JPH0755416A - Position sensor using magnetoresistance body and complementary target - Google Patents

Abstract

PURPOSE: To provide a magnetic sensor capable of accurate detection. CONSTITUTION: The position sensor has a magnetic resistance circuit on a first plane, the first part of the circuit being located on one side of a first shaft, the other part of the circuit on the other side of the first shaft. A movable member 10 having two target tracks 12, 14 is designed to rotate with respect to a central axis generally parallel to the first plane. The two target tracks 12, 14 are separated by a second plane generally perpendicular to the first plane and coinciding with the first shaft. The first and second target tracks 12, 14 comprise pluralities of first and second parts arranged in complementary fashion so that the magnetic part of the first track 12 is placed adjacent and opposite to the nonmagnetic part of the second track 15. The motion of the first and second parts passing the sensor varies the resistance of part of the circuit and issues an output signal showing the position of a rotating member 10 with respect to the sensor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to position sensors, and more particularly to monitoring magnetic field distortions acting on the resistance of magnetoresistive elements to detect magnetic and non-magnetic portions of two target tracks that are complementary to each other. The present invention relates to a position sensor that detects a position.

[0002]

Many different types of position sensors are known to those skilled in the art. Some position sensors utilize magnetically sensitive components such as Hall effect or magnetoresistive components to sense changes in magnetic field strength and direction in response to the presence of ferromagnetic materials. U.S. Pat.No. 4,970,463 issued to Wolff et al. On November 13, 1990, is a ferrous object capable of sensing the presence or absence of highly permeable objects such as teeth or notches on a rotatably mounted zero speed iron wheel. A sensor assembly is disclosed. The sensor assembly comprises a permanent magnet and a flux sensitive transducer having a sensing surface that produces an electrical output signal that varies as a function of changes in magnetic flux density. Iron sensor assemblies do not rely on pole face magnetism like some known conventional sensors, but instead rely on the radiant component of the magnetic flux density emanating from the face of the magnet between the facing pole faces.

US Pat. No. 4,992,731, issued to Lorenzen on February 12, 1991, discloses a rotation using a Hall cell that is sensitive to changes in the tangential component of the magnetic field caused by the intermittent surface features of the permanent magnets and rotating elements. A speed sensor system is disclosed. To avoid deviations caused by changes in the baseline value of the tangential component of the magnetic field, the output of the differential amplifier supplied by the Hall cell is connected to a voltage averaging circuit which stores the average voltage of the output in a single capacitor.

US Pat. No. 5,041,784, issued to Griebera on August 20, 1991, discloses a magnetic sensor having a rectangular magnetostrictive flux bar. The sensor is used to measure the position, velocity or direction of movement of an object having alternating magnetic conduction zones with a permanent magnet member having a pole face facing the moving object and an axis transverse to its direction of movement. A highly permeable ferromagnet strip is fused coaxially to the surface of the magnet. It has a length dimension in the direction of movement greater than a width dimension transverse to the direction of movement of the object. The ferromagnet strip distorts the magnetic field of the permanent magnet member in the area of the pair of sensor elements such that the magnetic flux lines in the area of each sensor are biased transversely with respect to the direction of movement of the object. The magnetic flux field in the area of each sensor is uniform.

US Pat. No. 4,086,533 issued to Ricard et al. On April 25, 1978 describes a Hall effect device for determining the angular position of rotating parts. It comprises first and second parallel arranged magnets forming a symmetrical circuit with axially arranged Hall effect elements. The rotating part has first and second elements made of soft magnetic material angularly arranged to alternately pass through the first and second magnets, respectively, and first and second Hall effect elements. To produce transverse magnetic field components in opposite directions. This produces a signal with the polarity reversed to indicate the angular position of the rotating part.

A paper entitled "Magnetic Resistance Sensor" was published in the Autumn 1987 issue of "Scientific Honeyweller". This paper was written by Baharat B. Punt and describes many different characteristics of magnetoresistive sensors, including the adaptation of several different sensors used in particular applications.

US patent application 07 / 952,449, filed September 29, 1992 and assigned to the assignee of the present application, discloses a gear sensor with a magnet such as a Hall effect element and two magnetically sensitive devices. Disclosure. The two magnetically sensitive devices are arranged on a common plane with one another, one of which is closer to the magnet than the other. The common surface on which the two magnetic sensitive devices are arranged is separated from the central axis of the magnet by a predetermined distance. Means are provided for determining the ratio of magnetic field strengths imposed vertically on the first and second magnetically sensitive devices, the ratio being used to distinguish between the tooth and the groove in proximity to the sensor.

US Patent Application 08 / 032,883 (M10-1500) filed March 18, 1993 and assigned to the assignee of the present application.
0) describes a magnetic sensor consisting of two target tracks which are associated generally parallel to each other. Each track consists of magnetic and non-magnetic parts arranged in an alternating pattern. Each magnetic portion of the first track is located along a side of the non-magnetic portion of the second track, and each magnetic portion of the second track is located along a side of the non-magnetic portion of the first track. To do. The first and second magnetically sensitive components are located proximate to the first and second target tracks, respectively, and the magnetic field source is proximate to the first and second magnetically sensitive components. The perpendicularly imposed magnetic field distortions for the first and second magnetically sensitive components are used to provide first and second output signals. A third output signal as a function of the first and second output signals is used to determine the position of the first and second target tracks with respect to the first and second magnetically sensitive components.

[0009]

Many types of position sensors allow the distinction between two different parts, such as the teeth or grooves of a rotating member, without having to move the rotating member before making a determination. This is very important. This is called the power-up cognitive ability to sense the position of the target before it moves. For example, when monitoring a gear having teeth and grooves with a position sensor, it would be very useful if the sensor could determine if the teeth or grooves were located adjacent to the sensor without having to rotate the gear. The present invention aims to realize this.

[0010]

A position sensor made in accordance with the present invention includes a first and second magnetic field disposed on a first surface and located on a first and a second side of a first axis, respectively. It consists of a resistance component. The sensor further includes a moveable member having first and second target tracks. Each first and second target track comprises a plurality of first portions and a plurality of second portions, each of the first portions of one target track being one of the second portions of the other target track. Placed adjacent to one. The first target track is located on the first side of the second surface, the second target track is located on the second side of the second surface, and the first axis is on the first and second surfaces. It is located at the intersection of. Embodiments of the present invention further include means for providing a first signal that is a function of the relative resistances of the first and second magnetoresistive elements. The first signal indicates the position of the movable member.

In the most preferred embodiment of the present invention, the magnetoresistive component comprises a magnetically sensitive element made from a nickel-iron alloy such as permalloy. The first, second, third, fourth magnetically sensitive elements can be arranged in a Wheatstone bridge configuration to sense changes in resistance. In the most preferred embodiment of the present invention, the first and third magnetically sensitive elements are electrically connected in series between the first and second circuit points. 2nd 4th
Magnetically sensitive elements are electrically connected in series between the first and second circuit points, and the first and third magnetically sensitive elements are electrically parallel to the second and fourth magnetically sensitive elements. Connect to. When the movable member rotates about a central axis parallel to the first surface and generally perpendicular to the second surface, the first and second target tracks are rotated.
The portions of move sequentially in close proximity to the first and second magnetoresistive components and affect the magnetic field created by them by the permanent magnets. This change in the shape of the magnetic field changes the resistance of the components and can sense the voltage difference between two selected points in the Wheatstone bridge configuration. The use of complementary targets, such as first and second target tracks, causes the magnetic material to move to a position on one side of the first and second magnetoresistive components while at the same time forming another magnetic member. Moving the device away from the opposite position facilitates operation of the device.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENT In the following description of the embodiments, similar components are designated by similar reference numerals. FIG. 1 shows a rotating member 10 having two target tracks 12,14. The two target tracks are complementary to each other and each tooth of one track is located close to the groove of the other track. For example, the tooth 16 of the second target track 14 is a groove of the first target track 12.
Proximity to 17, the teeth 18 of the first target track 12 are
It is close to the groove 19 of the target track 14. The advantages of this type of configuration will be described in detail later.

In FIG. 1, a permanent magnet 20 is further arranged in proximity to four magnetoresistive elements arranged on a silicon substrate mounted on a ceramic substrate. It should be noted that while the magnetoresistor is placed on a silicon substrate in the embodiment of the invention, the magnetoresistor can be placed on another non-conducting surface in other embodiments of the invention. As the target track rotates about axis 26, the teeth and grooves move sequentially through the magnetoresistor 44 on the ceramic substrate 22. Due to the complementary construction of the target track, when the tooth is located on one side of the magnetoresistor 44, the groove is located on the opposite side and vice versa.

FIG. 2 is a side view of the rotating member 10. As can be seen, the axis of rotation 26 is perpendicular to the plane of FIG. Due to the complementary relationship of the two target tracks 12, 14, the teeth of the second target track 14 are aligned with the grooves of the first target track 12. For example, the teeth 30 in the first target track 12,
Between 32, tooth 34 is visible through the gap between teeth 30, 32.
Similarly, the tooth 32 of the first target track 12 is located adjacent to the groove between the teeth 34, 36 of the second target track 14. Dashed line 40 indicates the position of the spacers located between the two target tracks 12,14. Although the embodiments of the present invention incorporate spacers to position the magnetoresistor at a preselected distance from the moveable magnetic teeth, the use of spacers is optional and in all embodiments of the present invention. It should be understood that it is not necessary.

FIG. 3 is an end view of FIG. 2, in which a permanent magnet 20, a ceramic substrate 22, and a magnetic resistor 44 are added. In Figure 3,
The first target track 12 and the second target track 14 are central axes
It is configured to rotate about 26 and alternate so that the grooves are on one side of the magnetoresistor 44 and the teeth are on the opposite side.
The target track teeth and grooves are sequentially arranged on opposite sides of the magnetoresistor 44.

To further illustrate the interaction between the magnetoresistor and target track teeth and grooves, FIG. 4 illustrates two linearly deployed target tracks 12, 14 instead of a circular pattern. Arrows A and B indicate magnetic resistor 44 and ceramic substrate
The driving direction of the target truck with respect to 22 is shown. Figure 3
For the sake of consistency with FIG. 4 and FIG. 4, the magnetoresistive element 44 is indicated by a dotted line to show the first and second target tracks under the ceramic substrate 22.
It is placed so that it faces 12 and 14. For simplicity,
Permanent magnet 20 is not shown in FIG.

In FIG. 4, reference numeral 50 is used to indicate the target track magnetic teeth, and reference numeral 52 is used to indicate the groove between the target track teeth 50. When the target track is in the position shown in FIG. 4, there are teeth 50 on the left side of the magnetoresistor 44,
The groove 52 is shown on the right. Two target tracks 12, 14
Move vertically in the directions indicated by arrows A and B, the magnetoresistive
On the right side of 44 the tooth 50 replaces the groove 52 and on the left side the groove 52
Replaces 50. When the target track continuously moves in the direction shown by the arrow in FIG.
The tooth 50 changes to the left side, and the groove 52 changes to the tooth 50 on the left side.

To further explain the principles of the present invention, FIG.
A, B, and C show the effect on the direction of the magnetic flux lines produced by the exemplary permanent magnet 20 and teeth 50. Note that in FIGS. 5B and C, the tooth 50 is shown schematically as a rectangular box and is not shown attached to the complete target track. It is assumed that the magnetic flux lines 60 indicate the magnetic field generated by the permanent magnet 20. Figure 5
The purpose of A, B, C is to show the action of the magnetic material as indicated by reference numeral 50 on the direction of the magnetic field of the permanent magnet 20, and in particular the first
To show the effect on the magnetic field in plane 70 of. Figure 5A
Shows permanent magnet 20 having its magnetic field 60 in the general form in which permanent magnet 20 is unaffected by an external magnetic material. FIG. 5A is shown together with FIGS. 5B and 5C so that the effect of the magnetic field on the direction of the magnetic flux lines can be seen for comparison.

FIG. 5B illustrates the effect on the magnetic field 60 caused by a magnetic material such as teeth 50 proximate permanent magnet 20. As can be seen, the left line 62 of the permanent magnet 20 is slightly affected by the presence of the tooth 50, resulting in
In B, it is slightly more vertical than the magnetic flux lines in the same place in FIG. 5A. On the other hand, the magnetic flux line 64 on the right side of the permanent magnet 20 in FIG. 5B is a portion near the permanent magnet 20, and is considerably affected by the magnetic member, that is, 50.

FIG. 5C illustrates a situation opposite to that shown in FIG. 5B. With the magnetic body or tooth 50 on the left side of the permanent magnet 20 and no magnetic body on the right side, the magnetic flux lines 62 are considerably deformed by the magnetic body, and the magnetic flux lines 64 on the right side of the permanent magnet 20 are slightly deformed. , FIG. 5C is more vertical than the corresponding flux lines of FIG. 5A.

It can be seen from FIGS. 5B and 5C that the presence of the magnetic material distorts the direction of the magnetic field of the permanent magnet, and as a result changes the magnitude and direction of the magnetic field component in the first surface 70. Utilizing the deformation of the magnetic field and the corresponding change in magnetic field strength measured at the first surface 70, the presence of a magnetic body is detected and the magnetic body on the first or second side of the Wheatstone bridge configuration of the magnetoresistor is utilized. The position can be identified.

FIGS. 6A, 6B, 7 and 8 show the magnetic field at the first surface with the magnetoresistors arranged under several different conditions. In FIGS. 6A, 6B, 7, and 8, the arrows indicate the direction and strength of the magnetic field provided by the permanent magnet 20 within the first surface 70. In other words, the long arrows show stronger magnetic field components in the first plane 70 than the short arrows, and the directions of all the arrows show the direction of the magnetic field at their selected position. Reference numeral 81 indicates an axis parallel to the traveling directions of the first and second target trucks. The first axis 81 lies between the two pairs of magnetoresistors. The first axis 81 lies in the first plane in which the magnetoresistor is also arranged. Those configurations will be described in detail below.

In FIGS. 5A and 6A, the arrow in FIG. 6A indicates the first surface when the magnetic substance or the tooth is not close to the permanent magnet 20.
Note that it indicates the magnitude and direction of the magnetic field components within 70.
As can be seen from FIG. 6A, the magnetic field strength is slightly greater at points further away from the first axis 81 than at points closer to the first axis 81. The reason for this difference in the magnetic field strength within the first surface 70 is that the magnetic flux lines extending through the first surface 70 near the first axis 81 are more distant from the first axis 81. First side
Because it is more vertical than what extends through 70. This change in the angle of the magnetic flux lines increases the component of the magnetic field in the first surface 70. Further in FIG. 6A, it can be seen that the size and direction of each representative arrow is symmetrical about the first axis 81.

It can be seen in FIGS. 5B and 6B that the arrow in FIG. 6B is slightly different from that in FIG. 6A. This deformation of the magnetic field is caused by the presence of the teeth 50 close to the permanent magnet 20. FIG. 6B shows an analytical simulation in which the wide teeth run on the right side of the permanent magnet 20 and the wide grooves run on the left side.

6A and 6B, it can be seen that the magnetic field strength component to the right of the first axis 81 is increased in FIG. 6B over that of FIG. 6A. This is caused by the deformation of the magnetic field by the wide teeth located on the right side of the device of FIG. 6B which reduces the perpendicularity of the magnetic flux lines to the first surface 70. By illustration of the two sides of FIGS. 6A and 6B, it can be seen that some of the arrows in FIG. 6B are significantly reduced in length as the magnetic flux lines in those regions are vertical. A part of the arrow on the left side of the first shaft 81 is reversed in direction, and is directed outward from the first shaft 81 in FIG. 6A, whereas it is directed toward the first shaft 81 in FIG. 6B. . In certain circumstances, the action of the tooth 50 changes the magnetic flux lines to the left of the first axis 81 from slightly non-vertical leftward to slightly non-vertical rightward. This effect can be seen in Figure 6B.

FIG. 7 shows the operation when the narrow groove is on the left side of the first shaft 81 and the narrow tooth is on the right side.
It should be noted that the teeth and grooves are only one of many different shapes that can be used in connection with a device such as the present invention. The teeth can be narrow or wide, and the corresponding grooves can be narrow or wide. It is determined that the wide-width tooth has a larger effect on the distortion of the magnetic field than the narrow-width tooth because the amount of the magnetic material forming the wide-width tooth is large.

FIG. 8 shows that the moveable object has its teeth away from near the first axis 81 on one side of the line 160 and the other tooth close to the first axis 81 on the other side of the first face 70. 6 illustrates the effect of the combination of two different teeth and grooves on the magnetic field of the first surface 70 during the transition. In FIG. 8, the two teeth 50 move in a direction parallel to the first axis 81 shown by the arrow. On the right side of the first axis 81, it can be seen that the arrow at the bottom of the figure is longer than that at the top of the figure. This is a magnetic body or tooth
The attractive force of 50 and the change in its angle as the magnetic flux lines extend through the first surface 70. A similar effect can be seen in the upper left part of FIG. 6A, 6B, 7, 8 the magnetic field component of the first surface 70 is affected by a magnetic material such as the tooth 50, which causes a measurable distortion of the magnetic field strength at various locations on the first surface 70. .

FIG. 9 shows a permanent magnet 20 and a ceramic substrate 22.
And the spacer 77 arranged between them. Magnetic resistor
The surface of the ceramic substrate 22 on which 44 (not shown in FIG. 7) is placed is shown by the dotted line 70 and was described above as the first surface. Point 81
The first axis indicated by is perpendicular to the plane of FIG. 9 and lies within the first plane 70. The second surface 82 extends between the two target tracks 12, 14 and is generally perpendicular to the first surface 70. For purposes of describing the construction of the present invention, the first axis 81 coincides with the point of intersection between the first and second surfaces 70,82. Further, it can be seen that the axis of rotation 26 is generally parallel to the first surface 70.

In FIG. 9, compared with FIGS. 5A, 5B and 5C,
It can be seen that the thickness of the spacer 77 changes the distance between the magnetic pole surface of the permanent magnet 20 and the first surface 70, and thus affects the size of the magnetic flux lines on the first surface 70. The thickness of the spacer 77 is the first surface
To determine the desired strength of the magnetic field component at 70, it can be specifically selected for a particular application of the invention. It should be clearly understood that the spacer 77 is useful in certain embodiments of the invention, but is not absolutely necessary in all possible configurations of the invention.

With continued reference to FIGS. 5A, 5B, 5C and FIG. 9, the teeth 50 pass through one or the other of the magnetoresistors 44 to extend through the first surface 70 to the magnetoresistors 44. It can be seen that it affects the direction of the acting magnetic flux lines. Depending on which side of the second surface 82 the tooth is closer to the magnetoresistor 44, the magnetic field is distorted by its presence, which distortion of the magnetic field can be sensed by the change in resistance of each magnetoresistor 44. . As detailed above, the effect sensed in the present invention corresponds to the change in magnetic field strength measured at the first surface 70. First
This change in magnetic field strength at plane ₇₀ is caused by a change in the angular relationship between the magnetic flux lines and the first plane. If the angular relationship between the magnetic flux lines and the first surface is made less perpendicular, the magnetic field component at the first surface will increase and, conversely, the magnetic flux lines will become more perpendicular with respect to the first surface 70. If so, their composition at the first surface 70 is reduced.

To illustrate one particular embodiment of the present invention, FIG. 10 illustrates a well known configuration of a Wheatstone bridge configuration resistor. A voltage Vs is applied across the bridge to measure the output voltage difference between the first voltage V1 and the second voltage V2. When the resistors RA and RD are linked so as to be similarly actuated by a magnetic field stimulus, and the resistors RB and RC are linked so that they are similarly actuated by a magnetic field stimulus, etc. Can be easily measured. The resistors RA and RD are arranged on one side of the first shaft 81,
When the resistors RB and RC are arranged on the second side of the first shaft 81,
They are reciprocally affected by the sequential movement of the teeth and grooves through the left and right positions of the magnetoresistor. 5A, 5
Due to the magnetic field distortion described above for B and 5C, FIG.
The change in resistance of each of the resistors can be sensed.
In the Wheatstone bridge configuration of FIG. 10, the first voltage V
If 1 is equal and equal to the second voltage V2, a change in the resistance of the resistor will raise the voltage across resistors RA and RD and likewise lower the voltage across resistors RB and RC, or vice versa. Become. As each resistor changes to increase, the first voltage V
The change in voltage between 1 and the second voltage V2 changes as a percentage of the supply voltage Vs at the same rate as the incremental resistance change to the original resistance of any of the four resistors shown in FIG.

It should be noted that many other configurations of resistors are possible within the scope of the invention. For example, resistors RA and RD
Can be a magnetic resistor, and the resistors RB and RC can be resistors having constant values. Alternatively, all of the resistors in Figure 10 could be magnetoresistors, as described above.

FIG. 11 shows another structure of the present invention. Two magnetic resistors RA and RB are arranged on the opposite sides of the first shaft 81 and electrically connected in parallel as shown in FIG. . Two constant current sources A1 and A2 are provided as shown, and the first voltage V1 and the second voltage V2 can be measured to determine the change in resistance of the two magnetoresistors.

To describe one embodiment of the present invention, the Wheatstone bridge configuration of FIG. 10 will be described with the physical layout of the resistors of the particular chip shown in FIG. The resistors shown in FIG. 12 are generally arranged in a serpentine, nested relationship. In FIG. 12, each of the four magnetoresistive bodies comprises a plurality of bars. To identify each of the four magnetoresistors, the conductive pads that connect the vertical bars of each of them together are indicated by a letter indicating the associated magnetoresistor. Figure 10,
With reference to 12, resistor RA is comprised of a plurality of vertical parallel bars of various sizes interconnected with a plurality of conductive pads identified as RA to indicate its connection to similarly identified resistors. , The conductor 102 and the conductor of FIG.
Forming a meandering pattern connected between 104. Thus, resistor RA is connected between circuit point 90 and circuit point 93 of FIG. 10, identified as a connection pad on the ceramic substrate of FIG. The resistor RA consists of a vertical bar connected to the pad RD on the one hand and is nested with the resistor RD connected between the pads 106 and 108. In this particular embodiment of the invention, the circuit shown in FIG. 12 is intended to be implemented with two jumper connections. 1
One jumper connection is the dotted line 91 between pads 106 and 112.
, The other jumper connection is pad 108 and pad 114
It is indicated by a dotted line 92 between. Jumper connections 91, 92 correspond to circuit points in FIG. 10 identified by the same reference numerals. By comparing the reference numerals and letters in FIGS. 10 and 11, it can be seen that voltage is provided at circuit point 90 and pads 108, 114 are electrically connected to ground. Further, the jumper connection 91 is connected between the resistors RB and RC, and the circuit point 93 is connected to the resistors RA and RD.
You can see that they are connected between.

Further in FIG. 12, the purpose of the serpentine nesting of the resistors is to accommodate different magnetic field strengths in the plane of the ceramic substrate resulting from the shape of the magnetic field emanating from the permanent magnet 20. The magnetic pole surface of the magnet is directly below the substrate shown in FIG. 12, and the magnetic field extends upward through the surface of the resistor, so that the magnetic field strength in the region closest to the first axis 81 is away from the first axis 81. It is usually less than the magnetic field strength at a given point. This effect can be seen in Figures 6-8. To accommodate this expected difference in magnetic field strength in the plane of the resistor, the width of the resistor section closest to the first axis 81 is greater than the width of the same resistor section away from the first axis 81. Has become. The reason for nesting resistor pairs is to try to make the magnetic effect on one of each pair of resistors as identical as possible to the magnetic effect on the other of those two pairs. In other words, the Wheatstone bridge arrangement shown in FIG. 10 works most predictably when the resistors RA, RD are nested such that they each generally experience similar magnetic effects due to the magnetic field.

In FIG. 12, the first surface 70 shown in FIG. 7 is generally coplanar with the four magnetoresistors RA, RD, RB, RC of FIG. Also shown in FIG. 12 is a first shaft 81. The second surface 82 is perpendicular to FIG. 12 and the first axis 81 lies within the first and second surfaces.

FIG. 13 illustrates a concept well known to those skilled in the art. If the arrow B in FIG. 13 indicates the direction and magnitude of the magnetic field passing through the first surface 70 at the point 128, the effective magnetic field strength of the magnetic field component of the first surface 70 is indicated by the arrow X. When the magnetic field is redirected as shown by arrow B ', the effective magnetic field component at the first surface 70 increases as shown by arrow X', where X'is a point 128 within the first surface 70. From that point to point 130). As can be seen from FIG. 13, the decrease in the perpendicularity of the magnetic flux lines increases the effective component on the first surface 70, whereas the increase in the perpendicularity of the magnetic flux lines reduces the component on the first surface 70. Will be done. This is why arrow X'becomes longer than arrow X even though arrow B'and arrow B are generally equal to each other. When a magnetic material such as the tooth 50 passes one side of the second surface 82, the magnetoresistor on the side of that surface is first
At surface 70 of the, one experiences an increase in the magnetic field strength, which is generally perpendicular to their total length of line segments, as shown in FIG. 12 and 13, when the magnetic substance passes through the resistors RB and RC but does not pass through the resistors RA and RD, the two resistors on the right side of the first shaft 81 in FIG. Experienced, the two resistors to the left of the first axis 81 experience their action to a much lesser degree. The resistance of the resistors RB, RC is reduced in certain increments. Bridge configuration thus resistor RB as shown in FIG. 10, reduction of the RC of the resistor reduces the first voltage V1, to increase the second voltage V _2. This increase in the differential voltage between the two sensing points of the bridge reflects the presence of magnetic material on the right side of the ceramic substrate and the absence of magnetic material on the left side of the magnetic substrate.

FIG. 14 is a graphical representation of the resistance of magnetoresistor 120 as a function of magnetic field strength HT transverse to its easy axis. In applications such as those described above, the magnetoresistor 120
A current I flowing through the magnetic field flows in a direction generally parallel to the easy axis of magnetization, and the effect of the transverse magnetic field on the resistance is illustrated in FIG. The magnetic field strength is measured in Gauss and the family of curves shown in FIG. 14 shows various different widths W of the magnetoresistor 120. As can be seen from the figure, the resistance of the magnetoresistor 120 increases as the strength of the magnetic field HT across the magnetoresistor 120 increases and its maximum value RMA.
The value decreases from X to about 98% of the maximum value.

FIG. 15 shows the relationship between the resistance of the magnetic resistor 120 and the direction of the external magnetic field HE. The family of curves shown in FIG. 15 shows various angles between the external magnetic field HE and the axis of the magnetoresistor 120. When the magnetic field HE is generally aligned with the direction of current flow through the magnetoresistor 120, the magnetoresistor 120 maximizes its resistance. As the angle q increases, the magnetic resistance 12
The zero resistance decreases from its maximum value RMAX to a value of about 98% of its maximum value. This change in the resistance of the magnetoresistor in response to changes in both magnitude and effective angle of the magnetic field allows monitoring the magnitude and direction of the magnetic field by sensing the change in resistance of the magnetoresistor in the Wheatstone bridge. Will be possible.

FIG. 16 shows an empirical test of one embodiment of the present invention. In FIG. 16, two curves 140 and 144 are shown. One curve 140 shows the effect on the sensor bridge output, measured in millivolts, produced by the target rotation with multiple complementary teeth and grooves. As the rotatable member moves about its axis of rotation, it is exposed to magnetic teeth on one side of its first axis 81 and then to the teeth on opposite sides of its first axis in the present invention. . Note that the use of the positive and negative voltage magnitudes in FIG. 16 is relative and depends on the configuration of the tooth and the groove considered to be the positive position. Figure 1
An important aspect shown in FIG. 4 is that the zero cross is relatively consistent and does not depend on the gap between the first surface 70 and the magnetic tooth. For example, curve 140 in FIG. 16 shows the results obtained with a 0.020 inch gap and curve 144 shows the results obtained with a 0.080 inch gap. The gap is defined by the reference letter G in FIG. As can be further seen in FIG. 14, the present invention provides a device exhibiting a property known to those skilled in the art as power-up recognition capability. This is shown by the fact that the polarity of the output signal from the Wheatstone bridge of the magnetoresistor gives an immediate indication of the position of the moving object without having to move the moving object. In other words, by monitoring the polarity of the output signal from the bridge, the relevant circuit immediately determines if the tooth is on the left side of the bridge and the groove is on the right side, or alternatively, the tooth is on the right side of the bridge and the groove is on the left side. Can be determined.

Further, in FIG. 16, the information shown in the area between 0 and 12 degrees indicates that the teeth of the second target track 14 are close to the magnetoresistive element and the gap or groove of the first target track 12 is magnetic. The rotating part when approaching a resistor is shown. This causes resistors RA, RD to experience increased resistance due to the effects described above in connection with FIG. In the rotation of about 12 degrees indicated by the dotted line 150,
First target track 12 in FIGS. 6A, 6B, 7, 8 and 12
The trailing edge of the teeth of the second target track 14 passing through line 160, shown as the rising edge of, has moved to the position of line 160. Similarly, in the rotation of about 15 degrees shown as the dotted line 155 in FIG. 14,
A conflicting situation occurred in which the tooth rise of the second target track 14 moved to line 160 and the tooth fall of the first target track 12 moved past line 160. As can be seen, these zero-cross positions allow the present invention to accurately define the exact location of the rise and fall of all teeth and grooves on both target tracks. This allows a very accurate determination of the position of the rotating member, which can be made without the need for rotation of the member.

Further in FIG. 16 it can be seen that both curves 140, 144 are slightly offset in the positive voltage direction. In other words, the peak of the curve 140 in the positive direction has a larger absolute value than the peak of the curve 140 in the negative direction. As is well known to those skilled in the art, this situation can be easily compensated for by circuit element trim operation.

It has not been shown that the use of other techniques such as the Hall effect element configuration or the multiple magnet technique has the beneficial effect shown in FIG. The very accurate zero-cross position detected by the present invention is generally insensitive to changes in the gap G between the target track tooth and the first surface on which the magnetoresistor is located. This is very important in many different types of applications due to the presence of runout due to changes in the manufacture and assembly of the device. For example, using the present invention in automotive applications to determine the rotational position of a particular shaft of an automotive engine,
The exact distance between the magnetoresistive body and the rotating object consisting of the complementary target track is from one assembly in the first vehicle to the second.
In a second assembly of a car, and more importantly, the gap G may change from one rotational position to another due to imperfect manufacturing or assembly procedures. Because of the relative insensitivity of the present invention to this type of change in the gap G, shown by the consistent zero crossings of FIG. 14 for both curves 140, 144, the present invention provides a useful solution to the problem well known to those skilled in the art for many years. I will provide a.

In FIG. 16, the graphical representation at the top of the figure can be used to generate a digital or binary output signal from the sensor. In other words, if the curves 140 to 144 are positive, the output signal will be positive, if the curves are negative, no signal will be emitted. The lower part of FIG. 16 illustrates this concept. Between 12 and 15 degrees, the curves 140, 144 are positive. To show this characteristic, a square wave 157 can be emitted during the positive period of the curve at the top of the figure. The square wave 157 shown at the bottom of FIG. 16 corresponds to the algebraic sign of the signal at the top of FIG. There are many different ways to provide a binary output, but one suitable circuit is shown in FIG. Magnetic resistor R
A, RB, RC and RD are composed of a Wheatstone bridge having the same structure as that shown in FIG. Circuit point 9
The outputs from 1, 93 are connected to amplifier 175. The output from the comparator 175 is connected to the Schmitt trigger 177. The output from the Schmitt trigger at circuit point 179 shows a signal similar to that shown at 157 in FIG.

To illustrate the embodiments of the present invention, the invention has been described in considerable detail and illustrated with particular specificity, but it is noted that other embodiments are within the scope thereof. Figure 1
Although the particular nested pattern of magnetoresistors shown in 2 provides certain advantages, other configurations are possible when using the present invention. Although a Wheatstone bridge configuration is further illustrated in FIG. 8 and used to illustrate the operation of an embodiment of the present invention, other electrical circuits may be used with the present invention. Further, although the target tracks 12, 14 are shown in the drawings with grooves to create teeth and gaps, other configurations of the target tracks could incorporate a rotatable cylinder or a linear track with openings made of magnetic material. . Alternatively, a non-magnetic cylindrical body can be provided with a magnetic insert on its outer surface.

[Brief description of drawings]

FIG. 1 is a perspective view of one embodiment of the present invention.

FIG. 2 is a side view of first and second target tracks of the present invention.

FIG. 3 is a diagram in which a magnet, a substrate, and a plurality of magnetoresistors are added.
FIG.

FIG. 4 is a diagram showing the relationship between a magnetic resistor and first and second target tracks.

FIG. 5 is a schematic diagram showing the shape of the magnetic field in relation to the presence or absence of a magnet and a magnetic object in the vicinity of one part of the magnet.

FIG. 6 is a schematic diagram (A) showing the direction and strength of the magnetic field of the first surface when there is no magnetic object in the immediate vicinity of the magnetoresistive body;
FIG. 3B is a schematic view (B) showing the direction and strength of a magnetic field in which wide magnetic teeth are arranged near one side of the device.

FIG. 7 is a schematic diagram generally similar to FIG. 6A except that the narrow magnetic teeth are near one of the magnetoresistive bridges and the narrow grooves are near the opposite.

8 is a schematic diagram generally similar to FIG. 6A except that the magnetic tooth is near the lower right portion of the figure and another magnetic tooth is near the upper left portion of the figure.

FIG. 9 shows a magnet, spacer, ceramic substrate, first side of the invention arranged in physical relationship with two target tracks.

FIG. 10 illustrates another circuit that can be used in connection with the present invention.

FIG. 11 illustrates yet another circuit that can be used in connection with the present invention.

FIG. 12 is an example of a physical layout of four magnetoresistors on a ceramic substrate.

FIG. 13 is a diagram showing the geometric effect of magnetic field strength on a surface caused by a change in the direction of a magnetic field spreading through the surface.

FIG. 14 is a graph showing the resistance of a magnetoresistive body corresponding to the strength of a transverse magnetic field.

FIG. 15 is a graph showing the resistance of the magnetoresistive body corresponding to the angular relationship between the external magnetic field and the axis of the magnetoresistive body.

FIG. 16 is a graph showing empirical results when the present invention is applied to the detection of tooth and groove movement.

FIG. 17 shows an exemplary circuit that can be used to provide a binary signal as shown at the bottom of FIG.

[Explanation of Codes] 10 ... Rotating member, 12, 14 ... Target track, 16, 1
8 ... Tooth, 17, 19 ... Groove, 20 ... Permanent magnet, 22 ... Ceramic substrate, 44 ... Magnetoresistive body.

Claims (8)

[Claims] 1. A first magnetoresistive component arranged on a first side of a first axis in a first plane and a second magnetoresistive component on a second side of a first axis in the first plane. A second magnetoresistive component and first and second target tracks, each of the first and second target tracks comprising a plurality of first portions and a plurality of second portions, Each of the first portions of the first target track is one of the second portions of the second target track.
Adjacent to each other, each of said second portions of said first target track is said first portion of said second target track.
Of the first target track is located adjacent to one of the portions of the second surface, the first target track is located on the first side of the second surface, and the second target track is located on the second side of the second surface. And a movable object in which the first axis is at the intersection of the first surface and the second surface, and a function of the relative resistance of the first and second magnetoresistive elements,
Means for providing a first signal indicating the position of the movable member. 2. The sensor according to claim 1, further comprising a magnet disposed in proximity to the first surface so that the first surface is located between the magnet and the movable member. 3. A first, a second, a third, and a fourth magnetoresistors are arranged on the first surface, and the first and the third magnetoresistors are connected in series between the first and second circuit points. And electrically connecting the second and fourth magnetoresistors in series between the first and second circuit points, the first and third magnetoresistors being connected to the second and Electrically connected in parallel with a fourth magnetoresistor, said first and second magnetoresistors being connected at said first circuit point, said first and fourth magnetoresistors being said 1 is disposed on the first side of the first axis in the plane, and the second and third magnetoresistors are disposed on the second side of the first axis in the first plane, The moveable member has first and second target tracks, the first of which is
And the second target track each comprises a plurality of first portions and a plurality of second portions, each of the first portions of the first target track being the second portion of the second target track.
A second portion of the first target track, each of the second portions of the first target track is disposed adjacent to one of the first portions of the second target track, and
Target track is located on a first side of a second surface, the second target track is located on a second side of the second surface, and the first axis is located on the first and second sides. Is a function of a first voltage potential between the first and third magnetoresistors and a second voltage potential between the second and fourth magnetoresistors, the movable member A position sensor comprising means for providing a first signal indicative of the position of the. 4. The sensor according to claim 3, further comprising a magnet disposed near the first surface, the first surface of which is located between the magnet and the movable member. 5. A first, a second, a third, and a fourth magnetically sensitive element are arranged on a first side, the first and the fourth magnetically sensitive element being arranged on a first axis of the first side. On the first side, the second and third magnetically sensitive elements are arranged on the second side of the first axis of the first surface and have first and second target tracks, and Each of the first and second target tracks comprises a plurality of first portions and a plurality of second portions, each of the first portions of the first target tracks being the first of the second target tracks. 1 of 2
Adjacent to each other, each of said second portions of said first target track is said first portion of said second target track.
Of the first target track is located adjacent to one of the portions of the second surface, the first target track is located on the first side of the second surface, and the second target track is located on the second side of the second surface. The movable member is arranged such that the first axis is arranged in the first and second planes, and is associated with the first and third magnetically sensitive elements. A position sensor comprising means for providing a first signal indicative of the position of the movable member, which is a function of a second voltage potential associated with the second and fourth magnetically sensitive elements. 6. The sensor according to claim 5, further comprising a magnet arranged near the first surface, the first surface being located between the magnet and the movable member. 7. A first and a fourth magnetically sensitive element on a first side of a first axis and a second and a third magnetically sensitive element on said first side.
The first arranged on the first surface so as to come to the second side of the axis of
Two, three, four magnetically sensitive elements and first and second target tracks, each of the first and second target tracks comprising a plurality of first portions and a plurality of second portions. And each of the first portions of the first target track is one of the second portions of the second target track.
Adjacent to each other, each of said second portions of said first target track is said first portion of said second target track.
Of the first target track is located adjacent to one of the portions of the second surface, the first target track is located on the first side of the second surface, and the second target track is located on the second side of the second surface. And a means having a movable member with the first axis disposed in the first and second planes and means for providing a first signal indicative of the position of the movable member. 8. Further comprising a permanent magnet disposed in close proximity to said first, second, third, fourth magnetically sensitive element, said permanent magnet forming a magnetic field extending through said first surface. The sensor according to claim 7.