JPH1028354A - Motor with torque sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor with a torque sensor, capable of obtaining an accurate measured value of torque. SOLUTION: A motor with a torque sensor includes a rotating shaft 3 with a rotor 4 fixed at its central part, two bearings 13 and 14 on both sides of the rotor 4 for supporting the shaft 3, and two rows of magneto-strictive films 5A and 5B having reverse magneto-strictive effect. The films 5A and 5B have a plurality of slits, arranged along a circumferential line and located alternately opposite at a given angle in an elongated direction of the shaft 3. In addition, the motor includes two excitation and detection coils 6A and 6B, each disposing opposite to each magneto-strictive film 5A or 5B with a gap in between. The magneto-strictive films 5A and 5B are provided at the same distance from the bearing 13 or 14 on the rotor side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor having a built-in magnetostrictive torque sensor utilizing a reverse magnetostriction effect of a magnetic material.

[0002]

2. Description of the Related Art Conventionally, in a motor with a torque sensor having a built-in magnetostrictive torque sensor, a cylindrical stator 2 is provided inside a cylindrical frame 1 as shown in FIG. Is provided with a rotor 4 fixed to the rotating shaft 3. A load-side bracket 11 and a non-load-side bracket 12 are provided on both end surfaces of the frame 1.
Are provided with bearings 13 and 14, respectively. The rotating shaft 3 is supported by bearings 13 and 14. Rotor 4 and bearing 13
A magnetostrictive body having an inverse magnetostrictive effect is provided on the surface of the rotating shaft 3 between the two. This magnetostrictive body is composed of two rows of magnetostrictive films 5 each having a plurality of slits that are inclined in directions opposite to each other with respect to the longitudinal direction of the rotating shaft 3 and are aligned in the circumferential direction of the rotating shaft 3.
A, 5B. Excitation / detection coils 6A and 6B facing the magnetostrictive films 5A and 5B via air gaps are provided on the outer periphery of the magnetostrictive films 5A and 5B, and are attached to the load-side bracket 11 by the support portion 7. The torque sensor 8 has the magnetostrictive films 5A and 5B and the excitation / detection coils 6A and 6B configured as described above. The reason why the plurality of slits inclined at a constant angle are set in directions opposite to each other with respect to the length direction of the rotation axis is to detect the rotation direction of the rotation axis. As described above, as an example of the torque sensor using the reverse magnetostriction effect composed of the magnetostrictive film and the excitation / detection coil, the change in the magnetic permeability of the magnetostrictive film, which changes due to the stress of the rotating shaft, is detected as the change in the impedance of the two detection coils. Many magnetostrictive torque sensors that determine the torque applied to the rotating shaft based on the difference between the detection values of the two detection coils have been disclosed (for example, Japanese Patent Application Laid-Open No. 6-291).
384). As shown in FIG. 4, in the conventional example, a bearing 15 dedicated to the torque sensor is also provided on the rotor 4 side of the torque sensor 8 and attached to the load-side bracket 11 by the support 70. In this example, two bearings 13 and 15 support both sides of the magnetostrictive films 5A and 5B provided on the surface of the rotating shaft 3, so that bending stress is not applied to the portions where the magnetostrictive films 5A and 5B are provided. .

[0003]

However, in the prior art shown in FIG. 3, in addition to the output of the torque sensor generated due to the distortion caused by the rotational force generated by the rotor 4,
Due to the unbalance of the rotor 4 and the resulting centrifugal force, distortion due to bending stress is generated, and the output of the torque sensor is generated due to the distortion. The output of the torque sensor due to the bending stress has a different output value because the positions of the two rows of the magnetostrictive films 5A and 5B are at different distances from the bearing 13, and are not offset even if a difference value between the two detected values is taken. Therefore, there is a problem that an output is generated even when no torque is applied to the rotating shaft 4 by the motor, and the torque value cannot be accurately detected. In the prior art shown in FIG.
Since both sides of the magnetostrictive films 5A and 5B of the rotating shaft 3 are supported by 3 and 15 so that the bending stress is not applied to the portion where the magnetostrictive films 5A and 5B are provided, the output from the torque sensor 8 due to bending is Does not occur. However, there is a problem that the axial length of the bearing portion on the load side is almost doubled. Further, in the configuration shown in FIG. 4, the heat from the rotor 4 is hardly escaped by being surrounded by the two bearings, the temperature rise in the torque sensor portion becomes large, and the magnetostrictive films 5A, 5
There is a problem that a temperature gradient occurs between B and the torque detection accuracy decreases. An object of the present invention is to provide a motor with a high-precision torque sensor that can obtain an accurate torque detection value even when a bending stress is applied to a rotating shaft.

[0004]

According to a first aspect of the present invention, there is provided a motor with a torque sensor according to a first aspect of the present invention, wherein a rotating shaft having a rotor fixed to a central portion and the rotating shaft supported on both sides of the rotor. And two bearings that are provided on the surface of the rotating shaft and form a certain angle with respect to the longitudinal direction of the rotating shaft, and the fixed angles are opposite to each other and are aligned in the circumferential direction of the rotating shaft. In a motor with a torque sensor including two rows of magnetostrictive bodies having a plurality of slits and having an inverse magnetostrictive effect, and two excitation / detection coils respectively opposed to the magnetostrictive body via a gap, the magnetostrictive body includes:
The two bearings are disposed at equal distances from the two bearings on the rotor side. Further, in the motor with the torque sensor according to the second invention, the rotating shaft is made of a non-magnetic material, and the magnetostrictive body has a film formed on a surface of the rotating shaft. Further, in the motor with a torque sensor according to the third invention, the rotating shaft is made of a magnetic material having an inverse magnetostrictive effect, and the magnetostrictive body is formed by processing the slit on the surface of the rotating shaft. is there.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in the drawings. FIG. 1 is a side sectional view showing a first embodiment of the present invention. The configuration shown in the figure is almost the same as the conventional example. The configuration is such that a cylindrical stator 2 is provided inside a cylindrical frame 1, and a rotor 4 fixed to a rotating shaft 3 made of a nonmagnetic material such as stainless steel is provided inside the stator 2. I have. The rotating shaft 3 is connected to a load-side bracket 11 and a non-load-side bracket 12 provided on both end surfaces of the frame 1.
It is supported via bearings 13 and 14. On the other hand, the point different from the conventional example is as a magnetostrictive body having an inverse magnetostrictive effect.
Magnetostrictive films 5A and 5B having a plurality of slits that are inclined at a fixed angle in opposite directions to each other when viewed clockwise with respect to the length direction of the rotation shaft 3 and are aligned in the circumferential direction of the rotation shaft 3,
The rotors 4 are formed at positions where the distances from the bearings 13 and 14 on both sides of the rotor 4 are substantially equal to each other by a vacuum evaporation method or a plating method. That is, the magnetostrictive film 5A is arranged on the rotor 4 side near the bearing 13 and the magnetostrictive film 5B is arranged on the rotor 4 side near the bearing 14 so that the distances between the centers are almost equal to each other. I have. The excitation / detection coil 6A is attached to the load side bracket 11 by the support portion 7A so as to face the magnetostrictive film 5A via a gap,
The excitation / detection coil 6B is opposed to the magnetostrictive film 5B via a gap by the support portion 7B by the support portion 7B.
2 attached.

With this configuration, when a bending stress is generated in the rotating shaft 3 due to unbalance or centrifugal force, the bearing 13
And the distance from the bearing 14 to the magnetostrictive film 5B is the same, so that the same bending stress is generated in the magnetostrictive films 5A and 5B. Therefore, the difference between the detection values of the magnetostrictive films 5A and 5B becomes zero. In addition, the rotor 4 of the motor is moved from the magnetostrictive film 5.
Since the distances to A and 5B are almost the same, a temperature change occurs similarly, and does not affect the difference between the detected values. In order to confirm the effects of such bending stress and temperature change by experiments, as an experimental condition, a 5 μm-thick 90% Ni—Fe film was formed on the surface of the stainless steel rotating shaft 3 by sputtering.
The films were formed as magnetostrictive films 5A and 5B. Further, the excitation / detection coil 6 was formed by setting the excitation coil to 200 turns and the detection coil to 600 turns. Under these conditions, the motor was rotated up to 1000 revolutions per minute, and the output change was measured. As a result, no output based on bending was observed. Further, continuous operation was performed at 1,000 revolutions per minute for a long time, but no output change due to temperature change occurred. FIG. 2 is a side sectional view showing a second embodiment of the present invention. In the first embodiment, the example in which the magnetostrictive films 5A and 5B are formed as the magnetostrictive body on the surface of the rotating shaft 3 by a vacuum evaporation method or a plating method, but in this case, the rotating shaft made of maraging steel is used. The surface of the rotating shaft 3 is inclined directly at an angle in a direction opposite to each other when viewed clockwise with respect to the length direction of the rotating shaft 3 by machining or etching, and is aligned in the circumferential direction of the rotating shaft 3. Multiple slits 50A, 50B
To form a magnetostrictive body. The experimental result in the case of the second embodiment was almost the same as that of the first embodiment.

[0007]

As described above, according to the present invention, a magnetostrictive body having a reverse magnetostrictive effect, which constitutes a torque sensor, is disposed at a position equidistant from two bearings supporting a rotating shaft. Even if there is no dedicated bearing for the sensor, it is not affected by bending stress, so the output of the torque sensor is not affected by bending, and the accuracy can be prevented from lowering due to heat generation of the motor. There is an effect that it is possible to provide a motor with a torque sensor that can obtain a high torque detection value.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a first embodiment of the present invention.

FIG. 2 is a side sectional view showing a second embodiment of the present invention.

FIG. 3 is a side sectional view showing a conventional example.

FIG. 4 is a side sectional view showing another conventional example.

[Explanation of symbols]

1: frame, 11: load side bracket, 12: anti-load side bracket, 13, 14: bearing, 2: stator, 3: rotating shaft, 4: rotor, 5A, 5B: magnetostrictive film, 50A, 50
B: slit, 6A, 6B: excitation / detection coil, 7A,
7B: Support, 8: Torque sensor

Claims (3)

[Claims] A rotating shaft having a rotor fixed at a central portion, two bearings supporting the rotating shaft on both sides of the rotor,
A plurality of slits are provided on the surface of the rotating shaft, form a certain angle with respect to the longitudinal direction of the rotating shaft, the fixed angles are opposite to each other, and are aligned in the circumferential direction of the rotating shaft. Two rows of magnetostrictive bodies having an inverse magnetostrictive effect;
In a motor with a torque sensor including two excitation / detection coils opposed to the magnetostrictive body via a gap, respectively, the magnetostrictive bodies are arranged at equal distances from the two bearings to the rotor. A motor with a torque sensor. 2. The rotating shaft is made of a non-magnetic material, and the magnetostrictive body has a film formed on the surface of the rotating shaft.
A motor with a torque sensor as described. 3. The motor with a torque sensor according to claim 1, wherein the rotating shaft is made of a magnetic material having an inverse magnetostrictive effect, and the magnetostrictive body is formed by processing the slit on a surface of the rotating shaft.