JP2000088506A - Magnetic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic sensor capable of detecting the position of a piston when a cylinder tube is made of magnetic material like iron, and further a magnetic sensor which eliminates influence of geomagnetism and enables high precise detection. SOLUTION: Two detection coils 61, 62 formed by winding coil 51, 52 around cores 41, 42 composed of high permeability soft magnetic material are arranged in the axial direction of a cylinder 1, shifting their positions. Exciting pulses are applied to one ends of the respective coils 61, 62. On the basis of difference of detected outputs obtained from the other ends, the position of a piston 2 in which a magnet 3 is assembled is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic sensor for detecting the position of an object to be detected in a container from outside the container, and more particularly to a magnetic sensor suitable for detecting the position of a piston in a cylinder.

[0002]

2. Description of the Related Art For example, in a manufacturing line in a factory, it is necessary to grasp whether or not a piston rod of a hydraulic or pneumatic hydraulic cylinder is operated to a proper position to normally process a workpiece or the like. A so-called cylinder switch is used in which a magnet is incorporated into a piston in a cylinder, and the arrival of the piston at a predetermined position from the outside of the cylinder is detected using a reed switch, a magnetoresistive element, a Hall element, or the like.

[0003]

In such a conventional cylinder switch, as described above, the magnetic flux of the magnet is detected outside the cylinder using a reed switch, a magnetoresistive element or a Hall element. However, these sensors have low sensitivity, and when the material of the cylinder tube is a magnetic material such as iron, the magnetic flux density leaking to the outside of the cylinder becomes small and cannot be detected. There is a drawback in that the use of stainless steel, aluminum, or the like has to be used, and the cost is high.

Therefore, a high-sensitivity magnetic sensor capable of detecting a slight magnetic flux density leaking to the outside of the cylinder is desired. Such a high-sensitivity magnetic sensor is affected by residual magnetism on the cylinder surface and terrestrial magnetism. There is a disadvantage.

The present invention has been made in view of the above technical problems, and provides a magnetic sensor capable of detecting the position of an object to be detected even when a container such as a cylinder is made of a magnetic material. It is an object of the present invention to provide a magnetic sensor capable of detecting with high accuracy by removing the influence of geomagnetism.

[0006]

In order to achieve the above-mentioned object, the present invention is configured as follows.

That is, the present invention according to claim 1 is a magnetic sensor for detecting a position of a detection target in which a magnet is incorporated in a container, wherein a coil made of a soft magnetic material having a high magnetic permeability is attached to a core material. Is disposed outside the container, the detection coil is excited, and the position of the detection target is detected based on the detection output.

In this case, the container may be any container that stores the object to be detected therein, regardless of whether it is closed or open.
Refers to various containers such as cylinders, tanks, and cases.

According to a second aspect of the present invention, in the configuration of the first aspect, the core material is detected by utilizing a change in magnetic permeability in a high magnetic permeability region of a magnetic saturation characteristic curve.

According to a third aspect of the present invention, in the configuration according to the first or second aspect, at least two detection coils are provided, and each of the detection coils is moved in a moving direction of the object to be detected moving in the container. While displacing the position,
The position of the object to be detected is detected based on a difference between the detection outputs of the detection coils.

According to a fourth aspect of the present invention, in the configuration of the third aspect, the object to be detected is detected based on a difference obtained by subtracting a detection output of the second detection coil from a detection output of the first detection coil. It is possible to switch between detecting the detected object and detecting the object based on a difference obtained by subtracting the detection output of the first detection coil from the detection output of the second detection coil.

According to a fifth aspect of the present invention, in the configuration according to the third aspect, a first detection coil for detecting a magnetic force of a magnet of the object to be detected at a predetermined position in the container, and at the predetermined position. A second detection coil that is disposed apart from the first detection coil so as not to be affected by a magnetic force of a magnet of the detection target and detects a residual magnetic force of the container.

According to a sixth aspect of the present invention, in the configuration according to any one of the third to fifth aspects, the container is a cylinder, the object to be detected is a piston, and one end of each of the detection coils. An excitation signal is given, and the position of the piston is detected based on a difference between detection outputs taken from the other ends.

(Operation) According to the first aspect of the present invention,
Since the detection coil formed by winding a coil around a core material made of a soft magnetic material having high magnetic permeability is excited and the position of the detection target in which the magnet is incorporated is detected based on the detection output, it is used as a material for the core material. By using a soft magnetic material having a higher magnetic permeability than the material of the cylinder tube, magnetic flux lines (magnetic flux) coming out of the container are collected and a large amount of magnetic flux is passed through the core material. Can be increased. Therefore, detection can be performed with higher sensitivity as compared with a conventional example using a reed switch, a magnetoresistive element, a Hall element, or the like.

According to the second aspect of the present invention, the change in the magnetic permeability in the high magnetic permeability region of the magnetic saturation characteristic curve of the core material is used, so that the inductance change of the coil of the detection coil is increased and the sensitivity is increased. Can be detected.

According to the third aspect of the present invention, at least two detection coils are provided, and each of the detection coils is disposed at a position shifted in the moving direction of the object to be detected, and based on a difference between the detection outputs. Since the position is detected, the position can be detected with high accuracy without being affected by geomagnetism having a wide magnetic flux distribution.

According to the fourth aspect of the present invention, the object to be detected is detected based on a difference obtained by subtracting the detection output of the second detection coil from the detection output of the first detection coil. Whether the object to be detected is detected based on a difference obtained by subtracting the detection output of the first detection coil from the detection output of the detection coil can be switched. Alternatively, when it is arranged on the rod end side, the object to be detected can be detected based on the difference which is less affected by the magnetic flux leaking from both ends of the cylinder.

According to the fifth aspect of the present invention, the first detection coil for detecting the magnetic force of the magnet of the object at the predetermined position and the influence of the magnetic force of the magnet of the object at the predetermined position are determined. And a second detection coil that is disposed apart from the first detection coil so as not to receive and detects the residual magnetic force, so that the two detection coils detect the magnetic force of the magnet together, Compared to the configuration in which the detection target is detected using the inclination of the peak or valley of the magnetic flux density distribution, for example, the detection target can be detected even when the thickness of the magnet is thin or the moving speed of the detection target is high. .

According to the sixth aspect of the present invention, the position of the piston in the cylinder can be detected with high accuracy without being affected by the residual magnetism or geomagnetism of the cylinder.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the magnetic sensor according to the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a schematic configuration diagram of a main part for detecting the position of a piston in a cylinder as a container using a magnetic sensor according to one embodiment of the present invention. .

The magnetic sensor A of this embodiment detects from outside the cylinder 1 that the piston 2 in the cylindrical cylinder 1 has reached a predetermined position. Has an annular magnet 3 incorporated therein. Here, the magnet 3 may have a rod shape, a spherical shape, a column shape, or a coil shape.

When a fluid such as pressurized oil or compressed air flows into or out of the ports 8 and 9, the piston 2 moves in the axial direction of the cylinder 1 (in the left-right direction in the figure). On the other end side of the workpiece 10, for example, processing is performed on the work.

The magnetic sensor A of this embodiment has a core 4 made of a soft magnetic material having a high magnetic permeability such as an amorphous alloy.
And a detection unit 6 in which the coil 5 is wound. A detection unit 7 in which the detection coil 6 is housed is disposed on the outer periphery of the cylinder 1.

In the magnetic sensor A, the change in the magnetic permeability in the high magnetic permeability region of the magnetic saturation characteristic curve of the core material 4 made of a soft magnetic material having a high magnetic permeability such as an amorphous alloy is used. The change in inductance of the coil 5 is increased so that detection can be performed with high sensitivity.

The shape of the core material 4 is not limited to a rod shape.
The core material 4 is not limited to an amorphous alloy, and other high-permeability soft magnetic materials such as permalloy, silicon steel, and iron-cobalt alloy may be used. Good.

FIG. 2 shows a magnetic sensor A according to the embodiment of FIG.
FIG. 3 is a block diagram showing the configuration of FIG. In the magnetic sensor A of this embodiment, a rectangular excitation pulse from the pulse oscillation circuit 12 is applied to one end of the detection coil 6 via the current limiting resistor R1 and the driver circuit 11, and the detection resistor R
When the detection output from the other end of the detection coil 6 grounded via the second circuit 2 is peak-held by the peak hold circuit 13 and the output is compared with a predetermined threshold by the comparator circuit 14 and exceeds the threshold, This provides an output indicating that the piston is at a predetermined position.

Next, the operation of the magnetic sensor A of this embodiment will be described with reference to the signal waveform diagrams of FIGS.

Here, FIG. 3 shows a case where an external magnetic field is not acting on the detecting coil 6, and FIG. 4 shows a case where an external magnetic field is acting on the detecting coil 6, respectively. Excitation pulse applied to one end of the detection coil 6, each figure (b) shows a detection current at the other end of the detection coil 6, each figure (c)
Indicates the output of the peak hold circuit 13.

A pulse oscillation circuit 1 is connected to one end of the detection coil 6.
When the pulse voltage shown in FIG. 2 to FIG. 3 (a) or FIG. 4 (a) is applied, the current is limited by the inductance of the coil 5 and the detection gradually increases as shown in FIG. 3 (b). If a current flows and this current does not exceed the saturation magnetic flux density (saturation limit) L1, the inductance of the coil does not change, and the output of the peak hold circuit 13 becomes a substantially constant value as shown in FIG. Become.

However, the piston 2 incorporating the magnet 3
When a magnetic field is applied from the outside close to the detection coil 6 and the amorphous alloy as the core material 4 constituting the detection coil 6 is magnetized in advance, the coil current exceeds the saturation magnetic flux density L2 at a smaller place, That is, the amorphous alloy is magnetically saturated, the inductance of the coil is reduced, and a large amount of current flows as shown in FIG. 4B, and the output of the peak hold circuit 13 is shown in FIG. As shown in FIG.

Therefore, by comparing the output of the peak hold circuit 13 with the threshold value corresponding to the predetermined position of the piston 2 to be detected by the comparator circuit 14, it can be determined that the piston 2 is at the predetermined position. .

More specifically, a threshold value is set in advance, the piston 2 is stopped at a predetermined position to be detected, and the detection coil 6 is moved along the axial direction of the cylinder 1 in that state, and the magnetic sensor A The detection coil 6 is installed at the outer peripheral position of the cylinder 1 where the output of (1) is obtained.

Thus, in FIG. 1 described above, a detection output is obtained from the magnetic sensor A when the piston 2 reaches a predetermined position from the left, for example.

As described above, the position of the piston 2 in which the magnet 3 is incorporated is excited based on the detection output by exciting the detection coil 6 formed by winding the coil 5 around the core material 4 made of a soft magnetic material having a high magnetic permeability. , It can be detected with higher sensitivity than the conventional example using a reed switch, a magnetoresistive element or a Hall element, etc., and the material of the cylinder tube must be made of stainless steel or aluminum as in the conventional example. Instead, it can be made of a magnetic material such as iron, so that the cost can be reduced. In particular, when applied to a large cylinder, the effect of cost reduction becomes remarkable.

(Embodiment 2) FIG. 5 is a schematic structural view corresponding to FIG. 1 of another embodiment of the present invention, and corresponding portions are denoted by the same reference numerals.

In the above embodiment, one detection coil 6 is provided, but in this embodiment, two detection coils having the same structure and size are provided, and each detection coil 6 ₁ ,
A 6 _second position, as shown in the plan view of FIG. 5 and 6, and staggered in the axial direction of the cylinder 1, as described later, the difference between the detection output of the detection coil 6 _and 62 The position of the piston 2 is detected based on this.

In this embodiment, the magnetic flux leaking to the surface of the cylinder 1 is about 1 gauss, and the magnitude of the detected magnetic flux density is, for example, 0.5 gauss. Moreover, these values depend on the strength of the magnet 3 and the cylinder 1
Have variations due to the magnetic properties of
There is also the influence of geomagnetism. Therefore, the first embodiment in which one detection coil 6 is used to detect the absolute value of the magnetic flux density
In the configuration described above, the detection position may be unstable.

Therefore, in this embodiment, as described above, two detection coils are provided, their detection positions are shifted, the difference between the two magnetic flux densities is calculated, and when the difference exceeds a predetermined threshold value, It is configured to provide an output indicating that the piston is at a predetermined position.

FIG. 7 is a block diagram of this embodiment, and portions corresponding to FIG. 2 are denoted by the same reference numerals.

In this embodiment, each detection coil 6 ₁ ,
6 ₂ as in the first embodiment described above, by applying the rectangular excitation pulse, the output of the detection coil 6 _and 62, respectively peak hold at each peak hold circuit 13 _1, 13 _2,
The outputs of the peak hold circuits 13 ₁ and 13 ₂ are differentially amplified by a differential amplifier circuit 15, and the output of the differential amplifier circuit 15 is compared with a predetermined threshold by a comparator circuit 14 so as to provide an output. Make up.

FIGS. 8 and 9 are signal waveform diagrams for explaining the operation, and are signal waveform diagrams corresponding to FIGS. 3 and 4 of the above embodiment. Note that, in FIG.
An output corresponding to the detection coil ₆₁ in the solid line respectively show an output corresponding to the second detection coil 6 ₂ by broken lines.

FIG. 8 shows one end of each of the detection coils 6 ₁ and 6 ₂ .
When a pulse-like voltage shown in FIG. 9A or FIG. 9A is applied, when no external magnetic field is applied,
The detection currents shown in FIG. 8B respectively flow, and the outputs of the peak hold circuits 13 ₁ and 13 ₂ become substantially constant and equal as shown in FIG. 8C.

However, the piston 2 incorporating the magnet 3
When a magnetic field is applied from the outside close to the detection coils 6 ₁ and 6 ₂ , the coil current exceeds the saturation magnetic flux density at a smaller place, and the inductance of the coil decreases, and as shown in FIG. Flows more, and the output values of the peak hold circuits 13 ₁ and 13 ₂ increase as shown in FIG. 9C.

Further, since the two detection coils 6 ₁ and 6 ₂ are arranged so as to be displaced in the axial direction of the cylinder 1, the magnitude of the magnetic flux density acting on each of the detection coils 6 ₁ and 6 ₂ is different. The detected current shown in FIG. 9B, and therefore, the output values of the peak hold circuits 13 ₁ and 13 ₂ are also shown in FIG.
As shown in (c), a difference Δ occurs.

In this embodiment, the first detection coil 6
Difference shown in FIG. 9 by subtracting the output from the output of the peak hold circuit 13 ₁ corresponding to the _first peak-hold circuit 6 ₂ corresponding to the second detection coil 6 ₂ (d) is, exceeds a predetermined threshold value Sometimes, the configuration is such that the output from the comparator circuit 14 is given assuming that the piston 2 is at a predetermined position.

FIG. 10 is a diagram showing the relationship between the position of the magnet 3 incorporated in the piston 2 and the magnetic flux density on the surface of the cylinder 1, and also shows the positions of the respective detection coils 6 ₁ and 6 ₂ . .

The magnet 3 incorporated in the piston 2 exhibits a magnetic flux density distribution (axial component) on the cylinder surface as shown. In the magnetic flux density distribution,-indicates a magnetic flux from right to left in the figure, and + indicates a magnetic flux from left to right in the figure as indicated by an arrow B.

The magnetic flux density distribution shown in FIG.
It moves with the movement of the magnet 3 in FIG. 10 (b), but the two detection coils 6 ₁ and 6 ₂ detect the magnetic flux density at each of the installation positions, and the difference becomes larger than a predetermined threshold value. When this happens, the output is given assuming that the piston 2 is at a predetermined position.

That is, in this embodiment, FIG.
In the left slope in the magnetic flux density distribution of the chevron curve shown in (a), when the difference D between the magnetic flux density detected by the detection coil 6 _1, 6 ₂ is equal to or greater than the threshold value, the piston is in position Give output as it comes.

When the differential outputs of the two detection coils 6 ₁ and 6 ₂ , which are displaced along the direction of movement of the piston 2, exceed a predetermined threshold value,
Is given at a predetermined position, the residual magnetism and the terrestrial magnetism of the cylinder 1 can be canceled out and removed.
Highly accurate detection can be performed.

The amount of displacement of the two detection coils 6 ₁ , 6 _{2 in} the axial direction is appropriately set based on, for example, data of measured magnetic flux distribution, and the two detection coils 6 ₁ , 6 ₂
In the same manner as in the first embodiment, the two detection coils 6 ₁ and 6 ₂ are moved along the cylinder 1 while the piston 2 is stopped at a predetermined position to be detected. This is installed at the outer peripheral position of the cylinder 1 where the output of the magnetic sensor A 'can be obtained. Therefore, when the piston comes to the position of the installed magnetic sensor A ', the magnetic sensor A' detects the piston position.

(Embodiment 3) FIG. 11 is a schematic structural view corresponding to FIG. 7 of still another embodiment of the present invention.
Corresponding parts are provided with the same reference symbols.

First, prior to the description of the third embodiment, the problems of the second embodiment will be described.

In the second embodiment, the magnetic sensor A '
Although the mounting direction and mounting position of the magnetic sensor A ′ were not described in detail,
In the case where it is mounted on the rod end side or the head end side, the following problems may occur.

12 to 14 show the axial magnetic flux density distribution (a) on the cylinder surface and the position of the piston 2 (b) when the material of the cylindrical cylinder 1 is a magnetic material.
FIG.

FIG. 12 shows a measured magnetic flux density distribution when the piston 2 is located at the center of the cylinder 1.
As is clear from this figure, the magnetic flux density distribution shows one peak at the center of the cylinder 1. This is due to the magnet 3 embedded in the piston 2. However, it can be seen that such a peak of the magnetic flux density distribution occurs near both ends of the cylinder 1 in addition to the center of the cylinder 1.

This is because, as shown in FIG. 15, the magnetic flux passing through the inside of the cylindrical cylinder 1 leaks intensively at the edge of the cylinder 1. For this reason, a peak of the magnetic flux density distribution occurs at both ends of the cylinder 1 irrespective of the absence of the piston 2.

FIGS. 13 and 14 show magnetic flux density distributions when the piston 2 is at each end of the cylinder 1, that is, at the rod end side and the head end side. As is clear from these figures, FIG. Since the peak of the magnetic flux density distribution due to the magnet 3 embedded in the piston 2 and the peak of the magnetic flux density distribution leaking from the end of the cylinder 1 overlap, the inclination of the peak of the magnetic flux density distribution generated by the magnet 3 on the cylinder end side is reduced. You can see that they are buried. That is, as shown in FIG. 13, when the piston 2 is on the rod end side, the inclination of the peak of the magnetic flux density distribution by the magnet 3 on the rod end side is buried.
As shown in FIG. 14, when the piston 2 is on the head end side, the head end side of the peak of the magnet density distribution by the magnet 3 is buried.

Here, the attachment of the magnetic sensor to the cylinder 1 will be described. Usually, the magnetic sensor A '
As shown in FIG. 16, a pair is attached to both ends of the cylinder 1. This is because the piston 2 is detected at the top dead center and the bottom dead center of the stroke of the piston 2, that is, at both ends of the cylinder 1, in order to confirm that the piston 2 is operating normally. In addition, the mounting direction of the magnetic sensor A ′ depends on the processing of the cable 20.
The magnetic sensor A 'on the rod end side draws the cable 20 to the head end side, and the magnetic sensor A' on the head end side is mounted in the opposite direction so that the cable 20 can be pulled out to the rod end side. In FIG. 16, for convenience of explanation, the first detection coil ₆₁ 'on the distal end side of the second detection coil 6 _{and second} magnetic sensors A' magnetic sensor A to the cable 20 pulling side of, spaced Are arranged.

The relationship between the direction of the magnetic sensor and the detection output of the detection coil of the magnetic sensor is shown in FIGS. 17 and 18. These figures show a case where the magnetic sensor A 'is arranged in the center position of the cylinder 1 in the opposite direction, and (a) shows the first and second detection coils 6.
_1, 6 ₂ detection outputs 1, 2, (b) shows the orientation of the magnetic sensor, the detection output is not a clean peak as shown by the influence of magnetic flux leakage from the cylinder 1 in practice However, in these figures, for convenience of explanation, they are shown as images.

As shown in these figures, depending on the direction of the magnetic sensor A ', the direction of the peak of the detection output is inverted to a valley or a mountain. This is because, as shown in FIGS. 19 and 20, the magnetic flux of the coil generated by the current flowing through the orientation of the magnetic sensor in the detection coil 6 _and 62 the orientation and, of the magnetic flux of the magnet 3 embedded in the piston 2 This is because the direction of the change of the detection output changes depending on whether the directions are the same direction or the opposite direction. Note that FIG.
20A and FIG. 20A show a magnetic sensor, and FIG.
The piston, (c) shows the detection outputs, arrows B are the direction of the current, arrow C the detection coil 6 _1,
The direction of the magnetic flux generated in the 6 _2, arrow D in the direction of the magnetic flux of the magnet 3, arrow E indicates the direction of movement of the piston 2, respectively.

In the second embodiment, when the differential output obtained by subtracting the detection output of the other detection coil from one detection coil exceeds a predetermined threshold, the detection output of the magnetic sensor is given. Yes, for example, FIG. 21 or FIG.
As shown in the detection output (a) of each of the detection coils and the detection output (b) of the magnetic sensor in FIG.
The second, shown from the detection output 1 of the detection coil ₆₁ in dashed lines
When detecting the piston 2 with the differential by subtracting the detected output 2 of the detection coil 6 _second output, a magnetic sensor,
Be arranged in any orientation, as shown on the detection output of the magnetic sensor in each figure (b), use the detection coil 6 _and 62 of the head end side of the peak detection output, the right side of the slope of the FIG. Will be detected. That is, the detection output of the first detection coil ₆₁ and the second detection coil 6 _second detection output 2
, And the difference is positive using an area where the difference is positive. FIGS. 21 and 22 show a state where the piston 2 at the center position is detected when the magnetic sensor is arranged at the center position of the cylinder 1.

[0064] That is, in the second embodiment described above, the first detection coil 6 ₁ from the first detection coil ₆₁ disposed near the tip end of the magnetic sensor than the second detection coil 6 of the _second differential output obtained by subtracting the detected output of the detection coil 6 _2, when it exceeds a predetermined threshold, in the configuration that gives the detection output of the magnetic sensor, by utilizing the inclination of the head end side of the peak detection output piston 2 will be detected.

However, as described above with reference to FIGS. 13 and 14, the magnetic flux passing through the inside of the cylinder 1 leaks intensively to both ends of the cylinder 1, so that the magnetic flux density Distribution peaks occur.

Therefore, in the second embodiment described above, when the magnetic sensor A ′ is disposed on the rod end side to detect the piston 2, as shown in FIGS. Toward the headend, that is,
Since it detected using the right side of the slope of the Figure, although a first detection output of the detection coil ₆₁ can be correctly detected above the detection output of the second detection coil 6 _2, magnetic sensors A '
When the piston 2 is detected by disposing the piston 2 on the head end side, as shown in FIGS. 25 and 26, the peak of the detection output is closer to the head end, that is, the inclination toward the right in FIG. As a result, the magnetic flux density distribution leaking from the end is buried in the peak, and a detection output cannot be obtained.

[0067] Similarly, in the case of detecting the piston 2 with the differential output of the detection output of the second detection coil 6 ₂ minus first detection output of the detection coil _61, the peak of the magnetic flux density distribution Therefore, when the magnetic sensor A ′ is disposed on the head end side to detect the piston 2, the detection output of the _second detection coil 62 is Although the detection output exceeds the detection output of the _first detection coil 61, the magnetic sensor A 'can be correctly detected.
Is disposed on the rod end side to detect the piston 2, the inclination of the peak of the detection output near the rod end is
This is buried in the peak of the magnetic flux density distribution leaking from the rod end of the cylinder 1, and a detection output cannot be obtained.

Therefore, in the third embodiment, the following configuration is adopted in order to correctly detect the piston 2 regardless of whether the magnetic sensor is disposed on the rod end or the head end of the cylinder 1. ing.

That is, as shown in FIG. 11, the magnetic sensor A ″ according to the present embodiment is provided between the first and second peak hold circuits 13 ₁ and 13 ₂ and the differential amplifier circuit 15. First and second signal switching circuits 2 for switching the output of each of the peak hold circuits 13 ₁ and 13 ₂ to the non-inverting input or the inverting input of the differential amplifier circuit 15 and selecting and outputting the selected signal.
11 ₁ , 21 _2, and a switching signal for outputting the first and second switching signals indicating which of the peak hold circuits 13 ₁ , 13 ₂ to select for the signal switching circuits 21 ₁ , 21 ₂ . An output circuit 22 is provided.
Outputs a corresponding switching signal in response to a switching operation of a switching switch described later.

In this embodiment, the switching signal output circuit 22 outputs a high-level or low-level first switching signal to the first signal switching circuit 211 and a _first switching signal second switching signal of the low level or the high level is obtained by inverting the the output second to the signal switching circuit 21 _2. Each of the signal switching circuits 21 ₁ and 21 ₂
For example, when the switching signal of high level is applied, the first output of the peak hold circuit 13 ₁ selects and outputs, when the switching signal of low level is applied, selectively outputs the output of the second peak hold circuit 13 ₂ Things.

In this embodiment, the magnetic sensor A ″
Is disposed on the rod end side shown on the left side of FIG. 16 to detect the piston 2, the changeover switch selects the operation position corresponding to the rod end, and in this state, the changeover signal output circuit 22 , while outputting a first switching signal at a high level to the first signal switching circuit 21 _1, and outputs the second switching signal of a low level to a second signal switching circuit 21 _2, whereby, first signal switching circuit 21 ₁ is
While providing a first output of the peak hold circuit 13 ₁ to the non-inverting input of the differential amplifier circuit 15, the second signal switching circuit 1
3 _2, provides an output of the second peak hold circuit 13 ₂ to the inverting input of the differential amplifier circuit 15, from the first detection output of the detection coil ₆₁ by subtracting the detected output of the second detection coil 6 ₂ The differential output is compared by the comparator 14.

In this case, that is, when it is arranged on the rod end side, the inclination of the peak of the detection output near the head end, that is, the inclination not buried in the magnetic flux density distribution leaking from the rod end of the cylinder 1 is used. The detection can be performed correctly.

Next, when the magnetic sensor A ″ is disposed on the head end side shown on the right side of FIG. 16 to detect the piston 2, the changeover switch is switched to the operation position corresponding to the head end. is selected, in this state, the switching signal output circuit 22, while outputting the first switch signal of a low level to the first signal switching circuit 21 _1, a second switching signal at a high level second signal switching output circuit 21 _2, whereby the first signal switching circuit 21 _1, while providing an output of the second peak hold circuit 13 ₂ to the non-inverting input of the differential amplifier circuit 15, the second signal switching circuit 21 _2, provides an output of the first peak hold circuit 13 ₂ to the inverting input of the differential amplifier circuit 15, from the detection output of the second detection coil 6 ₂ minus the first detection output of the detection coil 6 ₁ Compare the differential output with comparator 14 It will be.

In this case, that is, in the case of disposing the cylinder 1 on the head end side, the detection output peak is detected by using the inclination near the rod end. Thus, the detection can be performed correctly without being buried in the peak of the magnetic flux density distribution leaking from the head end.

As described above, when the piston 2 is detected by disposing the magnetic sensor A ″ on the rod end side, the peak of the magnetic flux density distribution leaking from the rod end of the cylinder 1 When the magnetic sensor A ″ is disposed on the head end side and the piston 2 is detected by detecting using the inclination near the head end where the peak of the magnetic flux density distribution is not buried, the magnetic flux leaking from the head end of the cylinder 1 Since the peak of the magnetic flux density distribution of the magnet 3 of the piston 2 is detected at the peak of the density distribution by using the inclination near the rod end, the leakage from both ends of the cylinder 1 occurs regardless of the position of the cylinder. Correct detection can be performed without being affected by the magnetic flux density distribution.

FIG. 27 is a block diagram showing an example of the specific configuration of FIG. 11, and corresponding portions are denoted by the same reference characters.

[0077] Each signal switching circuit 21 _1, 21 _2, respectively conducted by high-level switching signal of two analog switches 23 _1, 23 _2; consists of 23 _3, 23 _4, the switching signal output circuit 22 switches It has the above-mentioned changeover switch 24 to be operated, the inverter 25, and the resistor R3, and when the changeover switch 24 is off, a low-level changeover signal is output to the signal changeover circuit 21 ₁ , 21 ₂ . 1, while applied to the fourth analog switch 23 _1, 23 _4, inverter 25 switch signal of a high level through the respective signal switching circuit 21 _1, 21 ₂ of the second, third analog switches 23 _2, turned on and the analog switches 23 _2, 23 ₃ provided on the 23 _3, whereby the first output of the peak hold circuit 13 ₁ via the second signal switching circuit 21 ₂ While applied to the inverting input of the dynamic amplification circuit 15,
The second output of the peak hold circuit 13 _2, via the first signal switching circuit 21 ₁ is supplied to the non-inverting input of the differential amplifier circuit 15, whereby, from the detection output of the second detection coil 6 ₂ a differential output obtained by subtracting the first detection output of the detection coil ₆₁ will be compared by the comparator 14.

When the changeover switch 24 is turned on,
The high-level switching signal is supplied to each signal switching circuit 21 ₁ , 21 ₂
First, while the fourth analog switches 23 _1, 23 ₄ given by the analog switches 23 _1, 23 ₄ are turned on, the switching signal of low level via the inverter 25, the signal switching circuit 21 _1, 21 ₂ to the second and third analog switches 23 ₂ and 23 ₃ , whereby the output of the first peak hold circuit 13 ₁ is changed to the first signal switching circuit 21 ₁
Via one applied to the non-inverting input of the differential amplifier circuit 15, the output of the second peak hold circuit 13 _2, provided via the second signal switching circuit 21 ₂ to the inverting input of the differential amplifier circuit 15 It is, thereby, resulting in a differential output from the first detection output of the detection coil 6 ₁ minus the detection output of the second detection coil 6 _2, compared by the comparator 14.

As shown in FIG. 28, the switching signal output circuit 22 includes a transistor TR, exclusive OR circuits 26 and 27, inverters 28 and 29, and resistors R4 to R4.
R7 may be used. The other configuration is the same as that in FIG. 27, and a high-level or low-level operation signal may be applied to the base of the transistor TR in response to the switching operation.

As shown in FIG. 29, two differential amplifier circuits 15 ₁ and 15 ₂ are provided, and one differential amplifier circuit 15 1
_One non-inverting input is the output of the _first peak hold circuit 13 ₁ , and the inverting input is the second peak hold circuit 13 1
Give ₂ outputs respectively, to the non-inverting input of the other differential amplifier circuit 15 _2, the output of the second peak hold circuit 13 _2, the inverting input, a first output of the peak hold circuit 13 ₁ The output of one of the differential amplifier circuits 15 ₁ and 15 ₂ is selected by the signal switching circuit 31 according to the switching signal from the switching signal output circuit 30 corresponding to the switching operation, and is compared by the comparator 14. Is also good.

[0081] That is, if you select the output of one of the differential amplifier circuit 15 ₁ in the signal switching circuit 31, subtracting the second detection output of the detection coil 6 ₂ from a first detection output of the detection coil 6 ₁ and the differential output, will be compared by the comparator 14, if you select the output of the other differential amplifier circuit 15 _2, the first detection coil ₆₁ from the detected output of the second detection coil 6 ₂ Are compared by the comparator 14.

[0082] Figure 30 (Embodiment 4) is a diagram for further explaining the operation principle of another embodiment of the present invention, FIG. (A) the detection coil 6 ₁ of this embodiment, 6 ₂
FIG. 2B is a diagram showing the magnetic flux density distribution when the piston 2 is at the detection position of the rod end.

In the above-described second embodiment, as shown in FIG. 10, the magnetic force of the magnet 3 is detected by each of the detection coils 6 ₁ and 6 ₂ , and the piston 2 is detected by using the difference therebetween. In order to secure the stroke by reducing the thickness of the piston 2 in the axial direction, the thickness of the magnet 3 embedded in the piston 2 must be reduced. In such a case, the width of the peak-shaped magnetic flux density distribution of the magnet 3 Therefore, it is difficult to perform detection using a mountain-shaped inclination as shown in FIG.

[0084] Therefore, in this embodiment, in order to be able also accurately detected in such a case, the first detection coil ₆₁ of the magnetic sensor, the magnetic force of the magnet 3 of the piston 2 at a predetermined detection position And the second detection coil 6
_2, without being affected by the magnetic force of the magnet 3 of the piston 2 in the detection position directly, are arranged in the remote location can detect residual magnetic force of the cylinder 1. The other structure is the same as the second embodiment described above, when the difference obtained by subtracting the detected output of the second detection coil 6 ₂ from a first detection output of the detection coil ₆₁ exceeds a predetermined threshold value And the detection output of the magnetic sensor.

[0085] As shown in FIG. 30, to place the magnetic sensor on the rod end side, when the piston 2 has come to the detection position of the rod end side, the magnetic force of the magnet 3 of the piston 2 in the first detection coil 6 ₁ There while being detected, the second detection coil 6 _2, without being affected by the magnetic force of the magnet 2, will detect a residual magnetic force and geomagnetism of the cylinder 1. Therefore, when the first detection output of the detection coil 6 ₁ subtracting the detection output of the second detection coil 6 _2, the detection output of the magnetic sensor is obtained by exceeding the threshold value is the difference ΔH is a large positive value Will be.

[0086] Further, a magnetic sensor, as shown in FIG. 31, even when placed on the head end side, the first detection coil ₆₁ is a magnetic force of the magnet 3 of the piston 2 in the detection position of the head-end side detecting a second detection coil 6 _2,
The residual magnetic force and the terrestrial magnetism are detected without being affected by the magnetic force of the magnet 3 of the piston 2 at the detection position. Therefore, when the first detection output of the detection coil 6 ₁ subtracting the detection output of the second detection coil 6 _2, the detection output of the magnetic sensor is obtained by exceeding the threshold value is the difference ΔH is a large positive value Will be.

On the other hand, as shown in FIG.
When the magnetic sensor is arranged on the rod end side and the piston 2 is not at the predetermined detection position, for example, the second detection coil 6
When in the _second position, the first detection coil _61, the piston 2 is not to detect the magnetic force of the magnet 3 in order not in the predetermined detection position, the second detection coil 6 _2, the piston 2
To the detects directly subjected to the magnetic force effect of the magnet 3, the from the first output of the detection coil ₆₁ subtracting the second output of the detection coil 6 _2, so the difference ΔH is negative The detection output of the magnetic sensor cannot be obtained.

[0088] Thus, the first detection coil ₆₁ are arranged so as to detect the magnetic force of the magnet 3 of the piston 2 in the predetermined detection position and the second detection coil 6 ₂ at a predetermined detection position without being affected by the magnetic force of the magnet 3 of the piston 2 directly, by arranging so as to detect the residual magnetic force of the cylinder 1, the second detection coil 6 _second detecting from the first detection output of the detection coil 6 ₁ The difference after subtracting the output is
By exceeding the predetermined threshold value, the piston 2 at the detection position can be detected.

[0089] The threshold and the first detection coil ₆₁ and the second
Etc. arrangement interval between the detection coil 6 ₂ are determined experimentally.

In this embodiment, the magnet 3 of the piston 2
Is detected using the difference between the magnetic force of the magnet 3 and the residual magnetic force, so that the thickness of the magnet 3 is smaller than that in the case of using the inclination of the mountain-shaped magnetic flux density distribution by the magnet 3 as in the second embodiment. Even if the thickness becomes thinner or the moving speed of the piston 2 becomes faster, accurate detection becomes possible.

[0091] Since the first detection output of the detection coil ₆₁ subtracting the second detection output of the detection coil 6 _2, as in the second embodiment described above, can eliminate the influence of the residual magnetic force and geomagnetism it can.

In order to eliminate only the influence of the residual magnetic force and the geomagnetism of the cylinder 1, instead of the detection coil of the present invention,
The detection may be performed using a reed switch, a magnetoresistive element, a Hall element, or the like.

In this embodiment, the first and second detection coils 6 ₁ and 6 ₂ are built in one housing, but the first and second detection coils 6 ₁ and 6 ₂ are arranged separately. Therefore, they may be arranged in a separate housing.

(Other Embodiments) In the above embodiment, the detection coils 6 ₁ and 6 ₂ are arranged in parallel with the cylinder 1, but as another embodiment of the present invention, FIG.
As shown in FIG.

In the above-described embodiment, a DC pulse is applied to the detection coil for excitation. However, in another embodiment of the present invention, the detection coil may be excited by an AC current.

In the above embodiment, the present invention is applied to a cylinder switch for detecting the position of a piston in a cylinder. However, the present invention is not limited to this. This is applicable when detecting.

[0097]

As described above, according to the present invention, the following effects can be obtained.

According to the first aspect of the present invention, a detection coil formed by winding a coil around a core material made of a soft magnetic material having a high magnetic permeability is excited, and a magnet in which a magnet is incorporated based on the detection output is excited. Since the position of the detection body is detected, the detection can be performed with higher sensitivity than in the conventional example using a reed switch, a magnetoresistive element, a Hall element, or the like.

According to the second aspect of the present invention, since the change in the magnetic permeability in the high magnetic permeability region of the magnetic saturation characteristic curve of the core material is utilized, the change in the inductance of the coil of the detection coil is increased, and the sensitivity is increased. Can be detected.

According to the third aspect of the present invention, at least two detection coils are provided, and each of the detection coils is disposed at a position shifted in the moving direction of the object to be detected, and based on the difference between the detection outputs. Since the position is detected, the position can be detected with high accuracy without being affected by residual magnetic force, geomagnetism, or the like.

According to the present invention, the object to be detected is detected based on a difference obtained by subtracting the detection output of the second detection coil from the detection output of the first detection coil, or Whether the object to be detected is detected based on a difference obtained by subtracting the detection output of the first detection coil from the detection output of the detection coil can be switched. Alternatively, when it is arranged on the rod end side, the object to be detected can be detected based on the difference which is not affected by the magnetic flux leaking from both ends of the cylinder.

According to the fifth aspect of the present invention, the first detection coil for detecting the magnetic force of the magnet of the object at the predetermined position and the influence of the magnetic force of the magnet of the object at the predetermined position are determined. And a second detection coil that is disposed apart from the first detection coil so as not to receive and detects the residual magnetic force, so that the two detection coils detect the magnetic force of the magnet together, For example, the detected object can be detected even when the thickness of the magnet is thin or when the moving speed of the detected object is high, as compared with the configuration in which the detected object is detected using the mountain-shaped inclination of the magnetic flux density distribution.

According to the sixth aspect of the present invention, the position of the piston in the cylinder can be detected with high accuracy without being affected by the residual magnetism or geomagnetism of the cylinder. It is not necessary to be made of stainless steel, aluminum or the like as in the above, and it can be made of a magnetic material such as iron, so that the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of a main part according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of the magnetic sensor of FIG.

FIG. 3 is a signal waveform diagram when there is no external magnetic field.

FIG. 4 is a signal waveform diagram when an external magnetic field is present.

FIG. 5 is a diagram showing a schematic configuration of a main part according to a second embodiment of the present invention.

FIG. 6 is a plan view of FIG. 5;

FIG. 7 is a block diagram showing a configuration of the magnetic sensor of FIG.

FIG. 8 is a signal waveform diagram when there is no external magnetic field.

FIG. 9 is a signal waveform diagram when an external magnetic field is present.

FIG. 10 is a diagram showing a position of a magnet and a magnetic flux density distribution.

FIG. 11 is a block diagram according to a third embodiment of the present invention.

FIG. 12 is a diagram illustrating a relationship between a piston at a center position and a magnetic flux density distribution.

FIG. 13 is a diagram showing a relationship between a piston on a rod end side and a magnetic flux density distribution.

FIG. 14 is a diagram showing a relationship between a piston on the head end side and a magnetic flux density distribution.

FIG. 15 is a diagram showing magnetic flux leakage from a cylinder.

FIG. 16 is a diagram illustrating a mounting state of a magnetic sensor.

FIG. 17 is a diagram conceptually showing a relationship between a direction of a magnetic sensor and a detection output.

FIG. 18 is a diagram schematically illustrating a relationship between a direction of a magnetic sensor and a detection output.

FIG. 19 is a diagram showing a relationship among a direction of a magnetic flux generated in a detection coil, a direction of a magnetic flux of a magnet of a piston, and a detection output.

FIG. 20 is a diagram illustrating a relationship among a direction of a magnetic flux generated in a detection coil, a direction of a magnetic flux of a magnet of a piston, and a detection output.

FIG. 21 is a diagram showing a relationship between a detection output of each detection coil and a detection output of a magnetic sensor.

FIG. 22 is a diagram illustrating a relationship between a detection output of each detection coil and a detection output of a magnetic sensor.

FIG. 23 is a diagram showing the relationship between the detection output of each detection coil and the detection output of the magnetic sensor when the magnetic sensor is arranged on the rod end side.

FIG. 24 is a diagram showing the relationship between the detection output of each detection coil and the detection output of the magnetic sensor when the magnetic sensor is arranged on the rod end side.

FIG. 25 is a diagram showing the relationship between the detection output of each detection coil and the detection output of the magnetic sensor when the magnetic sensor is arranged on the head end side.

FIG. 26 is a diagram showing the relationship between the detection output of each detection coil and the detection output of the magnetic sensor when the magnetic sensor is arranged on the head end side.

FIG. 27 is a block diagram showing an example of a specific configuration of FIG.

FIG. 28 is a block diagram showing another example of the specific configuration of FIG. 11;

FIG. 29 is a block diagram of another example of the third embodiment of the present invention.

FIG. 30 is a diagram for explaining the operation principle of the fourth embodiment of the present invention.

FIG. 31 is a diagram for explaining the operation principle of the fourth embodiment of the present invention.

FIG. 32 is a diagram for explaining the operation principle of the fourth embodiment of the present invention.

FIG. 33 is a plan view showing another example of the arrangement of the detection coils.

[Explanation of symbols]

A, A ', A''magnetic sensor 1 cylinder 2 piston 3 magnet 4 core 5 coils 6,6 _and 62 detection coil 12 pulse oscillation circuit 13 the peak-hold circuit 14 a comparator circuit 15 a differential amplifier circuit 21 _1, 21 ₂ , 31 signal switching circuit 22, 30 switching signal output circuit

Continuing on the front page (72) Inventor Kenji Matsui Inside Omron Co., Ltd. 10 Hanazono Todocho, Ukyo-ku, Kyoto-shi Kyoto Prefecture (72) Inventor Tomofumi Motoshi 10 Okayama Todocho, Ukyo-ku, Kyoto City, Kyoto Prefecture (72) Katsuaki Hagiwara 1-1-1, Kitaeguchi, Higashiyodogawa-ku, Osaka City, Osaka Taiyo Iron Works Co., Ltd. (72) Inventor Masaaki Tokai 1-1-1 Kitaeguchi, Higashiyodogawa-ku, Osaka-shi, Osaka Taiyo Iron Works Co., Ltd.

Claims (6)

[Claims] 1. A magnetic sensor for detecting a position of an object to be detected in a container in which a magnet is incorporated, wherein a detection coil formed by winding a coil around a core material made of a soft magnetic material having a high magnetic permeability is provided in the container. A magnetic sensor, which is disposed outside and excites the detection coil and detects the position of the object to be detected based on the detection output. 2. The method according to claim 1, wherein a change in magnetic permeability in a high magnetic permeability region of the magnetic saturation characteristic curve of the core material is detected.
A magnetic sensor as described. 3. At least two detection coils are provided,
Claims 1. A detection coil, wherein a position of the detection object is shifted in a moving direction of the detection object moving in the container, and a position of the detection object is detected based on a difference between detection outputs of the detection coils. Item 3. The magnetic sensor according to item 1 or 2. 4. A method for detecting the object to be detected based on a difference obtained by subtracting a detection output of a second detection coil from a detection output of a first detection coil, or detecting the detected object based on a detection output of the second detection coil. 4. The magnetic sensor according to claim 3, wherein whether to detect the object to be detected is switchable based on a difference obtained by subtracting a detection output of one detection coil. 5. A first detection coil for detecting a magnetic force of a magnet of the object to be detected at a predetermined position in a container, and a first detection coil for preventing the influence of the magnetic force of the magnet of the object to be detected at the predetermined position. The magnetic sensor according to claim 3, further comprising: a second detection coil that is disposed apart from the first detection coil and detects a residual magnetic force of the container. 6. The container is a cylinder, the object to be detected is a piston, an excitation signal is applied from one end of each of the detection coils, and a difference between detection outputs taken from the other ends is provided. The magnetic sensor according to any one of claims 3 to 5, wherein the position of the piston is detected by a sensor.