JPH09243476A - Magnetostrictive torque sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetostrictive torque sensor which suppresses an undesirable effect based on a fact that one pair of right and left magnetostrictive materials are discontinuous, and by which a torque acting on a shaft can be detected with good accuracy. SOLUTION: A torque sensor is composed of one pair of right and left magnetostrictive materials 2 which are installed on the circumferential face of a shaft 1 so as to be tilted upward and downward with reference to the axial line of the shaft 1 and of one pair of exciting and detecting coils 7, 8 which are installed so as to correspond to the respective magnetostrictive materials 2, 3. In this case, a connection magnetostrictive part 4 which is connected to respective end parts of the right and left magnetostrictive materials 2, 3 so as to make the magnetostrictive materials continuous is installed between the right and left magnetostrictive materials. The connection magnetostrictive part 4 is installed so as to be exposed intermittently while it makes one round of the shaft 1.

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, and in particular, it uses a pair of left and right magnetostrictive members which are provided on a peripheral surface of a shaft inclining upward and downward with respect to the axis of the shaft. The present invention relates to a magnetostrictive torque sensor capable of detecting torque acting on a shaft.

[0002]

2. Description of the Related Art In recent years, it has been common practice to measure the torque acting on the shaft of a machine body and analyze the operating state of the shaft. And, the magnetostrictive torque sensor for detecting this torque uses the inverse magnetostrictive effect of the magnetostrictive material whose permeability changes when stress is applied and the shape changes, and is non-contact with the shaft. Since it can detect torque, it is used in the FA field and the like, and its performance is desired to be improved.

FIG. 7 shows an example of such a magnetostrictive torque sensor. When torque is applied to the shaft 101 which is driven to rotate about the axis 0 by the driving force of the machine body, the circumference of the shaft 101 is shown. The pair of left and right magnetostrictive members 102 and 103 provided on the surface are deformed by the torque, and by detecting the deformations by the excitation / detection coils 108 and 109, respectively, the torque can be detected without contacting the shaft 101. It is a thing.

The specific structure is as follows. As shown in FIG. 7, the shaft 101 of the machine body (not shown)
Is rotated by receiving the driving force from the machine body, and the magnetostrictive material 102 has an angle of 45 ° obliquely downward from the axis 0 direction and an angle of 45 ° obliquely upward from the axis 0 direction on its peripheral surface. The magnetostrictive material 103 is provided. As a result, a pair of left and right magnetostrictive members having a C-shape (chevron structure) are formed, and shape magnetic anisotropy is imparted. As the magnetostrictive materials 102 and 103, a method of sticking an amorphous magnetostrictive material to the shaft 101 with an organic adhesive, a method of using a shaft having a magnetostrictive effect, a method of welding magnetostrictive metal powder to the shaft 101 at high temperature, etc. Provided by.

The fixed portion 104 is the shaft 10
1 is fixed to the machine body in a state of enclosing it, and bearings 105 for the shaft 101 are provided at both ends thereof.
106 is attached. Therefore, the shaft 101
Rotate relative to the fixed portion 104. Also,
A holding member 107 is attached to the inner peripheral surface of the fixed portion 104, and excitation / detection coils 108, 10 are provided in two annular groove portions formed in the holding member 107.
9 are installed. This excitation / detection coil 108, 1
No. 09 is installed so as to surround the magnetostrictive materials 102 and 103, respectively.

When a torque as shown by an arrow in the figure acts on the shaft 101, a tensile stress acts on the magnetostrictive material 102 and a compressive stress acts on the magnetostrictive material 103.
Each magnetostrictive material is deformed by each stress. Since the respective magnetic permeability changes according to the deformation of the magnetostrictive material, the excitation / detection coil 108,
The torque acting on the shaft 101 can be detected by changing the output from each of 109 and using the difference between the outputs from the excitation / detection coils 108 and 109 by a differential amplifier (not shown).

[0007]

The conventional magnetostrictive torque sensor described above, however, has the following problems. Here, a pair of left and right magnetostrictive members 1 having a chevron structure.
Since 02 and 103 are discontinuous between them, the impedance distribution of each is a parabola with an upward convex shape as shown in FIG. 8. Comparing these, the two distributions are asymmetric and at the same time one distribution Is also asymmetric. This is considered to occur due to the temperature difference between the magnetostrictive materials 102 and 103 when the magnetostrictive materials 102 and 103 are provided.

Therefore, when a force in the thrust direction acts on the shaft 101 provided with such two discontinuous magnetostrictive materials 102 and 103, the magnetostrictive materials 102 and 103 are formed.
Since the relative positions of the excitation and detection coils 108 and 109 are displaced, the amounts of change in impedance of the excitation and detection coils 108 and 109 differ. This causes a change in the differential voltage based on the outputs from both sides to cause a zero-point variation, which causes a problem that the torque acting on the shaft 101 cannot be accurately detected. In particular, when a rotary cutting tool such as an end mill or a drill is attached to the shaft 101, a force in the thrust direction acts on the shaft 101 during cutting, so the torque acting on the shaft 101 is accurately detected during this cutting. It will not be possible.

In the excitation / detection coils 108 and 109, since the two impedance distributions are asymmetrical, the temperature coefficients of these impedances are different from each other. Therefore, when the ambient temperature changes and the shaft 101 expands and contracts, the amounts of change in the impedances differ from each other, so that the differential voltage based on the outputs from both changes and the zero point fluctuation occurs. 10
There is also a problem that the torque acting on No. 1 cannot be detected accurately.

The present invention has been made in view of such a problem, and suppresses the above-mentioned adverse effects due to the discontinuity of a pair of left and right magnetostrictive materials, and accurately controls the torque acting on the shaft. An object of the present invention is to provide a magnetostrictive torque sensor capable of detecting.

[0011]

In order to solve the above problems and to achieve the above object, a magnetostrictive torque sensor according to a first aspect of the present invention has a circumferential surface of a shaft which faces upward with respect to the axis of the shaft. A pair of left and right magnetostrictive members that are inclined downwards, and a pair of excitation / detection coils that are installed in correspondence with the respective magnetostrictive members. And a connection magnetostrictive portion for connecting the two to make them continuous, and the connection magnetostrictive portion is provided so as to appear intermittently during one round of the shaft.

Further, in the magnetostrictive torque sensor according to a second aspect of the invention, the connection magnetostrictive portion is individually provided so as to connect the left and right magnetostrictive materials in a one-to-one relationship. Furthermore, in the magnetostrictive torque sensor according to claim 3,
It is characterized in that the connection magnetostrictive portion is provided in a curved strip shape so as to face the respective left and right magnetostrictive materials.

As described above, in the magnetostrictive torque sensor according to the first aspect of the invention, the pair of left and right magnetostrictive members are connected by the connecting magnetostrictive portion, and the connecting magnetostrictive portion allows the two to be continuous. The change in impedance in the axial direction becomes extremely small, and the symmetry of the impedance distribution between the two becomes high. Therefore, even if the relative position between the magnetostrictive material and the excitation / detection coil shifts due to the force in the thrust direction acting on the shaft, the excitation / detection coils have almost the same impedance value before and after the shift. There is no change in the difference voltage between the two (the difference voltage remains 0), and the zero point fluctuation is suppressed to a small extent.

Further, since the impedance distribution has a high symmetry as described above, when the ambient temperature changes and the shaft expands or contracts, the impedance changes before and after the temperature change become substantially the same. There is no change in the difference voltage between the two (the difference voltage remains 0), and the zero point fluctuation is suppressed to a minimum. The connecting magnetostrictive portion is provided so as to appear intermittently during one round of the shaft, and the connecting magnetostrictive portion is not provided continuously over the entire circumference of the shaft. Therefore, the influence of the connecting magnetostrictive portion on the excitation / detection coil is reduced.

In the magnetostrictive torque sensor according to the second aspect of the invention, since the connecting magnetostrictive portions are individually provided so as to connect the left and right magnetostrictive materials in a one-to-one relationship, the continuity of the pair of left and right magnetostrictive materials is maintained. While maintaining, the connecting magnetostrictive portion does not have a great influence on the excitation / detection coil. In this case, it is not necessary to connect all of the left and right magnetostrictive materials with the connecting magnetostrictive portion, and an arbitrary number of them may be connected with the connecting magnetostrictive portion.

Further, in the magnetostrictive torque sensor according to the third aspect of the invention, since the connecting magnetostrictive portion is provided in a curved strip shape so as to face the respective directions of the left and right magnetostrictive materials, the connecting magnetostrictive portion is connected to the exciting / detecting coil. It is possible to further reduce the influence of the. This is because when the connection magnetostrictive portion has a corner portion, a large amount of magnetostrictive material exists in this corner portion, and the magnetostrictive material in this corner portion affects the excitation / detection coil.

[0017]

FIG. 1 is a block diagram showing an embodiment of the present invention.
~ It demonstrates with reference to FIG. As shown in FIG. 1, a shaft 1 is rotationally driven by receiving a driving force from a machine body (not shown) such as a machining center, and a pair of left and right magnetostrictive members 2 and 3 and these magnetostrictive members are provided on a peripheral surface thereof. A connection magnetostrictive portion 4 for connecting the materials 2 and 3 is provided. The magnetostrictive material 2 is
The magnetostrictive materials 3 are arranged in parallel over the circumference of the shaft 1 at an angle of 45 ° obliquely downward from the axis 0.
The shafts 1 are arranged in parallel at an angle of 45 ° upward from the axis 0 over the entire circumference of the shaft 1. Thereby, the magnetostrictive materials 2, 3
Form a pair of “C” -shaped (chevron structure). The connecting magnetostrictive portion 4 is provided so as to be connected to the end portions of the magnetostrictive materials 2 and 3 so that the magnetostrictive materials 2 and 3 are continuous.

The magnetostrictive materials 2 and 3 and the connecting magnetostrictive portion 4 are
First, a chevron shape is formed on the shaft 1 by a rolling method, then magnetostrictive powder is attached to the chevron shape portion by plasma spraying, and then the magnetostrictive powder is welded to the chevron shape portion in a vacuum electric furnace. Therefore, the same magnetostrictive material (for example, Fe-Ni-Mo-B) is used for the magnetostrictive materials 2 and 3 and the connection magnetostrictive portion 4, and they are simultaneously provided as one body. However,
Instead of such a method of welding the magnetostrictive powder, another method such as a method of sticking a chevron-shaped amorphous magnetostrictive material to the shaft 1 with an organic adhesive may be used.

The cross section of the shaft 1 provided with the connection magnetostrictive portion 4 is as shown in FIG. That is,
The connection magnetostrictive portion 4 is not provided over one round of the shaft 1, but intermittently makes one round of the shaft 1. However, the connecting magnetostrictive portion 4 for one round of the shaft 1
The ratio is not limited to that shown in FIG. 1 and can be increased or decreased as appropriate. In addition, the connection magnetostrictive portions 4 are not limited to appear at regular intervals during one round of the shaft 1, and the intervals may be uneven. Furthermore, each connection magnetostrictive portion 4
Instead of connecting the left and right magnetostrictive materials 2 and 3 in a one-to-one relationship, for example, two or three magnetostrictive materials 2 and 3 may be connected together.

It should be noted that, as described above, 1 mm is provided on the shaft 1 having the magnetostrictive members 2 and 3 continuous by the connecting magnetostrictive portion 4.
By moving the measurement coil for each and measuring the impedance with the LCR meter, the impedance distribution as shown in FIG. 3 was obtained. In this impedance distribution, it is confirmed that there are many flat portions in the portions corresponding to the magnetostrictive materials 2 and 3, and the amount of change in impedance is small in the axis 0 direction of the shaft 1. In addition,
It is considered that the central convex portion in the impedance distribution is due to the connection magnetostrictive portion 4, and the value of impedance is caused by the fact that the magnetostrictive material per unit length in the direction of the axis 0 is larger than the magnetostrictive materials 2 and 3. Is larger than the magnetostrictive materials 2 and 3.

Next, the fixed portion 5 is formed into a cylindrical shape that allows the shaft 1 to penetrate therethrough, and is fixed to the machine body by the support portion 6. Therefore, the shaft 1 is rotationally driven relative to the fixed portion 5. Also,
Excitation / detection coils 7 and 8 are provided on the inner peripheral surface of the fixed portion 5 in a positional relationship corresponding to the magnetostrictive materials 2 and 3, respectively. The excitation / detection coils 7 and 8 are provided in annular groove portions provided in the holding member 9, respectively, and are attached to the fixed portion 5 by attaching the holding member 9 to the inner peripheral surface of the fixed portion 5. Further, bearings 10 for rotatably supporting the shaft 1 are provided at both ends of the fixed portion 5,
11 is attached so that the central axes of the excitation / detection coils 7 and 8 are aligned with the axis 0 of the shaft 1.

The outputs from the excitation / detection coils 7 and 8 are input to the differential amplifier 12 and then taken out to the machine body by the connection cable C. This differential amplifier 1
2 does not output from the excitation / detection coils 7 and 8 when the input values are the same, but the excitation / detection coils 7 and 8
When the input values from 8 are different, the difference between these input values is amplified and output.

In the magnetostrictive torque sensor constructed by incorporating the shaft 1 as described above, the zero point is set so that the output from the differential amplifier 12 becomes 0 in the state where the torque is not acting on the shaft 1. It Then, in this magnetostrictive torque sensor, when the zero point variation was measured when the shaft 1 was moved by 200 μm in the thrust direction, an experimental result was obtained in which the zero point variation at that time was suppressed to 1.5% FS. As for the temperature characteristics, experimental results were obtained in which the temperature was suppressed to ± 1% FS per 10 ° C. This is because the shaft 1 has a flat impedance distribution as shown in FIG. 3, and even when the relative positions of the magnetostrictive materials 2 and 3 and the excitation / detection coils 7 and 8 are deviated, the amount of impedance change is large. Is not significantly changed, and the difference between the outputs from the excitation / detection coils 7 and 8 is not significantly changed.

Next, the operating state of the magnetostrictive torque sensor configured as described above will be described. First, when the shaft 1 is rotated around the axis 0, the shaft 1 is rotationally driven relative to the fixed portion 5 while being supported by the bearings 10 and 11. A rotary cutting tool such as a drill or an end mill is attached to the shaft 1, and cutting can be performed by rotating the rotary cutting tool around the axis 0.

When a torque acts on the rotary cutting tool during the cutting process and a torque in the direction shown by the arrow in FIG. 1 acts on the shaft 1, the torque is applied to the shaft 1.
Is transmitted to the magnetostrictive material 2 (left side in FIG. 1), tensile stress acts on the magnetostrictive material 2 and strain occurs in the form of stretching it, while compressive stress acts on the magnetostrictive material 3 (right side in FIG. 1) to shrink it. Distortion occurs in the roof.

Therefore, by changing the magnetic permeability of each of the magnetostrictive materials 2 and 3 based on this strain, the output from each of the excitation / detection coils 7 and 8 changes according to the change of the magnetic permeability. This output is input to the differential amplifier 12, and the difference between the input values is amplified and output from the differential amplifier 12, and by analyzing this output, the torque acting on the shaft 1 can be detected. .

Since the differential amplifier 12 outputs the difference in output corresponding to the strain of the magnetostrictive materials 2 and 3, a force in the direction of the axis 0 (thrust direction), such as rotation in cutting, is applied to the shaft 1. The influence of the compressive force acting in the axial direction of the cutting tool can be excluded.
At this time, as described above, even if a force in the thrust direction acts on the shaft 1, the zero point variation is suppressed, so that the torque acting on the shaft 1 can be detected with high accuracy.

FIGS. 4 to 6 show another embodiment of the connection magnetostrictive portion 4. The connection magnetostrictive portion 4 shown in FIG. 4 connects all the corresponding magnetostrictive materials 2 and 3 to each other. The connection is not made with four, but is made with every other connection, and the one on which the magnetostrictive materials 2 and 3 are not continuous is left on the peripheral surface of the shaft 1. As a result, the impedance value in the connection magnetostrictive portion 4 can be reduced, and the central convex portion in the impedance distribution of FIG. 3 can be eliminated to further flatten the distribution. However,
Since the magnetostrictive materials 2 and 3 which are not continuous exist, some undulations appear in the impedance distribution corresponding to the magnetostrictive material 2 or 3.

The connection magnetostrictive portion 4a shown in FIG.
3 is connected by a curved strip.
By curving the connection magnetostrictive portion 4a in this manner, the amount of use of the magnetostrictive material can be reduced as compared with the connection magnetostrictive portion 4 having a corner portion, thereby lowering the impedance value in the connection magnetostrictive portion 4a. I am trying. Therefore, when compared with those shown in FIGS. 1 and 4, in the impedance distribution of FIG. 3, it is possible to reduce the central convex portion while maintaining the flattening of the magnetostrictive materials 2 and 3.

The connection magnetostrictive portion 4b shown in FIG. 6 is provided with the width of the curved strip-shaped portion of the connection magnetostrictive portion 4a shown in FIG. 5 narrowed. Thereby, the connection magnetostrictive portion 4b
In the impedance distribution of FIG. 3, it is possible to continuously flatten the magnetostrictive members 2 and 3 including the connecting magnetostrictive portion 4b.

The form of the connecting magnetostrictive portion is not limited to that shown in FIGS. 1 and 4 to 6, but the magnetostrictive members 2 and 3 are connected, and the connecting magnetostrictive portion intermittently makes one revolution around the shaft 1. The form is arbitrary if it is one. Further, as described above, the magnetostrictive material torque sensor of the present invention is not only applied to the detection of the torque acting on the shaft 1 to which the rotary cutting tool is attached, but also the torque acting on the shaft of various machine tools and the like. It is also applied to detect the.

[0032]

As described above, in the magnetostrictive torque sensor according to the first aspect, the pair of left and right magnetostrictive members are connected by the connecting magnetostrictive portion so that the left and right magnetostrictive members are connected to each other. It is possible to extremely reduce the change in impedance in the axis direction of and to increase the symmetry of the impedance distribution of both. Therefore, even if the relative position between the magnetostrictive material and the excitation / detection coil shifts due to the force in the thrust direction acting on the shaft, both the excitation / detection coils have almost the same impedance value before and after the shift, so both It is possible to prevent the difference voltage between them from changing (the difference voltage can be kept at 0), and thus the zero point fluctuation can be suppressed to a small extent, and the torque acting on the shaft can be detected with high accuracy.

Further, the impedance distribution has a high symmetry, and even when the shaft expands or contracts due to a change in ambient temperature, the impedance change amounts of the excitation and detection coils are substantially the same before and after the temperature change. Because,
It is possible to prevent the difference voltage between the two from changing (the difference voltage can be kept at 0), and by this effect, the zero point fluctuation can be suppressed to a small degree in combination with the above effect, and the torque acting on the shaft can be accurately measured. Can be detected. Since the connecting magnetostrictive portion is provided so as to appear intermittently during the complete rotation of the shaft, the influence of the connecting magnetostrictive portion on the excitation / detection coil can be reduced.

In the magnetostrictive torque sensor according to the second aspect of the present invention, since the connecting magnetostrictive portions are individually provided so as to connect the left and right magnetostrictive materials in a one-to-one relationship, the continuity of the pair of left and right magnetostrictive materials is maintained. While maintaining, it is possible to reduce the influence exerted on the excitation / detection coil by the connection magnetostrictive portion. Therefore, it is possible to reduce the convex portion due to the connection magnetostrictive portion in the impedance distribution, and to suppress the zero point variation to a minimum,
The torque detection accuracy can be improved.

Further, in the magnetostrictive torque sensor according to the third aspect, since the connecting magnetostrictive portion is provided in a curved strip shape so as to face each of the left and right magnetostrictive materials, the connecting magnetostrictive portion is connected to the exciting / detecting coil. It is possible to further reduce the influence of. Therefore, it is possible to further reduce the convex portion due to the connecting magnetostrictive portion in the impedance distribution, further suppress the zero point variation to a minimum, and further improve the torque detection accuracy.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a magnetostrictive torque sensor according to the present invention.

2 is a cross-sectional view of the shaft taken along the line A of FIG.

FIG. 3 is a graph showing an impedance distribution in a shaft.

FIG. 4 is a front view showing another embodiment of the connection magnetostrictive portion.

FIG. 5 is a front view showing another embodiment of the connection magnetostrictive portion.

FIG. 6 is a front view showing another embodiment of the connection magnetostrictive portion.

FIG. 7 is a sectional view showing one form of a conventional magnetostrictive torque sensor.

FIG. 8 is a graph showing a conventional impedance distribution in a shaft.

[Explanation of symbols]

 1 Shaft 2, 3 Magnetostrictive Material 4, 4a, 4b Connection Magnetostrictive Section 5 Fixed Section 7, 8 Excitation / Detection Coil 10, 11 Bearing 12 Differential Amplifier

Claims (3)

[Claims] 1. A pair of left and right magnetostrictive members provided on the circumferential surface of the shaft inclining upward and downward with respect to the axis of the shaft, and a pair of exciting / exciting members installed corresponding to the respective magnetostrictive members. In the magnetostrictive torque sensor including a detection coil, a connecting magnetostrictive portion is provided between the left and right magnetostrictive members to connect the respective end portions to make the both continuous, and the connecting magnetostrictive portion is the shaft. A magnetostrictive torque sensor, wherein the magnetostrictive torque sensor is provided so as to appear intermittently during one round of the. 2. The magnetostrictive torque sensor according to claim 1, wherein the connection magnetostrictive portion is individually provided so as to connect the left and right magnetostrictive materials in a one-to-one relationship. 3. The magnetostrictive torque sensor according to claim 1 or 2, wherein the connection magnetostrictive portion is provided in a curved strip shape so as to face each of the left and right magnetostrictive members.