JP2022121929A - Magnetostrictive sensor and method for manufacturing the same - Google Patents

Abstract

To provide a magnetostrictive sensor that has high sensor sensitivity and can be easily manufactured, and in addition, to provide a magnetostrictive sensor with less hysteresis.SOLUTION: A magnetostrictive sensor has a magnetostrictive part 110 that is formed on a member by thermal spraying and subjected to heat treatment, and the magnetostrictive sensor has an increased sensor sensitivity through the heat treatment.SELECTED DRAWING: Figure 7

Description

The present invention relates to a magnetostrictive sensor that detects torque.

Conventionally, a sensor is used to detect the torque acting on the shaft. In the invention described in Patent Document 1, an amorphous magnetic ribbon is wound around a shaft and fixed, and torque is measured by detecting a change in the magnetic properties of the amorphous magnetic ribbon to detect the strain stress of the rotating shaft that accompanies torque fluctuations. is doing. From the viewpoint of low cost and productivity, instead of the above method, a sensor having a magnetostrictive film formed by spraying a thermal spray material onto the surface of the measurement member is also used. It is desirable that the torque sensor have characteristics of high sensitivity and little hysteresis. Amorphous magnetostrictive films have the characteristic of magnetic isotropy, which is convenient for reducing hysteresis, and the properties of high magnetic permeability and low Young's modulus are also favorable in terms of sensitivity. Equipped sensors are also used.

JP-A-60-123078

Sensors are desired to have high sensor sensitivity in order to detect minute inputs with high accuracy. In addition, although the amorphous magnetostrictive film has the above theoretical advantages, it has the disadvantage that the sensitivity is lowered and the hysteresis is increased due to the residual stress generated in the material molecules constituting the magnetostrictive film. there were. If the sensitivity is low or the hysteresis is large, the measurement accuracy will drop, so a sensor with little hysteresis is desired. In addition, the sensor should be easily manufacturable.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a magnetostrictive sensor that has high sensor sensitivity and can be easily manufactured. It is intended to

A magnetostrictive sensor according to the present invention has a heat-treated magnetostrictive film having a predetermined residual stress.

According to the present invention, the magnetostrictive film of the magnetostrictive sensor has increased sensor sensitivity. Therefore, it is possible to detect an output such as torque with high accuracy with respect to a minute input.

FIG. 4 is a perspective view showing one magnetic core block in the stator structure of the torque sensor according to the embodiment of the invention; FIG. 2 is a schematic diagram showing a magnetostrictive portion showing a state in which winding portions are mounted in grooves of the magnetic core block of FIG. 1; FIG. 4 is an explanatory diagram of an output signal when the torque sensor is in operation; FIG. 2 is a schematic diagram in which a plurality of magnetic core blocks in FIG. 1 are combined, and tooth end surfaces that form oblique magnetic fluxes are arranged vertically and horizontally symmetrically. FIG. 2 is a schematic diagram showing a configuration of a magnetic path-integrated core obtained by combining a plurality of magnetic core blocks shown in FIG. 1; FIG. 5 is an enlarged view of a part of the schematic diagram of FIG. 4; FIG. 4 is a characteristic diagram showing the sensitivity of the magnetostrictive torque sensor according to the embodiment of the invention; FIG. 4 is a characteristic diagram showing hysteresis of the magnetostrictive torque sensor according to the embodiment of the invention;

A magnetostrictive sensor according to an embodiment of the present invention is a magnetostrictive sensor having a magnetostrictive film formed on a member by thermal spraying and heat-treated. The magnetostrictive film is formed on the member by spraying a metallic glass material. By applying a heat treatment to the formed magnetostrictive film to adjust the residual stress to a desired value, the sensitivity can be increased compared to conventional sensors that have not been heat treated. Furthermore, by setting the heat treatment to a specific temperature range, the sensitivity can be increased and the hysteresis can be reduced.

A magnetostrictive sensor according to an embodiment of the present invention will be described below. The gist of the present invention is that it has a magnetostrictive film formed on a member and subjected to heat treatment, and the sensor using the magnetostrictive film of the invention can be implemented in any desired form. An embodiment of a magnetostrictive sensor for detecting torque of a rotating shaft will be described below. A torque sensor equipped with a magnetostrictive sensor according to the present invention is configured to detect distortion by a stator structure surrounding the rotating shaft by utilizing the Villari effect of the magnetostrictive portion provided on the rotating shaft. In the stator structure, inclined sides are attached to the tooth end surfaces facing the rotating shaft, and the sides are arranged so as to face each other. is efficiently detected as a change in magnetic flux. FIG. 6 shows its schematic structure. A magnetostrictive film is formed on the outer peripheral surface of the rotating shaft 90 facing the inner peripheral surface of the stator structure 10, and a magnetostrictive portion 110 is provided. The stator structure 10 is described below.

FIG. 1 shows one magnetic core block among many magnetic core blocks 10a in the stator structure of a torque sensor according to an embodiment of the magnetostrictive sensor of the present invention.
The magnetic core block 10a is integrally formed of a magnetic material by, for example, a metal injection molding machine. More specifically, the first tooth end face 260a, the second tooth end face 260b, and the third tooth end face 260c are formed integrally with the back yoke 100 serving as a substrate.

A first groove 101 and a second groove 102 are formed between the tooth end surfaces 260a, 260b, and 260c, and shafts 90 shown in FIG. A first side 30a, a second side 30b and a third side 30c, which are curved surfaces facing the curved surface of the peripheral surface 91 of the shaft 90, are arranged with a slight gap from the surface of the shaft 90. As shown in FIG.

A pair of first and second winding parts 105 and 106 are arranged in each of the grooves 101 and 102 so as to form a V shape when viewed from the surface side P, and a first magnetic flux direction 107 and a second magnetic flux are provided. A direction 108 is configured to occur.
2 shows that the winding portions 105 and 106 are provided with the respective grooves 101 and 102. For example, as another form, although not shown, the teeth 260a, A configuration that wraps around 260b, 260c and passes through each groove 101, 102 is also possible.
Therefore, one magnetostrictive portion 110 is formed by the configuration of FIG.

FIG. 3 shows the number of magnetic core blocks 10a shown in FIG. 4, that is, the stator structure in which the magnetostrictive portions 110 are arranged in a cylindrical shape (FIGS. 5 and 6), and the shaft 90 is rotated. A first signal VL1 obtained from one flux direction 107 and a second signal VR1 obtained from a second flux direction 108 (ie, symmetrical with the first flux direction 107) are obtained, and the difference 111 is obtained.
In the conventional state, the excitation coils 214a of the winding portions 105 and 106 are excited, and the torsion of the shaft 90 is detected by the detection coils 215a. The change in the magnetic permeability of the shaft 90 is used to take out the output voltage difference in a large number of magnetostrictive portions 110 . This embodiment utilizes the well-known Villari Effect using the magnetostrictive portion 110 described above, that is, the change in magnetic permeability in a ferromagnetic material in a magnetic field under the action of stress. .

FIG. 4 is a configuration diagram of a pair of magnetic core blocks 10a arranged vertically and horizontally symmetrically by combining teeth end surfaces 260a, 260b, and 260c that form oblique magnetic fluxes. The operation of FIG. 1, which is the basis of FIG. 4, will be described below.
In the magnetostrictive sensor 150 utilizing the Villari effect of the magnetostrictive portion 110 imparted to the shaft 90, inclined sides 30a, 30b and 30c are attached to the tooth end faces 260a, 260b and 260c facing the shaft 90, and the finished product is: By arranging the sides so that they face each other, the main magnetic flux can flow in an oblique direction (more than 0° and less than 90°) with respect to the axial direction E of the shaft 90. can be efficiently detected as a change in The efficiency is maximized when the gradient of the magnetic flux is 45°. In addition, by integrating the teeth, the winding portions 105 and 106 that connect them, and the back yoke 100, and constructing them from a continuous magnetic material, an efficient core with little magnetic loss can be manufactured as a pair. Minimize manufacturing errors. Furthermore, in the same core, by using a plurality of teeth to form a magnetic flux in an oblique direction (larger than 0° and smaller than 90°) with respect to the axial direction vertically or horizontally symmetrically, a plurality of teeth symmetrical with respect to the strain direction signals VL1 and VR1 can be obtained, and the detection accuracy can be improved by taking the difference 111 between them as shown in FIG.

The configuration of FIG. 5 shows a configuration in which four magnetic core blocks 10a are combined, and in reality, five magnetic core blocks 10a are further provided to form a finished product. state.
An example of a configuration for carrying out the present invention is described in FIGS. 4 to 6. FIG. The minimum unit of the magnetic core blocks of the embodiment is an arbitrary number N, and the magnetic core blocks are arranged in the axial direction.
In this embodiment, the inclined sides 30a, 30b, and 30c of the tooth end faces 260a, 260b, and 260c facing the shaft 90 face each other, and the main magnetic flux obliquely inclined with respect to the axial direction E shown in FIG. The strain and its direction can be efficiently detected as changes in magnetic flux. In addition, by integrating the tooth end surfaces 260a, 260b, 260c, the winding portions 105, 106 connecting them, and the back yoke 100 and constructing them with a continuous magnetic material, an efficient magnetic core block with little magnetic loss can be obtained. and Furthermore, in the same magnetic core block, by combining a plurality of teeth end faces 260a, 260b, 260c that are symmetrical vertically, horizontally, or vertically and horizontally, magnetic flux oblique to the axial direction E is formed vertically, horizontally, or vertically and horizontally symmetrically. By doing so, it is possible to obtain a plurality of signals VL1 and VR1 symmetrical with respect to the distortion direction, and by taking the difference 111 between them, it is possible to improve the detection accuracy.

Therefore, by forming the main magnetic flux in a direction oblique to the axial direction E of the magnetostrictive portion 110, detection efficiency (sensitivity) can be improved. By forming the tooth end faces 260a, 260b, 260c, the winding portions 105, 106, and the back yoke 100 from an integrated continuous magnetic material, a magnetic core block with good magnetic efficiency can be produced, and manufacturing errors can be suppressed. .
In the same magnetic core block, by combining a plurality of tooth end faces 260a, 260b, and 260c, oblique magnetic flux with respect to the axial direction E of the magnetostrictive portion 110 is formed vertically or horizontally symmetrically. A plurality of signals VL1 and VR1 are acquired, and the difference 111 between them can be used to improve the detection accuracy.

<Method for manufacturing magnetostrictive film>
A method for manufacturing the magnetostrictive film of the magnetostrictive sensor of this embodiment will be described. The magnetostrictive film has two steps of forming the magnetostrictive film on the surface of the member and heat-treating the formed magnetostrictive film.

First, a method of forming a magnetostrictive film on the outer peripheral surface of shaft 90 will be described. A known thermal spraying method is used to form the magnetostrictive film. In the thermal spraying method, kinetic energy is applied to the material to be thermally sprayed from some energy source to cause particles of the thermal spraying material to fly at high speed, thereby directly forming a magnetostrictive film on the member to be measured. Specifically, the flame spraying method, in which the particles of the thermal spraying material are ejected by burning gas as a heat source, and the plasma spraying method, in which the particles of the thermal spraying material are ejected by a plasma jet, by applying a high voltage while flowing a plasma gas such as argon gas. , a cold spray method in which particles of the thermal spray material are blown away by supersonic flow of high-pressure gas through a tapered and diverging nozzle. Particles of the thermal spray material are ejected by any thermal spraying method, and while the shaft 90 is rotated, particles in a supercooled liquid phase are deposited on the outer peripheral surface of the shaft 90 to form a thermal spray coating.

Any material can be used as the material for forming the magnetostrictive film as long as it is a metallic glass material capable of forming a magnetostrictive film on the member to be measured. For example, metallic materials such as iron, nickel, ferrite, iron-cobalt based alloys, iron-nickel based alloys are used. In this embodiment, a material containing an iron-cobalt alloy as a main component is used as the thermal spray material. The thermal spraying material is used in a form suitable for the thermal spraying method, such as powder or wire.

In the magnetostrictive sensor of this embodiment, the residual stress is adjusted by heat treatment after thermal spraying to obtain a desired state. In the thermal spraying process, the thermal spray material is deposited on the member in an amorphous state. The film thickness is preferably about 100 μm.

Next, a method of heat-treating the formed magnetostrictive film will be described. A magnetostrictive film formed on a member by thermal spraying has a predetermined residual stress. If there is residual stress, it means that there is strain, and it is thought that if the residual stress is reduced, the sensor output, that is, the sensor sensitivity, can be increased. Heat treatment changes the sensor sensitivity and also changes the hysteresis. The magnetostrictive film is heat-treated to adjust the direction and magnitude of residual stress, thereby realizing desired sensor sensitivity and hysteresis.

As the heat treatment method, a known method can be selected, but high-frequency heating is preferred. High-frequency heating is a heating method that makes it easy to heat only a portion that is desired to be heated and to easily adjust the temperature. In this embodiment, the shaft 90 on which the magnetostrictive portion 110 is formed is subjected to heat treatment by high-frequency heating. The heat treatment is carried out in a temperature range equal to or higher than the Curie point temperature at which the magnetic state changes and equal to or lower than the phase transformation temperature at which crystallization proceeds. The thermal spray material formed of the iron-cobalt alloy used in this embodiment has a Curie point temperature of 500.degree. C. and a phase transformation temperature of 580.degree. The portion of the shaft 90 where the magnetostrictive film is formed is heated to a temperature in the range of 500° C. or more and 580° C. or less to adjust the residual stress. The heating time is selected in the range of about 5 to 30 seconds depending on the type of thermal spray material and sensor characteristic value. In this embodiment, the heating is performed for 10 seconds. The heat treatment temperature and heat treatment time are appropriately determined according to the thermal spray material, desired residual stress and sensor sensitivity.

<Experimental results according to the embodiment>
Tables 1 and 2 show the results of measuring the sensitivity and hysteresis of an example in which the formed magnetostrictive film was heat-treated and a comparative example for comparison. The thermal spraying material was mainly composed of iron-cobalt. The magnetostrictive film was formed on the outer peripheral surface of the shaft 90 by flame spraying so as to have a film thickness of 100 μm. Six samples of Examples 1 to 5 and Comparative Example 1 were measured. The magnetostrictive films of Examples 1 to 5 and Comparative Example 1 were all formed under the same conditions, and differed only in the heat treatment conditions after the formation of the magnetostrictive films.

The heat treatment temperature of each sample is 300° C. for Example 1, 450° C. for Example 2, 500° C. for Example 3, 550° C. for Example 4, and 650° C. for Example 5. In all the heat treatments of the examples, heating is stopped when the target temperature is reached. As a reference, a magnetostrictive film was produced in the same manner as in Examples 1 to 5, and Comparative Example 1, which was not heat-treated, was also measured.

A torque input of the same predetermined value was applied to each prepared sample, and the sensor output was measured. The measurement results of sensor output values, ie, sensor sensitivities, for the same predetermined torque input for each sample are as follows.

FIG. 7 shows the sensor sensitivity measurement results of Table 1. FIG. Regarding the sensor sensitivity, the sensor sensitivities of Examples 1, 2, 3, 4, and 5 are 0.0770.151 (V/Nm) and 0.368 (V/Nm), respectively. , 0.358 (V/Nm), and 0.190 (V/Nm). On the other hand, the sensor sensitivity of Comparative Example 1 without heat treatment was 0.052 (V/Nm). Therefore, sensor sensitivity increased for all heat treated samples. In particular, in Examples 3 and 4 in which the heat treatment was performed at a temperature higher than the Curie point temperature and lower than the phase transformation temperature, the sensor sensitivity was greatly improved compared to the case without heat treatment. Moreover, in the temperature range of 450° C. to 650° C., it can be said that the sensor sensitivity clearly increased compared to the case without heat treatment.

From the above, the sensor sensitivity was higher than that without heat treatment regardless of the temperature. In particular, when the heat treatment was performed at a temperature higher than the Curie point temperature and lower than the phase transformation temperature, the sensor sensitivity could be significantly improved. It is considered that high sensor sensitivity was obtained because the residual stress of the magnetostrictive film was removed by the heat treatment. Even if the sensor is made of a thermal spray material containing a material other than an iron-cobalt alloy as a main component, it is thought that the sensor sensitivity can be improved by heat-treating at a temperature above the Curie point and below the phase transformation temperature. When a material other than an iron-cobalt alloy is used as the thermal spray material, the Curie point temperature and the phase transformation temperature are values corresponding to the material of the thermal spray material.

Next, the hysteresis measurement results of each sample are as follows.

The hysteresis measurement results of Table 2 are shown in FIG. Regarding hysteresis, the hysteresis of Examples 1, 2, 3, 4, and 5 is 1.04 (F.S.%) and 3.51 (F.S.%), respectively. , 2.69 (F.S.%), 1.05 (F.S.%), and 1.25 (F.S.%). On the other hand, the hysteresis of Comparative Example 1 without heat treatment was 1.11 (F.S.%). In the temperature range including Example 2, Example 3, and Example 5, the hysteresis increased compared to Comparative Example 1 without heat treatment, but some including Example 1 and Example 4 The hysteresis decreased in the temperature range. In FIG. 4, assuming that a straight line parallel to the horizontal axis of Comparative Example 1 is A, the range below straight line A is the temperature range of the heat treatment in which a magnetostrictive film with reduced hysteresis compared to the case without heat treatment is obtained. is. That is, when heat treatment is performed at a temperature in the range of 550° C. or more and less than 580° C., it is considered that the hysteresis is reduced as compared with Comparative Example 1 without heat treatment.

As described above, the hysteresis is reduced in the case of heat treatment at 300° C. and in the range of 550° C. to less than 580° C. as compared with the case without heat treatment.

From the above results, the heat treatment changes the characteristic values of both the sensor sensitivity and the hysteresis. As is clear from FIGS. 7-8, the temperature range in which the sensor sensitivity increases is not the same as the temperature range in which the hysteresis decreases. Therefore, for the heat treatment temperature conditions of the sensor, the optimum heat treatment conditions are determined after determining the respective desired value ranges for the sensor sensitivity and hysteresis. When priority is given to the increase in sensor sensitivity, the temperature range in which the sensor sensitivity is sufficiently increased is 450° C. or higher and 650° C. or lower as compared to the case without heat treatment. In particular, a temperature range of the Curie point temperature or higher and the phase transformation temperature or lower is preferable. In order to increase the sensor sensitivity without increasing the hysteresis too much, the heat treatment temperature range is preferably 550° C. or higher. In particular, when the temperature is 550° C. or more and less than the phase transformation temperature (580° C.), the sensor sensitivity can be sufficiently increased and the hysteresis can be reduced as compared with the case without heat treatment.

The magnetostrictive sensor 150 in this embodiment has a heat-treated magnetostrictive film having a predetermined residual stress.

Therefore, the sensor sensitivity can be increased compared to the case of having a magnetostrictive film that has not been heat treated.

Also, the magnetostrictive sensor 150 in the present embodiment has a magnetostrictive film heat-treated at an optimum heat-treatment temperature.

Therefore, in addition to the increase in sensor sensitivity, hysteresis can be reduced compared to the case of having a magnetostrictive film that has not been heat-treated.

Further, the magnetostrictive sensor 150 according to the present embodiment adjusts the characteristics by heat treatment after thermal spraying, regardless of the thermal history during thermal spraying.

Therefore, temperature control during thermal spraying is easier than in the case where the shaft temperature is kept constant during thermal spraying and the characteristics are adjusted.

The manufacturing method of the magnetostrictive sensor 150 according to the present embodiment includes a step of heat-treating the magnetostrictive film to adjust the residual stress.

Therefore, sensor sensitivity can be increased.

The manufacturing method of the magnetostrictive sensor 150 according to the present embodiment includes a step of heat-treating the magnetostrictive film at an optimum heat-treating temperature to adjust the residual stress.

Therefore, hysteresis can be reduced in addition to sensor sensitivity.

150 Magnetostrictive sensor, 110 Magnetostrictive part.

Claims (5)

A magnetostrictive sensor having a heat-treated magnetostrictive portion (110) formed on a member by thermal spraying and having a predetermined residual stress,
A magnetostrictive sensor, wherein the magnetostrictive portion (110) is subjected to the heat treatment to increase the sensor output with respect to the input torque. The magnetostrictive sensor according to claim 1, wherein the magnetostrictive portion (110) has hysteresis reduced by the heat treatment. 3. The magnetostrictive sensor according to claim 1, wherein the thermal spraying is performed below the glass transition temperature. forming a magnetostrictive film on the member by thermal spraying;
A method for manufacturing a magnetostrictive sensor, comprising the step of heat-treating the magnetostrictive film to adjust the residual stress,
A method of manufacturing a magnetostrictive sensor, wherein the magnetostrictive portion (110) has an increased sensor output with respect to input torque due to the heat treatment. 5. The method of manufacturing a magnetostrictive sensor according to claim 4, wherein the magnetostrictive portion (110) has its hysteresis reduced by heat treatment.

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