JPS6123822Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a differential magnetic sensor using a magnetoresistive element. More specifically, the present invention relates to a differential magnetic sensor that achieves high resolution by matching the magnetoresistive pattern of a magnetoresistive element to the magnetic signal pattern in order to obtain a magnetic signal from a regular magnetic signal pattern.

The operating principle of a differential magnetic sensor will be briefly explained. What is shown in FIG. 1 is the configuration of a commonly used magnetic sensor. Two magnetoresistive elements 1 and 2 with equal characteristics are connected in series and a magnet is placed close to them so that the magnetic flux leaking from the magnets evenly crosses the two magnetoresistive elements. The magnetoresistive element is the first
When connected as shown in Figure B, a voltage 1/2 of the applied voltage is obtained at the intermediate tap (outpu terminal).

Magnetoresistive elements made of materials such as InSb are well known, and have the characteristic that the resistance value changes when the magnetic flux density across the element changes. As shown in FIG. 1, when a magnetic material with high magnetic permeability approaches the magnetoresistive element of this magnetic sensor, the leakage magnetic flux of the magnet is disturbed. In the case shown in the figure, since the magnetic flux gathers on the magnetic material piece, the magnetic flux density crossing the magnetoresistive element 1 increases, and the resistance value of the element 1 increases. Therefore, the figure
The potential of the output terminal decreases. This magnetic piece is
As it moves in the direction, the potential at the output terminal changes as shown in FIG.

As explained above, magnetic bias is not only necessary for detecting unmagnetized magnetic materials, but also essential for increasing the sensitivity of magnetic sensors to a practical level. It is known that connecting two wires 1 and 2 is effective for stabilizing the output of the magnetic sensor, such as compensating for temperature changes in the magnetoresistive element. This magnetic sensor is used for detection of weak magnetic materials such as magnetic ink, detection of rotation, position and coordinate detection, feedback elements of servomechanisms, and pulse generators.

However, current magnetic sensors of this type cannot detect objects (signal sources) with minute structures. For example, when detecting the position (or rotation) by attaching magnetic bodies at equal intervals to a mechanical part that moves in parallel (or rotates), the pitch of the signal source is approximately 1 digit/mm with the currently used sensors. be. This is due to the following circumstances. FIG. 3 shows an example of a pattern of a conventionally used magnetoresistive element. In order to construct a practical magnetoresistive element using currently known materials with magnetoresistive effect, it is necessary to have a considerable length of magnetoresistive value. For this reason, it is common to construct the magnetoresistive element in a 99-fold configuration as shown in FIG. The width A (Fig. 3) of one magnetoresistive element is around 0.1 mm with current element processing technology, but since it has a 99-fold structure, the width a of the magnetoresistive element is 0.5 to 1 mm. It becomes something of a degree. Therefore, the width of the magnetic material of the signal source also needs to be about 0.5 mm or more, and the pitch thereof is also about 1 mm.

The present invention was devised to solve this problem. An example is shown in FIG.

FIG. 4a shows a signal source in which ink containing a magnetic substance is provided with regulating grids at intervals of d using a magnetic thin film or the like. For this purpose, a magnetic sensor having a magnetoresistive element as shown in FIG. 4b is prepared instead of the one shown in FIG. 3. In each of the magnetoresistive elements 1 and 2 of this sensor, the interval between the ninety-nine fold structures of the magnetoresistive body is made to match the pitch d of the signal source. Furthermore, each magnetoresistive element has an interval of (n+1/2)d (n: an integer) between adjacent magnetoresistive elements.
Arrange it so that When this magnetic sensor scans the magnetic pattern shown in Figure 4a, when magnetoresistive element 1 exactly overlaps the magnetic pattern (at this time, the change in magnetic flux across the magnetoresistive element is maximum), the part 2 is the magnetic pattern of the signal source. The magnetic flux change across MR ₂ is minimal. In this way, a magnetic signal pattern finer than the width of the magnetoresistive element can be read. The output change of the magnetic sensor increases as the area where the magnetoresistive part of the magnetoresistive element overlaps with the magnetic material of the signal increases. According to the magnetic sensor having the structure of the present invention, by increasing the number of folds of the magnetoresistive element, the output can be increased without sacrificing the resolution of the sensor.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1A shows the configuration of a differential magnetic sensor using a magnetoresistive element, and FIG. 1B shows the circuit configuration. FIG. 2 shows the output waveform of the magnetic sensor of FIG. 1. FIG. 3 shows an example of a pattern of a magnetoresistive element of a conventional magnetic sensor. FIG. 4 shows an embodiment of the magnetoresistive element of the magnetic sensor according to the present invention, in which figure a is a pattern diagram of a magnetic signal source, and figure b is a pattern diagram of the magnetoresistive element of the present invention. 1, 2... Magnetoresistive element.

Claims (1)

[Scope of utility model registration request] Two magnetoresistive elements are spaced apart from each other by d, or
It has a magnetic resistance pattern of ninety-nine folds,
A differential magnetic sensor characterized by arranging two magnetoresistive elements so that adjacent magnetoresistive parts are spaced at a distance of (n+1/2)d, and reading a magnetic signal with a pitch of d.