JP2002372574A - Magnetic field detector - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a magnetic field detection device which is not affected by a temperature change. SOLUTION: A synchronous rectifier circuit 1 for extracting a resistance component signal b from a detection signal of impedance by an MI element 11a.
9a, a synchronous rectifier circuit 19b for extracting a reactance component signal d from an impedance detection signal by the MI element 11a, a resistance component signal b extracted by the synchronous rectifier circuit 19a, and a reactance component signal extracted by the synchronous rectifier circuit 19b A variable amplifier 1 for correcting at least one of the component signals d so that the sum of the change amounts of the resistance component signal b and the reactance component signal d with respect to the temperature change approaches 0
9a and an adder 23 for adding and outputting the corrected resistance component signal b and reactance component signal f.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field detecting device for detecting an electromagnetic quantity or a dynamic quantity using an external magnetic field.

[0002]

2. Description of the Related Art Conventionally, in various fields, detection of an electromagnetic quantity or a dynamic quantity using an external magnetic field has been performed. In order to detect such an electromagnetic quantity or a dynamic quantity with high sensitivity, An element having a high rate of change in physical quantity (resistance, impedance) with respect to an external magnetic field is used, and the external magnetic field is converted into an electric signal and detected. As an element for performing such detection, for example, there is a magnetic field detection device using an MI element disclosed in Japanese Patent Application Laid-Open No. 8-320362.

[0003] This magnetic field detecting device is formed by forming a laminate composed of a conductor layer and a magnetic layer surrounding the periphery of the conductor layer on the upper surface of a planar substrate. Then, an alternating current is applied from a driving power supply to the magnetic field detecting device to detect a change in impedance due to an external magnetic field, and the magnetic layer has magnetic anisotropy in a direction perpendicular to the direction of current application. Has been granted.

[0004] As described above, the magnetic field detecting device is constituted by the MI element in which the magnetic layer and the conductive layer are laminated, and the magnetic layer is provided with magnetic anisotropy, so that the magnetic field detecting device can be made low. It can be made a resistor, so that a change in inductance and a change in resistance due to a change in an external magnetic field can be effectively detected. According to this, the sensitivity can be greatly increased in the driving frequency range of 100 KHz to 10 MHz, and the impedance change rate is 100% or more.

[0005]

However, in the conventional magnetic field detecting device, as shown in FIG. 5, there is a problem that the accuracy as a sensor is lowered because the impedance value fluctuates in response to a change in ambient temperature. . FIG.
When the ambient temperature is 100 ° C and when the ambient temperature is -40 ° C,
It shows a change in impedance (Ω) with respect to a change in the magnetic field (Oe). For all the magnitudes of the magnetic field, when the temperature is 100 ° C., the impedance value becomes larger than when −40 ° C. I have.

This is based on the following reasons. That is, the impedance Z that changes with respect to the applied magnetic field includes a resistance component R and a reactance component X as shown in the following equation.

[0007]

(Equation 1)

In the above equation, the main factor of the resistance component R is the resistivity of the conductor layer and the magnetic layer, which are the components of the MI element, and the main factor of the reactance component X is the permeability of the magnetic layer. The magnetic susceptibility. Since the resistivity has a characteristic that increases as the ambient temperature increases, the resistance component R
Increases with increasing temperature. On the other hand, since the magnetic permeability decreases with increasing ambient temperature, the reactance component X decreases with increasing temperature.

The increase in the resistance component R due to the temperature rise is as follows.
Since the reactance component X is larger than the decrease, the total impedance Z increases with the temperature rise. This tendency becomes remarkable when the element driving frequency at which a simple circuit configuration is possible is 50 MHz or less.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to address the above-mentioned problem, and an object of the present invention is to provide a magnetic field detecting device which is not affected by a change in temperature.

In order to achieve the above object, a feature of the magnetic field detecting device according to the present invention is that the magnetic field detecting device includes a magnetic detecting element and detects a change in electrical characteristics according to an external magnetic field. First extraction means for extracting a resistance component signal from the detection signal of impedance by the element, second extraction means for extracting a reactance component signal from the detection signal of impedance by the magnetic detection element, and a resistance component extracted by the first extraction means Correction means for correcting at least one of the signal and the reactance component signal extracted by the second extraction means so that the sum of the amounts of change in the temperature change of the resistance component signal and the reactance component signal approaches zero. And output means for adding and outputting the corrected resistance component signal and the reactance component signal.

In this case, the correction means includes a first correction means for correcting the resistance component signal extracted by the first extraction means,
It is preferable to include a second correction unit that corrects the reactance component signal extracted by the second extraction unit.

According to the feature of the present invention configured as described above, the amount of change in the resistance component signal due to temperature change is made closer to the amount of change in the reactance component signal due to temperature change, or The amount of change due to the temperature change of the signal can be approximated to the amount of change due to the temperature change of the resistance component signal. As a result, the impedance as a whole is directed in a direction in which the amount of change due to the temperature change is offset, and the influence of the temperature change is reduced.

This is because the resistance component signal rises and the reactance component signal falls as the temperature rises. Further, the correction means is composed of first and second two correction means, which correct the resistance component signal and the reactance component signal, respectively, so that the sum of the change amounts with respect to the temperature change approaches 0. More effective correction can be made.

Another feature of the present invention resides in that the correction amplification factor of the resistance component signal is set to be smaller than the correction amplification factor of the reactance component signal. When the resistance component signal and the reactance component signal are not corrected, the width of the change is larger in the resistance component signal than in the reactance component signal. Therefore, by making the correction amplification factor of the resistance component signal smaller than the correction amplification factor of the reactance component signal, efficient correction can be performed. In this case, only the reactance component signal may be corrected without correcting the resistance component signal.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a magnetic field detection device 10 according to the embodiment. In this magnetic field detecting device 10, two MI elements (magnetic detecting elements) 11a and 11b and two resistors 12a and 12b having the same resistance value are arranged in a bridge shape, and between the resistors 12a and 12b. The oscillation circuit 13 is connected.

The MI elements 11a and 11b are arranged with their longitudinal directions orthogonal to each other, and both have the structure shown in FIG. In the MI element 11a (11b), a rectangular thin film-shaped magnetic layer 15 is formed on the upper surface of an Si wafer 14 which is a rectangular planar semiconductor substrate, and a central portion along the longitudinal direction of the upper surface of the magnetic layer 15 is formed. The conductor layer 16 in the form of a rectangular thin film is elongated in the magnetic layer 15.
Are formed in a state aligned in the longitudinal direction. On the upper surfaces of the conductor layer 16 and the magnetic body 15, a rectangular thin film-shaped magnetic layer 17 is formed so as to sandwich the conductor layer 16 with the magnetic layer 15.

The length of the magnetic layers 15 and 17 is set to be at least 5 times the width and the width is set to be 100 to 1000 times the thickness. The magnetic layers 15, the conductor layers 16 and the magnetic layers Each of the layers 17 is formed by sputtering the Si wafer 1
4 is formed on the upper surface. This sputter deposition
This is performed as follows. That is, first, when forming the target metal plate (magnetic layers 15 and 17 in the vacuum chamber, CoNbZr, FeCoSiB, CoS
In the case of forming an amorphous soft magnetic material having a magnetostriction constant of approximately 0, such as iB, or a conductor layer 16, a conductor such as Cu, Al, or Ag) is disposed, and the Si wafer 1 is disposed at an opposing position.
4 is arranged.

Next, the chamber is evacuated to a high vacuum,
A high voltage is applied between the target and the Si wafer 14, and a gas such as argon is introduced into the vacuum chamber. Then, this gas is turned into plasma, and ions in the plasma collide with a target which is a negative voltage electrode to scatter (sputter) atoms of the target, so that sputtered particles are deposited on the surface of the Si wafer 14 provided on the anode side. Then, a magnetic layer 15, a conductor layer 16, and a magnetic layer 17 are sequentially formed.

In forming the thin film, a mask is used to prevent the thin film from being formed in a portion other than the thin film forming position, so that the thin film is formed only in the thin film forming position. After the formation of each of the layers 15, 16, and 17, the laminate is annealed (heat-treated) while a DC magnetic field is applied along the longitudinal direction of the laminate. As a result, the magnetic elements 15a, 17 are provided with magnetic anisotropy along the longitudinal direction, and the direction a becomes the easy magnetization direction.
b is obtained. Both ends of the conductor layer 16 are formed as wiring electrodes, respectively, and are connected to the wirings.

The oscillating circuit 13 serves as a driving means for supplying a high-frequency AC current to the MI elements 11a and 11b.
The signals are output to the elements 11a and 11b, respectively. As the oscillating circuit 13, one having a high frequency stability and a stable amplitude is used. The electrodes of the MI elements 11a and 11b, that is, the electrodes between the resistor 12a and the MI element 11a and the electrodes between the resistor 12b and the MI element 11b are connected to two input terminals of the differential amplifier circuit 18, respectively. .

The differential amplifier circuit 18 includes the MI element 11
A circuit for detecting the difference between the signals generated at the electrodes a and 11b and amplifying the difference between the two input signals.
b and the voltage V ₂ between the MI element 11b and the resistors 12a and M
Difference V ₂ −V between potential between voltage V ₁ and I element 11 a
₁ is amplified regardless of the magnitudes of V ₂ and V ₁ .

[0023] That is, MI elements 11a, in a state in which the magnetic field is not applied to the 11b, for equal to the voltage _{V 1} and the voltage _{V 2,} although the potential difference _V 2 -V ₁ is 0, the balance by applying a magnetic field Collapse and a potential difference occurs. At this time, the signal of the voltage V ₁ is input to one input terminal of the differential amplifier circuit 18, and the signal of the voltage V ₂ is input to the other input terminal of the differential amplifier circuit 18. 18 a signal of the output voltage _{V 3} corresponding to the difference between the two synchronous rectification circuit 19a, and outputs to 19b.

The synchronous rectifier circuit 19a is a circuit that converts an AC voltage into a DC voltage and extracts a resistance component from the impedance. In this synchronous rectifier circuit 19a,
Only a signal having the same phase as the phase reference signal output from the phase correction circuit 20 is extracted from the output signal from the differential amplifier circuit 18. This synchronous rectifier circuit 19a is connected to a phase correction circuit 20 connected to the oscillation circuit 13,
The signal output from the oscillation circuit 13 is input to the synchronous rectification circuit 19a via the phase correction circuit 20 as a phase reference signal.

The synchronous rectifier circuit 19b is also a synchronous rectifier circuit 19a.
As in the above, the AC voltage is converted to the DC voltage, and the reactance component in the impedance is extracted. The synchronous rectifier circuit 19b also includes the phase correction circuit 2 connected to the oscillation circuit 13.
0, and the signal output from the oscillation circuit 13 is input to the synchronous rectification circuit 19b as a phase reference signal via the phase correction circuit 20. The signal input to the synchronous rectifier circuit 19b via the phase correction circuit 20 and the synchronous rectifier circuit 19b
The signal to be inputted by a is determined by the phase correction circuit 20 as 9
A phase difference of 0 degrees is provided.

The phase correction circuit 20 is a circuit for performing processing for maintaining the phase relationship sufficiently correctly in the synchronous rectification mechanism. In this case, as described above, the phase correction circuit 20 is a base of the phase reference signal output from the transmission circuit 13. The signal is sent to the synchronous rectifier circuits 19a and 19b with the phase changed by 90 degrees. Therefore, the synchronous rectifier circuit 19a extracts a resistance component in the impedance, and the synchronous rectifier circuit 19b extracts a reactance component in the impedance.

That is, the oscillation circuit 13 generates a signal serving as a base of the phase reference signal, and outputs the signal to the phase correction circuit 20.
Send to The phase correction circuit 20 converts the signal having a phase difference of 0 from the signal serving as the base of the phase reference signal into the synchronous rectification circuit 19b
On the other hand, a signal that is 90 degrees out of phase with the signal serving as the base of the phase reference signal is generated, and this signal is sent to the synchronous rectifier circuit 19a. Then, the synchronous rectifier circuit 19a,
The output signal of the differential amplifier circuit 18 is input to 19b, and the impedance Z obtained from this signal can be expressed by the following equation.

[0028]

(Equation 2)

Asin θ is a resistance component, and A cos θ is a reactance component. Therefore, when the phase is shifted by 90 degrees and θ is 90 degrees, Z = Asin θ, and θ becomes 0
In the case of degrees, Z = Acos θ, and only the resistance component A is extracted as impedance in the synchronous rectifier circuit 19a, and only the reactance component A is extracted as impedance in the synchronous rectifier circuit 19b.

The synchronous rectifier circuit 19a is connected to a low-pass filter circuit 21a, and the low-pass filter circuit 21a is connected to a variable amplifier 22a.

The low-pass filter circuit 21a is a filter that removes unnecessary components such as noise and has a single transmission band from 0 to a certain finite cutoff frequency. Converts the AC signal to a DC signal by blocking the power supply frequency and its harmonics. That is, the alternating current converted by the synchronous rectifier circuit 19a has an uneven waveform having a positive voltage of a sine wave waveform, and the low-pass filter circuit 21a converts the uneven waveform into a smooth waveform. To convert to DC. The synchronous rectifier circuit 19a, the phase correction circuit 20, and the low-pass filter circuit 21a constitute a first extraction unit that extracts a resistance component signal from the impedance detection signal.

The variable amplifier 22a amplifies the input signal as the first correction means, can transmit an output signal larger than the input signal, and amplifies the signal from the low-pass filter circuit 21a by appropriately weighting it. Also, the amplification constant can be set arbitrarily in advance. In this case, an amplification constant that changes according to the ambient temperature is set.

The synchronous rectifier circuit 19b is connected to the low-pass filter circuit 21b,
1b is connected to the variable amplifier 22b.

Like the low-pass filter circuit 21a, the low-pass filter circuit 21b converts an AC signal into a DC signal by passing a DC and blocking a power supply frequency and its harmonics. In this case, the alternating current converted by the synchronous rectifier circuit 19b is converted into a direct current by converting it into a smooth waveform. The synchronous rectification circuit 19b, the phase correction circuit 20, and the low-pass filter circuit 21b constitute a second extraction unit that extracts a reactance component signal from the impedance detection signal. Therefore, the phase correction circuit 20 belongs to the first extraction unit at a point connected to the synchronous rectification circuit 19a, and belongs to the second extraction unit at a point connected to the synchronous rectification circuit 19b.

The variable amplifier 22b amplifies a reactance component as a second correction means. Here, in the amplification of the resistance component performed by the variable amplifier 22a and the amplification of the reactance component performed by the variable amplifier 22b, the change amount of the resistance component due to the temperature change and the change amount of the reactance component cancel each other. , So that the influence of the temperature change is eliminated.

The adder 23 inputs a signal corresponding to the resistance output from the variable amplifier 22a, and
Are output means for inputting signals corresponding to the reactances output by the control unit, adding up these signals, canceling out unnecessary component signals, and outputting the signals as detection signals.

Thus, the influence of the temperature change can be eliminated. To explain this in detail, as shown in FIG. 3, when this correction is not performed, the temperature is set to −50 ° C.
When the temperature is changed to 100 ° C., the resistance component signal b changes from 3v to 4.4v, and the fluctuation width c increases by 1.4v. On the other hand, the reactance component signal d is changed from 4v to 3.65.
and the fluctuation width e decreases by 0.35 v. As a result,
The phenomenon that the width of the increase in the resistance component signal b greatly exceeds the width of the decrease in the reactance component signal d, and that the impedance value increases as the temperature increases.

However, by performing the above correction, the variation width c of the resistance component signal b and the variation width e of the reactance component signal d have a relationship as shown in FIG. That is, in the correction shown in FIG. 4, the resistance component signal b is not corrected and the variation width c is kept, and the reactance component signal f
Are weighted so that the fluctuation width g is substantially equal to the fluctuation width c of the resistance component signal b. Thus, the sum of the positive fluctuation width c of the resistance component signal b and the negative fluctuation width g of the reactance component signal f is set to 0.

As a result, the magnetic field detection device 10 is not affected by temperature, and can perform accurate detection regardless of whether the temperature is high or low. When the correction of the resistance component signal b is not performed as in this embodiment, the variable amplifier 22a can be omitted from the magnetic field detection device 10.

Conversely, the reactance component d in FIG. 3 remains unchanged without change, and the resistance component signal b has a change width c substantially equal to the change width e of the reactance component signal d. Weighting may be performed so as to have the same value, and the sum of the negative fluctuation width e of the reactance component signal d and the positive fluctuation width of the resistance component signal may be zero. In this case, the variable amplifier 22b can be omitted from the magnetic field detection device 10.

Further, both the variation width c of the resistance component signal b and the variation width e of the reactance component d in FIG. 3 can be corrected so that the sum of the variation widths becomes zero. In this case, it is preferable to set the correction amplification factor of the resistance component signal b to be smaller than the correction amplification factor of the reactance component d.

As described above, according to the magnetic field detecting device 10, it is possible to prevent a detection error due to a difference in temperature characteristics between the resistance component and the reactance component. MI element 1
The magnetic material layers 1 and 11b have the magnetic material layers 15 and 17, respectively.
Since the magnetic anisotropy is provided along the longitudinal directions of Nos. 5 and 17, there is no influence on the temperature characteristics due to domain wall movement.
As a result, a highly accurate magnetic field detection device 10 that is not affected by temperature can be obtained.

Further, the magnetic field detecting device 10 according to the present invention
Any sensor that uses a magnetic field can be used, but in particular, a position sensor, a rotation sensor,
Use for an orientation sensor or the like is preferable.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a magnetic detection device according to an embodiment of the present invention.

FIG. 2 is a perspective view of an MI element.

FIG. 3 is a graph showing a relationship between a resistance component and a reactance component with respect to a temperature before correction.

FIG. 4 is a graph showing a relationship between a resistance component and a reactance component with respect to a temperature after correction.

FIG. 5 is a graph showing the relationship between magnetic field and impedance when the temperature is changed.

[Explanation of symbols]

Reference numeral 10: magnetic field detector, 11a, 11b: MI element, 19
a, 19b: synchronous rectifier circuit, 22a, 22b: variable amplifier, 23: adder, b: resistance component signal, c, e, g: fluctuation width, d, f: reactance component signal.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Koji Aoyama, Toyota-cho, Toyota-cho, Aichi Prefecture, Toyota Motor Corporation (72) Inventor Hironari Matsubara, Toyota-cho, Toyota-cho, Toyota-shi, Aichi Prefecture 72) Inventor Naoki Kawajiri 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Nobuyoshi Sugitani 1 Toyota Town Toyota City, Toyota City Inside Toyota Motor Corporation (72) Inventor Yuji Nishibe Aichi 41 Toyota Chuo Research Institute, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Institute, Inc. (72) Inventor Hideya Yamadera 41 Toyota Chuo Research Institute, Aichi-gun, Nagakute-cho, Aichi-gun Inventor Noriichi Ota 41-41, Chuchu-ji, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Laboratory Co., Ltd. F term (reference) 2F077 AA13 JJ07 TT06 TT13 UU08 2G017 AA02 AB05 AC04 AD01 BA09

Claims (3)

[Claims] 1. A magnetic field detecting device comprising a magnetic detecting element and detecting a change in an electrical characteristic according to an external magnetic field, wherein a first extraction for extracting a resistance component signal from an impedance detection signal by the magnetic detecting element. Means, a second extraction means for extracting a reactance component signal from an impedance detection signal by the magnetic detection element, a resistance component signal extracted by the first extraction means, and a reactance component extracted by the second extraction means Correction means for correcting at least one component signal of the signals so that the sum of the change amount of the resistance component signal and the reactance component signal with respect to the temperature change approaches 0; and the corrected resistance component signal and the reactance component. Output means for adding and outputting a signal. 2. The first correction means for correcting the resistance component signal extracted by the first extraction means, and the second correction means for correcting the reactance component signal extracted by the second extraction means. 2. The magnetic field detection device according to claim 1, comprising: 3. The magnetic field detecting device according to claim 1, wherein the correction amplification factor of the resistance component signal is set to be smaller than the correction amplification factor of the reactance component signal.