JPH01212313A - Magnetism detecting device - Google Patents

Abstract

PURPOSE:To restrict the consumption of current of a magnetism detecting device and also to enlarge the voltage of detected signals, by making a magnetoresistance stripe which is turned up to and from at least one time as a unit segment of a magnetoresistance element. CONSTITUTION:A magnetic reluctance element 39 has magnetoresistance stripes 31-38 each of which is turned up to and from at least one time, as a unit segment. A plurality of the magnetoresistance stripes are arranged in parallel with the distance lambda/4 every unit segment so that a lead wire from the unit segment is directed alternately in an opposite direction. The stripes of odd numbers in the unit segments of one phase are connected in series, and the stripes of even numbers are connected in series. Constant current sources 40-43 are provided so as to drive the magnetoresistance element 39. In this structure, when the magnetoresistance stripes 31-38 are driven by the constant current sources 40-43, and the magnetic recording medium 1 and the magnetoresistance element 39 are moved relatively, the magnetic signals received from the magnetic recording medium 1 are changed, and the resistance value is changed accordingly. Thus, the power consumption of the device can be reduced and moreover, the voltage of detected signals can be enlarged.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic detection device used in encoders and the like.

(Prior art) A magnetic detection device used in an encoder etc. uses a magnetic recording medium on which a repetitive signal of a constant wavelength λ is magnetized and recorded;
A magnetic detection device equipped with a magnetoresistive element having a magnetic stripe facing the magnetic recording medium,
The magnetoresistive element is formed using 2m (m is a natural number) magnetoresistive stripes arranged at intervals of 1/2)λ (n is a natural number) and connected in series as a unit segment.

A device characterized in that the magnetoresistive element is driven by a constant current source has been proposed. For example, as shown in FIG. 9, this magnetic detection device includes a magnetic drum 1, a magnetic resistance element 2.
It is composed of constant current sources 3 to 6 and a differential amplifier 7.8. The magnetic drum 1 is a magnetic recording medium in which a repeating signal of a constant wavelength λ is magnetized by alternately magnetizing N and S poles at regular intervals in the rotation direction, and the magnetoresistive element 2 has a plurality of Magnetoresistive (hereinafter referred to as MR) stripes 9 to 16
The lead-out terminals 17 to 20. Power terminal 21
．． 22 are provided. This MR Strive 9-16
faces the magnetic drum 1 and moves λ/2. in the direction of rotation thereof. λ/
4. λ/2. λ/8. λ/2゜λ/4. They are arranged at intervals of λ/2, one end connected to a DC power source of voltage Vc, and the other end connected to constant current sources 3 to 6, respectively. These MR stripes 9 to 16 are supplied with current I by constant current sources 3 to 6.
are supplied, and the resistance values Rtx(XL Riz(X)y Rti(
XL Rx4(X)t Rx5(XL Rts(XL
Rlt(XL Rx5(X) changes depending on the relative moving distance between the magnetic drum 1 and the MR element 2. Differential amplifier 7
is the voltage of constant current source 3.4 V ix (x) + V
t 4 (x), and the differential amplifier 8 performs differential amplification of the voltages v1 . (xLvi. When the magnetic drum 1 and the MR element 2, which perform differential amplification of (X), move relatively in the direction of the arrow, MR stripes 9 and 10, 11 and 12
The resistance value R, □(x) and Rtz(x), Rx1(x) and R14(X) change in opposite phases, and the resistance value Rtz(XLRta(X) of MR stripes 9 and 11 is 90
A sine wave eil(XL eB(x)) having a phase difference of 90° is obtained from the differential amplifier 7.8.

Now, assuming that the relative moving distance between the magnetic drum 1 and the MR stripe 9 is X, the resistance value R of the MR stripe 9 is
), the resistance value R of each MR stripe 10 to 16 is
tz(x)""Rx5(x) is expressed by the following formula.

Rig(X)=Rtx(X+λ/2)Rza(x)=
Rtz(x + 3λ/4)Rx4(x)=RLI
(X + 5λ/4) = Rtx (X + λ/4) Rzs (X ) = R11 (X + 11λ/8) = R
□, (x + 3λ/8) Rzs (x) = Rzz (x + 15λ/8)
= R11 (x + 7λ/8) Rzi (x) = Riz (x + 17λ/8)
=Rxt(X+λ/8) Ris(X)=Rlt(X+21λ/8)=R,
□(x+5λ/8) Also, the voltage of each constant current source 3 to 6 v□1(xL Vt*(x
LVzs()CL vts(x) is V, (x)=Vc (Riz(x)+Rxz(x))
xvx4(x)=Vc-(R,,(x)+R14(X)
) lVt5(X)=VC-(RLI(X)+RIS(
X))Ivis(x)=Vc-(R□,(x)+Rum
(X))I. When the amplification factor of the differential amplifiers 7 and 8 is 1, the output signals of the differential amplifiers 7 and 8 are all (XL et
a(x) is expressed as follows.

ext(x)=vti(x)-via(x)=(Ria
(x)+RtJx) Rxz(x)-Ryu1(X))
I”(Rtt(x+3λ/4)+R11(x+λ/
4)-R11(x+λ/2)-Rtt(x)) Iet
a(x)=vts(x)−via(x)=(Rtt(X
) + Rzs(x) Rts(x)-Rts(X))
I = (RLI(X+λ/8)+R11(x+5λ/8)−
R1□(x+7λ/8) −R1= (x+3λ
/8))I (Problem to be solved by the invention) In the above magnetic detection device, the MR stripes 9 to 16 are connected in series between the DC power source and the constant current sources 3 to 6, and the number of resistors is small. Since the value is small, the current consumption is large, and since the MR stripes 9 to 16 are spread out widely, the distance between the outer MR stripes and the magnetic drum 1 is large, and the signal magnetic field received from the magnetic drum 1 is small. .

The resistance value change is small and the detection signal voltage is small.

(Means for Solving the Problems) The present invention provides a magnetic detection device comprising a magnetic recording medium on which a repetitive signal of a constant wavelength λ is magnetized and recorded, and a magnetoresistive element facing the magnetic recording medium. The unit segment is a magnetoresistive stripe that has been folded back and forth at least once, and a plurality of unit segments are arranged in parallel at intervals of λ/4 so that the directions of leading wires from the unit segments are alternated. Odd-numbered units of the unit segments are connected in series, even-numbered units are connected in series, and a constant current source is provided for driving the magnetoresistive element.

(Function) The magnetoresistive stripe is driven by a constant current source, and when the magnetic recording medium and the magnetoresistive element move relative to each other, the resistance value changes as the magnetic signal received from the magnetic recording medium changes.

(Example) FIG. 1 shows an embodiment of the invention.

In this embodiment, the MR element 1-
In place of -, an MR element 39 composed of MR stripes 31 to 38 is used, and constant current sources 40 to 43 are used in place of constant current sources 3 to 6, and MR stripes 31 to 38 are used.
38 is a pair of MR stripes 31 and 32.33 and 34.
35, 36, 37, and 38 are connected in series, and one end of each is connected to a power supply terminal 44, 45, and the other end is connected to lead terminals 46 to 49, respectively. This M
R stripes 31 to 38 are each folded back and forth once and 2
MR stripe portions 311, 312...381
．． 382 are connected in series, and each of these two MR
Stripe portions 311, 312...381.382
The distance between the stripes is made close so that the change in resistance value with respect to the relative movement distance X with respect to the magnetic drum 1 can be approximated to be the same as that of one MR stripe without folding as in the conventional case.

The resistance value of such MR stripes 31 to 38 is twice that of a conventional single MR stripe without folding. Power supply terminals 44 and 45 of the MR element 39 are connected to a DC power supply of voltage VC, and lead-out terminals 46 to 4 of the MR element 39
9 are connected to constant current sources 40 to 43, respectively. This M
The R stripes 31 to 38 face the magnetic drum 1 and extend 31, 34 degrees 32, 33, 36, 37, 35 in the direction of rotation thereof.
．． 38 in the order of λ/4, λ/4. λ/4. λ/8. λ/4
．． The lead wires are arranged in parallel so that the lead-out directions are alternated at intervals of λ/4°.

Each resistance value of MR stripes 31 to 38 is R21 (X) ~
If Ra5(x) is set, the following equation holds true.

Ra1(x)=2 Rzt(x) R2! (x)= Rat (X+λ/2)=2Rt(x+λ/2) R23(X)= Rat (X+3λ/4)=
2 R1, (x + 3λ/4) Ras (X) = Rat (X + λ/4) = 2R (x + λ/4) Ras (X) = R2□ (x + 11λ/8) =
2 Jt(x+ 3λ/8) Rzs(x)=Rat(x+ 7λ/8)= 2 R,
, (x + 7λ/8) Ra7(X ) = Rzx (X + 9λ/8) = 2
R1□(X+λ/8) R,, (x)=R,, (x + 13λ/8)=2R1
i(x+5λ/8) In this embodiment, the resistance value of the MR stripes 31 to 38 is twice that of the magnetic detection device described above, and the constant current sources 40 to
The current value of 43 is λ/2, and the operation is the same as that of the magnetic detection device described above.

According to this embodiment, the spread of the arrangement of the MR stripes 31 to 38 is 13λ/8, which is 21
It is narrower by λ than λ/8, and a strong magnetic signal is applied from the magnetic drum 1 to the outer MR stripe, increasing the signal output. Furthermore, the MR stripes 31 to 38 have a large resistance value, resulting in small current consumption, and have a single layer structure without crossover, resulting in low cost.

FIG. 2 shows another embodiment of the invention.

In this embodiment, an MR element 59 composed of MR stripes 51 to 58 is used instead of the MR element 39 in the above embodiment, and constant current sources 60 to 60 are used instead of constant current sources 40 to 43.
The MR stripes 51 to 58 are a pair of MR stripes 51, 52, 53, 54, 55, 56, 57, and 58 connected in series, and one end of each is connected to a power supply terminal 64, 65. At the same time, the other ends are connected to the lead terminals 66 to 69, respectively. These MR stripes 51 to 58 are each folded back and forth twice to form four M stripes.
R stripe portions 511-514...581-58
4 are connected in series, and each of the four MR stripes 511 to 514...581 to 584 is widened and the gap between them is narrowed, so that the relative movement distance X with respect to the magnetic drum 1 is set as a solid arrangement. The change in resistance value can be approximated to be the same as that of one MR stripe without folding as in the prior art. Such MR stripes 51 to 58 have a resistance value of 1 without folding like the conventional one.
This is four times the number of MR stripes. Power supply terminals 64 and 65 of the MR element 59 are connected to a DC power supply of voltage Vc, and the MR element 59
The lead terminals 66 to 69 of the element 59 are each connected to a constant current source 7.
Connected to 0-73.

The MR stripes 51 to 58 face the magnetic drum 1 and extend 51.54, 52, 53° 57.55 degrees in the direction of rotation thereof.
, 58.56 in the order of λ/4. λ/4゜λ/4, 3λ/8
．． λ/4. λ/4. The lead line grooves are arranged in parallel at intervals of λ/4 so that the directions of the lead line grooves are alternated.

In this embodiment, the resistance value of the MR stripes 51 to 58 is four times that of the magnetic detection device described above, and the constant current sources 60 to 58 have four times the resistance value.
The current value of 63 is I/4, and the operation is the same as that of the magnetic detection device described above.

The MR stripe 51 has four MR stripe parts 511 to
514 are arranged at an interval of λ/16, and the resistance value of each of the four MR stripes 511 to 514 is expressed as Rzxx (XL
R3tz(XL Raxa(XL Rx, +(X)), the resistance value R1(X) of the MR stripe 51 is R21(X) = Rztz(X) + Rixi(X)+
R3xz(X)+R,□,(X) =Rzz(x-3λ/32)+R,,(X-λ
/ 32 ) + Rtz (X + λ/32) + Rut (
The same holds true for the other MR stripes 52 to 58, where X + 3λ/32).

Now, assume that the magnetic flux density component of the signal magnetic field parallel to the magnetic recording medium 1 is B(x)=B, +Ba 5in(2yc/λ)X. Here, 80 is the disturbance magnetic flux density, Ba is the amplitude of the signal magnetic flux density generated from the magnetic recording signal of the magnetic drum 1, and λ is the wavelength of the magnetic recording signal. The rate of change in resistance of the MR stripe with respect to the applied magnetic flux density is approximated to a quadratic curve as shown in Figure 3, and it is assumed that ρ(B(X))=A(B(x))''.ρ is the rate of decrease. In this case, the resistance value R1□(X) with respect to the relative moving distance X of the MR stripe is expressed as Rat(X) = Re (1-ρ(B (x))). When the magnetic flux density B(x) to be
p (B (x)) and Ra p (B (x)
) can be seen to decrease by @R11(X), Rtt(x) = R, (1-A(B, + Ba5
in(2x /λ)x)2) =Re (1-A (Ba” + Ba”/ 2 +
2B, Ba5in(2π/λ)x−(Ba”/2)co
s(4π/λ)X)). Similarly, Ra1t (X) = R11 (X - 3λ/32) =
Ro (1-A(Be2+ Ba”/2 + 2B,
Ba5in(2π/λ)(x-3λ/32)-(Ba
”/ 2) cos (4tc/λ) (X-3λ/32))
) R3xi (X)=Rzs (X-λ/32)=R
, CI A (Be” + Ba”/ 2 + 2
B, Ba5in (2s/λ) (X-λ/32) (B
a”/2)cos(4π/λ)(X-λ/32))) R,,3(x)=:R,(1-A(Bo”+Ba”/2
+ 2B, Ba5in (2π/λ) (x+λ/32)
(Ba”/ 2) cos (47C/λ) (X+λ/
32))) R3L4(X)=R, (1-A(B, "+Ba"/2+
2B, Ba5in(2π/λ)(x+3λ/32)−(
Ba”/2)cos(4x/λ)(X+3λ/32))
), and the resistance value R31(X) of the MR stripe 51 is R
3x (x) = Re [4-A (4Be” +
48a”/ 2 +2B, Ba(sin(2π/λ)(
x-3λ/32)+5in(2π/λ)(x+3λ/
32)+5in(2π/λ)(X-λ/32)+5in
(2π/λ)(X+λ/32)-(Ba”/2)(c
os(4tc/λ)(X-3λ/32)+cos(4
π/λ)(x+3λ/32)+cos(4tc/
λ)(X-λ/32)+cos(4tc/λ)(
X+3λ/32)))] =Re C4-A (4Be” + 4 B a”/
2 +28I, Ba(2sin(2tc/λ)xc
os(3π/16)+2sin(2π/λ) x co
syc/16)-(Ba2/2)(2cos(4x
/λ) x cos(3π/8)+2 cos(
4π/λ)xcos(π/8))] = Ra [4-A (4(Be” + Ba”/2
) +2BoBaX4sin(2g/λ)xX(c.

s3 xX 16 +cosπ/ 16)÷2−(Ba
”/2)X 4cos(4tc/λ)xX(cos
(3x/8)+cos(tc/8))÷2
))] =4 R@ [1-A (B o ” + B a”
/ 2 + 2BaBasin(2tc/λ)X
(cos3 tc/ 16 +cosπ/ l 6)
÷2−(Ba”/2) cos(4π/λ) x X(
cos(3xX8)+cos(π/8))÷2))] From the analysis of 0 or more, MR with resistance value R
When four stripes are arranged at an interval of xX16 and connected in series, the amplitude of the resistance change is as follows. Here, for example, 4 X (cos3?C/ 16 +cosg/ 16
) / 244 XO, 906 = 3.62 4X (cos3 π/8 + cos π/8) / 244xo
.

654=2.62, and the connection of these four MR stripes is 2
The π/λ component has an amplitude 3.62 times that of R11(X), and the 4π/λ component has an amplitude 2.62 times that of R11(X). Furthermore, the resistance value of the four MR stripes connected together is four times that of R1□(X) when the applied magnetic flux density is B(x)-0(B,=Ba=0). Furthermore, these four MRs
Compared to an MR stripe with a resistance value of R11(x), the connected stripes have exactly the same phase of resistance change when the center lines are aligned as shown in Figure 4, and the amplitude of the interaction of resistance change. It is possible to set R31(x)=4RLI(X) with only one difference.

Resistance value R32(X) to Rz of MRX drives 52 to 58
aCx) is expressed as follows.

R32 (X) = Rat (X + λ/2) = 4R1
1'(x+λ/2) R33(x)=Ra1(x+3λ/4)=4R
xz'(X+3λ/4) Ra4(X) = Rsz (X+λ/4)=4R1
1'(x+λ/4) R3s (X)= Rat (x+11λ/8)
=R,,(x+3λ/8) =4Ryu,'(x+3λ/8) R3s(x)=R31(x+15λ/8)−R,
, (x + 7λ/8) = 4R11' (x + 7λ/8) Rat (X) = R31 (X + 9λ/8) =
R3□(X+λ/8) =4Rtt'(X+λ/8) Ram (X)= Ram (X+13λ/8)
=Raz(x+5λ/8) =4R,,'(x+5λ/8) Therefore, the phase of the resistance change of the MR stripes 52 to 58 is the same as that of the MR stripes 9 to 58 in the magnetic detection device described above.
16, and the output signal e3□ of the differential amplifiers 7 and 8
(X), e, , CX) is the output signal e1□(X)e of the magnetic detection device described above.6. The phase is the same as □(X), but the amplitude is different. Further, as shown in FIG. 5, if each MR stripe part 511 to 514...581 to 584 is arranged at equal intervals and with the same width and gap, each MR stripe part 511 to 514---581 to 584 have the same sensitivity (p(B(x))=A (A of "B(x))" is the same), which eliminates distortion of the output waveform, which is desirable.

Depending on the application of the magnetic detection device, there may be cases where it is desired to further reduce the current consumption even if the spread of the MR stripe arrangement is a little wider than the above embodiment. In this case, an even number of MR stripes may be connected in series. For example, as shown in FIG. ~100
Four of them may be connected in series and the constant current sources 81 to 84 may supply a current of λ/8 to them. This MR
The stripes 85 to 100 are each folded back and forth twice, and constitute the MR element 101, facing the magnetic drum 1 and extending 85 degrees 89, 86, 90, 87 in the direction of rotation thereof.
,91,88,92,93.97,94,98,95,
λ/4 in the order of 99, 96, 100. λ/4. λ/4. λ
/4. λ/4, λ/4. λ/4, 3λ/8. λ/4. λ
/4°λ/4. λ/4. λ/4. λ/4. They are arranged in parallel so that the extraction directions are alternated at intervals of λ/4. Furthermore, depending on the application, the output signal may only be for one phase, and the present invention can be applied to this case as well. For example, as shown in FIG. , 103 between M
Two R stripes 104 to 107 may be connected in series, and current may be supplied to them by constant current sources 102 and 103. These MR stripes 104 to 107 are each folded back and forth once, and the MR element 108
10 facing the magnetic drum 1 in its rotating direction.
4, 105, 106, 107 in the order of λ/4. λ/4. λ
The differential amplifier 7, which is arranged in parallel at intervals of /4 so that the output directions of the lead line sources are alternated, performs differential amplification of the voltages of the constant current sources 102 and 103 to generate an output signal for one phase. Output.

FIG. 8 shows another embodiment of the invention.

This embodiment uses an MR element 119 consisting of MR stripes 111 to 118 in the embodiment shown in FIG.
111.113,112,1 in the direction of rotation facing the
14, 115. 117. 116, 118 in the order of λ/4.
λ/4. λ/4.3λ/8. λ/4. λ/4. They are arranged in parallel so that the extraction directions are alternated at intervals of λ/4. Two MR stripes 111 to 118 are connected in series, and one end of each is connected to a power terminal 120.12.
5 and the other end is connected to the lead terminal 121.
~ 124, power terminals 120 and 125 are connected to a DC power source, and lead terminals 121 to 124 are connected to a constant current source 4.
Connected to 0-43.

In this embodiment, MR stripes 111 and 112 are odd numbered and even numbered with power terminals 120 and 125 as boundaries.
, 113, 114, 115, 116, 117 and 118 are connected, but the operation is similar to the embodiment shown in FIG.

(Effects of the Invention) As described above, according to the present invention, in a magnetic detection device comprising a magnetic recording medium in which a repetitive signal of a constant wavelength λ is recorded once, and a magnetoresistive element facing the magnetic recording medium, the magnetic The resistance element has a unit segment of a magnetoresistive stripe folded back and forth at least once, and the unit segment is λ
A plurality of lead wire sources are arranged in parallel so that the directions of output from the unit segments are alternated at intervals of /4, and the odd-numbered ones of the unit segments for one phase are connected in series, and the even-numbered ones are connected in series. Since the magnetoresistive stripes located in the magnetoresistive stripes are connected in series and the magnetoresistive element is driven by a constant current source, the number of magnetoresistive stripes connected in series increases and the resistance value increases, reducing current consumption. Can be done. It is also possible to increase the detection signal voltage by reducing the extent of the arrangement of the magnetoresistive stripes.

[Brief explanation of the drawing]

1 and 2 are schematic diagrams showing each embodiment of the present invention, FIG. 3 is a characteristic diagram of an MR stripe, FIG. 4 and FIG. 5 are diagrams for explaining the above embodiment, and FIG. 6 8 to 8 are diagrams showing other embodiments of the present invention, and FIG. 9 is a schematic diagram showing an example of a magnetic detection device. 1...Magnetic recording medium, 31-38.51-58°85
~100,104~107,111~118...MR
Stripe, 39, 59, 101, 108° 119...
・MR element, 40~43.70~73°81~84,1
02,103... constant current source.

Claims (1)

[Claims] In a magnetic detection device comprising a magnetic recording medium on which a repetitive signal of a constant wavelength λ is magnetized and recorded, and a magnetoresistive element facing the magnetic recording medium, the magnetoresistive element has at least one magnetoresistive element.
The magnetoresistive stripes folded back and forth are used as unit segments, and a plurality of unit segments are arranged in parallel at intervals of λ/4 so that the directions of lead wires from the unit segments are alternated. A magnetic detection device characterized in that odd-numbered elements are connected in series, even-numbered elements are connected in series, and the magnetic resistance elements are driven by a constant current source.