JPH0258561B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a displacement detection device that utilizes changes in resistance of a magnetic thin film resistor depending on the presence or absence of a magnetic field.

A conventional displacement detection device using magnetic thin film resistors has magnetic thin film resistors 1 ₁ , 1 ₂ as shown in FIG.
is used to construct a bridge circuit and extract an output voltage related to the amount of displacement of the magnet 2 that applies a magnetic field to the magnetic thin film resistors 1 ₁ and 1 ₂ .This displacement amount detection device detects displacement in an analog manner. Since it is a detection method, it has the following drawbacks.

(1) The linearity of the output characteristics is poor because the amount of change in the resistance value of the magnetic thin film resistors 1 ₁ and 1 ₂ due to the magnetic field is not uniform.

(2) In order to improve the linearity in (1) above, the shape of the magnetic thin film resistors 1 ₁ and 1 ₂ must be slightly changed, but since they are continuous shapes, it is extremely difficult to change the shape and the linearity cannot be improved. is difficult to correct.

(3) For the same reason as (2) above, it is difficult to obtain arbitrary output characteristics such as characteristics A to D shown in FIG. 2 and to correct the characteristics.

(4) Since minute changes in the conditions during the manufacturing of the magnetic thin film resistors 1 ₁ and 1 ₂ bring about large differences in the amount of change in the resistance value of the magnetic thin film resistors 1 ₁ and 1 ₂ , it is difficult to reproduce the output characteristics during mass production. Bad sex.

In FIG. 1, R _D and R _E are resistors forming the bridge circuit, V _cc is the power supply voltage, and V _put is the output voltage.

In view of the above points, the present invention provides a displacement detection device that can easily improve linearity and correct characteristics by digitally detecting displacement, and can easily obtain arbitrary output characteristics. The purpose is to

In order to achieve this object, the present invention provides a group of magnetic thin film resistors in which a plurality of magnetic thin film resistors whose resistance values change depending on a magnetic field are arranged side by side, a reference resistor, and a magnetic thin film resistor that moves over the magnetic thin film resistors. A displacement amount detection device comprising a magnet and a means for comparing the parallel resistance value of a group of magnetic thin film resistors that changes due to the movement of the magnet with the resistance value of a reference resistor and detecting the amount of displacement of the magnet as a change in the corresponding electric quantity. It consists of the following:
An example will be explained.

FIG. 3 is a configuration diagram showing an embodiment of the present invention. In the figure, 3 ₁ , 3 ₂ , ... 3 _o are magnetic thin film resistors whose resistance values change depending on the magnetic field, and are arranged at equal intervals. , its both ends are conductor 4 ₁ ,
4 Connected to public service by ₂ . A reference resistor 5 is arranged parallel to the conductors 4 ₁ and 4 ₂ and is made of _a magnetic thin film resistor in this embodiment.
Conductor 4 is connected between ₃ . Reference numeral 6 on which these are provided is a substrate. A voltage V ₁ is applied to the conductor 4 ₂ , and the conductors 4 ₁ and 4 ₃ are connected to respective input terminals of the differential amplifier 7 . Note that R _A and R _B are resistances.

Now, if the magnets 8 ₁ and 8 ₂ are arranged as shown in FIG. 4 and the magnet 8 ₁ is moved in the direction of arrow M over the magnetic thin film resistors 3 ₁ , . . . , 3 _o , the output voltage of the differential amplifier 7 will be _Vput changes depending on the amount of movement (displacement) L of the magnet. The magnets 8 ₁ and 8 ₂ are arranged so that a magnetic path is formed in the direction of the arrow M of the magnetic thin film resistors 3 ₁ , . . . , 3 _o .

FIG. 5 is an output characteristic diagram showing an example of the relationship between the amount of displacement and the output voltage V _put , and is a digital approximation of the linear output characteristic. This degree of approximation can be increased to any degree by increasing the number of magnetic thin film resistors. For example, if 100 magnetic thin film resistors are installed, the output error at any displacement amount will be less than ±0.5% from the ideal value. Therefore, the nonlinearity of the analog detection method is ±
This is superior compared to only a few percent.

Next, the operating principle will be explained. Here, the individual magnetic thin film resistors 3 ₁ ,..., 3 _o are in the absence of a magnetic field.
It is assumed that each magnetic thin film resistor 3 ₁ , . . . , 3 _o has a resistance value of R ₀ and changes to a resistance value of R ₁ by applying a magnetic field. Further, the reference resistor 5 has a resistance value corresponding to n/R ₀ and is made of a magnetic thin film resistor in this embodiment, so that it is disposed at a position where it is not substantially affected by the magnetic field.

Assuming that a magnetic field is now applied to the magnetic thin film resistors 3 ₁ ,..., 3 _i , the output voltage of the differential amplifier 7 is
V _put is calculated as follows.

In other words, Fig. 3a is equivalently shown as Fig. 3b.
become that way. However, in the figure, Rx indicates the ladder-like composite resistance value of the MR elements, and Ry indicates the reference resistance value.

Here, since almost no current flows through the input terminals of the differential amplifier, V ₁ −Vx/Rx=Vx−Vout/R _A ……(1) V ₁ −Vy/Ry=Vy/R _B ……( 2) From equations (1) and (2), Vout is: Vout=R _A {V ₁ /V _Y (1/R _X +1/R _A )/1/R _Y +1/R _S
-R ₁ /Rx}...(3) At this time, the resistance value Rx of the ladder-shaped MR element is as shown in Fig. 3c, where R ₀ is the resistance value when the magnetic field O is on one bare side, and R ₁ If is the resistance value of one bare side when the magnetic field is saturated (reference resistance Ry=R ₀ /n), then 1/Rx=1/R ₁ /i+1/R ₀ /n-i=i/R ₁ +n
−i/R ₀ 1/Ry=1/R ₀ /n=n/R ₀ ...(4) (Set reference resistance Ry=R ₀ /n) Substituting equation (4) into equation (3), we get Vout=R _A・V ₁・i (1/R ₀ −R _B −1/R ₁・R _B )/n/R ₀
+1/R _B ......(5) Here, if R _A = R _B , Vout = V ₁・i (1/R ₀ -1/R ₁ )/n/R ₀ +1/
In other _words , if V ₁ (1/R ₀ -1/R ₁ )/n/R ₀ + 1/R _B =k (constant of proportionality), the output will be Vout=k・i, which is proportional to the amount of displacement i. Voltage is output.

Note that the values of the individual magnetic thin film resistors can be easily corrected to be uniform by trimming, and therefore the reproducibility of the output characteristics is excellent even when mass-produced. Furthermore, in this embodiment, since the reference resistor 5 is composed of a magnetic thin film resistor, it can be formed at the same time as the magnetic thin film resistors 3 ₁ , ..., 3 _o during manufacturing, and therefore the temperature coefficients are also the same. Therefore, there is no need for temperature compensation. It goes without saying that the reference resistor 5 may be formed of a material other than a magnetic thin film resistor, and in that case, it is desirable from the point of view of temperature compensation to form it with a material that has as similar a temperature coefficient as the magnetic thin film resistor. .

Next, a second embodiment of the present invention will be described.
This second embodiment makes it possible to obtain arbitrary output characteristics as shown in FIG. For example, if you want to obtain an output characteristic as shown in Figure 6, that is, a part of the basic output characteristic shown by the broken line with a dead zone, the first stage as shown in Figure 7. A magnetic thin film resistor _3A1 with a width W and a resistance value R is arranged, and by not placing magnetic thin film resistors in the second and third stage positions, the output of the first stage is maintained. A dead zone is formed, and a magnetic thin film resistor 3 A ₄ having a width of 3 W and a resistance value of R/3 is placed at the fourth stage position so that the output increases by three stages. Hereinafter, magnetic thin film resistors 3A ₅ , 3 having the same width and resistance value as the magnetic thin film resistor 3A ₁ will be described.
By arranging A ₆ and 3A ₇ at the positions of the fifth stage, the sixth stage, and the seventh stage, the characteristics shown in FIG. 6 can be obtained.

Figure 8 shows another modification of the shape of the magnetic thin film resistor, showing the first, fourth, fifth and sixth stages.
Step, resistance value 3R, R, 3R, 3R, at the 7th step position.
3R magnetic thin film resistors 3B ₁ , 3B ₄ , 3B ₅ , 3B ₆ ,
_3B7 , and its resistance ratio is the same as that shown in Figure 7.

FIG. 9 shows another output characteristic, and FIG. 10 shows the arrangement of the magnetic thin film resistors to obtain the output characteristics shown in FIG. ₉ . The resistance values of 3C ₂ , 3C ₃ , 3C _o-1 , and 3C _o are R, R, R/5, R, and R.

Fig. 11 shows the curved output characteristics, and Fig. 12 shows the arrangement of the magnetic thin film resistors to obtain the output characteristics shown in Fig. ₁₁ . , 3D ₂ , ..., 3D ₉ have gradually smaller resistance values.

FIG. 13 shows a third embodiment of the present invention. Whereas the first and second embodiments are suitable for cases where the amount of change is a straight line, this embodiment is suitable for cases where the amount of change is a straight line. Suitable for things that measure displacement.

In this embodiment, magnetic thin film resistors 3E ₁ , 3E ₂ , ..., 3E _o are arranged on the circumference as shown in the figure,
Further, the magnet 8A ₁ has an arc shape and is configured to move over the magnetic thin film resistors 3E ₁ , . . . , 3E _o arranged on the circumference. With this configuration, an output voltage _Vput proportional to the rotation angle (displacement amount) of the magnet _8A1 can be obtained. In addition, 4A ₁ , 4A ₂
is a conductor formed in an arc shape, 5A is a reference resistor formed in a circular diameter shape, and O is a rotation center.

Since the displacement detection device of the present invention is configured as described above, it is possible to easily obtain any output characteristic, and it is also possible to easily correct the output characteristic such as improving linearity. is expensive.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a conventional analog displacement detection device, Figure 2 is a diagram of various output voltage-displacement characteristics,
FIG. 3a is a configuration diagram of an embodiment of the displacement detection device of the present invention, FIG. 3b is a circuit diagram equivalently showing the same embodiment, and FIG. 3c is a ladder-shaped MR in the same embodiment.
A circuit diagram equivalently showing the element, FIG. 4 is a front sectional view showing the arrangement of magnets in the same embodiment, FIG. 5 is an output voltage-displacement characteristic diagram in the same embodiment, and FIG. 9 and 11 are characteristic diagrams when the output voltage-displacement characteristics of the embodiment shown in FIG. 3 are variously changed; FIGS. 7 and 8;
6, 9, and 11 respectively.
FIG. 13 is an arrangement diagram of a magnetic thin film resistor for obtaining the characteristics shown in the figure, and FIG. 13 is a diagram showing a main part configuration in another embodiment of the present invention. 3 ₁ ,..., 3 _o , 3A ₁ ,..., 3A ₇ , 3B ₁ ,...,
3B ₇ , 3C ₁ ,..., 3C _o , 3D ₁ ,..., 3D ₉ , 3
E ₁ ,...,3E _o ...Magnetic thin film resistor, 4 ₁ , 4 ₂ , 4
₃ , 4A ₁ , 4A ₂ ... conductor, 5, 5A ... reference resistor, 7 ... differential amplifier, 8 ₁ , 8A ₁ ... magnet.

Claims (1)

[Scope of Claims] 1. A magnetic thin film resistor group comprising a plurality of magnetic thin film resistors whose resistance value changes depending on a magnetic field, arranged side by side;
Comparing the reciprocal of the parallel resistance value of a reference resistor, a magnet moving on the magnetic thin film resistor, and the group of magnetic thin film resistors that changes due to the movement of the magnet with the reciprocal of the resistance value of the reference resistor, A displacement detection device comprising means for detecting the displacement of the magnet as a change in a corresponding quantity of electricity. 2. The displacement amount detection device according to claim 1, wherein the ratio of change in resistance value to the amount of movement of the magnet is changed by changing the arrangement interval, width, or length of each magnetic thin film resistor. 3. The displacement detection device according to claim 1, wherein the magnetic thin film resistors are arranged on the circumference. 4. The displacement detection device according to claim 1, wherein the reference resistor is a magnetic thin film resistor and is arranged at a position where it is not substantially affected by the magnetic field due to the movement of the magnet.