JP2020012659A - Torque sensor - Google Patents

Abstract

To provide a torque sensor which can increase the accuracy of detection.SOLUTION: The torque sensor includes: a torque sensor body 40 having a first structure 41, a second structure 42, a third structure 43 between the first structure 41 and the second structure 42, and at least two sensor parts 44 and 45 between the first structure 41 and the second structure 42; and an attachment unit fixed to the first structure 41, the attachment unit to be attached to an equipment part, at least one of the torque sensor body 40 and the attachment unit being a first tapered surface T1 inclined in the rotational-axis direction of the torque to be measured and being in contact with the other.SELECTED DRAWING: Figure 1

Description

  An embodiment of the present invention relates to a torque sensor applied to, for example, a robot arm or the like.

  The torque sensor has a first structure to which a torque is applied, a second structure to which the torque is output, and a plurality of strain generating portions as beams connecting the first structure and the second structure. In addition, a plurality of strain gauges as sensor elements are arranged in these strain generating portions. A bridge circuit is configured by these strain gauges (see, for example, Patent Documents 1, 2, and 3).

  2. Description of the Related Art In a torque converter for measuring a torque generated in an output section of an automobile engine or the like, a technique for reducing the influence of bending stress other than torque has been developed (for example, see Patent Document 4).

JP 2013-097735 A JP-A-2005-049209 JP 2017-172983 A JP 2010-169586 A

For example, a disc-shaped torque sensor has a first structure, a second structure, and a third structure between the first structure and the second structure, and the first structure and the second structure. And a strain-generating body as a strain sensor and a strain gauge.
When the first structure is fixed to, for example, a base of a robot arm, and the second structure is fixed to, for example, an arm of a robot arm, when the torque sensor is used, in addition to the torque, the transfer weight and load of the robot arm are also measured. And the bending moment accompanying the operation acceleration and the reaction force load are applied.

When attaching the torque sensor to the robot arm, it is necessary to align the axis of the torque sensor with, for example, the axis of the arm or the base of the robot arm.
Assuming that the shape of the first structure of the torque sensor is, for example, a cylinder, the shape of the base of the robot arm is a cylinder, and when fitting the cylinder into the cylinder, fitting the outer diameter of the cylinder to the inner diameter of the cylinder , The axes are matched. However, in this case, although the axes coincide, it is unclear exactly where the cylinder and cylinder are in contact. That is, since the outer diameter of the cylinder and the inner diameter of the cylinder are not perfect circles, it is expected that the outer surface of the cylinder and the inner surface of the cylinder will come into contact at several places at random.

  As described above, when the first structure of the torque sensor and the base or arm of the robot arm come into contact at several places at random, when a bending moment other than torque or a translational force is applied to the torque sensor, the first The structure and the second structure are deformed asymmetrically, and the strain sensor is deformed asymmetrically with the deformation, and an output is output from the sensor.

  When a bending moment or a load (X-axis direction Fx, Y-axis direction Fy, Z-axis direction Fz) other than torque is applied to the torque sensor, that is, a translational force is applied, a plurality of strain sensors provided in the torque sensor respond to displacement. Distortion occurs. Usually, the bridge circuit of the torque sensor is configured to output a voltage with respect to a force in the torque direction and not to output a voltage with respect to a force in a direction other than the torque. However, when the first structure or the second structure is asymmetrically deformed, asymmetric distortion is generated in a plurality of distortion sensors provided in the torque sensor. Due to this other-axis interference, a sensor output is generated, and the detection accuracy of the torque sensor is reduced.

  Embodiments of the present invention provide a torque sensor capable of improving detection accuracy of the torque sensor.

  The torque sensor according to the present embodiment includes a first structure, a second structure, a third structure provided between the first structure and the second structure, and a first structure. A torque sensor main body including at least two sensor units provided between the second structure and a mounting unit fixed to the first structure and mounted to a mounting location; At least one of the torque sensor main body and the mounting portion is in contact with the other at a first tapered surface inclined in the rotation axis direction of the torque to be measured.

FIG. 2 is a configuration diagram illustrating a torque sensor main body according to the first embodiment. FIG. 2 is a perspective view showing an example of a robot arm to which each embodiment is applied. FIG. 2 is a plan view of the torque sensor according to the first embodiment as viewed from above. The perspective view which looked at the attachment part concerning a 1st embodiment from the lower part. FIG. 2 is a simplified diagram simply showing a cross section of the torque sensor according to the first embodiment as viewed from a side. The top view which looked at the torque sensor concerning a 2nd embodiment from the upper part. The top view which looked at the torque sensor concerning a 2nd embodiment from the bottom. The perspective view which looked at the 1st attachment part concerning a 2nd embodiment from the upper part. The perspective view which looked at the 2nd attachment part concerning a 2nd embodiment from the upper part. The sectional view which looked at the 2nd attachment part concerning a 2nd embodiment from the side. FIG. 6 is a simplified diagram simply showing a cross section of a torque sensor according to a second embodiment viewed from a side. The top view which looked at the torque sensor concerning a 3rd embodiment from the bottom. The perspective view which looked at the 2nd attachment part concerning a 3rd embodiment from the upper part. FIG. 9 is a simplified diagram simply showing a cross section of a torque sensor according to a third embodiment viewed from a side. FIG. 9 is a simplified diagram simply showing a cross section of a torque sensor according to a fourth embodiment viewed from a side.

Hereinafter, embodiments will be described with reference to the drawings. In the drawings, the same parts are denoted by the same reference numerals.
First, a robot arm 30 to which each embodiment of the present invention is applied will be described with reference to FIG.
FIG. 2 shows an example of the articulated robot, that is, the robot arm 30. The robot arm 30 includes, for example, a base 31, a first arm 32, a second arm 33, a third arm 34, a fourth arm 35, a first drive unit 36, a second drive unit 37 as a drive source, and a third drive unit. 38, and a fourth drive section 39. However, the configuration of the robot arm 30 is not limited to this, and can be modified.

The first arm 32 is rotatable with respect to the base 31 by a first driving unit 36 provided at the first joint J1. The second arm 33 is rotatable with respect to the first arm 32 by a second driving unit 37 provided at the second joint J2. The third arm 34 is rotatable with respect to the second arm 33 by a third drive unit 38 provided at the third joint J3. The fourth arm 35 is rotatably provided with respect to the third arm 34 by a fourth drive unit 39 provided at the fourth joint J4. Hands and various tools (not shown) are attached to the fourth arm 35.
The first drive unit 36 to the fourth drive unit 39 include, for example, a motor, a speed reducer, and a torque sensor described below.

(1st Embodiment)
FIG. 1 is a configuration diagram illustrating a torque sensor main body 40 according to the first embodiment.
In the present embodiment, the torque sensor main body 40 is deformed with respect to the torque (Mz), and the deformation is suppressed with respect to a bending moment other than the torque (Mx, My).

  Here, assuming that the torque sensor main body 40 is mounted on the first joint J1 of the robot arm 30 shown in FIG. 2 and the rotational axis direction (Fz) of the torque measured by the torque sensor main body 40 is the vertical direction, the first arm 32 The description will be made mainly on the assumption that the base 31 is connected to the upper side and the base 31 is connected to the lower side.

However, the torque sensor main body 40 may be provided at the second joint J2 to the fourth joint J4, or may be provided so that the rotation axis direction (Fz) is in any direction. Further, the direction of the torque sensor main body 40 may be provided such that the upper and lower directions are opposite to those described below.
The torque sensor main body 40 includes a first structure 41, a second structure 42, a plurality of third structures 43, a first strain sensor 44 and a second strain sensor 45 as a sensor unit, and the like. .

  The first structure 41 and the second structure 42 are formed in a ring shape, and the diameter of the second structure 42 is smaller than the diameter of the first structure 41. The second structure 42 is arranged concentrically with the first structure 41, and the first structure 41 and the second structure 42 are connected by a third structure 43 as a plurality of radially arranged beams. Have been. The plurality of third structures 43 transmit torque between the first structure 41 and the second structure 42. The second structure 42 has a hollow portion 42a, and, for example, a wiring (not shown) is passed through the hollow portion 42a.

  The first structure 41, the second structure 42, and the plurality of third structures 43 are made of metal, for example, stainless steel. It is also possible to use materials other than metals. The first structure 41, the second structure 42, and the plurality of third structures 43 have, for example, the same thickness. The mechanical strength of the torque sensor main body 40 is set by the thickness, width, and length of the third structure 43.

  Between the first structure 41 and the second structure 42, a first strain sensor 44 and a second strain sensor 45 are provided. Specifically, one end of a strain body 44a forming the first strain sensor 44 and one end of a strain body 45a forming the second strain sensor 45 are joined to the first structure 41, and the strain bodies 44a, The other end of 45a is joined to the second structure 42. The thickness of the strain body 44a, 45a is smaller than the thickness of the first structure 41, the second structure 42, and the plurality of third structures 43.

  A plurality of strain gauges (not shown) as sensor elements are provided on the surfaces of the strain bodies 44a and 45a, respectively. A first bridge circuit is configured by the sensor element provided on the strain body 44a, and a second bridge circuit is configured by the sensor element provided on the strain body 45a. That is, the torque sensor main body 40 includes two bridge circuits.

  Further, the first strain sensor 44 and the second strain sensor 45 are arranged at symmetrical positions with respect to the center of the first structure 41 and the second structure 42 (the center of action of torque). In other words, the first strain sensor 44 and the second strain sensor 45 are arranged on the diameter of the first and second annular structures 41 and 42.

  The first strain sensor 44 (strain body 44a) is connected to the flexible board 46, and the second strain sensor 45 (strain body 45a) is connected to the flexible board 47. The flexible boards 46 and 47 are connected to a printed board (not shown) covered by a cover 48. An operational amplifier for amplifying the output voltages of the two bridge circuits is disposed on the printed circuit board. The circuit configuration is not the essence of the present embodiment, and the description is omitted.

  Here, the configuration of the torque sensor main body 40 described above is shown as an example of the torque sensor main body applied to the present embodiment, and is not limited thereto. For example, the torque sensor body 40 has been described as a disk-shaped one, but may be any shape such as a polygonal shape. Further, the case where the torque sensor main body 40 has two sensor units of the first strain sensor 44 and the second strain sensor 45 has been described. However, the present invention is not limited to this, and the torque sensor body 40 may have any configuration as long as it can obtain three axis information of Mx, My, and Mz, which are necessary to suppress interference between other axes. Therefore, any torque sensor main body 40 may be used as long as information of three or more axes can be obtained.

The upper edge portion of the torque sensor main body 40 is provided with a tapered surface T1 as if chamfered. The tapered surface T1 has a shape inclined in the rotation axis direction (Fz).
FIG. 3 is a plan view of the torque sensor 20 according to the present embodiment as viewed from above. FIG. 4 is a perspective view of the mounting portion 10 according to the present embodiment as viewed from below.

In the torque sensor 20, the mounting portion 10 is fixed to a first structure 41 of a torque sensor main body 40 with a plurality of bolts (screw) 21.
The mounting section 10 is a component for mounting the torque sensor 20 to a mounting location. For example, the mounting unit 10 is connected to a part of the robot arm 30 such as the base 31 or the first arm 32 by a component such as a bolt for fixing. Note that the mounting portion 10 may not be a component directly attached to the mounting location, but may be a component (for example, a cover) that protects the torque sensor main body 40 to be mounted on the mounting location. The attachment portion 10 is, for example, a metal, but may be a material other than a metal as long as the strength can be secured.

  The upper surface of the mounting portion 10 has a donut shape having a circular hole approximately the same size as the second structure 42 of the torque sensor main body 40 in the center of a disk shape slightly larger than the torque sensor main body 40. The diameter of the inner circumference of the mounting portion 10 is substantially the same as the outer diameter of the torque sensor main body 40. The mounting portion 10 is provided with screw holes H1 for passing a plurality of bolts 21 at equal intervals in the circumferential direction. The inside (lower side) of the mounting portion 10 has a shape in which the thickness of the outer peripheral portion is larger than that of the inner peripheral portion so as to cover the upper portion of the torque sensor main body 40. The step due to the difference in thickness between the inner peripheral portion and the outer peripheral portion is formed on the tapered surface T2. The tapered surface T2 is formed to have the same inclination as the tapered surface T1 so that the surfaces of the tapered surface T2 and the tapered surface T1 of the torque sensor main body 40 are fitted together.

FIG. 5 is a simplified diagram simply showing a cross section of the torque sensor 20 according to the present embodiment viewed from the side.
When the mounting portion 10 is mounted on the torque sensor main body 40, the tapered surface T2 of the mounting portion 10 comes into contact with the tapered surface T1 at the outer edge portion of the upper portion of the torque sensor main body 40. The tapered surface T2 and the tapered surface T1 are formed so as to have the same inclination, respectively, and come into contact with each other so as to meet each other. In this state, the mounting portion 10 and the torque sensor main body 40 are fixed by the bolt 21.

Due to the provision of the tapered surface T1, the torque sensor main body 40 is formed so as to become thinner as going upward. Further, the inner shape of the mounting portion 10 is formed so as to become narrower upward as the tapered surface T2 is provided.
(Effect of First Embodiment)
According to the first embodiment, each of the torque sensor main body 40 and the mounting portion 10 is provided with the tapered surfaces T1 and T2 inclined in the rotation axis direction (Fz), and is fixed so that the tapered surfaces T1 and T2 fit together. Thus, the external force applied to the torque sensor main body 40 in the rotation axis direction (Fz) can be reduced, and the detection accuracy of the torque sensor 20 can be improved.

Specifically, an effect can be expected in which external force applied in the Mx or My direction is released along the tapered surfaces T1 and T2.
For example, when there is no tapered surface and the side surface of the torque sensor main body 40 and the inner side surface of the mounting portion 10 are in contact with each other, when a force is applied in the Mx or My direction, the angle formed by the upper surface and the side surface of the torque sensor main body 40 It is assumed that the attachment portion 10 is deformed. When such deformation occurs, asymmetric displacements (strains) are generated in the strain generating bodies 44a, 45a of the strain sensors 44, 45. Therefore, such deformation can be avoided by providing the tapered surfaces T1 and T2 on the torque sensor body 40 and the mounting portion 10, respectively.

(2nd Embodiment)
FIG. 6 is a plan view of the torque sensor 20A according to the second embodiment as viewed from above. FIG. 7 is a plan view of the torque sensor 20A according to the present embodiment as viewed from below.
The torque sensor 20A is different from the torque sensor 20 according to the first embodiment in that the torque sensor main body 40 is replaced with the torque sensor main body 40A, the mounting portion 10 is replaced with the first mounting portion 11 and the second mounting portion 12, and a plurality of bolts 22 are provided. Is added. The plurality of bolts 21, 22 are held so that the torque sensor 20 </ b> A is held in a state where the torque sensor body 40 </ b> A is housed so as to be sandwiched by the first mounting part 11 on the upper side and the second mounting part 12 on the lower side. It is fixed by. The other points are the same as in the first embodiment.

  The torque sensor main body 40A is different from the torque sensor main body 40 according to the first embodiment in that the lower outer edge portion has the same rotation axis direction (Fz) as the tapered surface T1 instead of the upper outer edge portion. The tapered surface T1A having an inclined shape is provided. Other points are the same as those of the torque sensor main body 40 according to the first embodiment.

The plurality of bolts 21 are components that fix the first mounting portion 11 to the first structure 41 of the torque sensor main body 40A, as in the first embodiment. The plurality of bolts 22 are components for connecting and fixing the first mounting portion 11 and the second mounting portion 12.
FIG. 8 is a perspective view of the first mounting portion 11 according to the present embodiment as viewed from above. FIG. 9 is a perspective view of the second mounting portion 12 according to the present embodiment as viewed from above. FIG. 10 is a cross-sectional view of the second mounting portion 12 according to the present embodiment as viewed from the side.

The first attachment portion 11 and the second attachment portion 12 are components for attaching the torque sensor 20A to a mounting location, similarly to the attachment portion 10 according to the first embodiment.
The first mounting portion 11 has a ring shape slightly larger than the torque sensor main body 40A, and the upper and lower surfaces are flat. The first mounting portion 11 is provided with a plurality of screw holes H1A for passing the bolts 21 and a plurality of screw holes H2 for passing the bolts 22.

  The second mounting portion 12 has a ring shape having the same outer diameter as the first mounting portion 11. In the center of the second mounting portion 12, a hole having a shape into which the torque sensor main body 40A is fitted is provided. A tapered surface T2A having a shape inclined in the rotation axis direction (Fz) similar to the tapered surface T2 of the mounting portion 10 according to the first embodiment is formed at an outer edge portion below the hole. The tapered surface T2A is formed so as to have the same inclination as the tapered surface T1A so that the surfaces of the tapered surface T2A and the tapered surface T1A of the torque sensor main body 40A are fitted to each other. The second mounting portion 12 is provided with a plurality of screw holes H3 through which the bolts 22 pass.

FIG. 11 is a simplified diagram simply showing a cross section of the torque sensor 20A according to the present embodiment viewed from the side.
The tapered surface T2A of the second mounting portion 12 is formed to have the same inclination as the tapered surface T1A of the torque sensor main body 40A. As a result, similarly to the first embodiment, the tapered surface T2A comes into contact with the tapered surface T1A so that the surfaces are brought into contact with each other. In this state, it is fixed by the bolts 21 and 22.

The torque sensor main body 40A is formed so that the taper surface T1A is provided, so that the torque sensor body 40A becomes thinner downward. Further, the inner shape of the attachment portion 12 is formed so as to become narrower downward as the tapered surface T2A is provided.
With such a configuration, as in the first embodiment, the external force applied to the torque sensor main body 40A in the rotation axis direction (Fz) is released, and thus, the torque is reduced.
(Effect of Second Embodiment)
According to the second embodiment, each of the torque sensor main body 40A and the second mounting portion 12 is provided with the tapered surfaces T1A and T2A inclined in the rotation axis direction (Fz) so that the tapered surfaces T1 and T2 fit together. By fixing, similarly to the first embodiment, the external force applied to the torque sensor main body 40A in the rotation axis direction (Fz) can be reduced, and the detection accuracy of the torque sensor 20A can be improved.

(Third embodiment)
FIG. 12 is a plan view of the torque sensor 20B according to the third embodiment as viewed from below.
The torque sensor 20B is obtained by replacing the second mounting portion 12 with four second mounting portions 12B in the torque sensor 20A according to the second embodiment. The number of the second mounting portions 12B is not limited as long as the holding of the torque sensor main body 40A can be ensured, but is preferably three or more. The other points are the same as in the first embodiment.

FIG. 13 is a perspective view of the second mounting portion 12B according to the present embodiment as viewed from above.
The second attachment portion 12B has a shape in which a cylindrical upper portion and a conical lower portion are combined. The second mounting portion 12B is provided with a screw hole vertically penetrating at the center of the circular shape when viewed from above. This screw hole is formed so as to match the screw thread of the bolt 22. Thereby, the second mounting portion 12B has a function like a nut corresponding to the bolt 22.

The side surface of the conical portion of the second mounting portion 12B is formed as a tapered surface T2B having the same inclination as the tapered surface T1A.
FIG. 14 is a simplified diagram simply showing a cross section of the torque sensor 20B according to the present embodiment viewed from the side.
The tapered surface T2B of the second mounting portion 12B is formed to have the same inclination as the tapered surface T1A of the torque sensor main body 40A. The bolt 22 is inserted into the screw hole H2 of the first mounting portion 11, and the second mounting portion 12B is fitted from the side opposite to the head of the bolt 22, so that the tapered surface T2B of the second mounting portion 12B becomes a torque sensor body 40A. In line with the tapered surface T1A. In this state, it is fixed by the bolts 21 and 22.

  The torque sensor main body 40A is formed so that the taper surface T1A is provided, so that the torque sensor body 40A becomes thinner downward. Further, the inner shape surrounded by the four contact portions between the torque sensor main body 40A and the four mounting portions 12B is formed so as to become narrower downward as the tapered surface T2B is provided. .

With such a configuration, as in the second embodiment, the external force applied to the torque sensor main body 40A in the rotation axis direction (Fz) is released, thereby reducing the torque.
(Effect of Third Embodiment)
According to the third embodiment, by using the second mounting portion 12B provided with the tapered surface T2B, it is possible to obtain the same operation and effect as the second embodiment.

  In addition, since the four second mounting portions 12B can be manufactured at lower raw material costs and processing costs than the second mounting portions 12 according to the second embodiment, the manufacturing of the torque sensor 20B is more efficient than in the second embodiment. Cost can be reduced.

(Fourth embodiment)
FIG. 15 is a simplified diagram simply showing a cross section of a torque sensor 20C according to the fourth embodiment viewed from the side.
The torque sensor 20C has a configuration in which the torque sensor main body 40A is replaced with a torque sensor main body 40C in the torque sensor 20B according to the third embodiment. The torque sensor main body 40C is obtained by replacing the tapered surface T1A with a curved surface C1 in the torque sensor main body 40A according to the second embodiment. The other points are the same as in the third embodiment.

The curved surface C1 of the torque sensor main body 40C contacts the tapered surface T2B of the second mounting portion 12B at a point along the outer periphery of the curved surface C1.
(Effect of Fourth Embodiment)
According to the fourth embodiment, since the tapered surface T2B is provided in the second mounting portion 12B, similarly to the third embodiment, an external force applied to the torque sensor main body 40C in the rotation axis direction (Fz). Can be reduced.

Further, by forming the contact portion of the torque sensor main body 40C with the second mounting portion 12 as a curved surface C1, a tapered surface T1A is formed to match the tapered surface T2B of the second mounting portion 12B as in the third embodiment. Processing can be made easier.
Although the fourth embodiment is configured based on the third embodiment, it may be configured based on the first embodiment or the second embodiment. Specifically, the tapered surfaces T1 and T1A of the torque sensor main bodies 40 and 40A may be curved surfaces C1 as in the fourth embodiment. In the fourth embodiment, the torque sensor body 40C has the curved surface C1, but instead, the tapered surface T2B of the second mounting portion 12B may be a curved surface. Similarly, it may be configured based on the first embodiment or the second embodiment, and the tapered surfaces T2, T2A of the mounting portions 10, 12 may be curved surfaces. Also in these embodiments, the same operation and effect as in the fourth embodiment can be obtained.

  In addition, the present invention is not limited to the above embodiments as they are, and can be embodied by modifying the constituent elements in an implementation stage without departing from the scope of the invention. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Further, components of different embodiments may be appropriately combined.

  40: Torque sensor main body, 41: first structure, 42: second structure, 43: third structure, 44: first strain sensor, 44a: strain generator, 45: second strain sensor, 45a: strain Distorted body, 46: flexible substrate, 47: flexible substrate, 48: cover, T1: tapered surface.

Claims (8)

A first structure, a second structure, a third structure provided between the first structure and the second structure, and a third structure provided between the first structure and the second structure. A torque sensor main body comprising at least two sensor units provided in
A mounting portion fixed to the first structure, for mounting at a mounting location,
A torque sensor, wherein at least one of the torque sensor main body and the mounting portion is a first tapered surface inclined in a rotation axis direction of a torque to be measured, and is in contact with the other. The torque sensor according to claim 1, wherein the attachment portion has a shape that covers an outer circumference of the torque sensor main body with the first tapered surface. The attachment portion is configured such that a first attachment portion and a second attachment portion are connected,
The first mounting portion is fixed to the first structure,
The torque sensor according to claim 1, wherein the second mounting portion has a shape that covers an outer periphery of the torque sensor main body with the first tapered surface. The attachment portion is configured such that a first attachment portion and a second attachment portion are connected by a fixed component,
The first mounting portion is fixed to the first structure,
2. The torque sensor according to claim 1, wherein the second mounting portion is connected to the fixed component, and has a shape that contacts the outer periphery of the torque sensor main body at the first tapered surface. 3. The torque sensor according to any one of claims 2 to 4, wherein the torque sensor main body has a shape including a second tapered surface that is in contact with the first tapered surface at the same inclination. . The torque sensor according to any one of claims 2 to 4, wherein the torque sensor body has a shape including a curved surface that contacts the first tapered surface. The torque sensor according to claim 1, wherein the torque sensor body has a shape including the first tapered surface. The torque sensor according to claim 7, wherein the attachment portion has a shape including a curved surface that contacts the first tapered surface.

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