JPH05264326A - Linear position sensor - Google Patents

Abstract

PURPOSE:To provide a linear position sensor which can inexpensively obtain highly reliable position information in the form of analog signals for a long period for detecting positions on a limited straight line. CONSTITUTION:The title position sensor which detects a prescribed position on a limited straight line is constituted so that the sensor can be provided at least with a sensor main body 13 constituted by sticking a magnetic plate 12, the width of which against the length direction of a rectangular permanent magnet 11 fully magnetized in its thickness direction differs depending upon the position of the plate 12 in its length direction, to one surface of the permanent magnet 11 and magnetic converting element 15 which can move above the magnetic plate 12 of the sensor main body 13 in the length direction of the plate 12, with a fixed clearance being maintained between the element 13 and plate 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear type position sensor for accurately detecting a position within a limited linear region such as a liquid level detecting device, and is particularly inexpensive and highly reliable for a long period of time. The present invention relates to a linear type position sensor in which position information can be obtained as an analog signal.

[0002]

2. Description of the Related Art For example, a resistance sliding type, a linear optical encoder type, and a linear magnetic encoder type have been put into practical use as conventional linear position sensors.

The principle of each of these types will be briefly described below. This internal resistance sliding type is
It is composed of a resistance wire wound in a straight line and a slider that moves while making contact with the resistance wire, and the resistance value changes when the slider is moved. The position of the child is detected.

Therefore, although the structure is simple, there is an advantage that a device having a high detection accuracy can be formed at a low price, but since the slider and the resistance wire slide, it is necessary to improve the abrasion resistance of both. ..

Further, the linear type optical encoder has, for example, a straight plate in which slits having different widths are formed in parallel with each other at a minute interval, and the straight plate can be moved in the longitudinal direction with respect to the straight plate. It is composed of a moving element in which a light receiving element and a light emitting element are arranged on both sides sandwiching in the thickness direction, and when the moving element is moved, the amount of light between the light receiving and emitting elements and thus the current value The position of the mover with respect to the straight plate is detected from the change.

Therefore, since the straight plate and the mover are not in contact with each other, there is a merit that the durability is rich, but there is a demerit that a fine slit is required to increase the detection accuracy and the cost becomes high.

Further, the linear type magnetic encoder is, for example, N
It is composed of a straight plate in which poles and S poles are alternately formed, and a magnetic sensor that moves on the straight plate along its longitudinal direction. When the magnetic sensor is moved, The position of the magnetic sensor with respect to the straight plate is detected based on the change in the output voltage.

Therefore, the linear plate and the magnetic sensor are not in contact with each other like the linear type optical encoder, so that the durability is excellent. However, in order to improve the detection accuracy, the cost is high like the linear type optical encoder. There is.

[0009]

However, in the resistance sliding type, since the contacts slide on the surface of the resistor, the wear of the contacts limits the durability as a sensor and the positional information during use varies. There is a problem that it is easy to occur,
In addition, the linear type optical encoder has low reliability against dust and dirt, and since it is basically a digital output, it is necessary to form fine and many slits in order to make it a linear analog signal. There is a problem in that it is inevitably expensive because it requires a large number of bits to detect, and the linear magnetic encoder has high reliability against dust and dirt, but the linear optical encoder described above. There was a problem that it had to be expensive as well.

Recently, in addition to these, a linear type position sensor utilizing a magnetic leakage magnetic field (Japanese Patent Laid-Open No. 62-1680).
04 "Potentiometer") is disclosed, but there is a problem that there is a difficulty in controlling the leakage magnetic field.

[0011]

The above-mentioned problem is a linear type position sensor for detecting a required position on a limited straight line, and is a strip-shaped permanent magnet which is fully magnetized with the thickness direction as the magnetizing direction. A sensor body having a magnetic plate attached to one side of the magnetic plate, the width of which is different depending on the position in the length direction, and the magnetic plate of the sensor body can move along the longitudinal direction with a constant gap. And a magnetic conversion element.

[0012]

When a magnetic plate having a width different depending on the position in the length direction is attached to the surface of a strip-shaped permanent magnet having a magnetizing direction in the thickness direction, a constant magnetic field emitted from the magnet is generated by the magnetic plates having different widths. Since it is bypassed and shielded, the magnetic field strength on the surface of the magnetic plate can be changed by the position of the magnet in the longitudinal direction.

On the contrary, this means that the position of the magnet in the longitudinal direction can be detected by detecting the magnetic field strength on the surface of the magnetic plate. On the other hand, it is known that a magnetic conversion element such as a Hall element or a magnetoresistive effect element outputs an output proportional to an applied magnetic field.

Therefore, in the present invention, as described above, a sensor main body in which a magnetic plate having a width different depending on the position in the length direction is attached to the surface of a strip-shaped permanent magnet that is fully magnetized with the thickness direction as the magnetizing direction. A linear position sensor is constituted by a magnetic conversion element that can move on the magnetic plate along the longitudinal direction.

In this case, the position of the magnetic conversion element with respect to the magnet can be detected by detecting the output from the moving magnetic conversion element. Therefore, it is possible to realize an inexpensive linear type position sensor that can detect an accurate position for a long period of time only with a normal member without using a special member.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram for explaining the construction principle of a linear type position sensor according to the present invention, and FIG. 2 is a diagram showing the magnetic field strength received by the sensor of FIG.

FIG. 3 is a diagram for explaining the construction principle of another linear type position sensor, and FIG. 4 is a diagram showing the magnetic field strength received by the sensor of FIG. Further, FIG. 5 is a diagram showing a configuration example as a linear position sensor, and FIG. 6 is a diagram explaining a usage example.

In FIG. 1, a linear position sensor (hereinafter simply referred to as a sensor) 1 is a strip-shaped permanent magnet (hereinafter simply referred to as a magnet) 11 which is fully magnetized with a thickness direction a as a magnetizing direction and its length. The magnetic plate 1 is made of permalloy having an isosceles triangular shape whose width is different depending on the position in the vertical direction as shown in the figure.
2 and a sensor assembly 14 connected to a control unit (not shown) by a signal line 14a are main components.

The magnet 11 and the magnetic plate 12 are constructed as a sensor body 13 in a state where their longitudinal directions are aligned and attached, and in the sensor body 13, a part of a constant magnetic field by the magnet 11 is generated. Bypassing to the attached magnetic plate 12, the magnetic field leaking above the magnetic plate 12 changes according to the width of the magnetic plate 12 as shown by Mf ₁ , Mf ₂ , Mf ₃ , Mf ₄ , and Mf _5. To do.

Therefore, the strength of the magnetic field emitted from the sensor main body 13 can be stably changed for each position in the longitudinal direction. Although the same effect as that of the sensor main body 13 can be obtained by changing the magnetization amount of the magnet itself depending on the position in the longitudinal direction, in general, when the magnet is not fully magnetized, it becomes magnetically unstable. It is not preferable because the amount of magnetization easily changes due to a magnetic field from the outside.Therefore, as described above, the magnetic plate 12 having a different width depending on the position is attached to the surface of the fully magnetized magnet to change the strength of the magnetic field. ing.

On the other hand, the sensor assembly 14 is an extracted view.
As shown in (a), for example, the Hall element 15 and the amplifier 16 are internally provided, and the voltage signal output from the Hall element 15 is proportional to the strength of the external magnetic field.
The signal is amplified by 16 and delivered from the signal line 14a to a control unit (not shown).

Therefore, the controller calculates the strength of the magnetic field received by the sensor assembly 14 when the sensor assembly 14 is moved in the longitudinal direction at a position close to the surface of the sensor body 13. Thus, the position of the sensor assembly 14 with respect to the sensor body 13 can be accurately detected.

In FIG. 2, the horizontal axis X represents the length of the magnet 11 as S, and the vertical axis Y represents the magnetic field strength M received by the sensor assembly 14.
It is an F. In this case, the magnetic plate described in FIG.
If the shape of 12 is appropriately determined, the length range of the magnet 11 (shown in the figure)
Since s ₁ ~s ₂ between) at can be varied linearly as the magnetic field changes line C ₁ of the illustrated points on the magnetic field variation line C ₁ in inverse C ₁
By setting p in advance, the magnet 11 corresponding to the point C ₁ p
The upper position s ₁ p can be detected.

In FIG. 3 for explaining the other structural principle of the sensor, the sensor 2 is fully magnetized with the magnet 21a being fully magnetized in the thickness direction a and the magnet 21b being fully magnetized in the thickness direction b. A magnet 21b that is integrated with an insulating layer 21c, and a magnet body 21a, 21b having different widths depending on their longitudinal positions, for example, a diamond-shaped permalloy as shown in the drawing. The magnetic plate 22 and the sensor assembly 14 described with reference to FIG. 1 are main components.

The magnet body 21 and the magnetic plate 22 are attached to each other with their longitudinal directions aligned and attached.
However, in the sensor body 23, the magnet body 21
Since a part of the constant magnetic field due to the magnetic field is bypassed to the attached magnetic plate 22, the magnetic field leaking above the magnetic plate 22 changes depending on the width or position of the magnetic plate 22 as in FIG. In this case, the magnets 21a and 21b are magnetized in opposite directions, so that the magnetic fields of the areas A and B of the magnetic plate 22 are opposite to each other.

Therefore, as in the case of FIG. 1, when the sensor assembly 14 is moved on the magnetic plate 22 and the strength of the magnetic field received by the sensor assembly 14 is calculated by the control section, as shown in FIG. Similarly, as shown by a magnetic field change line C _{2 in} FIG. 4, where the horizontal axis X is the length of the magnet body 21 and the vertical axis Y is the magnetic field strength MF received by the sensor assembly 14, as shown in FIG. In the range (between s _{1 and} s _{2 in the} figure), when the magnetic field strength is zero, that is, when the sensor assembly 14 is located on the insulating layer 21c of the magnet body 21, the position with the reference origin C ₂ P can be detected. it can.

In FIG. 5 showing a configuration example as a sensor, (5-
1) shows the whole structure, and (5-2) shows (5, 1) with arrow c ~.
It is sectional drawing when it cut | disconnects by c '. In addition, in the figure, the case where the configuration is the same as that of the sensor 1 in FIG.
The same components as those in FIG. 1 are represented by the same symbols.

In FIG. 5, the sensor 3 is roughly divided into a shaft 31 made of an insulating material and a guide groove 31a provided in the shaft 31 along the length thereof so that the sensor 3 is fitted in the longitudinal direction with respect to the shaft 31. And a slider 32 made of an insulating material that can smoothly slide.

The shaft 31 has a flat surface 31b formed on a part of its surface along the longitudinal direction so that the magnetic plate 12 of the sensor body 13 described with reference to FIG. The sensor assembly 14 described with reference to FIG. 1 is mounted on the slider 32 in a position parallel to the sensor body 13 so that the Hall element 15 faces the sensor body 13. ..

Therefore, by sliding the slider 32 in the longitudinal direction with respect to the shaft 31, that is, in the direction of the arrow D in the figure, the sensor assembly 14 is moved with respect to the sensor body 13, and as a result, As described in FIG. 1, the position of the sensor assembly 14 with respect to the sensor body 13 can be accurately detected by the magnetic field strength sensed by the Hall element 15 of the sensor assembly 14.

If the sensor body 13 mounted on the sensor 3 is mounted in place of the sensor body 23 described with reference to FIG. 3, it is possible to construct a sensor capable of detecting positional deviation in both directions when the center is the reference point. Is as described in FIG.

FIG. 6 shows an example in which the sensor 3 described in FIG. 5 is used as a liquid level inspection device. That is, for example, the sensor 3 described with reference to FIG. 5 is vertically mounted and fixed to one wall surface of the liquid storage tank 35 surrounded by the opaque wall surface 35a.

A float 33 is attached and fixed to the slider 32 of the sensor 3. The curled signal line 14a connected to the sensor assembly 14 of the slider 32
Is led to the outside of the liquid storage tank 35 from a sealing flange 35b provided on the wall surface and then connected to a control unit (not shown).

In this case, the float 33 and thus the slider 32 move up and down with respect to the shaft 31 as the liquid level in the liquid storage tank 35 moves up and down.
The position of the slider 32, that is, the liquid surface can be detected by calculating the magnetic field strength sensed by.

[0035]

As described above, according to the present invention, it is possible to provide an inexpensive linear type position sensor which can obtain highly reliable position information as an analog signal over a long period of time.

In the description of the present invention, the case where the Hall element is used for the sensor assembly is taken as an example, but the same effect can be obtained by using the magnetoresistive effect element instead of the Hall element.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration principle of a linear position sensor according to the present invention.

FIG. 2 is a diagram showing the magnetic field strength received by the sensor of FIG.

FIG. 3 is a diagram illustrating a configuration principle of another linear position sensor.

FIG. 4 is a diagram showing magnetic field strength received by the sensor of FIG.

FIG. 5 is a diagram showing a configuration example as a linear position sensor.

FIG. 6 is a diagram illustrating a usage example.

[Explanation of symbols]

1,2,3 Linear position sensor 11,21,21a, 21b Strip-shaped permanent magnet 12,22 Magnetic plate 13,23 Sensor body 14 Sensor assembly 14a Signal line 15 Hall element (magnetic conversion element) 16 Amplifier 31 Axis 31a Guide groove 31b Flat surface 32 Slider 33 Float 35 Liquid storage tank 35a Opaque wall surface 35b Sealing flange

Front page continued (72) Inventor Michiko Endo 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa 1015, Fujitsu Limited

Claims (4)

[Claims] 1. A linear type position sensor for detecting a required position on a limited straight line, wherein one side of a strip-shaped permanent magnet (11) is fully magnetized with the thickness direction as a magnetizing direction. A sensor main body (13) having a magnetic plate (12) having a width different from the lengthwise direction depending on the position in the lengthwise direction, and the magnetic plate (12) of the sensor main body (13) are longitudinally maintained with a constant gap. A linear position sensor characterized by comprising at least a magnetic conversion element (15) capable of moving along a direction. 2. The strip-shaped permanent magnet according to claim 1, which has magnetizing directions opposite to each other with a longitudinal center line as a boundary.
The strip-shaped permanent magnets (21a, 21b) are formed by individual strip-shaped permanent magnets (21a, 21b).
The linear position sensor is characterized in that the width in the length direction within the length range is different depending on the position in the length direction. 3. A linear type position sensor, wherein the magnetic plate according to claim 1 is formed of a permalloy material. 4. A linear type position sensor, wherein the magnetic conversion element according to claim 1 is a Hall element or a magnetoresistive effect element.