JPS61173113A - Magnetic rotation sensor - Google Patents

Abstract

PURPOSE:To improve signal output and to reduce electric power consumption by disposing three pieces of sensing parts consisting of thin film magnetoresistance elements in parallel then connecting these sensing parts in series to constitute one set and forming such sensing parts on the same substrate in such a manner that the corresponding sensing parts parallel with each other. CONSTITUTION:The magnetic rotation sensor has the sensing parts MR5...MR10 of the thin film magnetoresistance element 15 formed on the insulating substrate 14. MR5, MR6 and MR7 among these sensing parts are arrayed in parallel at the interval of the wavelength of 1/3 the recording wavelength lambda of a signal magnetic field and are connected in series. MR8, MR9 and MR10 are also arrayed in parallel at the spacing of 1/3 the wavelength. The set of MR5, MR6 and MR7 and the set of MR8, MR9 and MR10 are arrayed at the spacing of 1/2 the wavelength in such a manner that the corresponding sensing parts parallel with each other. Two sets thereof are connected in parallel. The magnetic rotation sensor is thus prevented from being superposed with 1/2 the source voltage with the signal output as in the conventional practice and the signal output is improved 4/3 times. The electric power consumption is reduced to 2/3.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention uses a thin film magnetoresistive element to detect the rotation speed, rotation angle, and rotation direction of a rotating body such as a capstan motor of a video tape recorder (VTR). This relates to a magnetic rotation sensor.

(Summary of the invention) The present invention provides a magnetic rotation sensor that detects the rotation speed, rotation direction, etc. of a rotating body using a thin film magnetoresistive element whose resistance value changes due to a magnetic field repeatedly recorded at a constant wavelength.
Three sensing parts are formed on a thin film magnetoresistive element and connected in series, and two sets are connected in parallel and formed on the same substrate. The detection output of a one-rotation signal is increased by creating a specific relationship with the recording wavelength and applying a bias magnetic field to each sensing portion of the thin film magnetoresistive element.

Moreover, power consumption is reduced.

[Conventional technology]

A magnetic rotation sensor using a thin film magnetoresistive element.

As shown in the 4th WI, a recording medium 2 made of a plastic magnet or the like magnetized and recorded at a constant wavelength is attached to the outer periphery of the rotor 1, and a magnetic rotation sensor 3 made of a thin film magnetoresistive element is placed opposite to this recording medium 2. are doing.

The system is configured to detect the number of rotations, the direction of rotation, etc. of the rotor by utilizing the fact that the resistance value of the thin film magnetoresistive element changes due to changes in the magnetic field accompanying the rotation of the rotor 1, which is a rotating body. It is something.

Figure 5 shows the pattern of a thin film magnetoresistive element on a substrate of a conventional magnetic rotation sensor.A material such as NiFe alloy, NiCo alloy, etc. whose resistance value changes depending on the magnetic field is placed in a vacuum on an insulating substrate 4 made of glass or the like. A thin film magnetoresistive element S is obtained by forming a thin film using a method such as vapor deposition and patterning it into a predetermined shape using a photoetching technique.

This thin film magnetoresistive element 5 includes sensing parts M R1, M R2, M R3, M R4 for detecting a signal magnetic field, and a terminal part 6.
a Consists of P6b, 5e, and 5d. Here, the sensing part M R
1° MR2, MR3, and MR4 are arranged at intervals of 1/4 of the recording signals N and S alternately recorded at a constant wavelength λ on the recording medium 2 on the outer circumference of the rotor 1, as shown in FIG. ing.

As shown in FIG.
I and MR3 are connected in series to form a set of thin film magnetoresistive elements, the connection part is used as the signal output terminal 6d, and both ends 6
at 6G is used as the power supply terminal, and similarly, the sensing parts MR2 and MR4 are connected in series to form a set of thin film magnetoresistive elements, the connection part is used as the signal output terminal 6b, and both ends are used as the sensing part MRI. It is used as a common power supply terminal with the thin film magnetoresistive element consisting of MR3.

Furthermore, as shown by the broken line in FIG.
A bias magnet 7 for applying a bias magnetic field to R4 is
It is attached to the back surface of the insulating substrate 4 when viewed from the thin film magnetoresistive element 5 .

The magnetic rotation sensor configured in this manner is electrically connected as shown in FIG.

Here, a circuit in which two resistors 8 having a resistance value equal to that of the sensing units MRI, MR2, MR3, and MR4 are connected in series is connected in parallel to the power supply terminals 6a and 5c of the sensing units MRI to MR4 to form a bridge configuration. A power supply voltage Vcc is applied to both ends thereof.

The connection point between the two resistors 8 and 8 is connected to the two differential amplifiers 10. each one input side of it. Further, the signal output terminals 6d of the sensing units MRI and MR3 are connected to the other input side of the differential amplifier 10.

The signal output terminals 6b of MR2 and MR4 are respectively connected to the other input side of the differential amplifier 11. And output terminal A of each differential amplifier 10.11.

The output signal is obtained from B.

Next, the operating principle of this magnetic rotation sensor will be explained.

As shown in FIG. 9, when a magnetic field is applied to the thin film magnetoresistive element MR in a direction H perpendicular to the current direction.

The resistance value changes as shown in FIG. Sensing part M
A bias magnetic field is applied to R1, M R2, M R3, and M R4 by a bias magnet 7, and a bias point is set near the center P of a range a where the resistance value changes almost linearly.

The bias magnetic field at this time can be applied in a direction perpendicular to the longitudinal direction of the sensing units MRI to MR4, or
It is added by a method of adding in a direction that can be vector-decomposed into a direction parallel to the longitudinal direction of I to MR4 and a direction perpendicular to the direction.

Therefore, when the rotor 1 shown in FIG. 6 rotates, the signal output terminal 6d of the circuit shown in FIG. 8 receives an output E3 as shown in FIG. 11, and the output E3 shown in FIG.
4 is obtained.

[Problem that the invention seeks to solve]

However, in such a conventional magnetic rotation sensor, since 172 of the power supply voltage Vcc is added to the signal output,
As shown in Fig. 8, it is necessary to have a bridge configuration with resistors 8, 8, and to detect the rotation signal as a potential difference between the connection point S of resistors 8, 8 and the signal output terminal 6d or 6b. . Therefore, an external resistor is required, which further increases power consumption.

Furthermore, if the resistors 8, 8 in FIG. 8 were to be placed on the same insulating substrate as the thin film magnetoresistive element 5, there would be a problem in that the routing of the lead wire pattern would become complicated and the number of connection terminals would increase. .

This invention was made to solve the problems of the conventional ones as described above, and a bridge is constructed on the same insulating substrate by simple pattern routing.

An object of the present invention is to provide a magnetic rotation sensor that can reduce power consumption and improve signal output.

[Means for solving problems]

In order to solve the above-mentioned problems, the magnetic rotation sensor according to the present invention approaches a signal magnet recorded at a constant wavelength on the outer periphery of the rotor, and detects a signal at a distance between three sensing sections made of thin film magnetoresistive elements. One set consists of devices arranged in parallel and connected in series so as to correspond to 1/3 of the recording wavelength of the magnetic field, and two sets of these are connected in parallel, so that the corresponding sensing parts are parallel to each other and the distance between them is equal to the signal. The thin film magnetoresistive elements are formed on the same substrate so as to have a magnetic field of half the recording wavelength, and a bias magnetic field is applied to each sensing portion of this thin film magnetoresistive element.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 shows the configuration of a magnetic rotation sensor which is an embodiment of the present invention.
, MRIO is a sensing section of a thin film magnetoresistive element 15 formed on an insulating substrate 14, of which MR5°, MR6,
The M R7s are arranged in parallel and connected in series at intervals of 1/3 wavelength of the recording wavelength λ of the signal magnetic field.

Similarly, M R6, M R7, and M R8 are arranged in parallel with an interval of 173 wavelengths, and the corresponding sensing parts of the set of M R5, M R6, and M R7 and the set of MR8, MR9, and MRIO are parallel to each other. Arranged at intervals of 172 wavelengths.

These two sets are connected in parallel.

Then, connect terminals 17b and 17e to the power source.

Signals are output from terminals 17a, 17c, 17d, and 17f.

Furthermore, a bias magnetic field HB (indicated by an arrow HB in the figure) is applied to each sensing portion of the thin film magnetoresistive element 15 in a direction that can be vector resolved into a direction parallel to the longitudinal direction of the sensing portion and a direction perpendicular to the sensing portion. , which is obtained by the magnet 16 attached to the back surface of the insulating substrate 14.

This magnetic rotation sensor is electrically connected as shown in FIG. Detected by 1st, output terminal A,
Connect and use it so that the rotation signal is obtained from B.

Next, the operating principle of this embodiment will be explained.

The sensing units MR5 to MRIO to which the bias magnetic field is applied are
As shown in FIG. 10, the bias is set near the center P of the range a in which the resistance value changes approximately linearly.

Sensing units MR5 to MRIO in which vias are not set in this way
As in the conventional case, a signal magnetic field magnetized and recorded on the outer circumference of the rotor 1 acts on the rotor 1.

When the rotor rotates, a signal magnetic field of a certain wavelength is generated at the sensing part MR5.
～MRIO acts in forward and reverse directions perpendicular to the longitudinal direction of the MRIO, and the resistance values of the sensing parts MR5～MRIO are centered around the resistance value R when no signal magnetic field is applied, and approximately change with respect to the rotation angle of the rotor. The vibration changes in a sinusoidal manner,
Approximately R=R, +ΔR51nθ=io (i+(Δ
R/R□) sin θ). Here, ΔR sin θ is the resistance value change of the magnetoresistive element due to the signal magnetic field in FIG. 10, and θ is the rotation angle of the rotor when the recording wavelength λ of the signal magnetic field is replaced with 2π.

Therefore, based on the resistance value of the sensing part MR5, the position is 173 wavelengths apart with respect to the recording wavelength λ=2π of the signal magnetic field,
and sensing units MR6 and MR7 arranged at 1/2 wavelength intervals.
, MR8, MR9, MRIO resistance change due to signal magnetic field is RMz=Ro (1+(ΔR/R□)sinθ)R
cicada g=RO(1+(ΔR/RO) sin(θ−near c/
3)) RsKT=Ro (1+(ΔR/RO) sin
(θ−4g/3))RM(t=Ro(1+(ΔR/
R□ ) sin (θ−π)) RHRt:Ro (1+
(ΔR/RO) sin (θ-sπ/3)) Rsx+o=
Rg (1+(ΔR/RO)gin(θ-7g/3)
), the total resistance of the set of sensing units MR5 to MR7 connected in series is 3Ro, and similarly the sensing units MRa to MRIO
The total resistance of the set is also 3R.

Therefore, when the power supply voltage Vcc is applied between the terminals 17b and 17e, even if the signal magnetic field changes due to the rotation of the rotor, the combination of sensing parts M R5, M R6, M R7 and the sensing parts M R8, M R9, The current shunted to the MRIO set does not change and remains constant.

On the other hand, the voltage E1 at the signal output terminal 17a, which is the connection between the sensing parts MR5 and MR6, is as follows.

=1/3 (2-(ΔR/R□)sinθ)・vcc
becomes.

Also, the voltage E2 of the signal output terminal 17c, which is the connection between the sensing parts MR8 and MR9, is = 1/3 (2+(ΔR/R□) sin θ)・vcc
becomes.

Therefore, when the voltage difference between the signal output terminals 17a and 17c is extracted as the output signal ΔEa, ΔEa=E1-E2=1/3 [(2-(ΔR/RO)sinθ)-(2+
(ΔR/R□)ginθ)]・vcc knee (2ΔR/
3RO) Vcc sin θ −(1) is obtained.

Moreover, the voltage E3 of the signal output terminal 17f, which is the connection between the sensing parts MR6 and MR7, is = 1/3 (1+(ΔR/R□) sin(θ−4π/
3)) ・Vcc, and the voltage E4 of the signal output terminal 17d, which is the connection between the sensing unit MR9 and MRIO, is = 1/3 (1+(ΔR/R□) sin(θ-'7c
/3)) ・Vce.

Therefore, if the voltage difference between the signal output terminals 17f and 17d is extracted as the output signal ΔEb.

ΔEb=E3-E4 =1/3 ((1+(ΔR/R□) sin(θ-4t
c / 3) ) - (1 + (ΔR/Ro) sin (θ - 7
π13))]・vcc=(2ΔR/3Rg)Vcc-
cog(θ+π/6)=-(2ΔR/3R□)Vcc
-sin(θ+2 tc /3) (2) The rotation signal outputs shown by equations (1) and (2) are obtained.

Figure 3 shows this output signal waveform, and the output ΔEb is the output Δ
A signal whose phase is advanced by 2π/3 with respect to Ea is obtained,
If the rotational direction of the rotor is reversed, ΔEb becomes a signal whose phase is delayed by 2π/3 with respect to ΔEa, so that the rotational direction as well as the rotational speed or rotational angle of the rotor can be detected.

On the other hand, the power consumption of the magnetic rotation sensor having such a configuration is W1=2 Vcc"/3 Rg-(3).

On the other hand, in the conventional magnetic rotation sensor shown in FIG. 5, the bias magnetic field HB is directed in a direction that can be vector-resolved in a direction perpendicular to a direction parallel to the longitudinal direction of the sensing parts MRI to MR4, as in the above embodiment. When the signal magnetic field is applied, the resistance value change of the sensing part due to the signal magnetic field is R:=Ro (i+(ΔR/R
o) sinθ)R=1g (i+(ΔR/R(1)s
in(θ−π))Rsxz=R, (1+(ΔR/R□
) sin (θ−π/2)) RMR4=RO(1+(ΔR
/R□)sin(θ-3π/3)), and MRl
The voltage E3 of the signal output terminal 6d which is the connection part between and MR3
is E3=1/2 (1+(ΔR/R□)sinθ) ・
Vcc -(4), and the voltage E4 at the signal output terminal 6b, which is the connection between MR2 and MR4, is E4 = 1/2 (1+(ΔR/R□) sin(θ-
3π/2))・vCc...(5)

The power consumption of a magnetic rotation sensor with such a conventional configuration is W 2 = Vcc” / Ro − (6
). Moreover, if a bridge circuit as shown in FIG. 8 is constructed, power consumption will further increase.

In addition, in the above embodiment, the direction of the bias magnetic field was applied in a direction that can be vector resolved into a direction parallel to the longitudinal direction of the sensing section and a direction perpendicular to the direction, but by applying the bias magnetic field in a direction perpendicular to the longitudinal direction of the sensing section, It may be set at the bias point P in FIG.

Further, in the above embodiment, the sensing portion is formed into a folded shape, but the same effect can be obtained even if the sensing portion is not formed into a folded shape.

Furthermore, in the above explanation, the sensing part MR5゜MR
6, M R7 interval is 1/3 of the recording wavelength λ of the signal magnetic field, M R8, M R9, M RIO are M R5, M
R6° was set to be shifted by 1/2 of the recording wavelength λ with respect to MR7, but even if these intervals vary somewhat.

The current flowing through the sensing section changes slightly, and the phase of the change in resistance value shifts slightly, resulting in a slight drop in the output voltage.

〔Effect of the invention〕

As explained above, the magnetic rotation sensor according to the present invention differs from the conventional example in that the magnetic rotation sensor has a power supply voltage Vcc of 1
/2 is not superimposed, the signal output is increased by 4/3 times, and the power consumption is further reduced by 2/3. Moreover, no external resistor is required, and it can be realized with a relatively simple pattern configuration on a single substrate.

[Brief explanation of the drawing]

FIG. 1 is an enlarged plan view showing a pattern configuration of a thin film magnetoresistive element on a substrate of a magnetic rotation sensor showing an embodiment of the present invention. FIG. 2 is a circuit diagram of the magnetic rotation sensor, and FIG. 3 is a diagram showing changes in output voltage with respect to the rotor rotation angle by the magnetic rotation sensor. Fig. 4 is a perspective view showing the positional relationship between the rotor and the magnetic rotation sensor, Fig. 5 is an enlarged plan view similar to Fig. 1 of the conventional magnetic rotation sensor, and Fig. 6 is the same as that of the sensing part and the outer circumference of the rotor. An explanatory diagram showing a relationship with a signal magnetic field. FIG. 7 and FIG. 8 are circuit diagrams showing the connection relationship of a conventional magnetic rotation sensor. FIG. S is an explanatory diagram for explaining the operation when a magnetic field is applied to a thin film magnetoresistive element. FIG. 10 is a diagram showing a change in resistance when a magnetic field is applied to a thin film magnetoresistive element, and FIG. 11 is a diagram showing a change in output voltage with respect to a rotor rotation angle of a conventional magnetic rotation sensor. 1... Rotor 2... Magnetic signal recording medium 3... Magnetic rotation sensor 14... Insulating substrate 15.
...Thin film magnetoresistive element MRI-MRIO...Sensing section 16...Bias magnetic field magnet 17, ~17f...Terminal 18.19...Differential amplifier Fig. 1 Fig. 2 Fig. 3 Fig. 5 Figure 6 Figure 7 Figure 8 Figure 11 Procedural amendment (1. September 17, 1985, Director General of the Japan Patent Office, Michibu Uga, 1, Indication of Case Patent Application No. 12688-1988, 2) Name: Magnetic rotation sensor 3, person making the amendment Relationship to the case Patent applicant: 2-12-14 Higashikojidani, Ota-ku, Tokyo (002) Akai Electric Co., Ltd. 4, Agent: 5-6, 1-20 Higashiikebukuro, Toshima-ku, Tokyo , rR=Ro (1+(ΔR/Ro)sinθ)R=R on page 13, lines 19-20 of the specification of contents of amendment
o (1+(ΔR/RO)sin(θ−π))”. IrRMNI = Ro '(1+ (ΔR/R□)g
inθ)R north3=Ro (1+(ΔR/RO)sin
(θ−π))”. that's all

Claims (1)

[Claims] 1 A thin film magnetoresistive element whose resistance value changes due to a magnetic field repeatedly recorded at a constant wavelength is provided with three sensing parts,
The three sensing parts are arranged in parallel and connected in series so that the interval is 1/3 of the recording wavelength of the signal magnetic field, and the signal output terminal is pulled out from each connection part of the three sensing parts, and the signal output terminal is pulled out from both ends. Two sets are connected in parallel, and the corresponding sensing parts are parallel to each other and the distance is 1/2 of the recording wavelength of the signal magnetic field on the same substrate. 1. A magnetic rotation sensor characterized in that a magnet is attached to the back surface of the substrate to apply a bias magnetic field to each sensing portion of the thin film magnetoresistive element.