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`US005332965A
`.
`5,332,965
`[11] Patent Number:
`United States Patent
`Wolf et al.
`[45] Date of Patent:
`Jul. 26, 1994
`
`
`[19]
`
`[54] CONTACTLESS LINEAR ANGULAR
`POSITION SENSOR HAVING AN
`ADJUSTABLE FLUX CONCENTRATOR FOR
`SENSITIVITY ADJUSTMENT AND
`TEMPERATURE COMPENSATION
`
`[75]
`
`Inventors: Ronald J. Wolf, Goshen; Larry
`Hedeen, Howe, both of Ind.
`[73] Assignee: Durakool Incorporated, Elkhart, Ind.
`.
`[21] Appl. No. 902,075
`[22] Flled!
`Jun. 22, 1992
`[51]
`Int. Cl.5 ........................ G01B 7/14; GOlR 35/00
`[52] US. Cl. ............................ 324/207.12; 324/207.2;
`_
`324/20725; 324/202$ 324/225
`[58] Field of Search ................ 324/202, 207.12, 207.2,
`324/207'21’ 20722: 20725! 225’ 173’ 174: 235
`References Cited
`
`[56]
`
`U'S' PATENT DOCUMENTS
`2,942,177 6/1960 Neumann et a1.
`.
`2,992,369
`7/1961 LaRocca .
`3,060.370 10/1962 Varterasian .
`3,112,464 11/1963 Ratajski et al.
`3,118,108
`1/1964 Zoss et a1,
`.
`3,185,920
`5/1965 Brunner .
`3’473,109 10/1969 Maaz e! a].
`3,482,163 12/1969 Peek et a1.
`3,818,292
`6/1974 Berman .
`3,933,710 10/1976 Sidor et a],
`4,066,962
`1/1978 Jaffe .
`4,086,533 4/1978 Ricouard et a1.
`4,107,604
`8/1978 Bemier -
`4,156,191
`5/1979 Knight et al.
`.
`4,293,837 10/1981 Jaffe et a1.
`.
`4,392,375
`7/1983 Eguchi et a1.
`.
`:’;;?’;;3 giggg 333:?:31‘ '
`4,829,248
`5/1989 Loubier .
`4,857,842
`8/1989 Sturman et a1. .................. 324/207.2
`
`.
`
`.
`
`.
`
`.
`
`.
`
`...................... 324/207.12
`5/1990 Juds et al.
`4,922,197
`.
`4,970,463 11/1990 Wolf et a].
`............... 324/207.12
`5,087,879 2/1992 Sugifune et al.
`FOREIGN PATENT DOCUMENTS
`0053938 6/1982 European Pat. Off.
`.
`56-107119
`8/1981 Japan .
`1416925 12/1975 United Kingdom .
`Primary Examiner—Walter E. Snow
`Attorney, Agent, or Firm—Fitch, Even, Tabin &
`Flannery
`[57]
`
`ABSTRACT
`
`An angular position sensor for sensing the angular posi-
`tion of a pivotally mounted device includes a magneti-
`cally sensitive device, such as a Hall effect IC, and a
`plurality of flux concentrators, rigidly disposed relative
`to the Hall effect IC, forming an assembly. The assem-
`bly is disposed in a housing a fixed distance from a
`rotatably mounted standard magnet defining a fixed air
`gap therebetween. The magnet is disposed in rotatably
`mounted magnet holder which also acts as a drive arm
`that is adapted to be mechanically coupled to a pivot-
`ally mounted device. The configuration of the flux con-
`centrators assembled to the magnetically sensitive de-
`vice cause the output of the Hall effect IC to be gener-
`ally linear. In order to avoid problems associated with
`electrically adjustable angular posmon sensors, the an—
`gular posttion sensor in accordance with the present
`invention is adjusted mechanically. In particular, a flux
`concentrator, preferably having a halo shape,
`is dis-
`posed adjacent the magnet. The sensor is calibrated by
`varying the distance between the halo-shaped flux con-
`centrator and the magnet. In one embodiment of the
`invention, the halo-shaped flux concentrator is formed
`to provide temperature compensation for the sensor.
`The sensor is hermetically sealed and is thus unaffected
`by wear 0’ Vlbratlon-
`
`4,893,502
`
`1/1990 Kubota et a1.
`
`.
`
`6 Claims, 5 Drawing Sheets
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`VW EX1011
`
`US. Patent No. 6,588,260
`
`VW EX1011
`U.S. Patent No. 6,588,260
`
`

`

`US. Patent
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`July 26, 1994
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`Sheet 1 of 5
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`5,332,965
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`US. Patent
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`July 26, 1994
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`Sheet 2 of 5
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`5,332,965
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`US. Patent
`
`July 26, 1994
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`Sheet 3 of 5
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`5,332,965
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`DEGREES
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`OF
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`ROTATION
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`US. Patent
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`July 26, 1994
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`Sheet 4 of 5
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`5,332,965
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`US. Patent
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`July 26, 1994
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`Sheet 5 of 5
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`5,332,965
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`ONP
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`1
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`5,332,965
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`CONTACILESS LINEAR ANGULAR POSITION
`SENSOR HAVING AN ADJUSTABLE FLUX
`CONCENTRATOR FOR SENSITIVITY
`ADJUSTMENT AND TEMPERATURE
`COMPENSATION
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`
`The present invention relates to an angular position
`sensor and more particularly to a linear non-contact
`angular position sensor for sensing the angular position
`of a pivotally mounted device, such as a throttle valve,
`which includes a magnetic sensing element, such as a
`Hall effect integrated circuit (IC) and a mechanical
`adjustment mechanism which includes integral temper-
`ature compensation that allows the sensitivity of the
`sensor to be adjusted without the need for potentiome-
`ters and the like to provide a generally linear output
`signal as a function of the angular position of the sensor
`over a relatively wide temperature range.
`2. Description of the Prior Art
`Angular position sensors are known to be used for
`various purposes including throttle position sensors for
`determining the angular position of a butterfly valve in
`a throttle body. An example of such a sensor is disclosed
`in U.S. Pat. No. 4,893,502. Such sensors are generally
`used to sense the angular position of the butterfly valve
`in the throttle body in order to control the amount of
`fuel applied to the combustion chamber of an internal
`combustion engine.
`Various sensors for monitoring the angular position
`of a pivotally mounted device, such as a butterfly valve,
`are known. For example, various contact type sensors,
`such as electromechanical potentiometers are known.
`Such electromechanical potentiometers include an ar-
`cuately-shaped thick film resistive ink resistor and a
`movably mounted precious metal electrical wiper that
`is adapted to be mechanically coupled to a butterfly
`valve such that the relative position of the wiper rela-
`tive to the resistor varies in accordance with the angular
`position of the butterfly valve. Such sensors are used to
`provide an electrical signal which varies as a function of
`the angular position of the butterfly valve
`There are various known problems with such sensors.
`For example, such sensors cannot be hermetically
`sealed due to the dynamic seal required between the
`butterfly valve shaft and the wiper inside the sensor
`housing. As is known in the art such dynamic seals are
`subject to wear over time and thus, can result in de-
`graded sensor performance in time. As such, when such
`sensors are used in a relatively hostile environment,
`such as an under-hood environment, dirt, moisture and
`chemical fumes are known to ingress into the sensor
`housing and cause degradation and erratic operation of
`the sensor.
`Some known sensors, such as the sensor disclosed in
`U.S. Pat. No. 4,893,502, avoid the problem of dynamic
`seals. More particularly,
`the ’502 patent discloses a
`modified throttle body which incorporates the sensor
`therewithin. In order to provide access to the sensor,
`the throttle body is open on one end. The opening is
`closed by a cover that is secured to the throttle body by
`way of a plurality of fasteners forming a static seal.
`However, there are known problems with such static
`seals. For example, due to the vibration of an internal
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`combustion engine, the fasteners may loosen over time,
`thus degrading the static seal and, in turn, the sensor.
`Another problem with contact type sensors is that
`they are subject to wear. In particular, the wipers are
`known to move back and forth in contact across the
`thick film resistor a relatively large number of times
`over the expected lifetime of the sensor; perhaps mil.
`lions of time. Such moving contact causes localized
`reductions of the thickness of the thick film resistor.
`Since resistance is a function of cross-sectional area, the
`reduction of the resistor thickness will change the local
`resistance value in the portion of the resistor which
`experiences‘the greatest amount of wear. As such, this
`causes drift of the output over time which affects the
`calibration and linearity of the sensor.
`There are other problems with such contact sensors.
`For example, in some situations, for instance when the
`engine is run at a nearly constant speed, engine induced
`vibration can cause additional localized resistor wear,
`which, as discussed above, can affect the calibration and
`linear output of the sensor.
`In an attempt to overcome the problems associated
`with such contact type angular position sensors, non-
`contact sensors have been developed. Moreover, due to
`the relatively hostile environment of an internal com-
`bustion engine, various magnetic sensors have been
`developed. For example, U. S Pat. Nos. 3,118,108;
`4, 392, 375 and 4,570,118 disclose magnetic angular posi-
`tion sensors which include two magnets and a magneti-
`cally sensitive device, such as a Hall effect device or a
`magneto-resistor.
`However, there are various known problems with
`such sensors which utilize two magnets. For example,
`such sensors are relatively more expensive than sensors
`which utilize a single magnet. Also, calibration of such
`sensors is relatively difficult. In particular, convention—
`ally available magnets are generally providedin quan-
`tity with tolerance ranges of about ten percent. A sec-
`ond magnet doubles the range of potential variability
`and thus makes calibration relatively more difficult.
`Other known angular position sensors avoid the prob-
`lems of two magnet sensors and utilize a single magnet
`and a magnetically sensitive device, such as a Hall effect
`device, for example, as disclosed in U.S. Pat. Nos.
`3,818,292; 3,112,464; 4,893,502 and 4,570,118. Such sin-
`gle magnet angular position sensors rely on a varying
`air gap to vary the magnetic flux density applied to the
`Hall effect device in response to angular motion. How-
`ever, the varying air gap of such sensors causes the
`output signal of the sensor to be exponential and thus
`relatively non--linear. In order to linearize the response,
`the magnets utilized with such sensors have been known
`to be formed from irregular shapes by various known
`foundry casting methods. However, such cast magnets
`are known to be rough having imperfections in their
`surfaces which contribute to part--to-p-art variation. The
`process for removing such imperfections is relatively
`time-consuming and thus adds significantly to the over-
`all cost of the sensor.
`
`Other known single magnet angular position sensors
`with a varying air gap utilize irregular-shaped magnet
`holders for skewing the position of the magnet relative
`to the rotational axis and the Hall effect element. Such
`irregular-shaped magnet holders add to the overall cost
`of the sensor and also make the sensor relatively diffi~
`cult to calibrate.
`
`Angular position sensors which utilize a single mag—
`net and a non-varying air gap are also known, for exam-
`
`

`

`5,332,965
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`3
`ple, as disclosed in US. Pat. No. 4,893,502. The angular
`position sensor disclosed therein includes a single mag-
`net and a magnetic resistance element (MRE). In this
`embodiment, a circular magnet is rigidly secured di-
`rectly to the butterfly valve shaft. The MRE is disposed
`within a modified throttle body at a fixed air gap rela-
`tive to the circular magnet. An amplifying circuit with
`variable gain is used to calibrate the sensors by way of
`potentiometers or variable resistors. As is known in the
`art, the output of such potentiometers may vary with
`temperature or time. Due to the relatively wide operat-
`ing temperature range of such a sensor in an internal
`combustion environment, for example, such potentiom-
`eters will drift and affect the overall calibration of the
`device. Another problem with such an arrangement is
`that the electrical connection between such a potenti-
`ometer and the amplifier circuit is known to be made by
`relatively large macro-scale electrical
`tracings on a
`printed circuit board which would be physically large
`enough to act as an antenna, thus making the circuit
`relatively susceptible to electromagnetic interference
`(EMI) and especially radio frequency interference
`(RFI). As such, the amplifying circuitry would have to
`be shielded which adds to the cost of the sensor.
`
`SUMMARY OF THE INVENTION
`
`It is an object of the present invention to solve vari-
`ous known problems associated with angular position
`sensors.
`
`It is yet another object of the present invention to
`provide a non-contact angular position sensor.
`It is yet a further object of the present invention to
`provide an angular position sensor that utilizes a single
`magnet.
`It is yet a further object of the present invention to
`provide an angular position sensor that utilizes a fixed
`air gap.
`It is yet another object of the present invention to
`provide an angular position sensor that provides a gen-
`erally linear output over a relatively wide temperature
`range.
`It is yet a further object of the present invention to
`provide an angular position sensor that is mechanically
`adjustable.
`It is yet a further object of the present invention to
`provide an angular position sensor with self-tempera-
`ture compensation.
`It is yet another object of the present invention to
`provide a hermetic seal for an angular position sensor
`that is virtually unaffected by wear or vibration.
`Briefly, the present invention relates to an angular
`position sensor for sensing the angular position of a
`pivotally mounted device. The angular position sensor
`in accordance with the present invention is hermetically
`sealed and thus, is virtually unaffected by wear or vibra-
`tion, and includes a magnetically sensitive device, such
`as a Hall effect IC, a plurality of flux concentrators,
`rigidly disposed relative to the Hall effect IC, forming
`an assembly. The assembly is disposed in a housing a
`fixed distance from a rotatably mounted standard mag-
`net defming a fixed air gap therebetween. The magnet is
`disposed in rotatably mounted magnet holder which
`also acts as a drive arm that is adapted to be mechani-
`cally coupled to a rotatably mounted device. The con-
`figuration of the flux concentrators assembled to the
`magnetically sensitive device cause the output of the
`Hall effect IC to be generally linear. In order to avoid
`problems associated with electrically adjustable angular
`
`4
`position sensors, the angular position sensor in accor-
`dance with the present invention is adjusted mechani-
`cally.
`In particular, an additional flux concentrator,
`preferably having a halo shape, is disposed adjacent the
`magnet. The sensitivity of the sensor is adjusted by
`varying the distance between the additional flux con-
`centrator and the magnet. In one embodiment of the
`invention, the halo-shaped flux concentrator is formed
`to provide temperature compensation for the sensor.
`
`BRIEF DESCRIPTION OF THE DRAWING
`
`These and other objects of the present invention will
`be readily understood with reference to the specifica-
`tion and the following drawings, wherein:
`FIG. 1 is a sectional view, partially broken away, of
`a throttle body with an angular position sensor in accor-
`dance with the present invention attached thereto;
`FIG. 2 is a simplified perspective view of the angular
`position sensor in accordance with the present inven-
`tion;
`FIG. 3 is a plan view of the angular position sensor
`illustrated in FIG. 2;
`FIG. 4 is a simplified plan view of the angular posi-
`tion sensor in accordance with the present invention
`illustrating the relationship between the angular posi-
`tion sensor and the magnetic flux in a static position;
`FIGS. 5 and 6 are similar to FIG. 4 and illustrate the
`relationship between the angular position sensor and the
`magnetic flux in various operating positions;
`FIG. 7 is an exemplary graph illustrating the relation-
`ship between the output voltage of the angular position
`sensor versus degrees of rotation shown in dotted line
`with a superimposed curve which illustrates the effects
`of the flux concentrators in accordance with the present
`invention;
`FIG. 8 is a perspective view of a pair of flux concen-
`trators which form a portion of the present invention;
`FIG. 9 is an elevational view of an alternate embodi-
`ment of the flux concentrators illustrated in FIG. 8;
`FIG. 10 is an elevational view of a halo-shaped flux
`concentrator which forms a portion of the present in-
`vention;
`FIG. 11 is a perspective view of one embodiment of
`a carrier assembly in accordance with the present inven~
`tion, shown with a flux concentrator removed;
`FIG. 12 is a perspective view of the assembly illus-
`trated in FIG. 11 in a further stage of development;
`FIG. 13 is a cross-sectional view of an angular posi-
`tion sensor incorporating the carrier assembly illus-
`trated in FIGS. 11 and 12; and
`FIG. 14 is an exploded perspective View of an alter-
`nate embodiment of the angular position sensor in ac-
`cordance with the present invention.
`FIG. 15 is a perspective view of a flux concentrator in
`accordance with the present invention.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`The angular position sensor in accordance with the
`present invention is generally identified with the refer-
`ence numeral 20. An important aspect of the invention
`relates to the method for adjustment. In particular, the
`angular position sensor 20 is adapted to be adjusted
`mechanically which eliminates the need for potentiome-
`ters and the like that are used to calibrate known angu-
`lar position sensors, such as the angular position sensor
`disclosed in US. Pat. No. 4,893,502. As discussed
`above, such potentiometers and the like are temperature
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`5,332,965
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`dependent. Thus, in relatively hostile temperature envi-
`,ronments, the calibration of such sensors is affected.
`As will be appreciated by those of ordinary skill in
`the art, the angular position sensor 20 is adapted to be
`used in various applications for providing a signal repre-
`sentative of the angular position of a pivotally mounted
`device. The angular position sensor 20 is illustrated and
`discussed below in an application as a throttle position
`sensor. However, it should be appreciated by those of
`ordinary skill in the art that the application of the angu-
`lar position sensor 20 in accordance with the present
`invention is also useful for various other applications.
`With reference to FIG. 1, the angular position sensor
`20 is disposed in its own housing 22 and includes a drive
`arm 24, rotatably mounted relative to the housing 22,
`that enables the sensor 20 to be mechanically coupled to
`an output shaft of a pivotally mounted device. In an
`application, such as a throttle position sensor, the drive
`arm 24 is mechanically coupled to a butterfly valve
`shaft 26 carried by a throttle body 27. More particu-
`larly, in such an application, a butterfly valve 28 is
`rigidly affixed to the rotatably mounted shaft 26 with
`suitable fasteners 30 or by spot welding. The shaft 26 is
`rotatably mounted relative to a throttle body 27 with
`suitable bearings 34.
`The butterfly valve 28 is formed to close or throttle
`the air flow to an internal combustion engine (not
`shown). By coupling the angular position sensor 20 to
`the butterfly valve shaft 26, the angular position sensor
`20 is adapted to provide a signal representative of the
`angular position of the butterfly valve 28 for use in
`controlling the amount of fuel applied to the combus-
`tion chamber in an internal combustion engine.
`It is contemplated that the shaft 26 and the drive arm
`24 be prevented from rotating relative to each other.
`Various means can be used for preventing such rotation;
`all of which are intended to be included within the
`broad scope of the invention. As shown, the butterfly
`valve shaft 26 is formed with a reduced cross-sectional
`area portion or tongue 36 which extends outwardly
`from one side of a throttle body 27 to allow engagement
`with the drive arm 24. In order to prevent the rotation
`of the tongue 36 relative to the drive arm 24, the tongue
`36 may be formed with a non-circular cross-section that
`is adapted to mate with a cooperating recess 38 formed
`in the drive arm 24.
`
`Another important aspect of the angular position
`sensor 20 is that it is formed as a separate unit that is
`adapted to rather quickly and easily be secured to, for
`example, the throttle body 27 by way of suitable fasten-
`ers 40. By providing the angular position sensor 20 as a
`separate unit, the calibration of the sensor 20 can be
`done at the factory by the sensor manufacturer. In con-
`trast, some known angular position sensors are incorpo-
`rated directly into the throttle body, for example, as
`disclosed in U.S. Pat. No. 4,893,502. In such an embodi-
`ment, calibration of the sensor is normally done by the
`throttle body manufacturer whose experience with such
`sensors is admittedly less than the sensor manufacturer.
`FIGS. 2 and 3 illustrate the basic principals of the
`angular position sensor 20 in accordance with the pres-
`ent invention. In particular, the angular position sensor
`20 includes a magnet 42, preferably a standard bar-
`shaped magnet defining opposing North and South
`magnetic poles, a magnetic sensing element 43, a pair of
`generally L-shaped flux concentrators 44 and 46 and an
`additional flux concentrator 48, used for adjustment. As
`will be discussed in more detail below, the magnet 42 is
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`adapted to be mounted in the drive arm 24 for rotation
`about an axis 50 (FIG. 1) that is generally perpendicular
`to a magnetic axis 52 which interconnects the opposing
`North and South magnetic poles, as shown in FIG. 1.
`As will be discussed in more detail below, the magnet
`42 is mounted within the drive arm 24 such that the axis
`of rotation 50 of the magnet is coaxial with the butterfly
`valve shaft 26 and generally perpendicular to the mag-
`netic axis 52 such that rotation of the butterfly valve
`shaft 26 causes rotation of the magnet 42 about the axis
`50 by a corresponding amount.
`The magnetic sensing element 43 is preferably a Hall
`effect IC with on-chip amplifier circuits, for example,
`an Allegro Model No. 3506. Since the angular position
`sensor 20 is adjusted mechanically there is no need for
`external circuitry for electrically adjusting the sensor
`20. As such, the output of the magnetic sensing device
`43 is adapted to be directly coupled to the fuel control
`circuit (not shown) for the internal combustion engine.
`By eliminating the need for external potentiometers or
`variable resistors, the need for conductive tracings on a
`printed circuit board to connect the magnetic sensing
`device 43 to such external potentiometers or variable
`resistors is eliminated. As mentioned above, the conduc-
`tive tracings in such an application can act as antennas
`and thus subject the sensor to various electromagnetic
`interference. In sensors which incorporate such external
`potentiometers or variable resistors for adjustment, for
`example, as disclosed in U.S. Pat. No. 4,893,502, the
`circuitry must be shielded against electromagnetic in-
`terferences which adds to the cost of the sensor. Such
`external potentiometers or variable resistors are also
`affected by temperature. Thus,
`in a relatively hostile
`environment, such as an under-hood environment of an
`internal combustion engine, the calibration drifts with
`temperature change. The angular position sensor 20 in
`accordance with the present
`invention solves these
`problems by using a mechanical adjustment for the
`sensor which eliminates the need for external potenti-
`ometers and the like.
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`As best shown in FIG. 13, the magnetic sensing ele-
`ment 43 is mounted stationary relative to the housing 22
`at a fixed air gap 54 relative to a surface 58 of the mag-
`net 42 that is generally parallel to the magnetic axis 52.
`The generally L-shaped flux concentrators 44 and 46
`are rigidly disposed relative to the magnetic sensing
`device 43 forming an assembly 60. In particular, the
`magnetic sensing device 43 is sandwiched between the
`generally L-shaped flux concentrators 44 and 46 to form
`the assembly 60. The assembly 60 is disposed such that
`a sensing plane 62, defined by the magnetic sensing
`element 43, is generally parallel to the axis of rotation 50
`of the magnet 42. As shown, a Hall effect IC is used as
`the magnetic sensing element 43. In such an embodi-
`ment, the sensing plane 62 is defined as a plane generally
`parallel to opposing surfaces 64 and 66, shown in FIG.
`4.
`
`As shown in FIG. 2, the assembly 60 is disposed such
`that the axis of rotation 50 of the magnet 42 is through
`the midpoint of the magnetic sensing device 43 and
`parallel to the sensing plane 62. However,
`it is also
`contemplated that the assembly 60 can be disposed such
`that the axis of rotation 50 is offset from the midpoint of
`the magnetic sensing element 43 along an axis generally
`parallel to the sensing plane 62.
`As shown in FIG. 4, the angular position sensor 20 is
`in a quiescent state. In this state the magnetic flux den-
`sity B, represented by the arrows identified with the
`
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`

`7
`reference numeral 68, is generally parallel to the sensing
`plane 62 of the magnetic sensing device 43. In this state
`the magnetic sensing element 43 outputs a quiescent
`voltage. For an Allegro Model No. 3506 Hall effect IC,
`the quiescent output voltage is typically about 2.5 volts
`DC. Rotating the magnet 42 counterclockwise as
`shown in FIGS. 5 or 6 or clockwise (not shown) causes
`an ever increasing amount of magnetic flux density 68
`to be applied to the sensing plane 62 of the magnetic
`sensing element 43 to vary the output voltage of the
`magnetic sensing element 43 as a function of an angle 9
`defined between an axis 63 parallel to the sensing plane
`62 and an axis 65. For an Allegro Model No. 3506, the
`output voltage swing is approximately $2.0 volt DC
`depending on the direction of the angular rotation.
`In accordance with an important aspect of the inven-
`tion, the relationship between the axes 63 and 65 can be
`varied in order to adjust the offset voltage of the sensor
`20. In particular, the assembly 60 is rotated relative to
`the magnet 42 in a quiescent state to adjust the sensor
`offset voltage. In such an application, the sensor would
`be configured in the quiescent state to have a small
`angle 6 between the axes 63 and 65 as illustrated in FIG.
`4.
`
`As will be discussed in more detail below, an impor-
`tant aspect of the invention relates to the fact that the
`output voltage of the angular position sensor 20 varies
`linearly as a function of the angular rotation of the
`magnet 42. As such, the output voltage of the angular
`position sensor 20 can be applied directly to the fuel
`consumption circuit for the internal combustion engine
`without the need for additional and expensive external
`circuitry. In particular, known angular position sensors
`have utilized various circuitry including microproces-
`sors to linearize the output voltage, which adds to the
`complexity and cost of the sensor. The angular position
`sensor 20 in accordance with the present
`invention
`eliminates the need for such external circuitry. In par-
`ticular, the output signal
`is linearized by way of the
`generally L-shaped or book-end type flux concentrators
`44 and 46, which not only direct the magnetic flux and
`control the density and polarity of the magnetic flux
`density but also linearize the output signal
`to near
`straight line form. As such, the angular position sensor
`20, in accordance with the present invention, is adapted
`to be substituted for potentiometer-type throttle posi-
`tion sensors which are contact devices with a finite life.
`More particularly, FIG. 7 illustrates a graph of the
`output voltage of the angular position sensor 20 as a
`function of the degrees of rotation. The solid line 72
`represents the output of the angular position sensor 20
`without the book-end shaped flux concentrators 44 and
`46. As shown, the output voltage of such an embodi-
`ment varies relatively non-linearly relative to the de-
`grees of rotation. By incorporating the book-end shaped
`flux concentrators 44 and 46, the output voltage of the
`angular position sensor 20 becomes fairly linear. More
`particularly, the solid line 74 represents the desired
`relationship between the output voltage of the angular
`position sensor 20 versus the degrees of rotation of the
`magnet 42. The dashed line 76 represents the output
`voltage of the sensor 20 which incorporates the book-
`end shaped flux concentrators 44 and 46. As illustrated,
`the dashed line 76 is fairly linear over the anticipated
`operating range of the sensor, for example,
`llO° rota-
`tion.
`
`The book-end shaped flux concentrators 44 and 46
`are formed from a magnetically soft material — a mag-
`
`5,332,965
`
`8
`netically permeable material which does not retain re-
`sidual magnetism. Various configurations of the book-
`end shaped flux concentrators 44 and 46 are contem-
`plated, for example, as shown in FIGS. 8 and 9. Refer-
`ring to FIG. 8, the book-end flux concentrators 44 and
`46 are formed in a generally L-shape defining two de-
`pending leg portions 78 and 80. The outer intersection
`of the depending legs 78 and 80 defines a heel portion
`82. The inner intersection of the depending legs 78 and
`80 defines a generally arcuately-shaped inner portion
`84. It is also contemplated that the inner portion 84 may
`be formed such that the depending leg portions 78 and
`80 are virtually perpendicular at the point of intersec-
`tion or have a predetermined radius of curvature as
`illustrated in FIG. 8. In the preferred embodiment illus-
`trated in FIG. 9, the flux concentrators 44 and 46 are
`formed in a similar manner as the flux concentrators
`illustrated in FIG. 8 but with the heel portion 82 re-
`moved and a relatively larger radius of curvature for
`the inner portion 84.
`In accordance with another important aspect of the
`invention, the sensor 20 allows the sensitivity (e.g.,
`volts/degree of rotation) of the sensor 20 to be adjusted
`mechanically. As discussed above, various known sen-
`sors utilize potentiometers or variable resistors and the
`like for varying the sensitivity of the sensor. However,
`such sensors are relatively temperature dependent.
`Thus,
`in a relatively hostile environment where the
`temperature is anticipated to vary over a relatively wide
`range, the calibration of such sensors is known to drift.
`The angular position sensor 20 in accordance with the
`present invention solves this problem by providing a
`method for mechanically adjusting the sensitivity of the
`sensor without the need for potentiometers and the like.
`In particular, an additional flux concentrator 48 is pro-
`vided. Although the flux concentrator 48 is described
`and illustrated having a halo or washer shape, as illus-
`trated in FIG. 2, for example, it is to be understood that
`various shapes for the flux concentrator 48 are contem-
`plated. For example, a rectangular shape may be used
`for the flux concentrator as illustrated and identified
`with reference numeral 48’ in FIG. 15. In such an em-
`bodiment, various means within the ordinary skill in the
`art are contemplated for supporting the flux concentra-
`tor 48 relative to the magnet 42.
`In the preferred embodiment, the flux concentrator
`48 is formed in a generally circular or halo shape with a
`centrally disposed aperture 86. The flux concentrator 48
`is adapted to be disposed such that the midpoint of the
`aperture 86 is generally coaxial with the axis of rotation
`50 of the magnet 42. The sensor’s sensitivity is adjusted
`by varying the distance between the flux concentrator
`48 and the magnet 42 in an axial direction relative to the
`axis of rotation 50 as indicated by the arrows 88 (FIG.
`2). It is contemplated that the plane of the flux concen-
`trator 48 be generally parallel to the plane of the magnet
`42. The halo--shaped flux concentrator 48 thus provides
`a mechanical and relatively stable method for adjusting
`the sensitivity of the sensor 20 utilizing a relatively
`inexpensive and until now often impractical class of
`linear IC; impractical because of the relatively wide
`range of part-to-part electrical output values of offset
`voltage and sensitivity per gauss.
`In an alternate embodiment of the invention as illus-
`trated in FIG. 10, it is contemplated that the flux con-
`centrator 48 be formed to be self-temperature compen-
`sating. In this embodiment, the flux concentrator 48
`may be formed in a plurality of layers. Three layers are
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`

`

`9
`shown for example. The outer layers 90 are formed
`from a first material, for example, an iron—nickel alloy
`comprised of approximately 29%—33% nickel. The
`inner layer 92 is formed from low carbon steel, for
`example, C1008 low carbon steel. With such an embodi-
`ment, the properties of the nickel alloy used in the outer
`layers 90 cause the permeability of the outer layers 90 to
`decrease with an increase in temperature which de-
`creases the ability of the flux concentrator 48 to concen-
`trate magnetic flux as a function of temperature. Thu