Wave gear device equipped with torque detection device

Abstract

A strain gauge-type torque detection unit (20) of a strain wave gear (1) is provided with a first torque detection unit (20A) and a second torque detection unit (20B) that output two independent series of detection signals. The first and second torque detection units (20A, 20B) are each provided with a plurality of sets of strain gauges (11) affixed to a diaphragm (3c) of an external gear (3) at a prescribed angular interval around the center axis. A composite signal (23C) is generated by combining, after gain adjustment is performed, a first detection signal (22A) from the first torque detection unit (20A) and a second detection signal (22B) from the second torque detection unit (20B). Transmission torque can be calculated on the basis of the first detection signal (23A), the second detection signal (23B), and the composite signal (23C). From a torque detection device (10), three series of outputs resulting from adding a high-accuracy output (24C) to two independent series of detection outputs (24A, 24B) are acquired.

Description

[Technical Field]

[0001] The present invention relates to a strain gauge type torque detector that detects torque transmitted via a flexible external gear. [Background technology]

[0002] Wave gearing devices equipped with strain gauge-type torque detectors have been proposed in Patent Documents 1 to 3. To accurately detect torque in a wave gearing device, it is necessary to remove rotational ripple, which is a periodic error component contained in the strain gauge output signal that occurs regardless of the transmitted torque, and to improve the linearity of the detection output. For this reason, multiple sets of strain gauges are used to compensate for elliptical distortion, which is a periodic error component contained in the detection output due to the rotation of the wave generator.

[0003] In Patent Document 1, two sets of torque detection means, each consisting of a pair of strain gauges arranged at 90° intervals on the surface of the external gear, are arranged at positions rotated by an angle of k × 45° (k is an odd number) around the central axis of the external gear, and the transmitted torque is calculated based on the combined output of the detection outputs of these two sets of torque detection means. Patent Document 2 proposes a method of adjusting the gain of the output of each detection element to remove periodic errors contained in the detection output obtained by combining the outputs of multiple detection elements. Patent Document 3 proposes a method in which, when the order of the rotational ripple component to be compensated is N (N: positive integer), at least (2N + 1) strain gauges are attached to the external gear, and the outputs are gain-adjusted by an amplifier and then combined to generate a detection signal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3644558 [Patent Document 2] Patent No. 4569990 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-45378 Summary of the Invention [Problem to be solved by the invention]

[0005] When torque sensors are installed in collaborative robots and other devices for safety reasons, it is desirable to have redundant or dual-system sensors to ensure safety even in the unlikely event that a sensor fails.

[0006] The object of the present invention is to provide a strain gauge type torque detector that is duplicated by arranging multiple sets of strain gauges in a way that makes it possible to obtain a triple output system by adding a high-precision output to two independent systems of detection output. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a strain wave gear device equipped with a torque detection device that detects transmission torque transmitted via a flexible external gear, The torque detection device is a first torque detection unit and a second torque detection unit that output two independent systems of detection signals; an output combining unit that combines a first detection signal that is the detection signal of the first torque detection unit and a second detection signal that is the detection signal of the second torque detection unit to generate a combined signal; a calculation unit capable of calculating the transmission torque based on each of the first detection signal, the second detection signal, and the composite signal; It is equipped with the first torque detection unit is a strain gauge type torque detection unit including a first group of strain gauges attached to a surface of the external gear at predetermined angular intervals centered on the central axis of the external gear, The second torque detection unit is characterized in that it is a strain gauge type torque detection unit having a second group of strain gauges attached to the surface of the external gear at a predetermined angular interval centered on the central axis of the external gear.

[0008] The external gear of the strain wave gearing device is bent into an elliptical shape by a wave generator, and meshes with a rigid internal gear at the location of the major axis of the ellipse. The detection signals of the strain gauges contain periodic error components, including an elliptical distortion component with a 180° period and error components with periods that are integer multiples of 180°. In this case, for example, multiple strain gauges arranged at angular intervals of 45° or 60° around the central axis of the external gear are divided into two groups, and independent detection signals are obtained from each group of strain gauges. Furthermore, the two independent detection signals obtained from the two groups of strain gauges are combined to remove rotational ripple and obtain a highly accurate output with improved linearity. [Effects of the Invention]

[0009] According to the present invention, in order to remove periodic error components, multiple sets of strain gauges arranged around the central axis of the external gear are divided into two groups, allowing two independent detection signals to be obtained. Furthermore, the detection signals from the two systems are combined to obtain a three-system output, including a high-precision output from which periodic error components have been removed. This allows for highly accurate detection of transmitted torque, providing a torque detection device that can guarantee safety even if one of the detection sections fails. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an explanatory diagram showing a strain wave gear device equipped with a torque detector to which the present invention is applied; [Figure 2] 1A is a schematic longitudinal sectional view of an external gear, and FIG. 1B is a schematic end view of the external gear. [Figure 3] FIG. 1A is an explanatory diagram showing eight sets of strain gauges that make up a torque detection unit, and FIG. 1B is an explanatory diagram showing a Wheatstone bridge circuit made up of eight sets of strain gauges. [Figure 4] (A) is an explanatory diagram showing four sets of strain gauges that make up the first torque detection unit, (B) is an explanatory diagram showing a first Wheatstone bridge circuit, (C) is an explanatory diagram showing four sets of strain gauges that make up the second torque detection unit, and (D) is an explanatory diagram showing a second Wheatstone bridge circuit. [Figure 5] (A) is an explanatory diagram showing four sets of strain gauges that make up the first torque detection unit, (B) is an explanatory diagram showing a first Wheatstone bridge circuit, (C) is an explanatory diagram showing four sets of strain gauges that make up the second torque detection unit, and (D) is an explanatory diagram showing a second Wheatstone bridge circuit. [Figure 6] (A) is an explanatory diagram showing four sets of strain gauges that make up the first torque detection unit, (B) is an explanatory diagram showing a first Wheatstone bridge circuit, (C) is an explanatory diagram showing four sets of strain gauges that make up the second torque detection unit, and (D) is an explanatory diagram showing a second Wheatstone bridge circuit. [Figure 7] FIG. 3 is an explanatory diagram showing six sets of strain gauges that make up a torque detection unit. [Figure 8] (A) is an explanatory diagram showing three sets of strain gauges that make up the first torque detection unit, (B) is an explanatory diagram showing the first bridge circuit, (C) is an explanatory diagram showing three sets of strain gauges that make up the second torque detection unit, and (D) is an explanatory diagram showing the second bridge circuit. [Figure 9] FIG. 2(A) is an explanatory diagram showing three sets of strain gauges that make up the first torque detection unit, and FIG. 2(B) is an explanatory diagram showing three sets of strain gauges that make up the second torque detection unit. [Figure 10] (A) is an explanatory diagram showing six sets of strain gauges that make up the torque detection unit, (B) is an explanatory diagram showing three sets of strain gauges that make up the first torque detection unit, and (C) is an explanatory diagram showing three sets of strain gauges that make up the second torque detection unit. [Figure 11] 10(A) is a graph showing the measurement results of the rotational ripple (%) contained in the torque detection output relative to the input rotation angle obtained from the first torque detection unit shown in FIG. 10(B), and FIG. 10(B) is a graph showing the simulation results of the rotational ripple contained in the torque detection output (synthetic signal) obtained from the torque detection unit configured as shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Overall composition) Fig. 1 is a schematic longitudinal sectional view showing a strain wave gear device to which the present invention is applied. Fig. 2(A) is a longitudinal sectional view showing an external gear, and Fig. 2(B) is an end view of the external gear to which a torque detector is attached. The strain wave gearing 1 includes a rigid internal gear 2, a flexible external gear 3 coaxially arranged inside the rigid internal gear 2, a wave generator 4 with an elliptical contour fitted coaxially inside the flexible external gear 3, a cross roller bearing 5 that supports the internal gear 2 and the external gear 3 in a state where they can rotate freely relative to each other, a hollow input shaft 6, an end plate 7 arranged on one side in the axial direction, and an end plate 8 arranged on the other side in the axial direction. Both shaft ends of the hollow input shaft 6 are supported by the end plates 7 and 8 via ball bearings 9a and 9b, respectively.

[0012] The external gear 3 is top-hat shaped and includes a cylindrical body 3b on which external teeth 3a are formed, a diaphragm 3c that continues from one end of the cylindrical body 3b and extends radially outward, and an annular boss 3d formed on the outer periphery of the diaphragm 3c. The cylindrical body 3b is bent into an elliptical shape by the wave generator 4, and the external teeth 3a partially mesh with the internal teeth 2a of the internal gear 2. The wave generator 4 includes a cam plate 4a of a constant width that is formed integrally with the hollow input shaft 6, and a wave bearing 4b that is fitted onto the elliptical outer periphery of the cam plate 4a.

[0013] When the wave generator 4 rotates in conjunction with the rotation of the hollow input shaft 6, the meshing positions of the gears 2, 3 move circumferentially, causing relative rotation between the two gears according to the difference in the number of teeth between them. The internal gear 2 is sandwiched between the inner ring 5a of the cross roller bearing 5 and an end plate 7, and these three members are fastened and fixed coaxially in this state. The boss 3d of the external gear 3 is sandwiched between the outer ring 5b of the cross roller bearing 5 and the other end plate 8, and these three members are fastened and fixed coaxially in this state. For example, if the internal gear 2 is fixed so as not to rotate, the external gear 3 will rotate, and reduced rotation will be output to a load member (not shown) via the end plate 8, which functions as an output shaft.

[0014] (torque detection device) The strain wave gearing 1 is provided with a torque detector 10 that detects the torque transmitted via the external gear 3. The torque detector 10 includes a torque detector 20 attached to the external gear 3, a signal processing unit 30 located outside the strain wave gearing 1, and a cable 40 connecting the torque detector 20 and the signal processing unit 30. The torque detector 20 includes multiple sets of strain gauges 11 attached to the diaphragm 3c of the external gear 3 and a flexible printed wiring board 12. In this example, as shown in FIG. 2(B), eight sets of strain gauges are arranged at equal angular intervals of 45° around the central axis of the external gear 3. The strain gauges 11 are protected by a coating layer 13, as shown by the shaded areas in FIG. 2(A). The strain gauges 11 are also connected to each other by a wiring pattern (not shown) formed on the flexible printed wiring board 12.

[0015] 3(A) is an explanatory diagram showing the arrangement of eight sets of strain gauges 11 attached to the diaphragm 3c of the external gear 3. Each strain gauge 11 is of the orthogonal two-axis type and is arranged at equal angular intervals of 45° around the central axis of the external gear 3. Below, the strain gauges 11 will be described clockwise as strain gauges 11(A1, A2), 11(B1, B2), 11(C1, C2), 11(D1, D2), 11(E1, E2), 11(F1, F2), 11(G1, G2), and 11(H1, H2).

[0016] (torque detection section) As shown in FIG. 4, the torque detection section 20 of this example is divided into a first torque detection section 20A and a second torque detection section 20B that output two independent systems of detection signals. As shown in Fig. 4(A), the first torque detection section 20A of the torque detection unit 20 includes four sets of strain gauges 11 (A1, A2), 11 (C1, C2), 11 (E1, E2), and 11 (G1, G2) arranged at 90° intervals, and as shown in Fig. 4(B), these four sets of strain gauges form a first Wheatstone bridge circuit 21A. Similarly, as shown in Fig. 4(C), the second torque detection section 20B includes the remaining four sets of strain gauges 11 (B1, B2), 11 (D1, D2), 11 (F1, F2), and 11 (H1, H2) arranged at 90° intervals, and as shown in Fig. 4(D), these sets form a second Wheatstone bridge circuit 21B. A first detection signal 22A, which is an output signal of the first Wheatstone bridge circuit 21A constituting the first torque detection section 20A, and a second detection signal 22B, which is an output signal of the second Wheatstone bridge circuit 21B constituting the second torque detection section 20B, are supplied to the signal processing unit 30 via cable wiring 40.

[0017] The signal processing unit 30 Figure 1 As shown in the figure, the signal processing unit 30 includes a first amplifier 31A that adjusts the gain of the first detection signal 22A, a second amplifier 31B that adjusts the gain of the second detection signal 22B independently of the first amplifier 31A, and an output combiner 31C that combines the gain-adjusted first detection signal 23A and second detection signal 23B to generate a combined signal 23C. The signal processing unit 30 also includes a calculator 32 that calculates a transmission torque based on the gain-adjusted first detection signal 23A, the gain-adjusted second detection signal 23B, and the combined signal 23C, and an output port 33. A first detected torque signal 24A, a second detected torque signal 24B, and a combined torque signal 24C (high-precision detection signal) that represent the transmission torque calculated based on the first detection signal 23A, the second detection signal 23B, and the combined signal 23C, respectively, are output from the output port 33 to a higher-level controller (not shown) or the like. It is also conceivable that first detection signal 23A, second detection signal 23B and composite signal 23C are output from output port 33, and the transmission torque value is calculated on the upstream side, or the composite signal 23C is generated on the upstream side.

[0018] The composite signal 23C obtained by adding the first detection signal 23A and the second detection signal 23B of two independent systems is equivalent to the output of a Wheatstone bridge circuit consisting of eight sets of strain gauges shown in Figure 3(B), and is a high-precision detection output with rotational ripple error removed and improved linearity.

[0019] In this way, in the torque detection device 10 of this example, a torque detection mechanism is constructed that can obtain two independent systems of detection signals using eight sets of strain gauges 11 arranged around the central axis of the external gear 3 in order to remove periodic error components. Even if one sensor system fails, the other can continue to detect the transmitted torque, ensuring safety. Furthermore, by combining the detection signals from the two systems, the detection output from which periodic error components have been removed can be used to perform accurate torque detection.

[0020] The high-precision signal (composite signal 23C) can also be obtained by adding the two-system output (first detection signal 23A, second detection signal 23B) on the user side. Furthermore, if the output signals (23A, 23B) are digitally converted and serially output in the amplifier of the signal processing unit 30, the high-precision signal (composite signal 23C) can be combined with the two-system signals (23A, 23B) and output. For example, if the low-precision two-system signal is 12 bits and the high-precision signal is 12 bits, they can be transmitted as the upper (first and second detection signals 23A, 23B) and lower (composite signal 23C) of a 24-bit serial signal.

[0021] 5 and 6 show another example of two systems of the torque detection unit 20 when strain gauges are arranged at eight locations at 45°. In the example of Fig. 5, the torque detection unit is divided into a first torque detection unit 20A(1) having a first Wheatstone bridge circuit 21A(1) made up of four sets of strain gauges 11 (A1, A2) to 11 (D1, D2) as shown in Fig. 5(A) and (B), and a second torque detection unit 20B(1) having a second Wheatstone bridge circuit 21B(1) made up of the remaining four sets of strain gauges 11 (E1, E2) to 11 (H1, H2) as shown in Fig. 5(C) and (D).

[0022] In the example of Figure 6, the torque detection unit is divided into a first torque detection unit 20A(2) having a first Wheatstone bridge circuit 21A(2) consisting of four sets of strain gauges 11(A1, A2), 11(C1, C2), 11(F1, F2), and 11(H1, H2) as shown in Figures 6(A) and (B), and a second torque detection unit 20B(2) having a second Wheatstone bridge circuit 21B(2) consisting of the remaining four sets of strain gauges 11(B1, B2), 11(D1, D2), 11(E1, E2), and 11(G1, G2) as shown in Figures 6(C) and (D).

[0023] (Another example of a torque detector) Figure 7 shows another example of the torque detection unit 20. The torque detection unit 20 (3) shown in this figure is configured with six sets of strain gauges 11 (A1, A2) to 11 (F1, F2) attached to the diaphragm of the external gear at equal angular intervals of 60° around the central axis (six strain gauges arranged at 60° intervals).

[0024] In this case, an example in which the torque detection unit 20(3) is divided into two independent systems (a first torque detection unit 20A and a second torque detection unit 20B) is shown in FIGS. 8 is divided into a first torque detection section 20A(3) having a first bridge circuit 21A(3) made up of three sets of strain gauges 11 (A1, A2) to 11 (C1, C2), and a second torque detection section 20B(3) having a second bridge circuit 21B(3) made up of the remaining three sets of strain gauges 11 (D1, D2) to 11 (F1, F2). Torque detection is performed based on the detection outputs from the three sets of strain gauges 11 making up the first bridge circuit 21A(3) and the detection outputs from the three sets of strain gauges 11 making up the second bridge circuit 21B(3).

[0025] In this case, the detection outputs (OUT1-OUT3) from the three sets of strain gauges 11 constituting the first bridge circuit 21A(3) are amplified by an amplifier for gain adjustment (not shown) and then combined to generate a first detection signal. Similarly, the detection outputs (OUT4-OUT6) from the three sets of strain gauges 11 constituting the second bridge circuit 21B(3) are amplified by an amplifier for gain adjustment (not shown) and then combined to generate a second detection signal. Furthermore, the first detection signal and the second detection signal are combined to generate a combined signal. The transmission torque is calculated based on each of the first detection signal, the second detection signal, and the combined signal.

[0026] FIG. 9 shows another example of a two-system torque detection unit 20(3) in the case of a 60° arrangement of six strain gauges (see FIG. 7). In the example of FIG. 9, the torque detection unit is divided into a first torque detection unit 20A(4) having a first bridge circuit (not shown) composed of three sets of strain gauges 11(A1, A2), 11(C1, C2), and 11(E1, E2), and a second torque detection unit 20B(4) having a second bridge circuit (not shown) composed of the remaining three sets of strain gauges 11(B1, B2), 11(D1, D2), and 11(F1, F2). In this case, as in the example of FIG. 8, three systems of output are obtained. The transmission torque can be calculated based on each of the three systems of output.

[0027] (Yet another example of a torque detector) FIG. 10(A) shows another example of a torque detection unit 20 having two independent systems of first and second torque detection units. The torque detection unit 20(5) shown in this figure has six sets of strain gauges 11(A1, A2) to 11(F1, F2) attached to the diaphragm of an external gear. As shown in FIG. 10(B), the three sets of strain gauges 11(A1, A2), 11(C1, C2), and 11(E1, E2) that make up the first torque detection unit 20A(5) are attached at equal angular intervals of 120° around the central axis of the diaphragm. As shown in FIG. 10(C), the remaining three sets of strain gauges 11(B1, B2), 11(D1, D2), and 11(F1, F2) that make up the second torque detection unit 20B(5) are also attached at equal angular intervals of 120° around the central axis of the diaphragm. Furthermore, three sets of strain gauges 11 (A1, A2), 11 (C1, C2) and 11 (E1, E2) are arranged at angular intervals of 120°, and three sets of strain gauges 11 (B1, B2), 11 (D1, D2) and 11 (F1, F2) are positioned at angular positions rotated 30° relative to each other.

[0028] In this case, a first detection signal 22A, which is the output of a first bridge circuit composed of three sets of strain gauges 11 (A1, A2), 11 (C1, C2), and 11 (E1, E2) constituting the first torque detection unit 20A(5), is amplified via a gain-adjusting amplifier (not shown) to generate a first detection signal 23A. Similarly, a second detection signal 22B, which is the output of a second bridge circuit composed of three sets of strain gauges 11 (B1, B2), 11 (D1, D2), and 11 (F1, F2) constituting the second torque detection unit 20B(5), is amplified via a gain-adjusting amplifier (not shown) to generate a second detection signal 23B. These two detection signals are combined to generate a composite signal 23C. The composite signal obtained by adding the first and second torque detection signals of two independent systems, which have a phase difference of 30°, is a highly accurate detection output in which the sixth-order component of rotational ripple is removed and linearity is improved.

[0029] The graph shown in Fig. 11(A) is a graph showing actual measurements indicating the proportion of error components contained in the first torque detection signal obtained from the first torque detection unit shown in Fig. 10(B) (when three sets of strain gauges 11 are arranged at equal angles of 120°), and Fig. 11(B) is a graph showing the simulation results of torque detection by the torque detection unit 20(5) shown in Fig. 10. In these graphs, the horizontal axis indicates the input rotation angle (deg) of the wave generator, and the vertical axis indicates the proportion (%) of error components contained in the torque detection signal. In the graph shown in FIG. 11(B), the broken line La (actual measurement value) represents the error component ratio (actual measurement value) contained in the first torque detection signal obtained from the first torque detection unit shown in FIG. 11(A). The broken line Lb represents the error component ratio contained in the second torque detection signal obtained from the second torque detection unit. The broken line Lb is obtained by shifting the phase of the broken line La, which is the actual measurement value, by 30°. The broken line Lc (addition of two signals) represents the error component ratio contained in the combined signal obtained by combining the first torque detection signal and the second torque detection signal. As can be seen from the graph, the sixth-order periodic error component contained in the torque detection signal is significantly reduced.

[0030] Here, if the first and second torque detection units are configured from the six sets of strain gauges 11 shown in Figures 7 and 8 described above, it is possible to compensate for up to two frequency components contained in the rotational ripple by adjusting the gain of each of the six channel (6CH) signals (OUT1 to OUT6) of these torque detection units, but it is necessary to process the outputs of the 6CH individually. In contrast, in this example, the first torque detection unit is made up of three sets of strain gauges 11 arranged at angular intervals of 120°, and the second torque detection unit is made up of three sets of strain gauges 11 arranged in positions rotated 30° relative to the three sets of strain gauges 11 of the first torque detection unit. Simply by adding the 2CH outputs obtained from the first and second torque detection units, the sixth-order component of the rotational ripple is removed, and a highly accurate detection output (composite signal) with improved linearity can be obtained.

[0031] (Other embodiments) In the above example, a strain gauge is attached to the diaphragm of a top-hat shaped external gear. The strain gauge may be attached to a surface portion of the cylindrical body of the external gear other than the portion where the external teeth are formed. The present invention is also similarly applicable to strain wave gear devices with a cup-shaped external gear and strain wave gear devices with a cylindrical external gear.

[0032] In the above example, a two-axis overlapping arrangement type is used as the biaxial orthogonal strain gauge. However, a biaxial planar arrangement type is also known as a biaxial orthogonal strain gauge, and it goes without saying that this type of biaxial orthogonal strain gauge may also be used.

Claims

1. A strain wave gear device equipped with a torque detection device that detects a transmission torque transmitted via a flexible external gear, The torque detection device is a first torque detection unit and a second torque detection unit that output two independent systems of detection signals; an output combining unit that combines a first detection signal that is the detection signal of the first torque detection unit and a second detection signal that is the detection signal of the second torque detection unit to generate a combined signal; an output unit that outputs, to an outside of the torque detection device, the first detection signal, the second detection signal, and the composite signal, or a first detection torque signal, a second detection torque signal, and a composite torque signal that represent the transmission torque calculated based on these signals; It is equipped with the first torque detection unit includes a first group of strain gauges attached to a surface of the external gear at predetermined angular intervals around a central axis of the external gear, the second torque detection unit includes a second group of strain gauges attached to a surface of the external gear at predetermined angular intervals around a central axis of the external gear, the externally toothed gear has a cup or top hat shape including a cylindrical body portion on which external teeth are formed and a diaphragm extending radially from one end of the cylindrical body portion, the cylindrical body portion of the external gear is bent into an elliptical shape by a wave generator, and the external teeth located on the major axis of the elliptical shape are engaged with a rigid internal gear, the first group of strain gauges and the second group of strain gauges are attached to a surface of the diaphragm of the external gear, Eight sets of first to eighth strain gauges are arranged at equal angular intervals of 45° around the central axis, the first to eighth strain gauges are arranged in this order clockwise; the first torque detection unit includes the first, third, fifth, and seventh strain gauges as the first group of strain gauges, and an output of a first Wheatstone bridge circuit configured from these first, third, fifth, and seventh strain gauges is amplified and output as the first detection signal; The second torque detection unit includes the second, fourth, sixth, and eighth strain gauges as the second group of strain gauges, and the output of a second Wheatstone bridge circuit composed of these second, fourth, sixth, and eighth strain gauges is amplified and output as the second detection signal.

2. A strain wave gear device equipped with a torque detection device that detects a transmission torque transmitted via a flexible external gear, The torque detection device is a first torque detection unit and a second torque detection unit that output two independent systems of detection signals; an output combining unit that combines a first detection signal that is the detection signal of the first torque detection unit and a second detection signal that is the detection signal of the second torque detection unit to generate a combined signal; an output unit that outputs, to an outside of the torque detection device, the first detection signal, the second detection signal, and the composite signal, or a first detection torque signal, a second detection torque signal, and a composite torque signal that represent the transmission torque calculated based on these signals; It is equipped with the first torque detection unit includes a first group of strain gauges attached to a surface of the external gear at predetermined angular intervals around a central axis of the external gear, the second torque detection unit includes a second group of strain gauges attached to a surface of the external gear at predetermined angular intervals around a central axis of the external gear, the externally toothed gear has a cup or top hat shape including a cylindrical body portion on which external teeth are formed and a diaphragm extending radially from one end of the cylindrical body portion, the cylindrical body portion of the external gear is bent into an elliptical shape by a wave generator, and the external teeth located on the major axis of the elliptical shape are engaged with a rigid internal gear, the first group of strain gauges and the second group of strain gauges are attached to a surface of the diaphragm of the external gear, Eight sets of first to eighth strain gauges are arranged at equal angular intervals of 45° around the central axis, the first to eighth strain gauges are arranged in this order clockwise; the first torque detection unit includes the first to fourth strain gauges as the first group of strain gauges, and an output of a first Wheatstone bridge circuit configured from the first to fourth strain gauges is amplified and output as the first detection signal; The second torque detection unit includes the fifth to eighth strain gauges as the second group of strain gauges, and the output of a second Wheatstone bridge circuit composed of these fifth to eighth strain gauges is amplified and output as the second detection signal.

3. A strain wave gear device equipped with a torque detection device that detects a transmission torque transmitted via a flexible external gear, The torque detection device is a first torque detection unit and a second torque detection unit that output two independent systems of detection signals; an output combining unit that combines a first detection signal that is the detection signal of the first torque detection unit and a second detection signal that is the detection signal of the second torque detection unit to generate a combined signal; an output unit that outputs, to an outside of the torque detection device, the first detection signal, the second detection signal, and the composite signal, or a first detection torque signal, a second detection torque signal, and a composite torque signal that represent the transmission torque calculated based on these signals; It is equipped with the first torque detection unit includes a first group of strain gauges attached to a surface of the external gear at predetermined angular intervals around a central axis of the external gear, the second torque detection unit includes a second group of strain gauges attached to a surface of the external gear at predetermined angular intervals around a central axis of the external gear, the externally toothed gear has a cup or top hat shape including a cylindrical body portion on which external teeth are formed and a diaphragm extending radially from one end of the cylindrical body portion, the cylindrical body portion of the external gear is bent into an elliptical shape by a wave generator, and the external teeth located on the major axis of the elliptical shape are engaged with a rigid internal gear, the first group of strain gauges and the second group of strain gauges are attached to a surface of the diaphragm of the external gear, Eight sets of first to eighth strain gauges are arranged at equal angular intervals of 45° around the central axis, the first to eighth strain gauges are arranged in this order clockwise; the first torque detection unit includes the first, third, sixth, and eighth strain gauges as the first group of strain gauges, and an output of a first Wheatstone bridge circuit configured from these first, third, sixth, and eighth strain gauges is amplified and output as the first detection signal; The second torque detection unit includes the second, fourth, fifth, and seventh strain gauges as the second group of strain gauges, and the output of a second Wheatstone bridge circuit composed of these second, fourth, fifth, and seventh strain gauges is amplified and output as the second detection signal.

4. A strain wave gear device equipped with a torque detection device that detects a transmission torque transmitted via a flexible external gear, The torque detection device is a first torque detection unit and a second torque detection unit that output two independent systems of detection signals; an output combining unit that combines a first detection signal that is the detection signal of the first torque detection unit and a second detection signal that is the detection signal of the second torque detection unit to generate a combined signal; an output unit that outputs, to an outside of the torque detection device, the first detection signal, the second detection signal, and the composite signal, or a first detection torque signal, a second detection torque signal, and a composite torque signal that represent the transmission torque calculated based on these signals; It is equipped with the first torque detection unit includes a first group of strain gauges attached to a surface of the external gear at predetermined angular intervals around a central axis of the external gear, the second torque detection unit includes a second group of strain gauges attached to a surface of the external gear at predetermined angular intervals around a central axis of the external gear, the externally toothed gear has a cup or top hat shape including a cylindrical body portion on which external teeth are formed and a diaphragm extending radially from one end of the cylindrical body portion, the cylindrical body portion of the external gear is bent into an elliptical shape by a wave generator, and the external teeth located on the major axis of the elliptical shape are engaged with a rigid internal gear, the first group of strain gauges and the second group of strain gauges are attached to a surface of the diaphragm of the external gear, six sets of first to sixth strain gauges arranged at equal angular intervals of 60° around the central axis; the first to sixth strain gauges are arranged in this order clockwise; the first torque detection unit includes the first to third strain gauges as the first group of strain gauges, and outputs from the first to third strain gauges are amplified and then combined to be output as the first detection signal; The second torque detection unit includes the fourth to sixth strain gauges as the second group of strain gauges, and the outputs from these fourth to sixth strain gauges are amplified and then combined to be output as the second detection signal.

5. A strain wave gear device equipped with a torque detection device that detects a transmission torque transmitted via a flexible external gear, The torque detection device is a first torque detection unit and a second torque detection unit that output two independent systems of detection signals; an output combining unit that combines a first detection signal that is the detection signal of the first torque detection unit and a second detection signal that is the detection signal of the second torque detection unit to generate a combined signal; an output unit that outputs, to an outside of the torque detection device, the first detection signal, the second detection signal, and the composite signal, or a first detection torque signal, a second detection torque signal, and a composite torque signal that represent the transmission torque calculated based on these signals; It is equipped with the first torque detection unit includes a first group of strain gauges attached to a surface of the external gear at predetermined angular intervals around a central axis of the external gear, the second torque detection unit includes a second group of strain gauges attached to a surface of the external gear at predetermined angular intervals around a central axis of the external gear, the externally toothed gear has a cup or top hat shape including a cylindrical body portion on which external teeth are formed and a diaphragm extending radially from one end of the cylindrical body portion, the cylindrical body portion of the external gear is bent into an elliptical shape by a wave generator, and the external teeth located on the major axis of the elliptical shape are engaged with a rigid internal gear, the first group of strain gauges and the second group of strain gauges are attached to a surface of the diaphragm of the external gear, six sets of first to sixth strain gauges arranged clockwise at equal angular intervals of 60° around the central axis; the first to sixth strain gauges are arranged in this order clockwise; the first torque detection unit includes the first, third, and fifth strain gauges as the first group of strain gauges, and outputs from the first, third, and fifth strain gauges are amplified and then combined to be output as the first detection signal; The second torque detection unit includes the second, fourth, and sixth strain gauges as the second group of strain gauges, and the outputs from the second, fourth, and sixth strain gauges are amplified and then combined to be output as the second detection signal.

6. A strain wave gear device equipped with a torque detection device that detects a transmission torque transmitted via a flexible external gear, The torque detection device is a first torque detection unit and a second torque detection unit that output two independent systems of detection signals; an output combining unit that combines a first detection signal that is the detection signal of the first torque detection unit and a second detection signal that is the detection signal of the second torque detection unit to generate a combined signal; an output unit that outputs, to an outside of the torque detection device, the first detection signal, the second detection signal, and the composite signal, or a first detection torque signal, a second detection torque signal, and a composite torque signal that represent the transmission torque calculated based on these signals; It is equipped with the first torque detection unit includes a first group of strain gauges attached to a surface of the external gear at predetermined angular intervals around a central axis of the external gear, the second torque detection unit includes a second group of strain gauges attached to a surface of the external gear at predetermined angular intervals around a central axis of the external gear, the externally toothed gear has a cup or top hat shape including a cylindrical body portion on which external teeth are formed and a diaphragm extending radially from one end of the cylindrical body portion, the cylindrical body portion of the external gear is bent into an elliptical shape by a wave generator, and the external teeth located on the major axis of the elliptical shape are engaged with a rigid internal gear, the first group of strain gauges and the second group of strain gauges are attached to a surface of the diaphragm of the external gear, six sets of first to sixth strain gauges arranged clockwise at predetermined angular intervals around the central axis; the first to sixth strain gauges are arranged in this order clockwise; the first torque detection unit includes the first, third, and fifth strain gauges as the first group of strain gauges, and outputs from the first, third, and fifth strain gauges are combined and output as the first detection signal; the second torque detection unit includes the second, fourth, and sixth strain gauges as the second group of strain gauges, and outputs from the second, fourth, and sixth strain gauges are combined and output as the second detection signal; A strain wave gear device in which the second, fourth, and sixth strain gauges of the second group are arranged at positions rotated 30° clockwise relative to the first, third, and fifth strain gauges of the first group.

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