JP2000065511A - Magnetism detecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve use efficiency of a permanent magnet installed in a piston, and enable miniaturization of a permanent magnet and cost reduction of a cylinder tube. SOLUTION: This detecting apparatus 16 is fixed on the outer peripheral surface of a cylinder tube 11, and detects the magnetic field of a permanent magnet 14 which is installed in a piston 12 moving along the inner peripheral surface of the cylinder tube 11. The detecting apparatus 16 is provided with a magnetic sensor 34 operated by the magnetic flux generated from the permanent magnet 14, and part members 31, 32 composed of high permeability material which converge the magnetic flux generated from the permanent magnet 14 and guide the flux to the magnetic sensor 34.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic sensing device having enhanced magnetic sensitivity and a cylinder device using the same.

[0002]

2. Description of the Related Art Conventionally, a detecting device for detecting a magnetic field of a permanent magnet attached to a piston has been used to detect a piston position of a cylinder device. The sensing device includes an MR element that operates by a magnetic field (magnetic flux).
An element, a hall element, a lead switch, and the like are built in.

As the permanent magnet attached to the piston, an annular magnet having a diameter slightly smaller than the outer diameter of the piston is used. As cylinder devices are provided with various inner diameters of cylinder tubes, permanent magnets having various diameters are manufactured and used according to the respective inner diameters.

[0004]

As described above, a ring-shaped permanent magnet is conventionally used, but since the detection device operates by being attached to a part of the periphery of the cylinder tube, the detection device is not used. Of the magnetic flux emerging toward the entire circumference, only a small part of the magnetic flux is used to activate the sensing device, and most of the remaining magnetic flux is not effectively used. That is, the utilization efficiency of the permanent magnet is poor.

[0005] Therefore, a permanent magnet having an excessive size or performance is used, and the permanent magnet required for operating the detection device is enlarged as a whole.

Further, since the efficiency of using the permanent magnet is poor, it is necessary to reduce the thickness of the cylinder tube, and it is necessary to use a high-strength and expensive material as the material of the cylinder tube.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is possible to increase the efficiency of using a permanent magnet mounted on a piston or the like, to reduce the size of the permanent magnet or reduce the cost of a cylinder tube. It is an object to provide a magnetic sensing device.

[0008]

According to a first aspect of the present invention, there is provided an apparatus for detecting a magnetic field of a permanent magnet mounted on one surface of a wall member and moving along the other surface of the wall member. A magnetic sensor operated by magnetic flux emitted from the permanent magnet, and a magnetic flux collecting member made of a high magnetic permeability material for focusing the magnetic flux emitted from the permanent magnet and guiding the magnetic flux to the magnetic sensor. Have.

In the apparatus according to a second aspect of the present invention, the magnetic flux collecting member has a rear surface shape along the surface of the wall member so as to be arranged at a position close to the wall member. A leg extending in a direction perpendicular to the direction; and an operating portion continuously extending from the leg to a vicinity of a surface of the magnetic sensor.

According to a third aspect of the present invention, in the cylinder device, the magnetic detection device according to the first aspect is attached to the cylinder tube of the cylinder device as the wall member, and the magnetic detection device is mounted on a piston of the cylinder device. The permanent magnet is mounted only on the side where the device is mounted.

As the material of the magnetic flux collecting member, amorphous alloy, permalloy, silicon steel, iron cobalt alloy, iron nickel alloy, permalloy clad stainless steel, or the like is used.

As a magnetic sensor, a Hall element, a Hall I
C, a magnetoresistive element (MR element), a magnetic transistor, a reed switch, a proximity sensor, a coil, and the like are used.

[0013]

FIG. 1 shows a detecting device 16 according to the present invention.
FIG. 2 is a sectional front view of a fluid pressure cylinder 1 to which is attached.
3 is a sectional side view of the fluid pressure cylinder 1. FIG.

In these figures, a hydraulic cylinder 1
Are the cylinder tube 11, the piston 12, the piston rod 13, the permanent magnet 14, the packing 15, the detection device 1
6 and a cylinder cover (not shown).

The cylinder tube 11 is often
It is made of a non-magnetic material such as an aluminum alloy, stainless steel, or a synthetic resin. However, it is also possible to use a magnetic material such as a carbon steel pipe for the reasons described below.

The piston 12 is made of a non-magnetic material such as an aluminum alloy or stainless steel, and has a permanent magnet 14 and a packing 15 mounted in an annular groove provided on the outer periphery.

The piston rod 13 is made of steel or the like, and the piston 1 is formed by a screw or the like provided at the tip thereof.
2 and are integrally connected. The permanent magnet 14 is annular, and has an N pole and an S pole in a direction along the axial direction of the piston rod 13. Various materials can be used for the material of the permanent magnet 14, but using ferrite or a synthetic resin is advantageous in terms of cost. The outer diameter of the permanent magnet 14 is considerably smaller than the inner diameter of the cylinder tube 11, and a packing 15 is mounted in the gap. The packing 15 keeps the space between the inner peripheral surface of the cylinder tube 11 and the piston 12 airtight.

The detecting device 16 detects the magnetic field of the permanent magnet 14, and thereby detects the position of the piston 12. The detection device 16 includes a casing 30, magnetic flux collecting members 31 and 32, a magnetic sensor 34, a cable 37, a board (not shown) on which an electric circuit is mounted, and other members.

The casing 30 is made of a synthetic resin or the like, and accommodates components such as the magnetic flux collecting members 31 and 32 and a substrate therein. The magnetic flux collecting members 31 and 32 are for converging the magnetic flux emitted from the permanent magnet 14 and guiding the magnetic flux to the magnetic sensor 34. desirable. The two magnetic flux collecting members 31 and 32 have the same shape as each other. Each of the magnetic flux collecting members 31 and 32 has a back surface shape along the surface of the cylinder tube 11 so as to be arranged at a position close to the cylinder tube 11 and extends in the circumferential direction and a leg portion 51 and a leg portion 5.
It has an action portion 52 that continuously extends from 1 to near the surface of the magnetic sensor 34. The gap GP between these action parts 52, 52
, A magnetic sensor 34 is interposed.

Therefore, the leg 51 is disposed in contact with the surface of the cylinder tube 11 or with a sufficient gap of about several millimeters. Working part 52
Is a rod-shaped member extending in the left-right direction of FIG. 1. The action portions 52, 52 of the two magnetic flux collecting members 31, 32 are such that their respective tips are in contact with the respective surfaces of the magnetic sensor 34 or are Are arranged with a gap of about several millimeters.

Since the magnetic sensor 34 detects the magnetic flux passing in the left-right direction in FIG. 1 with the highest sensitivity, the magnetic sensor 34 detects the magnetic flux from one operating portion 52 to the other operating portion 52 with high sensitivity. These magnetic flux collecting members 31 and 32 are arranged as a whole in the direction of both magnetic poles of the permanent magnet 14, that is, along the axial direction of the cylinder tube 11.

As a material of the magnetic bypass members 31 and 32, a high magnetic permeability material or a ferromagnetic material which easily passes a magnetic flux is used. For example, amorphous alloy, permalloy, silicon steel, iron cobalt alloy, iron nickel alloy, permalloy clad stainless steel, or the like is used. These materials are materials used for a magnetic shield, a magnetic head core, and the like, and have a large maximum relative magnetic permeability of 10,000 or more. It also has a low coercive force and is therefore a soft magnetic material.

As the magnetic sensor 34, a Hall element, a Hall IC, a magnetoresistive element (MR element), a magnetic transistor, a reed switch, a proximity sensor, or the like is used. The position of the magnetic sensor 34 is the gap GP between the two working portions 52, 52 in the figure, but is a close position around the working portions 52, 52 and the working portion 5 in the axial direction.
The position may be such that the positions overlap with the positions 2 and 52. For example, the magnetic sensor 34 may be arranged so that it is located above the magnetic flux collecting members 31 and 32 and the center of the magnetic sensor 34 is located directly above the gap between the acting portions 52 and 52. The magnetic sensor 34 is connected to the operation unit 5
2 and 52, the action section 52,
There is no need to make the size of the gap GP of 52 dependent on the size of the magnetic sensor 34, and the size of the gap GP can be designed to an optimum value.

The substrate (not shown) includes a detecting device 16
Is provided, and a power supply circuit, an amplifier circuit, an output circuit, a display circuit, and a magnetic sensor 34 (not shown) are mounted on the circuit pattern.

The cable 37 is for supplying power to the substrate, extracting an output signal based on the operation of the magnetic sensor 34, and the like. Usually, when power supply and output are commonly performed, two cables are used. If the wires perform them separately, three wires are used each.

Next, the operation of the above-described hydraulic cylinder 1 will be described. In FIG. 1, the magnetic flux emitted from the north pole of the permanent magnet 14 passes through the surrounding space and returns to the south pole. Most of the magnetic flux is focused on the magnetic flux collecting members 31 and 32 and passes through the magnetic flux collecting members 31 and 32. Two working parts 5
The magnetic flux passes through the magnetic sensor 34 at the opposing portions 2 and 52. That is, many magnetic fluxes pass through the magnetic sensor 34.

When the amount of magnetic flux passing through the magnetic sensor 34, that is, the strength of the magnetic field becomes equal to or more than a certain value, the detecting device 16 outputs a detection signal and the display element of the display circuit is turned on. The detection signal is a switching signal for turning on an external load. The detection signal may be a signal corresponding to the strength of the detected magnetic field.

According to the detection device 16 described above, the magnetic flux emitted from the permanent magnet 14 is focused by the magnetic flux collecting members 31 and 32, and a large part of the magnetic flux emitted from the permanent magnet 14 efficiently passes through the magnetic sensor 34. Therefore, the permanent magnet 14
Even if the magnetic force of the permanent magnet 14 is not so strong and the permanent magnet 14 is separated from the detection device 16, the presence of the permanent magnet 14 can activate the detection device 16.

Therefore, the size and cost of the permanent magnet 14 can be reduced. Further, it is possible to increase the thickness of the cylinder tube 11 to improve the strength, and to use an inexpensive material for the cylinder tube 11. Also, as shown in FIG. 1, the outer diameter of the permanent magnet 14 is reduced,
The packing 15 can be mounted on the outer peripheral surface. Therefore, permanent magnets 14 of the same size can be used by being mounted on pistons of fluid pressure cylinders having different inner diameters. Then, the standardization of the permanent magnet 14 is promoted, and the cost is reduced.

FIG. 3 is a perspective view of magnetic flux collecting members 31A and 32A of a detecting device 16A according to another embodiment of the present invention, and FIG. 4 is a diagram showing the magnetic flux collecting members 31A and 32A shown in FIG.
FIG. 5 is a side view of the magnetic flux collecting members 31A and 32A shown in FIG.

In these figures, the magnetic flux collecting members 31A and 32A used in the detecting device 16A are arranged such that the magnetic flux collecting members 31A and 32A are arranged close to the cylinder tube 11.
1. A leg 61 having a back surface shape along the surface of the first and extending in the circumferential direction, and a magnetic sensor 34A continuously from the leg 61.
Has an action portion 62 reaching the vicinity of the surface.

The leg portion 61 is widened in the axial direction at a boundary portion with the action portion 62 so that the magnetic flux focused from the back surface of the leg portion 61 can be efficiently guided to the end face of the action portion 62. . Therefore, the magnetic flux of the permanent magnet 14A efficiently passes through the magnetic sensor 34A.

In the fluid pressure cylinder 1A, a plurality of holes are provided in the piston 12A in the axial direction inside the packing 15, and a plurality of columnar permanent magnets 1 are provided therein.
4A is embedded. When the piston 12A does not rotate with respect to the cylinder tube 11, it is not necessary to provide these permanent magnets 14A all around the piston 12A.
An appropriate number may be provided on the side where the detection devices 16A are arranged.
This also makes it possible to effectively use the magnetic flux of the permanent magnet 14A.

Further, as described above, even when a magnetic material such as a carbon steel pipe is used as the material of the cylinder tube 11, the detection by the detection devices 16, 16A is possible.

That is, the magnetic flux collecting members 31, 32, 31A,
When a material having a relative magnetic permeability of 10,000 or more is used as 32A, the relative magnetic permeability of a carbon steel pipe or the like is about several hundreds. Therefore, the magnetic flux collecting member has a higher magnetic permeability than a cylinder tube made of a carbon steel pipe. Is several orders of magnitude or more, which is an order of magnitude larger, and most of the magnetic force lines near the legs 51 and 61 of the magnetic flux collecting member flow into the magnetic flux collecting member. That is, the magnetic flux collecting members 31, 32, 31
A and 32A have a function of bypassing the magnetic flux flowing through the cylinder tube 11 and allowing a large amount of magnetic flux to pass through the magnetic sensors 34 and 34A. Cylinder tube 1
When a carbon steel pipe is used as the material of No. 1, the thickness of the cylinder tube 11 can be reduced, the outer diameter can be reduced,
The entire hydraulic cylinders 1 and 1A can be reduced in size. Further, since the thickness of the cylinder tube 11 is reduced, the material cost can be reduced and the weight can be reduced.

In the detection device 16 of the above embodiment,
The leg portions 51 of the magnetic flux collecting members 31 and 32 are configured to be exposed from the lower surface of the casing 30 to the outside.
32 may be configured to fit inside the casing 30. Cylinder tube 1
Although the shape is along the surface of No. 1, it may be linear (flat) if it is not too long. Further, the permanent magnets 14, 14
The shape, material, size, and number of A can be various. A plurality of detectors 16, 16A can be attached to one fluid pressure cylinder 1, 1A. The structures, shapes, dimensions, and the like of the detection devices 16, 16A and the fluid pressure cylinders 1, 1A can be appropriately changed in accordance with the gist of the present invention. The detection device of the present invention can be applied to detection of the position of various cylinder devices other than the fluid pressure cylinders 1 and 1A, and other devices.

[0037]

According to the present invention, the utilization efficiency of the permanent magnet mounted on the piston or the like can be enhanced, and the size of the permanent magnet can be reduced or the cost of the cylinder tube can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional front view of a hydraulic cylinder to which a detection device according to the present invention is attached.

FIG. 2 is a sectional side view of a hydraulic cylinder.

FIG. 3 is a perspective view of a magnetic flux collecting member of a detection device according to another embodiment of the present invention.

FIG. 4 is a front view showing a state where the magnetic flux collecting member shown in FIG. 3 is attached to a fluid pressure cylinder.

FIG. 5 is a side view of the magnetic flux collecting member shown in FIG.

[Explanation of symbols]

 1, 1A Fluid pressure cylinder 11 Cylinder tube (wall member) 12 Piston 14, 14A Permanent magnet 16, 16A Detector (magnetic detector) 31, 31A, 32, 32A Magnetic collector 34 Magnetic sensor 51, 61 Leg 52, 62 action part

Continued on front page F term (reference) 2F063 AA02 BA05 BD01 BD15 CA34 DA01 DD02 GA51 GA53 GA80 MA03 2F077 AA10 JJ03 JJ08 JJ09 JJ12 JJ13 JJ23 VV02 VV11 VV35 3H081 AA03 GG15 GG22

Claims (3)

[Claims] 1. A detecting device for detecting a magnetic field of a permanent magnet attached to one surface of a wall member and moving along the other surface of the wall member, wherein the detecting device detects a magnetic field from the permanent magnet. A magnetic detection device comprising: a magnetic sensor that operates; and a magnetic flux collecting member made of a material having a high magnetic permeability for converging a magnetic flux emitted from the permanent magnet and guiding the magnetic flux to the magnetic sensor. 2. A leg extending in a direction perpendicular to a moving direction of the permanent magnet, wherein the magnetic flux collecting member has a rear surface shape along a surface of the wall member so as to be arranged at a position close to the wall member. The magnetic sensing device according to claim 1, further comprising: an operating portion that continuously extends from the leg portion to a vicinity of a surface of the magnetic sensor. 3. The magnetic detection device according to claim 1, wherein a cylinder tube of the cylinder device is used as the wall member, and the piston of the cylinder device is provided only on a side on which the magnetic detection device is mounted. A cylinder device comprising the permanent magnet mounted thereon.