JPH07151616A - Magnetostriction type torque sensor - Google Patents

Abstract

PURPOSE:To improve the detection sensitivity of a magnetostriction type torque sensor by concentrating magnetic fluxes 5 the magnetic thin film of a magnetostriction shaft. CONSTITUTION:A magnetostriction shaft 21 is constituted by using such a nonmagnetic austenitic metallic material as YHD50 (steel for hot metallic molds) as the base material 21A of the shaft 21 and forming a magnetic thin film 21B over the entire outer periphery of the base material 21A by thermally- spraying powder of such a magnetostrictive material as the iron-aluminum alloy, etc. Therefore, all magnetic fluxes from an exciting coil can be concentrated on the thin film 21B of the shaft 21 and the torque detecting sensitivity of a magnetostriction type torque sensor using the shaft 21 can be improved, because the magnetic fluxes do not intrude into the base material 21A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetostrictive torque sensor suitable for detecting, for example, an output shaft torque of an automobile engine, and more particularly to a magnetostrictive torque sensor capable of improving torque detection performance. Regarding sensors.

[0002]

2. Description of the Related Art In an automatic vehicle or the like equipped with an automatic transmission, it has been proposed to attach a magnetostrictive torque sensor to an output shaft or the like for the purpose of optimizing the shift timing of the automatic transmission.

Therefore, FIGS. 3 to 7 show a magnetostrictive torque sensor of this type according to the prior art.

In FIG. 1, reference numeral 1 denotes a casing which constitutes the main body of the torque sensor. The casing 1 is formed of a non-magnetic material into a stepped cylinder shape so as to be fixed to a case (not shown) of an automatic transmission or the like. It has become.

Reference numeral 2 denotes a magnetostrictive shaft rotatably disposed in the casing 1 via bearings 3 and 3. The magnetostrictive shaft 2 is made of carbon steel (SC) or nickel chrome steel (SN).
C), nickel chrome molybdenum steel (SNCM), chrome steel (SCr), chrome molybdenum steel (SCM), manganese steel (SMn), manganese chrome steel (SMn C), etc. Material 2A
And a magnetic thin film 2B formed of a magnetostrictive material such as an iron-aluminum alloy on the outer peripheral surface of the shaft base material 2A over the entire circumference. Both ends of the magnetostrictive shaft 2 project outside the casing 1 to form an output shaft. Further, the magnetic thin film 2B of the magnetostrictive shaft 2 is provided with a slit forming portion 2C located at an intermediate portion in the axial direction.
, Are engraved, and other slit grooves 5, 5, ... Are engraved obliquely upward at an angle of 45 °.

The slit grooves 4 and 5 are spaced apart from each other in the axial direction of the magnetostrictive shaft 2 by a predetermined distance, and are formed on the outer peripheral surface of the slit forming portion 2C at equal intervals over the entire circumference. Then, the slit forming portion 2C of the magnetostrictive shaft 2
A first magnetic anisotropic portion 6 is formed between the slit grooves 4 and a second magnetic anisotropic portion 7 is formed between the slits 5. 7, a magnetic path is formed by the surface magnetic field as shown by the dotted line in FIG.

Reference numeral 8 denotes a core member which is fixed to the inner peripheral surface of the casing 1 and surrounds the slit forming portion 2C of the magnetostrictive shaft 2 from the outside in the radial direction. The core member 8 is a stepped cylinder made of a magnetic material such as iron. Exciting and detecting coils 9 and 10 to be described later are arranged on the inner peripheral side thereof.

Reference numerals 9 and 10 denote exciting and detecting coils as first and second coils which are opposed to the magnetic anisotropic portions 6 and 7 of the magnetostrictive shaft 2 in the radial direction.
10 are provided on the inner peripheral side of the core member 8 via coil bobbins (not shown), and an AC voltage V is applied by an oscillator 13 described later to perform an exciting action and a detecting action. The exciting and detecting coils 9 and 10 have self-inductances L1 and L2 as shown in FIG. 6, and their iron loss and DC resistance are r1 and r2.

Reference numeral 11 denotes a magnetostrictive torque sensor detection circuit. This detection circuit 11 is a bridge circuit 1.
2. An oscillator 13 as an AC voltage applying means, a differential amplifier 14, a synchronous detection processing circuit 15 and the like. Here, the bridge circuit 12 is composed of excitation and detection coils 9 and 10 and adjustment resistors R and R, and a connection point a between the excitation and detection coils 9 and 10 and adjustment resistors R and R
A connection point b between Rs is connected to an oscillator 13 of an AC voltage V having a frequency f of about 30 kHz, for example. Further, the connection points c and d between the excitation and detection coils 9 and 10 and the adjustment resistors R and R are connected to the input terminals of the differential amplifier 14, respectively, and the detection voltage V from the excitation and detection coils 9 and 10 is detected.
1 and V2 are output to the differential amplifier 14. The output terminal 14A of the differential amplifier 14 is connected to the input side of the synchronous detection processing circuit 15 together with the oscillator 13, and the synchronous detection processing circuit 15 outputs the output voltage E0 from the differential amplifier 14 to the oscillator 13
The output voltage E of the direct current is output by rectifying in synchronization with the alternating voltage V from the output.

The magnetostrictive torque sensor of the prior art has the above-mentioned structure. Next, the manufacturing process of the magnetostrictive shaft 2 will be described with reference to FIG.

First, in the process I, the shaft base material 2A made of structural steel is heated to a temperature of, for example, about 750 to 900 ° C. to be quenched to give the shaft base material 2A a desired strength.

Next, in Process II, a magnetostrictive material such as an iron-aluminum alloy is sprayed on the outer peripheral surface of the shaft base material 2A over the entire circumference to integrally form the magnetic thin film 2B on the shaft base material 2A.

Then, in the process III, the magnetic thin film 2B that covers the entire outer circumference of the shaft base material 2A is subjected to surface processing, and magnetic anisotropic portions 6 and 7 are formed on the surface side of the magnetic thin film 2B. In order to do so, each slit groove 4 and 5 is machined.

Next, in Process IV, the entire magnetostrictive shaft 2 in which the slit grooves 4 and 5 are formed is, for example, 850 ° C.
It is heated to the front and back to perform magnetic annealing to remove processing strain from the magnetostrictive shaft 2 and reduce hysteresis.
Variation in output sensitivity and hysteresis for each magnetostrictive shaft 2 is reduced.

Next, the operation of the conventional magnetostrictive torque sensor will be described.

First, when the AC voltage V from the oscillator 13 is applied to the exciting and detecting coils 9 and 10, the magnetostrictive shaft 2
In the slit forming portion 2C, magnetic paths due to the surface magnetic field are formed along the magnetic anisotropic portions 6 and 7 between the slit grooves 4 and 5, respectively. In this case, the adjustment resistor R shown in FIG. 6 is used in the differential amplifier 14 when the torque acting on the magnetostrictive shaft 2 is zero.
The output voltage E0 is adjusted to zero.

Then, in this state, the magnetostrictive shaft 2 shown in FIG.
When torque acts in the T direction indicated by the arrow, the magnetostrictive shaft 2
In the slit forming portion 2C, the tensile stress + σ acts along the magnetic anisotropic portion 6 between the slit grooves 4, and the compressive stress −σ acts along the magnetic anisotropic portion 7 between the slit grooves 5. Therefore, when a positive magnetostrictive material is used for the magnetostrictive shaft 2,
In the magnetic anisotropic portion 6, the magnetic permeability μ increases due to the tensile stress + σ, and in the magnetic anisotropic portion 7, the magnetic permeability μ decreases due to the compressive stress −σ.

As a result, the exciting and detecting coil 9 arranged opposite to the magnetic anisotropic portion 6 of the magnetostrictive shaft 2 has a magnetic permeability μ.
As a result, the self-inductance L1 increases and the current i1 flowing through the exciting and detecting coil 9 decreases. on the other hand,
Exciting and detecting coil 1 arranged opposite to the magnetic anisotropic portion 7
In the case of 0, the self-inductance L2 decreases due to the decrease of the magnetic permeability μ, and the current i2 flowing through the exciting and detecting coil 10 increases. As a result, the detection voltage V1 from the excitation / detection coil 9 decreases and the detection voltage V2 from the excitation / detection coil 10 increases, so that in the differential amplifier 14,

[0019]

[Equation 1] E0 = A × (V1−V2) However, A: Amplification with an amplification factor is performed, and the AC output voltage E0 is output from the output terminal 14A of the differential amplifier 14 to the synchronous detection processing circuit 15. . Then, the synchronous detection processing circuit 15 operates the oscillator 13
The output voltage E0 is synchronously detected and rectified by the AC voltage V from the DC voltage V, and the DC output voltage E as shown in FIG. 6 is output as a detection signal corresponding to the torque acting on the magnetostrictive shaft 2.

Here, the relationship between the torque applied to the magnetostrictive shaft 2 and the output voltage E is expressed as a characteristic line 16 shown in FIG. 7, and the torque sensitivity at this time has an inclination θ, and when the torque is increased or decreased. The hysteresis is represented by the hysteresis width h.

[0021]

By the way, in the above-mentioned magnetostrictive torque sensor according to the prior art, the magnetostrictive shaft 2 is used.
Shaft base material 2A of carbon steel (SC), nickel chrome steel (SNC), nickel chrome molybdenum steel (SNC)
M), chrome steel (SCr), chrome molybdenum steel (SC
M), manganese steel (SMn), manganese chromium steel (SM
nC) and other magnetic structural steel, the magnetic paths from the excitation and detection coils 9 and 10 penetrate into the shaft base material 2A as shown by the dotted lines in FIG. There is a problem that the magnetic flux density inside 2B becomes small, and the torque detection sensitivity decreases.

The present invention has been made in view of the above-mentioned problems of the prior art. The present invention can concentrate the magnetic path in the magnetic thin film of the magnetostrictive shaft to increase the magnetic flux density and improve the detection sensitivity. The present invention aims to provide a magnetostrictive torque sensor.

[0023]

The features of the structure adopted by the present invention to solve the above-mentioned problems are that the magnetostrictive shaft comprises a shaft base material made of a non-magnetic austenitic metal material, and an outer periphery of the shaft base material. Is formed on the entire surface,
It is composed of a magnetic thin film made of a magnetostrictive material.

[0024]

With the above structure, since the shaft base material of the magnetostrictive shaft is formed of a non-magnetic austenitic metal material, the magnetic flux from the coil does not enter the shaft base material and the magnetic flux density on the magnetic thin film side is reduced. It can certainly be raised.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the embodiment, the same components as those of the conventional technique shown in FIGS. 3 to 7 are designated by the same reference numerals, and the description thereof will be omitted.

In the figure, reference numeral 21 denotes a magnetostrictive shaft used in the present embodiment, and the magnetostrictive shaft 21 is substantially composed of a shaft base material 21A and a magnetic thin film 21B, almost like the magnetostrictive shaft 21 described in the prior art. However, the shaft base material 21A of the magnetostrictive shaft 21 is formed of a non-magnetic austenitic metal material such as non-magnetic hot die steel (YHD50).

Now, the manufacturing process of the magnetostrictive shaft 21 will be described with reference to FIG.

First, in process 1, a shaft base material 21A made of YHD50 is prepared in advance, and a powder of a magnetostrictive material made of an iron-aluminum alloy is sprayed on the outer surface of the shaft base material 21A by plasma spraying on the shaft base material 21A. , The magnetic thin film 21 around the entire circumference of the shaft base material 21A.
Form B. In this case, since the shaft base material 21A made of YHD50 is substantially hardened by the heat treatment of the process 3 which will be described later, before forming the magnetic thin film 21B on the shaft base material 21A, it is preliminarily quenched as in the prior art. There is no need to apply.

The thickness t of the magnetic thin film 21B is

[0030]

[Equation 2] However, ρ: electric resistance W: external magnetic field angular velocity μ: magnetic permeability almost corresponds to the skin depth S, for example, 0.1 to 0.3 m
It is set to about m.

Next, in process 2, the magnetic thin film 21B is subjected to surface processing, and slit grooves (not shown) for forming magnetic anisotropy are formed on the surface of the magnetic thin film 21B by machining.

In the process 3, the magnetostrictive shaft 21
Is kept at about 700 to 1100 ° C. for 1 hour or more, and then cooled in an oil liquid to carry out magnetic annealing to remove work strain from the magnetostrictive shaft 21 or reduce hysteresis. Variation in output sensitivity and hysteresis for each magnetostrictive shaft 21 is reduced. Further, at this time, the shaft base material 21A is substantially quenched and hardness is increased.

The magnetostrictive shaft 21 used in this embodiment has the structure described above, and its basic operation is not different from that of the prior art.

In this embodiment, however, the shaft base material 21
By forming A from a non-magnetic austenitic metal material such as YHD50 and spraying a magnetic thin film 21B made of a magnetostrictive material such as an iron-aluminum alloy on the outer peripheral surface of the shaft base material 21A, Since the magnetostrictive shaft 21 is configured, as shown in FIG. 1, the magnetic flux from the exciting coil does not enter the shaft base material 21A which is a non-magnetic material, and the magnetic thin film 21B of the magnetostrictive shaft 21 is prevented.
The magnetic flux can be concentrated to increase the magnetic flux density, whereby the torque detection sensitivity of the magnetostrictive torque sensor can be improved, and the inclination θ ₁ can be increased as shown by the characteristic line 22 shown by the dotted line in FIG.

Further, since the shaft base material 21A is formed of YHD50, magnetic annealing for the magnetic thin film 21B and quenching for the shaft base material 21A can be performed by the same heat treatment in process 3 shown in FIG. Can be simplified and the cost can be reduced accordingly.

In the above embodiment, the shaft base material 21
Although the magnetic thin film 21B is formed by spraying a magnetostrictive material such as an iron-aluminum alloy onto A, the present invention is not limited to this, and for example, the shaft base material 21A.
An alloy such as permalloy may be used as the magnetostrictive material thermally sprayed on.

[0037]

As described in detail above, according to the present invention, the magnetostrictive shaft is formed over the entire circumference of the shaft base material made of a non-magnetic austenitic metal material and the outer peripheral surface of the shaft base material. The magnetic flux from the exciting coil can be prevented from entering the inside of the shaft base material, which is a non-magnetic material, by concentrating the magnetic flux from the coil on the magnetic thin film of the magnetostrictive shaft. The density can be increased, and the torque detection sensitivity of the magnetostrictive torque sensor can be improved.

[Brief description of drawings]

FIG. 1 is a lateral cross-sectional view showing an enlarged main part of a magnetostrictive shaft used in a magnetostrictive torque sensor according to an embodiment of the present invention.

FIG. 2 is a process explanatory view showing a manufacturing process of the magnetostrictive shaft shown in FIG.

FIG. 3 is a vertical sectional view of a magnetostrictive torque sensor according to a conventional technique.

FIG. 4 is a transverse cross-sectional view showing an enlarged main part of the magnetostrictive shaft in FIG.

FIG. 5 is a process explanatory view showing a manufacturing process of a magnetostrictive shaft according to a conventional technique.

FIG. 6 is an electric circuit diagram showing a detection circuit of the magnetostrictive torque sensor shown in FIG.

FIG. 7 is a characteristic diagram showing the relationship between the torque acting on the magnetostrictive shaft and the output voltage from the detection circuit.

[Explanation of symbols]

 1 Casing 9 and 10 Excitation and detection coil (coil) 21 Magnetostrictive shaft 21A Shaft base material 21B Magnetic thin film

Claims (1)

[Claims] 1. A tubular casing, a magnetostrictive shaft rotatably arranged in the casing, and first and second magnetism shafts located radially outside the magnetostrictive shaft and provided on the casing side. In the magnetostrictive torque sensor including a coil, the magnetostrictive shaft is formed over the entire circumference of the shaft base material made of a non-magnetic austenitic metal material and the shaft base material, and made of a magnetic material made of a magnetostrictive material. A magnetostrictive torque sensor comprising a thin film.