JP2002228486A - Magnetic encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized magnetic encoder not requiring high accuracy in the attachment of a magnetic field detection element onto a magnetism generator. SOLUTION: The magnetic encoder is equipped with the magnetism generator 2, and magnetic detection elements 5a, 5b, 5c and 5d arranged in the gap 4 of the magnetism generator 2, and constituted so as to process the signals outputted from the magnetic detection elements by relative rotation to detect a rotational speed or a rotary position. The magnetism generator 2 is constituted of a permanent magnet formed into a cylindrical shape and magnetized so as to generate a parallel magnetic field B in one direction equal in a vertical direction with respect to the center axis in the central gap 4. A soft magnetic body 10 for forming a magnetic circuit is provided to the outer periphery of the magnetic body 2, and the magnetic field detection elements 5a, 5b, 5c and 5d are arranged in the gap 4 with mechanical phase difference of 90 deg. each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic encoder, and more particularly to a magnetic encoder suitable for miniaturization.

[0002]

2. Description of the Related Art Conventionally, encoders for detecting the number of rotations and the rotational position of a rotating body can be classified into optical (photoelectric), magnetic, and electrostatic types according to the principle of detection. And the magnetic type is used.

As a magnetic encoder, a magnetic drum type (for example, Japanese Patent Application Laid-Open No. 54-118259) composed of a magnetic drum and a magnetic sensor magnetized in multiple directions in the circumferential direction, a disk having a gear or a slit, a magnetic sensor, and a permanent magnet In addition to the reluctance type consisting of a magnet,
As disclosed in Japanese Patent Application Laid-Open No. 65596, there is provided a magnet made of a disk-shaped permanent magnet magnetized in one direction perpendicular to the rotation axis, and a magnetic field detection opposing the magnet in the axial direction. Magnetic encoder equipped with an element
As described in Japanese Patent Application Laid-Open No. 1-237257, a fixed frame is provided around the outer periphery of the magnetic body provided with a magnetic field in one direction in the same manner as described above. A pair of two magnetic field detecting elements which are opposed to each other and have a phase difference of 90 degrees in mechanical angle are provided at positions shifted from each other by 180 degrees.

FIG. 13 is a perspective view showing an example of such a motor. Reference numeral 20 denotes a rotating body such as a motor, 21 denotes a rotating shaft thereof, and 22 denotes a magnetizing body made of a disk-shaped permanent magnet attached to the rotating shaft 21. Magnetic field B magnetized in one direction perpendicular to 21
(Arrow). Reference numeral 23 denotes a fixed frame attached to a frame or the like of the rotating body 20 by attachment means (not shown).
a, 24b, 24c and 24d are attached.

[0005]

However, when the resolution of a magnetic drum type encoder is increased, the magnetizing method and the assembly accuracy become complicated, and a finely patterned magnetic resistance element is required as a magnetic sensor. And was not suitable for miniaturization. In the case where the magnetic field detecting element is attached to the permanent magnet disk magnetized in one direction in the axial direction, or the magnetic field detecting element is attached in the radial direction with a gap around the permanent magnet disk, the position of the magnetic field generating element and the magnetic field detecting element are shifted and the magnetic field is If the detection element is installed in a curved portion of the magnetic field, the waveform of the output signal is likely to be disturbed. For example, as shown in FIG. The detection signal is distorted due to the difference between the magnetic field and the magnetic field. For this reason, it is necessary to accurately maintain the relative position between the magnetic field detecting element and the magnetic field generator, and the production is troublesome.

The present invention eliminates the above-mentioned drawbacks, allows the magnetic field detecting element to be always installed within a range parallel to the magnetic field, facilitates attachment of the magnetic field detecting element to the magnetic field generator, and enables downsizing. I will provide a.

[0007]

For this purpose, a magnetic body is formed in a cylindrical shape, and a uniform magnetic field is generated in the gap in one direction perpendicular to the central axis. A plurality of magnetic field detecting elements are arranged in the inside of the magnetic field detecting element at a predetermined angular phase difference, and the magnetic field generator and the magnetic field detecting element are relatively rotated. The magnet can be formed of a cylindrical permanent magnet, and is magnetized so as to generate a magnetic field in one direction as a whole. In addition, in order to improve the magnetic field strength generated in the gap of the magnetic field, a cylindrical soft magnetic material constituting a magnetic path may be adhered to the magnetic field on the outer periphery of the magnetic field, or may be arranged via a small gap. it can.

It is also possible to gradually change the magnetization direction at the circumferential position of the magnet to form a unidirectional magnetic field in the central gap. In order to gradually change the magnetization direction at the circumferential position, a plurality of trapezoidal permanent magnet blocks having different magnetization directions are sequentially shifted in magnetization direction and combined in the circumferential direction to form a cylinder, or a rubber magnet is used. The magnetized body whose magnetization direction is gradually changed can be formed by separating one portion of the cylindrical body magnetized in the direction, and inverting the cylindrical body so that the inner peripheral surface is on the outside, and returning the cylindrical body to the cylindrical shape.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 and 2, reference numeral 1 denotes a rotating shaft, 2 denotes a cylindrical magnet, and a permanent magnet (arrow indicated by an arrow) is magnetized so as to generate a uniform magnetic field B in a direction perpendicular to the center axis. Indicates the direction of magnetization. Reference numeral 3 denotes a support plate to which the magnetizing member 2 is attached, which is fixed to the rotating shaft 1. 4 is the magnetizing body 2
The gaps 5a, 5b, 5c, and 5d on the inner side of the cylinder are magnetic field detecting elements, and are arranged in the gap 4 with a phase difference of 90 degrees from each other. Reference numeral 6 denotes a mounting seat for the magnetic field detecting element, and reference numeral 7 denotes a support plate for the mounting seat 6. In addition, a power supply circuit to the magnetic field detection element, a wiring of an output signal, a signal processing circuit, and the like are omitted.

A magnetic field B is provided in one uniform direction perpendicular to the axis by magnetizing the magnetizing body 2 in two poles, and forms a uniform parallel magnetic field in the entire space in the air gap 4. . Therefore, even if the magnetic field detecting elements 5a, 5b, 5c, and 5d deviate from the center of the gap 4, one magnetic field is applied to each magnetic field detecting element.
A high-quality sine-wave output signal having a waveform of exactly the same period can be obtained, and it is not necessary to accurately maintain a position related to the magnet 2 and high assembly accuracy is not required, so that the production becomes easy.

3 and 4 show another embodiment. 1 and 2 are denoted by the same reference numerals, and an annularly punched silicon steel plate is formed on the outer periphery of the magnetic body 2 in the embodiment shown in FIG. 2 according to the axial length of the magnetic body 2. A magnetic circuit is formed by providing a stacked cylindrical magnetic body 10. In the embodiment shown in FIGS. 1 and 2, the magnetic flux φ passes through the space outside the magnetic body 2, so that the magnetic resistance is large and the magnetic field strength in the air gap 4 is small. The magnetic circuit is formed to reduce the magnetic resistance of the magnetic flux φ and increase the magnetic field strength in the air gap 4.

The permanent magnet forming the magnet 2 may be a rare earth sintered magnet, a ferrite sintered magnet, a rare earth bonded magnet, a ferrite bonded magnet, an alnico magnet, a ferrite rubber magnet, or the like. The magnetic body 10 may be formed by winding silicon steel in the circumferential direction of the magnetic body 2, or may be formed of pure iron, mild steel, an amorphous alloy, or the like in a cylindrical shape. Further, it may be attached to the magnet body 2 in close contact with the magnetic body 2 or may be attached to a support plate 7 as shown in the embodiment of FIG.

FIG. 6 shows a different example of the magnetic field generator 2. The magnetization directions on the left and right sides of the cylindrical magnetic body are sequentially symmetrically arranged at circumferential positions (in the figure, eight magnetization directions are respectively shown). (Shown), and is constituted by a permanent magnet which gradually changes to form a magnetic field B in one direction in the central gap 4.

FIG. 7 shows a magnetic field generator having another configuration, which has eight trapezoidal permanent magnet blocks 8 each having a different magnetization direction, and a block whose magnetization direction is perpendicular to a parallel side. Blocks whose magnetization directions are sequentially shifted by 90 degrees are joined together in the circumferential direction so that they are adjacent to each other,
A unidirectional magnetic field B is formed in the central gap 4. The number of permanent magnet blocks is not limited to eight, and the configuration of such a magnet is disclosed in Japanese Patent Laid-Open No. 9-90.
It is the same as that shown in No. 009.

FIG. 8 shows still another magnetizing body 2 and its manufacturing process. First, as shown in FIG. 8 (a), the entire rubber magnet formed in a required cylindrical shape is radially moved by 2 mm. The magnetized body 2 is formed by polar magnetization. Magnet 2 made of this rubber magnet
Can be used as it is in the same manner as in FIG. 2 and the like, but if one arbitrary portion is cut in the radial direction by the cutting portion 9 and separated by the cutting portion 9 as shown in FIG. Since it is extended and the outside is compressed, the relationship of the magnetization direction to the cut portion 9 changes sequentially. Further, both ends are opened in the direction of arrow 9a as shown in FIG. 8 (c), and then continuously turned and curved in the direction of arrow 9b so that the inner peripheral surface becomes the outer periphery, via the state of FIG. 8 (d). Further, when bending in the direction of the arrow 9c and joining the cut portions 9 at both ends to return to a cylindrical shape as shown in FIG. 8 (e), the magnetization direction at the circumferential position gradually changes, and one direction is formed in the central gap 4. Magnet 2 with magnetic field B
Is formed. The cutting portion 9 may be cut not in the radial direction but in an oblique direction.

[0016]

(Example 1) Outer diameter 40 mm, inner diameter 20 mm,
A cylindrical Nd—Fe—B-based bonded magnet formed with a length of 10 mm in the axial direction (Br = 7.3 kG, (BH) max = 11)
A permanent magnet made of MGOe) is magnetized with two poles in the radial direction to generate a uniform magnetic field in one direction perpendicular to the central axis to produce a magnetized body 2 having an outer diameter of 60 m on its outer periphery.
When a magnetic circuit 10 was formed by laminating a silicon steel plate having a diameter of 40 mm and an inner diameter of 40 mm to form a magnetic circuit, and the magnetic field in the gap 4 was measured, a uniform magnetic field strength of 0.25T was confirmed. As shown in FIG. 4, the magnetic field detecting elements 5a, 5b, 5
c, 5d (Hall element) are arranged,
As a result of detecting the change of the magnetic field due to the rotation angle by rotating together with 0, a very high quality sine wave signal was obtained as shown in FIG.

(Example 2) Outer diameter 40 mm, inner diameter 20 m
m, Nd-Fe-B-based sintered magnet having an axial length of 10 mm (Br = 11.9 kG, (BH) max = 35 MGO
As a result of performing an experiment in the same manner as in Example 1 using e), the magnetic field intensity in the air gap was 0.44 T, and a very good quality sine wave signal was obtained with the same change in the magnetic field.

(Example 3) Outer diameter 42 mm, inner diameter 10 m
m, cylindrical ferrite rubber magnet having a length of 10 mm in the axial direction (Br = 1.5 kG, (BH) max = 0.5MGO
e) Two-pole magnetization was performed in the radial direction to form a magnetized body 2. A ring-shaped pure iron having an outer diameter of 13 mm and an inner diameter of 12 mm was arranged on the outer periphery of the magnetized body 2 and the magnetic field in the gap was measured.
As a result of detecting a change in the magnetic field by arranging a magnetoresistive element (MR element) in the gap 4, a good sine wave signal was obtained.

(Embodiment 4) Nd-Fe-
B-based sintered magnet (Br = 11.7 kG, iHc = 22 kO)
e, (BH) max = 32MGOe), eight permanent magnet blocks are configured as shown in FIG.
A cylindrical magnet 2 having a diameter of 24 mm, an inner diameter of 24 mm and a length of 72 mm was prepared. A magnetic field of 1.1 T is generated in the gap of the cylindrical magnet, and a uniform magnetic field B having a variation of 0.1% or less is formed within a diameter of 15 mm. (Hall element) and magnetizing element 2
As a result of detecting the change in the magnetic field due to the rotation angle by rotating
An extremely high quality sine wave signal was obtained.

Example 5 A ferrite rubber magnet having a width of 10 mm, a thickness of 1 mm, and a length of 35 mm (Br = 1.5 kg,
iHe = 2.4 kGe, (BH) max = 0.5 MGO
e) The magnetizing body 2 formed into a cylindrical shape having an outer diameter of 12 mm and an inner diameter of 10 mm using the method shown in FIG.
It was created. The magnetic field B generated in the gap 4 of the magnet 2
Was measured, a value of 0.024T was obtained, and the uniformity was the same as in Example 4. FIG. 10 shows a characteristic diagram of a result obtained by measuring a detection signal depending on a rotation angle by using the magnetic field generating element 2 and a Gauss meter using a Hall element in the gap 4 as a magnetic field detecting element. As is clear from this characteristic diagram, a very good sine wave signal is obtained even if the magnetic field detecting element is eccentric, and the amplitude intensity and waveform of the sine wave signal hardly change even if the magnetic field detecting element is further eccentric, and high assembly is achieved. Obviously, no accuracy is required.

For comparison, as shown in FIG. 11, a magnetic drum 25 in which a ferrite rubber magnet of the same material is formed into a ring shape and multi-polarized on the outer peripheral surface, and a magnetic sensor opposed to the outer peripheral surface The encoder provided with 26 was created. As a result of a test performed with this encoder, in the characteristic diagram of the rotation angle and the detection signal, the detection signal fluctuates due to slight eccentricity of the magnetic field detection element as shown in FIG.

(Embodiment 6)
As a result of configuring an incremental magnetic encoder of 2048P / R which employs an MR element as a magnetic field detecting element and has an arithmetic processing circuit including a multiplication circuit, the outer diameter is 15m.
m and a length of 25 mm, which is approximately half the size of a magnetic drum encoder having a multi-polarized magnetic drum on the outer periphery and a magnetoresistive element disposed outside thereof as shown in FIG. As a result, good results were obtained as in Example 5 with respect to the influence of the eccentricity of the assembly accuracy.

[0023]

As described above, according to the present invention, the magnet is formed in a cylindrical shape, and a magnetic field is generated in one direction which is uniform in the direction perpendicular to the center axis of the magnet. Since a plurality of magnetic field detecting elements are arranged with an angular phase difference, there is no need to accurately arrange the magnetic field detecting element in the center of the air gap. Are housed inside the magnetizing body, and can be formed in a small size, and effects such as the inertia of the rotating portion can be reduced.

By forming a magnetic circuit with a soft magnetic material surrounding the outer periphery of the magnet, the strength of the magnetic field in the air gap of the magnet can be increased and the detection accuracy can be improved. In addition, by gradually changing the magnetization direction of the magnetized body at the circumferential position and using a cylindrical body that forms a magnetic field in one direction in the center gap, the magnetic field in the gap is strengthened and the directionality is maintained well. be able to. Further, by inverting the cylindrical rubber magnet magnetized in one direction, there is an effect that a magnetized body whose magnetization direction gradually changes can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a main part of an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a side sectional view showing a main part of another embodiment.

FIG. 4 is a cross-sectional view at the center of FIG. 3;

FIG. 5 is a side sectional view showing a main part of another embodiment.

FIG. 6 is a front view showing a different example of the magnetic body.

FIG. 7 is a front view showing an example of another magnetizing body.

FIG. 8 is an explanatory view showing still another magnetizing body and a manufacturing process thereof.

FIG. 9 is a characteristic curve diagram of an output signal in the example of the encoder according to the present invention.

FIG. 10 is a characteristic curve diagram of an output signal in another embodiment.

FIG. 11 is a perspective view schematically showing an example of a magnetic drum type.

12 is a characteristic curve diagram of an output signal in the case of eccentricity in the example of FIG.

FIG. 13 is a perspective view showing a conventional example.

FIG. 14 is an explanatory diagram showing an eccentric state in a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 rotating shaft 2 magnetizing body 3 support plate 4 gap 5a, 5b, 5c, 5d magnetic field detecting element 6 mounting seat 8 permanent magnet block 9 cutting section 10 magnetic body

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazunari Matsuzaki 2-1 Kurosaki Castle Stone, Yawatanishi-ku, Kitakyushu-shi, Fukuoka F-term (reference) 2F077 AA47 CC02 JJ02 JJ07 JJ23 NN17 NN24 PP05 QQ02 VV01 VV11

Claims (6)

[Claims] 1. A magnetic encoder for providing a magnetic field detecting element in a magnetic field generated by a magnetic body and processing an output signal from the magnetic field detecting element due to a relative rotation between the magnetic body and the magnetic field detecting element. A magnetic field, wherein a magnetic field in one direction is generated in a direction perpendicular to the center axis of the magnetic field, and a magnetic field detecting element is arranged with a predetermined angular phase difference in a gap of the magnet. Encoder. 2. The magnetic encoder according to claim 1, wherein the magnetizing body is formed of a cylindrical permanent magnet and is magnetized in one direction. 3. The magnetic encoder according to claim 1, further comprising a cylindrical magnetic body forming a magnetic circuit on an outer periphery of said magnetic body. 4. The magnetic encoder according to claim 1, wherein the magnetizing body forms a magnetic field in one direction in a gap by gradually changing a magnetization direction at a circumferential position. 5. A magnetic body in which a plurality of trapezoidal permanent magnet blocks are combined in a cylindrical shape with the short sides inside and the magnetization directions are sequentially changed to form a unidirectional magnetic field in a central gap. The magnetic encoder according to claim 4, wherein 6. The magnetizing member magnetizes a cylindrical rubber magnet so as to generate a magnetic field in one direction, and then cuts one portion and inverts the inner peripheral surface to the outside to form a cylindrical shape. 5. The magnetic encoder according to claim 4, wherein the return causes the magnetization direction to gradually change to form a magnetic field in one direction.