Rotating shaft

Abstract

The present embodiment provides a rotary shaft in which the influence of a temperature change on the measurement accuracy of a torque sensor is reduced.SOLUTION: The rotary shaft 1 includes the shaft main body 30 and the torque sensor 10 that detects the torque generated in the shaft main body 30, the torque sensor 10 includes the first support portion 11c and the second support portion 11c disposed so as to be separated from and face the first support portion 11d, the first end portion of the torque sensor 10 is attached to the first support portion 11c, and the second end portion of the torque sensor 10 is attached to the second support portion 11d. The first support portion 11c, the flexure element 21, and the second support portion 11d are disposed along an axis of rotation of the shaft body 30, and α 1> α 2> α 3 or α 1 <α 2 <α 3 is satisfied, where α 1 is a linear expansion coefficient of the flexure element 21, α 2 is a linear expansion coefficient of the shaft body 30, and α 3 is a linear expansion coefficient of the first support portion 11c and the second support portion 11d.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a rotating shaft provided with a torque sensor. [Background technology]

[0002] In the field of automobiles, it is generally known to provide a torque sensor to detect the torque generated in a rotating shaft. For example, a torque detection device is disclosed in which a strain sensor is mounted on a protrusion provided on the outer circumferential surface of a shaft member (see Patent Document 1). Torque sensors are also used in fields other than automobiles. For example, it has been disclosed that an actuating unit used in a robot or the like is provided with a torque sensor that detects torque applied to the output shaft of a motor (see Patent Document 2). It has also been disclosed that in a robotic surgery system, multiple strain gauges are provided on the shaft of a manipulator and torque is detected by the strain gauges (see Patent Document 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6216879 [Patent Document 2] Japanese Patent Publication No. 2020-067295 [Patent Document 3] Special Publication No. 2009-522016 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when a torque sensor is provided on a rotating shaft to be measured, if the rotating shaft is deformed due to temperature changes, this deformation may result in a decrease in the accuracy of torque measurement.

[0005] An embodiment of the present invention provides a rotating shaft in which the effect of temperature changes on the measurement accuracy of a torque sensor is reduced. [Means for solving the problem]

[0006] The rotating shaft of this embodiment includes a shaft body having a cylindrical outer shape and rotating, and a torque sensor that detects torque generated in the shaft body, wherein the torque sensor includes a first attachment portion attached to a surface of the shaft body, a second attachment portion attached to the surface of the shaft body, a first support portion provided on the first attachment portion, a second support portion provided on the second attachment portion and arranged to face the first support portion at a distance, and a flexure element having a first end attached to the first support portion and a second end attached to the second support portion and having a plurality of strain gauges arranged on its surface, wherein the first support portion, the flexure element, and the second support portion are arranged along the axis of rotation of the shaft body, and wherein, where the linear expansion coefficient of the flexure element is α1, the linear expansion coefficient of the shaft body is α2, and the linear expansion coefficients of the first support portion and the second support portion are α3, α1>α2>α3 or α1<α2<α3 holds. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic view showing the configuration of a rotating shaft according to a first embodiment of the present invention. [Figure 2] FIG. 1 is a plan view showing the configuration of a torque sensor according to a first embodiment. [Figure 3] FIG. 3 is a cross-sectional view taken along line II-II shown in FIG. [Figure 4] FIG. 2 is a plan view showing a sensor main body according to the first embodiment. [Figure 5] FIG. 2 is a cross-sectional view showing the configuration of the strain gauge according to the first embodiment. [Figure 6] 3 is a cross-sectional view showing a torque sensor provided on the inner circumferential surface of the shaft body of the rotating shaft according to the first embodiment. FIG. [Figure 7] 3A and 3B are schematic diagrams for explaining the operation of the torque sensor according to the first embodiment. [Figure 8]FIG. 2 is a schematic view illustrating the rigidity of the torque sensor according to the first embodiment. [Figure 9] FIG. 10 is a plan view showing a sensor main body according to a first modified example of the first embodiment. [Figure 10] FIG. 10 is a plan view showing a sensor main body according to a second modified example of the first embodiment. [Figure 11] FIG. 10 is a cross-sectional view showing a first mounting configuration of a torque sensor according to a second modified example of the first embodiment. [Figure 12] FIG. 10 is a cross-sectional view showing a second mounting configuration of the torque sensor according to the second modified example of the first embodiment. [Figure 13] FIG. 10 is a perspective view showing a rotary shaft of a third modified example of the first embodiment. [Figure 14] FIG. 10 is a cross-sectional view showing a rotary shaft of a third modified example of the first embodiment. [Figure 15] FIG. 6 is a diagram showing the configuration of a rotating shaft according to a second embodiment of the present invention. [Figure 16] FIG. 16 is a cross-sectional view taken along line III-III shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] (First embodiment) 1 is a schematic diagram showing the configuration of a rotating shaft 1 according to a first embodiment of the present invention. In the drawings, the same parts are given the same reference numerals.

[0009] The rotating shaft 1 is a shaft that is rotated by a motor or the like. The rotating shaft 1 is equipped with a torque sensor 10 that detects the torque generated by the rotation of the rotating shaft 1 itself. For example, the rotating shaft 1 is the shaft that serves as the rotation axis of the tires of an electric vehicle. Note that the rotating shaft 1 is not limited to the automotive field and may be used in any industry, such as robotics.

[0010] The rotating shaft 1 includes a shaft body 30 and a torque sensor 10. Note that the rotating shaft 1 may be provided with a plurality of torque sensors 10.

[0011] The shaft body 30 has a circular cross section and an elongated cylindrical shape like a rod. The shaft body 30 may be a hollow cylindrical shape with a hollow center, or a solid cylindrical shape with a filled center (columnar shape).

[0012] The torque sensor 10 is attached to the shaft body 30. The torque sensor 10 detects the torque generated by the rotation of the shaft body 30. For example, the torque detected by the torque sensor 10 is transmitted as an electric signal to a control device that controls the rotation of the shaft body 30.

[0013] The torque sensor 10 according to this embodiment will be described with reference to Fig. 2 to Fig. 4. Fig. 2 is a plan view showing the configuration of the torque sensor 10. Fig. 3 is a cross-sectional view taken along line II-II shown in Fig. 2. Fig. 4 is a plan view showing the sensor main body 11.

[0014] The torque sensor 10 includes a sensor body 11 and a strain sensor 20 attached to the sensor body 11 .

[0015] For example, the sensor body 11 has an overall rectangular plate shape. For example, the sensor body 11 is made of a metal such as stainless steel. The sensor body 11 may be formed by punching a metal plate or may be manufactured by other methods.

[0016] The sensor body 11 includes a first attachment portion 11a, a second attachment portion 11b, a first support portion 11c, a second support portion 11d, a first beam 11e, and a second beam 11f.

[0017] The first mounting portion 11a and the second mounting portion 11b are portions that are attached to the shaft body 30 by screws 27 and 28, respectively. The first support portion 11c is provided so as to protrude from the first mounting portion 11a. The second support portion 11d is provided so as to protrude from the second mounting portion 11b. The first beam 11e and the second beam 11f are provided on both sides of the first support portion 11c and the second support portion 11d, between the first mounting portion 11a and the second mounting portion 11b.

[0018] The strain sensor 20 is disposed between the first support portion 11c and the second support portion 11d. The strain sensor 20 includes a flexure body 21 and a plurality of strain gauges 22 disposed on the surface of the flexure body 21. For example, the flexure body 21 is in the shape of a rectangular plate.

[0019] The mounting position of the torque sensor 10 on the shaft body 30 will be described with reference to FIG. The torque sensor 10 is attached to the outer surface of the shaft body 30. The torque sensor 10 is attached so that the longitudinal direction of the torque sensor 10 is aligned with the axis A (rotation axis or rotation center) about which the shaft body 30 rotates. Specifically, when the shaft body 30 is stationary (when no torque is applied), the first attachment portion 11a, first support portion 11c, strain element 21, second support portion 11d, and second attachment portion 11b, which are arranged in a straight line, of the torque sensor 10 are arranged along the axis A of the shaft body 30. In other words, the first support portion 11c, strain element 21, and second support portion 11d, which are arranged in series, are arranged parallel to the axis A of the shaft body 30.

[0020] In the torque sensor 10 arranged as described above, when torque is applied to the shaft body 30 in the direction of the arrow T in the figure, a twist occurs on the surface of the shaft body 30 in the same direction as the torque. That is, the shaft body 30 twists by an angle θ with respect to the axis A, causing a displacement Δ on the surface of the shaft body 30. As a result, the first support portion 11c of the torque sensor 10 is displaced in the direction of the arrow T relative to the second support portion 11d. This causes a distortion in the strain element 21, and this distortion is detected by the multiple strain gauges 22.

[0021] Two or more torque sensors 10 may be arranged symmetrically with respect to the shaft body 30. For example, the two torque sensors 10 may be arranged on opposite sides of the axis A (180° from the axis A). This makes it possible to eliminate components other than torque based on the detection values ​​of the two torque sensors 10 by utilizing the symmetry of the arrangement of the two torque sensors 10, and to more accurately determine the detection value of only the torque component.

[0022] An example of the shape of the sensor body 11 will be described with reference to FIG. The length Lc of the first support portion 11c and the length Ld of the second support portion 11d are equal (Lc=Ld), and the first support portion 11c and the second support portion 11d are spaced a predetermined distance apart. Therefore, the tip of the first support portion 11c and the tip of the second support portion 11d face each other at a predetermined distance in the longitudinal direction of the sensor body 11.

[0023] First slits 11g are provided between the first beam 11e and each of the first support portion 11c and the second support portion 11d. Second slits 11h are provided between the second beam 11f and each of the first support portion 11c and the second support portion 11d. Therefore, both longitudinal side surfaces of the first support portion 11c and both longitudinal side surfaces of the second support portion 11d are spaced apart from the first beam 11e and the second beam 11f.

[0024] The first beam 11e and the second beam 11f are provided to maintain a constant distance between the first support portion 11c and the second support portion 11d. Therefore, in order not to affect the torque detection sensitivity, it is preferable that the width of the first beam 11e and the second beam 11f (the length in the direction perpendicular to the longitudinal direction of the torque sensor 10) is as narrow as possible and the rigidity of the first beam 11e and the second beam 11f is as small as possible.

[0025] The widths of the first beam 11e and the second beam 11f are narrowed by providing the first slit 11g and the second slit 11h, respectively. Therefore, the rigidity of the first beam 11e and the second beam 11f is smaller than the rigidity of the strain body 21. Note that only one of the first beam 11e and the second beam 11f may be provided.

[0026] The first attachment portion 11a includes a plurality of holes 11i into which a plurality of screws 27 are inserted in a direction perpendicular to the longitudinal direction of the sensor main body 11. The second attachment portion 11b includes a plurality of holes 11j into which a plurality of screws 28 are inserted in a direction perpendicular to the longitudinal direction of the sensor main body 11.

[0027] The first support portion 11c includes a screw hole 11k into which the screw 24 is screwed. The second support portion 11d includes a screw hole 11l into which the screw 26 is screwed.

[0028] The configuration of the strain sensor 20 will be described with reference to FIGS. The flexure body 21 is made of a metal such as aluminum. However, the flexure body 21 may be made of a metal other than aluminum, or ceramic, etc. The four strain gauges 22 are arranged along the diagonal lines of the rectangular flexure body 21. The four strain gauges 22 form a bridge circuit. However, any number of strain gauges 22 may be provided, they may be arranged in any manner, and any type of electric circuit may be formed.

[0029] As shown in FIG. 3, the thickness Ta of the flexure element 21 (the length in the direction perpendicular to the plane of the flexure element 21) is thinner than the thickness Tb of the first support portion 11c and the second support portion 11d (the length in the direction perpendicular to the plane of the first support portion 11c and the second support portion 11d) (Ta <Tb)。

[0030] As shown in FIG. 2, the width Wa of the strain element 21 is narrower than the width Wb of the first support portion 11c and the second support portion 11d (Wa <Wb)。

[0031] The configuration of the strain gauge 22 will be described with reference to Fig. 5. The strain gauge 22 is not limited to the configuration described here, and may have any configuration.

[0032] The strain gauge 22 includes an elastic body 22a, an insulating film 22b, a thin-film resistor (strain-sensitive film) 22c, an adhesive film 22d, a thin-film wiring 22e, an adhesive film 22f, and a glass film 22g as a protective film. Specifically, the insulating film 22b is provided on the elastic body 22a, and the thin-film resistor 22c is provided on the insulating film 22b. For example, the thin-film resistor 22c is made of a Cr—N resistor. A thin-film wiring 22e serving as an electrode lead and made of a conductive material such as copper is provided on the end of the thin-film resistor 22c with an adhesive film 22d interposed therebetween. An adhesive film 22f is provided on the thin-film wiring 22e. The insulating film 22b, the thin-film resistor 22c, and the adhesive film 22f are covered with a glass film 22g. The adhesive film 22d improves adhesion between the thin-film wiring 22e and the thin-film resistor 22c. The adhesive film 22f improves adhesion between the thin-film wiring 22e and the glass film 22g. The elastic body 22a is made of a metal such as stainless steel or an aluminum alloy, or a silicon substrate, etc. The adhesive films 22d and 22f are films containing chromium (Cr) or the like.

[0033] A specific method for attaching the torque sensor 10 to the shaft body 30 will be described with reference to FIG.

[0034] A first end of the strain sensor 20 (flexure element 21) is disposed on the first support portion 11c. A second end of the strain sensor 20 is disposed on the second support portion 11d. The first end of the strain sensor 20 is fixed to the first support portion 11c by a first fixing member 23 and a screw 24 disposed on the first support portion 11c. The second end of the strain sensor 20 is fixed to the second support portion 11d by a second fixing member 25 and a screw 26 disposed on the second support portion 11d.

[0035] The first fixing member 23 contacts the upper surface of the first support portion 11c at the first protrusion 23a, and contacts the first end of the strain sensor 20 at the second protrusion 23b. The second protrusion 23b is shorter than the first protrusion 23a. A hole 23c is located between the first protrusion 23a and the second protrusion 23b of the first fixing member 23.

[0036] The screw 24 is inserted into the hole 23c and threaded into the screw hole 11k of the first support portion 11c, whereby the first protrusion 23a is fixed to the first support portion 11c and the second protrusion 23b is brought into line contact with the first end portion of the strain sensor 20. In this way, the first end portion of the strain sensor 20 is fixed to the first support portion 11c.

[0037] The configuration of the second fixing member 25 is similar to that of the first fixing member 23, and includes a third protrusion 25a that contacts the upper surface of the second support portion 11d, a fourth protrusion 25b that contacts the second end of the strain sensor 20 and is shorter in length than the third protrusion 25a, and a hole 25c located between the third protrusion 25a and the fourth protrusion 25b.

[0038] Screw 26 is inserted into hole 25c and threaded into screw hole 111 of second support portion 11d, thereby fixing third protrusion 25a to second support portion 11d and bringing fourth protrusion 25b into line contact with the second end portion of strain sensor 20. As a result, the second end portion of strain sensor 20 is fixed to second support portion 11d.

[0039] The torque sensor 10 having the above configuration is attached to the surface of the shaft body 30 by inserting screws 27 into each of a plurality of holes 11i provided in the first attachment portion 11a and by inserting screws 28 into each of a plurality of holes 11j provided in the second attachment portion 11b.

[0040] Therefore, the relationship between the length between the fixed portions of the flexure body 21 (the length between the second protrusion 23b and the third protrusion 25b, or the effective length of the flexure body 21) La and the length between the first mounting portion 11a and the second mounting portion 11b (the length between the center of the screw 27 and the center of the screw 28, or the effective length of the sensor main body 11) Lb is as follows: La <Lbである。

[0041] 1, the torque sensor 10 is attached to the outer surface (outer circumferential surface) of the shaft body 30, but the present invention is not limited to this and the torque sensor 10 may be attached to the inner surface (inner circumferential surface) of the shaft body 30. Specifically, in FIG. 3, the surface of the shaft body 30 on which the torque sensor 10 is provided may be the inner circumferential surface of the shaft body 30. FIG. 6 is a cross-sectional view of the torque sensor 10 provided on the inner circumferential surface of the shaft body 30, as viewed from the direction of the axis A. When the torque sensor 10 is provided on the inner circumferential surface of the shaft body 30, the wiring of the torque sensor 10 (for example, the wiring of the strain gauge 22) can be arranged in a cavity inside the cylinder of the shaft body 30, thereby making effective use of the internal space of the shaft body 30.

[0042] The operation of the torque sensor according to this embodiment will be described with reference to Figures 1 and 7. Figure 1 shows the positions of the shaft body 30 and the torque sensor 10 in a simplified manner.

[0043] The first support portion 11c, the strain element 21, and the second support portion 11d, which are arranged in series in the torque sensor 10, are arranged parallel to the axis A of the shaft main body 30.

[0044] Since the rigidity of the first support portion 11c and the second support portion 11d is sufficiently greater than the rigidity of the strain body 21, the displacement X1 of the first support portion 11c relative to the second support portion 11d is not greater than the displacement X2 of the first attachment portion 11a relative to the second attachment portion 11b. Specifically, the displacement of the first support portion 11c relative to the second support portion 11d and the displacement of the first attachment portion 11a relative to the second attachment portion 11b are substantially the same.

[0045] On the other hand, the effective length La of the flexure body 21 is sufficiently shorter than the effective length Lb of the sensor main body 11 (the length between the center of the screw 27 and the center of the screw 28). Therefore, the torsion angle θ1 of the flexure body 21 is larger than the torsion angle θ2 of the sensor main body 11. Therefore, the flexure body 21 deforms more than the sensor main body 11, and the amount of strain received by the flexure body 21 is larger than the amount of strain received by the sensor main body 11, resulting in amplified strain. Therefore, a large amplified signal is output from the multiple strain gauges 22 arranged on the flexure body 21.

[0046] Here, we will explain the rigidity of the first support portion 11c, the second support portion 11d, and the strain generator 21. One end of the first support portion 11c and one end of the second support portion 11d are connected to the first attachment portion 11a and the second attachment portion 11b, respectively. Therefore, the first support portion 11c and the second support portion 11d can be considered to be deformed cantilevers.

[0047] In the cantilever beam shown in FIG. 8, if the length of the beam is L and the displacement of the beam when a load P is applied to the free end of the beam is ymax, ymax is expressed by the following equation (1).

[0048] ymax = PL3 / 3EI …(1) where I: Moment of inertia E: Young's modulus Transforming equation (1) gives equation (2). P=3EIymax / L3 …(2) 3EI / L3 is like a spring constant, and can be thought of as equivalent to rigidity.

[0049] In this embodiment, the value of 3EI / L3 is set to be larger in the first support portion 11c and the second support portion 11d (sections of length Lc and length Ld (Lc=Ld)) than in the strain element 21 (section of effective length La).

[0050] Specifically, the value of 3EI / L3 can be found by substituting the Young's moduli of the flexure element 21, the first support portion 11c, and the second support portion 11d into E, and substituting the geometrical moment of inertia of the flexure element 21, the first support portion 11c, and the second support portion 11d into I (the geometrical moment of inertia in the direction perpendicular to the plane in the plan view shown in FIG. 2).

[0051] For example, if the cross section of the first support portion 11c and the second support portion 11d is rectangular, the thickness in the direction perpendicular to the plane is t, and the width in the direction perpendicular to the longitudinal direction is W, the second moment of area Is of the section of the lengths Lc and Ld of the first support portion 11c and the second support portion 11d is expressed by equation (3).

[0052] Is=tW3 / 12 …(3) Since the sections of lengths Lc and Ld of the first support portion 11c and the second support portion 11d are divided into two sections sandwiched between the strain body 21, the value equivalent to the rigidity is the sum of the rigidities of the sections of lengths Lc and Ld. Therefore, the rigidity of the section of lengths Lc and Ld is expressed by equation (4).

[0053] 2(3EI / L3) …(4) As described above, the configurations of the flexure body 21, the first support portion 11c, and the second support portion 11d can be defined. In this embodiment, the relationship between the rigidity of the flexure body 21 and the first support portion 11c and the second support portion 11d is such that the rigidity of the flexure body 21 is smaller than the rigidity of the first support portion 11c and the second support portion 11d (rigidity of the flexure body 21<rigidity of the first support portion 11c and the second support portion 11d).

[0054] Specifically, the sensor body 11, including the flexure element 21 and the first and second support portions 11c and 11d, is made of metal, such as stainless steel. The thickness Ta of the flexure element 21 is thinner than the thickness Tb of the first and second support portions 11c and 11d, and the width of the flexure element 21 is narrower than the width of the first and second support portions 11c and 11d.

[0055] The materials of the strain element 21 and the sensor main body 11 can be combined with other materials as long as the above-mentioned rigidity relationship is satisfied.

[0056] The strain body 21 is fixed to the first support part 11c and the second support part 11d using the first fixing member 23, the second fixing member 25, and the screws 24, 26, respectively, but this is not limitative and the strain body 21 may be fixed using an adhesive, welding, or the like.

[0057] The sensor body 11 is fixed to the shaft body 30 using a plurality of screws 27, 28, but this is not limitative and the sensor body 11 may be fixed using adhesive, welding, or the like.

[0058] (Linear expansion) In this embodiment, the first support portion 11c, the flexure body 21, and the second support portion 11d are arranged in series and are disposed on the shaft body 30. If the shaft body 30, the first support portion 11c, the flexure body 21, and the second support portion 11d are made of the same material, the coefficients of linear expansion with respect to temperature changes are the same, and therefore no tensile or compressive force is generated in the flexure body 21.

[0059] However, depending on the material of the flexure body 21, it may be difficult to form a film of the strain gauge 22 on the flexure body 21, and it may be difficult to form the flexure body 21, the shaft body 30, the first support portion 11c, and the second support portion 11d from the same material. If these materials are different, a tensile force or a compressive force will be generated in the flexure body 21 due to temperature changes, and the torque measurement accuracy will decrease.

[0060] Therefore, in this embodiment, the relationship between the linear expansion coefficients of the strain body 21, the first support portion 11c, the second support portion 11d, and the shaft body 30 is adjusted to be: strain body 21<shaft body 30<first support portion 11c, second support portion 11d.

[0061] Specifically, when the temperature changes by ΔT, if the sum of the linear expansion Lex1 of the shaft main body 30, the linear expansion Lex2 of the strain body 21 of the torque sensor 10, and the linear expansion Lex3 of the first support portion 11c and the second support portion 11d is equal (Lex1=Lex2+Lex3), no force is generated in the strain body 21.

[0062] where: Lex1=α2·Lb·ΔT Lex2=α1·La·ΔT Lex3=α3·(Lb-La)·ΔT La: Effective length of the strain body 21 Lb: length of the shaft body 30 between the first attachment portion 11a and the second attachment portion 11b (effective length of the shaft body 30) Then, Lex1=Lex2+Lex3 α2·Lb·ΔT=α1·La·ΔT+α3·(Lb-La)·ΔT Therefore, if the following formula (5) is satisfied, no force due to temperature change is generated in the strain element 21. La=Lb·(α2-α3) / (α1-α3) …(5) In this case, the relationship of the linear expansion coefficients is α1>α2>α3 or α1<α2<α3.

[0063] For example, the flexure element 21 may be made of stainless steel, the shaft body 30 may be made of aluminum alloy, and the first support portion 11c and the second support portion 11d may be made of zinc alloy. In this case, the linear expansion coefficient α2 of the aluminum alloy is larger than the linear expansion coefficient α1 of stainless steel (α1<α2) but smaller than the linear expansion coefficient α3 of the zinc alloy (α2<α3). Therefore, the first support portion 11c and the second support portion 11d, which have a large linear expansion coefficient, and the flexure element 21, which has a small linear expansion coefficient, can bring the overall linear expansion of the flexure element 21, the first support portion 11c, and the second support portion 11d closer to the linear expansion of the shaft body 30. This improves the accuracy of torque measurement in response to temperature changes.

[0064] (Effects of the embodiment) According to the rotating shaft 1 of this embodiment, a strain generator 21 including a plurality of strain gauges 22 is joined between the first support portion 11c and the second support portion 11d of the sensor main body 11, and torsion of the shaft main body 30 is detected by converting it into displacement between the first support portion 11c and the second support portion 11d, and into displacement of the strain generator 21. In other words, the displacement of the first support portion 11c and the second support portion 11d has the effect of magnifying the amount of torsion of the shaft main body 30. This allows the plurality of strain gauges 22 provided on the strain generator 21 to output a large signal. This allows for improved torque measurement accuracy compared to when a plurality of strain gauges are provided directly on the surface (outer or inner peripheral surface) of the shaft main body 30 to detect slight strain.

[0065] Furthermore, first slits 11g are provided between the first beam 11e and the first support portion 11c and the second support portion 11d, and second slits 11h are provided between the second beam 11f and the first support portion 11c and the second support portion 11d. This allows the rigidity of the first beam 11e and the second beam 11f to be smaller than the rigidity of the strain body 21, thereby increasing the displacement of the first mounting portion 11a and the second mounting portion 11b. This also increases the displacement of the strain body 21 between the first support portion 11c and the second support portion 11d, allowing larger signals to be output from the multiple strain gauges 22 and improving the torque measurement accuracy.

[0066] Furthermore, the relationship between the linear expansion coefficient α1 of the strain body 21, the linear expansion coefficient α3 of the first support portion 11c and the second support portion 11d, and the linear expansion coefficient α2 of the shaft body 30 satisfies α1>α2>α3 or α1<α2<α3, so that no force due to temperature changes is generated in the strain body 21. This improves the measurement accuracy of torque relative to temperature changes.

[0067] (Variation) FIG. 9 shows a sensor body 11 according to a first modified example of this embodiment. The basic sensor body 11 shown in FIG. 4 includes a first beam 11e, a second beam 11f, a first slit 11g, and a second slit 11h between a first mounting portion 11a and a second mounting portion 11b.

[0068] In contrast, the sensor body 11 of the first modified example does not include the first beam 11e, the second beam 11f, the first slit 11g, and the second slit 11h, but includes an opening 11m between the first support portion 11c and the second support portion 11d.

[0069] In the first variant, the rigidity of the sensor body 11 and the first support portion 11c and second support portion 11d is higher than that of the basic form, so that the displacement of the first support portion 11c and the second support portion 11d in response to twisting of the shaft body 30 is smaller than that of the basic form, but an effect almost the same as that of the basic form can be obtained.

[0070] FIG. 10 shows a sensor body 11 according to a second modification of this embodiment. The sensor main body 11 of the second modified example is separated into a first main body 111 and a second main body 112.

[0071] In the second modified example, because the first body 111 and the second body 112 are separated, the first body 111 and the first support portion 11c are displaced in the same manner, and the second body 112 and the second support portion 11d are displaced in the same manner in response to a twist of the shaft body 30. As a result, the strain element 21 joined between the first support portion 11c and the second support portion 11d undergoes a larger displacement than in the basic form. Therefore, the multiple strain gauges 22 can output a larger signal than in the basic form, improving the torque measurement accuracy.

[0072] In the case of the second modified example, it is necessary to keep the distance between the first body 111 and the second body 112 constant.

[0073] FIG. 11 shows a first mounting configuration of a torque sensor 10 according to a second modified example of this embodiment. In FIG. 11, the shaft body 30 has a first protrusion 30a as a first engagement portion and a second protrusion 30b as a second engagement portion on its surface. The first protrusion 30a and the second protrusion 30b are arranged at a predetermined interval along the axial direction A of the shaft body 30 and define the distance between the first body 111 and the second body 112. That is, the side surface of the first body 111 facing the first mounting portion 11a is arranged in contact with the first protrusion 30a, and the side surface of the second body 112 facing the second mounting portion 11b is arranged in contact with the second protrusion 30b. The other configurations are the same as those of the basic mounting configuration.

[0074] In this way, by providing the first protrusion 30a and the second protrusion 30b on the surface of the shaft body 30, the separated first body 111 and second body 112 can be positioned a predetermined distance apart, thereby improving the dimensional accuracy between the first body 111 and the second body 112.

[0075] 12 shows a second mounting configuration of the torque sensor 10 according to the second modified example of this embodiment. In FIG. 12, the shaft body 30 has a recess 31c on the surface and a cover 31d that covers the recess 31c.

[0076] The longitudinal direction of the recess 31c is arranged along the axis A of the shaft body 30, and the length Le of the recess 31c in the longitudinal direction defines the distance between the first body 111 and the second body 112. The side surface of the first body 111 on the side of the first mounting portion 11a is arranged in contact with the side surface (first engagement portion) on one side of the longitudinal direction of the recess 31c, and the side surface of the second body 112 on the side of the second mounting portion 11b is arranged in contact with the side surface (second engagement portion) on the other side of the longitudinal direction of the recess 31c. The other configurations are the same as the mounting configuration of the basic type.

[0077] In this way, by providing a recess 31c on the surface of the shaft body 30, the separated first body 111 and second body 112 can be positioned a predetermined distance apart, thereby improving the dimensional accuracy between the first body 111 and the second body 112.

[0078] Furthermore, the recess 31c displaces in response to applied torque in the same manner as the surface of the shaft body 30, so that torque can be measured in the same manner as with the basic shape.

[0079] In the second mounting configuration, a torque sensor 10 having a sensor body 11 of the second modified example shown in Figure 10 is placed in the recess 31c, but this is not limited to this, and it is also possible to place a torque sensor having a sensor body 11 of the basic type or the first modified example.

[0080] 13 and 14 show a rotating shaft 1 according to a third modified example of the present embodiment. Fig. 13 is a perspective view showing the rotating shaft 1. Fig. 14 is a cross-sectional view of the rotating shaft 1 shown in Fig. 13 taken along a plane that is parallel to and passes through axis A, so as to cut the rotating shaft 1 together with the strain sensor 20 in the longitudinal direction.

[0081] The sensor main body 11 of the third modified example is composed of a first main body 111a and a second main body 112a. The first main body 111a and the second main body 112a correspond to the first main body 111 and the second main body 112, respectively, of the sensor main body 11 of the second modified example shown in FIG.

[0082] As in the second modified example, the first body 111a and the second body 112a are arranged at a predetermined distance from each other, and the strain sensor 20 is arranged to straddle the first body 111a and the second body 112a at a predetermined distance from each other.

[0083] The sensor body 11 is formed as a whole in a ring shape that covers the entire outer circumferential surface of the shaft body 30. That is, the sensor body 11 is formed so as to wrap around the shaft body 30 around the axis A. The surface of the sensor body 11 on which the strain sensor 20 is provided is plate-shaped, and a cavity is formed between the sensor body 11 and the shaft body 30.

[0084] The end portions of the surfaces of the first body 111a and the second body 112a are bent perpendicularly toward the shaft body 30. As a result, the end portions of the surfaces of the first body 111a and the second body 112a are fixed to the outer circumferential surface of the shaft body 30. The first body 111a and the second body 112a may be fixed to the outer circumferential surface of the shaft body 30 by any method, such as screws, adhesive, or welding.

[0085] Even when the third modification is adopted, it is possible to obtain substantially the same effect as the second modification. Furthermore, if the distance between both ends of the sensor main body 11 (the end of the first main body 111a and the end of the second main body 112a) is Lb and the distance between the first main body 111a and the second main body 112a is La, the amplification factor of the strain detected by the strain sensor 20 is Lb / La.

[0086] (Second embodiment) Fig. 15 is a diagram showing the configuration of a rotating shaft 1A according to a second embodiment of the present invention. Fig. 16 is a cross-sectional view taken along line III-III shown in Fig. 15. Note that in Fig. 15, in order to make the attachment state easier to understand, the cross section is the same as in Fig. 3 except for the fixing member 40.

[0087] In the rotating shaft 1 of the first embodiment, the sensor body 11 was fixed to the shaft body 30 by screws 27 and 28, but in the rotating shaft 1A of this embodiment, the sensor body 11A is fixed to the shaft body 30 by two fixing members 40.

[0088] The sensor body 11A according to this embodiment is similar to the sensor body 11 according to the first embodiment, except that the holes 11i and 11j into which the screws 27 and 28 are inserted are removed, and a linearly extending protrusion 11Aa that is parallel to the axis A (longitudinal direction of the shaft body 30) and makes line contact with the shaft body 30 is provided on the back surface of the sensor body 11 (the contact surface with the shaft body 30). Here, the sensor body 11 according to the first embodiment, which is the base of the sensor body 11A according to this embodiment, may be any of the basic form, the first modified form, or the second modified form. The protrusion 11Aa may be modified to any shape or may not be present.

[0089] The fixing member 40 includes an upper frame 41, a lower frame 42, and two screws 43. The upper frame 41 and the lower frame 42 are semi-cylindrical, formed by dividing a cylinder into two halves in the axial direction. The inner circumferential surfaces of the upper frame 41 and the lower frame 42 are curved so that when the upper frame 41 and the lower frame 42 are fitted together with a small gap between them, a cylindrical space is formed inside to accommodate the shaft main body 30. A rectangular recess 41a is formed in each inner circumferential surface of the upper frame 41 and the lower frame 42, into which the first mounting portion 11a or the second mounting portion 11b of the sensor main body 11A is fitted. Protrusions 41b and 42b, which protrude in the shape of rectangular plates, are formed on both circumferential ends of the upper frame 41 and the lower frame 42, respectively. Threaded holes into which screws 43 are threaded are formed in the protrusions 41b and 42b.

[0090] 15 and 16, a method for attaching the torque sensor 10 to the shaft body 30 using the fixing member 40 will be described. Here, a method for attaching two torque sensors 10 to the shaft body 30 will be described, but any number of torque sensors 10 greater than or equal to one may be attached to the shaft body 30.

[0091] Two torque sensors 10 are arranged at attachment positions on the outer circumferential surface of the shaft body 30. For example, the two torque sensors 10 are arranged at positions 180° apart from the axis A of the shaft body 30. In other words, the two torque sensors 10 are arranged so that they are directly opposite each other. When arranging multiple torque sensors 10, arranging them at equal intervals on the outer circumferential surface of the shaft body 30 makes it easier to eliminate forces other than those being measured and to determine only the torque of the object being measured. However, the torque sensors 10 may be arranged in any manner.

[0092] After placing the two torque sensors 10 in predetermined positions, the shaft body 30 is sandwiched from above and below between the upper frame 41 and the lower frame 42 together with the first mounting portion 11a or the second mounting portion 11b of each sensor body 11A of the two torque sensors 10, thereby fixing the two sensor bodies 11A to the shaft body 30.

[0093] The first attachment portion 11a located at one longitudinal end of each of the two sensor bodies 11A is fixed with one fixing member 40, and the second attachment portion 11b located at the other longitudinal end of each of the two sensor bodies 11A is fixed with another fixing member 40. By threading screws 43 into screw holes provided in the protrusions 41b, 42b of the upper frame 41 and lower frame 42 of each of the two fixing members 40, the upper frame 41 and the lower frame 42 are fixed so that the shaft body 30 and the two sensor bodies 11A are maintained in contact with each other. The sensor bodies 11A are fixed in line contact with the outer circumferential surface of the shaft body 30 parallel to the axis A by protrusions 11Aa provided on the back surface of each of the sensor bodies 11A.

[0094] According to this embodiment, in addition to the same effects as those of the first embodiment, the following effects can be obtained.

[0095] By using the fixing member 40 to fix the torque sensor 10 to the shaft body 30, it is not necessary to perform processing (for example, forming a screw hole) to fix the torque sensor 10 to the shaft body 30.

[0096] The sensor main body 11A and the shaft main body 30 are not joined by welding or screwing, but are fixed in a contacting state, so that the sensor main body 11A is less likely to be deformed by longitudinal deformation of the shaft main body 30. This reduces the influence of longitudinal deformation of the shaft main body 30 (deformation unrelated to torque), and improves the measurement accuracy of the torque of the measurement object.

[0097] By providing protrusions 11Aa on sensor main body 11A and fixing sensor main body 11A and shaft main body 30 in a line contact state, the influence of deformation of shaft main body 30 due to temperature changes on torque measurement accuracy can be reduced. Specifically, by bringing the outer peripheral surfaces of sensor main body 11A and shaft main body 30 into line contact in the longitudinal direction (direction parallel to axis A), the coefficient of friction between sensor main body 11A and shaft main body 30 in the longitudinal direction is low, and the coefficient of friction between sensor main body 11A and shaft main body 30 in the longitudinal direction and perpendicular directions is high. As a result, sensor main body 11A is less likely to deform when the shaft main body 30 is deformed in the longitudinal direction (deformation unrelated to torque), but is more likely to deform when the shaft main body 30 is deformed in the longitudinal direction and perpendicular directions (deformation related to torque). Therefore, the influence of deformation in the longitudinal direction of shaft main body 30 due to forces unrelated to torque can be reduced, making it easier to measure the torque of the object to be measured.

[0098] Even if the sensor main body 11A is not provided with the protrusions 11Aa, line contact can be achieved by bringing the planar back surface of the sensor main body 11A into contact with the outer circumferential surface of the shaft main body 30. Therefore, similar to the case where the protrusions 11Aa are provided, the effect of reducing the influence of deformation in the longitudinal direction of the shaft main body 30 can be obtained.

[0099] In each embodiment, a configuration in which a torque sensor that detects only torque is provided has been described, but each embodiment is not limited to a torque sensor that detects only torque. For example, a configuration in which a torque sensor (e.g., a force sensor) that measures torque and forces in directions other than torque is provided may also be used.

[0100] Furthermore, the present invention is not limited to the above-described embodiments, and in the implementation stage, the components can be modified and embodied without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in the above-described embodiments. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0101] 1...rotating shaft, 10...torque sensor, 11...sensor body, 11c...first support portion, 11d...second support portion, 20...strain sensor, 21...flexure element, 30...shaft body.

Claims

1. a rotating shaft body having a cylindrical outer shape; a torque sensor for detecting torque generated in the shaft body, The torque sensor is a first attachment portion attached to a surface of the shaft body; a second attachment portion attached to the surface of the shaft body; a first support portion provided on the first mounting portion; a second support portion provided on the second mounting portion and arranged to face the first support portion at a distance; a strain generating body having a first end attached to the first support portion, a second end attached to the second support portion, and a plurality of strain gauges disposed on a surface thereof; the first support portion, the strain element, and the second support portion are arranged along a rotation axis of the shaft body, When the linear expansion coefficient of the strain body is α1, the linear expansion coefficient of the shaft main body is α2, and the linear expansion coefficients of the first support portion and the second support portion are α3, α1>α2>α3, or α1<α2<α3; a rotating shaft including

2. When the effective length of the strain element is La and the effective length of the shaft body is Lb, La=Lb・(α2-α3) / (α1-α3) To satisfy The rotating shaft of claim 1 , comprising:

3. At least one beam connecting the first mounting portion and the second mounting portion; At least one slit is provided between the at least one beam and the first support portion and between the at least one beam and the second support portion, a width of the at least one beam is smaller than a width of the first support portion and the second support portion; The rotating shaft of claim 1 , comprising:

4. the surface of the shaft body is an outer circumferential surface of the shaft body; The rotating shaft of claim 1 , comprising:

5. the surface of the shaft body is an inner circumferential surface of the shaft body; The rotating shaft of claim 1 , comprising:

6. a first fixing member that fixes the first support portion and the surface of the shaft body in contact with each other and accommodates the first attachment portion and the shaft body therein; a second fixing member that fixes the second support portion and the surface of the shaft body in contact with each other and accommodates the second attachment portion and the shaft body therein; The rotating shaft of claim 4, comprising:

7. the first support portion and the surface of the shaft body are fixed in a line contact state, the second support portion and the surface of the shaft body are fixed in a line contact state; The rotating shaft of claim 6 , comprising:

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