Torque sensor

Abstract

The torque sensor enables the first structure to be correctly mounted relative to the arm. The first structure (11) includes an annular first surface (11a), an annular second surface (11b) parallel to the first surface, a third surface (11c) connecting the outer periphery of the first and second surfaces, and a fourth surface (11d) connecting the inner periphery of the first and second surfaces. An annular second structure (12) is concentrically disposed inside the first structure. A plurality of third structures (13) connect the first and second structures. A plurality of strain sensors (14) are connected between the first and second structures. The first structure has a plurality of protrusions (11f) on a portion of the third surface. Each protrusion (11f) includes an inclined portion (11g) that increases in height from the first surface toward the second surface, and a linear contact portion (11h) extending from the apex of the inclined portion and parallel to the third surface.

Description

Technical Field

[0001] Embodiments of the present invention relate to torque sensors, for example, those used in robotic arms. Background Technology

[0002] The torque sensor, for example, has a first annular structure, a second annular structure concentrically arranged with the first structure, a plurality of third structures connecting the first and second structures, and a strain sensor disposed between the first and second structures. The first and second structures are mounted, for example, on the joints of a robotic arm, and the torque is detected based on the arm's movement (see, for example, Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2021-12024 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] The torque sensor has a first structure, for example, fixed to the inside of a cylindrical arm, and a second structure, for example, fixed to the output shaft of a motor mounted in a base. A portion of the outer surface of the first structure contacts the inner surface of the cylindrical arm. The contact area between the first structure and the inner surface of the arm is very small; therefore, when the axis of the first structure is installed at an angle relative to the axis of the arm, for example, the torque in the horizontal direction will be affected by the torque in the vertical direction, i.e., interference from other axes will occur, making it impossible to accurately detect the torque.

[0008] This embodiment provides a torque sensor that can be correctly mounted relative to the arm in the first structure.

[0009] Methods for solving problems

[0010] The torque sensor of this embodiment includes: a first structure comprising an annular first surface, an annular second surface parallel to the first surface, a third surface connecting the outer peripheries of the first and second surfaces, and a fourth surface connecting the inner peripheries of the first and second surfaces; an annular second structure concentrically disposed inside the first structure; a plurality of third structures connecting the first and second structures; and a plurality of strain sensors connected between the first and second structures. The first structure has a plurality of protrusions on a portion of the third surface, each protrusion including an inclined portion that increases in elevation from the first surface toward the second surface, and a linear contact portion continuous with the inclined portion and parallel to the third surface. Attached Figure Description

[0011] Figure 1 This is a plan view showing the torque sensor of this embodiment.

[0012] Figure 2 yes Figure 1 Side view.

[0013] Figure 3 It is Figure 2 A magnified stereoscopic view of part A.

[0014] Figure 4 The diagram showing the installation of the torque sensor of this embodiment onto the robotic arm is a three-dimensional view with a portion of it rendered as a cross-section.

[0015] Figure 5 It means Figure 4 A cross-sectional view of part B.

[0016] Figure 6 It means Figure 5 Cross-sectional view of the comparative example. Detailed Implementation

[0017] The embodiments will now be described with reference to the accompanying drawings. In the drawings, the same reference numerals are used to refer to the same parts or parts having the same function.

[0018] Figure 1 and Figure 2 This refers to the torque sensor of this embodiment. The torque sensor 10 includes a first structure 11, a second structure 12, a plurality of third structures 13, a plurality of strain sensors 14, etc.

[0019] The first structure 11 and the second structure 12 are formed in a ring shape, with the second structure 12 arranged concentrically inside the first structure 11. The first structure 11 and the second structure 12 are connected by a plurality of radially arranged third structures 13 acting as beams. The plurality of third structures 13 transmit torque between the first structure 11 and the second structure 12.

[0020] The first structure 11, the second structure 12, and the plurality of third structures 13 are made of metal, such as stainless steel, but materials other than metal may also be used if sufficient mechanical strength can be obtained for the applied torque.

[0021] The first structure 11 and the second structure 12, for example, have the same thickness, while the thickness of the plurality of third structures 13 is thinner than that of the first structure 11 and the second structure 12. The mechanical strength of the torque sensor 10 is set according to the thickness, width, and length of the third structures 13.

[0022] A plurality of strain sensors 14 are disposed between the first structure 11 and the second structure 12, outside of the plurality of third structures. The plurality of strain sensors 14 are arranged at equal intervals in positions symmetrical with respect to the center (center of torque application) of the first structure 11 and the second structure 12. Specifically, in Figure 1 In this configuration, eight strain sensors 14 are arranged, for example, at positions 45° apart. The number of strain sensors 14 is not limited to eight; for example, it can also be four, three, or two.

[0023] Each strain sensor 14 has a strain gauge 14a and multiple thin-film resistors (not shown) serving as strain gauges. The multiple thin-film resistors are disposed on the strain gauge 14a. The thickness of the strain gauge 14a is thinner than the thickness of the third structure 13. The multiple thin-film resistors form a bridging circuit.

[0024] One end of the strain gauge 14a is fixed to the first structure 11, and the other end of the strain gauge 14a is fixed to the second structure 12. The strain gauge 14a can be fixed by means of screw fastening, welding, or bonding with adhesive material. When using screw fastening, pressing components (not shown) are placed on both ends of the strain gauge 14a, and these pressing components are fixed to the first structure 11 and the second structure using screws, thereby fixing the strain gauge 14a to the first structure 11 and the second structure.

[0025] like Figure 2 As shown, the first structure 11 has an upper surface 11a as a first surface, a lower surface 11b parallel to the upper surface 11a as a second surface, an outer surface 11c connecting the upper surface 11a and the lower surface 11b as a third surface, and an inner surface 11d connecting the upper surface 11a and the lower surface 11b as a fourth surface. Figure 1 (As shown).

[0026] A step portion 11e is provided approximately at the center of the outer surface 11c in the thickness direction. Therefore, the diameter of the outer surface between the step portion 11e and the upper surface 11a of the first structure 11 is smaller than the diameter of the outer surface between the step portion 11e and the lower surface 11b.

[0027] A plurality of protrusions 11f are provided on the outer side surface between the stepped portion 11e and the upper surface 11a of the first structure 11. Each protrusion 11f is arranged, for example, at a position 90° apart. In this embodiment, the number of protrusions 11f is 4, but it is not limited to this, for example, there may be 3, 5, 6 or 8.

[0028] Figure 3Shows the specific structure of the protrusion 11f. The protrusion 11f has: an inclined portion 11g having a substantially triangular face, and a linear contact portion 11h. The inclined portion 11g slopes upward from the upper surface 11a of the first structure 11 toward the lower surface 11b. The height of the vertex of the inclined portion 11g coincides with the outer side surface between the step portion 11e and the lower surface 11b. The contact portion 11h extends from the vertex of the inclined portion 11g and extends downward toward the lower surface 11b to the step portion 11e. Therefore, the height of the contact portion 11h coincides with the outer side surface between the step portion 11e and the lower surface 11b.

[0029] When the thickness of the first structure is T1, the length T2 of the protrusion 11f is equal to the length from the upper surface 11a of the first structure to the step portion 11e. The length T2 is, for example, longer than 1 / 3 of the thickness T1 of the first structure 11 and is less than or equal to 1 / 2 of the thickness T1 (T1 / 3 < T2 ≤ T1 / 2). That is, the length T2 of the protrusion 11f is more than 1 / 3 and less than or equal to 1 / 2 of the thickness T1 of the first structure 11. In addition, the length of the contact portion 11h is, for example, more than 1 / 2 and less than or equal to 2 / 3 of the length of the protrusion 11f.

[0030] It should be noted that the step portion 11e is not necessary, and a plurality of protrusions 11f may be provided on the outer side surface 11c of the first structure 11.

[0031] Figure 4 Shows the case where the torque sensor of this embodiment is installed on a robotic arm. Figure 5 The Figure 4 portion B is shown enlarged.

[0032] Inside the cylindrical main body 20 of the robotic arm, an annular mounting member 21 is provided. The mounting member 21 has an annular fourth structure 21a and a cylindrical fifth structure 21b. The fourth structure 21a is parallel to the upper surface 11a of the first structure 11 of the torque sensor 10; the cylindrical fifth structure 21b is perpendicular to the fourth structure 21a and is parallel to the outer side surface 11c of the first structure 11. The diameter of the inner surface of the cylindrical fifth structure 21b is slightly larger than the diameter of the outer side surface between the plurality of protrusions 11f of the first structure and the lower surface 11b.

[0033] When the torque sensor 10 is installed on the mounting member 21, the torque sensor 10 is inserted into the cylindrical fifth structure 21b. At this time, the inclined portion 11g provided on the protrusion 11f of the torque sensor 10 is first inserted into the cylindrical fifth structure 21b, and then, the contact portion 11h of the protrusion 11f is inserted while contacting the inner surface of the fifth structure 21b. After that, when the torque sensor 10 is inserted into the cylindrical fifth structure 21b, as Figure 5As shown, the fourth structure 21a of the mounting component 21 contacts the upper surface 11a of the first structure 11. In this state, screws (not shown) are inserted into the plurality of holes 21c provided on the fifth structure 21b of the mounting component 21, and the plurality of screw holes 11i provided on the upper surface 11a of the first structure 11. Figure 1 (As shown) Tighten the screws respectively. In this way, the torque sensor 10 is installed on the mounting part 21.

[0034] It should be noted that a stepped portion 21c is provided on the inner surface of the fifth structure 21b, and a gap is provided between the inner surfaces of the first structure 11 and the fifth structure 21b, which makes it easier for the torque sensor 10 to be inserted into the fifth structure 21b.

[0035] (Effects of the implementation method)

[0036] According to the above embodiment, the torque sensor 10 has a plurality of protrusions 11f on its outer surface 11c, each protrusion 11f having an inclined portion 11g and a linear contact portion 11h. Therefore, when the torque sensor 10 is mounted to the robotic arm, the inclined portion 11g of each protrusion 11f plays a guiding role when inserted into the cylindrical fifth structure 21b, thus facilitating insertion.

[0037] Furthermore, the contact portion 11h of the protrusion 11f makes line contact with the cylindrical fifth structure 21b, thus preventing the axis of the first structure 11 of the torque sensor 10 from being tilted relative to the axis of the cylindrical fifth structure 21b. Therefore, the torque sensor 10 can be correctly mounted on the robotic arm 20, preventing interference from other axes and improving the accuracy of torque detection.

[0038] Furthermore, the length of the protrusion 11f is more than one-third and less than one-half of the thickness of the first structure 11, and the length of the contact portion 11h is more than one-half and less than two-thirds of the length of the protrusion 11f. Therefore, it can make sufficient contact with the cylindrical fifth structure 21b line. Thus, contact stability can be maintained.

[0039] Specifically, if like Figure 6 As shown in the comparative example, the protrusion 11f is shorter, so it cannot make sufficient line contact with the fifth structure 21b. Therefore, the axis of the first structure 11 will be installed at an angle relative to the axis of the cylindrical fifth structure 21b, resulting in other axial interference.

[0040] Furthermore, in this embodiment, a plurality of protrusions 11f are arranged at equal intervals around the first structure 11. Therefore, it is possible to prevent the torque sensor 10 from being installed at an angle relative to the cylindrical fifth structure 21b.

[0041] It should be noted that the configuration of the first structure 11, the second structure 12, the plurality of third structures 13, and the plurality of strain sensors 14 in the torque sensor of this embodiment is not limited to the configuration of the above embodiment and can be modified. Specifically, the shapes of the first structure 11 and the second structure 12 are not limited to ring shapes. For example, the first structure can be a quadrilateral frame, the second structure can be a roughly quadrilateral object disposed inside the first structure, the first structure and the second structure can be connected by the plurality of third structures, and the plurality of strain sensors 14 can be connected between the first structure and the second structure. The plurality of protrusions 11f can also be respectively disposed at the center of the four sides of the first structure.

[0042] Furthermore, this invention is not directly limited to the above-described embodiments. During implementation, the constituent elements can be modified and made more specific without departing from its essence. Additionally, various inventions can be formed by appropriately combining multiple constituent elements disclosed in the above-described embodiments. For example, several constituent elements can be deleted from all the constituent elements shown in the embodiments. Furthermore, constituent elements from different embodiments can be appropriately combined.

Claims

1. A torque sensor, comprising: A first structure includes an annular first surface, an annular second surface parallel to the first surface, a third surface connecting the outer periphery of the first surface and the second surface, and a fourth surface connecting the inner periphery of the first surface and the second surface. A ring-shaped second structure is concentrically arranged inside the first structure; Multiple third structures, which connect the first structure and the second structure; and, Multiple strain sensors are connected between the first structure and the second structure. The first structure has a plurality of protrusions on a portion of the third surface, the protrusions including an inclined portion that rises in the direction from the first surface toward the second surface, and a straight contact portion that extends from the apex of the inclined portion and is parallel to the third surface.

2. The torque sensor according to claim 1, wherein, The length of the plurality of protrusions is more than 1 / 3 and less than 1 / 2 of the thickness of the first structure.

3. The torque sensor according to claim 2, wherein, The length of the contact portion is more than 1 / 2 and less than 2 / 3 of the length of the protrusion.

4. The torque sensor according to claim 3, wherein, The plurality of protrusions are arranged at equal intervals around the first structure.

5. The torque sensor according to claim 4, wherein, The first structure has a stepped portion on the third surface. The diameter of the outer side of the first structure between the stepped portion and the first surface is smaller than the diameter of the outer side of the first structure between the stepped portion and the second surface. The plurality of protrusions are disposed on the outer side between the stepped portion and the first surface.

Images