JPS61120902A - Magnetic detecting apparatus - Google Patents

Abstract

PURPOSE:To improve DC drift and distortion of a detecting signal of MR element for signal detection by inserting at least a pair of ferro-magnetetic film resistance elements for signal detection and installing on both sides of them at least a pair of compensating MR elements. CONSTITUTION:An MR sensor is composed, on a surface of a substrate 33, of signal detecting MR elements 2-7, compensating MR elements 27, 28 and terminals 8-32. The elements 2-7 are installed with elements 2 and 5 constituting a pair with the distance of 1/2 P of a pitch P of magnetic pole teeth, representing the specimen. A 1/3 P distance arrangement is organized together with the elements 2 and 4, as well as 4 and 6, and as a result, from the output terminal, 22-24 3-phase output signals with each deviation by 120 deg. are obtained. Further, distribution of temperatures of the MR elements 2-7 can made constant, by heating again the outside elements 2-7 by the heat of the outside elements 27, 28. Further, the elements 27, 28 are arranged on the outer side of the elements 2-7 which have already been arranged on the outside of the elements 2-7 and consequently, magnetic balance of the elements 2-7 are improved and the disturbance of the magnetic field is reduced to a minimum.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a detection device used for detecting the moving distance of a linearly moving object and the rotation angle of a rotating object. The present invention relates to a device for detecting magnetic pole teeth (tooth-like irregularities made of a magnetic material) using a ferromagnetic thin film resistance element (hereinafter referred to as an MR element) having a magnetoresistive effect.

Conventional technology In recent years, M
The number of devices using R elements is increasing.

In light of these trends, the present inventor used an MR element to
As a device for detecting magnetic pole teeth that move relative to this, Japanese Patent Application No. 59-12302 and Japanese Patent Application No. 59-205
This was proposed in Specification No. 807.

The technique of the above-mentioned prior application will be described below as an example of a conventional detection device with reference to the drawings.

3, 4, and 6 show an example of a detection device using a conventional MR element for signal detection.
FIG. 4 is an explanatory diagram of the configuration and electrical connection relationship of the sensor, FIG. 4 is a configuration diagram of main parts of the detection device, and FIG. 6 is a magnetic field-resistance value characteristic diagram of the MR element for signal detection. In addition, the same numbers are given to the same components in each figure.

In FIG. 3, the MR sensor 1 includes signal detection MR elements 2, 3, 4, 5, 6°7 and terminals 8, 9 on the surface of a substrate 33.
, 10, 11.12. i3,14°15.16,17.
18.19, and each MR element and terminal are electrically connected as shown in FIG.
is connected to constant voltage 21. In addition, M for each signal detection
In the R element, the pitch of the magnetic pole teeth, which is the object to be detected, is P.
A pair of signal detection MR elements 2 and 6 (or 3 and 6, or 4 and 7) are arranged with an interval of T-P, and signal detection MR elements 2 and 4 and 4 and 6 (or 3 and 5 and 5 and 7
) are arranged with a spacing of −p between them, resulting in output terminals 22 , 23 .

The configuration is such that a three-phase output signal whose phase is shifted by 1200 from 24 can be obtained. However, each signal detection MR element has a so-called magnetic field, in which the resistance value changes according to changes in magnetic field strength in the ±X directions in the figure, and the resistance value hardly changes with respect to changes in magnetic field strength in other directions. It has an anisotropic effect.

FIG. 4 shows a detection device using the MR 7-naner 1 shown in FIG. 3, where FIG.

This detection device detects the relative position of the movable part 34 when moving linearly along the fixed part 26, and the movable part 34 is connected to the MR sensor 1 for supplying a bias magnetic field. On the other hand, the fixed part 26 has a surface facing the movable part 34 with an uneven pitch of P.
magnetic pole teeth are formed. Furthermore, the movable part 34 and the fixed part 26 are arranged as shown in FIG.
are arranged parallel to the fixed part 26. Incidentally, the electrical connection relationship of each signal detection MR element shown in FIG. 3 is omitted in FIG. 4 because it would clutter the drawing.

The operation of the detection device configured as described above will be described below.

First, considering the case where the movable part 34 moves in the ±X' direction along the fixed part 26 in FIG. It is affected by the shape and its direction is periodically bent. Because the lines of magnetic force are bent, they now include a component in the magnetic sensing direction (±X direction) for each signal detection MR element (hereinafter, this component is referred to as the signal magnetic field).
.

In addition, since each MR element and the magnetic pole teeth are inclined at an angle of α0 as shown in this figure, the lines of magnetic force generated upward from the permanent magnet 26 have a certain magnetic susceptibility to each signal detection MR element from the beginning. It gives a directional component (offset magnetic field). this is,
On the magnetic field-resistance value characteristic diagram shown in FIG. 6, it means the following. Each signal detection MR element of the MR sensor 1 has characteristics as shown in FIG. 6 with respect to the applied external magnetic field in the ±X direction. In the figure, a, c, and e are nonlinear regions,
b, (1 indicates a region with good linearity. When the angle α0 is zero, the signal magnetic field changes around the magnetic field 0, so there is a nonlinear region in the magnetic field-resistance value characteristic of the MR element for signal detection. C will be used, but when the angle α0 is set to an appropriate value, the operating point of each signal detection MR element will be 1Hxl
), and since the above-mentioned signal magnetic field changes around the operating black, it is used in the region d where linearity is good in the magnetic field-resistance value characteristic of the MR element for signal detection.

Problems to be Solved by the Invention The magnetic field-resistance characteristic of the above-mentioned signal detection MR element has a temperature characteristic. However, since the temperature characteristics of multiple signal detection MR elements formed close to each other on the same substrate are well matched, it is not possible to use two signal detection MR elements in a half-bridge like in conventional detection devices. As a result, it was possible to obtain an output signal with small DC drift from each output terminal in response to changes in ambient temperature.

However, each signal detection MR element generates self-heating due to current. In particular, when a large number of signal detection MR elements are arranged on the same substrate as in the conventional example shown in FIG. MR element 2. The temperature is often lower in A.

The DC drift of the output signal caused by this may amount to about 10% of the output signal amplitude.

Furthermore, the magnetic lines of force generated by the permanent magnet 26 change under the influence of the magnetic pole teeth, but are also influenced by the signal detection MR element, which is a magnetic material, placed in the magnetic field. For this reason, it is desirable to arrange the MR elements for signal detection at equal intervals in a well-balanced manner, but as can be seen from the conventional example in Fig. 3,
The signal detection MR elements 2 and 7 at both ends have poor left and right balance, and disturbances in the signal magnetic field are likely to occur. As a result, there was a problem in that the output signal was distorted.

In view of the above problems, the present invention improves the DC drift of the output signal due to self-heating of the MR element for signal detection, and further reduces the distortion caused by the disturbance of the signal magnetic field by the MR element for signal detection, thereby achieving high accuracy. The present invention provides a magnetic detection device that is suitable for use in magnetic fields.

Means for Solving the Problems In order to solve the above problems, the magnetic detection device of the present invention includes:
This device has a configuration in which at least one pair of signal detection MR elements is sandwiched between them, and at least one pair of compensation MR elements is disposed on both sides thereof.

Function The present invention utilizes the self-heating generated by the current of the above-mentioned compensation MR element, and uses it as a kind of electric heater to heat a plurality of signal detection MRs sandwiched between the pair of compensation MFt elements. The temperature distribution of the element can be made uniform.

In other words, in the conventional multiple signal detection MR elements arranged on the same substrate, those arranged on the outside have a lower temperature than those arranged on the inside, so the outer signal detection MR elements are further The temperature distribution of each signal detection MR element is made uniform by heating the compensation MR element disposed outside by generating heat. Thereby, the DC drift of the output signal, which has been a problem in the past, can be reduced.

In addition, since the compensation MR element is placed further outside the signal detection MR element placed outside, the left and right magnetic balance of the signal detection MR element is improved, and the disturbance of the magnetic field here is improved. It becomes less.

As a result, distortion of the output signal, which has been a problem in the past, can be reduced.

EXAMPLE Hereinafter, an example of the magnetic detection device of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory diagram of the configuration and electrical connections of an MR sensor used in a magnetic detection device according to an embodiment of the present invention. In this figure, the same components as those in the conventional example shown in FIG. 3 are given the same numbers.

In FIG. 1, the MR sensor 36 includes signal detection MR elements 2, 3, 4, 5, 6 degrees γ on the surface of a substrate 33, compensation MR elements 2, 28, and terminals 8, 9 degrees 10, 11. .12,
13,14,16,16゜17.18,19,29,3
0, 31.32, and each signal detection and compensation MR element is electrically connected as shown in the figure. In particular, terminals 8, 10, 12. ,
Terminals 9, 11, 13, 30 are connected to a constant voltage 21. In addition, each signal detection MR element has a pitch of 7-p between a pair of signal detection MR elements 2 and 6 (or 3 and 6, or 4 and 7), where P is the pitch of the magnetic pole teeth that are the object to be detected. The signal detection MR elements 2 and 4 and 4 and 6 are arranged at intervals of
(or 3 and 6 and 6 and 7) are arranged at an interval of 711 P, and as a result, a three-phase output signal whose phase is shifted by 1200 from the output terminals 22, 23, and 24 is obtained. There is. Further, the compensation MR elements 27 and 28 are arranged on both sides of each signal detection MR element, and
In this embodiment, the interval between the signal detection MR element 2 and the compensation MR element 27 is the same as the arrangement interval of each signal detection MR element. Further, in this embodiment, the compensation MR elements 27 and 28 are the same as the respective signal detection MR elements.

FIG. 2 shows an embodiment of the magnetic detection device of the present invention.
Figure 1 is a plan view, and Figure B is a sectional view taken along the line T-T of the body. In addition,
This magnetic detection device is the MR sensor 3S explained in FIG.
are used, and identical component parts have the same part number.

In FIG. 2, this detection device detects the relative position of the movable part 36 when it moves linearly along the fixed part 25, and the movable part 36 is connected to the M as described in FIG.
R sensor 35 and permanent magnet 2 for supplying bias magnetic field
6, while the fixed part 26 is configured to include a movable part 36
Magnetic pole teeth with an uneven pitch of P are formed on the surface facing the .

Furthermore, the movable part 36 and the fixed part 26 are arranged as shown in FIG.
The permanent magnet 26 is arranged parallel to the fixed part 26. Further, although not shown, a travel holding system for holding the movable part 36 so as to be movable along the fixed part 26 is provided. Note that the electrical connection relationships of the signal detection and compensation MR elements shown in FIG. 1 are omitted in FIG. 2 to avoid cluttering the drawing.

The operation of the magnetic detection device configured as described above will be described below with reference to FIGS. 1 and 2. However, since the basic signal detection (magnetic pole tooth detection) principle of this magnetic detection device is the same as that of the conventional example shown in FIGS. 3, 4, and 6, it will not be described here.

In the magnetic detection device of the present invention, in this embodiment, the compensation MR elements 2γ, 28 are the signal detection MR elements 2, 3, 4.
, 5, 6.7 have the same material, the same shape, and the same magnetic field -
Has resistance value characteristics. In addition, the compensation MR element 27.28
When connected to a constant voltage 20.21 common to each signal detection MR element, it self-heats almost in the same way as each signal detection MR element. As a result, the temperature of each signal MR element disposed between the pair of compensating Ml'l elements 26 and 27 can be made uniform. Specifically, in order to solve the conventional problem that the temperature of the outer MR elements 2 and 7 of each signal MR element is lower than that of the inner MR elements 4 and 5, the above-mentioned compensation MR element The self-heating of the elements 26 and 27 is used to heat the signal detection MR elements 2.7, and as a result, the temperature of each signal detection MR element is made uniform.

As a result, the temperature drift of the output signals obtained from the output terminals 22, 23, and 24 is reduced, and a highly accurate magnetic detection device can be realized.

In addition, among the MR elements for signal detection as magnetic materials, 2 and 7 are arranged at the outermost position with the worst magnetic balance.
As shown in FIGS. 1 and 2, the poor magnetic balance is improved by the compensating MR element 26.2 placed further outside, and the disturbance of the magnetic field here is reduced. Ru. This improves the distortion of the output signals obtained from the output terminals 22, 23, and 24.

Moreover, each signal detection and compensation MR element and each terminal are
Since they are simultaneously formed on the substrate 33 by, for example, a method such as vapor deposition, the cost remains unchanged compared to the conventional method by adding a compensating MR element.

In this embodiment, the compensating MR element and the signal detecting MR element are identical, and the same constant voltage source is used as the power source, but the present invention is not limited to this. The purpose is to make the temperature distribution of multiple signal detection MR elements uniform and to improve the magnetic balance. For example,
By changing the shape of the compensation MR element and changing its resistance value,
It is also possible to appropriately adjust the amount of heat generated here. Furthermore, for the same purpose, the distance from the compensation MR element to the signal MR element is changed. It is also possible to control the voltage of the constant voltage power supply of the compensating MR element.

Effects of the Invention As described above, the present invention can make the temperature of each signal detection MR element uniform and improve the magnetic balance with a simple configuration in which at least one pair of compensation MR elements is provided. , Thereby, it is possible to improve the DC drift and distortion of the detection signal of the MR element for signal detection.

[Brief explanation of the drawing]

Fig. 1 is a front view of an MR sensor used in a magnetic detection device according to an embodiment of the present invention, Fig. 2 is a plan view showing an embodiment of the magnetic detection device of the present invention, and Fig. 2B is the same. Figure T
- T-line sectional view, Figure 3 is a front view of an MR sensor used in a conventional magnetic detection device, Figure 4 is a plan view of a conventional magnetic detection device, and Figure 4B is a person's S -S line sectional view and FIG. 6 are magnetic field-resistance value characteristic diagrams. 2.3, 4, 5, 6.7... MR element for signal detection (ferromagnetic thin film resistance element), 20, 21... Constant voltage, 27.28...・Compensating MR element (ferromagnetic thin film resistance element), 26... Fixed part, 26...
...Permanent magnet, 33...Substrate, 35...
...MR sensor, 36...Movable part, P...
...Magnetic pole tooth pitch. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Fig. 10×-× Fig. 2 Fig. 3

Claims (3)

[Claims] (1) The structure includes first means and second means for performing relative movement while maintaining a constant gap, and the first means includes magnetic pole teeth formed at a constant pitch and made of a magnetic material. The second means includes a plurality of ferromagnetic thin film resistance elements having a magnetic anisotropy effect formed on the same substrate, and a permanent magnet that applies a magnetic field to the ferromagnetic thin film resistance elements, The magnetic thin film resistance element is disposed in a magnetic field between the magnetic pole teeth and the permanent magnet, and is disposed at a certain inclination angle with respect to the forming surface of the magnetic pole teeth, and further includes the plurality of ferromagnetic thin film resistors. The element includes at least one pair of signal detection ferromagnetic thin film resistance elements arranged at an interval of (n+(1/2)) P (n: integer), where the pitch of the magnetic pole teeth is P, and the signal detection element. At least one pair of compensation ferromagnetic thin film resistance elements are arranged on both sides of the detection ferromagnetic thin film resistance element, each pair of signal detection ferromagnetic thin film resistance elements being connected in series at one end. , an output signal is obtained from the connection point, and constant voltage E_1 and constant voltage E_ are obtained at the remaining two terminals.
2, the at least one pair of compensating ferromagnetic thin film resistance elements are connected in series at one end, and the remaining two ends are connected to a constant voltage E_3 and a constant voltage E_4. (2) Constant voltage E_1 and constant voltage E_3 are equal, and constant voltage E
2. The magnetic detection device according to claim 1, wherein _2 and constant voltage E_4 are equal. (3) The magnetic detection device according to claim 1, wherein the compensation ferromagnetic thin film resistance element is made of the same material as the signal detection ferromagnetic thin film resistance element and has the same shape.