JPH01189516A - Magnetic resistance sensor for magnetic encoder - Google Patents

Abstract

PURPOSE:To obtain an averaged detection signal even when a gap is locally varied, by a method wherein the pattern consisting of a detection part and a connection part formed by a magnetic resistor element is allowed to oppose to the magnetized pattern of the end surface of a shaft. CONSTITUTION:A magnetic resistance sensor 14 is constituted by forming MR elements 15a on a glass substrate 16 by vapor deposition and forming an insulating film 18 thereon while further forming MR elements 15b on the insulating film 18 by vapor deposition and forming a protective film 20 thereon. The elements 15a, 15b are formed over the entire periphery of the circumference of a circle in a comb shape to constitute a large number of detection parts S, S,... extending radially and a large number of circular arc connection parts C, C,... and opposed to the magnetized pattern M magnetically recorded on one end part 12a of a shaft 12. Herein, when the shaft 12 is rotated and the magnetized pattern M is relatively displaced with respect to the detection parts S, S,..., the sine and cosine wave detection signals corresponding to displacement quantity are respectively outputted from the elements 15a, 15b and the quantity and direction of rotation of the shaft 12 can be calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a magnetoresistive sensor applied to, for example, a magnetic encoder that detects the amount of rotation of each part of a drive system of an industrial robot or NO device.

"Prior Art" Conventionally, a magnetic encoder for detecting the amount of rotation has a configuration as shown in FIGS. 5 and 6.

The magnetic encoder A shown in FIG. 5 includes a shaft 1 whose end (not shown) is connected to a detection target (for example, a motor shaft, etc.), and a magnetized pattern on one end surface at a predetermined pitch. It is composed of a disc-shaped magnetic recording medium 2 on which M is magnetically recorded, and a magnetoresistive sensor 3 which is placed opposite to the magnetic recording medium 2 with a predetermined gap G therebetween. The magnetoresistive sensor 3 is made of a magnetoresistive element (Magneto R13sistive) whose specific resistance changes depending on the strength of the magnetic field when placed in a magnetic field.
It is constructed by depositing elements (abbreviated as MR elements) in a predetermined pattern on a glass substrate.

In addition, the magnetic encoder B shown in FIG. 6 has a cylindrical magnetic recording medium 4 on which magnetization patterns M are magnetically recorded at a predetermined pitch on the outer peripheral surface of the magnetic recording medium 4 instead of the disk-shaped magnetic recording medium 2 described above. 1, and a magnetoresistive sensor 3 is arranged at a predetermined gap G from the outer peripheral surface of the magnetic recording medium 4.

Each of these magnetic encoders A and B detects the amount of rotation of the magnetic recording medium 2 (4) by reading changes in the magnetic field of the magnetized pattern M on the magnetic recording medium 2 (4) using the magnetoresistive sensor 3. That is, the amount of rotation of the detection target connected to the shaft l is detected.

[Problem that the invention attempts to solve] By the way, the conventional magnetic encoder A mentioned above.

In B, the structure is such that the magnetized pattern M on the magnetic recording medium 2 (4) is read by a single magnetoresistive sensor 3. When vibration in the radial direction or vibration in the thrust direction occurs, the gap G between the recording medium 2 (4) and the magnetoresistive sensor 3 changes, which causes the magnetic field of the magnetization pattern M that acts on the magnetoresistive sensor 3 to change. fluctuates in the period of one rotation of the shaft l. Therefore, high precision is required for the support mechanism of the shaft l, and when manufacturing the magnetic recording medium 2,
High precision is also required when attaching the shaft to the shaft l, which has been a factor hindering reductions in manufacturing costs.

Therefore, a magnetic encoder C as shown in FIGS.
-E is known. The magnetic encoder C shown in FIG. 7 has a structure in which magnetized patterns M are magnetically recorded on both sides of the magnetic recording medium 2 and these are read by a pair of magnetoresistive sensors 3, and the magnetic encoder C shown in FIG. A magnetic encoder E shown in FIG. It has a structure in which the magnetized pattern M is read by a pair of magnetoresistive sensors 3, 3. According to these magnetic encoders C-E, the detection signals output from the pair of magnetoresistive sensors 3゜3 are added together and averaged, thereby detecting the difference between the recording medium 2 (4) and the magnetoresistive sensor 3. Fluctuations in the detection signal due to local variations in the gap G are corrected. However, since the magnetic encoder C-E described above also has a structure in which the pair of magnetoresistive sensors 3, 3 are arranged separately, each magnetoresistive sensor 3, 3 is connected to the magnetic recording medium 2 (4).
There was a problem in that the adjustment work when arranging the two oppositely with each other with a predetermined gap G between them was complicated.

This invention was made in view of the above-mentioned circumstances, and is a magnetic encoder that not only can minimize the fluctuations in the detection signal due to the fluctuation of the gap, but also can easily perform the adjustment work of the gap. The purpose of the present invention is to provide a magnetoresistive sensor for use.

"Means for Solving the Problems" The present invention provides a magnetic recording medium that is arranged opposite to one end surface of a rotatably supported shaft with a predetermined gap therebetween, and that is magnetically recorded at a predetermined pitch along the circumference of the one end surface. In a magnetoresistive sensor for a magnetic encoder that detects a magnetic pattern using a magnetoresistive element whose specific resistance changes depending on the strength of the magnetic field, the magnetoresistive element detects a plurality of detection sections extending radially, and each of the detection sections. The present invention is characterized in that a pattern consisting of arc-shaped connecting portions connecting the end portions is formed, and the pattern is formed over the entire circumference on the circumference facing the magnetized pattern.

"Operation" Since a pattern of magnetoresistive elements is formed all around the circumference facing the magnetized pattern magnetically recorded on one end surface of the shaft, the gap between it and the one end surface of the shaft is localized. Even if the magnetoresistive sensor fluctuates, it is possible to obtain a detection signal in which these fluctuations are averaged, thereby reducing the fluctuation of the detection signal.Also, since the structure uses a single magnetoresistive sensor, it is possible to reduce the gap. Adjustment work also becomes easier.

"Embodiments" Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1(A) is a sectional view showing an enlarged part of a magnetoresistive sensor 14 according to an embodiment of the present invention, and FIG. 1(B) is a front view showing the overall configuration of the magnetoresistive sensor 14. . Note that FIG. 1(b) shows only the patterns of the first MR element 15a and the second MR element 15b deposited on the glass substrate 16.

In these figures, a glass substrate 16 such as boric acid glass is used.
A first MR element 15a is deposited thereon, and a
An insulating film 18 such as a silicon oxide film is formed, and a second MR element 15b is deposited on this insulating film I8. Further, the insulating film 1 on which the second MR element 15b is deposited
8, a PSG film (phospho-5ilicat
e-glass; phosphorus-doped silicon oxide film)
A protective film 20 such as the above is formed. first and second M
R elements 15a and I5b are made of a ferromagnetic material such as Ni-Fe (iron), Ni-C0 (-1-cobalt), or In5b (indium antimonide), GaAs (gallium arsenide), etc. It is made up of semiconductors. These first and second MR elements 1
5a and 15b are both formed in a comb shape over the entire circumference facing a magnetized pattern M magnetically recorded on one end 12a of the shaft 12, which will be described later, and have a plurality of detection parts extending radially. S, S, . . . and arc-shaped connecting portions C, C, .
・It is composed of. In this case, each detection unit S, S,
... are arranged at the same interval as the pitch λ of the magnetized pattern M (see FIG. 3), and the first MR element 15a is
It is arranged shifted by λ/4 with respect to the second MR element 15b. As a result, the first and second MR elements 1
5a and 15b are insulated from each other via the insulating film 18, and have a phase of λ/4 (90°) with respect to each pitch of the magnetized pattern M on the one end surface 12a of the shaft 12.
They are arranged in a superimposed manner so that they are shifted.

Next, FIG. 2 is a partially cutaway perspective view showing a configuration example of a magnetic encoder to which the above-described magnetoresistive sensor 14 is applied. In this figure, IO is a casing, 12 is rotatably supported by the casing IO, and one end surface 1
A magnetized pattern Mh<magnetically recorded shaft is formed at a predetermined pitch along the circumference of 2a. And this shaft I
The magnetoresistive sensor 14 is disposed opposite to one end surface 12a of the magnetoresistive sensor 2 with a predetermined gap G therebetween. Note that FIG. 2 shows a state in which a part of the casing 10 is cut away and the magnetoresistive sensor 14 is removed from the casing 10.

The casing IO is formed into a rectangular parallelepiped shape by injecting synthetic resin material around the shaft 12, and has an inner diameter slightly larger than the outer diameter of the shaft 12, and has an inner diameter slightly larger than the outer diameter of the shaft 12. A through hole 10a into which the casing 12 is rotatably fitted and supported is formed along the length direction of the casing IO. An annular projection 15 that engages with the recess 12b of the shaft 12 is integrally formed on the inner peripheral surface of one end of the through hole 10a over the entire circumference.

This casing IO is manufactured as follows.

First, a thin film of a predetermined thickness is formed in advance on the outer peripheral surface of the shaft 12 using a mold release agent or the like, and then the casing IO is injection molded. Thereafter, by removing the thin film by heat treatment or chemical treatment, the outer peripheral surface of the shaft 12 and the through hole 10a are removed.
A slight gap is formed between the inner peripheral surface of the This results in
A shaft 12 is rotatably supported by the casing 10.

The shaft 12 is made of a magnetic material with excellent workability and high strength, such as iron-chromium-cobalt-based or iron-cobalt-manganese-based material, and is formed into a cylindrical shape. An annular recess 12b is formed around the entire circumference by cutting or the like. This recess j2
When the casing 10 is formed, the annular protrusion 15 of the casing 10 engages with the annular protrusion 15 of the casing 10, thereby restricting the relative movement of the shaft 12 in the length direction with respect to the casing 10. . Also, this shaft 12
One end surface 12a is magnetized with a sine wave of wavelength λ on the circumference centered on its axis, so that magnetization with the same wavelength λ is generated along the periphery of one end surface 12a as shown in FIG. Magnetized patterns M are magnetically recorded at pitches.

In the above configuration, when the shaft 12 rotates and the magnetized pattern M magnetically recorded on the one end surface 12a is displaced relative to each detection section S, S, . . . of the magnetoresistive sensor 14, this A detection signal of a sine wave and a cosine wave corresponding to the amount of displacement and having a phase shift of 90° is sent to the first MR element 15a.
and the second MR element 15b, and the rotation amount and rotation direction of the shaft 12 are determined based on these detection signals.

According to the embodiment described above, for example, the inclination of the shaft 12, the deformation of the one end surface 12a, or the deflection in the radial direction, the thrust direction, or the direction occurs, and the magnetoresistive sensor 1
4 and one end surface 12a of the shaft 12, the magnetoresistive sensor 14 obtains a detection signal ° in which these fluctuations are averaged, thereby reducing fluctuations in the detection signal. Furthermore, since the structure is such that a single magnetoresistive sensor 14 is disposed, the adjustment work of the gap G becomes easy. In addition, since the first MR element 15a and the second MR element 15b are formed on the circumference facing the magnetized pattern M over the entire circumference, the area facing the magnetized pattern M becomes large, and as a result, the S/N ratio of the detection signal can be made large.

Next, other configuration examples of the magnetoresistive sensor (4) will be explained.

Figure 4 (a) shows six detection units S, located at four equal locations on the circumference.
This shows an example in which the first MR element 25a and the second MR element 25b, which are provided together, are arranged separately on the outer circumferential side and the inner circumferential side so that they do not overlap with each other. M of
The detection section S of the R element 25a is shifted from the detection section S of the second MR element 25b by nλ+λ/4 (n=0.1.2...an integer). Also, Figure 4 (b)
is the detection part S over the entire circumference.

A first MR element 26a and a second MR element 26a provided with S,...
An example is shown in which the elements 26b are arranged in a nested manner so as not to overlap with each other. These are all examples of a layered structure, and each MR element 25a, 25 is placed on a glass substrate 16.
b, , 26a, 26b are deposited, and a protective film 20 (
(path shown). In addition, the configuration shown in FIG. 4(c) is also considered (in the figure, n and m are 0, 1,
2. ...is an integer).

Note that the shapes and dimensions of each component shown in the above-described embodiments are merely examples, and can be variously changed according to design requirements.

"Effects of the Invention" As explained above, according to the present invention, a plurality of radially extending detection sections and an arc-shaped connection section connecting the ends of each of the detection sections are connected by a magnetoresistive element. Since the pattern was formed all around the circumference facing the magnetized pattern magnetically recorded on one end surface of the shaft, the gap between the pattern and the one end surface of the shaft was localized. Even if there is a fluctuation in the magnetoresistive sensor, a detection signal is obtained in which this fluctuation is averaged.This allows the fluctuation of the detection signal to be minimized.Also, since the structure uses a single magnetoresistive sensor, there is no gap. This has the effect that the adjustment work for the drop can be easily performed.

[Brief explanation of the drawing]

FIGS. 1(A) and 1(B) are a partial sectional view and a front view showing the configuration of a magnetoresistive sensor according to an embodiment of the present invention,
FIG. 2 is a partially cutaway perspective view showing the structure of a magnetic encoder to which the magnetoresistive sensor according to the same embodiment is applied, and FIG. 3 shows the structure of the magnetization pattern M magnetically recorded on the end surface of the shaft 12 of the same magnetic encoder. 4(a), (b) and (c) are front views showing other configuration examples of the magnetoresistive sensor, and FIGS. 5(a), 5(a) and 9(b) to 9(a) and (b) are a front view and a side view showing the configuration of a conventional magnetic encoder. 12... Shaft, 12a... One end surface, M... Magnetized pattern, G... Gap, 14... Magnetoresistive sensor, 15 a, 25 a, 26 a=--=first MR
Element, 15b, 25b, 26b... Second MR
Element, 16...Glass substrate, S...Detection section, C...Connection section. Applicant: Yamaha Sigma Co., Ltd.

Claims (1)

[Claims] A magnetized pattern that is arranged opposite to one end surface of a rotatably supported shaft across a predetermined gap and magnetically recorded at a predetermined pitch along the periphery of the one end surface has a specific resistance. In a magnetoresistive sensor for a magnetic encoder that detects using a magnetoresistive element that changes depending on the strength of a magnetic field, the magnetoresistive element connects a plurality of radially extending detection sections and ends of each of the detection sections. 1. A magnetoresistive sensor for a magnetic encoder, characterized in that a pattern consisting of an arcuate connecting portion is formed, and the pattern is formed all around a circumference facing the magnetized pattern.