JP2000213957A - Magnetic encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic encoder which can make magnetic measurement and cope with high frequencies in a high magnetic field, has little output change caused by a temperature change, and receives no effect of stains or the like. SOLUTION: This magnetic encoder is provided with magnetic recording mediums and a magnetic detector having magnetic detecting elements 1 detecting the magnetic patterns of the magnetic recording mediums. Each magnetic detecting element 1 is provided with a giant magnetic resistance material thin film 3 formed on a substrate 2 directly or via an insulating layer and a first electrode thin film 4 connected to one end section of it. A second electrode thin film 6 connected to the other end section of the giant magnetic resistance material thin film 3 is provided on the giant magnetic resistance material thin film 3 and the first electrode thin film 4 via an insulating layer 5.

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 having a small size, high sensitivity, high output and high resolution by using a magnetic detecting element having a thin film of a giant magnetoresistive material formed on a substrate. The present invention relates to a magnetic encoder having:

[0002]

2. Description of the Related Art Conventional encoders are roughly classified into a magnetic type and an optical type. 2. Description of the Related Art Conventionally, in a magnetic encoder, a magnetoresistive sensor (Japanese Patent Application Laid-Open No. SHO 59-5959) has been used as a detecting element of a magnetic pattern that periodically appears as a position signal moves with the movement of a magnetic recording medium having a plurality of magnetic poles magnetized at equal intervals. -1472
No. 13, JP-A-2-195284, JP-A-7-139
No. 966) and a Hall sensor, and a magnetoresistive element such as NiF
e alloy (JP-A-2-195284) or the like is used.

On the other hand, an optical encoder uses a laser beam as a light source and an optical sensor as a detector. A detector is provided with a diffraction grating between the light source and the detector, and the diffracted light is provided behind the diffraction grating. There is a device that observes the position and detects a precise position by a change in the intensity of the diffracted light.

[0004]

However, in an encoder using a Hall sensor as a magnetic detecting element,
Since the Hall element has a four-terminal structure, miniaturization and miniaturization are difficult, and there is a problem that high resolution in the order of μm cannot be obtained. In addition, since a semiconductor is used, there is a problem that responsiveness to a change in a high-frequency magnetic field cannot be obtained and the device cannot be used at high temperatures.

On the other hand, a sensor using a magnetoresistive sensor can be reduced in size, but has no response to a high magnetic field of several tens of Oe or more, making measurement difficult when a magnetic field is applied from the outside. There's a problem. Therefore, when used in an environment that is affected by a high magnetic field, such as use as a rotation sensor for a motor having a high magnetic field of several hundred Oe or more, or use on a steel material side, a magnetic shield is required. There is a problem that becomes large.

[0006] In the optical encoder, although high resolution on the order of μm can be obtained, the detection sensitivity decreases when dirt such as dust and oil mist adheres.
There is a problem that measurement becomes difficult in an environment such as synchrotron radiation. Furthermore, since precision equipment such as a laser light source and a diffraction grating is used for detection, there is a problem that the apparatus itself is large and expensive.

Accordingly, it is an object of the present invention to make a magnetic detection element finer and smaller, to be able to perform magnetic measurement in a high magnetic field, and to support high frequency, to have a small output change due to a temperature change, and to be influenced by dirt and the like. It is an object of the present invention to provide an inexpensive high-sensitivity, high-output, high-resolution magnetic encoder which is not affected by the above.

[0008]

In order to achieve the above object, according to the present invention, a magnetic recording medium having a plurality of magnetic poles magnetized at equal intervals and a magnetic pattern of the magnetic recording medium are detected. A magnetic detector having a magnetic detection element,
A magnetic encoder in which the magnetic detecting element is disposed so as to be relatively movable within a range in which the magnetic field of the magnetic recording medium acts, wherein the magnetic detecting element uses a thin film of a giant magnetoresistive material. A magnetic encoder comprising a giant magnetoresistive element is provided. According to a preferred aspect, the magnetic detector includes a magnetic detecting element including a giant magnetoresistive material thin film formed on a substrate and two electrode thin films connected to both ends of the magnetic detecting element. It has means for applying a current or a constant voltage, and means for detecting a current or a voltage generated by the magnetic detecting element.

Preferably, the magnetic detecting element has a structure in which noise caused by an induced electromotive force from a lead wire due to a sudden change in a magnetic field is reduced and only a magnetic field in a sensor portion is detected. Connected to both ends of the thin film
The wiring structure is such that the sensor leads are stacked and formed with an insulating layer interposed therebetween. For example, a thin film of a giant magnetoresistive material formed directly on a substrate or via an insulating layer and a first electrode thin film (sensor lead) connected to one end thereof, a thin film of these giant magnetoresistive materials, A laminated film comprising a second electrode thin film (sensor lead) formed on the first electrode thin film via an insulating layer and connected to the other end of the giant magnetoresistive material thin film, or The second electrode thin film formed directly on the substrate or via the insulating layer, the thin film of the giant magnetoresistive material formed on the second electrode thin film via the insulating layer, and the first electrode The structure is a laminated film composed of a thin film.

[0010] It is preferable to use a magnetic detector in which two or more magnetic detecting elements as described above are formed at an interval of 1/2 of the distance between magnetic poles in the magnetic recording medium. With this configuration, a differential signal of two or more giant magnetoresistive elements can be detected as a rotation angle or a movement amount, and the influence of an external magnetic field such as an excitation coil driven to rotate is reduced. be able to. Such two or more giant magnetoresistive elements can be formed on the same substrate. For example, an insulating layer is laminated so as to cover a pair of elongated first electrode thin films formed in parallel and separated on a substrate and a thin film of a giant magnetoresistive material connected to each of the thin first electrode thin films, and the insulating layer is formed on the insulating layer. Further, a pair of elongated second electrode thin films are formed so as to be connected in parallel to the ends of the giant magnetoresistive material.

The giant magnetoresistive material includes a structure in which magnetic particles are dispersed in an electrically conductive matrix, preferably an electrically conductive matrix made of at least one element of Ag, Cu, Au, and Pt. Fe, Co,
Magnetic particles comprising at least one element of Ni,
It is preferable to use a magnetic particle dispersion type (granular type) giant magnetoresistive material having a structure dispersed at an atomic ratio of preferably 5 to 55%. Further, it is preferable that the plurality of magnetic poles magnetized at equal intervals of the magnetic recording medium are made of a magnet having a high coercive force.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the magnetic encoder of the present invention has a magnetic sensing element composed of a giant magnetoresistive element using a thin film of a giant magnetoresistive material (referred to as a material having a giant magnetoresistive effect). Therefore, it is possible to miniaturize and downsize the magnetic sensing element, measure the magnetic field in a high magnetic field, and support high frequency,
Further, it is possible to provide a high-sensitivity, high-output, high-resolution magnetic encoder in which an output change due to a temperature change is small and is not affected by dirt or the like. The giant magnetoresistive material is made of a magnetic particle-dispersed giant magnetoresistive material, an artificial lattice giant magnetoresistive material or a super giant magnetoresistive material, and can read an alternating magnetic field of at least 5 kHz or more as a signal.

Here, Giant Magnetoresis
tance, GMR) effect E. AE Berkowitz et al., Phys. Rev. Lett. 68 (1992),
3745 pages and Jay. queue. JQ Xiao et al., Ph
ys. Rev. Lett. 68 (1992), p. 3749. N. M. Baibich et al., Phys. Rev. Lett. 61 (1988),
P. 2473 or S. S. Pee. Parkin (SSP Parki
n) et al., Appl. Phys. Lett. 58 (1991), p. 2710, refers to an artificial lattice type giant magnetoresistance effect. The magnetoresistance effect of these materials, as described in Kataoka et al., “Materia,” Vol. 33, No. 2, 1994, p. 165, shows the magnetization and conduction of magnetic materials (precipitated particles or multilayer films). Is attributed to spin-dependent scattering of electrons responsible for Therefore, since Co, Ni, Fe or an alloy thereof is used as the magnetic material, there is no change in magnetization up to at least 300 ° C., and a large magnetoresistance effect can be obtained.

[0014] Colossal magnetoresistance (Colossal Magneto)
resistance, CMR) is La (AE)
MnO ₃ (AE: alkaline earth metal Ca, Sr or B
a) an oxide having a Mn-based perovskite structure shown in a), which has been studied since the 1950s (Land)
olt-Bornstein New Series III / 4a (1970), III / 12a (197
In recent years, attention has been paid to a material exhibiting a change in electrical resistance from an insulator to a metal due to a magnetic field at a low temperature (Materia, Vol. 35, No. 11, 1996, 121).
See page 7).

The magnetic particle-dispersed giant magnetoresistive material comprises:
In a conductive material such as Ag, Cu, or Au or a non-magnetic (paramagnetic, diamagnetic) material, the maximum major axis is about 5 to 500 n.
m, made of a material in which ferromagnetic particles such as Fe, Co, and Ni are dispersed. The artificial lattice type giant magnetoresistance material is composed of a nonmagnetic (paramagnetic, diamagnetic) material and a ferromagnetic material, For example, it is made of a material in which about 1 to 10 nm are periodically laminated. On the other hand, examples of the giant magnetoresistive material include, for example, a general formula: Ln _1-y AE _y MnO _3-z (where Ln is at least one element among rare earth elements, and AE is Ca, S
r and Ba are at least one element, and y and z are each represented by an atomic ratio of 0.2 ≦ y ≦ 0.4, −0.1 ≦ z ≦
0.3) as a main component (95 at% or more of the material has the above composition). Particularly preferred is a material in which the AE element is Sr, and La is mainly used as the rare earth element.

As a characteristic of these materials, the magnetic resistance changes even in a magnetic field of several kOe or more. Therefore, even if a sensor is provided in the motor, the magnetic field change accompanying the rotation of the rotor can be measured. In addition, since these materials require only two wirings, which are half of the Hall element, the wirings are simple and the miniaturization is easy. In other words, the magnetic encoder has requirements for “high magnetic field characteristics”, “high frequency characteristics”, “magnetic field resistance”, and “miniaturization” required for the magnetic encoder.

Of the three materials, it is preferable to use a magnetic particle-dispersed giant magnetoresistive material for use in a magnetic encoder. This is because, in the case of the giant magnetoresistance effect, a high temperature (700 to
This is because a heat treatment is required at 900 ° C.), which makes the manufacturing process difficult, and because the electric resistance is as high as several kΩ, it is difficult to conduct electricity.

The magnetic particle-dispersed giant magnetoresistive material preferably has a general formula: NM _100-X TM _X (where NM is Ag,
At least one element of Cu, Au, and Pt; TM is at least one element of Fe, Co, and Ni;
x is atomic%, 5 ≦ x ≦ 55, preferably 10 ≦ x ≦ 3
It has the composition shown in 5). In the magnetic particle-dispersed giant magnetoresistance material having the composition represented by the above general formula, the nonmagnetic material NM is up to 20 at%, preferably 10 at%.
One or more other elements such as Al, Ti, Pd, and Rh may be contained within the following ranges. These elements lower the magnetoresistance effect and lower the sensitivity, but on the other hand, Al, T
i reduces the temperature dependence of the magnetoresistance effect, while P
d, Pt, and Rh have the effect of increasing the magnetoresistance effect of the entire sensor including the wiring by increasing the electrical resistance. In addition, the ferromagnetic material TM is composed of C in addition to Fe, Co, and Ni.
Elements such as r and Mn can be contained in a range of up to 5 at%. In particular, Cr and Mn reduce the magnetoresistance effect, but can prevent coarsening of the magnetic particles and increase heat resistance.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a magnetic encoder according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a plan view showing an embodiment of a magnetic detecting element 1 of the magnetic detector according to the present invention.
Is a sectional view taken along the line II-II. 1 and 2,
Reference numeral 3 denotes a thin film (sensor element) made of a magnetic particle-dispersed giant magnetoresistance material as described above. As clearly shown in FIGS. 1 and 2, an elongated copper first electrode thin film 4 is formed on a substrate 2.
A thin film 3 of the above giant magnetoresistive material is disposed at the tip of. The giant magnetoresistive material thin film 3 and the first electrode thin film 4
On top of this, an insulating layer 5 made of Al ₂ O ₃ is laminated so as to cover them. However, the rear end of the first electrode thin film 4 is exposed for lead wire connection. On the insulating layer 5,
An elongated copper second electrode thin film 6 is formed at a position matching the first electrode thin film 4 so as to be connected to the giant magnetoresistive material thin film 3.

The shape of the giant magnetoresistive material thin film 3 is suitably a rectangle having a length of 5 mm or less and a width of 0.5 mm or less. The electrode thin films 4 and 6 can be made of a conductive material such as Al, Cu, Cr, Ta, or Mo, or an alloy thereof. Among them, Cu is preferable. Further, as the insulating layer 5, Al ₂ O ₃ , SiO ₂ , MgO or the like can be used. The thickness of the insulating layer 5 is 0.5 nm or more,
1,000 nm or less is suitable, preferably 10 nm
As described above, the thickness is preferably 100 nm or less. According to another preferred embodiment, a substrate having a soft magnetic material such as a silicon steel plate, a permalloy, or an amorphous alloy of CoFeSiB attached to or behind the substrate 2 is used. By converging the magnetic flux by using the soft magnetic material in this way, the sensitivity is further improved, and the restriction on the installation location of the detector is alleviated.

FIG. 3 shows a schematic basic configuration of an example in which the magnetic detecting element of the present invention is applied to a rotary encoder. In FIG. 3, reference numeral 10 denotes a rotary drive source 1 such as a motor.
3 is a rotating drum-shaped magnetic recording medium attached to the rotating shaft 12 of the third embodiment.
The S poles 11 are fixed so as to appear at equal intervals. It is preferable to use a strong magnet (a rare earth magnet such as SmCo and NdFeB) as the magnetic pole. Magnetic sensing element 1a
Is set so as to face the magnetic recording medium 10 and N
The power supply 17 is provided with a constant current or a constant voltage via a lead wire 14 within a range where a magnetic field generated by the S pole acts. The magnetic sensing element 1a shown in FIG. 3 has a structure in which lower ends of upper and lower electrode thin films laminated on a substrate via an insulating layer are extended in a forked shape. 1 and FIG.

In such a configuration, the magnetic recording medium 1
When 0 is rotated, the magnetic field applied to the magnetic detection element 1a changes periodically in accordance with the magnetized magnetic pattern. This change is detected as a change in magnetic resistance by the magnetic detection element 1a, and an output signal of a current change or a voltage change is obtained. This output signal is amplified by the amplifier circuit 15 and sent to the control system 16. In this manner, the rotation angle, the movement amount, and the rotation speed of the magnetic recording medium 10 can be detected.

FIG. 3 shows a schematic basic configuration in the case where the magnetic detecting element of the present invention is applied to a rotary encoder. It goes without saying that the configuration of the encoder itself can employ various conventionally known forms. For example, JP-A-59-147213 and JP-A-2-1952 described above.
No. 84, the absolute phase on the surface of the magnetic recording medium in a manner as described in JP-A-7-139966 and the like.
An incremental phase can be formed.

FIG. 4 shows a schematic basic configuration of an example in which the magnetic detecting element of the present invention is applied to a linear encoder. In this linear encoder, NS poles 11a are formed in a predetermined pattern on the surface, and an elongated plate-shaped magnetic recording medium 10a fixed to a moving object 18 is used. This is the same as the case of the rotary encoder. Also in this case, the magnetic detecting element 1a is arranged near the magnetic recording medium 10a so as to face the magnetic recording medium 10a.

The following is an example in which the effects of the present invention have been specifically confirmed. The magnetic particle-dispersed giant magnetoresistance material is Ag
It was manufactured using a composite target in which Co chips or Ni _0.66 Co _0.18 Fe _0.16 alloy chips were uniformly arranged on a target or a Cu target. The film forming conditions and the heat treatment conditions are as follows. Film forming method: RF magnetron sputtering Substrate: Si wafer Substrate temperature: 100 ° C. Atmosphere: Ar 0.6 Pa Sputter power: 100 W Thin film composition: Ag ₇₀ Co ₃₀ , Ag ₇₅ (Ni _0.66 Co _0.18 F
e _0.16 ) ₂₅ film thickness: 10 to 500 nm Heat treatment: temperature: 200 ° C. time: 0.5 hour Atmosphere: in vacuum Magnetoresistance effect at a film thickness of 10 nm: magnetoresistance ratio of about 10% at a magnetic field of 10 kOe ( MR ratio). The magnetoresistance ratio is a value obtained by the following equation. MR ratio (%) = (R (0) -R (H)) / R (0) × 1
00 R (0): Electric resistance when no magnetic field is applied R (H): Electric resistance when magnetic field is applied

According to the above method, a thin film of a giant magnetoresistive material is formed on a glass substrate in a rectangular shape having a length of 0.5 mm and a width of 0.1 mm, and the thickness is adjusted from 10 nm to 500 nm. Was changed from 2Ω to 50Ω, and a Cu electrode or an electrode was prepared using a silver paste to prepare a magnetic sensing element. A magnet plate (surface magnetic field of 500 Oe) having a thickness of about 1 mm is stacked so that NS poles are alternately arranged.
A magnetic recording medium having a 1 kΩ magnet interposed every other sheet is used as a magnetic recording medium. By moving the magnetic recording medium in opposition to the magnetic detecting element, not only a change in the position of the magnetic recording medium but also an absolute position can be detected. It was confirmed that detection was possible even under temperature conditions of ° C.

[0027]

As described above, the magnetic encoder of the present invention uses a giant magnetoresistive material as a magnetic detecting element, particularly a giant magnetoresistive material dispersed with magnetic particles, so that it can be used at high temperatures or in dusty environments. It has become possible to manufacture a small, high-resolution magnetic encoder that can be used at low cost. In addition, magnetic detection is possible even in a high magnetic field environment,
In addition, by using a strong magnet as a source of the detection magnetic field, it is hard to be affected by an external magnetic field (noise), and a high reliability can be obtained without the need for a magnetic shield. further,
High-frequency magnetic field can be measured, and sensitivity does not decrease even if dirt such as dust adheres. Therefore, it can be advantageously used as various rotary encoders and linear encoders for heaters, engines and the like.

[Brief description of the drawings]

FIG. 1 is a plan view showing one embodiment of a magnetic sensing element of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a schematic basic configuration diagram showing an embodiment in which the magnetic detection element of the present invention is applied to a rotary encoder.

FIG. 4 is a schematic basic configuration diagram showing an embodiment in which the magnetic detection element of the present invention is applied to a linear encoder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1a Magnetic detection element 2 Substrate 3 Giant magnetoresistive material thin film 4 First electrode thin film 5 Insulating layer 6 Second electrode thin film 10, 10a Magnetic recording medium 11, 11a NS pole 12 Rotation axis 13 Rotary drive source (motor) 15 Amplification Circuit 16 Control system 17 Power supply

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yunori Miura 4-26-3, Moiwadai, Taishiro-ku, Sendai-shi, Miyagi F-term (reference) 2F063 AA01 AA35 AA50 BC02 BC05 BD11 BD16 CA09 CA34 CA40 DA19 EA02 EA03 GA55 LA11 LA30 2F077 AA25 AA41 NN04 NN05 NN17 NN24 PP14 TT87 2G017 AA01 AB01 AB05 AD21 AD53 AD55 AD63 AD65

Claims (8)

[Claims] A magnetic recording medium having a plurality of magnetic poles magnetized at equal intervals; and a magnetic detector having a magnetic detecting element for detecting a magnetic pattern of the magnetic recording medium. A magnetic encoder, which is disposed so as to be relatively movable within a range in which a magnetic field of a magnetic recording medium acts, wherein the magnetic detecting element is a giant magnetoresistive element using a thin film of a giant magnetoresistive material. A magnetic encoder characterized in that: 2. The magnetic detector according to claim 1, wherein the magnetic detector includes a thin film of a giant magnetoresistive material formed on a substrate and two electrode thin films connected to both ends of the thin film. The magnetic encoder according to claim 1, further comprising: means for applying a constant voltage; and means for detecting a current or a voltage generated by the magnetic detection element. 3. The thin film of a giant magnetoresistive material formed directly or via an insulating layer on a substrate and a first electrode thin film connected to one end of the giant magnetoresistive element. A laminated film formed of a resistive material thin film and a second electrode thin film formed on the first electrode thin film via an insulating layer, and connected to the other end of the giant magnetoresistive material thin film, or A second electrode thin film formed directly on the substrate or via an insulating layer, and a thin film of the giant magnetoresistive material formed on the second electrode thin film via an insulating layer and the first The magnetic encoder according to claim 2, wherein the magnetic encoder is a laminated film including an electrode thin film. 4. The magnetic device according to claim 1, wherein two or more magnetic detectors are formed at intervals of a half of a distance between magnetic poles of the magnetic recording medium. Type encoder. 5. The magnetic encoder according to claim 1, wherein the giant magnetoresistive material has a structure in which magnetic particles are dispersed in an electrically conductive matrix. 6. The giant magnetoresistive material is Ag, Cu,
6. The magnetic type according to claim 5, wherein the magnetic type has a structure in which magnetic particles composed of at least one element of Fe, Co, and Ni are dispersed in an electrically conductive matrix composed of at least one element of Au and Pt. Encoder. 7. The magnetic encoder according to claim 6, wherein the content ratio of the magnetic particles in the giant magnetoresistive material is 5 to 55% in atomic ratio. 8. The magnetic recording medium according to claim 1, wherein the plurality of magnetic poles magnetized at equal intervals are magnets having a high coercive force.
A magnetic encoder according to any one of claims 1 to 7.