119)
`United States Patent
`5,056,613
`(11) Patent Number:
`Porteret al.
`
`{45] Date of Patent: Oct. 15, 1991
`
`VEHICULAR SPEED CONTROL SYSTEM
`WITH REDUCED GEAR CHATTER
`
`5/1988 Morita et al... 74/409
`4,745,823
`4,781,073 11/1988 Bondhus et al. «0.0.0... 74/409 X
`
`[54]
`
`[75]
`
`Inventors: David L. Porter, Westland; Charles F.
`Weber, South Lyon; Kah S. Oo,
`Farmington Hills, all of Mich.
`
`[73]
`
`Assignee:
`
`Ford Motor Company, Dearborn,
`Mich.
`
`[21]
`
`[22]
`
`[51]
`[52]
`
`[58]
`
`[56]
`
`Appl. No.: 558,918
`
`Jul. 27, 1990
`Filed:
`
`acta F16H 55/24
`WeCUS ss scsaritvni
`TS, Gy ecrescaccsenserorenvenessanseeess 180/178; 74/440:
`123/361
`Field of Search................. 74/857, 402, 403, 409,
`74/440, 443; 180/178; 123/361
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`3/1920 Bryan .
`1,334,517
`1,558,222 10/1925 Beetow .
`3,229,546
`1/1966 Nallinger et al. oo... 74/857
`3,359,819 12/1967 Veillette et al.
`.
`4,640,147
`2/1987 Yasukawaetal. oo... 74/409
`i
`4,688,441
`8/1987 Yasukawaetal. ..
`
`4,739,670 4/1988 Tomita et al. oc. 74/440 X
`
`FOREIGN PATENT DOCUMENTS
`
`1161526
`
`1/1984 Camada .........cccessssseessereressers 74/857
`
`Primary Examiner—Allan D, Herrmann
`Assistant Examiner—William O. Trousdell
`Attorney, Agent, or Firm—Allan J. Lippa; Peter Abolins
`[57]
`ABSTRACT
`A vehicle speed contro] system having phasing cir-
`cuitry which provides a sequence of electrical phase
`steps in response to a comparison of actual vehicle
`speed to a desired vehicle speed. A stepper motor cou-
`pled to a pinion shaft rotates by discrete phase stepsin
`response to the phasing circuitry. An anti-backlash/-
`transfer gear assembly includes a first sprocket gear
`coupled to a second sprocket gear by integrally formed
`compression or
`flexure members which hold the
`sprocket gears together and a spring assembly which
`displaces the circumferential teeth of the two sprocket
`gears relative to one another. Another gear assembly
`couples rotational movement from the stepper motor to
`the engine throttle.
`
`15 Claims, 5 Drawing Sheets
`
`
`
`1
`
`Mattel Ex. 2005
`Mattel Ex. 2005
`Dynacraft v. Mattel
`Dynacraft v. Mattel
`IPR2018-00038
`IPR2018-00038
`
`

`

`U.S. Patent
`
`Oct. 15, 1991
`
`Sheet 1 of 5
`
`5,056,613
`
`
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`2
`
`

`

`U.S. Patent
`
`Oct. 15, 1991
`
`Sheet 2 of 5
`
`5,056,613
`
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`
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`3
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`

`

`U.S. Patent
`
`Oct. 15, 1991
`
`Sheet 3 of 5
`
`5,056,613
`
`
`
`ENTER
`CONTROL MODE
`
`
`
`
`STOREV,
`= Vp
`
`|-118
`
`COMPUTEV,
`
`[122
`
`SET GAIN
`CONSTANTS:
`KN
`
`COMPUTE
`POSITION COMMAND
`
`128
`
`A=K_*Vo|FIG.28
`+K SV,
`
`LTO &
`
` 130
`
`GENERATE
`SEQUENCE OF
`PHASE PULSES
`
`134
`
`
`
`COUNT PHASE
`PULSES TO
`GENERATE &,
`
`4
`
`140
`
`GO TO STANDBY
`MODE
`.
`
`

`

`U.S. Patent
`
`Oct. 15, 1991
`
`Sheet 4 of 5
`
`5,056,613
`
`
`
`;Sayees
`
`(La
`
`
`
`
` SAAAS
`
`5
`
`

`

`U.S. Patent
`
`Oct. 15, 1991
`
`Sheet 5 of 5
`
`5,056,613
`
`
`
`6
`
`

`

`1
`
`5,056,613
`
`VEHICULAR SPEED CONTROL SYSTEM WITH
`REDUCED GEAR CHATTER
`
`BACKGROUND OF THE INVENTION
`
`Thefield of the invention relates to a vehicular speed
`control system having reduced audible gear chatter.
`A typical speed control system includes a DC motor
`coupled to an engine throttle by mechanical transfer
`gears. The DC motoris usually responsive to a feed-
`back loop which compares actual vehicle speed with a
`set or desired speed to generate an error signal. Accord-
`ingly, the engine throttle is rotated by the DC motorin
`a direction to reduce the error signal. Since the inertia
`load (transfer gears, throttle linkage, and throttle) does
`not abruptly change, and the DC motorrotates at sub-
`stantially constant velocity, gear chatter has not been a
`problem with these systems. Stated another way, back-
`lash between mating transfer gears has not been recog-
`nized as a problem with conventional speed control
`systems,
`The inventors herein have recognized, and appear to
`be the first to have recognized, that gear backlash may
`be a problem when certain stepper motors are employed
`in speed contro] systems. More specifically, when the
`stepper motorrotates in discrete phase steps, the result-
`ing nonconstant angular velocity may result in a trans-
`fer gear backlash. This backlash may result in audible
`gear chatter which the vehicular operator may find
`disturbing. The inventors herein have also recognized
`that anti-backlash gears maybe utilized to advantage in
`a speed control system employing a stepper motor
`which rotates at nonconstant angular velocity. How-
`ever,
`the inventors herein believe that conventional
`anti-backlash gears are not suited for assembly in a mass
`production environment. More specifically, prior anti-
`backlash gears
`required complicated assembly of
`springs, pins, split gears, and retaining rings which re-
`quire considerable manual dexterity and therefore re-
`sults in time consuming assembly operations.
`SUMMARYOF THE INVENTION
`
`5
`
`5
`
`25
`
`30
`
`35
`
`45
`
`55
`
`An object of the invention herein is to provide a
`speed control system utilizing a stepper motor con-
`trolled to movein discrete phase steps and is coupled to
`a new anti-backlash gear to avoid audible gear chatter.
`Another object of the invention is to provide a new
`anti-backlash gear which is substantially less compli-
`cated and easier to assemble than heretofore possible.
`The above objects are achieved, and disadvantages of 50
`prior approaches solved, by providing a vehicular
`speed control system coupled to an engine throttle hav-
`ing reduced gear chatter. In one particular aspectof the
`invention, the speed control system comprises: phasing
`meansfor providing a sequenceofelectrical phase steps
`in response to a comparisonofactual vehicle speed to a
`desired vehicle speed; a stepper motor coupled to a
`pinion shaft for rotating the pinion shaft by discrete
`phase steps in response to the phasing means;first gear
`transfer means havinga plurality of gear teeth for rotat-
`ably coupling to the pinion shaft with minimal slack
`between the gear teeth of the first gear transfer means
`and gear teeth of the pinion shaft; and second gear
`transfer means coupled between the first gear transfer
`means and the throttle for displacing the throttle in
`response to rotational movementof the stepper motor.
`The above aspectof the invention provides an advan-
`tage of a speed contro] system employing a stepper
`
`60
`
`65
`
`7
`
`2
`motor which,althoughit rotates at nonconstant angular
`velocity,
`is substantially immune from audible gear
`chatter.
`In another aspect of the invention, the speed control
`system comprises: generating means for generating a
`speed error signal by comparing actual vehicle speed to
`a set speed; phasing meansfor providing a sequence of
`electrical phase steps in response to the speed error
`generating means; a stepper motor coupled to a pinion
`shaft for rotating the pinion shaft by discrete phase steps
`in response to the phasing means; first gear transfer
`means having a plurality of gear teeth for rotatably
`coupling to the pinion shaft with minimal slack between
`the gear teeth of the first gear transfer means and gear
`teeth of the pinion shaft, the gear transfer means com-
`prising a first sprocket gear coupled to a second
`sprocket gear in compression by a flexible member
`integrally formed onthefirst sprocket gear and extend-
`ing through an opening in the second sprocket gear to
`apply compression to an outer face of the second
`sprocket gear, guide means integrally formed on the
`outer face of the second sprocket gear for alignment
`with the flexible member, and spring means inserted
`between the flexible member and the guide means on
`the outer face of the second sprocketgear for displacing
`the first sprocket gear relative to the second sprocket
`gear; and second gear transfer means coupled between
`the first gear transfer means and the throttle for displac-
`ing the throttle in response to rotational movement of
`the stepper motor.
`The aboveaspectof the invention provides an advan-
`tage of substantially eliminating audible gear chatter in
`a speed control system employing a stepper motor.
`Another advantageofthe aboveaspectofthe invention,
`is that simple assembly is provided by inserting the
`second sprocket gear overthe first sprocket gear such
`that it is interlocked by the above described flexible
`member. Further, the spring may be simply inserted on
`the outer face of the second sprocket gear between the
`flexible member and guide. This results in a substan-
`tially foolproof assembly process requiring no tools and
`very few, simple assembly steps.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The objects and advantages described herein will be
`better understood by reading an example of an embodi-
`ment, referred to as the preferred embodiment, de-
`scribed below with reference to the drawings wherein:
`FIG. 1 is a perspective view of a speed control system
`in which the invention is used to advantage;
`FIG, 2Ais an electrical block diagram of the control
`circuitry for controlling the speed control system
`shownin FIG. 1;
`FIG. 2Bis a flowchart of various computational steps
`performed by the circuitry shown in FIG.2A;
`FIG.2C illustrates various electrical waveforms gen-
`erated by the circuitry shown in FIG. 2A;
`FIG.3A is an exploded view of a transfer/backlash
`gear utilized in the embodiment shown in FIG. 1;
`FIG. 3B is a bottom perspective view of a portion of
`the transfer/backlash gear shown in FIG. 3A;
`FIG. 3C is a top view of the transfer/backlash gear;
`FIG. 3D shows a partial perspective view taken
`along line 3D—3D shownin FIG. 3C;
`FIGS. 3E-3G illustrate the assembly process for
`assembling the transfer/backlash gear; and
`
`

`

`5,056,613
`
`3
`FIG. 4 is a partially broken away view of the trans-
`fer/backlash gear mating with a pinion shaft such that
`minimal slack exist between the transfer/backlash gear
`and pinion shaft.
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`
`Referring first to FIG. 1, vehicular speed control
`system 10 is shown including stepper motor 12, a three
`phase stepper motor in this example, positioned par-
`tially through housing 18 and coupled to pinion shaft
`16. Stepper motor 12 is responsive to electrical phase
`signals ®,', 3', and 3’, from control circuitry whichis
`described in greater detail later herein with particular
`reference to FIGS. 2A-2C. Also described in greater
`detail later herein with particular reference to FIGS.
`3A-3G,
`transfer/backlash gear 22 includes sprocket
`gear 28, sprocket gear 30, and pinion gear 32 mounted
`on shaft 34. Sprocket gear 28 and sprocket 30 form a
`split-gear pair having respective circumferential gear
`teeth 38 and circumferential gear teeth 40 displaced
`from one another for mating to pinion shaft 16 with
`minimal or zero slack.
`Pinion gear 32 is shown rotatably coupled to transfer
`gear 44 which is rotatably coupled to shaft 46. Rotat-
`able core 50 is fixedly connected to shaft 46 and electro-
`magnetically coupled and uncoupled to transfer gear 44
`via clutch plates 54. Electrical coils (not shown) within
`core 50 engage clutch plates 54 when speed control
`system 10 is activated, such as by an operating actuable
`button, and disengage clutch plates 54 when speed con-
`trol 10 is deactuated such as when the vehicular brakes
`are applied or the off switch depressed.
`Cable connector 58 is shown fixedly coupled to shaft
`46 for displacing throttle cable 62 and, accordingly,
`throttle plate 66 after cable slack “‘d” between throttle
`end 68 and throttle plate 66 is taken in. In operation,
`rotational movement of stepper motor 12 displaces
`throttle plate 66 by coupling rotational movement
`through pinion gear 16,
`transfer/backlash gear 22,
`transfer gear 44, rotatable core 50, shaft 46 and cable
`connector 58.
`Referring now to FIG. 2, a block diagram of the
`control circuitry for speed control system 10 is de-
`scribed. Speed control commandsare provided by con-
`ventional steering wheel mounted switches designated
`as ON/OFFswitch 76, SET/ACCELERATEswitch
`78, and COAST/RESUMEswitch 80, each of which
`provides corresponding electrical commandsto micro-
`processor 84, Transducer 86 provides microprocessor
`84 with speed signal V, corresponding to actual vehicle
`speed. Brake switch 90 provides an indication to micro-
`processor 84 when the vehicular brakes are activated.
`Microprocessor 84, a conventional microprocessor
`such as sold by Motorola is represented in FIG. 2 by
`functional blocks designated in general terms as feed-
`back controller 92, stepper command generator 96,
`phase pulse generator 98, and phase counter 102. As
`described later herein with particular reference to FIG.
`2B, feedback controller 92 generates a position com-
`mand by comparing actual vehicle speed (Vs) to a de-
`sired speed (Vp). Phase pulse generator 98 generates a
`sequence of phase pulses ©), 2, and 3 for the three
`phases of stepper motor 12. Phase counter 102 counts
`each phase to generate phase count Mc which is an
`inference of the actual position of stepper motor 12.
`Stepper command generator 96 compares the desired
`position command from feedback controller 92 with
`
`20
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`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4
`cto provide an updated position command to phase
`pulse generator 98. The resulting sequence of phase
`signals <b}, 2, and 3, are converted into the appropri-
`ate phase drive signals ®', ®2’, and ®3’ by conventional
`drivers 106, transistor switches in this example. A se-
`quence of phase drive signals ?)', 2’, and 3’ for a
`desired motor velocity is shown in FIG. 2C. Each phase
`represents power applied to the appropriate stator coil
`(not shown) of stepper motor 12 for turningits rotor by
`a predetermined phase increment.
`Referring now to FIG. 2B, a flowchart of various
`computational steps performed by microprocessor 84
`during the control mode (i.e., steady state speed con-
`trol) is shown. Although a microprocessor and associ-
`ated processing steps are described herein, those skilled
`in the art will recognize that these steps may be per-
`formed by other means such as discrete IC’s or corre-
`sponding analog devices. Vehicle speed is calculated
`(step 112) as described in U.S. patent application Ser.
`No. 280,907, the specification of which is incorporated
`herein by reference. If the set switch has been depressed
`by the operator since the last microprocessor back-
`ground loop (see step 116) the actual vehicle speed is
`stored in memory asthe set or desired speed Vp during
`step 118. Speed error signal Veis then computed during
`step 122 by subtracting desired speed Vp from actual
`speed Vs. Proportional gain constant Kp, quadratic gain
`constant Ky, and integral gain constant Kj are deter-
`mined during step 124. Position commandu, correlated
`to desired throttle position, is then computed during
`step 128 in accordance with the following equation:
`
`u=Kp*Ve+Kg*he*Ve+ Kis Ve
`
`During step 130, position command u is compared to
`phase count &c to determine the phase correction re-
`quired to bring stepper motor 12 to a desired phase
`position. In response, the required sequence of phase
`pulses is generated during step 134. An example of such
`a sequence is shownin FIG, 2C as previously described
`herein. Each phase pulse generated is counted to gener-
`s'¢ phase count ®c (step 136) which provides an indica-
`uon of actual position of stepper motor 12 and, accord-
`ingly, throttle 66. During step 138, microprocessor 84
`determines whether a disable signal has been received
`such as when the vehicular brakes are applied or an
`OFFsignal has been received. If a disable signal has not
`been received, the above described process steps are
`repeated during the next microprocessor background
`loop. Otherwise, speed control system 10 enters the
`standby mode(step 140) in which speed controlis deac-
`tivated until receipt of a SET or, if appropriate, a RE-
`SUME signal.
`Transfer/backlash gear 22 is now described in more
`detail with particular reference to FIGS. 3A4-3G. Re-
`ferring first
`to FIG. 3A, upper sprocket gear 28 is
`shown having circumferential teeth 38. Sprocket gear
`28 is also shown having upper face 150 recessed therein
`whichincludes axial opening 152, guide slot 156, assem-
`bly alignment opening 158, spring guide slot 160¢ and
`spring guide slot 1605. Spring guide 162a is shown as a
`three sided guide outwardly extending from upper face
`150 and partially surrounding spring guide slot 160a.
`Spring guide 162a is also shown having three down-
`ward sloping shoulders 170a, 172a, and 174a formed on
`each ofits three sides. Shoulder 170a is shown having
`tab 178a@ extending therefrom. Similarly, spring guide
`1624 is a three sided guide upwardly extending from
`
`8
`
`

`

`5
`upper face 150 and partially surrounding spring guide
`slot 1605 in this example. Spring guide 162is also
`shown having three downward sloping shoulders 1703,
`1726, and 174b formedon eachofits three sides. Shoul-
`der 170is shown having tab 1785 extending therefrom.
`Continuing with FIG. 3A, and the bottom view
`shown in FIG. 3B, sprocket gear 30 is shown having
`circumferential teeth 40 and pinion shaft 32. Sprocket
`gear 30 includes upper face 180 recessed therein which
`includes hub 182, and pin 186 extending therefrom for
`alignment with respective axial opening 152 and guide
`slot 156 of upper sprocket gear 28. Upper face 180 of
`sprocket gear 30 also includes assembly alignment open-
`ing 188 for alignment with assembly alignment opening
`158 of sprocket gear 28 as described in greater detail
`later herein. Flexible member 192a is shown extending
`from sectional member 196¢ on upper face 180 of
`sprocket gear 30. Tab 198a is here shown extending
`from the backside offlexible member 192a for reasons
`described later herein (also see FIG. 3D). Similarly,
`flexible member 1926 is shown extending from sectional
`member 1966 on upper face 180 and tab 198) is shown
`extending from the backside of flexible member 1925
`(also see FIG. 3D).
`Reference is now made to FIGS. 3C and 3D which
`show respective top and cross-sectional views of trans-
`fer/backlash gear 22 after upper sprocket gear 28 and
`lower sprocket gear 30 are coupled together. The actual
`assembly steps required for coupling sprocket gears 28
`and 30 togetheris described later herein with particular
`reference to FIGS. 3E-3G.
`Referring first to FIG. 3C coil spring 202¢ and coil
`spring 202are showninserted within respective spring
`guides 162¢ and 162b. The tension force from coil
`springs 202¢ and 2026 deflect upper sprocket gear 28
`from lower sprocket gear 30 and, accordingly, deflect
`gear teeth 38 from gear teeth 40 for reducing or elimi-
`nating slack between the coupling of transfer/backlash
`gear 22 from pinion gear 16 (see FIG. 4).
`Referring now to FIG. 3D, flexible member 192is
`shown including portion 202) upwardly extending from
`sectional member 1965 on sprocket gear 30 and having
`tab 1986 extending from its backside. Flexible member
`1926is also shownincluding horizontalflexible member
`2046 extending from portion 2026 and having down-
`wardly extending lip 2065. Flexible member 1926 ap-
`plies a compression force to outer face 150 of sprocket
`gear 28 for coupling sprocket gears 28 and 30 together.
`Continuing with FIG. 3D, spring guide 1626 posi-
`tions coil spring 202b between tabs 178) and 198b. Slop-
`ing shoulders 1705, 1725, and 1745 of spring guide 1626
`facilitate easy insertion of spring 202) by an assembler.
`Spring guide 162a, tab 178a, and tab 198a (located at the
`back of flexible member 192a) create moveable spring
`receptacle 212a for easy insertion of spring 202¢ by an
`assembler. Similarly, moveable spring receptacle 212
`includes spring guide 1620, tab 178), and tab 198d.
`Spring guide 1626 and circumferential gear teeth 38
`are integrally formed from upper sprocket gear 28.
`Likewise, flexible member 1925, circumferential teeth
`40, and pinion gear 32 are integrally formed from lower
`sprocket gear 30. Thus, transfer/backlash gear 22 is
`designed in an exceptionally easy to manufacture form
`which includes only two integrally formed main com-
`ponents (sprocket gears 28 and 30) having both inte-
`grally formed flexible coupling members(flexible mem-
`bers 192a¢ and 1925) and integrally formed spring guides
`(spring guides 162¢ and 1628).
`
`10
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`5,056,613
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`6
`Referring now to FIGS. 3E-3G, the assembly opera-
`tion of transfer/backlash gear 22 is described and the
`assembly advantages will become further apparent.
`Referring first to FIG. 3E, sprocket gear 28 is first
`placed over sprocket gear 30 such that: flexible member
`192a and 192are inserted through respective spring
`guide slots 160¢ and 1605; hub 182 is inserted through
`hub opening 152; and pin 186 is inserted through guide
`slot 156.
`Sprocket gear 28 is then rotated clockwise until pin
`186 rests against the left most end of guide slot 156 as
`shown in FIG. 3F. In this position, flexible arms 204a
`and 2044 slide over, and exert a compression force
`against, upper face 150 of sprocket gear 28 as shown in
`FIG. 3F. Spring guides 162a¢ and 1625 are now at a
`maximum extension for accepting respective coil be-
`tween tabs 178a and 198a is at a maximum for accepting
`coil spring 202a. Similarly, the spacing between tabs
`1786 and 1985 is at a maximum position for accepting
`coil spring 2026. In general, movable spring receptacles
`212a and 2126 are arranged for easy operator insertion
`of respective coil springs 202¢ and 2025 by the assembly
`process described above.
`Referring now to FIG.3G, tool 220 is showninserted
`through alignment opening 188 of lower sprocket gear
`30 and alignment opening 158 of upper sprocket gear
`28. This alignment process also aligns circumferential
`teeth 38 of upper sprocket gear 28 with circumferential
`teeth 40 of lower sprocket gear 30. With these circum-
`ferential teeth aligned, the assembler then inserts shaft
`34 into bushings 36¢ and 365 (FIG.1) thereby coupling
`circumferential teeth 38 and 40 to pinion shaft 16 (FIG.
`1) with minimal manipulation. Tool 220 is then removed
`from alignment openings 158 and 188 such that circum-
`ferential teeth 38 and 40 becomedisplaced from one
`another (FIG. 1, FIG. 3C-D and FIG. 4)substantially
`eliminating slack betweentheteeth of transfer/backlash
`gear 22 and pinion shaft 16. This substantial elimination
`of slack is apparent by viewing a section of the coupling
`between transfer/backlash gear 22 and pinion shaft 16
`shown in FIG. 4.
`This concludes the description of the preferred em-
`bodiment. The reading of it by those skilled in the art
`will bring to mind manyalterations and modifications
`without departing from the spirit and scope of the in-
`vention. Accordingly, it is intended that the scope of
`the invention be limited only by the following claims.
`Whatis claimed:
`1. A vehicular speed control system coupled to an
`engine throttle by transfer gearing having reduced audi-
`ble gear chatter, comprising:
`phasing means for providing a sequenceofelectrical
`phase steps in response to a comparison of actual
`vehicle speed to a desired vehicle speed;
`a stepper motor coupledto a pinion shaft for rotating
`said pinion shaft by discrete phase steps in response
`to said phasing means;
`first gear transfer means having a plurality of gear
`teeth for rotatably coupling to said pinion shaft
`with minimal slack between said gear teeth of said
`first gear transfer means and gear teeth of said
`pinion shaft; and
`transfer means coupled betweensaid first gear trans-
`fer means and the throttle for displacing the throt-
`tle in response to rotational movement ofsaid step-
`per motor.
`2. The system recited in claim 1 wherein said stepper
`motor comprises a three-phase motor.
`
`9
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`

`5,056,613
`
`7
`3. The system recited in claim 1 further comprising an
`electromagnetic clutch positioned between said transfer
`means and the throttle for disengaging and engaging
`said stepper motorfrom thethrottle.
`4. A vehicular speed control system coupled to an
`engine throttle by transfer gearing having reduced audi-
`ble gear chatter, comprising:
`generating means for generating a speed error signal
`by comparing actual vehicle speed to a set speed;
`position generating means for generating a desired
`phaseposition signal in response to said speed error
`signal;
`phasing means for providing a sequenceofelectrical
`phase steps in response to said desired phase posi-
`tion signal;
`a stepper motor coupled to a pinion shaft for rotating
`said pinion shaft by discrete phase steps in response
`to said sequence of phase steps;
`first gear transfer means having a plurality of gear
`teeth for rotatably coupling to said pinion shaft
`with minimal slack between said gear teeth of said
`first gear transfer means and gear teeth of said
`pinionshaft, said gear transfer means comprising a
`first sprocket gear coupled to a second sprocket
`gear and spring means for displacing said first
`sprocketgearrelative to said second sprocket gear;
`and
`second gear transfer means coupled betweensaidfirst
`gear transfer means andthe throttle for displacing
`the throttle in response to rotational movement of
`said stepper motor.
`5. The system recited in claim 4 wherein said phasing
`means generates said sequence of phase steps in re-
`sponse to a comparison of said desired phase position
`signal to an indication of actual phase position of said
`stepper motor.
`6. The system recited in claim 5 wherein said indica-
`tion of actual phase position is provided by counting
`means for counting said sequence of phase pulses.
`7. The system recited in claim 4 wherein said position
`generating means further comprises meansfor integrat-
`ing said error signal.
`8. A vehicular speed control system coupled to an
`enginethrottle by transfer gearing having reduced audi-
`ble gear chatter, comprising:
`generating means for generating a speederrorsignal
`by comparing actual vehicle speed to a set speed;
`sequencing means for providing a sequenceofelectri-
`cal phase steps in response to said speed error gen-
`erating means;
`a stepper motor coupledto a pinion shaft for rotating
`said pinion shaft by discrete phase steps in response
`to said sequence of phase pulses;
`first gear transfer means having a plurality of gear
`teeth for rotatably coupling to said pinion shaft
`with minimal slack between said gear teeth of said
`first gear transfer means and gear teeth of said
`pinion shaft, said first gear transfer means compris-
`ing a first sprocket gear coupled to a second
`sprocket gear by interlocking means integrally
`formedonsaidfirst sprocket gear and spring means
`coupled to said interlocking means for displacing
`said first sprocket gear relative to said second
`sprocket gear; and
`second gear transfer means coupled betweensaidfirst
`gear transfer means and the throttle for displacing
`the throttle in response to rotational movement of
`said stepper motor.
`9. The system recited in claim 8 wherein said stepper
`motor comprises a three-phase motor.
`10. The system recited in claim 8 further comprising
`an electromagnetic clutch positioned betweensaid sec-
`
`10
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`8
`ond gear transfer means and the throttle for disengaging
`and engaging said stepper motor from thethrottle.
`11. A vehicular speed control system coupled to an
`engine throttle by transfer gearing having reduced audi-
`ble gear chatter, comprising:
`generating means for generating a speed errorsignal
`by comparing actual vehicle speed to a set speed;
`position generating means for generating a desired
`phase position signal in response to said speed error
`signal;
`phasing means for providing a sequence ofelectrical
`phase steps in response to said desired phase posi-
`tion signal;
`a stepper motor coupled to a pinion shaft for rotating
`said pinion shaft by discrete phase steps in response
`to said sequence of phase pulses;
`first gear transfer means having a plurality of gear
`teeth for rotatably coupling to said pinion shaft
`with minimal slack between said gear teeth of said
`first gear transfer means and gear teeth of said
`pinion shaft, said first gear transfer means compris-
`ing a first sprocket gear coupled to a second
`sprocket gear in compression by a flexible member
`integrally formed on said first sprocket gear and
`extending through an opening in said second
`sprocket gear to apply compression to an outer
`face of said second sprocket gear, guide means
`integrally formed on said outer face of said second
`sprocket gear for alignment with said flexible mem-
`ber, and spring means inserted betweensaid flexi-
`ble memberand said guide means onsaid outer face
`ofsaid second sprocket gear fordisplacingsaid first
`sprocket gear relative to said second sprocketgear;
`and
`second gear transfer means coupled between said first
`gear transfer means and the throttle for displacing
`the throttle in response to rotational movement of
`said stepper motor.
`12. The system recited in claim 11 wherein said phas-
`ing means generates said sequence of phase steps in
`response to a comparison ofsaid desired phase position
`signal to an indication of actual -phase position of said
`stepper motor.
`13. The system recited in claim 12 wherein said indi-
`cation of actual phase position is provided by counting
`means for counting said sequence of phase pulses.
`14, The system recited in claim 11 wherein said posi-
`tion generating means further comprises meansforinte-
`grating said errorsignal.
`15. An anti-backlash gear having reduced audible
`gear chatter when coupled to a stepper motor via a
`pinion shaft, comprising:
`a first sprocket gear having circumferential teeth for
`mating with the pinion shaft and also having an
`outer face with an integrally formed flexible mem-
`ber extending therefrom;
`a second sprocket gear having circumferential teeth
`for mating with the pinion shaft and also having an
`integrally formed spring guide;
`a spring configured for insertion into said spring
`guide; and
`alignment meansforaligning said first sprocket gear
`to said second sprocket gear such that said flexible
`member exerts a tension force against said outer
`face of said first sprocket gear and said spring in
`cooperation with said alignment means displaces
`said circumferential teeth of said first sprocket gear
`from said circumferential
`teeth of said second
`sprocket gear thereby eliminating gear slack when
`coupled with the pinion shaft.
`*
`*
`*
`*
`&*
`
`10
`10°
`
`