JPH05264206A - Magnetic sensor and device for detecting magnetic displacement - Google Patents

Abstract

PURPOSE:To facilitate measuring at high sensitivity and high accuracy by amplifying changes in magnetic flux density and to facilitate measuring with large gaps or inside hydraulic equipment. CONSTITUTION:A magnetic sensor comprises a magnet 1 having a width of more than one pitch of a magnetic scale 21, and a first and second sensor 31, 32 disposed near the lower portion of the end face of the magnet 1 and in a position of half of one pitch of the magnetic scale 21, and a sensor 3 for detecting magnetic flux density through differential action. A magnetic displacement detecting device comprises a pair of members 4, 5 movable relative to each other, a magnetic scale 42 comprising a magnetic graduation 41 formed in one of the members (4), and the magnetic sensor 7 disposed on the other member 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic sensor and a magnetic displacement detecting device used for magnetically measuring a displacement amount, a displacement speed and the like.

[0002]

2. Description of the Related Art As shown in FIG. 7, a conventional magnetic sensor has a prismatic bar magnet B arranged at right angles to a magnetic scale M.
And a sensor H that is smaller than the area of the S pole disposed near the S pole at the lower end of the bar magnet B, and detects the displacement by detecting the change in the magnetic flux density due to the relative movement of the magnetic scale. Is.

[0003]

In the above-mentioned conventional magnetic sensor, since the magnet B is a bar magnet and the width thereof is narrow, the magnetic flux density that can be detected by the sensor H is small. Therefore, when the gap between the sensor and the magnetic scale M becomes large, reading is not possible. Therefore, there is a problem in that it is difficult to incorporate the hydraulic equipment into the hydraulic equipment for measurement.

In order to solve the above-mentioned conventional problems, the inventors of the present invention have the idea of expanding the magnet width to make a large magnet by conversely thinking the conventional way of narrowing the magnetic flux by narrowing the magnet width. Focusing on the technical idea that the magnetic flux density will increase if this is done, and as a result of repeated research and development, a book that amplifies changes in the magnetic flux density and enables measurement in the case of large gaps and in hydraulic equipment The invention has been reached.

[0005]

A magnetic sensor according to the present invention (the first invention according to claim 1) has at least one pitch of a magnetic scale in which band-shaped magnetic displacement portions having different magnetic properties are regularly arranged. And a sensor having a cross-sectional area smaller than the area of the end face, which is disposed near the lower part of the end face of the magnet and which detects a change in magnetic flux density generated by the magnet.

A magnetic sensor of the present invention (the second invention according to claim 2) is the magnetic sensor according to the first invention, wherein the sensor is arranged at a position of a half pitch of the magnetic scale.
And a second sensor, which has a differential type configuration capable of differentially detecting the magnetic flux density.

A magnetic displacement detecting device of the present invention (the third invention according to claim 3) is a pair of members that are relatively movable,
A magnetic scale having a magnetic scale formed by regularly arranging strip-shaped magnetic displacement portions having different magnetic properties on one member of the pair of members, and a magnetic scale of the magnetic scale on the other member of the pair of members. Of a magnet having a width of 1 pitch or more, and first and second sensors respectively arranged below the end surface of the magnet at a position corresponding to a half pitch position of the magnetic scale on the other member. , A magnetic sensor for detecting a change in magnetic flux density according to relative movement of the pair of members.

[0008]

In the magnetic sensor according to the first aspect of the present invention having the above structure, the magnet of the magnetic sensor has a large width and a large size.
Since the magnetic flux emitted from the poles increases, a sensor arranged close to the lower part of the end face of the magnet detects a large change in the magnetic flux density.

In the magnetic sensor according to the second aspect of the present invention having the above structure, the first and second sensors are arranged at positions of a half pitch of the magnetic scale, and the change signals having different polarities of the magnetic flux density are differentiated. Since it is detected dynamically, the change in the magnetic flux density twice that of the first invention is detected.

In the magnetic displacement detecting device of the third invention having the above-mentioned structure, the magnet is widened and enlarged, and the first and second sensors are arranged at positions of a half pitch of the magnetic scale. Then, the change signal of the magnetic flux density having different polarities is differentially detected according to the relative movement of the pair of members.

[0011]

The magnetic sensor according to the first aspect of the present invention, which has the above-described operation, is large in size as compared with the conventional magnetic sensor and therefore detects a large change in the magnetic flux density. It has an effect of enabling measurement in a large case or in a hydraulic device.

In the magnetic sensor of the second invention having the above-mentioned operation, the first and second sensors are arranged at the position of a half pitch of the magnetic scale as compared with the magnetic sensor of the first invention, and the magnetic flux density Since the change signals having different polarities are differentially detected, it is possible to perform detection with higher sensitivity, and it is possible to perform measurement in the case of a large gap or in hydraulic equipment.

The magnetic displacement detection device of the third invention having the above-mentioned operation enables highly sensitive detection as in the second invention, and therefore, when the gap between the sensor and the magnetic scale or the magnetic scale is large, or when there is a pair of magnetic scales. It is possible to perform the measurement when the member is placed in the oil in the hydraulic device.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) The magnetic sensor of the first embodiment is an embodiment of the second invention, and as shown in FIG. 1, the magnetic scale 2 constitutes a strip-shaped flat plate made of a magnetic material in the width direction. Facing the non-magnetic magnetic scales 21 formed at intervals,
The magnet means 1 in which a cubic bar magnet 11 having a length corresponding to one pitch of the magnetic scale 21 is arranged is arranged, and is arranged below the S extreme surface of the bar magnet 11 in FIG. The sensor 3 is constructed by arranging the first and second sensors 31 and 32, which are Hall elements sufficiently smaller than the area of the magnet, in the member at positions of a half pitch of the magnetic scale, respectively, to form the sensor 3. 1 and the relative displacement of the sensor 3 and the magnetic scale 2 are detected by the magnet means 1 and the magnetic scale 2.
This is detected by the change in the density of the magnetic flux generated in the.

In the magnetic sensor of the first embodiment having the above-described structure and operation, since the bar magnet 11 is wide and large in size, a large magnetic flux density is formed, and the magnetic flux is generated by the first and second sensors 31 and 32. Since the change signal of the density is detected differentially and the output is doubled as shown in FIG. 3, the change of the magnetic flux density is detected with the sensitivity of about 5 times as compared with the conventional sensor as shown in FIG. , Sensor 3 and magnetic scale 2
This has the effect of making it possible to perform measurement in the case where there is a large gap with or in hydraulic equipment.

(Second Embodiment) The second embodiment corresponds to the embodiments of the second invention and the third invention, and is a magnetic sensor and a magnetic displacement detecting device in hydraulic equipment using the magnetic sensor (hereinafter This is simply referred to as a magnetic displacement detection device).

(Structure of Second Embodiment) As shown in FIGS. 4 and 5, the magnetic displacement detecting device of the second embodiment has an axially movable hollow cylinder 4 having a magnetic scale, and a hollow cylinder. A rod 5 coaxially fixed in the body 4, and a rod 5
6 disposed at the tip of the cylinder and inserted in the hollow cylindrical body 4
And a magnetic sensor 7 arranged on the outer peripheral wall of the piston 6.

The hollow cylindrical body 4 is made of non-magnetic steel locked to a moving member (not shown), and has belt-like magnetic graduations 41 magnetized at equal intervals on its inner peripheral wall.
The magnetic scale 42 is formed, and the inside thereof is filled with oil.

The rod 5 is a rod-shaped member 50 which is locked to a fixed member (not shown), and a lead wire of a magnetic sensor 7 described later is arranged inside.

The piston 6 is composed of a piston body 60 formed at the tip of the rod 5, and has a throttle 61 (not shown) for controlling the amount of oil passage and a recess 61 for arranging the magnetic sensor 7. ..

The magnetic sensor 7 is disposed so as to be entirely surrounded by a member in the recess 61 at a slight distance from the outer peripheral wall of the piston 6 so as not to come into direct contact with oil.
As shown in FIGS. 4 and 5, a wide and large bar magnet 70, which is a cube composed of each side corresponding to one pitch of the magnetic scale 41, is formed, and the bar magnet 70 is provided on the right side of the S extreme surface. The first and second sensors 71 and 72 composed of Hall elements that are sufficiently smaller than the area of the S-extreme surface are provided on the magnetic scale
The sensors 73 are formed by arranging them at a pitch of one-half.

The hollow cylindrical body 4 constituting the magnetic scale 42 is made of iron by feeding a carbon dioxide gas laser welding machine to a non-magnetic steel strip of SUS304 while supplying 35 liters of assist gas of argon 95% oxygen 5% per minute. Is supplied and laser irradiation is performed to form a 2 mm reformed portion and a 2 mm non-reformed portion that form a magnetic scale 22M that is rich in iron and has high magnetism at equal intervals.

The steel strip on which the laser modified portion is formed is gradually cooled in a bright annealing furnace (not shown) at 600 ° C. for 24 hours to soften and grind the modified bead portion of the laser modified portion. The bead-ground strip steel is passed through a rolling mill three times, adjusted to have a thickness of, for example, 1.6 mm, and soft-annealed as described above.

The annealed rolled strip steel is bent by an electric resistance welded pipe manufacturing machine into a tubular shape, and both ends thereof are electrically welded to form a pipe.
Molded into a pipe with an outer diameter of 38.1 mm and an inner diameter of 34.9 mm, TI
Weld the welded portion with a G welder.

The welded pipe is cooled to 55 in a bright annealing furnace.
After being gradually cooled at 0 ° C. for 2 hours to remove the strain in the welded portion, it is further pretreated with a resin by a pipe drawing machine, oil-lubricated and drawn out, and then softened and annealed in the same manner as described above.

The softened and annealed drawn pipe is finally drawn into an outer diameter of 34.6 mm and an inner diameter of 32.0 mm by a pipe drawing machine (not shown) in the same manner, and is drawn in a bright annealing furnace at 1050 ° C. for 2 hours. After being held, it is gradually cooled to 100 ° C. and then annealed again at 600 ° C. for 24 hours to manufacture the hollow cylindrical body 4 in which the magnetic scale 42 having the 2 mm pitch magnetic scale 41 is formed on the inner peripheral wall.

(Operation of the Second Embodiment) In the magnetic displacement detecting apparatus of the second embodiment having the above-mentioned structure, when the moving member moves and the hollow cylindrical body 4 forming the magnetic scale 42 moves up and down in the axial direction, Although the relative positional relationship with the magnetic sensor 7 arranged on the outer circumference of the piston 6 changes, the magnet means 70 is large and a large magnetic flux density is formed, and the two sensors 71 and 72 detect the difference differentially. Therefore, as shown in FIG. 2, it is detected as a magnetic flux change larger than in the conventional case and taken out by a lead wire.

(Effects of the Second Embodiment) In the magnetic displacement detecting apparatus of the second embodiment having the above-described operation, the modified portion (magnetic scale 41) and the non-modified portion of the magnetic scale 42 are both equidistantly spaced by 2 mm. Since the movement and displacement of the hollow cylindrical body 4 are detected with high sensitivity as a large magnetic flux change by the accurate differential output of the Hall elements 71 and 72, there is an effect of enabling high resolution and high accuracy detection. ..

Further, since the apparatus of the second embodiment enables highly sensitive detection, it is possible to perform measurement in the case where the gap between the sensor and the magnetic scale 42 is large and oil is filled as in this embodiment. It has the effect of enabling it. That is, the gap between the sensor portion and the scale portion can be increased, and the rod 5 is locked to the vehicle body, the hollow cylindrical body 4 is locked to the axle, and the shock absorber for an automobile is arranged in the absorber. It can be used in.

(Third Embodiment) As shown in FIG. 6, the magnetic sensor of the third embodiment has a thickness (instead of the cubic bar magnet 11 having one pitch of the magnetic scale of the first embodiment as one side). Figure 6
The magnets 12 and 13 having a half pitch in the middle and left and right directions are arranged in parallel and face the sensors 31 and 32, respectively, and the same effect as the first embodiment is obtained.

The above-mentioned embodiments are merely examples for the purpose of explanation, and the present invention is not limited to them. Modifications can be made without departing from the technical idea recognized by those skilled in the art from the description of the claims. And can be added.

In the second embodiment described above, the sensor is surrounded because it is filled with oil, but in the case of air, it may be exposed or may be formed on the outer peripheral portion.

In the second embodiment described above, the reformed portion and the non-reformed portion of the magnetic scale have the same width in view of the accuracy of the differential output, but it is also possible to have different widths.

[Brief description of drawings]

FIG. 1 is a perspective view showing a magnetic sensor according to a first embodiment of the invention.

FIG. 2 is a diagram showing a comparison of magnetic flux densities of the magnetic sensor of the first embodiment and a conventional sensor.

FIG. 3 is a diagram illustrating a differential output of the magnetic sensor according to the first embodiment.

FIG. 4 is a vertical sectional view showing a magnetic displacement detection device according to a second embodiment.

FIG. 5 is a transverse sectional view taken along the line AA in FIG. 3 of the magnetic displacement detection device of the second embodiment.

FIG. 6 is a sectional view showing a magnetic sensor of a third embodiment.

FIG. 7 is a perspective view showing a conventional magnetic sensor.

[Explanation of symbols]

 1, 70 Magnet Means 2, 42 Magnetic Scale 3, 73 Sensor 4 Hollow Cylindrical Body 5 Rod 6 Piston 7 Magnetic Sensor 11, 12, 13 Magnet 21, 41 Magnetic Scale 71 First Sensor 72 Second Sensor

Claims (3)

[Claims] 1. A magnet having a width of one pitch or more of a magnetic scale in which strip-like magnetic displacement portions having different magnetic properties are regularly arranged, and an area of the end surface which is disposed near a lower portion of the end surface of the magnet. A magnetic sensor having a smaller cross-sectional area and comprising a sensor for detecting a change in magnetic flux density generated by a magnet. 2. The differential type sensor according to claim 1, wherein the sensor comprises a first sensor and a second sensor which are respectively arranged at positions of a half pitch of the magnetic scale, and the magnetic flux density is differentially detected. A magnetic sensor having a configuration. 3. A pair of members that can move relative to each other, and a magnetic scale having a magnetic scale formed by regularly arranging band-shaped magnetic displacement portions having different magnetic properties on one member of the pair of members. A magnet having a width of one pitch or more of the magnetic scale of the magnetic scale on the other member of the pair of members, and a magnet at a position corresponding to a half pitch position of the magnetic scale on the other member. A magnetic displacement detection device comprising a first sensor and a second sensor respectively arranged below the end faces, and a magnetic sensor for detecting a change in magnetic flux density according to relative movement of the pair of members.