JP3186656B2 - Speed sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation speed sensor, and more particularly to a magnetic rotation speed sensor provided with a magnetic detecting element for detecting a change in a magnetic field accompanying rotation of a sensor rotor.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application No. 60-2544.
A magnetic rotational speed sensor disclosed in Japanese Patent No. 66 is known.
This rotation speed sensor includes a sensor rotor, a magnetic detector,
And a magnet. The magnetic detector is disposed so as to face the outer peripheral surface of the sensor rotor. The magnet is disposed so as to face the outer peripheral surface of the sensor rotor with the magnetic detector interposed therebetween. Further, the outer peripheral surface of the sensor rotor is provided with teeth formed at a constant pitch in the circumferential direction. Accordingly, when the sensor rotor rotates, a state in which the magnetic detector faces the tooth portion of the sensor rotor and a state in which the magnetic detector does not face the tooth portion are alternately formed, so that the magnetic field acting on the magnetic detector is formed. Changes according to the rotation of the sensor rotor.

In the above-mentioned conventional magnetic rotational speed sensor,
The magnetic detector has a bridge circuit composed of four magnetoresistive elements. The magnetoresistive elements are arranged at predetermined intervals in the rotation direction of the sensor rotor. Therefore, when the magnetic field acting on the magnetic detector changes according to the rotation of the sensor rotor, the resistance value of each magnetoresistive element forming the bridge circuit changes, and the output voltage of the bridge circuit changes according to the change in resistance. . Therefore, according to the conventional magnetic rotation speed sensor, the rotation speed of the sensor rotor can be detected based on the output voltage of the bridge circuit.

[0004] Incidentally, the magnetoresistive element has a property that its resistance value changes depending on temperature. On the other hand, in the conventional magnetic rotation speed sensor, since a bridge circuit is configured by the magnetoresistive elements, when the resistance value of each magnetoresistive element changes at a constant rate according to a temperature change, Its output voltage does not change. in this way,
The above-mentioned conventional magnetic rotational speed sensor can compensate for a resistance change of the magnetoresistive element depending on a temperature change by forming a bridge circuit with the magnetoresistive element.

[0005]

In the above-mentioned conventional magnetic rotational speed sensor, it is desirable that the output voltage of the bridge circuit be large in order to detect the rotational speed of the sensor rotor with high accuracy. The output voltage of the bridge circuit changes according to the phase relationship of the resistance change of each magnetoresistive element. Therefore, in order to increase the output of the sensor, it is necessary to appropriately set the arrangement of the magnetoresistive elements. However, in the above-mentioned conventional rotational speed sensor, no attempt is made to increase the output of the sensor.

[0006] The present invention has been made in view of the above points, and has as its object to provide a rotation speed sensor capable of obtaining a large output signal.

[0007]

The above object is achieved by the present invention.
As described in the above, a magnetic detector configured as a bridge circuit by a magnetic detection element showing a resistance change according to a change in the applied magnetic field, a magnet that generates a magnetic field, and a magnet that rotates in synchronization with the rotating body, A sensor rotor that changes a magnetic field acting on the magnetic detector at a predetermined cycle with respect to a rotation angle, wherein one pair of magnetic detection elements facing each other of the bridge circuit is connected to the sensor rotor. Place in the same position in the rotation direction and
The other pair of the magnetic sensing elements is referred to as the one pair, respectively.
Between the pair, the rotation direction of the sensor rotor or
Is a distance corresponding to a quarter of the predetermined period in the anti-rotation direction.
This is achieved by a rotational speed sensor spaced apart by a distance .

In the present invention, one set of the magnetic detecting elements facing each other in the bridge circuit is arranged at the same position in the rotation direction of the sensor rotor. Therefore, the magnetic fields acting on one pair of the magnetic sensing elements change in phase with each other. The resistance value of the magnetic sensing element changes according to the applied magnetic field. Therefore, the resistance value r of one pair of the magnetic sensing elements
1, r2 change in phase with each other. Generally, in a bridge circuit, when the resistance values of the opposing elements both increase, the potential of one of the output terminals decreases and the other potential increases. On the other hand, the other pair of magnetic sensing elements
With one pair interposed, the sensor rotor is turned from the other pair.
Equivalent to one-fourth of the predetermined period in the direction of rotation or counter-rotation
Separated by a certain distance. In this case, the bridge times
The road pattern becomes rich in symmetry. Therefore, according to the present invention, the resistance r
When 1, 1 and r2 change in phase, a large output voltage is output from the bridge circuit, and at the same time ,
By setting the resistance balance well, the offset
And a good output voltage with a small output voltage is secured .

Further, the object of the present invention is to provide a magnetic device which exhibits a resistance change corresponding to a change in an applied magnetic field.
Magnetic detector consisting of a bridge circuit with sensing elements
And a magnet that generates a magnetic field,
Rotate and act on the magnetic detector for its rotation angle
A sensor rotor that changes a magnetic field at a predetermined cycle.
In the rotation speed sensor, the magnet is detected by the magnet.
Made us Ri by the rotational speed sensor that is offset <br/> arranged in the rotational direction of the sensor rotor with respect to the device.

[0010]

[0011]

FIG. 1 is a configuration diagram of a rotation speed sensor 10 according to one embodiment of the present invention. As shown in FIG. 1, the rotation speed sensor 10 includes a sensor rotor 12. The sensor rotor 12 is a disk-shaped member made of a soft magnetic material. The teeth 13 are formed at a predetermined pitch P on the outer periphery of the sensor rotor 12.

The rotation speed sensor 10 also has a detection unit 14. The detection unit 14 includes a magnetic detector 16. The magnetic detector 16 is attached to an end face of the holding block 18. As will be described later, the magnetic detector 16 is formed by patterning a GMR thin film on an insulating substrate into a predetermined pattern. The detection unit 14 includes a magnetic detector 16
Are provided so as to face the outer peripheral surface of the sensor rotor 12 with a predetermined gap therebetween. The sensor rotor 12
Is provided to be larger than the width of the magnetic detector 16 in the direction perpendicular to the plane of FIG. Therefore,
The magnetic detector 16 has a sensor rotor 1 on its entire surface.
2 is opposed to the outer peripheral surface.

The detecting section 14 further includes a bias magnet 20. The bias magnet 20 is mounted inside the holding block 18 so as to face the outer peripheral surface of the sensor rotor 12 with the magnetic detector 16 therebetween. As described later, the bias magnet 20
It is arranged so as to be offset from the center position of the magnetic detector 16 by a predetermined amount in the rotation direction of the sensor rotor 12. The bias magnet 20 is polarized so that the side near the sensor rotor 12 has an N pole and the side far from the sensor rotor 12 has an S pole, or in the opposite direction.

A signal processing circuit 22 is mounted on the upper surface of the holding block 18 in FIG. The signal processing circuit 22
The signal output from the magnetic detector 16 is subjected to predetermined signal processing, and the result is output from the connector 23 as a sensor output signal. Next, the configuration of the magnetic detector 16 will be described with reference to FIG. FIG. 2 is a configuration diagram of the magnetic detector 16. Note that the magnetic detector 16 is installed such that the left-right direction in FIG. 2 coincides with the tangential direction of the sensor rotor 12. As shown in FIG. 2, the magnetic detector 16 includes an insulating substrate 24 formed in a rectangular shape. Insulating substrate 24
A GMR element bridge 26 is formed on the surface of. The GMR element bridge 26 is formed by patterning a GMR thin film formed on the surface of the insulating substrate 24 by photolithography.

The GMR thin film is a thin film formed by alternately stacking ferromagnetic layers and non-magnetic layers. As a combination of materials constituting the ferromagnetic layer and the nonmagnetic layer, for example, cobalt (Co) / copper (Cu), chromium (Cr) / iron (F
Combinations such as e) can be used. The GMR thin film having such a configuration has a characteristic that its resistance value greatly changes in accordance with the magnitude of a magnetic field acting in parallel to its surface (hereinafter, referred to as a horizontal component of the magnetic field). Fig. 3 is GM
2 illustrates a relationship between a magnetic field H acting on the R thin film and a resistance value R per unit area of the GMR thin film. As shown in FIG. 3, the resistance R per unit area of the GMR thin film is represented by a magnetic field H
Decreases as the absolute value of increases. The resistance of the GMR thin film does not depend on the direction of the magnetic field in a plane parallel to the surface.

Since the GMR element bridge 26 is made of a GMR thin film having such characteristics, the magnetic detector 16 can be used based on the resistance change of the GMR element bridge 26.
Can be detected. Referring to FIG. 2 again, the GMR element bridge 26 includes four GMR elements of a first GMR element 26a to a second GMR element 26d formed in a thin band-like pattern and four electrodes 28a to 28G.
8d. The electrode 28a is formed on the insulating substrate 24 in FIG.
Is provided at the lower left end. Also, the electrode 28b
To 28d are arranged in the vertical direction in the figure at positions spaced a predetermined distance to the right of the electrode 28a in FIG.

The first GMR element 26a extends upward from the electrode 28a, turns downward at the upper end of the insulating substrate 24, bends rightward near the lower end, and reaches the electrode 28d. The fourth GMR element 26d extends rightward from the electrode 28d, bends upward, turns downward near the upper end of the insulating substrate 24, and then bends leftward to form the electrode 28c.
Has been reached.

After extending leftward from the electrode 28c, the third GMR element 26c bends downward at a position adjacent to the first GMR element 26a, and turns upward near the lower end of the insulating substrate 24. Is bent rightward in the vicinity of the upper end of the first electrode and reaches the electrode 28b. Second GMR element 26
b extends rightward from the electrode 28b, then bends downward at a position adjacent to and beyond the fourth GMR element 26d, reaches the lower end of the insulating substrate 24, and bends leftward to reach the electrode 28a.
Has been reached.

As described above, the first GMR element 26a and the third
The GMR element 26c, the second GMR element 26b and the fourth
The GMR elements 26d are arranged adjacent to each other. Also, the second GMR element 26b and the fourth GMR
The element 26d is connected to the sensor rotor 12 from the first GMR element 26a and the third GMR element 26c to the right in FIG.
Are arranged at positions spaced apart by a distance corresponding to half of the pitch P of the tooth portions 13.

The first GMR element 26a to the fourth GMR element 2
6d and the electrodes 28a to 28d are formed as described above, so that the first GMR element 26a, the fourth GMR element 26d, the third GMR element 26c, and the second GMR element 26b are arranged in this order in the electrode 28d, respectively. , 28b,
They are connected to each other via 28b and 28a to form a bridge circuit. Hereinafter, the resistance of the first GMR element 26a is R1, and the resistance of the second GMR element 26b is R2.
The resistance of the third GMR element 26c is R3, and the resistance of the fourth GMR element 26c is R4.
The resistance value of the R element 26d is represented by R4. The first GMR element 26a to the fourth GMR element 26
d is a state in which no magnetic field acts, and the resistance values R1 to R4 are configured to be equal to each other.

FIG. 4 is a circuit diagram of a bridge circuit formed by the GMR element bridge 26. As shown in FIG. 4, a constant voltage E is applied between the pair of electrode pads 28 b and 28 d facing each other, and the potential difference V between the other pair of electrode pads 28 a and 28 c is used as the output voltage of the magnetic detector 16. , To the signal processing circuit 22. The output voltage V can be represented by the following equation using the resistance values R1 to R4 and the constant voltage E.

V = E · {R2 / (R1 + R2) −R3 / (R3 + R4)} (1) As can be seen from the equation (1), the resistance values R1 and R3 (or R2 and R4) of the elements facing each other are the same. When the phase is changed, when one term on the right side increases, the other term decreases, so that the amplitude of the output voltage V can be increased. By the way, as described above, the magnetic detector 16 is arranged so that the left-right direction in FIG. 2 coincides with the tangential direction of the sensor rotor 12, that is, the rotation direction. Therefore, the first GMR element 26a to the fourth GMR element 26d are arranged such that main parts thereof are perpendicular to the rotation direction of the sensor rotor 12. For this reason, when the sensor rotor 12 rotates, the tooth portions 13 are moved from the first GMR element 26a to the fourth GMR element 26a.
It moves across the front surface of the GMR element 26d, and accordingly, the first GMR element 26a to the fourth GMR element 26d
The magnetic field that acts on changes.

The change of the magnetic field acting on the GMR element 26 according to the rotation angle of the sensor rotor 12 will be described below with reference to FIGS. In the following description, the rotation angle of the sensor rotor 12 is represented by a phase angle of 360 ° when the sensor rotor 12 is rotated by an angle corresponding to the pitch P of the teeth 13, and is represented by a phase angle. The rotation angle of the sensor rotor 12 is referred to as the rotation phase angle θ of the sensor rotor 12.

As shown in FIGS. 5 to 8, the magnetic flux generated by the bias magnet 20 is guided to the teeth 13 of the sensor rotor 12. As shown in these figures, the bias magnet 20 is located at the center of the GMR sensor bridge 26,
First GMR sensor element 26a and third GMR element 26c
From the sensor rotor 12 in the rotation direction of the sensor rotor 12. Therefore, in the state shown in FIG. 5, the magnetic flux 21 guided from the bias magnet 20 to the teeth 13
The magnetic flux b passes through the second GMR element 26b and the fourth GMR element 26d, and the magnetic flux 21a guided from the bias magnet 20 to the tooth portion 13a is separated by the first GMR element 26a and the third GM
It has passed through the R element 26c. In addition, at the rotation position of the sensor rotor 12 shown in FIG.
The horizontal component of the magnetic field acting on the fourth GMR element 26d is equal to the horizontal component of the magnetic field acting on the first GMR element 26a and the third GMR element 26c. Hereinafter, this rotational position is referred to as a reference position. Therefore, at the reference position shown in FIG. 5, the first GMR element 26a to the fourth GMR element 2
The resistance values R1 to R4 of 6d are equal to each other.

From the reference position shown in FIG.
2 rotates rightward in the drawing by a phase angle of 90 °, as shown in FIG. 6, the center of the magnetic flux 21b becomes the second GMR element 26b.
And the magnetic flux 21a passes through the fourth GMR element 26d.
A state where the light does not pass through the GMR element 26a and the third GMR element 26c is formed. In this state, the second GMR element 2
6b and the horizontal component of the magnetic field acting on the fourth GMR element 26d are maximized, so that their resistances R2 and R4 are minimized, while the first GMR element 26a and the third GMR element 26d are not.
Since the horizontal component of the magnetic field acting on the MR element 26c becomes minimum (substantially zero), these resistance values R1 and R3 become maximum.

When the sensor rotor 12 further rotates rightward in the figure by a phase angle of 90 ° from the state shown in FIG. 6, that is, when the sensor rotor 12 rotates by a phase angle of 135 ° from the reference position, as shown in FIG. The peripheral portion is the second GMR element 2
6b and the fourth GMR element 26d, and the first GMR element 26
a and the third GMR element 26c. In this state, the second GMR element 26b and the fourth GMR element 26b
The horizontal component of the magnetic field acting on the MR element 26d and the first GM
The horizontal components of the magnetic field acting on the R element 26a and the third GMR element 26c are equal to each other, and therefore, the resistance values R1 to R
4 are equal to each other.

When the sensor rotor 12 further rotates rightward in the figure by a phase angle of 90 ° from the state shown in FIG. 7, that is, when the sensor rotor 12 rotates by a phase angle of 180 ° from the state shown in FIG. 6, the state shown in FIG. Become. As described above, the second GMR element 26b and the fourth GMR element 26d, and the first GMR element 26a and the third GMR element 26c
The second tooth portions 13 are arranged at positions separated by half the pitch P. For this reason, in the state shown in FIG. 8, the first GMR element 26a and the third GMR
The horizontal component of the magnetic field acting on the element 26c is maximized, while the horizontal component of the magnetic field acting on the second GMR element 26b and the third GMR element 26d is minimized. Therefore, the resistance values R2 and R4 become maximum, and the resistance values R1 and R3 become minimum.

When the sensor rotor 12 further rotates from the state shown in FIG. 8 to the right by a phase angle of 45 ° in the figure, a state similar to that shown in FIG.
4 are equal to each other. Thus, the first GMR element 2
The resistance values R1 to R4 of the 6a to fourth GMR elements 26d are periodically increased and decreased with the sensor rotor 12. FIG. 9 shows the relationship between (a) the resistance values R1 to R4 and (b) the output voltage V obtained from the above equation (1) with respect to the rotation angle phase angle θ of the sensor rotor 12. In FIG. 9, the rate of change of the resistance values R1 to R4 is 1 at the maximum.
It is assumed that the constant voltage E is 0%, and the output voltage V indicates a value when the constant voltage E supplied to the GMR element bridge 26 is 2V.

As shown in FIG. 9, the resistance values R1, R3 and the resistance values R2, R4 are shifted from each other by 180 °, and are shifted by 360 ° with respect to the rotational phase angle θ of the sensor rotor 12.
It changes in the period of. In response to such a change in R1 to R4, the output voltage V changes at a cycle of 360 ° with respect to the rotation phase angle θ of the sensor rotor 12, as shown in FIG. 9B, and its amplitude becomes about 200 mV _pp. I have. Therefore, the output voltage V is converted into a pulse signal by, for example, binarization by the signal processing circuit 22 and the number of pulses is counted, whereby the rotation speed of the sensor rotor 12 can be detected.

As described above, in the present embodiment, the first GMR element 26a and the third GMR element
The resistance values R1 and R3 of the second GMR element 26b and the resistance values R2 and R4 of the fourth GMR element 26d change in phase with each other, so that a large amplitude is obtained as described with reference to the above equation (1). Can be obtained. Further, when the resistance value R2 and the resistance value R3 change in opposite phases to each other, the difference between the terms on the left side of Expression (1) increases, and the output voltage V is further increased.

As described above, in the present embodiment, the pair of the first GMR element 26a and the third GMR element 26c facing each other in the bridge circuit and the second GMR element 26b
And the set of the fourth GMR elements 26d are separated from each other by a distance corresponding to a half of the pitch P of the teeth 13 of the sensor rotor 12, so that the output of the magnetic detector 16 is increased. Therefore, according to the rotation speed sensor 10 of the present embodiment, the signal processing circuit 22 that processes the output signal of the magnetic detector 16 can be simplified, and the cost of the system can be reduced.

As described above, the first GMR element 26a
The fourth GMR element 26d is configured such that the resistance values R1 to R4 are equal to each other in a state where no magnetic field is applied, and the offset of the output voltage V in a state where the magnetic field is not applied to the magnetic detector 16 is as follows. It is kept small.
By the way, generally, the resistance value of a GMR thin film changes at a rate corresponding to a temperature change. That is, G at a certain reference temperature
Assuming that the resistance value of the MR thin film is R, from this reference temperature, Δt
The resistance value Rt in the case where the resistance value rises by Rt is represented by Rt = (1 + α · Δt) · R (2) Here, α is a temperature change coefficient of the resistance value of the GMR thin film.

Therefore, when the temperature of the GMR element 26 rises by Δt, the resistance values R1 to R4 become (1 + α
.DELTA.t) times. However, as can be seen from equation (1), the output voltage V
Is expressed as a ratio of resistance values R1 to R4. For this reason,
When the same temperature change occurs in the first GMR element 26a to the second GMR element 26d, the output voltage V does not change because the resistance values R1 to R4 change at an equal rate. Thus, in the present embodiment, the first GMR elements 26a to 26a
Since the fourth GMR element 26d forms a bridge circuit, temperature-dependent changes in the resistance values R1 to R4 are compensated.

In the present embodiment, the bridge circuit is realized only by arranging the electrode pads 28a to 28d at the connection portions of the first GMR element 26a to the fourth GMR element 26d, and a wiring part is separately provided. It is not necessary. For this reason, it is not necessary to configure the magnetic detector 16 by multilayer wiring, and it is possible to reduce the manufacturing cost of the magnetic detector 16. In addition, since a multilayer wiring is not required, a protective film is formed on the surface of the magnetic detector 16,
By providing a contact hole at a portion corresponding to the electrodes 28a to 28d, electrical connection to the GMR bridge 26 can be easily performed by, for example, face-down mounting.

Next, a second embodiment of the present invention will be described. The rotational speed sensor of the present embodiment is realized by using a magnetic detector 50 instead of the magnetic detector 16 in the rotational speed sensor 10 of the first embodiment. FIG. 10 is a configuration diagram of the magnetic detector 50 included in the rotation speed sensor of the present embodiment. The magnetic detector 50 of the present embodiment includes an insulating substrate 52 and an insulating substrate 52 similar to the magnetic detector 16 of the first embodiment.
And a GMR element bridge 54 formed on the surface of the GMR element. The GMR element bridge 54 includes first to fourth GMR elements 54a to 54d and electrodes 56a to 56d. In this embodiment, the magnetic detector 50 is also used.
Are installed such that the left-right direction in FIG. 10 coincides with the rotation direction of the sensor rotor 12.

The electrodes 56a to 56d are provided at the upper right corner, the upper left corner, the lower left corner, and the lower right corner of the insulating substrate 52, respectively. The first GMR element 54a extends in the up-down direction in FIG. 10 and connects the electrode 56a to the electrode 56d. Further, the third GMR element 54c is shifted from the first GMR element 54a by half the pitch P (phase angle 180
(°) extends vertically in FIG. 10 to connect the electrode 56b and the electrode 56c.

The second GMR element 54b extends to the left in the figure from the electrode 56a, and extends from the first GMR element 56a at a pitch P of four.
At a position separated by a distance corresponding to one-half (a phase angle of 90 °), it bends and extends downward, turns near the lower end of the insulating substrate 52, extends upward, and then bends to the left to form an electrode 56
b has been reached. The fourth GMR element 54d includes an electrode 56d
From the first GMR element 56a, and bends at a position separated from the first GMR element 56a by a distance corresponding to a quarter of the pitch P (phase angle 90 °), and extends upward adjacent to the second GMR element 54b. After being folded near the upper end of the insulating substrate 52 and extending downward, it is bent leftward to reach the electrode 56c. Also in the present embodiment, if the resistance values of the first GMR element 54a to the fourth GMR element 54d are R1 to R4, respectively, a bridge circuit similar to that of FIG. 4 is formed, and a constant voltage E is applied between the electrodes 56d and 56b. Then, the potential difference between the electrodes 56a and 56c is output as the output voltage V of the magnetic detection element 50.

As described above, in this embodiment, the second G
The MR element 54b and the fourth GMR element 54c are arranged at the same position in the rotation direction of the sensor rotor 12. For this reason, with the rotation of the sensor rotor 12, the second GMR
The horizontal components of the magnetic field acting on the element 54b and the fourth GMR element 54d change in phase. On the other hand, the first GMR element 5
4a and the third GMR element 54c
b and the fourth GMR element 54d, respectively, as shown in FIG.
0 on both the left and right sides with a phase distance of 90 °. Therefore, for example, when the sensor rotor 12
When rotating from left to right in FIG. 10, the first GM
The horizontal component of the magnetic field acting on the R element 54a is the second GMR
The horizontal component of the magnetic field acting on the element 54b and the fourth GMR element 54d changes with a phase delay of 90 ° with respect to the horizontal component of the magnetic field acting on the third GMR element 54b.
The phase changes by 90 degrees with respect to the horizontal component of the magnetic field acting on the GMR element 54b and the fourth GMR element 54d.

FIG. 11 shows (a) resistance values R1 to R with respect to the rotation phase angle of the sensor rotor 12 in this embodiment.
4 and (b) the relationship between the output voltages V under the same conditions as in FIG. As the magnetic field acting on the first GMR element 54a to the fourth GMR element 54d changes in the above-described phase relationship, the resistance values R2 and R4 change in the same phase as shown in FIG. R1 is in a state in which the phase is delayed by 90 ° with respect to the resistance values R2 and R4, and the resistance value R3 is in a state in which the phase is 90 ° behind the resistance values R2 and R4.
° Each change in advanced state. Then, according to the change in the resistance value, the output voltage V becomes 36 degrees with respect to the phase rotation angle θ of the sensor rotor 12 as shown in FIG.
It changes with an amplitude of about 120 mV _{pp in} a 0 ° cycle.

As described above, generally, in order to increase the output voltage of the bridge circuit, it is desirable to change the resistance values of the elements facing each other in the same phase. According to the present embodiment, the second GMR element 54b and the fourth GM
By changing the resistance values R2 and R4 of the R element 54d in the same phase, the output voltage V is improved. In the present embodiment, the pattern of the GMR element bridge 54 is richer in symmetry than the pattern of the GMR element bridge 26 of the first embodiment. Therefore, it is easy to set a good balance of the resistance values of the first GMR elements 54a to 54d constituting the GMR element bridge 54, and a good output voltage V with a small offset is obtained.
Can be obtained.

Also, in the rotation speed sensor of this embodiment, like the rotation speed sensor 10 of the first embodiment, the first rotation speed
The electrode 5 is provided between the GMR element 54a and the fourth GMR element 54d.
By providing 6a to 56d, the bridge circuit is realized. That is, also in the present embodiment, it is unnecessary to perform multilayer wiring, and by forming a protective film and a contact hole, electrical connection to the magnetic detector 50 can be easily performed.

In the first and second embodiments, the bias magnet 20 is disposed at the back of the magnetic detectors 16 and 50, and the sensor rotor 12 is made of a soft magnetic material. The magnetic field acting on the magnetic detectors 16 and 50 is changed according to the above. However, the present invention is not limited to such a configuration, and magnets may be provided on the outer peripheral portion of the sensor rotor 12 at a constant pitch.

In the first to fourth embodiments,
First GMR element 26a, 54a to fourth GMR element 26
d and 54d correspond to the magnetic detecting element described in the claims.

[0044]

As described above, according to the first and second aspects of the present invention, the output signal of the magnetic detector can be increased.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a rotation speed sensor according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a magnetic detector included in the rotation speed sensor of the present embodiment.

FIG. 3 is a diagram showing a relationship between a magnetic field acting parallel to the GMR thin film and a resistance value.

FIG. 4 is a circuit diagram of a GMR element bridge included in the magnetic detector of the present embodiment.

FIG. 5 is a diagram (part 1) illustrating how a magnetic field acting on a GMR element bridge changes in accordance with rotation of a sensor rotor.

FIG. 6 is a diagram (part 2) illustrating how a magnetic field acting on a GMR element bridge changes according to rotation of a sensor rotor.

FIG. 7 is a diagram (part 3) illustrating how a magnetic field acting on a GMR element bridge changes according to rotation of a sensor rotor.

FIG. 8 is a diagram (part 4) illustrating how a magnetic field acting on a GMR element bridge changes according to rotation of a sensor rotor.

FIG. 9 shows a resistance value of each GMR element with respect to a rotation phase angle of a sensor rotor in the rotation speed sensor of the present embodiment, and
It is a figure showing relation of output voltage of a magnetic detector.

FIG. 10 is a configuration diagram of a magnetic detector included in a rotation speed sensor according to a second embodiment of the present invention.

FIG. 11 is a diagram showing the relationship between the resistance value of each GMR element and the output voltage of the magnetic detector with respect to the rotation phase angle of the sensor rotor in the rotation speed sensor of the present embodiment.

[Explanation of symbols]

 12 Sensor rotor 16, 50 Magnetic detector 20 Bias magnet 26, 54 GMR element bridge 26a, 54a First GMR element 26a, 54b Second GMR element 26c, 54c Third GMR element 26d, 54d Fourth GMR element

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01D 5/00-5/62 G01B ⁷ /00-7/32 G01P 1/00-3/80

Claims (2)

(57) [Claims] A magnetic detector configured to form a bridge circuit with a magnetic detection element exhibiting a resistance change corresponding to a change in an applied magnetic field; a magnet for generating a magnetic field; A sensor rotor that changes a magnetic field acting on the magnetic detector at a predetermined cycle with respect to a rotation angle, wherein one pair of magnetic detection elements facing each other of the bridge circuit is connected to the sensor rotor. The magnetic sensors are arranged at the same position with respect to the rotation direction, and the other pair of the magnetic sensing elements are respectively connected to the one pair.
, The rotational direction of the sensor rotor from the one pair
Or, in the anti-rotation direction, corresponds to a quarter of the predetermined period
A rotation speed sensor, wherein the rotation speed sensor is arranged at a distance . 2. A resistance change according to a change in an applied magnetic field.
The magnetism that constitutes the bridge circuit with the magnetic sensing element shown
Air detector, a magnet that generates a magnetic field, and a rotating body.
Rotate synchronously, and the magnetic detector
A sensor rotor that changes the acting magnetic field at a predetermined cycle.
A rotation speed sensor comprising:
A rotation speed sensor, wherein the rotation speed sensor is arranged offset in the rotation direction of the rotor .