JPH08201007A - Position detection device and magnetoresistive effect element - Google Patents

Abstract

(57) [Summary] [Object] To provide a position detection device and a magnetoresistive effect element capable of obtaining highly accurate position information. According to the magnetoresistive effect element of the present invention, at least two magnetic detectors M1 and M2 whose resistance value changes in response to a magnetic field of a scale portion 7 having magnetic poles alternately magnetized at predetermined intervals are arranged. These magnetic detectors are connected in series, a voltage is applied to both ends of the magnetic detector, and an output is obtained from a midpoint. Further, external connection terminals 401 and 501 required for voltage application or signal output are provided. , 601
The width of the scale portion in the direction parallel to the magnetic field is 2 m times the magnetic pole formation width P of the scale portion (m = 1, 2 ,.
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Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device for detecting the position of an object, and more particularly to detecting the position of an object with high accuracy and high resolution by using a magnetoresistive effect element (MR element). The present invention relates to a position detection device.

[0002]

2. Description of the Related Art For example, a lens system having a zoom mechanism and a focus mechanism in a video camera is one of those requiring high-resolution position detection. In such a lens system, the subject distance at the focal point, the zoom lens position, and the focus lens position must have a predetermined positional relationship determined by the lens design. In order to satisfy this positional relationship, conventionally, a method of using a mechanical cam or a method of detecting the zoom lens position and the focus lens position and forming an electronic cam by calculation is used.

The method using a mechanical cam has problems such as a large device structure and a decrease in accuracy due to mechanical abrasion.

As a method using an electronic cam, there are a method using a potentiometer as a position detector, a method using a stepping motor as a lens driving motor, and a method for counting control signals of the stepping motor. However, the method using the potentiometer has problems that the load applied to the motor is increased because of the contact type, the linearity is deteriorated due to the dispersion of the resistance film, the reliability is low, and the like.
On the other hand, the method of counting the control signals of the stepping motor can be applied only to the lens system using the stepping motor as the motor. Further, if there is an object, such as a gear, interposed between the motor and the lens, an error occurs due to the play (play).

As a method for solving the above problems, it is possible to use an MR element. That is, the characteristic that the resistance value of the MR element changes according to the change of the magnetic field is used. For example, there is a method in which a magnet is mounted on the lens side, an MR element is arranged on the fixed side, the magnet is moved with respect to the MR element by moving the lens, and the resistance change is extracted as a position change.

FIG. 4 shows a pattern diagram of a conventional MR element. The MR element is composed of two magnetic detectors M1 and M2. These magnetic detectors M1 and M2 are ferromagnetic thin films, for example, a thin nickel-iron alloy film is formed on a glass substrate by vacuum vapor deposition or sputtering in a magnetic field, and two thin lines are folded back by etching or the like. Form a line. The folded portion 1 has a large line width in order to reduce the resistance value. In the magnetic detectors M1 and M2, the resistance value is changed by the magnetic field of the magnet (scale part) 7,
It is formed long in the direction orthogonal to the direction of the magnetic field of the magnet 7. Between the magnetic detectors M1 and M2 or the magnetic detectors M1,
The connection line 2 or the wiring portion 3 for connecting M2 and an external connection terminal described later is formed of the same ferromagnetic thin film as the magnetic detectors M1 and M2. The connection line 2 is formed in a direction in which resistance change does not occur due to the magnetic field of the magnet 7, that is, in a direction parallel to the direction of the magnetic field of the magnet 7. In order to reduce the resistance value, the line widths of the connection line 2 and the wiring portion 3 are formed thick. 4 and 6 are external connection terminals for applying power to the MR element,
Reference numeral 5 is an external connection terminal for extracting the output signal of the MR element. The external connection terminals 4, 5, 6 are connected to the magnetic detector M1,
It is formed of the same ferromagnetic thin film as M2. The magnet 7 has N magnetic poles and S magnetic poles alternately formed at a certain predetermined interval P.

FIG. 5 shows an equivalent circuit diagram of the MR element. FIG. 6 shows the relationship between the magnetic detectors of the MR element and the magnetic poles in the magnet, and the output signal waveform of the MR element. The magnetic detectors M1 and M2 are formed with a phase shift of substantially P / 2 in order to make the output signal sinusoidal.

Position information can be obtained by waveform-shaping the output signal of the MR element thus constructed into a pulse signal and measuring the edge thereof, and further, interpolating the output signal in an analog manner. Thus, position information with higher resolution can be obtained.

[0009]

However, in the above-mentioned conventional example, the resistance value change due to the magnetic field occurs not only in the magnetic detectors M1 and M2 but also in the external connection terminals 4, 5 and 6 or the wiring portion 3. I will end up.

Further, in the MR element, the MR element is generally
There is a characteristic that the hysteresis of the resistance value change is different when the magnetic field applied to the element is increased and when it is decreased. Figure 7
An example of a change in resistance value of the MR element when a magnetic field is applied in a direction orthogonal to the MR element is shown in FIG. In FIG. 7, the solid line is a curve showing the resistance value change when the magnetic field is decreased, and the broken line is the curve showing the resistance value change when the magnetic field is increased. The external connection terminals 4, 5, 6 or the wiring portion 3 are formed without considering the characteristics having such hysteresis. Therefore, in the conventional MR element, an error occurs when the position is measured with higher accuracy.

In order to solve the above problems, it is an object of the present invention to provide a position detecting device and a magnetoresistive effect element which can obtain highly accurate position information.

[0012]

In order to solve the above-mentioned conventional problems and to achieve the above-mentioned objects, a magnetoresistive effect element according to the present invention has a magnetic field of a scale portion having magnetic poles alternately magnetized at predetermined intervals. At least two magnetic detectors whose resistance values change in response to the magnetic detectors are connected in series, and a voltage is applied across the magnetic detectors to obtain an output from the midpoint. , The width of the external connection terminal required for voltage application or signal output in the direction parallel to the magnetic field in the scale portion is 2 m times the magnetic pole formation width P of the scale portion (m = 1, 2, ...) Is formed in.

As another structure of the magnetoresistive effect element, at least two magnetic detectors whose resistance value changes in response to the magnetic field of the scale portion having magnetic poles alternately magnetized at predetermined intervals are arranged. , These magnetic detectors are connected in series, a voltage is applied to both ends of the magnetic detector, and an output is obtained from a midpoint, and further, the magnetic field of the wiring part in the direction orthogonal to the direction of the magnetic field in the scale part. The width in the direction parallel to is 2n times (n = 1, 2, ...) The magnetic pole formation width P of the scale portion.

Further, it is desirable that the magnetic detector, the external connection terminal and the wiring portion are formed of a ferromagnetic thin film.

Further, a highly accurate position detecting device can be provided by having the scale section described above and the sensor section composed of the magnetoresistive effect element described above.

[0016]

Embodiments will be described in detail below with reference to embodiments of the present invention. It should be noted that components having the same configurations or functions as those of the conventional technique are designated by the same reference numerals and described.

[First Embodiment] FIG. 1 shows a pattern diagram of forming an MR element as a sensor portion according to a first embodiment of the present invention. The MR element has two magnetic detectors M1 and M2.
Is configured. The magnetic detectors M1 and M2 are formed by vacuum deposition or sputtering in a magnetic field on a glass substrate (not shown) to form a ferromagnetic thin film having a thickness of about 500 to 1000 Å, for example, a nickel-iron alloy film, and etching. A thin line having a line width of about 10 μm is folded back to form two lines. The folded portion 1 is formed to have a wide line width of about 100 μm in order to reduce the resistance value. The magnetic detectors M1 and M2 are formed long in a direction orthogonal to the direction of the magnetic field of the scale part 7 so that the resistance value is changed by the magnetic field of the scale part (magnet) 7.

On the other hand, the connecting wire 2 or the wiring portion 3 for connecting between the magnetic detectors M1 and M2 or between the magnetic detectors M1 and M2 and an external connection terminal described later is the magnetic detector M.
It is formed of the same ferromagnetic thin film as 1 and M2. Connection line 2
Are formed in a direction in which resistance change does not occur by the magnetic field of the scale portion 7, that is, in a direction parallel to the magnetic field direction of the scale portion 7. Further, in order to reduce the resistance value, the line width of the connection line 2 and the wiring portion 3 is wide, and is about 100 μm. 401 and 601 are external connection terminals for applying power to the MR element, and 501 is an external connection terminal for taking out an output signal of the MR element. External connection terminals 401, 501, 6
01 is formed of the same ferromagnetic thin film as that of the magnetic detection unit. The line width d of these external connection terminals 401, 501, 601 is 2 m times the magnetic pole formation width P of the scale portion 7 (however,
m = 1, 2, ...). In this embodiment, it is formed with m = 1. In the scale portion 7, N magnetic poles and S magnetic poles are alternately formed at a certain predetermined interval P.

FIG. 2 is a diagram showing changes in resistance value when a magnetic field is applied to the MR element using a scale having a magnetic pole formation width P and magnetic poles formed therein. The solid line and the broken line have different waveforms because the hysteresis of the resistance value change history is different when the magnetic field applied to the MR element is increased and when it is decreased.

However, as described above, the line width d of the external connection terminal is 2 m times the magnetic pole formation width P of the scale portion 7 (m =
1, 2, ...)
The resistance values of 1,501,601 are constant resistance values obtained by averaging the resistance values in the section d. Therefore, the error component of the position information due to the resistance change of the external connection terminal can be reduced,
More accurate position information can be obtained.

[Second Embodiment] Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 shows M of the second embodiment.
The formation pattern figure of R element is shown. In FIG.
Description of the same components as those in FIG. 1 will be omitted.

In FIG. 3, reference numeral 301 denotes a wiring portion formed in a direction orthogonal to the direction of the magnetic field of the scale portion 7. The wiring portion 301 is formed of the same ferromagnetic thin film as the magnetic detectors M1 and M2, and its line width is 2n times the magnetic pole formation width P of the scale portion 7 (where n = 1, 2, ...). Is formed by. In the present embodiment, n = 1. 401 and 601 are external connection terminals for applying power to the MR element, and 501 is an external connection terminal for taking out an output signal of the MR element. External connection terminals 401, 50
Reference numerals 1 and 601 are formed of the same ferromagnetic thin film as that of the magnetic detection unit. The width d of these external connection terminals in the direction parallel to the magnetic field generated by the scale portion 7 is the magnetic pole formation width P of the scale portion 7.
2m times (m = 1, 2, ...) In this embodiment, it is formed with m = 1.

In the second embodiment, even in the wiring portion 301, the resistance change due to the magnetic field of the scale portion 7 does not occur and the resistance value becomes a constant value. Therefore, the error component of the position information due to the resistance change of the external connection terminal and the wiring portion can be reduced, and more accurate position information can be obtained.

[0024]

As described above, according to the present invention, the error component of the position information due to the magnetoresistive effect of the external connection terminal or the wiring portion can be removed, and the highly accurate position information can be obtained.

[Brief description of drawings]

FIG. 1 is a formation pattern diagram of an MR element according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a change in resistance value when a magnetic field is applied to an MR element using a scale having a magnetic pole formation width P and magnetic poles formed therein.

FIG. 3 is a formation pattern diagram of an MR element according to a second embodiment of the present invention.

FIG. 4 is a pattern diagram of a conventional MR element.

FIG. 5 is an equivalent circuit diagram of a conventional MR element.

FIG. 6 is a diagram showing a relationship between each magnetic detector of the MR element and a magnetic pole in the magnet, and an output signal waveform of the MR element.

FIG. 7 is a diagram showing an example of a change in resistance value of an MR element when a magnetic field is applied in a direction orthogonal to the MR element.

[Explanation of symbols]

 2 connection wire 3 wiring part 7 scale part (magnet) 301 wiring part 401 external connection terminal 501 external connection terminal 601 external connection terminal M1 magnetic detector M2 magnetic detector

Claims (8)

[Claims] 1. A scale part having magnetic poles alternately magnetized at predetermined intervals, and at least two magnetic detectors whose resistance changes in response to a magnetic field of the scale part are arranged. Is connected in series, and a sensor unit configured to apply a voltage to both ends thereof and obtain an output from a midpoint, wherein the sensor unit is for applying a voltage or outputting a signal. The width of the external connection terminal required in the direction parallel to the magnetic field in the scale portion is 2 m times (m = 1, 2, ...) The magnetic pole formation width P of the scale portion. Position detection device. 2. The position detecting device according to claim 1, wherein the magnetic detector and the external connection terminal are formed of a ferromagnetic thin film. 3. A scale part having magnetic poles alternately magnetized at predetermined intervals, and at least two magnetic detectors whose resistance changes in response to a magnetic field of the scale part are arranged. Are connected in series, a voltage is applied to both ends thereof, and a position detection device having a sensor unit configured to obtain an output from a midpoint, wherein the sensor unit is a magnetic field direction in the scale unit. The width of the wiring part in the direction parallel to the magnetic field in the direction orthogonal to
2n times the magnetic pole formation width P of the scale portion (n = 1, 2,
...) is formed in the magnetoresistive effect element type position detecting device. 4. The position detecting device according to claim 3, wherein the magnetic detector and the wiring portion are formed of a ferromagnetic thin film. 5. At least two magnetic detectors whose resistance values change in response to a magnetic field of a scale portion having magnetic poles alternately magnetized at predetermined intervals are arranged, and these magnetic detectors are connected in series. , A magnetoresistive effect element that is configured so that an output can be obtained from the midpoint by applying a voltage to both ends of the magnetoresistive effect element, and is parallel to the magnetic field in the scale part of the external connection terminal required for voltage application or signal output. 2m times the magnetic pole formation width P of the scale portion (m = 1, 2, ...
..) The magnetoresistive element. 6. The magnetoresistive effect element according to claim 5, wherein the magnetic detector and the external connection terminal are formed of a ferromagnetic thin film. 7. At least two magnetic detectors, whose resistance values change in response to a magnetic field of a scale portion having magnetic poles alternately magnetized at predetermined intervals, are arranged, and these magnetic detectors are connected in series. , A magnetoresistive effect element configured to apply a voltage to both ends thereof and obtain an output from a midpoint, the direction being parallel to the magnetic field of the wiring part in a direction orthogonal to the direction of the magnetic field in the scale part. Is formed to be 2n times (n = 1, 2, ...) The magnetic pole formation width P of the scale portion. 8. The magnetoresistive effect element according to claim 7, wherein the magnetic detector and the wiring portion are formed of a ferromagnetic thin film.