Strain wave gearing device provided with torque detection device

Abstract

A strain gauge type torque detection unit (20) of a strain wave gearing device (1) is provided with a first torque detection unit (20A) and a second torque detection unit (20B) that output detection signals of two independent systems. The first and second torque detection units (20A, 20B) are provided with a plurality of sets of strain gauges (11) that are attached to a diaphragm (3c) of the externally toothed gear (3) at predetermined angular intervals around the central axis. A first detection signal (22A) from a first torque detection unit (20A) and a second detection signal (22B) from a second torque detection unit (20B) are subjected to gain adjustment and then combined to generate a combined signal (23C). The transmission torque can be calculated on the basis of the first detection signal (23A), the second detection signal (23B), and the composite signal (23C). Three system outputs can be obtained from a torque detection device (10), said three system outputs being obtained by adding a high-precision output (24C) to detection outputs (24A, 24B) of two independent systems.

Description

Technical Field

[0001] The present invention relates to a wave gear device including a strain gauge type torque detection device for detecting a transmission torque transmitted via a flexible externally-toothed gear. Background Art

[0002] Patent Documents 1 to 3 propose a wave gear device with a torque detection device of a strain gauge type. In order to detect torque of a wave gear device with high accuracy, it is necessary to remove the periodic error component, i.e., rotation pulsation, contained in the output signal of the strain gauge that is generated independently of the transmitted torque, and improve the linearity of the detection output. Therefore, a plurality of sets of strain gauges are used in a manner that can compensate for the periodic error component, i.e., elliptical strain, contained in the detection output caused by the rotation of the wave generator.

[0003] In Patent Document 1, two sets of torque detection units consisting of a pair of strain gauges arranged at intervals of 90° on the surface of the external gear are arranged at a position after rotating around the central axis of the external gear by an angle of k×45° (k is an odd number), and the transmission torque is calculated based on the combined output of the detection outputs of the above two sets of torque detection units. In Patent Document 2, the following method is proposed: the gain of the output of each detection element is adjusted in a manner that can remove the periodic error contained in the detection output obtained by synthesizing the outputs of multiple detection elements. In Patent Document 3, the following method is proposed: when the number of rotational pulsation components to be compensated is set to N (N: a positive integer), (2N+1) or more strain gauges are attached to the external gear, and after the gain of each output is adjusted using an amplifier, synthesis is performed to generate a detection signal.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 3644558

[0007] Patent Document 2: Japanese Patent No. 4569990

[0008] Patent Document 3: Japanese Patent Application Publication No. 2004-45378 Summary of the invention

[0009] Here, when a torque sensor or the like is mounted on a human-cooperative robot or the like for the purpose of safety measures, it is desirable to realize duplexing or dual-systeming of sensors so that safety can be ensured even if a sensor fails.

[0010] The object of the present invention is to provide a wave gear device having a torque detection device in which a plurality of sets of strain gauges are carefully designed so that a strain gauge-type torque detection device is duplicated, thereby being able to obtain a three-system output with a high-precision output in addition to the detection output of two independent systems.

[0011] In order to solve the above-mentioned problems, the wave gear device of the present invention includes a torque detection device for detecting a transmission torque transmitted via a flexible externally toothed gear, and is characterized in that:

[0012] The torque detection device comprises:

[0013] A first torque detection unit and a second torque detection unit, which output two independent detection signals;

[0014] an output synthesis unit that synthesizes a first detection signal as the detection signal of the first torque detection unit and a second detection signal as the detection signal of the second torque detection unit to generate a synthesis signal; and

[0015] a calculation unit capable of calculating the transmission torque based on the first detection signal, the second detection signal, and the synthetic signal, respectively;

[0016] The first torque detection unit is a strain gauge type torque detection unit including a first set of strain gauges attached to the surface of the externally toothed gear at predetermined angular intervals with the central axis of the externally toothed gear as the center.

[0017] The second torque detection unit is a strain gauge type torque detection unit including a second set of strain gauges attached to the surface of the externally toothed gear at predetermined angular intervals with the central axis of the externally toothed gear as a center.

[0018] The external gear of the wave gear device is bent into an elliptical shape by the wave generator, and the part where the major axis of the elliptical shape is located is meshed with the rigid internal gear. As a periodic error component, the detection signal of the strain gauge contains an elliptical strain component with a period of 180° and an error component with a period of an integer multiple of 180°. In this case, for example, a plurality of strain gauges arranged at an angular interval 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. In addition, by synthesizing the detection signals of the two independent systems obtained from the two groups of strain gauges, a high-precision output can be obtained in which the rotation pulsation is removed and the linearity is improved.

[0019] Effects of the Invention

[0020] According to the present invention, in order to remove the periodic error component, the multiple sets of strain gauges arranged around the central axis of the external gear are divided into two groups, and two independent detection signals of the system are obtained. In addition, by synthesizing the detection signals of the two systems, the periodic error component is removed and a three-system output with high-precision output is obtained. As a result, the transmission torque can be detected with high precision, and a torque detection device that can ensure safety even if one detection unit fails can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is an explanatory diagram showing a wave gear device including a torque detection device to which the present invention is applied.

[0022] Figure 2 (A) is a schematic longitudinal sectional view of an external gear. Figure 2 (B) is a schematic end view of the external gear.

[0023] Figure 3 (A) is an explanatory diagram showing eight sets of strain gauges constituting a torque detection unit, Figure 3 (B) is an explanatory diagram showing a Wheatstone bridge circuit composed of eight sets of strain gauges.

[0024] Figure 4 (A) is an explanatory diagram showing four sets of strain gauges constituting the first torque detection unit, Figure 4 (B) is an explanatory diagram showing a first Wheatstone bridge circuit, Figure 4 (C) is an explanatory diagram showing four sets of strain gauges constituting the second torque detection unit, Figure 4 (D) is an explanatory diagram showing a second Wheatstone bridge circuit.

[0025] Figure 5 (A) is an explanatory diagram showing four sets of strain gauges constituting the first torque detection unit, Figure 5 (B) is an explanatory diagram showing a first Wheatstone bridge circuit, Figure 5 (C) is an explanatory diagram showing four sets of strain gauges constituting the second torque detection unit, Figure 5 (D) is an explanatory diagram showing a second Wheatstone bridge circuit.

[0026] Figure 6 (A) is an explanatory diagram showing four sets of strain gauges constituting the first torque detection unit, Figure 6 (B) is an explanatory diagram showing a first Wheatstone bridge circuit, Figure 6 (C) is an explanatory diagram showing four sets of strain gauges constituting the second torque detection unit, Figure 6 (D) is an explanatory diagram showing a second Wheatstone bridge circuit.

[0027] Figure 7 It is an explanatory diagram showing six sets of strain gauges constituting the torque detection unit.

[0028] Figure 8 (A) is an explanatory diagram showing three sets of strain gauges constituting the first torque detection unit, Figure 8 (B) is an explanatory diagram showing a first bridge circuit, Figure 8 (C) is an explanatory diagram showing three sets of strain gauges constituting the second torque detection unit, Figure 8 (D) is an explanatory diagram showing the second bridge circuit.

[0029] Fig. 9 (A) is an explanatory diagram showing three sets of strain gauges constituting the first torque detection unit, Fig. 9 (B) is an explanatory diagram showing three sets of strain gauges constituting the second torque detection unit.

[0030] Fig.10 (A) is an explanatory diagram showing six sets of strain gauges constituting a torque detection unit, Fig.10 (B) is an explanatory diagram showing three sets of strain gauges constituting the first torque detection unit, Fig.10 (C) is an explanatory diagram showing three sets of strain gauges constituting the second torque detection unit.

[0031] Fig.11 (A) is a graph showing the Fig.10 (B) is a graph showing the measurement result of the rotation pulsation (%) included in the torque detection output obtained by the first torque detection unit with respect to the input rotation angle, Fig.11

[0032] (B) is a graph showing the Fig.10 Graph showing simulation results of rotation pulsation included in a torque detection output (synthesized signal) obtained by a torque detection unit having the structure shown. DETAILED DESCRIPTION

[0033] (Overall structure)

[0034] Figure 1 This is a schematic longitudinal sectional view showing a wave gear device to which the present invention is applied. Figure 2 (A) is a longitudinal sectional view showing an external gear. Figure 2 (B) is an end view of the external gear on which the torque detection unit is mounted.

[0035] The wave gear device 1 includes: a rigid internal gear 2; a flexible external gear 3 coaxially arranged inside the internal gear; a wave generator 4 with an elliptical profile coaxially embedded inside the external gear; a cross roller bearing 5 supporting the internal gear 2 and the external gear 3 in a state of relative free rotation; 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. The shaft ends of the hollow input shaft 6 are supported by the end plates 7 and 8 via ball bearings 9a and 9b, respectively.

[0036] The external gear 3 is formed in a top hat shape and includes: a cylindrical main body 3b formed with external teeth 3a; a diaphragm 3c extending radially outward continuously from the one end; and an annular boss 3d formed on the outer peripheral edge of the diaphragm. The cylindrical main body 3b is bent into an elliptical shape by the wave generator 4, and the external teeth 3a are partially meshed with the internal teeth 2a of the internal gear 2. The wave generator 4 includes: a cam plate 4a of a constant width formed integrally with the hollow input shaft 6; and a wave bearing 4b fitted with the elliptical outer peripheral surface of the cam plate 4a.

[0037] When the wave generator 4 rotates with the rotation of the hollow input shaft 6, the meshing position of the two gears 2 and 3 moves in the circumferential direction, thereby generating a relative rotation between the two gears according to the difference in the number of teeth of the two gears. The internal gear 2 is sandwiched between the inner ring 5a of the cross roller bearing 5 and the end plate 7, and in this state, the three components are coaxially fastened and fixed. 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 in this state, the three components are coaxially fastened and fixed. For example, if the internal gear 2 side is fixed in a manner that does not rotate, the external gear 3 rotates and outputs a reduced rotation to the load component side (not shown) through the end plate 8 that functions as an output shaft.

[0038] (Torque detection device)

[0039] The wave gear device 1 is additionally provided with a torque detection device 10 for detecting the transmission torque transmitted by the external gear 3. The torque detection device 10 includes: a torque detection unit 20 mounted on the external gear 3; a signal processing unit 30 disposed outside the wave gear device 1; and a cable wiring 40 connecting the torque detection unit 20 and the signal processing unit 30. The torque detection unit 20 includes a plurality of strain gauges 11 attached to the diaphragm 3c of the external gear 3 and a flexible printed wiring substrate 12. In this example, as shown in FIG. Figure 2 As shown in (B), there are 8 sets of strain gauges arranged at equal angles of 45° around the central axis of the external gear 3. Figure 2As indicated by the mesh portion in (A), each strain gauge 11 is protected by a coating layer 13. In addition, wirings are connected to each other by a wiring pattern (not shown) formed on the flexible printed wiring substrate 12.

[0040] Figure 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 an orthogonal dual-axis structure, and is arranged at equal angular intervals of 45° around the central axis of the external gear 3. The strain gauges 11 are described below 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) in the clockwise direction.

[0041] (Torque detection unit)

[0042] like Figure 4 As shown, the torque detection unit 20 of this example is divided into a first torque detection unit 20A and a second torque detection unit 20B which output two independent detection signals.

[0043] like Figure 4 As shown in FIG. 2A , the first torque detection unit 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 intervals of 90°. Figure 4 As shown in (B), the above four groups of strain gauges form a first Wheatstone bridge circuit 21A. Figure 4 As shown in (C), the second torque detection unit 20B includes the remaining four sets of strain gauges 11 (B1, B2), 11 (D1, D2), 11 (F1, F2) and 11 (H1, H2) arranged at intervals of 90 degrees. Figure 4 As shown in FIG. 2A , the strain gauges constitute 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 unit 20A, and a second detection signal 22B, which is an output signal of the second Wheatstone bridge circuit 21B constituting the second torque detection unit 20B, are supplied to the signal processing unit 30 via the cable wiring 40.

[0044] like Figure 1As shown in FIG. 1 , 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 synthesis unit 31C that synthesizes the gain-adjusted first detection signal 23A and the second detection signal 23B to generate a synthesis signal 23C. In addition, the signal processing unit 30 includes a calculation unit 32 that calculates the transmission torque based on the gain-adjusted first detection signal 23A, the gain-adjusted second detection signal 23B, and the synthesis signal 23C, and an output port 33. The first detection torque signal 24A, the second detection torque signal 24B, and the synthesis torque signal 24C (high-precision detection signal) indicating the transmission torque calculated based on the first detection signal 23A, the second detection signal 23B, and the synthesis signal 23C, respectively, are output from the output port 33 to a controller or the like on the upstream side (not shown). When the first detection signal 23A, the second detection signal 23B, and the composite signal 23C are output from the output port 33 and the transmission torque value is calculated on the upstream side, it is also considered that the composite signal 23C is generated on the upstream side.

[0045] The composite signal 23C obtained by superimposing the first detection signal 23A and the second detection signal 23B of the two independent systems is Figure 3 The output of the Wheatstone bridge circuit composed of eight sets of strain gauges shown in (B) is equivalent to that of a high-precision detection output in which the rotation pulsation error is eliminated and the linearity is improved.

[0046] Thus, in the torque detection device 10 of this example, in order to remove the periodic error component, a torque detection mechanism capable of obtaining two independent detection signals is constructed by using eight sets of strain gauges 11 arranged around the central axis of the external gear 3. Even if one sensor system fails, the transmission torque can be continuously detected by the other, so safety is ensured. In addition, the detection output in which the periodic error component is removed by synthesizing the detection signals of the two systems can detect torque with high accuracy.

[0047] In addition, the high-precision signal (synthesized signal 23C) can also be obtained by superimposing the two system outputs (the first detection signal 23A and the second detection signal 23B) on the user side. In addition, if the output signals (23A, 23B) are digitally converted and serially output on the amplifier of the signal processing unit 30, the two system signals (23A, 23B) can also be output together with the high-precision signal (synthesized signal 23C). For example, in the case of two system signals with low precision of 12 bits and a high-precision signal of 12 bits, it can be sent as the upstream (first and second detection signals 23A, 23B) and downstream (synthesized signal 23C) of a 24-bit serial signal.

[0048] Figure 5 and Figure 6 Another example of dual systemization of the torque detection unit 20 is shown in FIG. 1 , in which strain gauges are arranged at eight locations spaced 45° apart. Figure 5 In the example of FIG. 1 , the torque detection unit is divided into: a first torque detection unit 20A (1), such as Figure 5 As shown in (A) and (B), it comprises a first Wheatstone bridge circuit 21A (1) composed of four sets of strain gauges 11 (A1, A2) to 11 (D1, D2); and a second torque detection unit 20B (1), as shown in Figure 5 As shown in (C) and (D), it includes a second Wheatstone bridge circuit 21B (1) composed of the remaining four sets of strain gauges 11 (E1, E2) to 11 (H1, H2).

[0049] exist Figure 6 In the example of FIG. 1 , the torque detection unit is divided into: a first torque detection unit 20A (2), such as Figure 6 As shown in (A) and (B), it has a first Wheatstone bridge circuit 21A (2) composed of four sets of strain gauges 11 (A1, A2), 11 (C1, C2), 11 (F1, F2), and 11 (H1, H2); and a second torque detection unit 20B (2), as shown in Figure 6 As shown in (C) and (D), it includes a second Wheatstone bridge circuit 21B(2) composed of the remaining four sets of strain gauges 11 (B1, B2), 11 (D1, D2), 11 (E1, E2), and 11 (G1, G2).

[0050] (Other Examples of Torque Detection Unit)

[0051] Figure 7 , another example of a torque detection unit 20 is shown. The torque detection unit 20 (3) shown in the figure has the following structure: the diaphragm of the external gear has 6 groups of strain gauges 11 (A1, A2) to 11 (F1, F2) pasted at equal angular intervals of 60° around the central axis (the strain gauges are arranged at 6 locations 60° apart).

[0052] Figure 8 and Fig. 9 2 shows an example in which the torque detection unit 20 ( 3 ) in this case is divided into two independent systems (a first torque detection unit 20A and a second torque detection unit 20B).

[0053] Figure 8 The torque detection unit 20 shown is divided into a first torque detection unit 20A (3) having a first bridge circuit 21A (3) composed of three sets of strain gauges 11 (A1, A2) to 11 (C1, C2); and a second torque detection unit 20B (3) having a second bridge circuit 21B (3) composed 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 constituting the first bridge circuit 21A (3) and the detection outputs from the three sets of strain gauges 11 constituting the second bridge circuit 21B (3).

[0054] In this case, the detection outputs (OUT1 to 3) from the three sets of strain gauges 11 constituting the first bridge circuit 21A (3) are synthesized after being amplified by an amplifier for gain adjustment (not shown) to generate a first detection signal. Similarly, the detection outputs (OUT4 to 6) from the three sets of strain gauges 11 constituting the second bridge circuit 21B (3) are synthesized after being amplified by an amplifier for gain adjustment (not shown) to generate a second detection signal. In addition, the first detection signal and the second detection signal are synthesized to generate a synthesized signal. The transmission torque is calculated based on the first detection signal, the second detection signal, and the synthesized signal.

[0055] Fig. 9 The figure shows a case where strain gauges are arranged at six locations spaced 60° apart (see Figure 7 ) is another example of dual systemization of the torque detection unit 20 (3). Fig. 9 In the example of , the torque detection unit is divided into: a first torque detection unit 20A (4), which has 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), which has 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, Figure 8 The outputs of the three systems can be obtained in the same manner as in the example of . The transmission torque can be calculated based on the outputs of the three systems respectively.

[0056] (Another Example of Torque Detection Unit)

[0057] Fig.10(A) shows another example of a torque detection unit 20 having two independent systems of a first torque detection unit and a second torque detection unit. The torque detection unit 20 (5) shown in the figure has six sets of strain gauges 11 (A1, A2) to 11 (F1, F2) attached to the diaphragm of the external gear. Fig.10 As shown in (B), the three sets of strain gauges 11 (A1, A2), 11 (C1, C2) and 11 (E1, E2) constituting the first torque detection unit 20A (5) are attached at equal angular intervals of 120° around the central axis of the diaphragm. Fig.10 As shown in (C), the remaining three sets of strain gauges 11 (B1, B2), 11 (D1, D2) and 11 (F1, F2) constituting the second torque detection unit 20B (5) are also attached at equal angular intervals of 120° around the central axis of the diaphragm. Furthermore, the three sets of strain gauges 11 (B1, B2), 11 (D1, D2) and 11 (F1, F2) are respectively located at angular positions rotated by 30° with respect to the three sets of strain gauges 11 (A1, A2), 11 (C1, C2) and 11 (E1, E2) arranged at angular intervals of 120°.

[0058] In this case, the output of the first bridge circuit composed of the three sets of strain gauges 11 (A1, A2), 11 (C1, C2) and 11 (E1, E2) constituting the first torque detection unit 20A (5), that is, the first detection signal 22A is amplified by an amplifier for gain adjustment (not shown) to generate a first detection signal 23A. Similarly, the output of the second bridge circuit composed of the three sets of strain gauges 11 (B1, B2), 11 (D1, D2) and 11 (F1, F2) constituting the second torque detection unit 20B (5), that is, the second detection signal 22B is amplified by a gain adjustment unit (not shown) to generate a second detection signal 23B. The synthetic signal 23C is generated by synthesizing the detection signals of the above two systems. The synthetic signal obtained by superimposing the first torque detection signal and the second torque detection signal of two independent systems with a phase difference of 30° is a high-precision detection output with the sixth-order component of the rotation pulsation removed and the linearity improved.

[0059] Fig.11 The graph shown in (A) is a graph showing the Fig.10 (B) is an actual measurement value of the ratio of the error component included in the first torque detection signal obtained by the first torque detection unit (when three sets of strain gauges 11 are arranged at an equal angle of 120°), Fig.11 (B) is shown Fig.10 Graph showing simulation results of torque detection by the torque detection unit 20 (5) shown in FIG. 1. In the graph, the horizontal axis represents the input rotation angle (deg) of the wave generator, and the vertical axis represents the ratio (%) of the error component included in the torque detection signal.

[0060] exist Fig.11 In the graph shown in (B), the broken line La (actual measured value) is Fig.11 (A) shows the ratio of the error component contained in the first torque detection signal obtained by the first torque detection unit (actual measurement value). The broken line Lb shows the ratio of the error component contained in the second torque detection signal obtained from the second torque detection unit. The broken line Lb is the result of making the phase of the broken line La, which is the actual measurement value, shift by 30°. The broken line Lc (two signal superposition operation) shows the ratio of the error component contained in the synthesized signal obtained by synthesizing the first torque detection signal and the second torque detection signal. As can be seen from the graph, the six-order periodic error component contained in the torque detection signal is greatly reduced.

[0061] Here, in the previously described Figure 7 , Figure 8 In the case where the first and second torque detection units are composed of 6 groups of strain gauges 11 as shown, the signals (OUT1~OUT6) of the 6 channels (6CH) of the above-mentioned torque detection unit are gain adjusted respectively, so as to compensate for the 2 frequency components contained in the rotational pulsation, but the outputs of 6CH need to be processed separately.

[0062] In contrast, in this example, the first torque detection unit is composed of three sets of strain gauges 11 arranged at an angular interval of 120°, and the second torque detection unit is composed of three sets of strain gauges 11 arranged at a position rotated 30° relative to the three sets of strain gauges 11 of the first torque detection unit. By simply superimposing the 2CH outputs obtained from the first and second torque detection units, a high-precision detection output (synthesized signal) can be obtained in which the sixth-order component of the rotation pulsation is removed and the linearity is improved.

[0063] (Other embodiments)

[0064] In the above example, the strain gauge is attached to the diaphragm of the external gear formed in a top-hat shape as the external gear. The attachment position of the strain gauge may be a surface portion other than the portion where the external teeth of the cylindrical body of the external gear are formed. In addition, the present invention can also be applied to a wave gear device having an external gear formed in a cup shape and a wave gear device having a cylindrical external gear.

[0065] In the above example, a two-axis overlapping arrangement is used as a two-axis orthogonal strain gauge. A two-axis planar arrangement is also known as a two-axis orthogonal strain gauge, and this type of two-axis orthogonal strain gauge may also be used.

Claims

1. A wave gear device comprising a torque detection device for detecting a transmission torque transmitted via a flexible externally toothed gear, characterized in that: The torque detection device comprises: A first torque detection unit and a second torque detection unit, which output two independent detection signals; an output synthesis unit that synthesizes a first detection signal as the detection signal of the first torque detection unit and a second detection signal as the detection signal of the second torque detection unit to generate a synthesis signal; as well as an output unit that outputs the first detection signal, the second detection signal, and the synthesized signal, or a first detection torque signal, a second detection torque signal, and a synthesized torque signal indicating the transmission torque calculated based on these signals, The first torque detection unit includes a first set of strain gauges attached to the surface of the externally toothed gear at predetermined angular intervals with the central axis of the externally toothed gear as the center. The second torque detection unit includes a second set of strain gauges attached to the surface of the externally-toothed gear at predetermined angular intervals with the central axis of the externally-toothed gear as a center.

2. The wave gear device according to claim 1, characterized in that: The externally toothed gear is formed in a cup or hat shape including a cylindrical main body portion having external teeth and a diaphragm extending in a radial direction from one end of the cylindrical main body portion. The cylindrical main body of the external gear is bent into an elliptical shape by the wave generator, and the external teeth located on the major axis of the elliptical shape mesh with the rigid internal gear. The first set of strain gauges and the second set of strain gauges are adhered to the surface of the diaphragm of the external gear.

3. The wave gear device according to claim 2, characterized in that: The wave gear device includes eight sets of first to eighth strain gauges arranged at equal angular intervals of 45° around the central axis. The first to eighth strain gauges are arranged in this order in a clockwise direction. The first torque detection unit includes the first strain gauge, the third strain gauge, the fifth strain gauge, and the seventh strain gauge as the first set of strain gauges, and amplifies the output of the first Wheatstone bridge circuit composed of the first strain gauge, the third strain gauge, the fifth strain gauge, and the seventh strain gauge and outputs the amplified output as the first detection signal. As the second group of strain gauges, the second torque detection unit includes the second strain gauge, a fourth strain gauge, a sixth strain gauge and an eighth strain gauge, and amplifies the output of the second Wheatstone bridge circuit composed of the second strain gauge, the fourth strain gauge, the sixth strain gauge and the eighth strain gauge and outputs it as the second detection signal.

4. The wave gear device according to claim 2, characterized in that: The wave gear device includes eight sets of first to eighth strain gauges arranged at equal angular intervals of 45° around the central axis. The first to eighth strain gauges are arranged in this order in a clockwise direction. The first torque detection unit includes the first to fourth strain gauges as the first set of strain gauges, and amplifies the output of a first Wheatstone bridge circuit composed of the first to fourth strain gauges and outputs the amplified output as the first detection signal. The second torque detection unit includes the fifth to eighth strain gauges as the second set of strain gauges, and amplifies an output of a second Wheatstone bridge circuit composed of the fifth to eighth strain gauges and outputs the amplified output as the second detection signal.

5. The wave gear device according to claim 2, characterized in that: The wave gear device includes eight sets of first to eighth strain gauges arranged at equal angular intervals of 45° around the central axis. The first to eighth strain gauges are arranged in this order in a clockwise direction. The first torque detection unit includes the first strain gauge, the third strain gauge, the sixth strain gauge, and the eighth strain gauge as the first set of strain gauges, and amplifies the output of the first Wheatstone bridge circuit composed of the first strain gauge, the third strain gauge, the sixth strain gauge, and the eighth strain gauge and outputs the amplified output as the first detection signal. As the second group of strain gauges, the second torque detection unit includes the second strain gauge, a fourth strain gauge, a fifth strain gauge and a seventh strain gauge, and amplifies the output of the second Wheatstone bridge circuit composed of the second strain gauge, the fourth strain gauge, the fifth strain gauge and the seventh strain gauge and outputs it as the second detection signal.

6. The wave gear device according to claim 2, characterized in that: The wave gear device includes 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 in a clockwise direction. The first torque detection unit includes the first to third strain gauges as the first set of strain gauges, and outputs from the first to third strain gauges are synthesized after amplifying the outputs respectively and output as the first detection signal. The second torque detection unit includes the fourth to sixth strain gauges as the second set of strain gauges, and outputs from the fourth to sixth strain gauges are synthesized after amplifying the outputs respectively and output as the second detection signal.

7. The wave gear device according to claim 2, characterized in that: The wave gear device includes six sets of first to sixth strain gauges arranged in a clockwise direction at equal angular intervals of 60 degrees around the central axis. The first to sixth strain gauges are arranged in this order in a clockwise direction. The first torque detection unit includes the first strain gauge, a third strain gauge, and a fifth strain gauge as the first set of strain gauges, and outputs from the first strain gauge, the third strain gauge, and the fifth strain gauge are synthesized after being amplified and output as the first detection signal. The second torque detection unit includes the second strain gauge, a fourth strain gauge, and a sixth strain gauge as the second set of strain gauges, and outputs from the second strain gauge, the fourth strain gauge, and the sixth strain gauge are synthesized after being amplified and output as the second detection signal.

8. The wave gear device according to claim 2, characterized in that: The wave gear device includes six sets of first to sixth strain gauges arranged in a clockwise direction at equal angular intervals of 60 degrees around the central axis. The first to sixth strain gauges are arranged in this order in a clockwise direction. The first torque detection unit includes the first strain gauge, a third strain gauge, and a fifth strain gauge as the first set of strain gauges, and outputs from the first strain gauge, the third strain gauge, and the fifth strain gauge are synthesized and output as the first detection signal. The second torque detection unit includes the second strain gauge, a fourth strain gauge, and a sixth strain gauge as the second set of strain gauges, and outputs from the second strain gauge, the fourth strain gauge, and the sixth strain gauge are synthesized and output as the second detection signal. The second strain gauge, the fourth strain gauge, and the sixth strain gauge of the second set of strain gauges are respectively arranged at positions rotated by 30° in the clockwise direction with respect to the first strain gauge, the third strain gauge, and the fifth strain gauge of the first set of strain gauges.

Images