JP2007108013A - Harmonic Drive (registered trademark) reducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a harmonic drive (R) reducer having a torque sensor which can be incorporated easily and has high reliability. <P>SOLUTION: The harmonic drive (R) reducer is provided with a flexspline having teeth. The flexspline 1 is magnetized in the direction of the teeth. A magnetic field sensor 2 for detecting a change in a leakage magnetic field on the basis of a change in the magnetic characteristics of the flexspline 1 is placed on the outer periphery of the teeth in a noncontact manner. A torque transmitted by the flexspline is detected by the output of the magnetic field sensor 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a Harmonic Drive (registered trademark) speed reducer used as a speed reducer for an industrial robot, and more particularly to a function having a function of detecting a transmitted torque.

  Harmonic Drive (registered trademark) reducers have been widely used in industrial robots and the like, and those incorporating a torque sensor have been developed. The first conventional example will be described with reference to FIG. FIG. 4 is a diagram for explaining the configuration of the main part of the Harmonic Drive (registered trademark) reducer. 103 is a film formed on the outer peripheral surface of the flexspline, and 102 is provided on the fixed side via the film 103 and a gap. The torque detecting coil. The film 103 is coated on the flexspline with a thickness of 0.1 to 30 μm by a sputtering method or the like, and the film 103 and the coil 102 constitute a magnetostrictive torque sensor. Since such a torque sensor is incorporated in a part of the flexspline and applied to a Harmonic Drive (registered trademark) reducer, it is not necessary to take a new space for incorporating the torque sensor in the output shaft, and the length of the output shaft There is an advantage that the size can be reduced without increasing the length and the robot can be reduced in size (for example, see Patent Document 1).

Next, a wave reducer equipped with a torque sensor will be described as a second conventional example with reference to FIGS. FIG. 5 is a diagram showing an internal configuration of a wave reducer provided with a torque sensor, and is a perspective view with a part cut away. FIG. 6 is a cross-sectional view of the main part including the torque sensor.
In FIG. 1, 203 is an input shaft supported by a bearing 208a, 213 is an output shaft supported by a bearing 208b, and a speed reduction mechanism that reduces the rotation of the input shaft 203 and transmits it to the output shaft 213 is provided with a support case 201 and a flange. It is arranged in a space surrounded by the cover 202. The output shaft 213 is connected to a cylindrical flex spline member 210 via a disk-shaped bottom plate 212 a, and an internal tooth circular spline 201 a is interposed between the flex spline member 210 and the input shaft 203. By the interposition, the rotation of the input shaft 203 can be decelerated with a large reduction ratio and transmitted to the output shaft 213. A torque sensor 220 is provided outside the disk-shaped bottom plate 212a and is covered and protected by a protective cover 215 (see, for example, Patent Document 2). FIG. 6 is a cross-sectional view showing details of a portion where the torque sensor 220 is provided. The torque sensor 220 extends in the circumferential direction and is bonded to the outer surface of the disk-shaped bottom plate 212a, which is an elastic body, and includes a first magnetic layer 222 whose magnetostriction characteristics change according to elastic deformation of the disk-shaped bottom plate 212a, and a first magnetic layer 222. It is composed of a flat coil 223 which is disposed on one magnetic layer and detects a change in magnetostriction characteristics, and a second magnetic layer 224 which is disposed so as to cover the flat coil. Since the configuration is as described above, torque measurement can be performed without adding a new elastic element or changing the mechanism, and without using a strain gauge.
JP-A-7-103291 (page 3, FIG. 1) Japanese Patent No. 3451130 (page 7, FIGS. 1 and 4)

However, the harmonic drive (registered trademark) speed reducer of the first conventional example can detect torque by arranging a coil for torque detection on the outer periphery of the flexspline via a gap. Since it is necessary to arrange a coil on the outer periphery of the coil, it takes time to arrange the coil.
The wave reducer of the second conventional example can measure the torque by attaching a torque sensor to the disk-shaped bottom plate. However, depending on how the magnetic body is attached, the reliability of the sensor is low and the length is long. There was a problem that the magnetic material peeled off when used for a long time.
The present invention has been made in view of such problems, and a harmonic drive (registered trademark) having a highly reliable torque sensor that can be incorporated in the outer surface of the flexspline without contact and relatively easily. An object is to provide a reduction gear.

In order to solve the above problem, the first invention is a harmonic drive (registered trademark) speed reducer equipped with a flexspline having teeth, wherein the flexspline is magnetized in the direction of the teeth, and the flexspline magnetic characteristics are changed. A magnetic field sensor for detecting a change in the leakage magnetic field is disposed on the outer surface of the tooth in a non-contact manner, and the torque transmitted by the flexspline is detected by the output of the magnetic field sensor.
The second invention is a Harmonic Drive (registered trademark) speed reducer provided with a flexspline having teeth, wherein the flexspline has a second tooth formed in parallel to the toothless portion of the flexspline. A magnetic field sensor for detecting a change in leakage magnetic field based on a change in characteristics is disposed in a non-contact manner on the outer surface of the second tooth, and a torque transmitted by the flexspline is detected by an output of the magnetic field sensor. .
The third invention is characterized in that the magnetic field sensor is any one of an MI sensor, an MR sensor, and a Hall element, and the fourth invention is characterized in that the magnetic field sensor is arranged in a circular spline.

According to the first invention, the flexspline is magnetized in the direction of the tooth, and the magnetic field sensor is disposed in a non-contact manner on the outer surface of the tooth, so that the magnetic field sensor can be incorporated relatively easily.
According to the second invention, the flexspline is formed in a portion where there are no teeth, the second teeth are formed in parallel with the teeth, and the magnetic field sensor is arranged in a non-contact manner on the outer surface of the second teeth. Sensors can be incorporated relatively easily.
According to the third invention, since the magnetic field sensor is any one of the MI sensor, the MR sensor, and the Hall element, the reliability of the torque sensor can be improved.
According to the fourth invention, since the magnetic field sensor is disposed in the circular spline, the reliability of the torque sensor can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a harmonic drive (registered trademark) speed reducer according to the present invention, and is a perspective view in which main parts are partially cut away. In the figure, 1 is a flexspline, 2 is a magnetic field sensor, 3 is a wave generator, and 4 is a circular spline. The flexspline 1 corresponds to the flexspline in FIG. 4, and FIG. 2 is a diagram for explaining the magnetization direction of the flexspline 1. The torque sensor shown in FIG. 1 is composed of a magnetic field sensor 2 and a flexspline 1. As shown in FIG. 2, the magnetic field sensor is not in contact with the outer surface of the flexspline member and is uniform over the entire circumference of the circular spline. It is arranged. The configuration of the main part shown in FIG. 1 will be described in detail below.

  An internal tooth circular spline is formed in a cylindrical support case (not shown), and a torque sensor is built in a space surrounded by the support case and a flange cover (not shown). The flex spline 1 is rotatably supported by a bearing. The support case and the flange cover are normally fixedly supported, and a Harmonic Drive (registered trademark) speed reducer decelerates the rotation of the input shaft with a very large reduction ratio such as several tens to hundreds and transmits it to the output shaft.

  An input shaft (not shown) is rotatably supported by a flange cover (not shown) via a bearing (not shown), one end projects outward, and the other end is coupled to an elliptic disk cam (not shown). A plurality of pressing balls are arranged at equal intervals along the outer periphery of the elliptical cam, and the wave generator 3 is configured. An output shaft (not shown) is rotatably supported by a support case (not shown) via a bearing (not shown), one end protrudes outward from the side surface of the support case, and the other end is a flex spline 1 disposed in the support case. Is bound to.

The flexspline 1 is made of an elastic material, and an external tooth flexspline (not shown) is provided at the tip. The external tooth flexspline and the output shaft are coupled by a thin cylindrical coupling having a disk-shaped bottom (not shown). Inside the external tooth flex spline, there is a wave generator along its inner peripheral surface, which meshes with the internal tooth circular spline.
When the ellipsoidal cam pushes the ball outward on the outer surface, the flexspline is elastically deformed into an ellipse. Two portions corresponding to the long axis of the ellipse are pushed out to the outermost side and mesh with the internal circular splines.

Next, the operation of the harmonic drive (registered trademark) reducer configured as described above will be described. When the input shaft rotates, the elliptical cam of the wave generator also rotates, and the meshing position of the flex spline and the internal circular spline also rotates. Here, if the number of teeth of the flexspline is two less than the number of teeth of the internal circular spline, if the input shaft rotates once, the flexspline member is equal to the number of different teeth, that is, the number of teeth of two. It only rotates and is decelerated with a very large reduction ratio.
When the flexspline member is elastically deformed when transmitting torque, a leakage magnetic field based on a change in magnetic characteristics changes. This change in the leakage magnetic field is detected by a magnetic field sensor. Since the change in the leakage magnetic field is proportional to the elastic deformation of the flexspline member, the torque can be obtained by calculation from the detected change in the leakage magnetic field.

  FIG. 3 is a diagram illustrating another configuration of the torque sensor. The difference from FIG. 2 is that the second tooth 5 is provided in the flex spline 1 of FIG. FIG. 2 differs from FIG. 2 only in the position of the magnetic field sensor and the teeth facing each other through the air gap, and operates in the same manner as in the first embodiment and can detect torque.

Although the magnetic field sensor is used in the above embodiment, other types of sensors may be used according to the spirit of the present invention. Instead of the magnetic field sensor, any of an MI sensor, MR sensor, or Hall element may be used. Since any sensor can detect a change in the leakage magnetic field based on a change in the magnetic characteristics of the flexspline member, a torque to be transmitted by calculation can be obtained.
In addition, the magnetic field sensor may be arranged so as to be uniform over the entire circumference of the circular spline while not contacting the outer surface of the flexspline member. Even with such an arrangement, the transmitted torque can be detected in the same manner as in the first and second embodiments.

Partially cutaway perspective view of the main part of the harmonic drive (registered trademark) speed reducer mechanism of the present invention Diagram explaining the torque sensor The figure explaining other torque sensors Flexspline of conventional harmonic drive (registered trademark) reducer Conventional wave reducer Explanatory drawing of the main part of FIG.

Explanation of symbols

1 Flex Spline 2 Magnetic Field Sensor 3 Wave Generator 4 Circular Spline 5 Machined Teeth

Claims (4)

In a Harmonic Drive (registered trademark) reducer with a flexspline with teeth,
The flexspline is magnetized in the direction of the teeth,
A magnetic field sensor for detecting a change in a leakage magnetic field based on a change in magnetic properties of the flexspline is disposed in a non-contact manner on the outer surface of the tooth;
A harmonic drive (registered trademark) speed reducer that detects torque transmitted by the flexspline based on an output of the magnetic field sensor. In a Harmonic Drive (registered trademark) reducer with a flexspline with teeth,
The flexspline has second teeth formed in parallel to the teeth-free portion,
A magnetic field sensor for detecting a change in a leakage magnetic field based on a change in magnetic properties of the flexspline is disposed in a non-contact manner on an outer surface of the second tooth;
A harmonic drive (registered trademark) speed reducer that detects torque transmitted by the flexspline based on an output of the magnetic field sensor.   The harmonic drive (registered trademark) speed reducer according to claim 1, wherein the magnetic field sensor is any one of an MI sensor, an MR sensor, and a Hall element.   The harmonic drive (registered trademark) speed reducer according to claim 1, wherein the magnetic field sensor is disposed in a circular spline.

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