JPS6344730Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a displacement detection device that magnetically detects minute displacements and the like using a magnetoresistive element that utilizes the ferromagnetic magnetoresistive effect.

Magnetoelectric transducers whose output voltage changes in response to a magnetic field are used in magnetic scales, magnetically set point reading devices, frequency generators for rotation control of motors, etc.
It is also widely used in the fields of measuring instruments and consumer equipment, such as non-contact switches and non-contact volumes. The above-mentioned magnetoelectric transducer includes a ferromagnetic magnetoresistive element based on a magnetic sensing principle that uses the ferromagnetic magnetoresistive effect of a ferromagnetic metal, a semiconductor magnetoresistive element that uses the semiconductor magnetoresistive effect of a semiconductor, or a hole-based magnetoresistive element that uses the semiconductor magnetoresistive effect of a semiconductor. Elements and the like have been known in the past.

The ferromagnetic magnetoresistive effect of ferromagnetic metals can be roughly divided into two types of effects, the first of which is a resistance change that occurs through a change in spontaneous magnetization due to an external magnetic field, and is explained by Mott's theory. be able to. Generally, this first effect is a negative magnetoresistive effect in which the resistance decreases linearly as the magnetic field increases, and is isotropic with respect to the direction of the magnetic field. 1st above
The effect becomes large near the Curie temperature, where spontaneous magnetization is intense, but unless a large magnetic field is applied,
Usually can be ignored. The second effect is observed in a relatively small magnetic field, and the resistance changes in different directions depending on the angle formed between the magnetization direction and the current direction. This second effect is
The temperature change in spontaneous magnetization is large in the temperature range where it is small;
It becomes smaller towards the Curie temperature. For general ferromagnetic metals, such as NiCo alloy, NiFe alloy, NiAl alloy, NiMn alloy, or NiZn alloy,
When the current path section 1 is formed as shown in Fig. 1, its resistance value ρ (θ) is maximum when the current and magnetization direction are parallel, and minimum when the direction of magnetization is perpendicular to ρ. (θ)=ρ⊥·sin ² θ+ρ·cos ² θ The second effect can be expressed by the Viogt-Thomson equation, which is the first equation. Here, in the first equation,
θ is the angle between the current I and the saturation magnetization M, and ρ⊥
is the resistance when the current I and the saturation magnetization M are orthogonal, and ρ is the resistance when the current and the saturation magnetization are parallel. Therefore, a highly sensitive magnetoresistive element can be manufactured by utilizing the second effect.

For example, as shown in FIG. 1, both terminals 2a,
A bias current I _B is applied from a constant current source 3 between 2b,
When magnetic fields H ₁ and H ₂ having different directions are applied to the current path portion 1 with a boundary line 4 crossing the current path portion 1, the following conversion characteristics are obtained.

In other words, if x is the length to which the magnetic field H ₁ is applied at an angle of θ ₁ with respect to the direction of the bias current I _B , then the length of the region to which the magnetic field H ₂ is applied, also at an angle of θ ₂ When y is the resistance value R of both terminals 2a and 2b of the current path section 1, R=x(ρ⊥sin ² θ ₁ +ρcos ² θ ₂ ) +y(ρ⊥sin ² θ ₂ +ρcos ² θ ₂ ) The boundary line 4 changes depending on the position where the boundary line 4 crosses the current path section 1.

The present invention provides a magnetoelectric conversion device that performs a conversion operation corresponding to the amount of relative displacement between a magnetoresistive element and a magnetizing part using the ferromagnetic magnetoresistive effect as described above. It can be easily implemented using magnets of commonly available shapes.

Hereinafter, the present invention will be described in detail with reference to the drawings showing one embodiment.

In the embodiment shown in FIG. 2, a magnetoresistive element 10 having a current passage section 11 made of ferromagnetic metal is connected to three cylindrical magnets 12, respectively.
It is arranged on a plane including the central axis 14 in the cylindrical hollow part 13 of the magnetizing part 12 which is made up of the magnetizing part 12 arranged in series, and is provided so as to be freely displaceable relative to the magnetizing part 12. 3 constituting the magnetizing section 12
As shown in FIG. 3, the magnet 12B placed in the center of the magnets 12A, 12B, and 12C has its outer peripheral surface 12b side magnetized to the N pole.
The inner circumferential surface 12a side thereof is magnetized to the S pole, and a radial magnetic field H _B is generated within the cylindrical hollow portion 13.
In addition, as shown in FIG. 4, the other two magnets 12A and 12C have their joint end surfaces 12d and 12e with the magnet 12B in the central portion magnetized to the S pole, respectively, and the other end surfaces 12f and 12g. The sides are each magnetized to the N pole, and the shaft 1 is located inside the cylindrical hollow part 13.
Generates parallel magnetic fields H _A and H _C in four directions. Here, the total length L ₎ of the magnetizing section 12 in the axis 14 direction is relative to the total length l ₀ of the current path section 11 of the magnetoresistive element 10 .
It has a length of at least 2·l ₀ or more, and
The axial length L ₁ of the magnet in the central portion is set to be less than l ₀ . In this embodiment, L ₁ =1/2l ₀ . Therefore, each of the magnets 12A, 12
Hollow part 13 of magnetizing part 12 composed of B and 12C
A magnetic field H B in a direction perpendicular to the current path portion 11 is applied to the magnetoresistive element 10 disposed within the magnetoresistive element 10 by the magnet 12B in the central portion, and a magnetic field H _B in a direction parallel to the current path portion 11 is applied to the magnetoresistive element 10 disposed within The magnetic fields H _A and H _C are provided by the other two magnets 12A and 12B.

The magnetoresistive element 10 arranged in the hollow part 13 of the magnetizing part 12 having the above-described structure is connected to the current passage part 11 of the magnetoresistive element 10.
It operates as a potentiometer with the midpoint of the output terminal 11a as the output terminal 11a, and outputs a conversion output corresponding to the axial position within the hollow portion 13 from the output terminal 10a. Note that a constant voltage from a constant voltage source (not shown) is applied between both terminals 11b and 11c of the magnetoresistive element 10, thereby causing a constant bias current I _B to flow.

According to the present invention, a magnetoresistive element that utilizes a ferromagnetic magnetoresistance effect, a cylindrical magnet that generates a magnetic field parallel to the axis, and a cylindrical magnet that generates a radial magnetic field are connected in the axial direction. and a magnetoresistive part, the magnetoresistive element being disposed in a cylindrical hollow part of the magnetizing part so as to be freely displaceable relative to the magnetizing part in the axial direction, Stable magnetic fields with different directions from the respective cylindrical magnets are applied to the magnetoresistive element within the cylindrical hollow part of the magnetization section to perform a magnetoelectric conversion operation with good linearity. A magnetoelectric transducer can be provided using a simple magnetizing section using a shaped magnet and a magnetoresistive element using a ferromagnetic magnetoresistive effect.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram for explaining the operating principle of a magnetoresistive element using the ferromagnetic magnetoresistive effect. FIG. 2 is an external perspective view showing an embodiment of the magnetoelectric transducer according to the present invention. Figures 3 and 4
The figures are a longitudinal sectional side view and a lateral plan view of the magnetizing section in this embodiment. 10... Magnetoresistive element, 11... Current path section, 1
2, 22...Magnetizing part, 12A, 12B, 12C, 2
2A, 22A', 22B, 22B', 22C, 22
C′...Magnet, 13...Hollow part, 14, 24...Axis center.

Claims (1)

[Scope of Claim for Utility Model Registration] A magnetoresistive element that uses ferromagnetic magnetoresistive effect, a cylindrical magnet that generates a magnetic field parallel to the axis, and a cylindrical magnet that generates a radial magnetic field are connected in the axial direction. a magneto-electric transducer comprising a magneto-generating section, the magnetoresistive element being disposed in a cylindrical hollow part of the magneto-generating section so as to be freely displaceable relative to the magneto-generating section in the axial direction. .