Patent Description:
A torque sensor includes a first structure to which torque is applied, a second structure from which torque is output, and a plurality of strain parts serving as beams connecting the first structure and the second structure, and a plurality of strain gauges serving as sensor elements are arranged on the strain parts. A bridge circuit is constituted by these strain gauges (cf. , for example, Patent Literature <NUM>, <NUM>, and <NUM>).

In a torque amount converter which measures a torque generated in an output unit of an engine, etc., of an automobile, a technique for reducing an influence of a bending stress other than torque has been developed (cf. , for example, Patent Literature <NUM>).

Another torque sensor mount is disclosed in <CIT> which includes an outer tubular structure connected through a plurality of canted ribs to an an inner tubular structure. Posts are placed outside the outer tubular structure.

A disc shaped torque sensor according to the invention is defined by claim <NUM> and comprises a first structure, a second structure, and a third structure between the first structure and the second structure, and is equipped with a strain body serving as a strain sensor, and a strain gauge, between the first structure and the second structure.

When the first structure is fixed to, for example, a base of a robot arm and the second structure is fixedly used on, for example, an arm of the robot arm, a bending moment accompanying a transfer weight of the robot arm, a distance to the load and acting acceleration, and a load of its reaction force are applied to the torque sensor, other than the torque.

When a torque sensor is attached to a robot arm, a center of axis of the torque sensor needs to be aligned with a center of axis of, for example, an arm or a base of the robot arm.

When a shape of a first structure of the torque sensor is assumed to be, for example, a column and a shape of the base of the robot arm is assumed to be a cylinder, the centers of axes are made to coincide with each other by fitting the column into the cylinder. In this case, however, the axes are coincident with each other, but it is unclear which parts of the column and the cylinder are exactly in contact with each other. That is, the column and the cylinder are not perfect circles, and each of the outer diameter of the column and the inner diameter of the cylinder is irregular. For this reason, the outer surface of the column and the inner surface of the cylinder are expected to be in contact with each other at several points at random.

Thus, in a case where the first structure of the torque sensor, and the base and the arm of the robot arm are brought into contact with each other at several points at random, when the bending moment other than torque, and the translational force are applied to the torque sensor, the first structure and the second structure are asymmetrically deformed, and the strain sensor is deformed asymmetrically due to its deformation, and an output is emitted from the sensor.

When a bending moment and a load (X-axis direction Fx, Y-axis direction Fy, and Z-axis direction Fz), i.e., a translational force other than the torque is applied to the torque sensor, distortion corresponding to displacement occurs in the plurality of strain sensors provided in the torque sensor. In general, a bridge circuit of a torque sensor is configured to output a voltage against a force in a torque direction and not to output a voltage against a force in a direction other than the torque. However, if the first structure or the second structure is deformed asymmetrically, an asymmetric strain is generated at a plurality of strain sensors provided in the torque sensor. Besides this, a sensor output is generated and the detection accuracy of the torque sensor is degraded due to the axial interference.

Embodiments described herein aim to provide a mounting structure for a torque sensor capable of improving a detection accuracy of a torque sensor.

According to the embodiment, there is provided a mounting structure for a torque sensor comprising: a torque sensor comprising a first structure, a second structure, a third structure provided between the first structure and the second structure, and at least two senor units provided between the first structure and the second structure; and a plurality of contact portions provided on one of the first structure and a first attachment portion and one of the second structure and a second attachment portion, and being in contact with another of the first structure and the first attachment portion and another of the second structure and the second attachment portion.

Mode for Carrying Out the Invention Embodiments will be described hereinafter with reference to the accompanying drawings. In the drawings, the same elements are denoted by the same reference numerals.

First, a robot arm <NUM> and a torque sensor <NUM> to which the embodiments are applied will be described with reference to <FIG>.

<FIG> shows an example of an articulated robot, i.e., the robot arm <NUM>. The robot arm <NUM> comprises, for example, a base <NUM>, a first arm <NUM>, a second arm <NUM>, a third arm <NUM>, a fourth arm <NUM>, a first drive unit <NUM> serving as a drive source, a second drive unit <NUM>, a third drive unit <NUM>, and a fourth drive unit <NUM>. However, the structure of the robot arm <NUM> is not limited thereto, but can be modified.

The first arm <NUM> is provided to be rotatable relative to the base <NUM> by the first drive unit <NUM> provided in a first joint J1. The second arm <NUM> is provided to be rotatable relative to the first arm <NUM> by the second drive unit <NUM> provided in a second joint J2. The third arm <NUM> is provided to be rotatable relative to the second arm <NUM> by the third drive unit <NUM> provided in a third joint J3. The fourth arm <NUM> is provided to be rotatable relative to the third arm <NUM> by the fourth drive unit <NUM> provided in a fourth joint J4. A hand and various tools (not shown) are mounted on the fourth arm <NUM>.

Each of the first drive unit <NUM> to the fourth drive unit <NUM> comprises, for example, a motor, a speed reducer, and a torque sensor, which will be described later.

<FIG> shows an example of a disk-shaped torque sensor <NUM> applied to the present embodiment. The torque sensor <NUM> comprises a first structure <NUM>, a second structure <NUM>, a plurality of third structures <NUM>, a first strain sensor <NUM> and a second strain sensor <NUM> serving as sensor units, and the like.

The first structure <NUM> and the second structure <NUM> are formed in an annular shape, and a diameter of the second structure <NUM> is smaller than a diameter of the first structure <NUM>. The second structure <NUM> is arranged concentrically with the first structure <NUM>, and the first structure <NUM> and the second structure <NUM> are connected by the third structures <NUM> serving as a plurality of beams arranged radially. The plurality of third structures <NUM> transmit torque between the first structure <NUM> and the second structure <NUM>. The second structure <NUM> has a hollow portion 42a and, for example, a line (not shown) is passed through the hollow portion 42a.

The first structure <NUM>, the second structure <NUM>, and the plurality of <NUM> structures <NUM> are formed of a metal, for example, stainless steel. However, a material other than metal can be used if a mechanically sufficient strength can be obtained for the applied torque. The first structure <NUM>, the second structure <NUM>, and the plurality of <NUM> structures <NUM> have, for example, the same thickness. The mechanical strength of the torque sensor <NUM> is set based on the thickness, width, and length of the third structures <NUM>.

The first strain sensor <NUM> and the second strain sensor <NUM> are provided between the first structure <NUM> and the second structure <NUM>. More specifically, one end of the strain body 44a constituting the first strain sensor <NUM> and one end of the strain body 45a constituting the second strain sensor <NUM> are joined to the first structure <NUM>, and the other ends of the strain bodies 44a and 45a are joined to the second structure <NUM>. The thickness of the strain bodies 44a and 45a is smaller than the thickness of the first structure <NUM>, the second structure <NUM>, and the plurality of third structures <NUM>.

A plurality of strain gauges (not shown) serving as sensor elements are provided on each of the surfaces of the strain bodies 44a and 45a. A first bridge circuit is composed of the sensor elements provided on the strain body 44a, and a second bridge circuit is composed of the sensor elements provided on the strain body 45a. That is, the torque sensor <NUM> comprises two bridge circuits.

In addition, the first strain sensor <NUM> and the second strain sensor <NUM> are arranged at symmetrical positions with respect to the center of the first structure <NUM> and the second structure <NUM> (the center of action of the torque). In other words, the first strain sensor <NUM> and the second strain sensor <NUM> are arranged on the diameter of the annular first structure <NUM> and second structure <NUM>.

The first strain sensor <NUM> (strain body 44a) is connected to a flexible substrate <NUM>, and the second strain sensor <NUM> (strain body 45a) is connected to a flexible substrate <NUM>. The flexible substrates <NUM> and <NUM> are connected to a printed circuit board (not shown) covered with a cover <NUM>. An operational amplifier for amplifying output voltages of two bridge circuits is arranged on the printed circuit board. Since the circuit configuration is not essential to the embodiment, descriptions thereof will be omitted.

<FIG> show a first embodiment. The torque sensor <NUM> is provided in, for example, the first drive unit <NUM> of the robot arm <NUM>. However, the torque sensor <NUM> can also be provided in, for example, the second drive unit <NUM> to the fourth drive unit <NUM> of the robot arm <NUM>.

In <FIG>, the first structure <NUM> of the torque sensor <NUM> is fixed to the first arm <NUM> by a plurality of bolts <NUM>. That is, a plurality of bolts <NUM> are inserted into the flange 32a of the first arm <NUM>, and the bolts <NUM> are screwed onto the surface of the first structure <NUM>. For this reason, a part of the back surface of the flange 32a of the first arm <NUM> is fixed to the surface of the first structure <NUM>.

The first drive unit <NUM> includes, for example, a motor 36a and a speed reducer 36b. The speed reducer 36b comprises, for example, a casing 36b-<NUM>, an output shaft 36b-<NUM>, a bearing 36b-<NUM>, and a plurality of gears (not shown). The output shaft 36b-<NUM> is connected to a shaft 36a-<NUM> of the motor 36a via a plurality of gears (not shown) and is provided to be rotatable with respect to the casing 36b-<NUM> by the bearing 36b-<NUM>. The motor 36a is provided in the casing 36b-<NUM> of the speed reducer 36b, and the casing 36b-<NUM> is fixed to, for example, the base <NUM>.

The second structure <NUM> of the torque sensor <NUM> is connected to the output shaft 36b-<NUM> of the speed reducer 36b by a plurality of bolts <NUM>. That is, the back surface of the second structure <NUM> is fixed to the surface of the output shaft 36b-<NUM>.

In contrast, as shown in <FIG> and <FIG>, for example, a vertical inner side surface (hereinafter simply referred to as a side surface) 32b is provided on a back surface, around the back surface of the flange 32a. The side surface 32b and the back surface form, for example, a step part. The side surface 32b is a surface that is parallel to an outer peripheral surface of the torque sensor <NUM>, i.e., an outer peripheral surface of the first structure <NUM>, and is separated from an outer peripheral surface of the first structure <NUM> by a predetermined distance L1.

More specifically, as shown in <FIG>, a step part 41a is provided at an outer peripheral part of the first structure <NUM>, and a side surface 41b of the step part 41a is spaced apart from the side surface 32b of the flange 32a by the distance L1. The side surface 41b of the step part 41a is also hereinafter referred to as the side surface 41b of the first structure <NUM>.

As shown in <FIG>, a plurality of pins <NUM> serving as first contact portions are provided on an outer peripheral portion of the first structure <NUM>. The number of pins <NUM> is even, for example, four. The number of pins <NUM> is larger than the number of the strain bodies 44a and 45a or equal to the number of the strain bodies 44a and 45a.

Four pins <NUM> are arranged at equal intervals on the outer periphery of the first structure <NUM>. More specifically, the pins <NUM> are provided on a straight line connecting the first strain sensor <NUM> and the second strain sensor <NUM> and on a straight line orthogonal to this straight line. However, the number and arrangement of pins <NUM> are not limited thereto. For example, the first strain sensor <NUM> and the second strain sensor <NUM> may be arranged at positions displaced by <NUM> degrees relative to four pins <NUM> shifted by <NUM> degrees.

Alternatively, for example, when four strain sensors are used, the four strain sensors may be arranged at the same angle as the four pins <NUM> or may be arranged at positions shifted from the four pins <NUM> by <NUM> degrees.

The pin <NUM> is formed of, for example, a cylindrical metal and, as shown in <FIG>, one end of the pin <NUM> is inserted into the bottom part 41c of the step part 41a. More specifically, the pin <NUM> is press-fitted in an axial direction orthogonal to the surface of the torque sensor <NUM>, and the side surface of the pin <NUM> is in contact with the side surface 41b of the step part 41a. The pin <NUM> is not limited to metal, and can be formed of resin.

The diameter of the pin <NUM> is set to be equal to the distance L1 between the side surface 32b of the flange 32a and the side surface 41b of the step part 41a. For this reason, the side surfaces of four pins <NUM> are in line contact with the side surface 32b of the flange 32a, and the side surfaces of four pins <NUM> are in line contact with the side surface of the first structure <NUM> of the torque sensor <NUM>. In other words, the side surface 41b of the first structure <NUM> of the torque sensor <NUM> is not in contact with the flange 32a of the first arm <NUM> except for the portions of four pins <NUM>.

In addition, a plurality of pins <NUM> are provided as second contact portions, on the back surface of the second structure <NUM> of the torque sensor <NUM>. The number of pins <NUM> is even, for example, four, similarly to the pins <NUM>. As shown in <FIG>, four pins <NUM> are arranged at regular intervals on the second structure <NUM>. The arrangement of the pins <NUM> is similar to that of the pins <NUM>. More specifically, the pins <NUM> are provided on a straight line connecting the first strain sensor <NUM> and the second strain sensor <NUM> and on a straight line orthogonal to the straight line. However, the number and arrangement of the pins <NUM> are not limited thereto.

Similarly to the pin <NUM>, the pin <NUM> is formed of, for example, a cylindrical metal and, as shown in <FIG>, one end of the pin <NUM> is inserted (press-fitted) into the back surface of the second structure <NUM>. The pin <NUM> can also be formed of a resin material, similarly the pin <NUM>.

The diameter of the pin <NUM> is equal to that of the pin <NUM>, and the side surface of the pin <NUM> is in line contact with the side surface of the output shaft 36b-<NUM> of the speed reducer 36b. For this reason, the side surface of the output shaft 36b-<NUM> is connected to the second structure <NUM> of the torque sensor <NUM> via four pins <NUM>. In other words, the second structure <NUM> of the torque sensor <NUM> is not in contact with the side surface of the output shaft 36b-<NUM>, except for the parts of four pins <NUM>.

In the above-described structure, when the speed reducer 36b is driven by the motor 36a, a force in the torque (Mz) direction is applied to the torque sensor <NUM>. The first structure <NUM> of the torque sensor <NUM> is displaced in the torque (Mz) direction relative to the second structure <NUM>. In the torque sensor <NUM>, when the first structure <NUM> is displaced relative to the second structure <NUM>, an electric signal is output from the first strain sensor <NUM> and the second strain sensor <NUM>, and the torque can be detected.

In contrast, the side surface of the first structure <NUM> of the torque sensor <NUM> is in contact with the flange 32a of the first arm <NUM> at the parts of the four pins <NUM> and is not in contact with the flange 32a of the first arm <NUM> at parts other than the pins <NUM>. Furthermore, the second structure <NUM> of the torque sensor <NUM> is in contact with the side surface of the output shaft 36b-<NUM> at the parts of the four pins <NUM> and is not in contact with the side surface of the output shaft 36b-<NUM> at parts other than the pins <NUM>. Therefore, when a bending moment or a translational force in directions (Mx, My) other than the torque is generated on the first arm <NUM> by the operations of the first arm <NUM> to the fourth arm <NUM>, the bending moment or the translational force acts on the torque sensor <NUM> via the pins <NUM> and the pins <NUM>. However, the first structure <NUM> is in contact with the flange 32a of the first arm <NUM> by four pins <NUM>, and the second structure <NUM> is in contact with the output shaft 36b-<NUM> by four pins <NUM>. For this reason, the first structure <NUM> can be deformed with good balance with respect to the second structure <NUM>, and the strain body 44a constituting the first strain sensor <NUM> and the strain body 45a forming the second strain sensor <NUM> can be deformed symmetrically. Therefore, in the first strain sensor <NUM> and the second strain sensor <NUM>, the output of the signals to the bending moment and the translational force in the direction (Mx, My) other than the torque is suppressed.

According to the first embodiment, the first structure <NUM> of the torque sensor <NUM> is in line contact with, for example, the side surface 32b of the first arm <NUM> serving as the first attachment portion via four pins <NUM> serving as the first contact portions, and the second structure <NUM> is in line contact with the side surface of the output shaft 36b-<NUM> of the speed reducer 36b provided on the base <NUM> serving as the second attachment portion via four pins <NUM> serving as the second contact portions. For this reason, when the bending moment and the translational force are generated in the directions (Mx, My) other than the torque on the first arm <NUM>, the first structure <NUM> of the torque sensor <NUM> is deformed with good balance with respect to the second structure <NUM>, and the strain body 44a of the first strain sensor <NUM> and the strain body 45a of the second strain sensor <NUM> are deformed symmetrically. For this reason, output of the signals to the bending moment and the translational force in the directions (Mx, My) other than the torque can be suppressed. Therefore, the interference of the other axis can be reduced and the detection accuracy of the torque can be improved.

For example, when a configuration without a plurality of pins <NUM> is assumed, the side surface of the first structure <NUM> of the torque sensor <NUM> and the side surface of the first arm <NUM> are not shaped in a perfect circle, but are slightly deformed as viewed microscopically. For this reason, the side surface of the first structure <NUM> and the side surface of the first arm <NUM> are in contact with each other at a plurality of parts. If the side surface of the first structure <NUM> and the side surface of the first arm <NUM> are fully and uniformly in contact with each other, the strain body 44a constituting the first strain sensor <NUM> and the strain body 45a constituting the second strain sensor <NUM> generate strain symmetrical to the bending moment and the translational force other than the torque applied to the torque sensor <NUM>. However, when the side surface of the first structure <NUM> and the side surface of the first arm <NUM> are not on, for example, a straight line connecting the first strain sensor <NUM> and the second strain sensor <NUM> or a straight line perpendicular to this straight line, but are in contact at three points of non-regular intervals, the deformation of the strain body 44a and the strain body 45a becomes asymmetrical and a signal is generated.

However, when the side surface of the first structure <NUM> and the side surface of the first arm <NUM> are in contact with each other via four pins <NUM>, and when the strain body 44a and the strain body 45a are arranged to correspond to two pins <NUM> arranged on a diameter, similarly to the first embodiment, the strain body 44a and the strain body 45a generate strain symmetrical to the bending moment and the translational force other than the torque applied to the torque sensor <NUM>. For this reason, the torque sensor <NUM> can suppress the generation of signals for the bending moment and translational force other than the torque. Therefore, the detection accuracy of the torque can be improved.

In the above-described first embodiment, a plurality of pins <NUM> are provided in the first structure <NUM> of the torque sensor <NUM>, and a plurality of pins <NUM> are provided in the second structure <NUM> of the torque sensor <NUM>. However, the present invention is not limited thereto.

In the second embodiment, one ends of the plurality of pins <NUM> are inserted (press-fitted) into the flange 32a of the first arm <NUM>, and one ends of the plurality of pins <NUM> are inserted (press-fitted) into, for example, the output shaft 36b-<NUM> of the speed reducer 36b.

The side surfaces of the pins <NUM> are in contact with the side surface of the first structure <NUM> of the torque sensor <NUM> and the side surface 32b of the flange 32a. The side surface of the pin <NUM> is in contact with the side surface 42c of the step part 42b provided on the second structure <NUM> of the torque sensor <NUM>, and the side surface 36b-<NUM> constituting the step part 36b-<NUM> of the output shaft 36b-<NUM>.

According to the second embodiment, the first structure <NUM> of the torque sensor <NUM> is in contact with, for example, the side surface 32b of the first arm <NUM> serving as the first attachment portion via a plurality of pins <NUM> serving as the first contact portions, and the second structure <NUM> is in contact with the side surface 36b-<NUM> of the output shaft 36b-<NUM> of the speed reducer 36b provided on the base <NUM> serving as the second attachment portion via a plurality of pins <NUM> serving as the second contact portions. Therefore, in the second embodiment, too, the interference of the other axis can be reduced and the detection accuracy of the torque can be improved, similarly to the first embodiment.

<FIG> and <FIG> show a third embodiment.

In the first and second embodiments, the plurality of pins <NUM> are provided in the direction orthogonal to the surface of the torque sensor <NUM>. However, the present invention is not limited thereto.

As shown in <FIG> and <FIG>, in the third embodiment, a plurality of pins <NUM> are press-fitted into the side surface of the first structure <NUM> of the torque sensor <NUM>. In other words, one ends of the pins <NUM> are press-fitted into the side surface of the first structure <NUM> along the diameter direction of the torque sensor <NUM>.

The other ends of the pins <NUM> are processed into a spherical shape and are in point contact with the side surface 32b of the flange 32a of the first arm <NUM>.

A plurality of pins <NUM> are provided on the side surface of the first structure <NUM> of the torque sensor <NUM>, but the present invention is not limited thereto.

As represented by a broken line in <FIG>, for example, one ends of the plurality of pins <NUM> may be press-fitted into the side surface <NUM> b of the flange 32a, and the other ends in the spherical shape may be brought into point contact with the side surface of the first structure <NUM> of the torque sensor <NUM>.

According to the third embodiment, a plurality of pins <NUM> are provided on the side surface of the first structure <NUM> of the torque sensor <NUM>, and the other ends of the spherical shape of the pins <NUM> are in point contact with the side surface 32b of the flange 32a. For this reason, since the contact area between the pin <NUM> and the side surface 32b of the flange 32a is small, as compared with the first and second embodiments, the output of the signal for the bending moment and the translational force in the directions (Mx, My) other than the torque can be suppressed. Therefore, the interference of the other axis can be reduced and the detection accuracy of the torque can be improved.

<FIG> shows a modified example of <FIG>. Each of the plurality of pins <NUM> is allowed to come into and out of the first structure <NUM> of the torque sensor <NUM>, and is urged in a direction of protruding from the side surface of the first structure <NUM> by a coil spring <NUM> serving as an elastic member provided in the first structure <NUM>.

The structure shown in <FIG> can also be applied to the pin <NUM> represented by the broken line in <FIG>.

According to the modified example, the pin <NUM> is allowed to come into and out of the side surface of the first structure <NUM>, and is urged by the coil spring <NUM> in the direction of protruding from the side surface of the first structure <NUM>. For this reason, when the bending moment or the translational force in the directions (Mx, My) other than the torque is generated in the first arm <NUM>, transmission of the bending moment and the translational force to the torque sensor <NUM> can be relieved by the pin <NUM>. Therefore, output of the signals to the bending moment and the translational force in the direction (Mx, My) other than the torque can be further suppressed.

In the fourth embodiment, for example, a plurality of protrusions 32c are integrally provided on an inner side surface of the first arm <NUM>. Distal ends of the protrusions 32c are formed in a spherical shape. The distal ends of the protrusions 32c are made to be in point contact with the outer peripheral surface of the first structure <NUM> of the torque sensor <NUM>.

The number of the plurality of protrusions 32c is an even number, for example, four. Four protrusions 32c are arranged at regular intervals. More specifically, the protrusions are arranged on two straight lines inclined at, for example, <NUM> degrees to the line connecting the first strain sensor <NUM> and the second strain sensor <NUM>. However, the embodiment is not limited thereto. The protrusions may be arranged on a straight line connecting the first strain sensor <NUM> and the second strain sensor <NUM> and on a straight line orthogonal to this straight line.

The plurality of protrusions 32c are provided on the inner side surface of the first arm <NUM>. However, the embodiment is not limited thereto. As represented by a broken line in <FIG>, for example, a plurality of protrusions 41d may be provided on the outer peripheral surface of the first structure <NUM> of the torque sensor <NUM>, and distal ends of these protrusions 41d may be brought into point contact with the inner side surface of the first arm <NUM>.

In addition, the protrusions 32c and 41d may be formed in a semi-cylindrical shape, and the side surfaces of the semi-cylindrical protrusions 32c and 41d may be brought into line contact with the outer peripheral surface of the first structure <NUM> or the inner side surface of the first arm <NUM>.

According to the fourth embodiment, the plurality of protrusions 32c are provided on the inner side surface of the first arm <NUM>, the protrusions 32c are brought into contact with the outer peripheral surface of the first structure <NUM> of the torque sensor <NUM> or the plurality of protrusions 41d are provided on the outer peripheral surface of the first structure <NUM>, and the protrusions 41d are brought into contact with the inner side surface of the first arm <NUM>. Therefore, the interference of the other axis can be reduced and the detection accuracy of the torque can be improved, similarly to the first to third embodiments.

Moreover, the plurality of protrusions 32c are formed on the inner side surface of the first arm <NUM>, and a plurality of protrusions 41d are integrally formed on the outer peripheral surface of the first structure <NUM>. For this reason, the number of components can be reduced and the steps of assembly can be reduced.

<FIG> shows a modified example of <FIG>. In <FIG>, for example, a plurality of protrusions 32d are integrally provided on the inner side surface of the first arm <NUM>. The protrusions 32d are formed in an arcuate shape along the outer peripheral surface of the first structure <NUM> of the torque sensor <NUM>, and the side surfaces of the protrusions 32d are in surface contact with parts on the outer peripheral surface of the first structure <NUM> of the torque sensor <NUM>.

The number of the plurality of protrusions 32d is an even number, for example, four. For example, four protrusions 32d are arranged on a straight line connecting the first strain sensor <NUM> and the second strain sensor <NUM> (i.e., a position corresponding to the first strain sensor <NUM> and the second strain sensor <NUM>) and on a straight line orthogonal to this straight line. However, the protrusions can also be arranged at the same position as that shown in <FIG>.

The plurality of protrusions 32d are provided on the inner side surface of the first arm <NUM>. However, the embodiment is not limited thereto. For example, a plurality of protrusions 41e may be provided on the outer peripheral surface of the first structure <NUM> of the torque sensor <NUM>, and the protrusions 41e may be brought into surface contact with the inner side surface of the first arm <NUM>.

According to the modified example, too, the plurality of protrusions 32d in an arcuate shape provided on parts of the inner side surface of the first arm <NUM> are brought into surface contact with a part of the outer peripheral surface of the first structure <NUM> of the torque sensor <NUM>, and the plurality of protrusions 41e in an arcuate shape provided on parts of the outer peripheral surface of the first structure <NUM> are brought into surface contact with a part of the inner side surface of the first arm <NUM>. For this reason, output of the signals to the bending moment and the translational force in the directions (Mx, My) other than the torque of the torque sensor <NUM> can be prevented. Therefore, the interference of the other axis can be reduced and the detection accuracy of the torque can be improved.

The example of providing the plurality of protrusions on the outer peripheral surface of the first structure <NUM> of the torque sensor <NUM> has been described in the fourth embodiment.

As shown in <FIG>, the fifth embodiment is a modification of the fourth embodiment, and the outer shape of the first structure <NUM> of the torque sensor <NUM> is, for example, a polygon having four or more corners, for example, an octagon. Vertexes 41f of the polygon are brought into, for example, line contact with, for example, the inner side surface of the first arm <NUM>.

The fifth embodiment is not limited to the case where the outer shape of the first structure <NUM> of the torque sensor <NUM> is a polygon.

As shown in <FIG>, for example, the shape of the inner side surface of the first arm <NUM> can be formed as a polygon, and the outer peripheral surface of the first structure <NUM> of the torque sensor <NUM> having a disk-shaped outer shape can also be in, for example, line contact with each of the sides 32e of the polygon.

According to the fifth embodiment, the outer shape of the first structure <NUM> of the torque sensor <NUM> is formed as a polygon, the inner side surface of the first arm <NUM> is brought into contact with each of the vertexes 41f of the polygon, the inner side surface of the first arm <NUM> is formed as a polygon, and the first structure <NUM> of the disk-shaped torque sensor <NUM> is brought into contact with each of the sides 32e of the polygon. Therefore, the interference of the other axis can be reduced and the detection accuracy of the torque can be improved, similarly to the first to fourth embodiments.

<FIG> show a modified example of the fifth embodiment, illustrating a plurality of contact portions <NUM> between the first structure <NUM> of the torque sensor <NUM> and the first arm <NUM>, and a plurality of strain sensors <NUM>.

The number of contact portions between the first structure <NUM> of the torque sensor <NUM> and the first arm <NUM> is not limited to an even number, but may be an odd number.

The number of strain sensors is not limited to an even number but may be an odd number.

<FIG> shows a case where the number of contact portions between the first structure <NUM> of the torque sensor <NUM> and the first arm <NUM> is an even number, for example, four, and the number of the strain sensors is an odd number, for example, three.

<FIG> shows a case where the number of contact portions between the first structure <NUM> of the torque sensor <NUM> and the first arm <NUM> is an odd number, for example, five, and the number of the strain sensors is an odd number, for example, five.

The plurality of strain sensors <NUM> are arranged at regular intervals, and a plurality of contact portions <NUM> are also arranged at regular intervals.

As shown in <FIG>, one sensor portion <NUM> is arranged at a position corresponding to the contact portion <NUM>. Two or more portions where the sensor portion <NUM> is arranged at a position corresponding to the contact portion <NUM> may be provided.

As shown in <FIG>, one or more portions where the sensor portion <NUM> is arranged at a position corresponding to a middle part between two adjacent contact portions <NUM> may be provided.

Furthermore, one or more portions where the contact portion <NUM> is arranged at a position corresponding to the middle part of two adjacent sensor portions <NUM> may be provided.

Claim 1:
A mounting structure for a torque sensor comprising:
a torque sensor (<NUM>) comprising an annular first structure (<NUM>), an annular second structure (<NUM>) having a diameter smaller than a diameter of the annular first structure and arranged concentrically with the annular first structure (<NUM>), a plurality of third structures (<NUM>) connected between the annular first structure (<NUM>) and the annular second structure (<NUM>) and transmitting torque between the annular first structure and the annular second structure, and at least two sensor units (<NUM>, <NUM>) provided between the annular first structure (<NUM>) and the annular second structure (<NUM>); said structure being characterized by comprising:
a plurality of first contact portions (<NUM>, 32c, 41d, 32d, 41e, 41f, 32e) provided on one of the annular first structure (<NUM>) and a first attachment portion (<NUM>) fixed to the annular first structure (<NUM>), wherein the first attachment portion (<NUM>) is in a cylindrical shape, and an outer peripheral side surface of the annular first structure (<NUM>) is in contact with an vertical inner side surface of the first attachment portion (<NUM>) at the plurality of first contact portions (<NUM>, 32c, 41d, 32d, 41e, 41f, 32e) and except for the plurality of first contact portions (<NUM>, 32c, 41d, 32d, 41e, 41f, 32e) is not in contact with the vertical inner side surface of the first attachment portion (<NUM>), and
a plurality of second contact portions (<NUM>) provided on one of the annular second structure (<NUM>) and a second attachment portion (36b-<NUM>) fixed to the annular second structure (<NUM>), wherein the second attachment portion (36b-<NUM>) is a shaft, and the annular second structure (<NUM>) is in contact with an outer side surface of the second attachment portion (36b-<NUM>) at the plurality of second contact portions (<NUM>) and except for the plurality of second contact portions (<NUM>) is not in contact with the outer side surface of the second attachment portion (36b-<NUM>).