Torque sensor

Abstract

To provide a highly rigid, thin and lightweight torque sensor.SOLUTION: A plurality of third structures 13 connect a first structure 11 and a second structure 12. At least two recesses 15 are provided corresponding to at least two of the plurality of third structures, and are provided continuously on surfaces of the first structure, the third structure, and the second structure. At least two fourth structures 14 are disposed within each of the at least two recesses with first ends fixed to the first structure and second ends fixed to the second structure. Strain sensors 16 are disposed within each of the at least two fourth structures.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the invention relates to a torque sensor for application in, for example, a joint of a robot arm. [Background technology]

[0002] If the joints of a robot arm (hereinafter simply referred to as the arm) have low rigidity, the position of the tip of the arm is difficult to determine due to inertia when the arm is operated. For this reason, the joints of the arm need to have high rigidity.

[0003] Furthermore, in order to improve the torque detection accuracy of the torque sensor disposed at the joint of the arm, it is necessary for the torque sensor to have high rigidity in the torque direction and in the moment direction other than the torque.

[0004] In general, for example, in the case of a torque sensor having a configuration in which multiple beams are arranged between two annular elastic bodies having the same diameter, the rigidity in the torque direction and moment direction can be increased by optimizing the length and number of the multiple beams. In this case, the weight can be reduced by increasing the opening area of ​​the two annular elastic bodies. However, since multiple beams are arranged in the axial direction between the two elastic bodies, the thickness of the torque sensor increases, making it difficult to reduce the thickness of the torque sensor (see, for example, Patent Document 1).

[0005] On the other hand, in the case of a torque sensor having two annular elastic bodies with different diameters arranged concentrically and a plurality of beams arranged radially between these elastic bodies, it is possible to make the axial thickness of the beams equal to or smaller than the thickness of the two elastic bodies. This makes it possible to realize a thin torque sensor capable of highly accurate detection. However, in this case, in order to obtain the necessary rigidity, it is necessary to make the two elastic bodies sufficiently thick, which increases the weight of the torque sensor (see Patent Document 2).

[0006] Increasing the rigidity of the torque sensor in this way increases the thickness and weight of the torque sensor, resulting in a larger size. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2010-169586 A [Patent Document 2] Patent Publication No. 2021-060349 Summary of the Invention [Problem to be solved by the invention]

[0008] Embodiments of the present invention provide a torque sensor that is stiff, thin, and lightweight. [Means for solving the problem]

[0009] The torque sensor of this embodiment includes a ring-shaped first structure, a ring-shaped second structure arranged concentrically with the first structure, a plurality of third structures arranged between the first structure and the second structure and connecting the first structure and the second structure, at least two recesses corresponding to at least two of the plurality of third structures and continuously provided on the surfaces of the first structure, the third structure and the second structure, at least two fourth structures arranged inside the at least two recesses, respectively, and having a first end fixed to the first structure and a second end fixed to the second structure, and a strain sensor arranged inside each of the at least two fourth structures. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a plan view showing a torque sensor according to a first embodiment. [Diagram 2] FIG. 2 is a plan view showing an elastic body of the torque sensor shown in FIG. [Diagram 3] FIG. 2 is a plan view showing a plurality of sensor blocks of the torque sensor shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV shown in FIG. [Diagram 5] 3 is a cross-sectional view taken along line VV shown in FIG. 2. [Figure 6] FIG. 1 is a diagram showing the relationship between the dimensions of a typical beam and the stiffness and output with respect to torque. [Figure 7] The figure shows the relationship between general beam dimensions and stiffness against moment. [Figure 8] FIG. 11 is a plan view showing a torque sensor according to a second embodiment. [Figure 9] FIG. 9 is a plan view showing a part of FIG. 8. [Figure 10] FIG. 10 is a cross-sectional view taken along line XX shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment will be described with reference to the drawings. In the drawings, the same parts are denoted by the same reference numerals.

[0012] (First embodiment) 1 to 7 show a torque sensor 10 according to a first embodiment. As shown in Fig. 1 and Fig. 2, the torque sensor 10 includes an annular first structure 11, an annular second structure 12, a plurality of third structures 13 as beams, and a plurality of sensor blocks 14 as a fourth structure.

[0013] As described later, the first structure 11, the second structure 12, and the third structure 13 have a function of receiving torque in the direction of the arrow Z shown in FIG. 1, and the multiple sensor blocks 14 have a function of detecting torque and receiving moments in the directions of the arrows X and Y.

[0014] The first structure 11, the second structure 12, and the third structure 13 form an elastic body and are made of a metal, for example, aluminum. However, the material is not limited to aluminum, and other metals such as stainless steel, or resins may also be used.

[0015] The sensor block 14 is made of, for example, stainless steel. However, the sensor block 14 may be made of other metals or resins as long as the materials have higher rigidity than the first structure 11, the second structure 12, and the third structure 13.

[0016] 2, the first structure 11 has a plurality of holes 11a penetrating from the front surface to the back surface. A bolt 41 for attaching the first structure 11 to a robot arm (not shown) is inserted into each hole 11a.

[0017] The second structure 12 is disposed inside the first structure 11 and concentrically with respect to the first structure 11. The second structure 12 has a plurality of holes 12a penetrating from the front surface to the back surface. A bolt 42 is inserted into each hole 12a to attach the second structure 12 to a reducer connected to a motor (not shown).

[0018] The multiple third structures 13 are disposed between the first structure 11 and the second structure 12, and connect the first structure 11 and the second structure 12. The width W1 of the third structure 13 (the length along the direction around the axis passing through the center of the second structure 12) is wider than the interval W2 between two adjacent third structures 13 (the width of the opening between two adjacent third structures 13) (W1>W2).

[0019] As shown in Fig. 5, the first structure 11 and the second structure 12 have a thickness (length along the axial direction) T1, and the third structure 13 has a thickness T2 that is thinner than the thickness T1 (T1>T2). The thickness T2 of the third structure 13 is smaller than the width W1 of the third structure 13 (T2 <W1)。

[0020] 1 and 3, a plurality of sensor blocks 14 are disposed between the first structure 11 and the second structure 12 at the positions of some of the third structures 13. Specifically, eight sensor blocks 14 are disposed between the first structure 11 and the second structure 12 at the positions of eight of the third structures 13. The number of sensor blocks 14 is not limited to eight, and may be, for example, four or two.

[0021] As shown in FIG. 2, corresponding to each of the third structures 13 where the sensor blocks 14 are arranged, recesses 15 are provided. Each recess 15 is continuously provided in the first structure 11, the third structure 13, and the second structure 12. The recess 15 has a width W3 along the circumferential direction of the axis. The width W3 of the recess 15 is narrower than the width W1 of the third structure 13 and wider than the interval W2 between adjacent third structures 13 (W2 < W3 < W1). The third structures 13 (referred to as fifth structures 13a) located on both sides of the recess 15 each have a width W4, and the width W4 of the fifth structure 13a is narrower than the width W1 of the third structure 13 (W4 < W1) and narrower than the interval W2 between adjacent third structures 13 (W4 < W2).

[0022] As shown in FIG. 5, the recess 15 has a depth D1 along the axial direction. The depth D1 of the recess 15 is equal to the thickness T3 of the third structure 13 (D1 = T3), and the bottom surface of the recess 15 is arranged at a position approximately half of the thickness T2 of the third structure 13.

[0023] As shown in FIGS. 3 and 4, each sensor block 14 includes a first attachment portion 14a, a second attachment portion 14b, two connecting portions 14c, a housing portion 14d, a strain sensor 16, a first fixing member 17, a second fixing member 18, a first screw 19, and a second screw 20.

[0024] The first attachment portion 14a is arranged corresponding to the surface of the first structure 11, and the second attachment portion 14b is arranged corresponding to the surface of the second structure 12. The housing portion 14d is arranged corresponding to the recess 15 and is connected to the first attachment portion 14a, the second attachment portion 14b, and the two connecting portions 14c. The two connecting portions 14c are arranged between the first attachment portion 14a and the second attachment portion 14b corresponding to the surface of the third structure 13 and connect the first attachment portion 14a, the second attachment portion 14b, and the housing portion 14d. Each connecting portion 14c has the same width W4 as the width W4 of the third structure 13 located on both sides of the recess 15.

[0025] The first attachment part 14a has two holes 14e corresponding to the two holes 11a of the first structure 11, and the second attachment part 14b has two holes 14f corresponding to the two holes 12a of the second structure 12. As shown in FIG. 1, a bolt 41 inserted into the hole 11a of the first structure 11 is inserted into the hole 14e, and a bolt 42 inserted into the hole 12a of the second structure 12 is inserted into the hole 14f.

[0026] In a state where the housing part 14d of the sensor block 14 is housed in the recess 15, the first attachment part 14a is disposed on the first structure 11, and the second attachment part 14b is disposed on the second structure 12, the sensor block 14 is fixed to the surfaces of the first structure 11 and the second structure 12 by a plurality of bolts 41 and 42.

[0027] As shown in FIG. 4, each connecting part 14c, the first attachment part 14a, and the second attachment part 14b have a thickness T4, and the thickness T4 is smaller than the thickness T2 of the third structure 13 (T4 < T2). The housing part 14d has a width W5 that is equal to or less than the width W3 of the recess 15 (W5 ≦ W3), and the outer surface of the housing part 14d is configured to be able to be in close contact with the inner surface of the recess 15. Specifically, the outer surface of the housing part 14d that intersects the circumferential direction around the Z axis is configured to be able to be in close contact with the inner surface of the recess 15 that intersects the circumferential direction around the Z axis.

[0028] The housing part 14d has a recess 14j. The thickness of the side surface of the housing part 14d that intersects the circumferential direction around the Z axis (the thickness in the direction intersecting the circumferential direction around the Z axis) is substantially the same as the thickness T4 of the connecting part 14c.

[0029] The strain sensor 16, the first fixing member 17, the second fixing member 18, the first screw 19, and the second screw 20 are disposed inside the recess 14j (hereinafter, including the inside of the recess 14j, referred to as the housing part 14d).

[0030] The bottom of the accommodation section 14d has an opening 14g between the first structure 11 and the second structure 12. The bottom of the accommodation section 14d is separated by the opening 14g into a first portion 14h corresponding to the first structure 11 and a second portion 14i corresponding to the second structure 12. The strain sensor 16 is disposed inside the accommodation section 14d across the opening 14g.

[0031] As shown in FIG. 3, the strain sensor 16 includes a strain body 16a made of an elastic body, for example, a metal, and a plurality of strain gauges 16b arranged on the strain body 16a via an insulating film (not shown).

[0032] The flexure body 16a is disposed at the bottom of the housing portion 14d. Specifically, one end of the flexure body 16a is placed on the first portion 14h, and the other end is placed on the second portion 14i. The first fixing member 17 is placed on the first portion 14h and one end of the flexure body 16a, and the second fixing member 18 is placed on the second portion 14i and the other end of the flexure body 16a. The first screw 19 is inserted into the first portion 14h from its back surface and screwed into the first fixing member 17. Therefore, one end of the flexure body 16a is fixed to the first portion 14h by the first fixing member 17. The second screw 20 is inserted into the second portion 14i from its back surface and screwed into the second fixing member 18. Therefore, the other end of the flexure body 16a is fixed to the second portion 14i by the second fixing member 18.

[0033] The method of fixing the strain generating body 16a is not limited to this, and welding or an adhesive may also be used.

[0034] The plurality of strain gauges 16b included in the plurality of strain generating bodies 16a (the plurality of sensor blocks 14) form, for example, a plurality of bridge circuits (not shown), and the torque is detected by these bridge circuits.

[0035] Here, a further description will be given of the third structure 13 and the connecting portion 14c of the sensor block 14 in the first embodiment. Both the third structure 13 and the connecting portion 14c function as beams.

[0036] In general, stiffness and output are considered as the characteristics of a beam with respect to torque, and stiffness is considered as the characteristic of a beam with respect to moment.

[0037] FIG. 6 shows the relationship between the dimensions of a typical beam and the stiffness and output with respect to torque, and FIG. 7 shows the relationship between the dimensions of a typical beam and the stiffness with respect to moment.

[0038] As shown in Fig. 6, the relationship between the length, width, and thickness of the beam and the stiffness and output with respect to torque is contradictory. That is, to increase stiffness, it is necessary to shorten the length of the beam and increase the width and thickness of the beam. However, to increase the torque detection output, it is necessary to increase the length of the beam and decrease the width and thickness. In particular, the length and width of the beam have a greater effect on torque than the thickness.

[0039] On the other hand, in order to increase the rigidity with respect to the moment, it is necessary to shorten the length of the beam and increase the width and thickness of the beam, as shown in Fig. 7. In particular, the length and thickness of the beam have a greater effect on the moment than the width.

[0040] The length of the beam has a large effect on the stiffness and output of the torque. Therefore, if a design is based on the thickness of the beam, which has a small effect, the rated output torque can be obtained, but in order to increase the stiffness against the moment, it is necessary to increase the thickness of the beam. Therefore, the torque sensor becomes larger and heavier.

[0041] On the other hand, the width of the beam does not have a large effect on the moment, and can increase the rigidity against torque, so it is possible to increase the torque output by reducing the beam width.

[0042] For this reason, in the torque sensor 10 of the first embodiment, the width W1 of the third structure 13 is made larger than the interval W2 between two adjacent third structures 13 (W1>W2), and the thickness T2 of the third structure 13 is made smaller than the thickness T1 of the first structure 11 and the second structure 12 (T2 <T1)。

[0043] Further, the width W4 of the third structure 13 at the portion where the sensor block 14 is disposed is narrower than the width W1 of the third structure 13 at the portion where the sensor block 14 is not disposed (W4 < W1). The width of the connecting portion 14c as the beam of the sensor block 14 is also W4, and the thickness is T4 which is thinner than the thickness T2 of the third structure 13. Further, the thickness of the side surface of the accommodating portion 14d is substantially the same as the thickness T4 of the connecting portion 14c. Therefore, the sensor block 14 has a structure that is easily deformed by torque.

[0044] Therefore, when a Z-direction torque shown in FIG. 1 is applied to the torque sensor 10, the high-rigidity third structure 13 can receive the torque, and the detection output of the torque by the sensor block 14 can be improved.

[0045] Furthermore, the sensor block 14 disposed between the first structure 11 and the second structure 12 has a thickness T3 larger than the thickness T2 of the third structure 13 (T3 > T2). Therefore, the sensor block 14 can obtain rigidity against moments from the X-axis and Y-axis other than torque. Therefore, the torque sensor 10 can prevent the influence of the moment and improve the detection accuracy of the torque.

[0046] (Effect of the First Embodiment) According to the first embodiment, the torque sensor 10 includes the first structure 11, the second structure 12, and a plurality of third structures 13, and a plurality of sensor blocks 14 different from these. Therefore, even when any one of the plurality of third structures 13 is damaged, the influence on the sensor block 14 can be reduced. Therefore, it is not necessary to excessively increase the safety factor of the torque sensor 10 even at low rating or high rating. Therefore, the first structure 11, the second structure 12, and the third structure 13 can be thinned and lightened, and the torque sensor 10 can be miniaturized.

[0047] The torque sensor 10 includes a first structure 11, a second structure 12, a third structure 13, and a plurality of sensor blocks 14 separate from these, and receives torque through the third structure 13 and receives a moment other than torque through the plurality of sensor blocks 14. Therefore, the rigidity against the rated torque can be designed based on the width W1 of the third structure 13, and the rigidity against the moment can be designed based on the thickness T3 of the sensor block 14. Therefore, the rigidity against the rated torque and the rigidity against the moment can be designed separately, which can simplify the design.

[0048] Furthermore, the stress applied to each sensor block 14 can be adjusted by the first structure 11, the second structure 12, and the multiple third structures 13. Therefore, the same sensor block 14 can be used for both low and high ratings. This simplifies the design and allows the use of standardized parts, thereby reducing manufacturing costs.

[0049] Furthermore, the multiple sensor blocks 14 have a different configuration from the first structure 11, the second structure 12, and the third structure 13. Therefore, for example, if a failure occurs in any of the sensor blocks 14, the sensor block 14 can be easily replaced. Therefore, in the event of a failure, repair can be easily performed.

[0050] Second embodiment 8, 9 and 10 show a second embodiment. In the first embodiment, each sensor block 14 has a first mounting portion 14a and a second mounting portion 14b, and is attached to the surfaces of the first structure 11 and the second structure 12 by a plurality of bolts 41, .

[0051] In contrast, the sensor block 30 of the second embodiment does not have the first attachment portion 14a, the second attachment portion 14b, and the two connecting portions 14c.

[0052] 9 and 10, the first structure 11 has holes 11b communicating with the recesses 15 on its outer surface corresponding to each recess 15. The second structure 12 has holes 12b communicating with the recesses 15 on its inner surface corresponding to each recess 15.

[0053] Each sensor block 30 has a first screw hole 14k and a second screw hole 14l on both longitudinal sides of the housing portion 14d.

[0054] Each of the sensor blocks 30, when housed in the recess 15, is fixed in the recess 15 by a first screw 31 and a second screw 32. That is, the first screw 31 is inserted into the hole 11b of the first structure 11 and screwed into the first screw hole 14k of the housing portion 14d. The second screw 32 is inserted into the hole 12b of the second structure 12 and screwed into the second screw hole 14l of the housing portion 14d.

[0055] (Effects of the second embodiment) The second embodiment described above can also provide the same effects as the first embodiment. Moreover, since the sensor block 30 does not have the first mounting portion 14a, the second mounting portion 14b, and the two connecting portions 14c of the first embodiment, the structure is simple and the manufacture is easy.

[0056] Incidentally, the first and second embodiments are not limited to a torque sensor, but can also be applied to a force sensor that detects torque and a plurality of moments.

[0057] In addition, the present invention is not limited to the above-mentioned embodiments as they are, and in the implementation stage, the components can be modified and embodied without departing from the gist of the invention. In addition, various inventions can be formed by appropriately combining the multiple components disclosed in the above-mentioned embodiments. For example, some components may be deleted from all the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0058] 10...torque sensor, 11...first structure, 12...second structure, 13...third structure, 13a...fifth structure, 14...sensor block (fourth structure), 14a...first mounting portion, 14b...second mounting portion, 14g...opening, 14k...first screw hole, 14l...second screw hole, 15...recess, 16...strain sensor, 16a...strain element, 16b...strain gauge, 30...sensor block (fourth structure), 31...first screw, 32...second screw.

Claims

1. An annular first structure; an annular second structure disposed concentrically with the first structure; a plurality of third structures disposed between the first structure and the second structure and connecting the first structure and the second structure; At least two recesses are provided corresponding to at least two of the plurality of third structures, and are provided continuously on the surfaces of the first structure, the third structure, and the second structure; at least two fourth structures disposed within the at least two recesses, each having a first end fixed to the first structure and a second end fixed to the second structure; a strain sensor disposed inside each of the at least two fourth structures; A torque sensor comprising:

2. 2. The torque sensor according to claim 1, wherein a width of the third structure (fifth structure) located on both sides of each of the at least two recesses in a direction around an axis passing through a center of the second structure is narrower than a width of the third structure in a direction around the axis.

3. 2. The torque sensor according to claim 1, wherein a thickness of each of the third structures along an axis passing through a center of the second structure is thinner than a thickness of the fourth structure along the axis.

4. 2. The torque sensor according to claim 1, wherein each of the fourth structures has a first mounting portion fixed to a surface of the first structure and a second mounting portion fixed to a surface of the second structure.

5. 2. The torque sensor according to claim 1, wherein the fourth structure includes a first screw hole into which a first screw inserted from a side surface of the first structure is screwed, and a second screw hole into which a second screw inserted from a side surface of the second structure is screwed.

6. the fourth structure has an opening corresponding to a position between the first structure and the second structure, The torque sensor according to claim 1 , wherein the strain sensor is disposed across the opening.

7. 2. The torque sensor according to claim 1, wherein the strain sensor comprises a strain element and a plurality of strain gauges arranged on the strain element.

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