JPH11213540A - Magnetic type encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic type encoder wherein an output signal is corrected in a waveform distortion irrespective of a gap length between a magnetic detector and a magnetic member, the output is also improved in SN ratio and usable without trouble, and conditions for manufacture become also simple. SOLUTION: This magnetic type encoder is made up by forming plural linear magnetic domains 4 of a rare earth magnetic material which are arranged on the side of main surface 3a of a substrate 3 at a constant set spacing λin the moving direction as a magnetic scale and also magnetized in a specific direction, and thereby forming a magnetic member 1 to be mounted on the side of a detected body, and tilting a magnetic resistance element 6 on a magnetic detecting body 2 moving relatively to the magnetic member 1 and the magnetic domains 4 by a specific angle θ (0 deg.<θ<90 deg.) with respect to the width direction b of the magnetic member 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic encoder which magnetically detects the rotational momentum of a rotary motor or the like or the linear momentum of a linear motor or the like and outputs an electric signal.

[0002]

2. Description of the Related Art As is well known, encoders are broadly classified into optical ones and magnetic ones depending on the method of detecting an object to be detected. Compared to optical encoders, magnetic encoders are less affected by detection sensitivity even when dust or dirt adheres to the detection area, consume less power, and have light-emitting and light-receiving elements. It is advantageous in that it can be made compact without the need to perform it and has high mechanical strength.

A magnetic encoder generally has a magnetic member attached to an object to be detected, for example, an N pole and an S pole are alternately formed on the main surface side in the movement direction of the object to be detected.
It is composed of a so-called multi-pole magnet, and the alternating magnetism when the multi-pole magnet rotates or moves linearly is
The detection is performed by a magnetic detection body having a magnetic detection element such as a magnetic element or a magnetic resistance element.

A multi-pole magnet is manufactured by, for example, using a linear encoder as shown in FIG.
A magnet head 102 is disposed opposite to the main surface of the magnetic head 101, and the magnetic member 101 is linearly moved at a constant speed in the longitudinal direction, and an alternating current is supplied to the coil 103 of the magnetized head 102 in synchronization with the movement. And thereby the magnetic member 1
In general, a large number of N poles and S poles are alternately magnetized on the main surface of No. 01 to form the multipole magnet 100.

In a magnetic encoder (linear encoder) using the multipole magnet 100, as shown in FIG. 16, the multipole magnet 100 is a long base material 10 to be detected.
4, a magnetic detector 105 facing the main surface of the multipole magnet 100 with a small gap G is provided so as to be capable of relative movement.

The north and south poles of the multipole magnet 100 have a constant width λ / 2 in the direction of movement (the direction of arrow a).
(Λ is a set interval of N pole or S pole)
4 is configured as a magnetic scale across. Magnetic detector 1
Numeral 05 has, for example, two magnetoresistive paths 106A and 106B constituting the magnetoresistive element 106 as shown in FIG. 17, and each of the magnetoresistive paths 106A and 106B is a direction orthogonal to the direction of movement, that is, a multipole magnet. 100 has a length L extending along the width direction (direction of arrow b).

The two magnetoresistive paths 106A, 1
06B are connected in series with each other, both ends of the series connection body are connected to a power source E, and two magnetoresistive paths 106A, 106A,
The connection point m of 6B is connected to the output terminal Q of the midpoint potential Vo.

In this magnetic encoder, if the magnetic detection body 105 and the detection body 104 are relatively displaced in the direction of movement, the magnetism is detected from the multipole magnet 100 by the respective magnetic resistance paths 106A and 106B. From the magnetic detector 105, a detection output corresponding to the momentum of the detection target 104 is converted into an electric signal and output.

[0009]

The output signal from such a magnetic encoder is used as a control signal for various devices, but it has a sine waveform as shown in FIG. Is desirable. However, the magnetic detector 105
G between the magnet and the multipole magnet 100 is, for example, 0.2
The sine wave is hard to be obtained unless the gap G is set with extremely high precision because the sine wave is arranged within a minute range of about mm or less.

In the region where the gap G is small, the multipole magnet 100
The strength of the magnetism received by the magnetoresistive paths 106A and 106B from the side becomes excessive, and the output signal becomes a distorted waveform as shown in FIG. 18B, and cannot be used as a control signal. In the region where the gap G is small, the multipole magnet 10
The magnetic field of the horizontal component locally present at zero is detected by the magnetoresistive paths 106A and 106B, which also causes the waveform to be distorted.

On the other hand, in a region where the gap G is large, the intensity of the magnetism received by the magnetoresistive paths 106A and 106B from the multipole magnet 100 becomes too small, and the output signal becomes insufficient as shown in FIG. As a result, the S / N ratio becomes extremely poor. In this case, unless an output signal is corrected by introducing an amplifier, a filter, or the like, it is still difficult to use the control signal.

Japanese Patent Publication No. 6-17800 discloses that the angle between the longitudinal direction of the magnetoresistive path constituting the magnetoresistive element and the main surface of the multi-pole magnet at the closest part of the magnetoresistive element is set to 90 ° or less. Specifically, it has been proposed to suppress the intensity of an output signal so that waveform distortion does not occur. Also, Japanese Patent Application Laid-Open No. 5-24
JP-A-8887 discloses that a magnetoresistive element is tilted by a specific angle relative to a line connecting N pole or S pole within one cycle of a magnetic scale in a multipole magnet, so that a peak portion of an output signal and It has been proposed to suppress the wave at the valley to reduce the waveform distortion of the output signal.

According to these proposed methods, it is possible to improve the waveform distortion of the output signal in a region where the gap between the magnetic detector and the main surface of the multipole magnet is considerably small. However, since the multipolar magnet attached to the object to be detected is generally made of a ferrite-based magnetic member, the output signal decreases in the region where the gap is relatively large, and the S / S of the output signal decreases.
It is inevitable that the deterioration of the N ratio becomes remarkable.

In order to suppress the decrease in the output strength, it is conceivable that the multipolar magnet is made of a rare-earth magnetic material of Sm.Co type or Na.Fe type. However, in this case, there is a problem that power is insufficient when the multipole magnet is formed with the magnetized head, and it is difficult to magnetize a fine magnetic scale that can be used for a magnetic encoder.

According to the present invention, in view of such circumstances, the output signal of the magnetic detector does not suffer from waveform distortion or output shortage, and can be used as it is as a control signal, and the gap between the magnetic detector and the magnetic member can be used. The purpose of the present invention is to provide a magnetic encoder which has a wider range of choices and which helps to simplify the manufacturing conditions.

[0016]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the above-mentioned objects, and as a result, as a magnetic member attached to the object to be detected, a substrate and a main surface of the substrate have been used instead of a multipolar magnet. A single-pole linear magnetic domain provided at a constant set interval in the direction of movement on the side, and this linear magnetic domain is made of a rare-earth magnetic material, while the magnetoresistive element in the magnetic detector is used. Constant angle θ with respect to the linear domain
By inclining (0 ° <θ <90 °), it is possible to suppress the waveform distortion of the output signal in a region where the gap between the magnetic detector and the magnetic member is small, and to magnetize a single pole on the surface. In the process, there is no need to alternate the coil current for magnetization, and magnetization in a strong one-way magnetic field is possible, so that the magnetic domain is formed in a state where the rare earth magnetic material is fully magnetized. As a result, it was found that the S / N ratio of the output signal in the region where the gap was large could be improved, and the present invention was completed.

That is, the present invention comprises a magnetic member attached to the object to be detected, and a magnetic detector disposed at a position capable of moving relative to the magnetic member. In a magnetic encoder for detecting momentum magnetically, the magnetic member is provided as a magnetic scale on a main surface side of the substrate at a predetermined interval in the direction of motion and magnetized in a predetermined direction. Each magnetic domain is composed of a rare-earth magnetic material, and is formed linearly so as to have a predetermined width in the direction of movement, and the magnetic detector is a main surface of the magnetic member. And a magnetoresistive element comprising a magnetoresistive path extending in a direction intersecting with the direction of movement, wherein the magnetic domains and the magnetoresistive element are set to be inclined at a constant angle relative to the width direction of the magnetic member. Specially And magnetic to diene - da (claim 1
To 4).

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing the appearance of a magnetic member used in a magnetic linear encoder according to the present invention together with a magnetic detector, and FIG. 2 is an overall configuration diagram showing an outline of the magnetic linear encoder. In both figures, reference numeral 1 denotes a magnetic member attached to an object to be detected (not shown) which linearly moves in the direction of arrow a, and 2 denotes a magnetic member which is disposed facing the main surface of the magnetic member 1 with a gap G therebetween. 1 is a magnetic detector set to be able to move relative to 1.

The magnetic member 1 comprises an elongated substrate 3 along the direction of movement, and a plurality of magnetic domains 4 as magnetic scales formed on the main surface 3a side. The substrate 3 is formed in a plate shape from a ferromagnetic material or the like, and a plurality of holes 5 which are inclined at a predetermined angle θ with respect to the width direction of the substrate 3 and substantially traverse the main surface 3 a thereof in the movement direction ( They are formed at a constant set interval (pitch) λ in the longitudinal direction of the substrate). A rare-earth magnetic material such as a Cm-Co-based magnetic material or a Na-Fe-based magnetic material is fitted and fixed in each of the holes 5 so as to be flush with the main surface 3a of the substrate 3. Is formed. The magnetic domains 4 are magnetized along a direction perpendicular to the main surface 3a of the substrate 3.

In the magnetic member 1, the width W of each magnetic domain 4 in the movement direction is set to, for example, (1/2) .times..lambda., Whereby the planar shape of each magnetic domain 4 has a constant width W. 3
It is linear along the width direction. In this example, each magnetic domain 4 is formed to have a width substantially traversing the substrate 3 in the width direction, but may be linear so as to completely traverse the substrate 3 in the width direction.

The magnetic detector 2 is disposed so that the detection surface 2a is parallel to the main surface 3a of the substrate 3, and a magnetoresistive element 6 is provided on the detection surface 2a side. The magnetoresistive element 6 is composed of two magnetoresistive paths 6A and 6B arranged side by side at a predetermined interval in the movement direction (direction in which the magnetic domains 4 are arranged). These two magnetoresistive paths 6A, 6B extend in a direction orthogonal to the direction of movement in the same plane, that is, along the width direction of the substrate 3 (the direction of arrow b).

As shown in FIG. 3, the two magnetoresistive paths 6A and 6B are connected in series. Both ends Pa and Pb of this series connection are connected to a power source E, and one end Pb is grounded. is there. An output terminal Q of the midpoint potential Vo is connected to a connection point m between the two magnetoresistive paths 6A and 6B. The number of the magnetic resistance paths 6A and 6b constituting the magnetic resistance element 6 is not limited to two, but can be arbitrarily increased or decreased.

In this configuration, each magnetic domain 4 is inclined at a fixed angle θ with respect to the width direction of the substrate 3 so that each magnetic domain 4 and the magnetoresistive element 6 are relatively fixed in the width direction. The state is inclined by the angle θ. Tilt angle θ
Is selected and set within the range of 0 ° <θ <90 °. In particular, when the length of the magnetoresistive path 6A (6B) is L,
It is preferable to set a relationship that satisfies 0 <θ ≦ tan ⁻¹ (λ / 4L). That is, the projected component 1 (L × tan θ) in the direction of motion at the length L of the magnetoresistive path 6A (6B) is λ / 4 or less, that is, L × tan θ ≦ λ / 4, It is preferable to set the inclination angle θ so as to satisfy θ ≦ tan ⁻¹ (λ / 4L).

In the magnetic linear encoder configured as described above, the magnetic member 1 linearly moves in the same direction as the detected object moves in the direction of arrow a, and the magnetic detector 2 moves with respect to the magnetic member 1. Relatively linear motion. As a result, the two magnetoresistive paths 6A and 6B constituting the magnetoresistive element 6 cross each magnetic domain 4 of the magnetic member 1 in a direction intersecting the magnetization direction,
The magnetism in the magnetic domain 4 is detected as a horizontal magnetization component. As shown in FIG. 2, the detection output f is sequentially sent to an arithmetic unit 7 such as a CPU. The arithmetic unit 7 receives the output f and determines the number of times of magnetic detection of the magnetic domain 4 per unit time. Calculated and data g of the linear momentum of the object to be detected
Is sent out.

Here, each magnetic domain 4 and the magnetoresistive path 6A (6
B) means that the magnetic resistance path 6A (6B) is in a linear motion with the boundary between the magnetic domain 4 and the non-magnetic domain part because the magnetic resistance path 6A (6B) is relatively inclined with respect to the width direction of the magnetic member 1. The crossing area increases by L × tan θ in the direction of motion. Therefore, in a region where the gap G between the magnetic detector 2 and the main surface of the magnetic member 1 is small, the magnetic resistance path 6A (6
B) reduces the amount of detecting the magnetic field of the horizontal component locally present in the magnetic domain 4. As a result, the waveform distortion of the output signal can be reduced.

Each magnetic domain 4 and the magnetic resistance path 6A (6B)
Is relatively inclined by a constant angle θ, the amount of detection of the horizontal component of the magnetic field detected by the magnetoresistive path 6A (6B) decreases, but the magnetic domain 4 is formed of a rare-earth magnetic material. Therefore, the output intensity (amplitude value) of the output signal does not significantly decrease. Moreover, the magnetic member 1 and the magnetic detector 2
The S / N ratio of the output signal is improved in a region where the gap G between the output signal is large. As a result, it can be used as it is as a control signal for various devices. Further, while suppressing the waveform distortion in the region where the gap G is small, the output intensity is also ensured in the region where the gap G is large, so that the selection range of the gap G is widened and the manufacturing conditions are greatly eased.

In the above embodiment, each magnetic domain 4 is inclined at a fixed angle θ with respect to the width direction of the magnetic member 1,
Although the length direction of the magnetoresistive paths 6A (6B) has been described as being coincident with the direction perpendicular to the direction of motion (the width direction of the magnetic member 1), the width direction of each magnetic domain 4 is conversely perpendicular to the direction of motion. The length direction of the magnetoresistive path 6A (6B) may be inclined at a fixed angle θ with respect to the width direction of the magnetic member 1 as shown in FIG. Also in this case, the same effect as described above can be exerted.

Further, in addition to the above-described embodiment, it is possible to adopt another embodiment in which both the magnetic domain 4 and the magnetoresistive path 6A (6B) are inclined at different angles. Further, it goes without saying that the above configuration of the present invention can be applied not only to the magnetic linear encoder but also to a magnetic rotary encoder using a circular magnetic member.

[0029]

EXAMPLES Examples of the present invention will be described below in more detail.

Example 1 A magnetic member 1 (magnetic material: Na—Fe—B) in which each magnetic domain 4 was inclined at an angle θ with respect to the width direction of the magnetic member 1 was used. The inclination angle θ was 2 °. The set interval λ of the magnetic domain 4 is 0.375 mm, and the length L of the magnetic resistance paths 6A and 6B is 1.5.
mm. That is, in FIG. 3, 1 = L × tan θ
= 0.052 mm. In this example, the gap G between the magnetic member 1 and the magnetic detector 2 was changed within the range of 0 to 0.200 mm, and the magnetic detection waveforms of the magnetic resistance paths 6A and 6B were measured for each gap G.

The measurement results are shown in FIGS.
The results were as shown in (D) to (F) of FIG. 6 and (G) to (I) of FIG. As is clear from these figures, the gap G has a wide range of 0 to 0.150 mm, has a small waveform distortion, and has good characteristics with sufficient output intensity. It can be seen that an appropriate output signal can be obtained in a wide range of the gap G with 2.

Example 2 A magnetic member 1 in which each magnetic domain 4 was inclined at a fixed angle θ with respect to the width direction of the magnetic member 1 was used. The inclination angle θ is 3.6 °. In this case, in FIG. 3, 1 = L × tan θ = 0.094 mm
(= Λ / 4). Other configurations were the same as those of the first embodiment. In this example, the gap G between the magnetic member 1 and the magnetic detector 2 was set to 0.05 mm, and the magnetic detection waveforms by the magnetic resistance paths 6A and 6B were measured.

The measurement results are as shown in FIG. As is apparent from FIG.
It can be seen that a signal with little waveform distortion is obtained although the output intensity is slightly lower than that of. Also,
Even in the case where the gap G is changed, 0 to 0
It has been found that up to 0.150 mm, the waveform distortion is small and the output intensity is sufficiently satisfactory.

Comparative Example 1 A multi-pole magnet composed of a ferrite-based magnetic material was used.
The north and south poles were inclined by a fixed angle θ with respect to the width direction of the magnet. The inclination angle θ was 2 °. Other configurations are the same as in Embodiment 1, λ = 0.375 mm, L = 1.5
mm, L × tan θ = 0.052 mm. In this example, the gap G between the magnetic member and the magnetic detector is set to 0 to 0.200.
mm, the magnetic resistance path 6
The magnetic detection waveforms of A and 6B were measured.

The measurement results are shown in FIGS. 9A to 9C,
(D) to (F) in FIG. 10 and (G) to (I) in FIG.
The results were as shown in FIG. From these results, when the inclination angle θ is set, the waveform distortion in the region where the gap G is small is improved, but the gap G is set to 0.100 mm or more because the multipolar magnet made of the ferrite magnetic material is used. It can be seen that when this happens, the output intensity drops significantly and the S / N ratio deteriorates significantly.

Comparative Example 2 A multi-pole magnet made of a ferrite-based magnetic material was used.
The inclination angles θ of the N pole and the S pole were set to 0 °. Other configurations were the same as in the first embodiment. In this example, the gap G between the magnetic member and the magnetic sensing element was changed from 0 to 0.200 mm, and the magnetic detection waveform by the magnetoresistive paths 6A and 6B was measured for each gap G.

The measurement results are shown in FIGS.
(C), (D) to (F) of FIG. 13 and (G) of FIG.
To (I). From these results, in this example, since the inclination angle θ is 0 degree, the waveform distortion becomes extremely large in a region where the gap G is small, that is, G = 0 to 0.050 mm. That is, the gap G at which good characteristics with small waveform distortion are obtained is 0.075 to 0.100 mm.
It can be seen that the production conditions are considerably strict.

[0038]

As described above, according to the present invention, as the magnetic member attached to the object to be detected, a plurality of single-pole linear magnetic domains are provided on the main surface side of the substrate at a predetermined set interval in the direction of movement. And the magnetic domain and the magnetoresistive element on the side of the magnetic detector are inclined at a constant angle relative to the width direction of the magnetic member, so that the output in the region where the gap between the magnetic detector and the magnetic member is small is used. The waveform distortion of the signal can be corrected.

Further, since the magnetic domains are made of a rare earth magnetic material, the output intensity in the region where the interval is large is sufficiently secured, and the S / N ratio can be improved. As a result, it can be effectively used as a control signal without performing complicated electrical processing and processing, and the setting range of the gap can be widened, so that it is practically easy to use.

[Brief description of the drawings]

FIG. 1 is an external view showing a magnetic member used in a magnetic linear encoder of the present invention together with a magnetic detector.

FIG. 2 is an overall configuration diagram showing an outline of the linear encoder.

FIG. 3 is a plan view showing an arrangement relationship between a magnetic domain inclined at a fixed angle with respect to a width direction of a magnetic member and a magnetoresistive element.

FIG. 4 is a plan view showing an arrangement relationship between a magnetic resistance element and a magnetic domain that are inclined at a fixed angle with respect to a width direction of a magnetic member.

5A and 5B show measurement results of a magnetic detection output in Example 1; FIG. 5A shows a gap G = 0 mm between a magnetic member and a magnetic detection body;
(B) G = 0.025 mm, (C) G = 0.050 mm
It is a characteristic diagram at the time of.

FIG. 6 shows a measurement result similar to the above in Example 1, (D)
Is G = 0.075 mm, (E) is G = 0.100 mm,
(F) is a characteristic diagram when G = 0.125 mm.

FIG. 7 shows a measurement result similar to the above in Example 1, (G)
Is G = 0.150 mm, (H) is G = 0.175 mm,
(I) is a characteristic diagram when G = 0.200 mm.

FIG. 8 is a characteristic diagram showing a measurement result of a magnetic detection output in Example 2.

9A and 9B show measurement results of a magnetic detection output in Comparative Example 1. FIG. 9A shows a gap G = 0 mm between a magnetic member and a magnetic detector.
(B) G = 0.025 mm, (C) G = 0.050 mm
It is a characteristic diagram at the time of.

FIG. 10 shows the same measurement results as described above of Comparative Example 1,
(D): G = 0.075 mm, (E): 0.100 m
m and (F) are characteristic diagrams when G = 0.125 mm.

FIG. 11 shows the same measurement results as described above of Comparative Example 1,
(G): G = 0.150 mm, (H): G = 0.175 m
m and (I) are characteristic diagrams when G = 0.200 mm.

12A and 12B show measurement results of a magnetic detection output in Comparative Example 2, and FIG. 12A shows a gap G = 0 m between a magnetic member and a magnetic detection body.
m, (B) G = 0.025 mm, (C) G = 0.05
It is a characteristic diagram at the time of 0 mm.

FIG. 13 shows the same measurement results as described above of Comparative Example 2,
(D) G = 0.075 mm, (E) G = 0.100 m
m and (F) are characteristic diagrams when G = 0.125 mm.

FIG. 14 shows the same measurement results as described above of Comparative Example 2,
(G): G = 0.150 mm, (H): G = 0.175 m
m and (I) are characteristic diagrams when G = 0.200 mm.

FIG. 15 is a perspective view showing a magnetizing means of a magnetic member of a conventional general magnetic encoder.

16 is a perspective view showing an outline of a general magnetic encoder using a magnetic member obtained by the magnetizing means of FIG.

17 is a plan view showing an arrangement relationship between a magnetic member and a magnetoresistive element in the magnetic encoder of FIG.

18 is a diagram showing a waveform state of an output signal due to a difference in a gap between a magnetic detector and a magnetic member in the magnetic encoder of FIG.

[Explanation of symbols]

 Reference Signs List 1 magnetic member 2 magnetic detector 3 substrate 3a main surface of substrate 4 magnetic domain (magnetic scale) 6 magnetic resistance element 6A, 6B magnetic resistance path a movement direction b width direction L length of magnetic resistance path λ magnetic domain setting interval θ inclination angle

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Fumiki Asai 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation

Claims (4)

[Claims] A magnetic member attached to a detection object side; and a magnetic detection body disposed at a position capable of relatively moving with respect to the magnetic member. In the magnetic encoder described above, the magnetic member comprises a substrate and a plurality of single poles provided on the main surface side of the substrate as magnetic graduations at fixed intervals in the direction of movement and magnetized in a constant direction. Each magnetic domain is composed of a rare earth magnetic material, and is formed linearly so as to have a predetermined width in the direction of movement, and the magnetic detector is parallel to the main surface of the magnetic member and The magnetic domain and the magnetoresistive element having a magnetoresistive path extending in a direction intersecting the direction of movement, wherein the magnetic domains and the magnetoresistive element are set to be inclined at a constant angle relative to the width direction of the magnetic member. Characteristic magnetic encoder -Da. 2. The relative inclination angle (θ) between the magnetic domain and the magnetoresistive element is 0 <θ ≦ tan ⁻¹ (λ / 4L) (λ is the set interval of the magnetic domain, and L is the length of the magnetoresistive path. 2. The magnetic encoder according to claim 1, wherein the relationship is satisfied. 3. The magnetic encoder according to claim 1, wherein the magnetic domains are arranged such that a width direction thereof coincides with a direction orthogonal to a direction of movement. 4. The magnetic encoder according to claim 1, wherein the magnetoresistive path is disposed such that its length direction coincides with a direction orthogonal to the direction of movement.