;FIG. 2 is an exploded view of the torque motor as-sembly of Fig. 1;FIG. 3 is a sectional view of the torque motor-ser-vovalve assembly taken along line 3-3 of Fig. 11;so FIG. 4 is a top sectional view of the torque motortaken along line 4-4 of Fig. 3;FIG. 5 is an end view of an oval shaped torque mo-tor according to the invention;FIG. 6 is a perspective view of a torque motor with55 parts broken away to show the method for adjustingthe lower air gap without requiring disassembly;FIG. 7 is also a perspective view of a torque motorwith parts broken away showing an air gap adjust-

(i) providing a torque motor comprising at least the 45following components: a plurality of spaced polepieces forming air gaps therebetween, an armature,means for suspending the armature between the airgaps, at least one coil positioned about the arma-ture and at least one magnet in engagement with sothe pole pieces;(ii) providing an outer casing for housing the torquemotor of step (i), the outer casing having a roundedconfiguration with a wall thickness in the range ofabout 0.30 to 0.76 mm and dimensions limited to 55provide an interference fit when engaged with theperipheral surface of the torque motor assembly,and

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7 EP 0 727 868 B1 8ing fixture mounted to the upper end of the motorfor moving the upper pole piece;FIG. 8 is a side perspective view of an assembledtorque motor and servovalve;FIG. 9 is a top plan view of the torque motor-ser-vovalve combination shown in Fig. 8;FIG. 10 is a bottom view of the torque motor-ser-vovalve combination shown in Fig. 8;FIG. 11 is aside sectional view of the torque motor-servovalve combination taken along line 11-11 ofFig. 8.

DESCRIPTION OF THE PREFERREDEMBODIMENTS[0024] Turning first to Figs. 1-2, there is shown oneembodiment of a torque motor 10 assembled accordingto the invention and mounted onto the housing of an hy-draulic fuel valve 12, a type of servovalve, wherein thetorque motor performs as an actuator therefor. While theparticular configuration of the internal components ofmotor 10, as discussed hereinbelow, is provided for pur-poses of illustration, it is to be understood that the in-ventive concepts as disclosed herein apply to virtuallyany torque motor configuration having comparable ap-plications, and the torque motor of Fig. 1 is only repre-sentative. For purposes of this invention, such motorsshould have at least two spaced pole pieces, an arma-ture, means for suspending the armature to allow rota-tion in the air gaps between the spaced pole pieces, oneor more coils, at least one magnet and a motor housing.[0025] One preferred embodiment of a torque motorincorporating the concepts of this invention is illustratedby Fig. 1 wherein torque motor 10 comprises first andsecond pole pieces 14-1 6, respectively having opposingpole faces 15-17 spaced from one another to providean air gap 18 therebetween. Shims 19 (Fig. 3) on upperpole face 15 limit displacement of the armature. Arma-ture 20 with end pieces 22 is positioned between polefaces 15-17 for angular displacement in air gap 18. Agenerally U-shaped tube assembly 24, best illustratedby Fig. 2, includes a jet pipe 59 which passes throughthe interior of flexure tube 58. Jet pipe 59 functions asthe motor output shaft, and is coupled to valve housing12 by engaging the enlarged lower end of flexure tube58 to inlet 62. In general, the output shaft of the inventionmay be coupled to any type of load, such as clutch,brake, spool valve, or as in the illustrated representativeexample acts to convey motion of the armature to thejet pipe controlled by the torque motor.[0026] Electromagnetic coils 26 positioned about thearmature provide magnetic flux to the armature, perma-nent magnets 28 are stationed at the peripheral edgesof the motor with poles of opposite polarity of each mag-net positioned on opposite sides of armature 20. Amotorassembly jig 30 in the form of a component cage, al-though optional, is especially useful as a retainer to re-strict longitudinal movement of the above components

during press fit placement of motor housing 32 circum-ferentially around the motor assembly. Encasement ofthe motor is completed with a housing cap 34 which pro-vides secondary retention of the magnets and coils after5 assembly.[0027] The exploded view of Fig 2 provides more de-tails of the motor assembly of Fig. 1. In this regard, it willbe observed that motor housing 32 may in one preferredembodiment consist of a cylindrically shaped thin walled10 sleeve 36, formed from a metal or metal alloy, preferablyone having the same or approximately the same coeffi-cient of thermal expansion of materials used in fabricat-ing other motor components, e.g., pole pieces, armatureand magnets; have high strength and ideally be non-15 magnetic. A representative preferred motor housingmaterial is titanium metal or titanium alloy, such as6AI4V, which is commercially available through ordinarychannels of commerce. Expressions like thin walledare principally intended to relate to thicknesses in the20 range of approximately 0.30 to about 0.76 mm (0.012 toabout 0.030 inches).[0028] Optionally, but preferably, thin walled metallicsleeve 36 of motor housing 32 contains a multiplicity ofinwardly directed surface elevations or dimples 38 stra-ps tegically positioned to engage with each of permanentmagnets 28, of which there are four.[0029] While torque motors embodying the conceptsof the invention most preferably relate to actuators hav-ing circular configurations, e.g., housed in cylindrically30 shaped outer casings, it should be understood the con-cepts of the invention as disclosed herein also apply totorque motors assembled in other generally roundedconfigurations, such as the oval shaped actuator illus-trated in Fig. 5. In this regard, torque motor 88 (Fig. 5)35 contains a motor housing 90 which engages the motorassembly 92 applying inwardly directed compressiveforces as a result of an interference fit between outerhousing 90 and motor assembly 92. As with cylindricallyshaped motors, frictional forces generated by the oval40 shaped housing impart desired rigidity and strength tothe motor assembly for greater resistance to externalvibration while maximizing structural damping. The forc-es resisting vibration are especially effective when mo-tor housing 90 includes multiple inwardly directed sur-45 face elevations 94, such as those illustrated in the formof dimples on the ID of the housing which engage witheach of magnets 91 .[0030] Permanent magnets 28 (Fig. 2) are quarterrounds with each having an inner notch 40 to provideso upper first and lower second end portions of oppositepolarity with each end portion disposed on oppositesides of the armature.[0031] Pole pieces 14-16 are substantially C-shapedand spaced from one another with their pole faces 15-1755 positioned opposite the other. Armature 20 includes ter-minal end portions 22 intersecting the plane betweenthe pole faces forming upper and lower air gaps at eachend of the armature typically ranging from 0.13 mm

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9 EP 0 727 868 B1 10(0.005 inches) to about 0.64 mm (0.025 inches). Upperand lower flux conducting pole pieces 14-16 preferablyhave threaded openings 42-44, respectively runningperpendicular and adjacent to pole faces 15-17. Arma-ture 20 contains non-threaded openings 46 keyed to co-incide with openings 42-44 of pole pieces 14-16. As willbe discussed in greater detail below, the openings in thepole pieces and armature are specially useful in meas-uring and setting the width of air gaps between the polepieces and armature during the assembly procedure.[0032] Electromagnetic coils 26 for generating mag-netic flux in the armature each have a central opening48 for receiving armature end pieces 22. Coils 26 arealso equipped with spacers 50 and electrical conductors52. Spacers 50 engage with each other, as best illus-trated by Fig. 4.[0033] As previously stated, armature 20 is equippedwith a transversely positioned motor output shaft con-sisting of a generally U-shaped tube assembly 24. Ar-mature 20 is suspended between the air gaps by a pairof flexure tubes 54-58 which allow the armature to rotateabout an axis passing through the axis of both flexuretubes at the mid-length of their flexing portions. Flexuretube 54 serves to convey fluid from a supply duct 60 toa U-shaped tube 56 which connects to jet pipe 59 run-ning through flexure tube 58. Flexure tubes 54-58 actas flexural seals preventing fluid from contacting torquemotor components. While U-shaped tube assembly 24is illustrated extending perpendicularly from the arma-ture, it will be understood the invention contemplates al-ternative motor configurations, e.g., wherein the motoroutput shaft and flexure tube suspension means run lon-gitudinally with the armature.[0034] Assembly jig 30 consists of a cylindricallyshaped metallic cage having axially aligned ring sec-tions 64-66 and dual connecting struts 68. The cylindri-cally shaped assembly jig 30 is made to be expandablewhen slidably engaged over the motor assembly. Thisis accomplished by not bonding adjacent edges of thejig, but instead providing a gap 70 at one strut 68.[0035] One useful assembly procedure which avoidsinefficient trial assembly methods previously describedfor the torque motors of this invention consists of install-ing flexure tubes 54-58 by pressing into openings intoarmature 20 followed by first brazing tubular elbow 56and jet pipe 59 thereto. Flexure tubes 54 and 58 of thearmature-jet pipe assembly are then press fitted to theservovalve housing outlet 60 and inlet 62, respectively.Electromagnetic coils 26 can then be inserted onto thearmature by slipping coil openings 48 over armature endpieces 22. Coil conductor leads 52-53 are then routedthrough lead exit 72 in servovalve housing 12. Lowersecond pole piece 16 is slid into place below the bottomedge of coils 26. Notch 74 in lower pole piece 16 enablespositioning without interference with flexure tubes54-58. Upper pole piece 14 is then placed over coils 26.The assembly jig 30 is then spread open at gap 70 witha spacer (not shown) sufficiently to allow longitudinal

passage over the torque motor assembly including pastthe armature and coils. The jig spacer is then removedand coils 26 positioned inside the areas having threesided rectangular openings 76 in assembly jig 30. Each5 of the 4 magnets are then vertically positioned in theopen areas of the cage adjacent to the coils 26, as bestillustrated by Fig. 4.[0036] Before pressing on sleeve 36 of motor housing32 onto the torque motor assembly, threaded jack10 screws 78 (Fig. 6) are installed in tapped openings 44of lower pole piece 16. Jack screws 78 are initially tight-ened to elevate the lower pole piece so pole faces 17are in contact with the bottom side of armature end piec-es 22 to provide zero lower air gaps.is [0037] Sleeve 36 of motor housing 32 have surfaceelevations 38 (Figs. 1, 2 and 4) aligned so they makefirm contact with the centers of each magnet 28 OD sur-face when the sleeve is pressed into place. Frictionalforce between sleeve 36 IDand upper pole piece 14ap-20 ply pressure to the upper side of armature 20. However,armature 20 is securely supported by lower pole piece16 and jack screws 78 to also provide zero upper airgaps. Longitudinal/vertical movement of magnets 28 isrestricted by assembly jig 30 during press fit placement25 of the metal sleeve.[0038] After fully pressing tubular sleeve 36 in placecircumferentially about the torque motor assembly thelower air gaps must be reformed between each poleface 17 of lower pole piece 16 and the underside of ar-30 mature 20, and upper air gaps reformed between eachpole face 15 of upper pole piece 14 and the upper sideof armature 20. The lower jack screws 78 (Fig. 6) areturned counter clockwise about one-half revolution to el-evate the lower jack screw ends off the floor of valve35 housing 12. This in-turn will permit lowering lower polepiece 16 about 0.41 mm (0.016 inch), assuming a 0.81mm (0.032 inch) thread for the jack screws, by tappingthe heads of the lower jack screws with the aid of analien wrench, or other small tool. Afeeler gauge 80 (Fig.40 6) can then be inserted into openings 42 in the upperpole piece to check the width of the lower air gaps be-tween the underside of the armature and each of polefaces 17. Feeler gauge 80 can be equipped with a smallmetallic disc 82 having athickness, e.g., 0.38 mm (0.01545 inches). Any adjustments in the width of the lower airgaps can be effectuated by turning lower jack screws. Itwill be understood that use of the above feeler gaugefor measuring the air gaps is only one representativeexample of such a device. And the invention contem-50 plates use of any number of measuring means, such asoptical methods of directly observing the air gap via adiagonal mirror inserted into the hole, and measuringthe gap by visual comparison with a graduated reticule.[0039] The width of the upper air gaps between pole55 faces 15 of upper pole piece 14 and armature 20 canbe adjusted by attaching air gap fixture 84 (Fig. 7) withjack screws 86 to the upper end of motor housing 32.Threaded jack screws 86 once engaged with tapped

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11 EP 0 727 868 B1 12openings 42 in the upper pole piece can be used to el-evate the upper pole piece by turning about one-half rev-olution to provide a gap of about 0.47 mm (0.016 inch-es). The width of the gap can be verified with feelergauge 80 as previously discussed in connection with the slower air gaps. After adjusting the air gap dimensions,optionally they can be permanently locked into place byany number of methods, including spot welding the polepieces, applying a threaded fastener through the sidewall of sleeve 36, and so on. 10[0040] As previously indicated, one principal aspectof the invention is reducing the susceptibility of a torquemotor to external vibration while maximizing structuraldamping. The inventors have been able to achieve thisobjective by holding the components of the motor as- 15sembly rigidly in place through frictional forces fromcompressive engagement of the motor assembly bymeans of a generally thin walled tubular casing, e.g.,cylindrically shaped sleeve 36 (Fig. 4), oval shapedsleeve 90 (Fig. 5), etc. The inward compressive forces 20according to the invention are generated through an in-terference fit between the tubular shaped housing andthe motor assembly. The inventors, however, have dis-covered that ID surface elevations 38 (Fig 4) and 94(Fig. 5) are specially useful in producing even a higher 25degree of rigidity and stability in motor assemblies be-cause it was discovered serendipitously that the eleva-tions have a tendency to produce a stretching and a gen-erally flattening effect on the thin metal tubular housingsidewalls in areas 96 (Fig. 4) and 98 (Fig. 5) between 30adjacent elevations. Desirably, this flattening effect pro-duces more inwardly directed compressive forces foreven greater motor stability.[0041] Figs. 3 and 8-11 relate to the torque motor-hy-draulic fuel/servovalve combination 100. Servovalves 35are devices which control flow or pressure of fluids (liq-uid or gas) in proportion to an electrical input. They area subgroup of servovalves in general that control fluidpressure orflow in proportion to mechanical, pneumatic,electrical, thermal, optical or magnetic input. Hydraulic 40valve 102 (Fig 8) in particular is useful in controlling theflow of fuel to a jet aircraft engine. The valve housingincludes flanges 104 for mounting the device withthreaded fasteners (not shown). The underside of valve102 shows various ports without filter screens, including 45a large supply port 106 which is connected to a sourceof fluid under pressure (liquid or gas); a return port 108connected to a source of lower pressure, or sink, twocontrol ports 110, which are connected to an hydraulicload, such as a piston actuator 111 (Fig. 3), and a pair soof electrical conductors 112 connected to an adjustablesource of electric current.[0042] An electric current applied to the torque motorcauses the flow of hydraulic fluid 105 (Fig. 11) from sup-ply port 106 to a control port 110 (Fig. 3), the particular 55control port being determined by the location of the jetpipe nozzle 119 of jet pipe 59 relative to bores 116 and118 of receiver 120. The position of the jet pipe and noz-

zle relative to the receiver bores is proportionately mod-ulated according to the amplitude of the current appliedto the torque motor and polarity. Thus, as the armatureproportionally moves the jet pipe nozzle 119 at the ex-treme end of jet pipe 59 the nozzle will ether be coinci-dent with the axis of either receiver bore, or midpoint ofthe bridge between the bores, or at any location be-tween these limits. It will be noted, except where jet pipe59 is pressed into the outer flexure tube 58 the OD ofjet pipe 59 is less than the ID of the flexure tube. Thisstructural feature allows the jet pipe to rotate inside theflexure tube with angular displacement of the armatureupon actuation of the torque motor. Lateral displace-ment of the jet pipe between receiver bores 116 and 118is thus due to its rotational movement.[0043] Valve 102 also possesses important structuralfeatures that enables adjustment of hydraulic output forzero current by mechanical setting means incorporatedtherein. These structural features are significant in pre-venting inadvertent changes in the null adjust whichmight otherwise be caused by external influences, suchas temperature change, shock or vibration. Receiver120 (Fig. 3) is mounted for lateral right and left move-ment, but advantageously restricted in rotational move-ment. On the left side (Fig. 3) null adjust means consistsof a null adjust threaded screw 122 shown threaded intoa plug 123 which is retained in the valve housing bymeans of an externally threaded sleeve 124. At the op-posite end or the right side of receiver 120 there is arectangular tab 126 extending axially from the receiverwhich engages with slot 128 in plug 130, the latter beingretained by an externally threaded sleeve 132 in thevalve housing.[0044] Conical spring washers (Bellville) 134 at theright end of receiver 120 hold the receiver against nulladjust screw 122. Because of the preloading by conicalsprings 134 when the null adjust screw is rotated thereceiver moves laterally to the left or right depending onthe direction of rotation of the screw. This is especiallyuseful in making precise axial adjustments for zero inputcurrent in positioning receiver bores 116-118 relative tothe center of nozzle 119 of the jet pipe. Advantageously,such lateral adjustments of the receiver can be per-formed without causing rotation of the receiver about itsaxis. Any rotational movement occurring during null ad-just would allow the receiver bores to move away fromtheir preferred position, which is exactly centered underthe jet pipe. Rotational movement of the receiver is pre-vented by close fit engagement of rectangular tab ex-tension 126 with slot 128 of plug 130. Thus, the receiveris able to move side-to-side freely when making delib-erate null adjustments while simultaneously preventedfrom making unintended rotational movements by sim-ply turning a single null adjust screw (122).[0045] Nevertheless it may be necessary to adjust theposition of receiver 120 relative to the center of the jetpipe by rotational movement, either clockwise or coun-ter clockwise. This adjustment can be performed by

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13 EP 0 727 868 B1 14loosening externally threaded sleeve 132, and rotatingplug 130 by engaging slot 128 with a screwdriver. Oncethe receiver is rotated to the correct position externallythreaded sleeve 132 is re-tightened to lock plug 130 andreceiver in the desired position.[0046] As previously discussed, an electric currentapplied to the torque motor causes the flow of hydraulicfluid 105 (Fig. 11) from supply port 106 to a control port110 (Fig. 3). At the same time, the alternate control port110 (Fig. 3) performs as a connection for return flow 114from piston actuator 111 through receiver bore 116 to fillreturn space 121 (Fig. 3) located between OD of jet pipe59 and ID of flexure tube 58. The return flow proceedsas a low pressure drain from slot 117 (Fig. 11), a tan-gential notch in receiver 120, to return port 108 (Fig. 11)for collection as hydraulic fluid supply 105.[0047] Modifications are possible within the scope ofthe appended claims.

Claims1. Atorque motor comprising first and second flux con-ducting pole pieces(1 4, 16) spaced from one anoth-er to define air gaps (18); an armature (20) sus-pended between said pole pieces with ends thereofextending into said air gaps (18); motor output shaftmeans (59) rigidly affixed to said armature (20) formovement therewith; electromagnetic coil means(26) positioned about said armature (20); perma-nent magnetic means (28) having first and secondsections of opposed polarity disposed on oppositesides of said armature (20) in engagement with said

pole pieces (14,16); and an outer casing (32) forhousing said motor, components of said motor be-ing held rigidly in place through frictional forces fromcompressive engagement by said outer casing(32).2. The torque motor of claim 1 wherein the peripheraledges of said pole pieces (14,16), coil means (26)and magnetic means (28) are compressively en-gaged by means of the interior surface of said outercasing (32).3. The torque motor of claim 1 wherein componentsof said motor are held in place by inwardly directedclamping forces produced by the interference fit be-tween said outer casing (32) and the peripheraledges of said pole pieces (14,16), coil means (26)and magnetic means (28) of said motor.4. The torque motor of claim 1, wherein componentsof said motor are held in place by inwardly directedclamping forces from an interference fit between theinterior surface of said outer casing (32; 90) and theperipheral surface of said magnetic means (28; 91 ).

5. The torque motor of claim 4, wherein the interfer-ence fit between said interior surface of said outercasing (32; 90) and said peripheral surface of saidmagnetic means (28; 91) is produced through sur-5 face elevations (38; 94).6. The torque motor of claim 5 wherein the surface el-

evations (38; 94) are located on said outer casing(32; 90).10 7. The torque motor of claim 5 wherein the surface el-evations are located on the outer surface of saidpermanent magnetic means (28; 91).is 8. The torque motor of claim 4 wherein said outer cas-ing (32) is a generally thin walled cylindricallyshaped housing (36).

9. The torque motor of claim 1wherein the output shaft20 (59) extends perpendicularly from said armature(20), said armature supported for angular displace-ment in said air gaps (18).

10. The torque motor of claim 1 wherein the first and25 second flux conducting pole pieces (14,16) and thearmature (20) have perpendicular openings (42,44;46) in proximity to said air gaps (18) for receivingmeans (80) for measuring the width of said air gapsand fasteners (86) for setting the width of said air30 gaps.11. The torque motor of claim 1 which is free of poly-meric fillers and motor component fasteners.

35 12. The torque motor of claim 1wherein the axis of saidarmature (20) is coextensive with the longitudinalaxis of said outer casing (32).13. The torque motor of claim 1wherein the axis of said40 armature (20) is transverse to the longitudinal axisof said outer casing (32).14. The torque motor of claim 1 in combination with ahydraulic fuel valve (102).4515. The torque motor of claim 1 wherein said pole piec-es (14, 16) are substantially C-shaped with terminalend portions of the said first pole piece (14) oppo-sitely spaced from terminal end portions of said see-so ond pole piece (1 6) to define said air gaps, said ar-mature (20) suspended for angular displacementbetween said airgaps (18), said pole pieces and ar-mature having openings (42) adjacent to said air-

gaps (18) keyed for receiving means for measuring55 the width (80,82) of said airgaps and fasteners (86)for adjusting the width of said airgaps, said motoroutput shaft means extending transversely fromsaid armature (20) and comprises a flexible fluid de-

9.20

25

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15 EP 0 727 868 B1 16livery tube (54,58), and said outer casing (32; 90)having a rounded configuration and a wall thicknessin the range of about 0.30 to 0.76 mm.

16. The torque motor of claim 1or claim 15 wherein saidouter casing (32) is a cylindrically shaped housing.17. The torque motor of claim 1or claim 15 wherein saidouter casing (90) is a generally oval shaped hous-ing.18. The torque motor of claim 16 wherein said clampingforces are produced by an interference fit betweensaid cylindrically shaped outer casing (32) and com-ponents (14,16,26,28) of said motor.19. The torque motor of claim 16 wherein said cylindri-cally shaped outer casing (32) includes interior sur-face elevations (38) and the interference fit is pro-duced by said elevations engaging the peripheral

surface of said magnetic means (28).20. The torque motor of claim 1or claim 16 including jigmeans (30) for restraining longitudinal movementof said motor components during engagement ofsaid outer casing (32), said jig means positioned ad-jacent to the peripheral edge of said motor compo-nents and the interior surface of said outer casing.21 . The torque motor of any of claim 1, 16 or 17 in com-bination with a servovalve.22. Amethod for reducing the susceptibility of a torque

motor to external vibration while maximizing struc-tural damping effect, which comprises the steps of:

ing adhesives, resins or fastener means.23. The method of claim 22 wherein said outer casing(32; 90) includes surface elevations (38; 94) for di-5 rectly engaging said motor components.24. The method of claim 22 including the step of insert-

ing jig means (30) adjacent to the peripheral surfaceof said components before assembling said outer10 casing (step iii) for restricting longitudinal move-ment of said motor components during engagementby said outer casing (32).25. The method of claim 22 wherein said torque motoris of step (i) comprises four magnets (28) and the out-er casing (32) of step (ii) is cylindrically shaped andincludes interior surface elevations (38) which di-rectly engage the peripheral edge of said magnets(28).2026. The method of claim 22 including the step of pro-viding first and second flux conducting pole pieces(14, 16) spaced from one another to define air gaps(18); said armature (20) positioned between said25 pole pieces (1 4, 16) with ends thereof extending intosaid air gaps (18), said pole pieces and armaturehaving perpendicular keyed openings (42,44; 46) inproximity to said air gaps; introducing means(80,82) into said keyed openings for measuring the30 width of said air gaps (18) and introducing fasteners(86) into said openings (42) for adjusting the air gapwidths by moving the fasteners to elevate or lowersaid pole pieces (14, 16) relative to the ends of said

armature (20).35(i) providing a torque motor assembly compris-ing at least the following components: a plural-ity of spaced pole pieces (14,16) forming airgaps (18) therebetween, an armature (20),means for suspending the armature (20) be-tween said air gaps (18), at least one coil (26)positioned about the armature (20) and at leastone magnet (28) in engagement with the polepieces (14,16);(ii) providing an outer casing (32) for housingthe torque motor of step (i), said outer casinghaving a rounded configuration with a wallthickness in the range of about 0.30 to 0.76 mmand dimensions limited to provide an interfer-ence fit when engaged with the peripheral sur-face of said torque motor, and(iii) assembling the outer casing (32; 90) of step(ii) onto the torque motor of step (i) by slidablypress fitting said casing therearound to applyclamping forces directly or indirectly on saidtorque motor components to positively retainthem in place by frictional forces without requir-

Patentanspruche1. Drehmomentmotor mit ersten und zweiten KraftfluB40 fuhrenden Polschuhen (14,16), die zur Begrenzungvon Luftspalten (18) voneinander beabstandet sind,einem zwischen den Polschuhen aufgehangten An-ker (20), dessen Enden sich in die Luftspalte (18)erstrecken, einer mit dem Anker (20) zur Bewegung45 mit ihm starr verbundenen Motorausgangswelle(59), urn den Anker (20) herum angeordneten elek-tromagnetischen Spuleneinrichtungen (26), Per-manentmagneten (28) mit ersten und zweiten Ab-schnitten entgegengesetzter Polaritat, die auf ein-50 ander gegenuberliegenden Seiten des Ankers (20)in Eingriff mit den Polschuhen (14,16) angeordnetsind, und einem auBeren Gehause (32) zur Aufnah-me des genannten Motors, wobei die Komponentendes Motors durch Reibungskrafte infolge Kompres-55 sionseingriff durch das auBere Gehause (32) testan ihrem Platz gehalten sind.2. Drehmomentmotor nach Anspruch 1, bei dem die

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17 EP 0 727 868 B1 18Umfangsrander der Polschuhe (14,16), der Spule(26) und der Magnete (28) mit der Innenflache desgenannten auBeren Gehauses (32) in Kompressi-onseingriff sind.

3. Drehmomentmotor nach Anspruch 1, bei dem dieKomponenten des Motors an ihrem Platz durch ein-warts gerichtete Klemmkrafte gehalten sind, diedurch Passung zwischen dem auBeren Gehause(32) und den Umfangsrandern der Polschuhe(14, 16), Spule 26 und der Magnete (28) des Motorserzeugt werden.

4. Drehmomentmotor nach Anspruch 1, bei dem dieKomponenten des Motors an ihrem Platz durch ein-warts gerichtete Klemmkrafte infolge Passungssitzzwischen der Innenflache des auBeren Gehauses(32; 90) und der Umfangsflache der Magnete (28;91) gehalten werden.

5. Drehmomentmotor nach Anspruch 4, bei dem diePassung zwischen der Innenflache des auBerenGehauses (32; 90) und derUmfangsflache der ma-gnetischen Einrichtung (28; 91 )durch Oberflachen-erhohungen (38; 94) gebildet ist.6. Drehmomentmotor nach Anspruch 5, bei dem dieOberflachenerhohungen (38; 94) auf dem auBerenGehause (32; 90) angeordnet sind.7. Drehmomentmotor nach Anspruch 5, bei dem dieOberflachenerhohungen auf der AuBenflache derPermanentmahnete (28; 91) angeordnet sind.8. Drehmomentmotor nach Anspruch 4, bei dem dasauBere Gehause (32) ein im allgemeinen dunnwan-diges, zylinderformiges Gehause (36) ist.9. Drehmomentmotor nach Anspruch 1, bei dem dieAusgangswelle (59) sich senkrecht von dem Anker(20) erstreckt, der winkelverschieblich in den Luft-spalten (18) gelagert ist.10. Drehmomentmotor nach Anspruch 1, bei dem dererste und zweite KraftfluB fuhrende Polschuh

(14,16) und der Anker (20) in Nachbarschaft zu ih-ren Luftspalten (18) senkrechte Offnungen (42,44;46) haben zur Aufnahme von Mitteln (80) zur Mes-sung der Breite der Luftspalte und von Befesti-gungseinrichtungen (86) zur Einstellung der Breiteder Luftspalte.

11. Drehmomentmotor nach Anspruch 1, der von poly-merischen Fullstoffen und Befestigungsmitteln furMotorkomponenten frei ist.12. Drehmomentmotor nach Anspruch 1, bei dem dieAchse des Ankers (20) die gleiche Langserstrek-

kung wie die Langsachse des auBeren Gehauses(32) hat.13. Drehmomentmotor nach Anspruch 1, bei dem die5 Achse des Ankers (20) quer zu der Langsachse desauBeren Gehauses (32) verlauft.14. Drehmomentmotor nach Anspruch 1 in Kombinati-on mit einem hydraulischen Treibstoffventil (102).10 15. Drehmomentmotor nach Anspruch 1, bei dem diePolschuhe (14,16) im wesentlichen C-formig sind,wobei die Enden des ersten Polschuhs (1 4) mit Ab-stand den Enden des zweiten Polschuhs gegen-15 uberstehen, urn die genannten Luftspalte zu be-

grenzen, der Anker (20) zwischen die Luftspaltewinkelverschieblich aufgehangt ist, die Polschuheund der Anker Offnungen (42) neben den Luftspal-ten (18) zur Aufnahme von Einrichtungen zur Mes-20 sung der Breite (80,82) der Luftspalte und von Be-festigungsmitteln (86) zur Einstellung der Breite derLuftspalte haben, wobei sich die Motorausgangs-welle quer zu dem Anker (20) erstreckt und ein fle-xibles Stromungsmittel-Zufuhrungsrohr (54,58)25 aufweist und das auBere Gehause (32; 90) eine ab-gerundete Gestalt und eine Wandstarke in dem Be-reich von etwa 0,30 bis 0,76 mm hat.

16. Drehmomentmotor nach Anspruch 1 oder An-30 spruch 15, bei dem das auBere Gehause (32) einzylinderformiges Gehause ist.17. Drehmomentmotor nach Anspruch 1 oder An-

spruch 15, bei dem das auBere Gehause (90) ein35 Gehause von im allgemeinen ovaler Gestalt ist.18. Drehmomentmotor nach Anspruch 16, bei dem dieKlemmkrafte durch einen Passungssitz zwischendem zylindrisch geformten auBeren Gehause (32)40 und den Motorkomponenten (14,16,26,28) erzeugtwerden.19. Drehmomentmotor nach Anspruch 16, bei dem daszylindrisch geformte auBere Gehause (32) innere45 Oberflachenerhebungen (38) enthalt und der Pas-sungssitz durch die genannten, mit der Umfangs-flache der Magnete (28) in Eingriff befindlichen Er-hebungen erzeugt wird.

so 20. Drehmomentmotor nach Anspruch 1 oder An-spruch 16 mit Einspannmitteln (30) zur Unterdruk-kung der Langsbewegung der Motorkomponentenwahrend des Eingriffs des auBeren Gehauses (32),wobei die Einspannmittel an dem Umfangsrand der55 Motorkomponenten und der Innenflache des auBe-ren Gehauses angeordnet sind.21. Drehmomentmotor nach einem der Anspruche 1,

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19 EP 0 727 868 B1 2016 oder 17 in Kombination mit einem Servoventil.

22. Verfahren zur Verringerung der Suszeptibilitat ei-nes Drehmomentmotors gegenuber auBererSchwingung bei Maximierung des strukturellen sDampfungseffekts, bei dem man(i) einen Drehmomentmotorsatz vorsieht mitwenigstens den folgenden Komponenten: ei-ner Mehrzahl von auf Abstand gehaltenen Pol- 10schuhen (14, 16) mit zwischen ihnen gebildetenLuftspalten (18), einem Anker (20), Mitteln zumAufhangen des Ankers (20) zwischen den ge-nannten Luftspalten (18), wenigstens einer urnden Anker (20) herum angeordneter Spule (26) 15und wenigstens einem Magnet (28) im Eingriffmit den Polschuhen (14,16);(ii) ein auBeres Gehause (32) vorsieht zur Auf-nahme des Drehmomentmotors der Stufe (i),wobei das Gehause eine abgerundete Gestalt 20mit einer Wanddicke in dem Bereich von etwa0,30 bis 0,76 mm und begrenzte Abmessungenzur Schaffung eines Passungssitzes bei Ein-griff mit der Umfangsflache des Drehmoment-motors hat; und 25(iii) das auBere Gehause (32; 90) der Stufe (ii)mit dem Drehmomentmotor der Stufe (i) zu-sammensetzt, indem man das Gehause durchgleitenden PreBsitz auf den Motor aufbringt,urn Klemmkrafte direkt oder indirekt auf die ge- 30nannten Drehmomentmotorkomponenten aus-zuuben, urn diese durch Reibungskrafte ohneKlebstoffe, Harze oder Befestigungsmittelkraftschlussig an ihrem Platz zu halten. 3523. Verfahren nach Anspruch 22, bei dem das auBereGehause (32; 90) Oberflachenerhohungen (38; 94)fur den direkten Eingriff mit den Motorkomponentenenthalt. 4024. Verfahren nach Anspruch 22, mit der Stufe des Ein-setzens der Einspannmittel (30) an der Umfangs-flache der genannten Komponenten vor der Monta-

ge des auBeren Gehauses (Stufe iii), urn die Langs-bewegung der Motorkomponenten wahrend des 45Eingriffs mit dem auBeren Gehause (32) einzu-schranken.25. Verfahren nach Anspruch 22, bei dem der Drehmo-mentmotor der Stufe (i) vier Magnete (28) umfaBt sound das auBere Gehause (32) der Stufe (ii) zylin-drisch geformt ist und innere Oberflachenerhebun-

gen (38) hat, die sich dem Umfangsrand der Ma-gnete (28) direkt anlegen. 5526. Verfahren nach Anspruch 22, bei dem man ersteund zweite KraftfluB fuhrende Polschuhe (14,16)vorsieht, die zur Begrenzung von Luftspalten (18)

voneinander auf Abstand gehalten sind, der ge-nannte Anker (20) zwischen den Polschuhen(14,16) angeordnet ist, wobei deren Enden sich indie Luftspalte (18) erstrecken, die Polschuhe undder Anker nahe den Luftspalten senkrechte verkeil-te Offnungen (42,44; 46) haben, und bei dem manMittel (80,82) in die genannten Offnungen zur Mes-sung der Breite der Luftspalte (18) und Befesti-gungsmittel (86) in die Offnungen (42) einfuhrt, urndie Luftspaltbreiten durch Bewegung der Befesti-gungsmittel einzustellen, indem die Polschuhe(14, 16) relativ zu den Enden des Ankers (20) geho-ben oder gesenkt werden.

Revendications1. Moteur couple comprenant des premiere et secon-de pieces polaires (14, 16) conductrices du flux es-

pacees I'une de I'autre pour definir des espaces li-bres (18) pour I'air; un induit (20) suspendu entrelesdites pieces polaires, dont les extremites s'eten-dent, a I'interieur desdits espaces libres (18) pourI'air; un moyen d'arbre de sortie de moteur (59) fixede maniere rigide audit induit (20) pour effectuer unmouvement avec ce dernier; un moyen de bobineelectromagnetique (26) positionne autour dudit in-duit (20); un moyen d'aimant permanent (28) pos-sedant des premiere et seconde sections de pola-rite opposee disposees sur les cotes opposes duditinduit (20) en contact avec lesdites pieces polaires(14, 16); et un carter externe (32) dans lequel vientse loger ledit moteur, les composants dudit moteuretant maintenus en place de maniere rigide via desforces de friction provenant de la mise en contactpar compression avec ledit carter externe (32).

2. Moteur couple selon la revendication 1, dans lequelles bords peripheriques desdites pieces polaires(14, 16), dudit moyen de bobine (26) et dudit moyend'aimant (28) sont mis en contact par compressionavec la surface interne dudit carter externe (32).3. Moteur couple selon la revendication 1, dans lequelles composants audit moteur sont maintenus enplace via des forces de serrage orientees vers I'in-terieur, generees par le joint a ajustement serre en-tre ledit carter externe (32) et les bords peripheri-

ques desdites pieces polaires (14, 16), dudit moyende bobine (26) et dudit moyen d'aimant (28) duditmoteur.4. Moteur couple selon la revendication 1, dans lequelles composants dudit moteur sont maintenus enplace via des forces de serrage orientees vers I'in-terieur, generees par un joint a ajustement serre en-tre la surface interne dudit carter externe (32; 90)et la surface peripherique dudit moyen d'aimant (28;

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21 EP 0 727 868 B1 2291).

5. Moteur couple selon la revendication 4, dans lequelle joint a ajustement serre entre ladite surface inter-ne dudit carter externe (32; 90) et ladite surface pe-ripherique dudit moyen d'aimant (28; 91 ) est obtenuvia des elevations de surfaces (38; 94).6. Moteur couple selon la revendication 5, dans lequelles elevations de surfaces (38; 94) sont disposeessur ledit carter (32; 90).7. Moteur couple selon la revendication 5, dans lequelles elevations de surfaces sont disposees sur lasurface externe dudit moyen d'aimant permanent(28; 91).8. Moteur couple selon la revendication 4, dans lequelledit carter externe (32) est un carter (36) de formegeneralement cylindrique a paroi mince.9. Moteur couple selon la revendication 1, dans lequelI'arbre de sortie (59) s'etend perpendiculairementaudit induit (20), ledit induit etant supporte a des finsde deplacement angulaire dans lesdits espaces li-bres (18) pour I'air.10. Moteur couple selon la revendication 1, dans lequelles premiere et seconde pieces polaires (14, 16)conductrices du flux et I'induit (20) possedent desouvertures perpendiculaires (42, 44; 46) a proximitedesdits espaces (18) pour I'air pour la receptiond'un moyen (80) destine a mesurer la largeur des-dits espaces libres pour I'air et de fixateurs (86) pourle reglage de la largeur desdits espaces libres pourI'air.11. Moteur couple selon la revendication 1, qui estexempt de matiere de charge polymere et de fixa-teur de composants de moteur.12. Moteur couple selon la revendication 1, dans lequelI'etendue de I'axe dudit induit (20) correspond a cel-le de I'axe longitudinal dudit carter externe (32).13. Moteur couple selon la revendication 1, dans lequelI'axe dudit induit (20) est transversal par rapport aI'axe longitudinal dudit carter externe (32).14. Moteur couple selon la revendication 1 en combi-naison avec une soupape de carburant hydraulique(102).15. Moteur couple selon la revendication 1, dans lequellesdites pieces polaires (14, 16) possedent essen-tiellement la forme d'un C, les portions de bornesde ladite premiere piece polaire (14) etant de pola-rite opposee et etant espacees par rapport aux por-

tions de bornes de ladite seconde piece polaire (16)pour definir lesdits espaces libres pour I'air, ledit in-duit (20) etant suspendu a des fins de deplacementangulaire entre lesdits espaces libres (18) pour I'air,5 lesdites pieces polaires et ledit induit possedant desouvertures (42) en position adjacente auxdits espa-ces libres (18) pour I'air, dimensionnees pour rece-voir des moyens pour mesurer la largeur (80, 82)desdits espaces libres pour I'air et des fixateurs (86)10 pour regler la largeur desdits espaces libres pourI'air, ledit moyen d'arbre de sortie de moteur s'eten-dant en direction transversale par rapport audit in-duit (20) et comprenant un tube flexible de distribu-tion de fluide (54, 58), et ledit carter externe (32; 90)is possedant une configuration arrondie et une epais-seur de paroi dans le domaine d'environ 0,30 a 0,76mm.

16. Moteur couple selon la revendication 1 ou 15, dans20 lequel ledit carter externe (32) est un carter de for-me cylindrique.

17. Moteur couple selon la revendication 1 ou 15, danslequel ledit carter cylindrique (90) est un carter de25 forme generalement ovale.18. Moteur couple selon la revendication 16, dans le-quel lesdites forces de serrage sont generees parun joint a ajustement serre entre ledit carter externe30 (32) de forme cylindrique et les composants (14, 16,26, 28) dudit moteur.19. Moteur couple selon la revendication 16, dans le-

quel ledit carter externe (32) de forme cylindrique35 englobe des elevations de surfaces internes (38) etle joint a ajustement serre est genere par lesditeselevations entrant en contact avec la surface peri-pherique dudit moyen d'aimant (28).40 20. Moteur couple selon la revendication 1 ou 16, en-globant un moyen de gabarit (30) pour restreindrele mouvement longitudinal desdits composants dumoteur lors de la mise en contact avec ledit carterexterne (32), ledit moyen de gabarit etant dispose45 en position adjacente au bord peripherique desditscomposants du moteur et a la surface interne duditcarter externe.

21 . Moteur couple selon I'une quelconque des revendi-50 cations 1, 16 ou 17 en combinaison avec une sou-pape de commande.

22. Procede pour reduire la sensibilite d'un moteur cou-ple a des vibrations externes tout en maximisant55 son effet d'amortissement structural, qui comprendles etapes consistant a:(i) procurer un assemblage de moteur couple

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23 EP 0 727 868 B1 24comprenant au moins les composants ci-apres:plusieurs pieces polaires espacees (14, 16) for-mant entre elles des espaces libres (18) pourI'air, un induit (20), des moyens pour suspendreI'induit (20) entre lesdits espaces libres (18) spour I'air, au moins une bobine (26) positionneeautour de I'induit (20) et au moins un aimant(28) en contact avec les pieces polaires (14,16);(ii) procurer un carter externe (32) dans lequel 10vient se loger le moteur couple de I'etape (i),ledit carter externe possedant une configura-tion arrondie avec une epaisseurde paroi dansle domaine d'environ 0,30 a 0,76 mm et posse-dant des dimensions limitees pour procurer un 15joint a ajustement serre lors de sa mise en con-tact avec la surface peripherique dudit moteurcouple, et(iii) assembler le carter externe (32; 90) de I'eta-pe (ii) au moteur couple de I'etape (i) en ajus- 20tant par glissement ledit carter autour dudit mo-teur pour exercer des forces de serrage de ma-niere directe ou indirecte sur lesdits compo-sants du moteur couple dans le but de les main-tenir fermement en place via des forces de fric- 25tion sans avoir recours a des adhesifs, a desresines ou a des moyens de fixation.

et ledit induit possedant des ouvertures dimension-nees perpendiculaires (42, 44; 46) a proximite des-dits espaces libres pour I'air; introduire un moyen(80, 82) dans lesdites ouvertures dimensionneespour mesurer la largeur desdits espaces libres (18)pour I'air; et introduire des fixateurs (26) dans les-dites ouvertures (42) pour regler les largeurs desespaces libres pour I'air en deplacant les fixateursdans le but d'elever ou d'abaisser lesdites piecespolaires (14, 16) par rapport aux extremites duditinduit (20).

23. Procede selon la revendication 22, dans lequel leditcarter externe (32; 90) englobe des elevations desurfaces (38; 94) destinees a venir se mettre direc-tement en contact avec lesdits composants de mo-teurs.

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24. Procede selon la revendication 22, englobant I'eta- 35pe consistant a inserer un moyen de gabarit (30) enposition adjacente a la surface peripherique desditscomposants avant d'assembler ledit carter externe(etape iii) pour restreindre le mouvement longitudi-nal desdits composants de moteur lors de leur mise 40en contact avec ledit carter externe (32).

25. Procede selon la revendication 22, dans lequel leditmoteur couple de I'etape (i) comprend quatreaimants (28) et le carter externe (32) de I'etape (ii) 45est de forme cylindrique et englobe des elevationsde surfaces internes (38) entrant directement encontact avec le bord peripherique desdits aimants(28). 5026. Procede selon la revendication 22, englobant lesetapes consistant procurer des premiere et secon-de pieces polaires (14, 16) conductrices du flux, es-

pacees I'une de I'autre pour definir des espaces li-bres (18) pour I'air; positionner ledit induit (20) entre 55lesdites pieces polaires (14, 16) de telle sorte queleurs extremites s'etendent a I'interieur desdits es-paces libres (18) pour I'air, lesdites pieces polaires

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