JPH05346329A - Magnetic sensor - Google Patents

Abstract

PURPOSE:To cancell 5th-order or higher odd harmonics of a reproduction signal in a magnetic sensor with an MR element. CONSTITUTION:In a magnetic sensor composed of a magnetoresistance effect element that can be move relatively along the scalewise direction facing the recorded magnetic scale by recording wavelength l, a linear magnetic resistance effect element at a specified position in a scalewise direction is equally divided into 2<n> (n=2, 3, 4,... e.g. 2) linear magnetoresistance effect element pieces M(1/4)a-M(1/4)d, and they are connected serially. Furthermore, the scalewise direction position of the 2<n> magnetoresistance effect element pieces M(1/4)a-M(1/4)d is set to the specified position + or -{lambda/(8X3)}+ or -{lambda/(8X5)}+ or -{lambda/(8X7)}+ or -...+ or -[lambda/{8X(2n-1)}]+ or -[lambda/{8X(2n+1)}].

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic sensor using a magnetoresistive effect element (hereinafter abbreviated as MR element).

[0002]

2. Description of the Related Art Since an MR element basically has a square characteristic, it is necessary to make its reproduction output linear. The linearization method includes the following methods. (A) A DC bias magnetic field is applied to the MR element. (B) Bridge the MR element to remove even harmonics. The wavelength of the reproduction output when the MR element is bridge-connected with the magnetic field bias is half the recording wavelength of the magnetic scale. In the case of the method (b), when the signal magnetic field is not distorted, a clean sine wave is obtained (frequency is twice), but when the signal magnetic field is distorted, the reproduction output is distorted. When the magnetic recording is performed finely on the magnetic scale, the even harmonics are small, but the odd harmonics are significantly large.

In particular, in a magnetic sensor composed of an MR element,
When detecting the position of the magnetic scale, in order to obtain a position resolution higher than the recording wavelength of the magnetic scale by interpolation, the reproduction signal must be a sinusoidal wave without distortion.

First, the principle of a magnetic sensor using an MR element will be described with reference to FIG. The MR element is an application of the fact that the magnetic thin film changes its resistance depending on the angle θi formed between the direction of the magnetization M and the direction of the current I flowing through it. The change in the resistance ρ of the magnetic thin film is expressed by the following equation.

[0005]

Where ρ = ρ ₀ −Δρ (sin θi) ² where Δρ = ρ ₀ −ρ ₉₀ , sin θi = H / H _s ρ ₀ : Resistance when the direction of the magnetization M and the direction of the current I match. ρ ₉₀ : Resistance when the direction of magnetization M and the direction of current I are orthogonal to each other H: Signal magnetic field H _s : Saturation magnetic field When the signal magnetic field H changes sinusoidally and a stray magnetic field H ₀ exists, that is, H = H _a sin θ _m + H _o , the resistance ρ becomes as follows.

[0006]

(2) ρ = ρ ₀ − (Δρ / 2) · (H _a ² + 2H ₀ ² ) / H _s ² + (Δρ / 2) · (H _a / H _s ) ² · sin2θ _m − (2ΔρH _a H _o / H _s ) ・ sin θ _m

In this equation 2, if H _o = 0, the following equation is obtained.

[0008]

[Number 3] _{ρ = ρ 0 - (Δρ /} 2) · (H a / H s) 2 + (Δρ / 2) · (H a / H s) 2 · sin2θ m

That is, when the signal magnetic field changes in a sine wave shape,
Frequency of the signal magnetic field (f_oFrequency)
Number (2f_o= F₁Signal) (this is the fundamental wave)
Is obtained. When there is a stray DC magnetic field,
The frequency f of the signal magnetic field as _oSo that the waves of
Becomes Therefore, in general, the frequency f of the signal magnetic field_oThe wave of
Bridge the MR element to cancel
I try to take out the main wave.

Next, a conventional magnetic sensor will be described with reference to FIG. FIG. 29 (A) shows a magnetic sensor composed of MR elements, and FIG. 29 (B) shows its reproducing circuit (bridge circuit).
And (C) shows a magnetic scale (where the recording wavelength is λ). A position detection output is obtained from the magnetic sensor by moving the magnetic sensor while facing the magnetic scale. In this magnetic sensor, an MR element made of a ferromagnetic material such as Ni-Fe or Ni-Co is arranged on an insulating substrate such as glass as described later.

The magnetic sensor shown in FIG. 29A will be described.
M1 to M8 are MR elements, which are arranged in parallel with each other and are arranged so as to be orthogonal to the longitudinal direction of the magnetic scale. The arrow of each MR element indicates the direction of magnetization. These MR elements M1 to M8 are divided into two sets of MR elements M1 to M4 and M5 to M8, and the distance between the two sets of MR elements is

[0012]

(4) (M + 1/2) λ / 2 (M = 0, 1, 2, ...). Further, between the MR elements M1 and M3 and M
Between 5 and M7,

[0013]

(5) (N + 1/2) λ / 2 (N = 0, 1, 2, ...). Further, between the MR elements M1 and M2, M
The intervals between 3, M4, between M5 and M6, and between M7 and M8 are

[0014]

## EQU6 ## It is set to (2L + 1) λ / 2 (L = 0, 1, 2, ... ......).

As shown in FIGS. 29A and 29B, in the set of MR elements M1 to M4, the lower end of MR element M1 is connected to the power supply terminal V, and the upper end of M1 is connected to the upper end of M2. , M2 is connected to the lower end of M3, the upper end of M3 is connected to the upper end of M4, and the lower end of M4 is connected to the ground terminal G. Further, in the group of MR elements M5 to M8, the lower end of the MR element M5 is connected to the power supply terminal V, and the upper end of M5 is M.
6, the lower end of M6 is connected to the lower end of M7, the upper end of M7 is connected to the upper end of M8, and the lower end of M8 is connected to the ground terminal G. The connection between each MR element is
An MR element or a non-magnetic conductor is used. The terminal A derived from the connection midpoint of the MR elements M2 and M3 is connected to the non-inverting input terminal of the subtractor (differential amplifier) S, and the terminal B derived from the connection midpoint of the MR elements M6 and M7. Is connected to the inverting input terminal of the subtractor S, and the output terminal T of the subtractor S
The subtraction output is obtained at.

According to such a magnetic sensor, the MR element M
1, M2 series circuit, M3, M4 series circuit, M5, M
In the series circuit of 6 and the series circuit of M7 and M8, it can be seen from Equation 6 that the waves of the frequency f _o of the positive phase and the negative phase are canceled respectively.

Further, in the series circuit of the MR elements M1, M2 and M3, M4 and the series circuit of M5, M6 and M7, M8, from the equation 5, they are respectively in-phase even-order (second-order, fourth-order, fourth-order).
Next .........) Harmonics are generated. Therefore, the MR element M
If the even harmonics of A and MB are subtracted by the subtractor S, they will be canceled.

As is apparent from the above, in the conventional example shown in FIG. 29, the even harmonics can be canceled to obtain the fundamental wave, but the odd harmonics (third, fifth, ...) Harmonics. Wave cancellation is not possible.

Therefore, a magnetic sensor capable of canceling the third harmonic (Japanese Patent Application No. 3-4972, which has not been known before the present application).
No. 0) will be described with reference to FIG. Incidentally, FIG.
At 0, the horizontal axis (the scale direction of the magnetic scale) is λ /
The X axis represents the position of the magnetic scale with respect to the track center in the track width direction. As shown in FIG. 30, one MR element M (its length is equal to the track width and its position is X / λ
= 0), and the divided MR elements M (1/2) a and M (1/2) b have an interval of λ / 12, and their position is the horizontal axis. It is moved so as to be point-symmetric with respect to the origin O above. Since the half wavelength of the third harmonic is λ / 12, these MR elements M (1/2) a,
If each end of M (1/2) b on the horizontal axis is connected by an MR element (or a non-magnetic conductive element) (not shown) perpendicular to these ends, the third harmonic can be canceled. I understand.

MR elements M (1/2) a, M (1/2) b
The position along the horizontal axis of (the scale direction of the magnetic scale) is ±
It becomes {λ / (8 × 3)}.

Now, if the original signal is Eosin (θ),
The read signal E is expressed by the following equation.

[0022]

[Equation 7] E = 1/2 Eo [sin (θ−π / 6) + sin (θ + π / 6)] + Eocos (π / 6) · sin (θ) = 0.866Eo · sin (θ)

From this equation 7, it can be seen that the amplitude of the read signal is as small as 0.866 times the amplitude of the MR element M before division, but its phase is the same as the phase of the original signal.

Therefore, by dividing the MR elements M1 to M8 of FIG. 29 as shown in FIG. 30, it is possible to obtain a magnetic sensor which can obtain a reproduction signal in which both the even harmonics and the third harmonics are canceled.

[0025]

According to the magnetic sensor shown in FIG. 30, since the third harmonic can be canceled, the ninth, fifteenth, ... The harmonics of the next, the 7th, the 11th, the 13th, and so on cannot be canceled.

In view of the above point, the present invention proposes a magnetic sensor using an MR element, which can cancel the fifth and higher odd harmonics of a reproduced signal.

[0027]

According to a first aspect of the present invention, there is provided a magnetic sensor comprising a magnetoresistive effect element facing a magnetic scale recorded with a recording wavelength λ and relatively movable along the scale direction. , The linear magnetoresistive effect element at a predetermined position in the graduation direction is 2 ⁿ (where n = 2
3, 4, ...........) The linear magnetoresistive element pieces are equally divided and electrically connected in series.
^{The position of the n} magnetoresistive element pieces in the scale direction is a predetermined position ± {λ / (8 × 3)} ± {λ / (8 × 5)} ± {λ / (8 × 7)} ± ...... ..... ±. [Λ / {8 × (2n−1)}] ± [λ / {8 × (2n + 1)}].

A second aspect of the present invention is the magnetic sensor of the first aspect of the present invention, in which 2 ⁿ pieces of magnetoresistive element are electrically connected in series so as to form a continuous step. ..

The third aspect of the present invention is substantially equivalent to the magnetic sensor of the second aspect of the present invention, and includes a magnetoresistive effect element having a shape of a smooth curve connecting the respective midpoints of the 2 ⁿ magnetoresistive effect pieces. It consists of

A fourth aspect of the present invention is the magnetic sensor of the third aspect of the present invention, in which the positions of both ends of the magnetoresistive effect element having a curved shape in the scale direction from the respective midpoints of the magnetoresistive effect element. Is approximately equal to the average position of the continuous stairs in the scale direction.

A fifth aspect of the present invention is the magnetic sensor according to the first, second, third or fourth aspect of the present invention, in which a pair of magnetic sensors that are point-symmetric with respect to each midpoint thereof are provided, and the magnetic sensor of the pair is provided. An end on the magnetic scale side or an end on the side opposite to the magnetic scale is electrically connected, and the pair of magnetic sensors is inclined so as to be line-symmetric with respect to the direction orthogonal to the scale direction.

[0032]

According to the first aspect of the present invention, the fifth and higher order odd harmonics of the reproduced signal can be removed, and a reproduced signal closer to a sine wave can be obtained.

According to the second aspect of the present invention, the fifth and higher odd harmonics of the reproduced signal can be removed, a reproduced signal closer to a sine wave can be obtained, and an electrical crossing portion occurs. Since it does not exist, it is easy to manufacture a magnetic sensor.

According to the third aspect of the present invention, the fifth and higher order odd harmonics of the reproduced signal can be removed, a reproduced signal closer to a sine wave can be obtained, and only the magnetoresistive effect element can be obtained. Since the magnetic sensor can be configured by using the magnetic sensor, the manufacturing is facilitated, and Barkhausen noise can be reduced as compared with the stepwise magnetic sensor including only the magnetoresistive effect element.

According to the fourth aspect of the present invention, the fifth and higher odd harmonics of the reproduced signal can be removed, a reproduced signal closer to a sine wave can be obtained, and only the magnetoresistive effect element can be obtained. Since the magnetic sensor can be configured by using the magnetic sensor, the manufacture can be facilitated, Barkhausen noise can be reduced, and low-order harmonics can be reduced.

According to the fifth aspect of the present invention, in addition to the effect of the first, second, third or fourth aspect of the present invention, the distortion of the reproduction signal due to the azimuth deviation of the magnetic scale of the magnetic sensor is canceled. be able to.

[0037]

Embodiments of the present invention will now be described in detail with reference to the drawings. First, with reference to FIG. 1, a magnetic sensor capable of canceling harmonics up to the fifth order will be described. Note that, in FIG. 1, as in FIG. 30, the horizontal axis represents λ / X and the vertical axis represents the position with respect to the track center in the track width direction of the magnetic scale. MR elements M (1/2) a and M (1/2) b shown by dotted lines in FIG.
The MR element is the same as that indicated by 0.

These MR elements M (1/2) a, M (1 /
2) MR element M shown by a solid line obtained by dividing b into upper and lower parts at ± 1/2 track widths.
(1/4) a, M (1/4) b and M (1/4) c, M
The interval of (1/4) d is the half wavelength of the fifth harmonic, that is, λ / 20, and the positions thereof are the MR element M (1/2) a and M (1/2) b, respectively. It is moved so as to be point-symmetric with respect to each midpoint. Then, between the end portions of the MR elements M (1/4) a and M (1/4) b on the horizontal axis and the lateral portions of M (1/4) c and M (1/4) d. MR elements M (1/4) b, M (1/4) arranged between the ends on the axis
If the ends of c on the horizontal axis are connected by an MR element (or a non-magnetic conductive element) (not shown) perpendicular to each other,
A magnetic sensor in which the fifth harmonic is canceled together with the third harmonic is obtained. It is needless to say that a harmonic of an odd multiple of three or more of the fifth harmonic is also canceled (this is a matter of course, so the description thereof will be omitted in the following embodiments).

MR elements M (1/4) a to M (1/4) d
The position of the horizontal axis of (the direction of the scale of the magnetic scale) is
± {λ / (8 × 3)} ± {λ / (8 × 5)}.

Therefore, if the MR elements M1 to M8 of FIG. 29 are respectively divided as shown in FIG.
It is possible to obtain a magnetic sensor that can obtain a reproduction signal in which the third harmonic and the fifth harmonic are canceled.

Next, with reference to FIG. 2, a magnetic sensor capable of canceling harmonics up to the 7th order will be described. In FIG. 2, the MR element M (1 /
2) a and M (1/2) b are MR elements similar to those shown in FIG. 30, and the MR element M (1 /
4) a to M (1/4) d are the same MR as shown in FIG.
It is an element.

These MR elements M (1/4) a to M (1 /
2) d is vertically divided into two equal parts as described above, and the MR elements M (1/8) a and M (1/8) b shown by the divided solid lines are divided.
Interval, M (1/8) c, M (1/8) d interval,
The interval between M (1/8) e and M (1/8) f and M (1 /
8) The intervals between g and M (1/8) h are both half wavelengths of the 7th harmonic, that is, λ / 28, and their positions are MR elements M (1/4) a ... M (1/4) d
Move so that it becomes point-symmetric with respect to each midpoint of. Then, the MR elements M (1/8) a and M (1/8) b
Of M (1/8) c and M (1/8) d of M (1 /
8) e and M (1/8) f, M (1/8) g and M
If the (1/8) h and adjacent ends of each MR element are connected by an MR element (or a non-magnetic conductive element) (not shown) perpendicular to each other, the third harmonic A magnetic sensor is obtained which, together with the wave and the fifth harmonic, gives a canceled reproduced signal of the seventh harmonic.

MR elements M (1/8) a to M (1/8) h
The position of the horizontal axis of (the direction of the scale of the magnetic scale) is
± {λ / (8 × 3)} ± {λ / (8 × 5)} ± {λ /
(8 × 7)}.

Therefore, if the MR elements M1 to M8 of FIG. 29 are respectively divided as shown in FIG.
It is possible to obtain a magnetic sensor that can obtain a reproduction signal in which the third harmonic, the fifth harmonic, and the seventh harmonic are canceled.

Next, referring to FIG. 3, a magnetic sensor capable of canceling harmonics up to the 11th order will be described. In FIG. 3, the MR element M (1 /
8) a to M (1/8) h are the same M as shown in FIG.
It is an R element.

These MR elements M (1/8) a to M (1 /
8) In the same manner as described above, h is vertically divided into two equal parts, and MR elements M (1/16) a, M (1/1) shown by the divided solid lines
6) Interval between b, M (1/16) c, M (1/16) d
Interval, M (1/16) e, M (1/16) f interval, M (1/16) g, M (1/16) h interval, M
The interval between (1/16) i and M (1/16) j, M (1 /
16) k, the interval between M (1/16) l, M (1/16)
m, the spacing between M (1/16) n and M (1/16) o,
The intervals between M (1/16) p are both half wavelengths of the 11th harmonic, that is, λ / 44, and the positions thereof are MR elements M (1/8) a to M (1 / 8) Move so as to be point-symmetric with respect to each midpoint of h. Then, between the (1/16) a and M (1/16) b of these MR elements, between M (1/16) c and M (1/16) d, M (1
/ 16) e and M (1/16) f between M (1/16)
Between g and M (1/16) h, M (1/16) i, M (1
/ 16) j between M (1/16) k and M (1/16) l
Between, M (1/16) m, between M (1/16) n and M
MR elements (or non-magnetic conductivity) that are perpendicular to (1/16) o, M (1/16) p, and between adjacent ends of each MR element on the horizontal axis. A magnetic sensor capable of obtaining a reproduction signal in which the 11th harmonic is canceled together with the 3rd harmonic, the 5th harmonic, and the 7th harmonic can be obtained by connecting the elements (not shown).

MR elements M (1/16) a to M (1/1
6) The position of p in the direction of the horizontal axis (direction of the scale of the magnetic scale) is ± {λ / (8 × 3)} ± {λ / (8 × 5)} ±
{Λ / (8 × 7)} ± {λ / (8 × 9)} ± {λ / (8
X11)}.

The position (X / λ) on the horizontal axis of each MR element is specifically as follows. M (1/16) a: 0.09589 M (1/16) i: 0.01255 M (1/16) b: 0.07316 M (1/16) j: -0.01017 M (1/16) ) C: 0.06017 M (1/16) k: -0.02316 M (1/16) d: 0.03745 M (1/16) l: -0.04589 M (1/16) e: 0 0.04589 M (1/16) m: -0.03745 M (1/16) f: 0.02316 M (1/16) n: -0.06017 M (1/16) g: 0.01017 M ( 1/16) o: -0.07316 M (1/16) h: -0.01255 M (1/16) p: -0.09589

Therefore, if the MR elements M1 to M16 of FIG. 29 are respectively divided as shown in FIG. 3, the third harmonic, the fifth harmonic, the seventh harmonic, and the eleventh harmonic as well as the even harmonics. It is possible to obtain a magnetic sensor that can obtain a canceled reproduction signal.

By repeating the above method, in theory, it is possible to cancel the 13th, 17th, 19th, ... Since the width of the MR element is finite, the reproduction resolution of the MR element is limited, and it is meaningless to divide the MR element at or above the reproduction resolution.

Next, the reproduced waveforms of the magnetic sensor in the case of the conventional example of FIG. 30 and the embodiment of FIGS. 1 to 3 obtained by simulation are shown in the drawings. Before that, refer to FIG. , The simulation method will be explained.
Assuming an MR magnetic scale, recording wavelength 80 on the plating medium
The reproduced waveform is obtained by simulation for the case of saturation recording at μm. In this case, the coercive force Hc of the medium is 1200 Oe, the residual magnetization Mr is 640 G, and the thickness δ is 3.
A recording scale signal having an inversion width a of 4.9 μm (1.4δ) is used.

The magnetization reversal formula is expressed as the following formula.

[0053]

Mx (x) = (2Mr / π) tan ⁻¹ (x / a) where −δ ≦ y ≦ 0 a: magnetization reversal width Mr: residual magnetization

At this time, the x-direction magnetic field Hx at the distance d from the medium is expressed by the following equation.

[0055]

Hx (x, d) = − Mr [tan ⁻¹ {(d + δ + a) / x} −tan ⁻¹ {(d + a) / x}] = −Mrtan ⁻¹ [d · x / {x ² + (D + δ + a) · (d + a)} where δ: media thickness a: recording scale signal inversion width

FIG. 5 shows the magnetic field distribution (X distribution) of the isolated transition calculated on the assumption that a magnetic field as shown in Equation 9 is generated by the magnetization reversal.
It shows in (A). The results of calculation of the magnetic field distribution at the recording wavelength of 80 μm when d = 1 μm, 4 μm, and 10 μm by the superposition method are shown in FIGS. 5B, 6A, and 6B. MR
The larger the distance d between the element and the medium, the larger the magnetic field, but the larger the distortion. The distance d between the MR element and the medium is d = 10 μm
However, the reproduced waveform is not a perfect sine wave.

In this way, the calculated magnetic field was applied to the MR element, and the reproduced waveform was calculated assuming that it has a square as shown in the equation (3). 7 (A), 9 (A) and 1
1 (A) shows reproduced waveforms when the even harmonics from the magnetic sensor including the bridge circuit and the subtractor of the MR element shown in FIG. 29 are removed when d = 1 μm, 4 μm, and 10 μm, respectively. 7B, 9B, and 11B show d = 1 μm, 4 μm, and 10 μm, respectively.
In the magnetic sensor including the bridge circuit and the subtractor of the MR element shown in FIG. 29 at that time, the even harmonics and the third harmonics in the case where each MR element is configured as shown in FIG. 30 are removed. The reproduced waveform in this case is shown. 8 (A) and 10 (A) show d = 1 μm and 4 μ, respectively.
In the magnetic sensor including the bridge circuit of the MR element shown in FIG. 29 and the subtractor when m, even harmonics, third harmonics and fifth harmonics when each MR element is configured as shown in FIG. The reproduced waveform when is removed is shown. 8B and 10B respectively show d = 1 μ.
In the magnetic sensor composed of the bridge circuit of the MR element and the subtractor shown in FIG. 29 at m and 4 μm, the even harmonics, the third order and the fifth order in the case where each MR element is configured as shown in FIG. 7A and 7B show reproduced waveforms when the 7th harmonic is removed.

According to these reproduced waveforms, for example, d =
It can be seen that when the thickness is 1 μm, the reproduced waveform when the even harmonics, the third harmonic, the fifth harmonic, and the seventh harmonic are removed is a substantially clean sine wave. Also, for example, when d = 10 μm, it can be seen that the reproduced waveform when the even harmonics and the third harmonic are removed is a substantially clean sine wave.

Now, for example, the MR of the magnetic sensor of FIG.
The array of elements is not continuous stepwise, but partly undulating. Therefore, as shown in FIG. 12 (A), by moving the positions of some of the MR elements in FIG. 3 (indicated by dotted lines in FIG. 12 (A)) in the vertical axis direction, a continuous staircase is formed. Since the MR element does not move in the horizontal axis direction, it can be seen that the magnetic sensor of FIG. 12A is equivalent to the magnetic sensor of FIG.

In the magnetic sensor shown in FIG. 12A, the MR element parallel to the horizontal axis is only for connecting the MR element parallel to the vertical axis, but the existence thereof is Barkhausen noise. Will increase the occurrence of. Therefore, if the sum of the lengths of the MR elements of this magnetic sensor can be reduced, the generation of Barkhausen noise can be reduced accordingly.

Therefore, as shown in FIG.
It is considered to replace the magnetic sensor of (A) with a magnetic sensor composed of an MR element having a smooth curve connecting the midpoints of the MR elements parallel to the vertical axis. It should be noted that although the end of this curved MR element has arbitrariness, the midpoint of the two MR elements at the end is linearly extended. In FIG. 13A, d =
In the magnetic sensor composed of the bridge circuit of the MR element and the subtractor shown in FIG.
The element has a smooth curved MR as shown in FIG.
The reproduced waveform in the case of being composed of elements is shown, and it can be seen that this is a substantially clean sine wave shape. FIG. 13B shows the magnetic sensor including the bridge circuit of the MR element and the subtractor shown in FIG. 29 when d = 1 μm.
12B shows reproduced waveforms in the case where each MR element is configured by a linear approximation MR element instead of the smooth curved MR element as shown in FIG. 12B. Since this does not sufficiently cancel harmonics. , It can be seen that the linear approximation is inappropriate.

As is clear from the above, the magnetic sensor in which the MR element constitutes the spatial filter is
Although it is possible to obtain a substantially clean sine wave-shaped reproduction signal in which harmonics are attenuated, on the other hand, it has the following weak points. That is, consider a case where the MR element shown in FIG. 29 has an azimuth shift. In this case, the MR element rotates around its center, and the amount of movement of the track edge is, for example, ±
1 μm deviation (rotation angle ± when track width is 2 mm
(Corresponding to 0.057 °), each d = 1 μm
In the magnetic sensor including the bridge circuit of the MR element and the subtractor shown in FIG. 29 at that time, the reproduction in the case where each MR element is configured by the smooth curved MR element as shown in FIG. 12B. Waveforms are shown in Fig. 14 respectively.
As shown in (A) and (B), it can be seen that a slight shift in azimuth significantly distorts the reproduced waveform. This is because the above-mentioned magnetic sensor is composed of a precise spatial filter composed of an MR element to cancel or attenuate harmonics.

In order to remove the distortion of the reproduced signal due to the azimuth shift of each MR element of this magnetic sensor, as shown in the partial structure of FIG.
The elements M1 and M2, M3 and M4, ... May be arranged so as to rotate about their respective centers in opposite directions by the same angle. In this way, when the azimuth shift occurs in the MR element, the paired MR elements are tilted in opposite directions, so that the distortion of the reproduced waveform due to the azimuth shift is reduced. In this case, when the MR element shown in FIG. 29 has an azimuth shift, the MR element rotates around its center and the amount of movement of the track end is, for example, 1
μm deviation (rotation angle ± 0.
(Corresponding to 057 °), in the magnetic sensor including the bridge circuit and the subtractor of the MR element shown in FIG.
FIG. 16 (A) shows the reproduced waveform in the case of the smooth curved MR element as shown in FIG. 2 (B). According to this, a clean sine wave is obtained, and harmonic distortion is almost eliminated. .. However, in this case, if the movement amount of the track end of the MR element is set to +2 μm, FIG.
The distortion increases as shown in.

Next, the reproduction signal of the magnetic sensor is FFT.
The distortion of the reproduction signal of the magnetic sensor was analyzed by (Fast Fourier Transform). 17 to 24 show the fundamental wave of the detection signal (half the recording wavelength, and its frequency is indicated by f ₁ ).
, The frequencies are f ₂ , f ₃ , ...
Second-order, third-order, indicated by ……………………………….
Those having a value of B or less are meaningless in terms of practical use and calculation accuracy, and are therefore cut with a line of -80 dB or less.

17 (A), (B) and FIG. 18 (A),
(B) shows d = 1 μm, 4 μm, 10 μm, 1
FIG. 30 shows a signal spectrum of a reproduced waveform when the even harmonics from the magnetic sensor including the bridge circuit and the subtractor of the MR element shown in FIG. 29 are removed at 5 μm. As is clear from these figures, it is understood that the reproduced signal has many harmonic components. Also, as a matter of course, the reproduction signal has 2
It can be seen that the second harmonic is removed. However, it can be seen that when d is large, harmonics are easily generated.

FIG. 19A shows the graph of FIG. 2 when d = 1 μm.
31 shows the signal spectrum of the reproduced waveform when the even harmonics and the third harmonics are removed when each MR element of the magnetic sensor of No. 9 has the configuration shown in FIG. 30. As is clear from this figure, it can be seen that the reproduced signal has the third and ninth harmonics removed.

FIG. 19B shows the case where the even harmonics and the third, fifth and seventh harmonics are removed when each MR element of the magnetic sensor of FIG. 29 is configured as shown in FIG. The signal spectrum of a reproduced waveform is shown.

As shown in FIGS. 12 (B) and 20 (A) described above, FIG. 1 capable of removing the 11th harmonic.
If the magnetic sensor of 2 (A) is replaced with a magnetic sensor consisting of a MR element having a smooth curve connecting the midpoints of the MR elements parallel to the vertical axis, the magnetic sensor at the end from the midpoint to the track end It was found that the distortion of the reproduced signal changes considerably depending on whether the extension is performed in this way. As shown in FIG. 20 (A), the signal spectrum of the reproduction signal of the magnetic sensor when d = 1 μm when extrapolated by a quadratic curve passing through the three end points a, b, d is shown in FIG. 20 (B). Shown in. In addition, FIG.
As shown in (A), the signal spectrum of the reproduction signal of the magnetic sensor when extrapolated by a straight line passing through the two points at the ends is shown in FIG.
It shows in (B). In addition, as shown in FIG.
FIG. 22B shows the signal spectrum of the reproduced signal when extrapolated from the position of the R element to a position of 1/2 of the track end portion when d = 1 μm when extrapolated linearly.
Further, as shown in FIG. 23 (A), reproduction at d = 1 μm when extrapolated toward the position of 1/3 of the track end when extrapolated linearly from the position of the MR element at the end The signal spectrum of the signal is shown in FIG. These FIG.
As can be seen from (B) of FIG. 23, the distortion of the reproduced signal is -60 dB or less, and a good result can be obtained. In other words, if the curve of the MR element of the magnetic sensor is properly selected, the distortion of the reproduced signal can be set to -60 dB or less. FIG. 24 shows the signal spectrum of the reproduced signal when the MR element is approximated by a slanted straight line, but it can be seen that the distortion of the reproduced signal cannot be sufficiently reduced.

FIG. 25 is a block diagram of FIG.
Magnetic sensor that can obtain the reproduction signal from which the second harmonic is removed
The stepwise MR element that composes
Shows a magnetic sensor replaced with a curved MR element.
The smooth curve of is the function Y = f ₁It is represented by (x) and its base
The stairs of the staircase-shaped MR element formed are expressed by the function Y = f
₂It is represented by (x). Also, the seat of the end of the smooth curve
Mark (X₁, W). However, 2W indicates the track width
You Then the average position of the smooth curve and stairs is
It is expressed as.

[0070]

[Equation 10]

[0071]

[Equation 11]

At this time, X ₁ is determined so that both average positions are substantially equal.

When the MR element constituting the magnetic sensor is formed in a smooth curved shape, it is difficult for the level of the relatively low-order harmonic of the reproduction signal to be zero. This is because the high-order terms have large attenuation due to the azimuth shift of the MR element. Therefore, it is necessary to reduce the level of low-order harmonics in the reproduced signal. Since the average position becomes a problem for low-order harmonics, by making the average position closer to the staircase shape of the MR element in which the harmonics can be completely eliminated by the above-mentioned method, Three
The second harmonic can be reduced. FIG. 26 shows a stepwise MR element configured to be able to erase up to the 11th harmonic,
It shows a magnetic sensor composed of a smooth curved MR element in which the coordinates X ₁ of the ends are determined so that the average positions thereof coincide with each other, passing through the middle points of the respective MR elements. The frequency spectrum of the reproduction signal of the magnetic sensor is -60 dB or less (distortion rate 1
%) Or less), indicating good characteristics.

[0074]

According to the first aspect of the present invention, it is possible to remove the fifth and higher odd harmonics of the reproduction signal, and obtain a reproduction signal closer to a sine wave.

According to the second aspect of the present invention, the fifth and higher order odd harmonics of the reproduced signal can be removed, a reproduced signal closer to a sine wave can be obtained, and an electrical crossing portion is generated. Since it does not exist, the magnetic sensor can be easily manufactured.

According to the third aspect of the present invention, the fifth and higher order odd harmonics of the reproduced signal can be removed, a reproduced signal closer to a sine wave can be obtained, and only the magnetoresistive effect element can be obtained. Since the magnetic sensor can be configured by using the magnetic sensor, the manufacturing is facilitated, and Barkhausen noise can be reduced as compared with the stepwise magnetic sensor including only the magnetoresistive effect element.

According to the fourth aspect of the present invention, the fifth and higher odd harmonics of the reproduced signal can be removed, a reproduced signal closer to a sine wave can be obtained, and only the magnetoresistive effect element can be obtained. Since the magnetic sensor can be configured by using a magnetic sensor, it is easy to manufacture, and Barkhausen noise can be reduced and low-order harmonics can be reduced as compared with a stepped magnetic sensor including only a magnetoresistive effect element. can do.

According to the fifth aspect of the present invention, in addition to the effects of the first, second, third or fourth aspect of the present invention, the distortion of the reproduction signal due to the azimuth shift of the magnetic sensor with respect to the magnetic scale is canceled. be able to.

[Brief description of drawings]

FIG. 1 is a diagram showing a magnetic sensor according to an embodiment of the present invention capable of removing harmonics up to the fifth order.

FIG. 2 is a diagram showing a magnetic sensor of an embodiment capable of removing harmonics up to the 7th order.

FIG. 3 is a diagram showing a magnetic sensor of an embodiment capable of removing harmonics up to the 11th order.

FIG. 4 is a diagram showing a reproducing system for obtaining a reproduced waveform by simulation.

FIG. 5 is a curve diagram showing a magnetic field distribution of an isolated transition for obtaining a reproduced waveform by simulation.

FIG. 6 is a curve diagram showing a magnetic field distribution of an isolated transition for obtaining a reproduced waveform by simulation.

FIG. 7 is a curve diagram showing a reproduced waveform by simulation.

FIG. 8 is a curve diagram showing a reproduced waveform by simulation.

FIG. 9 is a curve diagram showing a reproduced waveform by simulation.

FIG. 10 is a curve diagram showing a reproduced waveform by simulation.

FIG. 11 is a curve diagram showing a reproduced waveform by simulation.

FIG. 12 is a diagram showing a modification of the embodiment capable of removing harmonics up to the 11th order.

FIG. 13 is a curve diagram showing a reproduced waveform by simulation.

FIG. 14 is a curve diagram showing a reproduced waveform by simulation.

FIG. 15 is a diagram showing a magnetic sensor including a pair of symmetrically arranged MR elements.

FIG. 16 is a curve diagram showing a reproduced waveform by simulation.

FIG. 17 is a diagram showing a signal spectrum of a reproduced waveform.

FIG. 18 is a diagram showing a signal spectrum of a reproduced waveform.

FIG. 19 is a diagram showing a signal spectrum of a reproduced waveform according to the example.

FIG. 20 is a diagram showing a magnetic sensor of an example and a signal spectrum of a reproduced waveform thereof.

FIG. 21 is a diagram showing a magnetic sensor and a signal spectrum of its reproduced waveform.

FIG. 22 is a diagram showing a magnetic sensor of an example and a signal spectrum of a reproduced waveform thereof.

FIG. 23 is a diagram showing a magnetic sensor of an example and a signal spectrum of a reproduced waveform thereof.

FIG. 24 is a diagram showing a signal spectrum of a reproduced waveform.

FIG. 25 is a diagram showing a magnetic sensor of an example.

FIG. 26 is a diagram showing a magnetic sensor of Example.

FIG. 27 is a diagram showing a signal spectrum of a reproduced waveform according to an example.

FIG. 28 is an explanatory diagram of an MR element

FIG. 29 is a diagram showing a conventional magnetic sensor and magnetic scale.

FIG. 30 is a diagram showing a conventional magnetic sensor capable of removing third-order harmonics.

[Explanation of symbols]

 M MR element

Claims (5)

[Claims] 1. A magnetic sensor comprising a magnetoresistive effect element facing a magnetic scale recorded at a recording wavelength λ and relatively movable along the scale direction, wherein a line at a predetermined position in the scale direction. -Shaped magnetoresistive effect element is equally divided into 2 ⁿ (where n = 2, 3, 4, ... ......) linear magnetoresistive effect pieces and electrically connected in series. , The positions of the 2 ⁿ magnetoresistive element pieces in the scale direction are: predetermined position ± {λ / (8 × 3)} ± {λ / (8 × 5)} ± {λ / (8 × 7) A magnetic sensor characterized in that it is set to ±± (λ / {8 × (2n−1)}] ± [λ / {8 × (2n + 1)}]. 2. The above 2 ⁿ is formed so as to form a continuous step.
The magnetic sensor according to claim 1, wherein the magnetoresistive element pieces are electrically connected in series. 3. A magnetoresistive effect element which is substantially equivalent to the magnetic sensor according to claim 2 and which has a shape of a smooth curve connecting the respective midpoints of the 2 ⁿ magnetoresistive effect pieces. And a magnetic sensor. 4. The position in the graduation direction of both ends of the magnetoresistive effect element having the shape of the curve from each midpoint of the magnetoresistive effect element is an average position in the graduation direction of the continuous stairs. 4. The magnetic sensor according to claim 3, wherein the magnetic sensor is substantially equal to. 5. The magnetic sensor according to claim 1, 2, 3 or 4, wherein a pair of magnetic sensors point-symmetric with respect to each midpoint thereof is provided, and the magnetic sensor side end of the pair of magnetic sensors is provided. Part or an end opposite to the magnetic scale is electrically connected, and the pair of magnetic sensors are inclined so as to be line-symmetric with respect to a direction orthogonal to the scale direction.