JPS63212803A - Measuring device for displacement - Google Patents

Abstract

PURPOSE:To enable the attainment of an electric output proportional to displacement with high reliability, by making the field of a magnet distributed in a small width and by making a magnetoresistance element have a linear sensitivity distribution in relation to the direction of the displacement ranging from a small width to a large width. CONSTITUTION:A magnetic circuit comprising yokes 13-1 and 13-2 and a permanent magnet 12 is fitted to a moving body 11, and a magnetoresistance element 14 disposed opposite to said circuit with a gap between them is provided. Magnetoresistance bodies 15 having terminals 15 and arranged in a pattern shown in the figure are used as the element 14. The magnetoresistance bodies 15 are thin film conductors having a magnetoresistance effect respectively and have a sensitivity characteristic varying linearly in the direction of movement. The variation of the sensitivity of the magnetoresistance bodies 15 can be set arbitrarily by giving a linear variation to the length of the bodies 15. According to this construction, the magnet 12 moves as the movement of the body 11, a variation of magnetoresistance proportional to the movement of the magnet is obtained in the element 14, and thus the measurement of the displacement can be implemented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a displacement measurement device that converts displacement into an electrical signal, and in particular, a displacement measurement device that can obtain an output signal proportional to the amount of displacement and that is highly reliable. It is related to the device.

[Conventional technology]

Devices for measuring displacement (position) are widely used in the industrial field as sensors for measuring displacement, vibration, width, thickness, unevenness, etc., as well as feedback for positioning control.

A "potentiometer" is a device that applies the principle of a variable resistor to obtain an electrical signal that changes linearly with displacement.
are often used, but while they are inexpensive, they have problems such as short lifespans and noise generation because they have contact parts, and are not suitable for applications that require frequent movement or applications that require reliability. Differential transformers are used in fields where reliability is required, but because they require windings and precise magnetic circuits, they are expensive and bulky.

Sensors that combine a permanent magnet and a magnetically sensitive element are also widely used because they are small, lightweight, inexpensive, and highly reliable; however, they cannot obtain a signal that changes linearly with displacement. However, its use was limited to on/off control, etc.

The present invention has been made in consideration of the above points, and an object of the present invention is to provide a displacement measuring device that can obtain an output signal proportional to the amount of displacement.

[Means for solving problems]

A displacement measuring device according to the present invention is a displacement measuring device in which a permanent magnet or a magnetic circuit including the same and a magnetoresistive element are movably arranged opposite to each other with an air gap between the permanent magnet or the magnetic circuit including the permanent magnet. The component of the magnetic field generated by the magnetoresistive element that is sensitive to the magnetoresistive element is distributed with a narrow width in the direction of movement, and the magnetoresistive element has a linear sensitivity distribution in the direction of movement with a width wider than the above width in the direction of movement. It was arranged as follows.

[Effect]

In this invention, an electric signal that changes linearly with displacement can be obtained from the magnetoresistive element.

(Example) Before explaining the present invention in detail, the measurement principle of the present invention will be explained with reference to FIG.

FIG. 8(a) shows the relative relationship between the permanent magnet 1 and the magnetic resistor 2, and FIG. 8(b) is a diagram showing the resistance change of the magnetic resistor in FIG. 8(a). As shown in FIG. 8(a), the coordinate X is taken in the moving direction, and the resistance change of the magnetoresistive element 2 having unit sensitivity placed at the position x, ) is assumed to be γ. In this invention, since the magnetic field component sensitive to the magnetoresistive element 2 has a narrow width d in the moving direction, the resistance change γ also
As shown in Figure (b), it takes a large value only within a certain width, and becomes almost 0 outside of this range.

In this invention, a magnetoresistive element (same as magnetoresistive element 2 in this figure) having a linear sensitivity distribution with respect to the moving direction X is used. Therefore, the sensitivity S at the position X is expressed by the general formula 3, where χ is the displacement. The resistance change dr of the entire magnetoresistive element 2 is given by integrating the product of the resistance change γ and the sensitivity S over the entire length of the magnetoresistive element 2, and the linearity of sensitivity is satisfied at least in the section where γ is not 0. Then, the integral over the entire length is equivalent to the infinite interval integral, and is calculated by the following formula.

=α·I8·χ+α·I2·β·11 Since both are constants, a proportional relationship holds between the displacement χ and the resistance change dr.

Note that sensitivity is better when β is 0.

Next, embodiments of the invention will be described.

FIG. 1 shows an embodiment of the present invention, in which a permanent magnet 12 attached to a moving object 11 and a yoke 13-1.
It consists of a magnetic circuit 13-2 and a magnetoresistive element 14 placed opposite to the magnetic circuit 13-2 with an air gap in between. In addition, permanent magnet 1
2 may be sufficient, but a magnetic circuit including a permanent magnet 12 as shown in the figure may be used. As the magnetoresistive element 14, as shown in FIG.
) or the magnetic resistor 15 having the pattern arrangement shown in FIG. 3(a) is used. 16 is a terminal of the magnetic resistor 15.

The magnetoresistive elements 15 in FIGS. 2(a) and 3(a) are thin film conductors having a magnetoresistive effect, and have sensitivity characteristics that vary linearly with respect to the direction of movement.

As shown in FIG. 2(a), the change in sensitivity is caused by the magnetic resistance element 15.
It can be set arbitrarily by linearly changing the length of , or by linearly changing the inclination of the magnetic resistor 15 as shown in FIG. 3(a). For example, the pattern shown in FIG. 3 is formed by bending a parabolic magnetic resistor 15, and each of the bent pieces forms a part of the parabola. Therefore, the change in slope is linear. Note that the pattern of the magnetoresistive element 15 is not limited to a parabola, but may have a shape approximating this. These sensitivity characteristics change linearly as shown in FIG. 2(b) and FIG. 3(b), respectively.

According to the above configuration, the permanent magnet 12 moves as the moving object 11 moves, and a resistance change proportional to this movement is obtained in the magnetoresistive element 14, so that displacement measurement can be performed.

Generally, the resistance of the magnetoresistive element 15 also changes depending on the temperature. To compensate for this, as shown in FIG. 4, two magnetoresistive elements 14A and 14B with the pattern shown in FIG. 2 are provided so that the resistance changes due to displacement are in opposite directions, and the resistor R
Preferably, one voltmeter V is used to construct the bridge.

Note that E is a battery and 16 is a terminal. In this way, resistance changes due to temperature cancel each other out, and resistance changes due to a magnetic field strengthen each other, so displacement can be measured without being affected by temperature changes.

FIG. 5(a) shows an example of bridge magnetoresistive elements 14A and 14B configured by changing the inclination of the magnetoresistive element 15,
This corresponds to the pattern shown in FIG. FIG. 5(b) shows the sensitivity characteristics. The dotted line shows the apparent sensitivity in the bridge configuration.

The change in resistance per displacement is proportional to the sensitivity gradient α in the movement direction, and the larger this value is, the less susceptible to the influence of noise, which is preferable. The sensitivity gradient α is the value obtained by dividing the width of change in sensitivity by the length, but in general, sensitivity cannot take a negative value, and there is an upper limit determined by the material and shape, so there is a certain limit to the width of change in sensitivity. There is. By the way, when a bridge configuration is adopted, the sensitivity of one magnetoresistive element 14A can be regarded as negative sensitivity for the other magnetoresistive element 14B. By utilizing this, the sensitivity change range can be doubled. When this is done, as shown in FIG. 5(b) above, by forming a pattern so that the sensitivity is O at the connection part, the linear range of the magnetoresistive element 14A is adjusted.

14B, and the apparent sensitivity can be expanded from the negative upper limit to the positive upper limit.

The displacement measuring device according to the present invention detects the movement of the magnetic field pattern in the magnetoresistive element 14 portion. The displacement of the permanent magnet 12 (FIG. 1), which is the object to be measured, and the movement of the magnetic field pattern can be the same, or they can be separated.

FIG. 6 schematically shows this, and shows the object to be measured, 8'! II When the object 11 moves in the Y direction, the magnetic field pattern moves in the X direction. By using this, it is possible to measure displacement of any size even with the same element by adjusting the angle (σ) between the magnetic field generating part and the moving direction. It is possible to measure large displacements.

FIG. 7 shows an example of a rotation angle measuring device constructed using the displacement measuring device according to the present invention, in which a rotor 17 having three magnetic poles and two sets of magnetic Resistance element 14A.

Consists of 14B. The rotor 17 is magnetized so that the magnetic pole boundary is located at the position expressed by the formula %. Here, Y is the position in the height direction, Y − and Y b are the center heights of the respective magnetoresistive elements 14A and 14B, A is a constant, and θ is the rotation angle. When power supplies with the same positive and negative voltages are connected to both ends of each of the magnetoresistive elements 14A and 14B, a voltage proportional to sin θ is obtained at one end, and a voltage proportional to COS θ at the other end is obtained at the midpoint. In addition, when the magnetoresistive element 14A is driven by an AC voltage proportional to +/-sinωt and the magnetoresistive element 14B is driven by an AC voltage proportional to ±sinωt, and the midpoint potential of the pixel element is added, the phase is shifted by θ with respect to the driving AC. By obtaining an AC signal and measuring the phase difference, it is possible to measure the rotation angle with high resolution.

[Effects of the Invention] As explained in detail above, the present invention is a displacement measuring device in which a permanent magnet or a magnetic circuit including the permanent magnet and a magnetoresistive element are arranged opposite to each other with a gap in between. ,
Of the magnetic field generated by a permanent magnet or a magnetic circuit including the permanent magnet, the component sensitive to the magnetoresistive element is distributed with a narrow width in the direction of displacement, and the magnetoresistive element has a linear distribution in the direction of displacement over a wider width than the narrow width. Since the configuration has a sensitivity distribution, it is possible to obtain an electrical output proportional to displacement and to construct a highly reliable displacement measuring device at low cost. In addition, linearity is determined by the accuracy of the sensitivity distribution, but since magnetoresistive elements are manufactured by photoetching, it is easy to adjust the sensitivity distribution to the target value, making it possible to obtain a high-precision measurement device at low cost. . In addition, by devising the configuration, it is also possible to measure large displacements and rotation angles.
It has excellent advantages that can be applied in a wide range of fields.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of the present invention, and FIG. 2 (
a) and (b) are diagrams showing the pattern arrangement of the magnetoresistive element used in the present invention and its sensitivity characteristics; Fig. 3 (a), (b)
4 is a diagram showing a pattern arrangement of a magnetoresistive element and its sensitivity characteristics, similarly showing another example, FIG. 4 is a diagram showing a circuit of an embodiment of the present invention, and FIGS. Figures 6 and 7 are schematic diagrams showing other embodiments of the invention, and Figure 8 is a diagram explaining the principle of the invention. FIG. 4 is a diagram showing the relationship between a magnet and a magnetoresistive body, as well as resistance change characteristics. In the figure, 11 is a moving object, 12 is a permanent magnet 13-1.13
-2 is a yoke, 14 is a magnetoresistive element, 15 is a magnetoresistive body, and 16 is a terminal. FOp 几Go j, H Figure 1 Figure 2 Figure 3 (b)
(b) - Displacement - Displacement Figure 4

Claims (3)

[Claims] (1) A displacement measuring device in which a permanent magnet or a magnetic circuit including the same and a magnetoresistive element are movably arranged opposite to each other with an air gap, the magnetic field generated by the permanent magnet or the magnetic circuit including the permanent magnet is Among them, a component sensitive to the magnetoresistive element is distributed with a narrow width in the direction of displacement, and the magnetoresistive element has a linear sensitivity distribution in the direction of displacement over a width wider than the narrow width. Displacement measuring device. (2) A magnetoresistive element is constructed by connecting a magnetoresistive element whose sensitivity increases linearly with respect to the direction of movement and a magnetoresistive element whose sensitivity linearly decreases with respect to the direction of movement, and applies different voltages to terminals at both ends. and obtains a voltage change proportional to the displacement at the connection part.
1) Displacement measuring device described in section 1). (3) A claim characterized by using a magnetoresistive element composed of two magnetoresistive bodies that have a symmetrical shape with respect to the connection point and have zero sensitivity at the connection point. The displacement measuring device according to item (2).