JPS63187159A - Current detector - Google Patents

Abstract

PURPOSE:To achieve thickness reduction and miniaturization and to reduce the number of assembling and adjusting processes, by forming a magnetic resistor element, a membrane yoke and a membrane coil on the same substrate and providing a permanent magnet for applying a bias magnetic field to the back surface of the substrate. CONSTITUTION:When a detection current is supplied to terminals 5, 6, the magnetic field proportional to the ampere-turn of a membrane coil 3 is generated in the gap 21 of the ferromagnetic membrane yoke 2 of a substrate 4 and linearly changes from negative polarity to positive polarity by the bias magnetic field due to the permanent magnet 5 provided to the back surface of the substrate 4 until the yoke reaches a saturated flux. This magnetic field is formed in the gap 21 on the substrate 4 and detected by a bridge circuit consisting of magnetic resistor elements 11, 12 of which the positional accuracy depends on mask accuracy at the time of formation and magnetic resistor elements 13, 14 at a position receiving no effect of a leakage magnetic field or a bias magnetic field. By this method, a current detector becomes thin and small in size, and the number of assembling and adjusting processes are reduced.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to the magnitude and polarity of the current flowing through one circuit in an inverter drive circuit, a printer print head drive circuit, a facsimile telephone line input circuit, etc. This invention relates to a current detector that determines.

<Prior Art> An example of a conventional current detector is shown in FIG. 7, which is partially shown. A coil winding 9 for passing the current to be detected is applied to a ferromagnetic core 7 with an air gap 71 formed in a part of the circumferential magnetic circuit, and the substrate surface is placed near the air gap 71 with a length of , a magnetoresistive element made of a ferromagnetic thin film, also called an MR sensor, is fixed in the Z direction.

FIG. 8 (at is the noso-turn diagram of the magnetoresistive element parallel to the two planes, which is composed of four magnetoresistive element strife '81.82, 83.84 with resistance value R'1R5RζRS, Of these, 81 and 82 are parallel to each other and close to each other (about 50μ apart), while 83°84 is parallel to 81 and 82.
and are oriented at right angles to each other. The magnetoresistive element stripes f81 and f82 are used to sense a magnetic field in a direction perpendicular to their length, while the stripes f83 and 84 are used without sensing a magnetic field. Therefore, the equivalent circuit as a magnetoresistive element is as shown in FIG. 8 (bl).

The position of the magnetoresistive element winding is adjusted so that the magnetoresistive element elements R1 and R2 are substantially parallel to each other along this edge between the side surfaces of both edges of the air gap 710. Therefore, out of the leakage magnetic flux from the air gap 71, Z
A magnetic field in the direction acts on the magnetoresistive element 81.82, producing an output voltage vout. On the other hand, a bias magnet 101 is attached to the back surface of the substrate 10 of the magnetoresistive pre-wound.

A bias magnetic field H6 is applied to the magnetoresistive element elements 81 and 82 as shown in FIG. 8 (al).

FIG. 9 shows the output voltage V for a two-direction parallel magnetic field using only a magnetoresistive pre-winding. ut vs. applied magnetic field characteristics.

Due to the bias magnetic field H'B, the output curve becomes asymmetrical with respect to the positive and negative applied magnetic fields, and the points between points A, B, and C in the 1% curve are used to change the magnitude and polarity of the positive and negative currents.

FIG. 10 shows the output voltage V of the magnetoresistive element winding with respect to the unturned applied to the coil 9 in the conventional example of FIG. 7. u
This shows an example of the characteristics of t. Here, i direction (7) 7
7 The maximum leakage magnetic flux strength at one time is the bias magnetic field H
The magnetic circuit is adjusted so that it saturates below 'B.

From the characteristics shown in FIG. 10, the absolute value and polarity of the current in both positive and negative directions can be determined.

<Problem to be solved by the invention> Here, the gap length of the gap 71 of the ferromagnetic core 7 is usually 100
~200μ, while the spacing between the magnetoresistive elements (81.82) is around 50μ, so that the magnetoresistive element (Ni element) into the air gap 71 edge is 81
, 82 requires an assembly precision of about 10μ, the assembly man-hours and adjustment man-hours are expensive, and the characteristics have a large variation. Also, @ sex body core 7
Since the assembled size of the coil 9 and the coil 9 is larger than that of a normal magnetoresistive element winding (usually about 10 mm square), it has been difficult to miniaturize the current detector as a whole.

Therefore, it is an object of the present invention to improve assembly compared to the prior art.

It is an object of the present invention to provide a current detector that requires fewer adjustment steps, is inexpensive, has less variation in characteristics, and is miniaturized.

<Means for Solving the Problems> According to the present invention, a thin film coil with a gap formed in a part and a multilayer wiring for passing the current to be detected is provided on one surface of the substrate. A ferromagnetic thin film yoke and a ferromagnetic magnetoresistive element magnet in which a pair of magnetoresistive element elements operating as a variable resistance are disposed in the air gap are provided, and the pair of magnetoresistive elements on the other surface of the substrate are provided. A current detector is obtained comprising a biasing permanent magnet in position relative to the magnetoresistive element.

<Example> Fig. 1 is a diagram showing an embodiment of the present invention, Fig. 2 is a sectional view taken at A A' in Fig. 1, and Fig. 3 is a sectional view taken at B in Fig. 1.
The cross-sectional view at B' and FIG. 4 are equivalent circuit diagrams.

A ferromagnetic magnetoresistive element/mother turn 1 and a ferromagnetic thin film yoke of Fe--Ni alloy are formed on the substrate 4 (glass substrate or alumina substrate) by means of vapor deposition or sintering. A thin film coil 1 is formed, and the entire surface of the coil 2 is covered with an insulating protective film 6 (an inorganic film such as a SiO2 film, or an organic film such as a polyimide film, etc.).

A gap 21 is provided in a part of the magnetic circuit of the ferromagnetic thin film yoke 2.
(gap length tg), and magnetoresistive element elements 11 and 12 (resistances are R1 and R2) of the ferromagnetic magnetoresistive element pattern ↓ are arranged in the air gap 21. Fe
-Ni alloy magnetoresistive element elements 11, 12.13
．． 14 are bridge-connected to each other, and the equivalent circuit thereof is as shown in FIG. (However, H is not shown in the figure), while the other opposing magnetic field is detected. Resistance element elements 13 and 14 are located outside the air gap 21, and in the example shown in FIG. do not. In addition.

The elements 13 and 14 do not necessarily have to be in the rectangular direction as long as they are located at positions where no magnetic field is detected.

As shown in the cross-sectional view in FIG. 2 (direction AA' in FIG. 1).

A bias permanent magnet 5 is attached to the back surface of the substrate 4 in the vicinity of the gap 21 using an adhesive or the like, and a bias magnetic field HB is always applied in a direction perpendicular to the length direction of the magnetoresistive element Niremen 1-11.12. ing. Note that in this case as well, H indicating the magnetic field from the ferromagnetic yoke 2 is omitted. The film thickness of the magnetoresistive element 11゜12.13.14 is usually selected to be around 500X, and the thickness of the ferromagnetic yoke 2 is
At least twice the film thickness of the magnetoresistive element (1000λ
above). The width of the magnetoresistive element 11.12 is about 10 to 20 microns, the length is about 1 inch, and the spacing between each element is usually selected to be 40 to 50 microns.

The gap length tg of the gap 21 is set to a value as small as possible without interfering with the P-turn wiring of the magnetoresistive element ↓, and is usually approximately 100 μm.

In FIG. 3, which shows the cross section of the thin film coil 3, the first layer thin film coil No'? An insulating protective film 61 such as S+02 is formed on the turn 31, a ferromagnetic thin film yoke 2 is formed on it, and then a second insulating protective film 62 and a second layer of thin film coil/ξ turn are formed. 32 is formed. Here, the width of the insulating protective films 61 and 62 is slightly larger than the width of the ferromagnetic thin film yoke 2, and therefore, the outer end portions of the yoke 2 of the thin film coil grooves 31 and 32 are insulated. There is no protective film, and the thin film coil patterns 32 of the second layer are diagonal.
1.32 are electrically connected to form a coil with several turns per turn (usually 10 to 20 turns).

With the above configuration, a magnetomotive force is generated against the ferromagnetic thin film yoke 2 by passing the detection current wire through the terminal 5. A @ field proportional to is generated and the yoke material (Fe-
Nj) increases almost linearly until it reaches the saturation magnetic flux.

FIG. 5 is a diagram showing the relationship between the magnetic field generated in the air gap 21 and the ampere turns of the thin film coil 1. Here, the saturation magnetic field strength H1 is set to be slightly smaller than the bias magnetic field strength HB (set by adjusting the width or film thickness of the yoke 2).

Figure 6 shows the output voltage Vout of the magnetoresistive element↓ in Figure 1.
(Terminal 2-3) This is a diagram showing the relationship between the ampere turns of the thin film coil l. From the relationship H4≦HB, it is almost linear in the positive direction and negative direction AT (between -AT and +AT). A good relationship can be obtained. Therefore, the linear range E, F, G
Any threshold voltage between v4. If v5 is selected, the corresponding positive direction ampere turn +AT4 and negative direction ampere turn -AT5 can be detected.

In relation to the number of turns n, the current between 5 and 6 in FIG. 1 can be distinguished between positive and negative polarities.

As can be seen from the above explanation, the magnetoresistive element Niremen) 11
．． The relative relationship between the thin film yoke 12 and the gap 21 of the thin film yoke 2 depends on the accuracy of alignment of pattern masks during film production, and an accuracy of several microns can be obtained extremely easily. Therefore, the accuracy required for the conventional device shown in FIG. 7 can be easily obtained, almost no assembly man-hours are required for positioning, and the variation in characteristics is significantly improved.

Furthermore, the device shown in FIG. 1 has a magnetoresistive element on the same substrate.

Since a thin film yoke and a thin film coil are formed, the structure is thinner and clearly smaller than the conventional example. It should be noted that, although the above-mentioned Example Vi describes the case where direct current is detected, it goes without saying that even alternating current can be used.

<Effects of the Invention> According to the present invention, it is possible to provide a small current detector that requires fewer assembly and adjustment steps than conventional current detectors, is lower in cost, has less variation in characteristics, and is thinner. It is.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing one embodiment of the present invention, Fig. 2 is a sectional view of A A' in Fig. 1, and Fig. 3 is a sectional view of B B' in Fig. 1.
4 is an equivalent circuit diagram of the magnetoresistive element in FIG. 1, FIG. 5 is a diagram showing the yoke air gap direction magnetic field versus coil unturning characteristics in FIG. 1, and FIG. Figure 7 is a diagram showing the turn characteristic of the magnetoresistive element output voltage versus coil angle, Figure 7 is a diagram showing an example of a conventional example, Figure 8 (al is the turn diagram of the magnetoresistive element, Figure 8 ( bl is its equivalent circuit diagram, and Fig. 9 is a diagram showing the output voltage of the magnetoresistive element versus applied magnetic field characteristic. Fig. 10 is a diagram showing the output voltage of the magnetoresistive element in Fig. 7 versus coil unturning characteristic Explanation of symbols: 1 is a magnetoresistive element pattern, 11° 12.
13.14 is a magnetoresistive element element, 2 is a ferromagnetic thin film yoke, 21 is an air gap, Good is a thin film coil, 31.32 is a thin film coil pattern, 4 is a substrate, 5 is a bias permanent magnet, 6.61.62 is a Insulating protective film, 7 is a ferromagnetic core, 7
1 is the air gap, dan is the magnetoresistive element, 81, 82, 83.84
9 is a magnetoresistive element stripe, 9 is a coil, and 10 is a substrate. 101 is a bias magnet, H is a magnetic field (from a ferromagnetic thin film yoke), HB is a bias magnetic field, and Hl is a saturation magnetic field strength. Figure 1 Figure 2 1\zl Figure 3 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure with bias magnet Figure 10

Claims (1)

[Claims] 1. A ferromagnetic thin film yoke with a gap formed in a part on one side of the substrate and a thin film coil with multilayer wiring for passing the current to be detected in the main part, and a pair of thin film coils that operate as variable resistors. a ferromagnetic magnetoresistive element pattern in which a magnetoresistive element is arranged in the air gap; and a bias permanent magnet is provided at a position relative to the pair of magnetoresistive elements on the other surface of the substrate. vessel.