JPS61287284A - Magnetic sensor - Google Patents

Abstract

PURPOSE:To enable high identification by forming a raster on only one of a pair of magnetoresistance elements, and preventing the cancelling of outputs when character patterns having equal interval and width to those of the elements are continuously arrived. CONSTITUTION:A raster 5 is formed on only one magnetoresistance element 3 of a magnetic sensor 1 having a pair of magnetoresistance elements 3, 4 secured onto a substrate 2. Here, the raster 5 is mounted in a stripe shape perpendicularly to the longitudinal direction onn the slender substrate 2, the element 3 is equivalent to the series connected magnetoresistance elements having shorter distance between electrodes than the width of the electrodes, thereby increasing the resistance value. The elements 3, 4 are formed on the same substrate, differentially connected to compensate the temperature to one another. Only the element 3 is largely varied in the resistance by forming the raster 5, but the element 4 is not almost altered. Thus, even if equal character pattern are continuously arrived to the width and the interval of the elements, the output can be detected without cancelling each other out.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a magnetic sensor using a magnetoresistive element.

(b) Conventional technology Semiconductors with high carrier mobility such as InSb, In5b-NiSb, InAs or Ni-Co, Ni-F
Ferromagnetic materials such as e, Ni-Fe-Co have the property that the resistance value changes when a magnetic material is applied to it.
Magnetic sensors that utilize this property to detect the presence of magnetism, the presence of magnetic materials, and their movement have been put into practical use.

In general, conventional magnetic sensors (2)
As shown in Publication No. 755, the casing (E) is made of metal and is formed into a rectangular tube shape with one end closed, and the lower end opening is closed with a lid member.1. Inside there are devices such as a mount board t7) and a sensor unit (8).
The remaining space except for the area surrounded by the spacer (9) was filled with synthetic resin. Sensor unit (8
) is formed by fixing a pair of magnetoresistive elements (c), 04) in parallel on the magnetic substrate on the upper surface of the Yaunt board (7) using adhesive resin, and the spacer (9) is formed by fixing a pair of magnetoresistive elements (c), 04) in parallel on the magnetic substrate on the upper surface of the Yaunt board (7). They were placed on all sides.

As shown in Figure 4, the operating principle is a pair of magnetoresistive elements (
c)c! 4) is placed on the magnetic pole face of the magnet and magnetically biased. The magnetic body approaches from below and magnetoresistive element C! At (a), the magnetic flux generated by the magnet concentrates on the magnetic material.

Therefore, the resistance of the magnetoresistive element r24) increases.

When these two magnetoresistive elements (c) (24) are connected as shown in Figure 4 and connected to a constant voltage circuit, an AC signal appears at the output terminal as the magnetic material moves, making it possible to detect the magnetic material. become.

Furthermore, as shown in FIG. 3, a short-circuit stripe called a raster is attached on top of the magnetoresistive element (c) C241 at right angles to the length direction. This is equivalent to magnetoresistive elements connected in series with a distance between the electrodes that is short compared to the width of the electrodes, and at the same time suppresses the Hall electric field and increases the resistance value by connecting many of them. be able to.

Using this method, financial institutions are able to read eight bills, checks, and bills that are printed using special magnetic ink.

(/Co) Problems that the invention aims to solve General banknotes differ in size, color, and ink used - watermarks and other features make them easy to distinguish, but special banknotes differ in size, ink, color, etc. Because they are the same, identification is highly dependent on magnetic patterns using magnetic ink, and there is a need to further improve performance such as resolution and stability over current magnetic sensors.

For example, as shown in Fig. 5, two magnetoresistive elements MR,...
When a character pattern whose width is narrower than the interval p of MR arrives, the output signal waveform temporarily reaches its maximum value and then returns to the zero level. However, as shown in Figure 5), the signal waveform when a character pattern with an interval q and a width S equal to the width r and the interval p of the magnetoresistive elements MR1 and MR, respectively, arrives successively. , is the same as when one wide pattern arrives, and therefore the magnetic sensor detects the upper and lower two types of patterns as being the same.

B) Means for Solving the Problems The present invention has been made in view of the above points, and provides a magnetic sensor (1) having a pair of magnetoresistive elements (3) and (4) fixed on a magnetic substrate (2). ) is solved by forming the raster (5) only on one of the magnetoresistive elements (3).

(E) Effect Here, the raster (5) is attached in a stripe shape on the elongated magnetic substrate (2) at right angles to the length direction, and this magnetoresistive element (3) is This is equivalent to magnetoresistive elements connected in series with a short distance between electrodes, and the resistance value can be increased.

A pair of magnetoresistive elements (3) and (4) are formed on the same substrate and are differentially connected, and since the magnetoresistive elements (3) f41 exhibit the same characteristics, they mutually perform temperature compensation.

Therefore, if the raster (5) is formed only on one of the pair of magnetoresistive elements (31 (41), the resistance of one of the magnetoresistive elements (3) will change greatly, but the resistance of the other (41) will change significantly.
) will hardly change. Therefore, even if character patterns having the same spacing q and width S of the magnetoresistive elements come in succession as shown in FIG. 5), the outputs do not cancel each other out and can be detected.

(v) Example Below, an example of a magnetic sensor related to the present invention is shown in Figure 1.
This will be explained with reference to FIG.

First, a method for manufacturing a pair of magnetoresistive elements (3) and (4) fixed on a magnetic substrate (2) shown in FIG. 1 will be briefly described.

After slicing the InSb ingot into wafers 1 with a thickness of about 300 μm using a diamond tool or the like, a mirror borishing process is performed to remove distortion of the wafers. Next, etching is performed to form a groove in which a copper layer is to be laminated in a raster pattern.

Here, we patterned the photoresist into a desired pattern, and dug grooves (omitted here) in a stripe pattern perpendicular to the length direction on top of the magnetoresistive element (31+41).Next, we used copper sulfate to create an electric field. Plating is performed and copper (5) is laminated in the groove.After removing the photoresist, a magnetoresistive element (InSb wafer) as shown in FIG.
3) (To cut into the shape of 41, photoresist treatment is performed and etched deeper than the groove.

Here, etching is performed by approximately 10 μm. Finally, the InSb wafer is bonded onto the glass substrate using an adhesive, with the surface facing downward, and back-wrapped. The resulting raster (5)
The magnetoresistive element (3) (41) formed with is removed in the shape shown in FIG.

Next, the configuration of the magnetic sensor (1) according to the present invention will be shown.

The casing (6) is made of metal and is formed into a rectangular tube shape with one end closed, the lower end opening is closed with a lid member, and the mount board (7), sensor unit (8), etc. are housed inside. The space other than the part surrounded by the sensor unit (8) and spacer (9) is filled with synthetic resin.

The sensor unit (8) is formed by fixing the pair of magnetoresistive elements (3) (41) in parallel on the magnetic substrate (2) on the upper surface of the mount substrate (7) using adhesive resin, and The magnetoresistive element (31f41) is magnetically biased by the magnet QOI. Spacers (9) are installed on all sides of the sensor unit 7H81. Here, the raster (5) is formed only on one side of the magnetoresistive element (3H41). The other magnetoresistive element may or may not have raster-formed grooves.

Here, the potential distribution of the magnetoresistive element on which the raster (5) is not formed has a property that the potential distribution is higher at both ends of the magnetoresistive element than at the center. Therefore, by utilizing this property and forming the raster (5) on the magnetoresistive element in a stripe shape perpendicular to the length direction, the magnetoresistive elements with short inter-electrode distances can be connected in series. , it is possible to prevent the center voltage from decreasing and further improve the resistance change.

This raster (5) is formed on the same substrate (or separate substrates may be used), and a magnetoresistive element (304J) is formed, and when connected as shown in Fig. 4, it is differentially connected. do.

However, in the above-mentioned relationship, Figures 5(a) to 5(a)
C), but when character patterns with spacing q and width S that are equal to the width r of the magnetoresistive element and the spacing p, respectively, arrive in succession as shown in FIG. 5), the signal waveform is This is the same as when one wide pattern arrives, and therefore, the magnetic sensor detects the upper and lower two types of patterns as being the same.

The feature of the present invention lies in the raster (5), which solves the above problem. In other words, if the raster (5) is formed only on one magnetoresistive element (3) of the pair of magnetoresistive elements (31 (4)), one magnetoresistive element (3) will be thick (resistance will change, but the other 41 hardly changes.Here, the raster (5) may be formed to trap the other magnetoresistive element (4).Therefore, as shown in Fig. 4, the resistance changes of the upper and lower magnetoresistive elements are different, and the (see figure 5)
Even if character patterns having a spacing q and a width S that are equal to the width r of the magnetoresistive element and the spacing p thereof, respectively, arrive in succession, the outputs are not canceled out and can be detected.

(G) Effects of the Invention As is clear from the above description, the present invention is achieved by forming a raster (5) only on one of the magnetoresistive elements (3) of the pair of magnetoresistive elements (3H4). ), the distance q is equal to the width r of the magnetoresistive element and the distance p, respectively.
Even if character patterns having a width S and a width S continuously arrive, the outputs can be detected without canceling each other out, and a higher degree of discrimination can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a partially fragmented plan view of a hunting sensor that is an embodiment of the present invention, Fig. 2 is a partially fragmented side view of a conventional R and a magnetic sensor that is an embodiment of the present invention, and Fig. 3 is a partially fragmented side view of a conventional magnetic sensor that is an embodiment of the present invention. Fig. 4 is a partially fragmented plan view of the magnetic sensor, and Fig. 5 is a circuit diagram of the magnetic sensor.
Figures (a) to 5) are diagrams showing the relationship between character patterns and output signal waveforms. Explanation of the main drawing numbers (1) is a magnetic sensor, (2) is a magnetic substrate, (31 (4
1 is a magnetoresistive element, (5) is a raster, (6) is a housing, (
7) is the Macintosh board, (8) is the sensor unit, (9)
is a spacer, and QO) is a magnet. Applicant Sanyo Electric Co., Ltd. and one other representative Patent attorney Shizuo Sano Figure 2 Figure 5

Claims (1)

[Claims] (1) A magnetic sensor having a pair of magnetoresistive elements fixed on a magnetic substrate, characterized in that a raster is formed on only one of the magnetoresistive elements.