Torque sensor

Abstract

To provide a torque sensor which has high rigidity, and with which downsizing and weight reduction are possible.SOLUTION: An annular first structure 11 has a first outer diameter and a first inner diameter. An annular second structure 12 is disposed on a shaft of the first structure by being spaced apart from the first structure, and has a second outer diameter and a second inner diameter smaller than the first inner diameter. A plurality of third structures 13 are connected between the first structure and the second structure and have at least a thickness greater than or equal to the distance along the axial direction between the first structure and the second structure and a width wider than the distance between the first structure and the second structure in a direction orthogonal to the shaft. A plurality of strain sensors 14 are connected between the first structure and the second structure and disposed at right angles to the shaft.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] Embodiments of the present invention relate to a torque sensor applied to, for example, a joint of a robotic arm.

Background Art

[0002] When the rigidity of a joint of a robotic arm (hereinafter also simply referred to as an arm) is low, when the arm is operated, the position of the tip of the arm is difficult to determine due to inertia. Therefore, the joints of the arm need to have high rigidity.

[0003] In addition, in order to improve the detection accuracy of torque by the torque sensor disposed at the joint of the arm, the rigidity in the torque direction and the moment direction other than torque needs to be high.

[0004] Generally, for example, in the case of a torque sensor in which a plurality of beams are arranged between two annular elastic bodies having the same diameter, by optimizing the lengths and numbers of the plurality of beams, it is possible to increase the rigidity in the torque direction and the moment direction. In this case, by increasing the opening area of the two annular elastic bodies, weight reduction is possible. However, since a plurality of beams are arranged axially between the two elastic bodies, the thickness of the torque sensor increases, and it is difficult to make the torque sensor thinner (see, for example, Patent Document 1).

[0005] On the other hand, in the case of a torque sensor in which two annular elastic bodies having different diameters are concentrically arranged and a plurality of beams arranged radially are provided between these elastic bodies, it is possible to make the thickness of the beam (the thickness along the axial direction of the elastic body) equal to or less than the thickness along the axial direction of the two elastic bodies. Therefore, it is possible to realize a thin and highly accurate torque sensor. However, in this case, in order to obtain the required rigidity, it is necessary to make the two elastic bodies sufficiently thick, and the weight of the torque sensor increases (see Patent Documents 2, 3, and 4).

[0006] As described above, when increasing the rigidity of the torque sensor, the thickness and weight of the torque sensor increase, and the size becomes large.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0008] Embodiments of the present invention provide a torque sensor that is highly rigid, thin, and lightweight.

Means for Solving the Problems

[0009] The torque sensor of the present embodiment includes an annular first structure having a first outer diameter and a first inner diameter, an annular second structure disposed on the axis of the first structure and spaced apart from the first structure, the second structure having a second outer diameter and a second inner diameter smaller than the first inner diameter, a plurality of third structures connected between the first structure and the second structure, the third structures having a thickness of at least a distance along the axial direction between the first structure and the second structure and a width wider than a distance between the first structure and the second structure in a direction perpendicular to the axis, and a plurality of strain sensors connected between the first structure and the second structure and disposed perpendicular to the axis.

Brief Description of the Drawings

[0010]

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Best Mode for Carrying Out the Invention

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

[0012] (First Embodiment) FIGS. 1 to 5 show a torque sensor 10 according to the first embodiment. 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 strain sensors 14.

[0013] The first structure 11, the second structure 12, and the third structure 13 are elastic bodies and are made of a metal, for example, stainless steel. However, it is not limited to stainless steel, and other metals can also be applied.

[0014] As shown in FIG. 2, the first structure 11 has a first outer diameter OD1 and a first inner diameter ID1 smaller than the first outer diameter OD1, and the second structure 12 has a second outer diameter OD2 smaller than the first inner diameter ID1 and a second inner diameter ID2 smaller than the second outer diameter OD2 (OD1>ID1>OD2>ID2).

[0015] The second structure 12 is concentric with the first structure 11 and is arranged at a predetermined interval, for example, a distance L (shown in FIG. 3), from the first structure 11 along the axial direction passing through the center of the first structure 11.

[0016] As shown in FIG. 1, the thickness T1 of the first structure 11 along the axial direction is equal to the thickness T2 of the second structure 12 along the axial direction (T1 = T2). However, it is not limited to this, and the thickness T1 of the first structure 11 and the thickness T2 of the second structure 12 may be different.

[0017] The plurality of third structures 13 are arranged radially with respect to the first structure 11 and the second structure 12, and connect the first structure 11 and the second structure 12 that are axially separated. Details of the third structure 13 will be described later.

[0018] As shown in FIG. 2, the plurality of strain sensors 14 are arranged in a direction orthogonal to the axis between the first structure 11 and the second structure 12 at positions different from the third structure 13. In the first embodiment, the number of strain sensors 14 is, for example, eight, but is not limited thereto, and may be four or two.

[0019] Each strain sensor 14 includes a strained body 14a made of an elastic body, for example, a metal, and a plurality of strain gauges 14b arranged on the strained body 14a via an insulating film (not shown).

[0020] One end of the strained body 14a is arranged on the first structure 11, and the other end is arranged on the second structure 12. One end of the strained body 14a is fixed to the first structure 11 by a fixing member 15a arranged on the first structure 11 and a screw 15b inserted from the back surface of the first structure 11 and screwed into the fixing member 15a. The other end of the strained body 14a is fixed to the second structure 12 by a fixing member 16a arranged on the second structure 12 and a screw 16b inserted from the back surface of the second structure 12 and screwed into the fixing member 16a.

[0021] The plurality of strain sensors 14 constitute, for example, a plurality of bridge circuits (not shown), and torque is detected by these bridge circuits.

[0022] Note that the strain sensor 14 and the configuration for fixing it are omitted from FIGS. 1, 4, and 5. Further, this embodiment is not limited to a torque sensor, and can also be applied to a force sensor that detects torque and a plurality of moments.

[0023] As shown in FIGS. 1, 3, and 4, the first structure 11 includes a first surface (hereinafter also referred to as the front surface) 11a, a second surface (hereinafter also referred to as the back surface) 11b parallel to the first surface 11a, a first outer surface (hereinafter also referred to as the outer surface) 11c connecting the outside of the first surface 11a and the outside of the second surface 11b, and a first inner surface (hereinafter also referred to as the inner surface) 11d connecting the inside of the first surface 11a and the inside of the second surface 11b.

[0024] The second structure 12 includes an annular third surface (hereinafter also referred to as the front surface) 12a, a fourth surface 12b (hereinafter also referred to as the back surface) parallel to the third surface 12a, a second outer surface (hereinafter also referred to as the outer surface) 12c connecting the outside of the third surface 12a and the outside of the fourth surface 12b, and a second inner surface (hereinafter also referred to as the inner surface) 12d connecting the inside of the third surface 12a and the inside of the fourth surface 12b.

[0025] The first structure 11 includes a plurality of holes 11e and 11f penetrating from the front surface 11a to the back surface 11b, and the second structure 12 includes a plurality of holes 12e and 12f penetrating from the front surface 12a to the back surface 12b.

[0026] Bolts (not shown) for fixing the first structure 11 to a robot arm (not shown), for example, are inserted into the hole 11e, and bolts (not shown) for fixing the second structure 12 to a speed reducer connected to a motor (not shown), for example, are inserted into the hole 12e.

[0027] A screw 15b screwed into the aforementioned fixing member 15a is inserted into the hole 11f, and a screw 16b screwed into the aforementioned fixing member 16a is inserted into the hole 12f.

[0028] A plurality of third structures 13 connect the first structure 11 and the second structure 12 that are axially separated. For this reason, the axial thickness T3 of the third structure 13 is larger than the thickness T1 of the first structure 11 and the thickness T2 of the second structure 12 (T3>T1, T2). Also, the third structure 13 has a width W in the circumferential direction. The width W of the third structure 13 in the circumferential direction is determined according to, for example, the maximum stress with respect to torque.

[0029] As shown in FIGS. 1 to 5, the strain sensor 14 is disposed between a pair of third structures 13. The pair of third structures 13 are connected to at least the surface 11a of the first structure 11 and at least the back surface 12b of the second structure 12.

[0030] As shown in FIG. 5, in a portion corresponding to the space between the pair of third structures 13 where the strain sensor 14 is disposed, a first recess 11g, a second recess 12g, a third recess 11h, and a fourth recess 12h are provided. The first recess 11g is disposed above the surface of the first structure 11, and the second recess 12g is disposed below the surface of the second structure 12 at a position corresponding to the first recess 11g, that is, at a corresponding position in a direction perpendicular to the axis. The horizontal positions of the bottom surfaces of the first recess 11g and the second recess 12g are equal. Specifically, the position of the bottom surface of the first recess 11g is higher than the position of the surface of the first structure 11, and the position of the bottom surface of the second recess 12g is lower than the position of the back surface 12b of the second structure 12.

[0031] The third recess 11h is disposed on the back surface of the first structure 11 at a position corresponding to the first recess 11g, and the fourth recess 12h is disposed on the back side of the second structure 12 at a position corresponding to the third recess 11h. The horizontal positions of the bottom surfaces of the third recess 11h and the fourth recess 12h are equal. Specifically, the position of the bottom surface of the third recess 11h is higher than the position of the surface 11a of the first structure 11, and the position of the bottom surface of the fourth recess 12h is lower than the position of the back surface 12b of the second structure 12.

[0032] In other words, the portion where the first recess 11g to the fourth recess 12h are provided has a thickness T3 equivalent to that of the third structure 13, and the bottom surfaces of the first recess 11g and the second recess 12g are disposed at positions axially higher than the surface 11a of the first structure 11.

[0033] One end of the strain generating body 14a constituting the strain sensor 14 is placed on the bottom surface of the first recess 11g, and the other end of the strain generating body 14a is placed on the bottom surface of the second recess 12g. Further, a fixing member 15a is placed on the bottom surface of the first recess 11g, and a fixing member 16a is placed on the bottom surface of the second recess 12g.

[0034] The aforementioned hole 11f penetrates from the first recess 11g to the third recess 11h, and the hole 12f penetrates from the second recess 12g to the fourth recess 12h.

[0035] (Configuration of the third structure) FIG. 6 shows the third structure 13 taken out. The third structure 13 connects the first structure 11 and the second structure 12 with different diameters arranged apart in the axial direction. For this reason, the shape of the side surface of the third structure 13 is substantially a parallelogram, and has a thickness T3 greater than or equal to the axial distance L between the first structure 11 and the second structure 12 (T3 ≧ L).

[0036] Furthermore, the third structure 13 has a length L2 greater than the distance L1 between the first structure 11 and the second structure 12 in the direction orthogonal to the axis. In other words, the third structure 13 has a length L2 greater than the distance L1 which is half of the difference between the first inner diameter ID1 (shown in FIG. 2) of the first structure 11 and the second outer diameter OD2 (shown in FIG. 2) of the second structure 12.

[0037] The third structure 13 includes a first portion 13a and a second portion 13b orthogonal to the axis passing through the centers of the first structure 11 and the second structure 12, and a third portion 13c and a fourth portion 13d inclined with respect to the axis. Furthermore, the third structure 13 includes a first stepped portion 13e between the first portion 13a and the third portion 13c, and a second stepped portion 13f between the second portion 13b and the fourth portion 13d.

[0038] The first portion 13a of the third structure 13 is connected to the back surface 12b of the second structure 12, and the first stepped portion 13e is connected to the outer surface 12c. The second portion 13b of the third structure 13 is connected to the front surface 11a of the first structure 11, and the second stepped portion 13f is connected to the inner surface 11d of the first structure 11. The angle formed by the fourth portion 13d of the third structure 13 and the front surface 11a of the first structure 11 is θ1, and the angle formed by the third portion 13c of the third structure 13 and the back surface 12b of the second structure 12 is also θ1 (not shown).

[0039] In the first part 13a of the third structure 13, the portion connected to the outer surface 12c of the second structure 12 includes a recess 13g that is recessed in the axial direction, and includes a protrusion 13h as a side surface on the first structure 11 side of the recess 13g. However, it is not limited to this, and it may be flat and parallel to the surface 12a of the second structure 12.

[0040] The operation of the third structure 13 will be described with reference to the configuration shown in FIG. 6. The third structure 13 of the first embodiment has an operation of suppressing deformation with respect to moments Mx and My in directions other than torque.

[0041] Specifically, when a moment Mz in the torque direction is applied between the first structure 11 and the second structure 12, the first structure 11 and the second structure 12 are relatively displaced in the circumferential direction around the axis. On the other hand, when moments Mx and / or My in directions other than torque are applied between the first structure 11 and the second structure 12, the first structure 11 and the second structure 12 are displaced so as to incline with respect to the axis.

[0042] In contrast, the third structure 13 has a length L2 that is greater than the distance L1 between the first structure 11 and the second structure 12 in a direction orthogonal to the axis, and has a thickness T3 that is greater than or equal to the axial distance L between the first structure 11 and the second structure 12. For this reason, the third structure 13 can easily displace the first structure 11 and the second structure 12 in the direction of arrow A or B in the drawing with respect to the moment Mz in the torque direction, and can suppress the displacement of the first structure 11 and the second structure 12 in the direction of arrow C or D in the drawing with respect to moments Mx and My other than torque. That is, when a moment Mz in the torque direction is applied to the torque sensor 10, it is possible to suppress deformation caused by moments Mx and My in directions other than torque.

[0043] Furthermore, the first portion 13a of the third structure 13 includes a recess 13g corresponding to the space between the first structure 11 and the second structure 12, and includes a protrusion 13h on the side surface of the recess 13g on the side of the first structure 11. By including this protrusion 13h, the third structure 13 can further suppress displacement of the first structure 11 and the second structure 12 in the direction of the illustrated arrow C or D with respect to moments Mx and My other than torque.

[0044] (First modification of the third structure) The angle formed between the fourth portion 13d of the third structure 13 and the surface of the first structure 11 is not limited to θ1.

[0045] FIG. 7 shows a first modification of the third structure 13, and the angle formed between the fourth portion 13d of the third structure 13 and the surface 11a of the first structure 11 is an angle θ2 greater than θ1 (θ1 < θ2). In other words, the lengths of the first portion 13a and the second portion 13b of the third structure 13 are longer than the lengths of the first portion 13a and the second portion 13b of the third structure 13 shown in FIG. 6.

[0046] The third structure 13 according to the first modification has an increased volume compared to the third structure 13 shown in FIG. 6. For this reason, the mass of the torque sensor 10 including the weight of the third structure 13 increases, but since the rigidity of the third structure 13 is increased, it is possible to improve the rigidity with respect to moments Mx and My in each direction.

[0047] Furthermore, the first portion 13a of the third structure 13 includes a recess 13g corresponding to the space between the first structure 11 and the second structure 12, and includes a protrusion 13h on the side surface of the recess 13g on the side of the first structure 11. By including this protrusion 13h, the third structure 13 can further suppress displacement of the first structure 11 and the second structure 12 in the direction of the illustrated arrow C or D with respect to moments Mx and My other than torque.

[0048] FIG. 8 shows the relationship between the angle formed by the surface of the first structure 11 and the fourth portion 13d of the third structure 13, the displacement amounts with respect to the moments Mx and My, the mass, and the stress in the torque direction. In FIG. 8, curve A represents the displacement amounts with respect to the moments Mx and My, curve B represents the mass, curve C represents the stress in the torque direction, and curve D represents the approximation of curve C.

[0049] When torque is applied to the torque sensor 10, the stress, as shown by curve D, decreases in the range of angles from 40° to 60°, and reaches the minimum in the range of angles from 45° to 50°. Therefore, the range of angles necessary for detecting torque is from 40° to 60°, preferably from 45° to 50°.

[0050] On the other hand, the displacement amounts with respect to the moments Mx and My are the smallest when the angle is 45° or more, as shown by curve A. That is, it can be seen that the rigidity with respect to the moments Mx and My is high in the range of angles from 45° to 90°. In other words, the longer the length of the first portion 13a of the third structure 13, the higher the rigidity with respect to the moments Mx and My. However, as shown by curve B, the mass of the third structure 13 increases as the angle increases.

[0051] Therefore, in the first embodiment, when considering torque detection and the rigidity with respect to moments, the angle formed by the surface 11a of the first structure 11 and the second portion 13b of the third structure 13 is preferably in the range of 40° to 60°, and more preferably in the range of 45° to 50°.

[0052] (Effect of the First Embodiment) According to the first embodiment, the second structure 12 has an outer diameter smaller than the inner diameter of the first structure 11, is arranged axially separated from the first structure 11, and the plurality of third structures 13 connecting the first structure 11 and the second structure 12 have a length L2 greater than the distance L1 between the first structure 11 and the second structure 12 in a direction perpendicular to the axis, and have a thickness T3 greater than or equal to the axial distance L between the first structure 11 and the second structure 12. Therefore, it is possible to suppress deformation caused by moments Mx and My in directions other than torque, and it is possible to configure a high-rigidity torque sensor.

[0053] Moreover, the first portion 13a of the third structure 13 is connected to at least the fourth surface 12d of the second structure 12, and the second portion 13b of the third structure 13 is formed on at least the first surface 11a of the first structure 11. Therefore, while maintaining the rigidity of the torque sensor 10, the thicknesses T1 and T2 of the first structure 11 and the second structure 12 can be made thinner. Therefore, it is possible to reduce the thickness (miniaturize) and weight of the torque sensor 10.

[0054] Furthermore, according to the configuration of the third structure 13, when a moment Mz in the torque direction is applied to the torque sensor 10, it is possible to suppress deformation caused by moments Mx and My in directions other than torque. Therefore, it is possible to prevent cross-axis interference and accurately detect torque.

[0055] Also, the angle formed by the surface 11a of the first structure 11 and the fourth portion 13d of the third structure 13 is in the range of 40° to 60°. Therefore, even if the thicknesses of the first structure 11 and the second structure 12 are made thinner and the weight is reduced, the rigidity in the directions of moments Mx and My can be improved, and an increase in the total axial thickness (height) of the first structure 11, the second structure 12, and the third structure 13 can be suppressed. Therefore, the torque sensor 10 of the first embodiment can provide a high-rigidity, thin, and lightweight torque sensor while maintaining the detection accuracy of torque.

[0056] FIG. 9A shows a case where the torque sensor 10 according to the first embodiment is applied to the robot arm 31, and FIG. 9B shows a case where the torque sensor 32 as shown in Patent Document 1 is applied to the robot arm 31.

[0057] When the rigidity of the joint of the robot arm is low, when the robot arm is driven and moved to a predetermined position, it is difficult to determine the position of the tip of the arm due to inertia. For this reason, the joint of the robot arm is required to have high rigidity including the torque sensor. Also, the inertia when the robot arm stops is more easily suppressed when the weight of the joint including the torque sensor is lighter. Further, as shown in FIG. 9A, when the axial height H of the torque sensor 10 is shorter than the axial height H of the torque sensor 32 shown in FIG. 9B, moments other than torque become smaller. For this reason, the influence of cross-axis interference is small, and more accurate control becomes possible. In other words, when the load applied to the robot arm 10 is equal, the larger the axial height H of the torque sensor 10, the larger the moment other than torque applied to the torque sensor 10.

[0058] FIG. 10 shows the axial height of the torque sensor and the displacement amount in the axial direction (z-axis) when moments Mx and My are applied. The torque sensor 10 of the first embodiment can significantly reduce the displacement amount in the axial direction (z-axis) when moments Mx and My are applied compared to the structure of Patent Document 2, although the height H is slightly larger than the structure of Patent Document 2 and the height H is 1 / 2 of the structure of Patent Document 1. That is, the torque sensor 10 of the first embodiment can be thin and has high rigidity against moments Mx and My. Therefore, it is possible to prevent cross-axis interference and improve the detection accuracy of torque.

[0059] Although FIG. 10 explains the effects by comparing the first embodiment with Patent Documents 1 and 2, the first embodiment can obtain the same effects as Patent Documents 1 and 2 with respect to Patent Documents 3 and 4 as well.

[0060] (Modification of the third structure) FIG. 11 shows a second modification of the third structure 13. In the second modification, the third structure 13 has a first stepped portion 13e between the first portion 13a and the fourth portion 13d, and a second stepped portion 13f between the second portion 13b and the third portion 13c.

[0061] The first portion 13a of the third structure 13 is connected to the back surface 12b of the second structure 12, and the first stepped portion 13e is connected to the outer surface 12c of the second structure 12. The second portion 13b of the third structure 13 is connected to the front surface 11a of the first structure 11, and the second stepped portion 13f is connected to the inner surface 11d of the first structure 11. The angle formed between the fourth portion 13d of the third structure 13 and the front surface 11a of the first structure 11 is θ.

[0062] Also by the second modification, it is possible to obtain the same effects as in the first embodiment. Moreover, since the volume of the third structure 13 can be reduced as compared with the first embodiment, the torque sensor 10 can be further lightened.

[0063] FIG. 12 shows a third modification of the third structure 13. In the third modification, the third structure 13 has a parallelogram side surface shape, and the entire first portion 13a of the third structure 13 is connected to the back surface 12b of the second structure 12, and the entire second portion 13b of the third structure 13 is connected to the front surface 11a of the first structure 11. The third portion 13c and the fourth portion 13d as the inclined portions of the third structure 13 are not connected to either the first structure 11 or the second structure 12.

[0064] Also by the third modification, it is possible to obtain the same effects as in the first embodiment. Moreover, since the volume of the third structure 13 can be further reduced as compared with the second modification, the torque sensor 10 can be further lightened.

[0065] Further, in the second and third modified examples, the second structure 12 can be formed into concentric circles in which a part in the radial direction overlaps with the first structure 11 within the range of the angle θ formed between the fourth portion 13d of the third structure 13 and the surface 11a of the first structure 11. However, by forming recesses in the first structure 11 and the second structure 12 respectively, it is possible to dispose the strain sensor 14 between the first structure 11 and the second structure 12.

[0066] Also, in the second and third modified examples, the width W of the third structure 13 may vary according to the required torque and the maximum stress with respect to the moment.

[0067] FIG. 13 shows a fourth modified example of the third structure 13. In the fourth modified example, the side surface shape of the third structure 13 is not a parallelogram but a rectangle. For this reason, the third portion 13c and the fourth portion 13d intersect at right angles with respect to the first portion 13a and the second portion 13b, and the angle formed between the fourth portion 13d and the surface 11a of the first structure 11 is 90°.

[0068] A part of the first portion 13a of the third structure 13 is connected to the back surface 12b of the second structure 12, and a part of the second portion 13b is connected to the surface 11a of the first structure 11. The rectangular third structure 13 has a characteristic of high rigidity with respect to the moments Mx and My, as is apparent from the curve A shown in FIG. 8.

[0069] FIG. 14 shows a fifth modified example of the third structure 13. In the third structure 13 of the fifth modified example, a part of the third structure 13 shown in the fourth modified example is chamfered and removed, and the side surface shape is a parallelogram. For this reason, the third structure 13 includes an inclined third portion 13c and a fourth portion 13d.

[0070] A part of the first portion 13a of the third structure 13 is connected to the back surface 12b of the second structure 12, and a part of the second portion 13b is connected to the surface 11a of the first structure 11. The third structure 13 of the fifth modified example can be made lighter than the third structure 13 shown in the fourth modified example.

[0071] FIG. 15 shows a sixth modification of the third structure 13. In the sixth modification, the third structure 13 is substantially rectangular, and the angle formed by the fourth portion 13d and the surface 11a of the first structure 11 is 90°. The third structure 13 includes a first step portion 13e between the first portion 13a and the third portion 13c, and a second step portion 13f between the second portion 13b and the fourth portion 13d.

[0072] A part of the first portion 13a of the third structure 13 is connected to the back surface 12b of the second structure 12, and the first step portion 13e is connected to the outer surface 12c of the second structure 12. Therefore, the other part of the first portion 13a is made to coincide with the surface of the second structure 12. A part of the second portion 13b of the third structure 13 is connected to the surface 11a of the second structure 12, and the second step portion 13f is connected to the inner surface 11d of the first structure 11. Therefore, the other part of the second portion 13b is made to coincide with the back surface of the first structure 11.

[0073] As will be described later, the third structure 13 of the sixth modification can reduce the maximum stress when moments Mx and My are applied as compared with the third structure 13 of the fourth modification, and can improve the rigidity in the axial (z-axis) direction.

[0074] FIG. 16 shows a seventh modification of the third structure 13. In the third structure 13 of the seventh modification, a part of the third structure 13 shown in the sixth modification is chamfered and removed. Therefore, the third structure 13 includes an inclined third portion 13c and a fourth portion 13d. That is, the angle formed by the fourth portion 13d and the surface 11a of the first structure 11 is less than 90°. The third structure 13 of the seventh modification is the same as the third structure 13 of the first embodiment, but is shown for convenience of explanation. The seventh modification can be made lighter than the sixth modification.

[0075] Here, the shape of the third structure 13 of the second modification example shown in FIG. 11 is referred to as (outer-outer-inclined), the shape of the third structure 13 of the third modification example shown in FIG. 12 is referred to as (inner-inner-inclined), the shape of the third structure 13 of the fourth modification example shown in FIG. 13 is referred to as (inner-inner-square), the shape of the third structure 13 of the fifth modification example shown in FIG. 14 is referred to as (inner-inner-rounded), the shape of the third structure 13 of the sixth modification example shown in FIG. 15 is referred to as (outer-outer-square), and the shape of the third structure 13 of the seventh modification example shown in FIG. 16 is referred to as (outer-outer-rounded).

[0076] FIG. 17 shows the relationship between the maximum stress when moments Mx and My are applied to the third structure 13 according to the second to seventh modification examples shown in FIGS. 11 to 16 and the displacement amount in the axial (z-axis) direction. The smaller the numerical value of the displacement amount in the axial (z-axis) direction, the higher the rigidity. Note that the width W and the length L2 of the third structure 13 of each modification example are the same.

[0077] As shown by E in FIG. 17, when the third structure 13 (inner-inner-inclined) of the third modification example shown in FIG. 12 is used as a reference, it can be seen that the third structure 13 (outer-outer-inclined) of the second modification example shown in FIG. 11 can reduce the maximum stress and has higher rigidity compared to the third modification example.

[0078] Furthermore, when assuming that the maximum stress of the second modification example (outer-outer-inclined) shown in FIG. 11 is equal to the maximum stress of the third modification example (inner-inner-inclined) shown in FIG. 12, since the third structure 13 of the second modification example (outer-outer-inclined) has higher rigidity than the third structure 13 of the third modification example (inner-inner-inclined), it is possible to reduce the thickness and the axial interval between the first structure 11 and the second structure 12. Therefore, the torque sensor 10 can be miniaturized and thinned.

[0079] Also, as shown by F in Fig. 17, the third structure 13 of the fourth modification (inner-inner-square) shown in Fig. 13 and the fifth modification (inner-inner-chamfered) shown in Fig. 14 has the same rigidity as the third structure of the third modification (inner-inner-inclined) shown in Fig. 12 in the axial direction (z-axis direction) when a moment is applied, and it can be seen that the maximum stress is reduced. For this reason, in the fourth modification (inner-inner-square) and the fifth modification (inner-inner-chamfered), it is possible to reduce the thickness and the axial interval between the first structure 11 and the second structure 12 compared to the third modification (inner-inner-inclined). Therefore, it is possible to miniaturize and thin the torque sensor 10.

[0080] Furthermore, as shown by G in Fig. 17, the third structure 13 of the sixth modification (outer-outer-square) shown in Fig. 15 and the seventh modification (outer-outer-chamfered) shown in Fig. 16 has a higher rigidity in the axial direction (z-axis direction) when a moment is applied compared to the third structure of the second modification (outer-outer-inclined) shown in Fig. 11, and it can be seen that the maximum stress is reduced. For this reason, in the sixth modification (outer-outer-square) and the seventh modification (outer-outer-chamfered), it is possible to reduce the thickness and the axial interval between the first structure 11 and the second structure 12 compared to the second modification (outer-outer-inclined). Therefore, it is possible to make the torque sensor 10 smaller and thinner.

[0081] (Second Embodiment) Figs. 18 and 19 show the second embodiment of the torque sensor. In the first embodiment, the plurality of third structures 13 are arranged independently of each other, except for the pair of third structures 13 arranged on both sides of the strain sensor 14.

[0082] On the other hand, in the second embodiment, all the third structures 13 disposed on both sides of the strain sensor 14 are connected on the surface 11a of the first structure 11. That is, the surface 11a of the first structure 11 includes an annular first connecting portion 11i, and the plurality of third structures 13 are connected by the first connecting portion 11i. The thickness of the first connecting portion 11i along the axial direction of the first structure 11 is equal to the distance L12 from the surface 11a of the first structure 11 to the surface 12a of the second structure 12, and the width W12 in the direction orthogonal to the axis is approximately 1 / 8 of the width W1 of the first structure 11. However, the thickness and width of the first connecting portion 11i are not limited thereto.

[0083] According to the second embodiment, the plurality of third structures 13 are connected by the annular first connecting portion 11i provided on the surface 11a of the first structure 11. Therefore, the rigidity of the plurality of third structures 13 and the first structure 11 can be increased. Accordingly, it is possible to suppress an increase in the thickness of the torque sensor 10 and increase the maximum stress with respect to torque and moment, and it is possible to improve the detection accuracy of torque by the torque sensor 10.

[0084] (Third Embodiment) Figs. 20 and 21 show the third embodiment. In the second embodiment, the plurality of third structures 13 are connected by the first connecting portion 11i on the surface 11a of the first structure 11.

[0085] On the other hand, in the third embodiment, the plurality of third structures 13 are connected by a second connecting portion 12i on the back surface 12b of the second structure 12. That is, the back surface 12b of the second structure 12 includes an annular second connecting portion 12i, and the plurality of third structures 13 are connected by the second connecting portion 12i. The thickness of the second connecting portion 12i along the axial direction of the second structure 12 is equal to the distance L12 from the back surface 12b of the second structure 12 to the back surface 11b of the first structure 11, and the width W12 in the direction orthogonal to the axis is approximately 1 / 8 of the width W2 of the second structure 12. However, the thickness and width of the second connecting portion 12i are not limited thereto.

[0086] According to the third embodiment, the plurality of third structures 13 are connected by an annular second connecting portion 12i provided on the back surface 12b of the second structure 12. Therefore, the rigidity of the plurality of third structures 13 and the second structure 12 can be increased. Accordingly, it is possible to suppress an increase in the thickness of the torque sensor 10 and increase the maximum stress with respect to torque and moment, and it is possible to improve the detection accuracy of torque by the torque sensor 10.

[0087] (Fourth Embodiment) FIG. 22 shows the fourth embodiment. The fourth embodiment is a combination of the second embodiment and the third embodiment.

[0088] In the fourth embodiment, the plurality of third structures 13 are connected by an annular first connecting portion 11i provided on the front surface 11a of the first structure 11 and an annular second connecting portion 12i provided on the back surface 12b of the second structure 12. Therefore, the rigidity of the plurality of third structures 13, the first structure 11, and the second structure 12 can be increased. Accordingly, it is possible to suppress an increase in the thickness of the torque sensor 10 and further increase the maximum stress with respect to torque and moment, and it is possible to improve the detection accuracy of torque by the torque sensor 10.

[0089] In addition, the present invention is not limited to the above-described embodiments as they are, and at the implementation stage, the components can be modified and embodied without departing from the gist thereof. Also, various inventions can be formed by appropriately combining the plurality of components disclosed in the above-described 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.

Description of Reference Numerals

[0090] 10… Torque sensor, 11… First structure, 12… Second structure, 13… Third structure, 14… Strain sensor, 11a… First surface (front surface), 11b… Second surface (back surface), 11c… First outer surface (outer surface), 11d… First inner surface (inner surface), 11i… First connecting part, 12a… Third surface (front surface), 12b… Fourth surface (back surface), 12c… Second outer surface (outer surface), 12d… Second inner surface (inner surface), 12i… Second connecting part, 13a… First part, 13b… Second part, 13c… Third part, 13d… Fourth part, 13e… First stepped portion, 13f… Second stepped portion, 13g… Recess, 13h… Projection, OD1… First outer diameter, OD2… Second outer diameter, ID1… First inner diameter, ID2… Second inner diameter.

Claims

1. An annular first structure having a first outer diameter and a first inner diameter; An annular second structure disposed axially spaced from the first structure and having a second outer diameter and a second inner diameter smaller than the first inner diameter; A plurality of third structures connected between the first structure and the second structure and having a thickness of at least the axial distance between the first structure and the second structure and a width wider than the distance between the first structure and the second structure in a direction perpendicular to the axis; A plurality of strain sensors connected between the first structure and the second structure and arranged perpendicular to the axis; A torque sensor comprising the above.

2. The third structure is at least a quadrilateral including a first portion and a second portion perpendicular to the axis, and a third portion and a fourth portion having an angle of not more than a right angle with the axis, and at least the first portion is connected to the second structure, and at least the second portion is connected to the first structure. The torque sensor according to claim 1.

3. The angle formed by the fourth portion of the third structure and the first structure is in the range of 40° to 60°. The torque sensor according to claim 2.

4. The angle formed by the fourth portion of the third structure and the first structure is in the range of 45° or more and 50° or less. The torque sensor according to claim 2.

5. The first portion of the third structure includes a recess corresponding to between the first structure and the second structure, and includes a protrusion as a side surface on the first structure side of the recess. The torque sensor according to claim 2.

6. The first structure has an annular first surface, an annular second surface parallel to the first surface, a first outer surface connecting the outside of the first surface and the second surface, and a first inner surface connecting the inside of the first surface and the second surface; The second structure has an annular third surface, an annular fourth surface parallel to the third surface, a second outer surface connecting the outside of the third surface and the fourth surface, and a second inner surface connecting the inside of the third surface and the fourth surface. The torque sensor according to claim 2.

7. The first portion of the plurality of third structures is connected to at least the fourth surface of the second structure, and the second portion of the plurality of third structures is connected to at least the first surface of the first structure. The torque sensor according to claim 6.

8. The plurality of third structures include a first stepped portion between the first portion and the third portion, and a second stepped portion between the second portion and the fourth portion. The first stepped portion is connected to the second outer surface of the second structure, and the second stepped portion is connected to the first inner surface of the first structure. The torque sensor according to claim 6, characterized in that.

9. The third structure includes a first stepped portion between the first portion and the fourth portion, and a second stepped portion between the second portion and the third portion. The first portion is connected to the fourth surface of the second structure, the first stepped portion is connected to the second outer surface of the second structure, the second portion is connected to the first surface of the first structure, the second stepped portion is connected to the first inner surface of the first structure, and the angle formed by the fourth portion and the first surface of the first structure is less than a right angle. The torque sensor according to claim 6, characterized in that.

10. The third structure has a parallelogram side shape, the first portion is connected to the fourth surface of the second structure, and the second portion is connected to the first surface of the first structure. The torque sensor according to claim 6, characterized in that.

11. The third structure has a rectangular side shape, a part of the first portion is connected to the fourth surface of the second structure, and a part of the second portion is connected to the first surface of the first structure. The torque sensor according to claim 6, characterized in that.

12. The third structure has a parallelogram side shape, a part of the first portion is connected to the fourth surface of the second structure, and a part of the second portion is connected to the first surface of the first structure. The torque sensor according to claim 6, characterized in that.

13. The third structure includes a first stepped portion between the first portion and the third portion, and a second stepped portion between the second portion and the fourth portion. A part of the first portion is connected to the fourth surface of the second structure, the first stepped portion is connected to the second outer surface of the second structure, a part of the second portion is connected to the first surface of the first structure, the second stepped portion is connected to the first inner surface of the first structure, and the angle formed by the fourth portion and the first surface of the first structure is a right angle. The torque sensor according to claim 6, characterized in that.

14. The third structure includes a first stepped portion between the first portion and the third portion, and a second stepped portion between the second portion and the fourth portion. A part of the first portion is connected to the fourth surface of the second structure, the first stepped portion is connected to the second outer surface of the second structure, a part of the second portion is connected to the first surface of the first structure, the second stepped portion is connected to the first inner surface of the first structure, and the angle formed by the fourth portion and the first surface of the first structure is less than a right angle. The torque sensor according to claim 6, characterized in that.

15. The first structure has a first recess where one end of the strain sensor is disposed, the second structure has a second recess where the other end of the strain sensor is disposed, and the position of the bottom of the second recess in the direction intersecting the axis of the first structure is the same as the position of the bottom of the first recess in the direction intersecting the axis of the first structure. The torque sensor according to claim 1, characterized in that.

16. The torque sensor according to claim 6, further comprising an annular first connecting portion for connecting the plurality of third structures on the first surface of the first structure.

17. The torque sensor according to claim 6, further comprising an annular second connecting portion for connecting the plurality of third structures on the fourth surface of the second structure.

18. The torque sensor according to claim 6, further comprising an annular first connecting portion for connecting the plurality of third structures on the first surface of the first structure and an annular second connecting portion for connecting the plurality of third structures on the fourth surface of the second structure.

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