JP7062540B2 - Torque sensor - Google Patents

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

A technique for reducing the influence of bending stress other than torque has been developed in a torque amount converter for measuring torque generated in an output unit of an automobile engine or the like (see, for example, Patent Document 4).

Japanese Unexamined Patent Publication No. 2013-096735 JP-A-2015-049209 Japanese Unexamined Patent Publication No. 2017-172983 Japanese Unexamined Patent Publication No. 2010-169586

For example, a disk-shaped torque sensor has a first structure and a second structure, and a third structure between the first structure and the second structure, and the first structure and the second structure. A strain generator as a strain sensor and a strain gauge are provided between the and.
When the first structure is fixed to the base of the robot arm, for example, and the second structure is fixed to the arm of the robot arm, for example, the torque sensor is used not only for torque but also for the transfer weight and load of the robot arm. The bending moment associated with the distance and the operating acceleration, and the load of the reaction force are applied.

When the torque sensor is attached to the robot arm, it is necessary to align the axis of the torque sensor with the axis of the robot arm, for example, the arm or the base.
When the shape of the first structure of the torque sensor is assumed to be a cylinder, the shape of the base of the robot arm is assumed to be a cylinder, and the cylinder is fitted inside the cylinder, the outer diameter of the cylinder and the inner diameter of the cylinder should be fitted. Therefore, the axes are aligned. However, in this case, although the axes are aligned, it is unclear exactly where the cylinder and the 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 randomly contact at several places.

In this way, when the first structure of the torque sensor and the base or arm of the robot arm come into contact at random in several places, 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 the output is output from the sensor.

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

An embodiment of the present invention provides a torque sensor capable of improving the detection accuracy of the torque sensor.

The torque sensor of the present embodiment includes a first structure, a second structure, a third structure provided between the first structure and the second structure, and the first structure. A torque sensor main body including at least two sensor portions provided between the second structure, a mounting portion fixed to the first structure and attached to a mounting location, and a torque sensor main body . Alternatively, an elastic means provided between the outer edge of the torque sensor main body and the mounting portion is provided so as to come into contact with one of the mounting portions without being fixed .

The block diagram which shows the torque sensor main body which concerns on 1st Embodiment. The perspective view which shows an example of the robot arm to which each embodiment is applied. A plan view of the torque sensor according to the first embodiment as viewed from above. A perspective view of the mounting portion according to the first embodiment as viewed from below. The simplified figure which showed the cross section which looked at the outer edge part of the torque sensor which concerns on 1st Embodiment from the side surface simply. A plan view of the mounting portion according to the second embodiment as viewed from below. The simplified figure which showed the cross section which looked at the outer edge part of the torque sensor which concerns on 2nd Embodiment from the side surface simply. A plan view of the torque sensor main body according to the third embodiment as viewed from above. The simplified figure which showed the cross section which looked at the torque sensor which concerns on 3rd Embodiment from the top simply. A plan view of the mounting portion according to the fourth embodiment as viewed from below. The simplified figure which showed the plane which looked at the torque sensor which concerns on 4th Embodiment from the bottom simply. FIG. 5 is a simplified diagram showing a simplified cross section of the outer edge portion of the torque sensor according to the fifth embodiment as viewed from the side surface.

Hereinafter, embodiments will be described with reference to the drawings. In the drawings, the same parts are designated by the same reference numerals.
First, the 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 an articulated robot, that is, a 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 as a drive source, a second drive unit 37, and a third drive unit. 38, a fourth drive unit 39 is provided. However, the configuration of the robot arm 30 is not limited to this, and is deformable.

The first arm 32 is made rotatable with respect to the base 31 by the first drive unit 36 provided in the first joint J1. The second arm 33 is made rotatable with respect to the first arm 32 by the second drive unit 37 provided in the second joint J2. The third arm 34 is made rotatable with respect to the second arm 33 by the third drive unit 38 provided in the third joint J3. The fourth arm 35 is rotatably provided with respect to the third arm 34 by the fourth drive unit 39 provided in the fourth joint J4. A hand 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, which will be described later.
(First Embodiment)
FIG. 1 is a configuration diagram showing 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 torque (Mz), and deformation is suppressed with respect to bending moments other than 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 rotation axis direction (Fz) of the torque measured by the torque sensor main body 40 is the vertical direction, the first arm 32 It will be mainly described as being connected so that the side is on the upper side and the base 31 is on the lower side.

However, the torque sensor main body 40 may be provided in the second joint J2 to the fourth joint J4, or may be provided in any direction in the rotation axis direction (Fz). Further, the direction of the torque sensor main body 40 may be provided so as to be upside down from the following description.
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 sensor portions, and the like. ..

The first structure 41 and the second structure 42 are formed in an annular 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 beam portions. Has been done. 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, 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, but if mechanically sufficient strength can be obtained with respect to the applied torque. , It is also possible to use materials other than metal. 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.

A first strain sensor 44 and a second strain sensor 45 are provided between the first structure 41 and the second structure 42. Specifically, one end of the strain generating body 44a constituting the first strain sensor 44 and the strain generating body 45a constituting the second strain sensor 45 are joined to the first structure 41, and the strain generating body 44a, The other end of 45a is joined to the second structure 42. The thickness of the strain-causing bodies 44a and 45a is thinner 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-causing bodies 44a and 45a, respectively. The sensor element provided on the strain-causing body 44a constitutes a first bridge circuit, and the sensor element provided on the strain-causing body 45a constitutes a second bridge circuit. 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 positions symmetrical 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 diameters of the annular first structure 41 and the second structure 42.

The first strain sensor 44 (distortion body 44a) is connected to the flexible substrate 46, and the second strain sensor 45 (distortion body 45a) is connected to the flexible substrate 47. The flexible boards 46 and 47 are connected to a printed circuit board (not shown) covered by a cover 48. An operational amplifier or the like that amplifies the output voltage of the two bridge circuits is arranged on the printed circuit board. Since the circuit configuration is not the essence of this embodiment, the description thereof will be 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 to this. For example, although the torque sensor main body 40 has been described as having a disk shape, it may have 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 main body 40 may have a configuration capable of obtaining three axis information of Mx, My, and Mz necessary for suppressing interference with other axes. Therefore, any torque sensor main body 40 may be used as long as information of three axes or less can be obtained.

The outer edge portion of the torque sensor main body 40 is provided along the outer periphery so that the elastic shape portion E1 is integrally formed. The elastic shape portion E1 has an elastic property by being deformed so that the groove-shaped portion is crushed.
FIG. 3 is a plan view of the torque sensor 20 according to the present embodiment as viewed from above.

In the torque sensor 20, the mounting portion 10 is fixed to the first structure 41 of the torque sensor main body 40 with bolts (screws) or the like.
FIG. 4 is a perspective view of the mounting portion 10 according to the present embodiment as viewed from below.
The mounting portion 10 is a component for mounting the torque sensor 20 at the mounting location. For example, the mounting portion 10 is connected to a part of the robot arm 30 such as the base 31 or the first arm 32 with a component for fixing such as a bolt. The mounting portion 10 does not have to be a component that is directly mounted at the mounting location, and may be a component (for example, a cover) that protects the torque sensor main body 40 for mounting at the mounting location. The mounting portion 10 is made of metal, for example, but may be made of a material other than metal as long as the strength can be secured.

The upper surface of the mounting portion 10 is a donut shape having a circular hole having a size similar to that of the second structure 42 of the torque sensor main body 40 in the center of a disk shape that is one size 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 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.

FIG. 5 is a simplified diagram showing a simplified cross section of the outer edge portion of the torque sensor 20 according to the present embodiment as viewed from the side surface.
When the mounting portion 10 is mounted on the torque sensor main body 40, the inner side surface of the mounting portion 10 comes into contact with the elastic shape portion E1 on the outer edge of the torque sensor main body 40. In this state, the mounting portion 10 and the torque sensor main body 40 are fixed.

Since the elastic shape portion E1 is provided on the outer edge of the torque sensor main body 40, the elastic shape portion E1 is located between the outer edge of the torque sensor main body 40 and the mounting portion 10. As a result, the groove-shaped portion of the elastic shape portion E1 is elastically deformed so as to be crushed, so that the external force applied to the torque sensor main body 40 in the radial direction with respect to the rotation of the torque (Mz) is reduced.
(Effect of the first embodiment)
According to the first embodiment, by providing the elastic shape portion E1 on the outer edge of the torque sensor main body 40, it is possible to reduce the external force in the radial direction applied to the torque sensor main body 40 and improve the detection accuracy of the torque sensor 20. can.
(Second Embodiment)
The torque sensor 20A according to the second embodiment is the torque sensor 20 according to the first embodiment in which the torque sensor main body 40 is replaced with the torque sensor main body 40A and the mounting portion 10 is replaced with the mounting portion 10A. Other points are the same as those of the first embodiment.

The torque sensor main body 40A is obtained by removing the elastic shape portion E1 from the torque sensor main body 40 according to the first embodiment.
FIG. 6 is a plan view of the mounting portion 10A according to the present embodiment as viewed from below.
The attachment portion 10A is provided with the elastic shape portion E2 having the same shape as the elastic shape portion E1 according to the first embodiment in the attachment portion 10 according to the first embodiment. The elastic shape portion E2 is provided along the inner circumference so as to be integrally formed on the inner side surface of the mounting portion 10A so as to be in contact with the outer edge of the torque sensor main body 40A.

FIG. 7 is a simplified diagram showing a simplified cross section of the outer edge portion of the torque sensor 20A according to the present embodiment as viewed from the side surface.
When the mounting portion 10A is mounted on the torque sensor main body 40A, the elastic shape portion E2 on the inner side surface of the mounting portion 10 comes into contact with the outer edge of the torque sensor main body 40A. In this state, the mounting portion 10A and the torque sensor main body 40A are fixed.

Since the elastic shape portion E2 is provided on the inner side surface of the mounting portion 10A, the elastic shape portion E2 is located between the outer edge of the torque sensor main body 40A and the mounting portion 10A. As a result, the groove-shaped portion of the elastic shape portion E2 is elastically deformed so as to be crushed, so that the external force applied to the torque sensor main body 40A in the radial direction with respect to the rotation of the torque (Mz) is reduced.
(Effect of the second embodiment)
According to the second embodiment, the same effect as that of the first embodiment can be obtained by providing the elastic shape portion E2 on the inner side surface of the mounting portion 10A.
(Third Embodiment)
The torque sensor 20B according to the third embodiment replaces the torque sensor main body 40 with the torque sensor main body 40B in the torque sensor 20 according to the first embodiment. Other points are the same as those of the first embodiment.

FIG. 8 is a plan view of the torque sensor main body 40B according to the present embodiment as viewed from above.
The torque sensor main body 40B is provided with four elastic shape portions E3 instead of the elastic shape portion E1 in the torque sensor main body 40 according to the first embodiment. The elastic shape portions E3 are provided on the outer edge of the torque sensor main body 40B at equal intervals in the circumferential direction. The elastic shape portion E3 is connected so that one end of the curved plate shape is integrally formed with the outer edge of the torque sensor main body 40B. The elastic shape portion E3 has an elastic property by being deformed like a leaf spring. Any number of elastic shape portions E3 may be provided as long as they are two or more. Further, both ends of the curved plate shape of the elastic shape portion E3 may be connected to the outer edge of the torque sensor main body 40B.

FIG. 9 is a simplified diagram showing a simplified cross section of the torque sensor 20B according to the present embodiment as viewed from above.
When the mounting portion 10 is mounted on the torque sensor main body 40B, the inner side surface of the mounting portion 10 comes into contact with the elastic shape portion E3 on the outer edge of the torque sensor main body 40. In this state, the mounting portion 10 and the torque sensor main body 40B are fixed.

Since the elastic shape portion E3 is provided on the outer edge of the torque sensor main body 40B, the elastic shape portion E3 is located between the outer edge of the torque sensor main body 40B and the mounting portion 10. As a result, the elastic shape portion E3 is elastically deformed like a leaf spring, so that the external force applied to the torque sensor main body 40B in the radial direction with respect to the rotation of the torque (Mz) is reduced.
(Effect of the third embodiment)
According to the third embodiment, by providing the elastic shape portion E3 on the outer edge of the torque sensor main body 40B, the same effect as that of the first embodiment can be obtained.
(Fourth Embodiment)
The torque sensor 20C according to the fourth embodiment replaces the mounting portion 10 with the mounting portion 10C in the torque sensor 20A according to the second embodiment. Other points are the same as those of the second embodiment.

FIG. 10 is a plan view of the mounting portion 10C according to the present embodiment as viewed from below.
The attachment portion 10C is provided with four elastic shape portions E4 having the same shape as the elastic shape portion E3 according to the third embodiment in place of the elastic shape portion E2 in the attachment portion 10A according to the second embodiment. be. The elastic shape portions E4 are provided at equal intervals along the inner circumference so as to be integrally formed on the inner side surface of the mounting portion 10C so as to be in contact with the outer edge of the torque sensor main body 40A. The number and shape of the elastic shape portions E4 are the same as those of the elastic shape portion E3 according to the third embodiment.

FIG. 11 is a simplified diagram showing a simple plane of the torque sensor 20C according to the present embodiment as viewed from below.
When the mounting portion 10C is mounted on the torque sensor main body 40A, the elastic shape portion E4 on the inner side surface of the mounting portion 10C comes into contact with the outer edge of the torque sensor main body 40A. In this state, the mounting portion 10C and the torque sensor main body 40A are fixed.

Since the elastic shape portion E4 is provided on the inner side surface of the mounting portion 10C, the elastic shape portion E4 is located between the outer edge of the torque sensor main body 40A and the mounting portion 10C. As a result, the elastic shape portion E4 is elastically deformed like a leaf spring, so that the external force applied to the torque sensor main body 40A in the radial direction with respect to the rotation of the torque (Mz) is reduced.
(Effect of Fourth Embodiment)
According to the fourth embodiment, the same effect as that of the first embodiment can be obtained by providing the elastic shape portion E4 on the inner side surface of the mounting portion 10C.
(Fifth Embodiment)
In the torque sensor 20D according to the fifth embodiment, in the torque sensor 20 according to the first embodiment, the torque sensor main body 40 is replaced with the torque sensor main body 40A according to the second embodiment, and an elastic member E5 is added. Other points are the same as those of the first embodiment.

FIG. 12 is a simplified diagram showing a simplified cross section of the outer edge portion of the torque sensor 20D according to the present embodiment as viewed from the side surface.
The elastic member E5 is provided so as to be in contact with the inner side surface of the mounting portion 10 and the outer edge of the torque sensor main body 40A in a state where the mounting portion 10 is mounted on the torque sensor main body 40A. The elastic member E5 may be made of any material as long as it is elastically deformable. The elastic member E5 is, for example, a resin. The elastic member E5 may be an independent component, may be adhered to the inside of the mounting portion 10 or one or both of the outer edges of the torque sensor main body 40A, or may be provided so as to be integrally formed with one of them. .. In this state, the mounting portion 10 and the torque sensor main body 40A are fixed.

The elastic member E5 is provided so as to be located between the inner side surface of the mounting portion 10 and the outer edge of the torque sensor main body 40A. As a result, the elastic shape portion E5 is elastically deformed so as to be crushed, so that the external force applied to the torque sensor main body 40A in the radial direction with respect to the rotation of the torque (Mz) is reduced.
(Effect of the fifth embodiment)
According to the fifth embodiment, the same effect as that of the first embodiment can be obtained by providing the elastic shape portion E5 between the inner side surface of the mounting portion 10 and the outer edge of the torque sensor main body 40A. ..

In addition, the present invention is not limited to each of the above embodiments as it is, and at the implementation stage, the components can be modified and embodied within a range that does not deviate from the gist thereof. In addition, various inventions can be formed by an appropriate combination of the plurality of components disclosed in each of the above embodiments. For example, some components may be removed from all the components shown in the embodiments. In addition, components across different embodiments may be combined as appropriate.

40 ... Torque sensor body, 41 ... First structure, 42 ... Second structure, 43 ... Third structure, 44 ... First strain sensor, 44a ... Distortion body, 45 ... Second strain sensor, 45a ... Distorted body, 46 ... Flexible substrate, 47 ... Flexible substrate, 48 ... Cover, E1 ... Elastic shape part.

Claims (6)

Between the first structure, the second structure, the third structure provided between the first structure and the second structure, and between the first structure and the second structure. A torque sensor body comprising at least two sensor units provided in the
A mounting portion fixed to the first structure and mounted at the mounting location,
It is characterized by comprising an elastic means provided between the outer edge of the torque sensor main body and the mounting portion so as to come into contact with the torque sensor main body or the mounting portion without being fixed . Torque sensor. The torque sensor according to claim 1, wherein the elastic means has a shape including a groove-shaped portion. The torque sensor according to claim 1, wherein the elastic means has a shape that elastically deforms like a leaf spring. The torque sensor according to claim 1, wherein the elastic means is made of a material that elastically deforms. The torque sensor according to any one of claims 1 to 4, wherein the elastic means is provided so as to be integrally formed with the torque sensor main body. The torque sensor according to any one of claims 1 to 4, wherein the elastic means is provided so as to be integrally formed with the mounting portion.

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