JPH07157825A - Production of magnetostrictive shaft - Google Patents

Abstract

PURPOSE:To produce a magnetostrictive shaft capable of reducing hysteresis and improved in sensitivity. CONSTITUTION:A heating stage for a shaft material 21 is done by performing heating at 800-900 deg.C for about 1hr in a state where an airtight chamber 22 is filled with argon gas of about 500-600Torr. Further, an oil quenching stage is done by immersing the shaft material 21 in a heated state into an oil liquid 17 in the airtight chamber 22 with argon atmosphere. The oxidation and nitriding of a thin magnetic film 2B on the surface of the shaft material 21 can be prevented and also the increase of hysteresis can be prevented, and further, cooling velocity for the shaft material 21 is increased and high torque detection sensitivity can be provided to the shaft material 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetostrictive shaft which is suitable for use in a magnetostrictive torque sensor for detecting the output shaft torque of an automobile engine, and more particularly, to improve the torque detection performance. The present invention relates to a method for manufacturing a magnetostrictive shaft.

[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 8 show a magnetostrictive torque sensor according to this type of 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. As shown in FIG. 4, the magnetostrictive shaft 2 is made of carbon steel (SC) or nickel chrome steel ( SNC), nickel chrome molybdenum steel (S
NCM), chrome steel (SCr), chrome molybdenum steel (SCM), manganese steel (SMn), manganese chrome steel (SMn C) and the like, the shaft base material 2A formed in a rod shape and the shaft base material The thin film 2B is generally composed of a magnetic thin film 2B formed of a magnetostrictive material such as an iron-aluminum alloy on the outer peripheral surface of 2A.
Both ends of the magnetostrictive shaft 2 project outside the casing 1 to form an output shaft. Also,
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, and the outer peripheral surface of the slit forming portion 2C is slanted downward at an angle of 45 ° to form slit grooves 4, 4, 4. … Engraved, diagonally upward 45 °
The other slit grooves 5, 5, ... Are engraved at an angle of.

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. In 7, a magnetic path is formed by the surface magnetic field.

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. Each of the coils 9 and 10 described later is disposed 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. 5, 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, and a magnetic thin film 2B is integrally formed on the shaft base material 2A to form a shaft material. 16 is formed.

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 the heating step of Process IV, the entire shaft material 16 in which the slit grooves 4 and 5 are formed is heated in air or nitrogen gas, for example, to 800 to 900 ° C., preferably 850 ° C. before and after. This temperature is maintained for one hour before and after.

Next, in the oil cooling step of process V, the entire shaft material 16 heated in the heating step is immersed in the oil liquid 17 in air or nitrogen gas as shown in FIG. In this manner, the magnetic annealing of the shaft material 16 is performed by the heating step and the oil cooling step, processing distortion is removed, hysteresis is reduced, and variations in output sensitivity and hysteresis of individual shaft materials 16 are reduced. After that, the magnetostrictive shaft 2 is completed.

Now, 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. 5 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.

In this state, the magnetostrictive shaft 2 is 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,

[0020]

[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. 8 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 18 shown in FIG. 8, and the torque detection sensitivity at this time has an inclination θ, and when the torque is increased or decreased. Is represented by a hysteresis width h.

[0022]

By the way, in the above-described method of manufacturing a magnetostrictive shaft according to the prior art, since the shaft member 16 is heated in the gas in air or nitrogen in the heating step and the oil cooling step, the shaft is cooled. The magnetic thin film 2B on the surface of the material 16 is oxidized or nitrided, which increases the hysteresis and reduces the torque detection sensitivity. For example, as the magnetic thin film 2B, iron containing 13% of aluminum-
When an aluminum alloy is used, as shown in Table 1 below, the surface of the magnetic thin film 2B is oxidized in the heating process and the oil cooling process, the torque detection sensitivity is reduced to 0.232 V, and the hysteresis is 3. There is a problem that it increases to 2%.

On the other hand, if the heating step and the oil cooling step are carried out in vacuum, it is possible to prevent the surface of the shaft material 16 from being oxidized or nitrided, but in this case, the magnetic thin film 2B is used.
However, there is a problem in that the torque detection sensitivity cannot always be improved because the cooling rate is slowed.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a method for manufacturing a magnetostrictive shaft which can reduce hysteresis and improve torque detection sensitivity.

[0025]

In order to solve the above-mentioned problems, a method of manufacturing a magnetostrictive shaft adopted by the present invention comprises a machining step of machining a shaft material having a magnetostrictive material at least on the surface side, and a machining step. It comprises a heating step of heating the applied shaft material in a rare gas to maintain it in a high temperature state, and an oil cooling step of immersing the heated shaft material in an oil liquid in the rare gas.

[0026]

With the above structure, since the shaft material is heated in the rare gas in the heating step, it is possible to prevent the surface of the shaft material from being oxidized or nitrided. Further, in the oil cooling step, the shaft material can be cooled at a high speed by immersing the shaft material in an oil liquid in a rare gas.

[0027]

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.

FIG. 1 shows a method of manufacturing a magnetostrictive shaft according to this embodiment, and the manufacturing method comprises processes 1 to 5.

First, process 1 to process 3 indicate processing steps, which are the process I described in the prior art.
~ In almost the same manner as in Process III, in Process 1, the shaft base material 2A made of structural steel is heated to, for example, 750 to 900 ° C.
Quench by heating to a moderate temperature.

Next, in process 2, 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, and the magnetic thin film 2B is integrally formed on the shaft base material 2A to form the shaft material. 21 is formed.

Then, in the process 3, the shaft base material 2
The magnetic thin film 2B that covers the outer circumference of A over the entire circumference is subjected to surface processing, and the slit grooves 4 and 5 are machined in order to form the magnetic anisotropic portions 6 and 7 on the surface side of the magnetic thin film 2B. To do.

Next, in the heating step of Process 4, 0.067 to 0.080 M is stored in the airtight chamber 22 as shown in FIG.
With the Ar (Ar) gas (or helium gas, neon gas, etc.) as a rare gas of about Pa (500 to 600 Torr) being filled, the shaft member 21 is heated by an electric furnace (not shown) or the like. For example 800-90
It is carried out by heating to 0 ° C., preferably 850 ° C. before and after, and maintaining this temperature state for about 1 hour.

Next, in the oil cooling step of the process 5, the entire shaft material 21 heated in the heating step is immersed in the oil liquid 17 in the airtight chamber 22 filled with, for example, argon gas to thereby obtain the shaft material. 21 is oil-cooled and magnetic annealing is performed.

Thus, according to the present embodiment, in the heating step, the airtight chamber 22 of the shaft member 21 is filled with argon gas of about 1 atm, and the temperature before and after 850 ° C.
Magnetic annealing is performed by heating for about one hour, and in the oil cooling step, the entire shaft material 21 heated in the heating step is immersed in the oil liquid 17 in the airtight chamber 22 filled with argon gas and oil-cooled. Since this is performed, the following operational effects are achieved.

That is, in the heating step, since the periphery of the shaft material 21 is filled with argon gas, the shaft material 21
When the shaft material 21 is heated to a high temperature,
It is possible to prevent the magnetic thin film 2B on the surface of the substrate from being oxidized or nitrided, and thus it is possible to prevent the hysteresis from increasing.

Further, by immersing the shaft material 21 in the oil liquid 17 in argon gas, the cooling speed of the shaft material 21 can be increased, and thus the magnetostrictive shaft 2 can have a large torque detection sensitivity. .

Here, the content of aluminum in the iron-aluminum alloy forming the magnetic thin film 2B is 10%, 1
Table 1 shows the numerical values of sensitivity and hysteresis when changed to 3% and 15%. Also, as reference values, the numerical values are shown when the heating step and the oil cooling step are performed in vacuum or in air.

[0038]

[Table 1]

Thus, according to the manufacturing method of this embodiment,
As shown in Table 1, it is possible to provide a magnetostrictive shaft with a smaller hysteresis and a higher torque detection sensitivity as compared with the conventional manufacturing method.

In the above embodiment, the shaft base material 2A is used.
Although the magnetic thin film 21B is formed by thermally spraying a magnetostrictive material such as an iron-aluminum alloy on the above, the present invention is not limited to this, and for example, a magnetostrictive material sprayed on the shaft base material 21A such as Permalloy. Alloys may be used.

In the above embodiment, the shaft base material 2A is used.
The case where the magnetic thin film 2B made of a magnetostrictive material is formed on the surface of the to form the shaft material 21 and the magnetostrictive shaft 2 is manufactured from the shaft material 21 has been described as an example, but the present invention is not limited to this. Alternatively, for example, the shaft material may be entirely made of a magnetostrictive material.

[0042]

As described above in detail, in the method for manufacturing a magnetostrictive shaft according to the present invention, a machining step of machining a shaft material having a magnetostrictive material at least on the surface side and a machining of the shaft material with a rare gas. It has a heating process in which it is heated in the air and kept at a high temperature, and an oil cooling process in which the heated shaft material is immersed in an oil liquid in a rare gas. However, since the circumference of the shaft material is filled with the rare gas, it is possible to prevent the surface of the shaft material from being oxidized or nitrided, and thereby to reduce the hysteresis. Further, by immersing the shaft material in the oil liquid in the rare gas, the cooling rate of the shaft material can be increased, and thereby the torque detection sensitivity can be increased.

[Brief description of drawings]

FIG. 1 is a process explanatory view showing a manufacturing process of a magnetostrictive shaft according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a heating process and an oil cooling process.

FIG. 3 is a vertical sectional view showing 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.

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

FIG. 6 is a process explanatory view showing a manufacturing process of a magnetostrictive shaft according to a conventional technique.

FIG. 7 is an explanatory diagram of a heating process and an oil cooling process.

FIG. 8 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]

 2 Magnetostrictive shaft 2A Shaft base material 2B Magnetic thin film 17 Oil liquid 21 Shaft material 22 Airtight chamber

Claims (2)

[Claims] 1. A machining step of machining a shaft material, at least the surface side of which is made of a magnetostrictive material, and a heating step of heating the machined shaft material in a rare gas to keep it at a high temperature. A method of manufacturing a magnetostrictive shaft, which comprises an oil cooling step of immersing the shaft material in an oil liquid in a rare gas. 2. The shaft material is heated to 80 in the heating step.
The method for producing a magnetostrictive shaft according to claim 1, wherein the magnetostrictive shaft is placed in a rare gas at a temperature of 0 to 900 ° C. for 1 hour before and after.