JPH065172B2 - Magnetoresistive sensor for magnetic encoder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of application" The present invention is applied to, for example, a magnetic rotary encoder and the like, and the specific resistance of magnetic information recorded on a magnetic recording medium changes according to the strength of a magnetic field. The present invention relates to a magnetic resistance sensor for a magnetic encoder, which detects a relative displacement of a magnetic recording medium by detecting the magnetic resistance element.

"Prior Art" As is well known, a magnetic rotary encoder is composed of a disk-shaped magnetic recording medium fixed to a shaft, and a magnetoresistive sensor that is opposed to the magnetic recording medium with a predetermined gap. However, these are generally configured as shown in FIGS. 3 (A) to 3 (D).

In these figures, 1 is a magnetic recording medium, and 2 is a magnetoresistive sensor. By magnetically recording a sinusoidal wave having a wavelength λ along a circular orbit facing the magnetoresistive sensor 2, magnetic information (magnetization pattern 1a, 1a, ... ) Is recorded. on the other hand,
The magnetoresistive sensor 2 is composed of a glass substrate 3 and a magnetoresistive element 4 deposited on the glass substrate 3. The magnetoresistive element 4 is composed of an element material that produces a phenomenon in which the specific resistance changes according to the strength of the magnetic field when placed in a magnetic field, so-called magnetoresistive effect. Then, when the magnetic recording medium 1 is relatively displaced in the direction of the arrow M shown in the figure, the magnetization pattern recorded on the magnetic recording medium 1 is read, whereby the rotation of the shaft that rotates together with the magnetic recording medium 1 is rotated. The amount is to be detected.

In this case, the magnetoresistive element 4 connects the detection units S _{1 to} S ₁₆ extending in the direction orthogonal to the displacement direction M of the magnetic recording medium 1 and the detection units S _{1 to} S ₁₆ respectively, and It is composed of connecting portions C _{1 to} C ₁₆ extending in parallel with M and is formed in a comb shape. Here, the relative positional relationship between the detection units S _{1 to} S ₁₆ will be described. The detection units S _{1 to} S ₄ are separated from each other by λ, and the detection unit S ₅ is separated from the detection unit S ₄ by λ / 2. The detectors S _{5 to} S ₈ are separated from each other by λ, and the detector S ₉ detects the detector S ₈
And the detectors S _{9 to} S ₁₂ are separated from each other by λ, the detector S ₁₃ is separated from the detector S ₁₂ by λ / 2, and the detector S ₉ is separated from the detector S _{12.
13 to} S ₁₆ are separated by λ. In addition, the detection unit S ₁
End of the terminal is connected to the terminal T ₁ , the connecting portion C ₄ is connected to the terminal T ₂ , and the connecting portion C ₈
And C ₉ are connected to the terminal T ₃ , the connecting portion C ₁₃ is connected to the terminal T ₄ , and the end portion of the detecting portion S ₁₆ is connected to the terminal T ₅ .

Then, when the terminal T ₃ is grounded and + VCC is applied to the terminals T ₁ and T ₅ , the terminal T _{2 is} moved along with the displacement of the magnetic recording medium 1.
The sine wave detection signal SinOUT is output from
The cosine wave detection signal CosOUT is output from the terminal T ₄ . That is, the detection signal SinOUT detected by the sine wave detecting magnetoresistive element A including the detection units S _{1 to} S ₈ , the connection units S _{1 to} S ₈ and the connection units C _{1 to} C ₈ is detected by the detection units S _{9 to} S 8. ₁₆
And the detection signal CosOUT detected by the cosine wave detecting magnetoresistive element B including the connecting portions C _{9 to} C ₁₆ and the phase is λ.
It is / 4 (90 °) offset. As a result, the displacement direction and displacement amount of the magnetic recording medium 1 are obtained based on these detection signals SinOUT and CosOUT.

[Problems to be Solved by the Invention] By the way, the distance between the center of the sine wave detecting magnetic resistance element A and the center of the cosine wave detecting magnetic resistance element B of the magnetic resistance sensor 2 is about 1 mm (about 8λ). Minutes) before and after. Although the distance between the centers is very small, even with such a small distance, there is a high probability that physical distortion occurs on the magnetic recording medium 1 side, which is the reason why highly accurate position detection cannot be performed. It was. The reason will be described in detail below.

First, as shown in FIG. 3C, the sine wave detecting magnetic resistance element A and the cosine wave detecting magnetic resistance element B are provided in series along the displacement direction M of the magnetic recording medium 1. Here, assuming that the magnetic recording medium 1 is moving to the right in the figure, a portion of the magnetic recording medium 1 facing the sine wave detecting magnetoresistive element A is for detecting a cosine wave after a predetermined time has elapsed. It faces the magnetoresistive element B. By the way, if there is distortion in the portion of the magnetic recording medium 1 facing the sine wave detecting magnetic resistance element A, the detection signal SinOU
Swelling occurs at T. Next, after a lapse of a predetermined time, when the portion moves to the right and faces the cosine wave detecting magnetoresistive element B, the detection signal CosOUT is undulated. As described above, when the magnetic recording medium 1 is distorted, undulations occur in both the detection signals SinOUT and CosOUT, but the undulations occur at different timings in both detection signals, and in the worst case, FIG. As shown in (b) and (c), undulations of opposite phase are superimposed on the detection signals SinOUT and CosOUT.

Now, the magnetoresistive sensor applied to a rotary encoder or the like is used together with a detection circuit as shown in FIG. In the figure, the detection signal SinOUT output from the sine wave detecting magnetic resistance element A is compared with the reference voltage V0 in the comparator 12, and the square wave a as shown in FIG. Is converted to. Similarly, the detection signal CosOUT is converted by the comparator 14 into a square wave b as shown in FIG. 6 (b). Here, the reference voltage controller 15 controls the reference voltage V0 so that the duty ratio of the square wave a is 50%. That is, if the duty ratio of the square wave a is larger than 50%, the level of the reference voltage V0 is raised, and if the duty ratio is smaller than 50%, the level of the reference voltage V0 is lowered. As a result, the reference voltage V0 changes so as to pass through the central portion of the upper and lower envelopes of the detection signal SinOUT shown in FIG. The reference voltage V0 is also used as the reference voltage of the comparator 14 for the cosine wave detecting magnetic resistance element B.

However, in the case of the conventional magnetoresistive sensor, the detection signal SinOUT and the detection signal CosOUT have different swelling timings, so that the reference voltage V0 deviates from the center of the envelope of the detection signal CosOUT. Therefore, the duty ratio of the square wave b greatly fluctuates, and it becomes difficult to perform accurate position detection.

The present invention has been made in view of the above-mentioned circumstances, and even when a slight physical distortion occurs in the magnetic recording medium, the magnetic resistance elements for sine wave detection and the cosine wave detection are output respectively. It is an object of the present invention to provide a magnetoresistive sensor for a magnetic encoder that can make the undulations of the respective detection signals in phase with each other and thereby reduce the detection error.

"Means for Solving the Problems" The present invention provides the magnetic information from a magnetic recording medium on which magnetic information alternating at a predetermined wavelength along a predetermined orbit is recorded. In a magnetoresistive sensor for a magnetic encoder for detecting using a magnetoresistive element that changes in accordance with, a first wavelength, a half wavelength, and a first wavelength, a second wavelength, a third wavelength, and a fourth wavelength that are sequentially arranged at intervals of one wavelength. And a first, a second, and a third connection part for sequentially connecting these first, second, third, and fourth magnetic detection parts so as to form a square wave, and a voltage is applied across the both ends. Is applied and the magnetic recording medium is displaced and a first magnetoresistive element that outputs a first detection signal from the second connection portion and a second magnetoresistive element are sequentially arranged at intervals of two wavelengths, a half wavelength, and two wavelengths. 5th, 6th, 7th and 8th magnetism The output part and the fourth, fifth, and sixth connection parts that sequentially connect the fifth, sixth, seventh, and eighth magnetic detection parts so as to form a square wave, and a voltage is applied to both ends. And a second magnetoresistive element that outputs a second detection signal from the fifth connection portion when the magnetic recording medium is displaced, the first magnetoresistive element and the second magnetoresistive element. The elements are arranged in a nested manner, and one of the first detection signal and the second detection signal is a sine wave and the other is a cosine wave.

"Operation" Since the magnetic resistance element for detecting the sine wave and the magnetic resistance element for detecting the cosine wave are arranged in a superimposed manner in a nested manner, the magnetic information of the sine wave is detected from the same portion of the track of the magnetic recording medium, Thereby, even when a slight physical distortion occurs in the magnetic recording medium, the swell of both detection signals respectively output from the sine wave detection magnetic resistance element and the cosine wave detection magnetic resistance element is in-phase, This reduces the detection error.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

1 (a) and 1 (b) are diagrams showing the configuration of an embodiment of the present invention. In addition, in FIG. 1 (a), the illustration of the portion other than the pattern of the magnetoresistive element 4 is omitted.

In these figures, 10 is a substrate made of, for example, borate glass and having a high insulating property and smoothness, and a sine wave composed of detection units S _{1 to} S ₈ and connection units C _{1 to} C ₈ is provided on the substrate 10. Magnetic resistance element A for detection, detection S _{9 to} S ₁₆ and connecting portions C _{9 to} C
_A cosine wave detecting magnetoresistive element B consisting of ₁₆ is deposited. On the substrate 10 on which the sine wave detecting magnetic resistance element A and the cosine wave detecting magnetic resistance element B are vapor-deposited, for example, a protective film formed of a PSG film (phospho-silicate-glass; silicon oxide film doped with phosphorus) 14 is formed. The magnetoresistive element 4 including the sine wave detecting magnetic resistance element A and the cosine wave detecting magnetic resistance element B is a ferromagnetic material such as Ni-Fe (nickel-iron), Ni-Co (nickel-cobalt), or InSb. (Cindium antimonide) and other semiconductors.

Further, the sine wave detecting magnetic resistance element A and the cosine wave detecting magnetic resistance element B are arranged in a superposed manner on the substrate 10, and the comb-shaped pattern of the sine wave detecting magnetic resistance element A has a cosine wave detecting magnetic resistance. The resistance elements B are arranged in a nested manner with respect to the comb-shaped pattern.

Here, the relative positional relationship between the detection units S _{1 to} S ₁₆ will be described. The detection unit S ₂ is separated from the detection unit S ₁ by λ, and the detection unit S ₁ is separated from the detection unit S 1.
₃ is separated from the detector S ₂ by 2λ, and the detector S ₄ is separated from the detector S ₃ by λ.
The detector S ₅ is separated from the detector S ₄ by 3 / 2λ, the detector S ₆ is separated from the detector S ₅ by λ, and the detector S ₇ is separated from the detector S ₆ by 2λ. ₈ is separated from the detection section S ₇ by λ.
Further, the detection unit S ₁₅ is separated from the detection unit S ₁₆ by 2λ, and the detection unit S ₁₄
Is separated from the detecting section S ₁₅ by λ, and the detecting section S ₁₃ is separated from the detecting sections S ₁₄ and 2.
The detector S ₁₂ is separated from the detector S ₁₃ by λ / 2, the detector S ₁₁ is separated from the detector S ₁₂ by 2λ, and the detector S ₁₀ is separated from the detector S ₁₁ by λ. S ₉ is placed 2λ away from the detection S ₁₀ . Furthermore, each detection unit S ₁ , S ₃ , S ₅ , S ₇ ,
The detectors S ₁₆ , S ₁₄ , S ₁₂ , and S ₁₀ are arranged with a distance of λ / 4.

As described above, the magnetic resistance element A for detecting the sine wave and the magnetic resistance element B for detecting the cosine wave are arranged in the magnetic recording medium 1 (see FIG. 3).
They are arranged in a nested manner and in a superposed manner so that the phase shifts by 90 ° with respect to the wavelength λ of the sine wave recorded in 1.

Next, a case will be described where the magnetic resistance sensor according to the above-described embodiment is used to detect the magnetic information of the sine wave recorded on the magnetic recording medium 1 in which the distortion as shown in FIG. To do.

In this case, connect terminal T ₃ to ground and connect terminals T ₁ and T ₅ to + VCC
Is applied, the terminal T is moved along with the displacement of the magnetic recording medium 1.
Detection signals SinOUT and CosOUT as shown in FIGS. 2A and 2B are output from ₂ and T _4, respectively. That is, since the sine wave detecting magnetic resistance element A and the cosine wave detecting magnetic resistance element B are arranged in a nested manner so as to overlap each other, magnetic information of the sine wave is transmitted from the same portion of the track of the magnetic recording medium 1. Even if a slight physical distortion is generated in the magnetic recording medium 1 due to the detection, the sine wave detecting magnetic resistance element A and the cosine wave are detected as shown in FIGS. The swells U ₁ and U _{2 of the} detection signals SinOUT and CosOUT respectively output from the detection magnetic resistance element B are made in phase. Therefore, the detection error can be reduced by using the magnetoresistive sensor of each of the above-described embodiments.

FIG. 7 shows measured waveforms of the detection signal obtained from the magnetoresistive sensor according to the present embodiment. In the figure, (a) is the waveform of the detection signal SinOUT, and (b) is the detection signal CosOU.
It shows a waveform of T. As shown in the figure, it can be seen that low-frequency swells of substantially the same phase are superimposed on the detection signals SinOUT and CosOUT. In the conventional magnetoresistive sensor, these low-frequency undulations are superimposed at the shifted timing, which is an obstacle to accurate position detection as described above. However, according to the present embodiment, as shown in FIG. 7, the respective detection signals SinOUT and Cos are
Since the undulations superimposed on OUT are almost in phase, accurate position detection can be performed.

[Advantages of the Invention] As described above, according to the present invention, the magnetic information is recorded on a magnetic recording medium on which sinusoidal magnetic information is recorded along a predetermined orbit, and the specific resistance indicates the strength of the magnetic field. In a magnetoresistive sensor for a magnetic encoder that detects using a magnetoresistive element that changes in accordance with, a sine wave detecting magnetoresistive element that outputs a sine wave detection signal with displacement of the magnetic recording medium, and a cosine wave. The magnetic resistance element for detecting a cosine wave for outputting the detection signal of is arranged in a nested manner so that the magnetic information of the sine wave is detected from the same portion of the orbit of the magnetic recording medium, and thereby the magnetic recording is performed. Even when a slight physical distortion occurs in the medium, it is possible to make the swell of each detection signal output from the sine wave detection magnetic resistance element and the cosine wave detection magnetic resistance element in phase, thereby Inspection The effect that the output error can be reduced is obtained.

Further, according to the present invention, the interval between the one of the first and second magnetoresistive elements located inside the nested arrangement is set to a half wavelength of the sine wave, and the nested arrangement is provided. Since the interval in which the other element located outside is set to one and a half wavelength of the sine wave is provided, the device can be made extremely small.

[Brief description of drawings]

FIG. 1 (a) is a schematic plan view showing the configuration of an embodiment of the present invention, FIG. 1 (b) is a sectional view taken along line BB of FIG. 1 (a), and FIG.
(A) and (B) are waveform charts for explaining the operation of the embodiment of the present invention, and FIGS. 3A to 3D are the magnetic recording medium 1 and the magnetoresistive sensor 2 of the conventional magnetic rotary encoder. 4A to 4C are views for explaining problems when the conventional magnetoresistive sensor 2 is used, and FIG. 5 is used with a magnetoresistive sensor in a rotary encoder or the like. 6 is a circuit diagram illustrating the configuration of a detection circuit that is used, FIG. 6 is a waveform diagram showing a square wave signal obtained from the detection circuit, and FIG. 7 is an actual measurement of detection signals obtained from a magnetoresistive sensor according to an embodiment of the present invention. It is a wave form diagram which shows an example. A: sine wave detecting magnetic resistance element, B ... cosine wave detecting magnetic resistance element, S _{1 to} S ₁₆ ...... detecting section, C _{1 to} C ₁₆ ...... connecting section, T _{1 to} T ₅ ...... terminal 1 ... Magnetic recording medium, 4 ...
Magnetoresistive element, 10 ... Substrate, 12 ... Insulating film, 14 ...
…Protective film.

Front page continued (72) Inventor Yoshinori Hayashi 10-1 Nakazawa-machi, Hamamatsu-shi, Shizuoka Nihon Gakki Co., Ltd. (56) Reference JP 59-166812 (JP, A) JP 59- 179321 (JP, A) JP-A-55-59314 (JP, A)

Claims (1)

[Claims] 1. A magnetoresistive element whose specific resistance changes in accordance with the strength of a magnetic field from a magnetic recording medium on which magnetic information alternating with a predetermined wavelength along a predetermined trajectory is recorded. In a magnetoresistive sensor for a magnetic encoder for detecting by using, a first, a second, a third and a fourth magnetic detection section sequentially arranged at intervals of one wavelength, one and a half wavelength and one wavelength, and a square wave The magnetic recording medium is composed of first, second and third connecting portions for sequentially connecting the first, second, third and fourth magnetic detecting portions so that a voltage is applied to both ends thereof. Is displaced, a first magnetoresistive element that outputs a first detection signal from the second connection portion and fifth, sixth, and sixth elements sequentially arranged at intervals of two wavelengths, a half wavelength, and two wavelengths. Make a square wave with the 7th and 8th magnetic detectors. And the fifth, sixth, seventh and eighth magnetic detectors are sequentially connected, and the fourth, fifth and sixth connecting portions are connected. When a voltage is applied to both ends and the magnetic recording medium is displaced, A second magnetoresistive element that outputs a second detection signal from the fifth connection portion, wherein the first magnetoresistive element and the second magnetoresistive element are arranged in a nested manner, and One of the first detection signal and the second detection signal is a sine wave, and the other is a cosine wave.