JPH09196778A - Magnetostrictive torque sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to accurately detect the torque operating at a shaft by bringing the central axis of exciting and detecting coils into coincidence with the axis of the shaft, and suppressing the rotating zero-point change. SOLUTION: The magnetostrictive torque sensor has magnetostrictive materials 2, 3 provided at a shaft 1, and exciting and detecting coils 5, 6 installed corresponding to the materials 2, 3, and comprises bearing mounting parts 7, 8 integrally formed as bearings at a bobbin 4 provided with the coils 5, 6, wherein the central axes of the coils 5, 6 are brought into coincidence with the axis 0 of the shaft 1 by rotatably supporting the shaft 1 by the bearings 9, 10 mounted at the parts 7, 8.

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, for example, when a shaft is rotationally driven,
The present invention relates to a device capable of detecting torque acting on this 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. When a rotary cutting tool such as an end mill or a drill is attached to one end of the shaft, the torque that acts on the rotary cutting tool during cutting appears as the torque that acts on the shaft. Therefore, it is important to measure the torque, and analyze the cutting processing state from the result to optimize the processing, and thus it is important to measure the torque.

FIG. 3 shows an example of a magnetostrictive torque sensor for detecting the torque acting on the shaft according to the prior art. This is because when torque acts on the shaft 101 that is driven to rotate about the axis 0 by receiving the driving force of the machine body, the magnetostrictive members 102 and 103 formed on the shaft 101 are deformed by this torque, and such deformation is excited respectively. Also, the torque can be measured by detecting with the detection coils 108 and 109.

The specific structure is as follows. As shown in FIG. 3, 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 is provided on the peripheral surface thereof at an angle of 45 ° obliquely downward from the direction of the axis 0, and at the angle 45 ° obliquely upward from the axis 0. The magnetostrictive material 103 is provided at an angle. Then, the magnetostrictive material 10 of the shaft 101
The fixed portion 104 is provided so as to surround the portions 2, 103. The fixed portion 104 is fixed to the machine body, and bearings 105 and 106 for the shaft 101 are attached to both end portions thereof. Therefore, the shaft 101 rotates relative to the fixed portion 104.

A core member 107 is attached to the inner peripheral surface of the fixed portion 104, and the core member 1
The excitation and detection coils 108 and 109 are installed in two annular groove portions formed in 07. The excitation and detection coils 108 and 109 are installed on the core member 107 in a state of being wound around bobbins (not shown), and further installed in a positional relationship so as to correspond to the magnetostrictive materials 102 and 103, respectively. Has been done.

When a torque as shown by an arrow in the figure acts on the shaft 101, a tensile force acts on the magnetostrictive material 102 and a compressive force acts on the magnetostrictive material 103, so that the magnetic permeability of each magnetostrictive material changes. To do. The outputs from the excitation and detection coils 108 and 109 respectively change based on the degree of this change, and by analyzing the output results,
The torque acting on the shaft 101 can be detected.

[0007]

However, in the above-described conventional magnetostrictive torque sensor, the number of components for constituting the magnetostrictive torque sensor, in particular, the excitation and detection coils 108 and 109 are positioned with respect to the shaft 101. Due to the large number of parts, when combining the tolerances of these parts,
There is a case where the central axes of the excitation / detection coils 108 and 109 and the axis line 0 of the shaft 101 are deviated from each other, which causes a rotation zero point variation and deteriorates sensor accuracy.

That is, when the number of parts is large, the core member 107 is left with the center axes of the bobbins forming the two exciting and detecting coils 108 and 109 displaced during the assembly of the sensor.
The shaft 101 may be tilted with respect to the excitation / detection coil 108 and the like due to the mounting of the bearing 105 and the like.
Is eccentric with respect to the excitation / detection coil 108, the torque acting on the shaft 101 cannot be accurately detected, and the excitation / detection coil 108 is rotated by the rotation of the shaft 101 even when no torque is applied to the shaft 101. This causes a situation in which the output from 108 or the like changes, and causes deterioration in sensor accuracy.

The present invention has been made in view of the above problems, and suppresses the fluctuation of the rotation zero point and acts on the shaft by making the central axes of the excitation and detection coils coincide with the axis of the shaft. An object of the present invention is to provide a magnetostrictive torque sensor capable of accurately detecting torque.

[0010]

In order to solve the above problems and to achieve the above object, a magnetostrictive torque sensor of the present invention is provided with a magnetostrictive material provided on a shaft and corresponding to the magnetostrictive material. The bobbin provided with the excitation and detection coils includes one or more bearings that rotatably support the shaft with the central axes of the excitation and detection coils aligned with the axis of the shaft. The part is integrally formed. Further, the bobbin may be made of ceramics.

As described above, since the bearing is integrally formed on the bobbin on which the excitation and detection coils are provided, the combination of tolerances is reduced, and the center axis of the excitation and detection coils and the axis of the shaft are easily aligned. Is possible
The shaft is not tilted with respect to the excitation and detection coils. In particular, when the bearing portions are formed at both ends (a plurality of locations) of the bobbin, it becomes possible to more reliably match the central axis of the excitation and detection coils with the axis of the shaft. Even when a plurality of exciting and detecting coils are formed, the exciting and detecting coils are arranged side by side on one bobbin so that the central axes of the exciting and detecting coils are displaced from each other. There is no.

When a torque is applied to the shaft while the shaft is rotating under the driving force of the machine body, a tensile force or a compressive force acts on the magnetostrictive material formed on the peripheral surface of the shaft. Then, the magnetic permeability is changed. The output from the excitation and detection coils changes based on this change in magnetic permeability, and the torque acting on the shaft can be measured by analyzing this. In addition,
The excitation and detection coil has two roles of exciting a magnetostrictive material and detecting a change in magnetic permeability. One that performs excitation and detection and one of the excitation coil and the detection coil Some use two coils.

Here, the magnetic material used for the magnetostrictive material is
When a tensile stress or a compressive stress acts, its magnetic permeability changes. The magnetostrictive torque sensor of the present invention utilizes such a property of the magnetic material, and when torque acts on the shaft, it excites and detects a change in magnetic permeability of the magnetostrictive material to which a tensile force or a compressive force acts. The torque acting on the shaft is measured by capturing the change in the output from the coil and analyzing this change in output.

Further, in a mode in which the magnetostrictive materials are lined up around the shaft at an angle of 45 ° obliquely downward and 45 ° obliquely upward from the axis 0 direction, when torque acts on the shaft, a tensile force is applied to one of the magnetostrictive materials. While acting, the compressive force acts on the other magnetostrictive material.
Therefore, by determining the difference between the output results from each excitation and detection coil corresponding to each magnetostrictive material, the influence of the force acting on the shaft in the axial direction can be excluded, and the torque acting on the shaft can be detected purely. It becomes possible to do.

[0015]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described with reference to FIG. As shown in FIG. 1, the shaft 1 is a machine body (not shown) such as a machining center.
It is driven to rotate by receiving a driving force from the magnetostrictive members 2 and 3 on its peripheral surface. The magnetostrictive materials 2 are provided in a state of being respectively embedded in the groove portions that are arranged obliquely downward from the axis 0 at 45 ° over the circumference of the shaft 1. In addition, the magnetostrictive material 3 is oriented diagonally upward 4 from the axis 0.
It is provided in such a manner that it is embedded in the groove portions arranged side by side around the shaft 1 at 5 °.

As shown in FIG. 2, the bobbin 4 is formed into a tubular shape which can penetrate the shaft 1 as a whole and has an annular recessed portion 4 formed over the entire circumference of the outer peripheral surface thereof.
Excitation and detection coils 5 and 6 are provided on each of a and b. These exciting and detecting coils 5 and 6 are
The magnetostrictive materials 2 and 3 are installed in a positional relationship corresponding to each. In this way, by providing the excitation and detection coils 5 and 6 on one bobbin 4, it is possible to avoid the deviation of the central axes of the excitation and detection coils 5 and 6.

The material of the bobbin 4 is made of resin such as plastic or ceramics, but is preferably made of ceramics. This is because, when the bobbin 4 is manufactured, the ceramics can improve the processing accuracy and can reduce the combination of the tolerances more than the resin, and the ceramics are less susceptible to the thermal expansion.

In addition, on both left and right ends of the inner peripheral surface of the bobbin 4,
Bearing mounting portions 7 and 8 (bearing portions) for mounting the bearings 9 and 10 are integrally formed. Then, as shown in FIG. 1, the bearings 9 and 10 are attached to the bearing mounting portions 7 and 8, and the bearings 9 and 10 are installed between the bobbin 4 and the shaft 1, whereby the shaft 1
Are rotatable relative to the bobbin 4.
In this way, the use of the two bearings 9 and 10 prevents the bobbin 4 from tilting with respect to the shaft 1, and thereby the axis 0 of the shaft 1 and the central axes of the excitation and detection coils 5 and 6 are set. Trying to match.

In addition, the bobbin 4 is not only attached by fitting it from the end of the shaft 1 in a state where it is integrally formed into a tubular shape, but also the bobbin 4 is preliminarily divided vertically (in a state of being divided in the axis 0 direction), The shaft 1 may be sandwiched and the two may be integrally mounted. further,
The bobbin 4 may be divided for each of the excitation and detection coils 5 and 6 and attached to the shaft 1 so that they are integrated.

Further, since the magnetostrictive materials 2 and 3 are positioned between the bearings 9 and 10, the shaft 1 of the magnetostrictive materials 2 and 3 and the bobbin 4 of the excitation and detection coils 5 and 6 are disposed.
The positional relationship between and is not easily changed, and the magnetostrictive members 2 and 3 are prevented from being bent by the bending force applied to the shaft 1 from the outside. However,
If the axis 0 of the shaft 1 and the central axes of the excitation and detection coils 5 and the like can be matched, two bearings 9 and 1
The number of bearings is not limited to 0, and one or three or more bearings may be used, for example.

Further, instead of the bearings 9 and 10, for example, bushings may be attached to the bearing mounting portions 7 and 8 to thereby rotatably support the shaft 1, and the bearing mounting portions 7 and 8 may be used as shaft bearing portions. Instead of forming it, for example, an annular protrusion that can directly rotate and support the shaft 1 may be formed as a bearing. in this case,
Similar to the above, one or two or more bearing portions may be formed.

A magnetic yoke 11 is attached to the outer peripheral surface of the bobbin 4 while covering the exciting and detecting coils 5 and 6. The magnetic yoke 11 has a function of confining the magnetic flux from the excitation and detection coils 5 and 6. The bobbin 4 including the magnetic yoke 11 is also included.
A case 12 is attached to the outer peripheral surface of the. As shown by the dotted line in FIG. 1, the case 12 is fixed to the machine body via a support portion 13, whereby the bobbin 4, the magnetic yoke 11 and the case 12 are fixed to the machine body, and the shaft 1 is opposed to each other. It will be rotated.

Here, the magnetic material used for the magnetostrictive materials 2 and 3 has a magnetic permeability that changes according to the strain when a tensile force or a compressive force is applied. On the other hand, the exciting and detecting coils 5, Reference numeral 6 changes the self-inductance according to the change in the magnetic permeability of the magnetic material, and changes the output therefrom. Therefore, the excitation and detection coils 5, 6
Will linearly correspond to the magnitude of the tensile force or the compressive force acting on the magnetostrictive materials 2 and 3.

Outputs from the excitation and detection coils 5 and 6 are input to a differential amplifier circuit (not shown) and then taken out of the torque sensor via a connection cable C. This differential amplifier circuit includes excitation and detection coils 5 and 6.
If each input value from is not output from here,
Excitation and detection coils 5, corresponding to changes in the magnetostrictive materials 2 and 3,
When different values are input from 6, the differential amplifier circuit outputs the difference between these values.

Next, the operating state of the magnetostrictive torque sensor configured as described above will be described. First, when the shaft 1 is rotationally driven by the driving force of the machine body, the shaft 1
Is rotated relative to the bobbin 4 while being rotatably supported by the bearings 9 and 10 because the bobbin 4 is fixed. A rotary cutting tool such as a drill or an end mill is attached to the shaft 1, and the rotary cutting tool is rotated about the axis 0 to perform cutting work.

When torque is applied to the rotary cutting tool during cutting and torque in the direction shown by the arrow in FIG. 1 is applied to the shaft 1, the torque causes the magnetostrictive material 2 (left side in FIG. 1) to be pulled. A force acts, and strain is generated by stretching it, while a compressive force acts on the magnetostrictive material 3 (on the right side in FIG. 1), and strain occurs when it is compressed. The outputs from the excitation and detection coils 5 and 6 respectively change according to this distortion, these outputs are input to the differential amplifier circuit, and the difference between the input values is output from the differential amplifier circuit.
Then, the torque acting on the shaft 1 is detected based on the output result.

Further, by the differential amplifier circuit, the magnetostrictive material 2,
Since the difference between the detection results corresponding to the strain of No. 3 is output, the influence of the force in the axis 0 direction on the shaft 1 (for example, the compressive force acting in the axial direction of the rotary cutting tool during cutting) can be excluded. It is possible to measure the torque acting purely on the shaft 1. Further, since the magnetostrictive members 2 and 3 of the shaft 1 are located between the bearings 9 and 10 attached to the bobbin 4, the shaft 1
Even when a force in the direction orthogonal to the axis 0 acts on the end portion of the shaft 1 and the bending force acts on the shaft 1, the magnetostrictive members 2 and 3 are prevented from bending by the bending force, and when the torque is measured, The influence of such bending force is also reduced.

The detection result of the torque becomes an element for detecting damage or wear of the rotary cutting tool by being analyzed by a computer or the like. By feeding back the detection result to the control system of the machine body, The driving state and the like are appropriately corrected to contribute to the optimization of the operation of the machine body.

In this way, the excitation and detection coils 5, 6 are
Is provided on one bobbin 4 in which the shaft 1 is rotatably supported by bearings 9 and 10, so that the central axes of the bobbins 4 are aligned with the axis 0. Therefore, the fluctuation of the rotation zero point is suppressed, and the sensor accuracy is ensured. Moreover, since the bobbin 4 is fixed to the machine body, the excitation and the output from the detection coil 5 and the like can be taken out regardless of the rotation of the shaft 1, and a highly reliable detection result is expected. The durability can be improved.

As shown in the figure, the present invention is not limited to the use of the magnetostrictive materials 2 and 3, and one (one aspect) magnetostrictive material may be used. In this case, one exciting and detecting coil is installed corresponding to the magnetostrictive material, and the torque acting on the shaft 1 is detected based on the output change from the exciting and detecting coil. However, when one excitation and detection coil is used, the detection result includes the influence of a force other than torque (a force acting on the shaft 1 in the direction of the axis 0). And the excitation and detection coils 5 and 6 are preferably provided.

The magnetostrictive material torque sensor of the present invention is, as described above, the shaft 1 to which the rotary cutting tool is attached.
The present invention is not limited to the detection of the torque acting on, but is also applied to the detection of the torque acting on the shaft of various machine tools and the like.

[0032]

According to the present invention, the axis line of the shaft and the central axis of the exciting and detecting coil are made to coincide with each other by integrally forming the bearing portion for rotatably supporting the shaft on the bobbin provided with the exciting and detecting coil. Therefore, it is possible to suppress the fluctuation of the rotation zero point caused by the deviation between the axis of the shaft and the central axis of the excitation and detection coils, and prevent the deterioration of the sensor accuracy. Furthermore, the number of parts is reduced compared to the conventional one, so that it is possible to reduce the combination of tolerances, and thus it is possible to easily secure the coincidence between the axis line of the shaft and the central axes of the excitation and detection coils. it can.
Also, even when installing multiple excitation and detection coils,
Since these excitation and detection coils are formed on a single bobbin, deviations of the center axes of the excitation and detection coils are prevented, and in the same way as above, matching with the axis of the shaft is ensured, respectively, and sensor accuracy is improved. Can be prevented from deteriorating.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view showing a bobbin.

FIG. 3 is a cross-sectional view showing one form of a conventional magnetostrictive torque sensor.

[Explanation of symbols]

 1 shaft 2, 3 magnetostrictive material 4 bobbin 5, 6 excitation and detection coil 7, 8 bearing mounting part (bearing part) 9, 10 bearing

Claims (2)

[Claims] 1. A magnetostrictive torque sensor comprising a magnetostrictive material provided on a shaft and an exciting and detecting coil installed corresponding to the magnetostrictive material, wherein the bobbin provided with the exciting and detecting coil is provided with the shaft. A magnetostrictive torque sensor, characterized in that one or more bearing portions are integrally formed to rotatably support the shaft with the central axes of the excitation and detection coils aligned with the axis of the. 2. The magnetostrictive torque sensor according to claim 1, wherein the bobbin is made of ceramics.