Sensor device

Abstract

The present invention aims to reduce the influence of temperature in the detection environment to enable good detection of a state quantity. The present invention provides a sensor device (60) that detects a prescribed state quantity, performs a first detection and a second detection that produces a smaller state quantity than the first detection, and has a correction section (61) that corrects the detection value of the first detection based on the detection value of the second detection. The detection value of the second detection, which is a smaller state quantity, is less affected by the ambient temperature, so, for example, the correction section (61) corrects the detection value obtained by the first detection based on the detection value obtained by the second detection, thereby enabling accurate detection of the state quantity.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2021-123292 filed on July 28, 2021. The entire contents of this Japanese application are incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to a sensor device. BACKGROUND

[0003] As a sensor device that detects a state quantity of a device, for example, there is a device that detects a strain of an internal gear of a flexspline gear device using a strain gauge (for example, refer to Patent Literature 1).

[0004] Patent Literature 1: Japanese Patent Application Laid-Open No. Hei 07-20537

[0005] However, in the past, there is room for improvement in countermeasures against external disturbances. SUMMARY

[0006] An object of the present application is to reduce the influence of external disturbances and thereby enable good detection of a state quantity.

[0007] The present application provides a sensor device that detects a prescribed state quantity, wherein

[0008] a first detection and a second detection that produces a smaller state quantity than the first detection are performed,

[0009] The sensor device has a correction section that corrects a detection value of the first detection based on a detection value of the second detection.

[0010] According to the present application, it is possible to reduce the influence of external disturbances and thereby enable good detection of a state quantity. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is an axial sectional view showing a flexspline gear device to which a sensor device according to a first embodiment of the present application is applied.

[0012] Figure 2 is a perspective view of a first internal gear member.

[0013] Figure 3 (A) is a circuit diagram of a Wheatstone bridge circuit to which two strain gauges arranged in a non-diagonal configuration are assembled, Figure 3 (B) is an equivalent circuit diagram thereof.

[0014] Figure 4 is a front view showing a first internal gear member of a flexspline gear device to which a sensor device according to a second embodiment of the present application is applied.

[0015] Figure 5 is another perspective view showing the first internal tooth member of the flexspline type gear device to which the sensor device according to the third embodiment is applied.

[0016] Figure 6 is an axial sectional view of the first internal tooth member of Figure 5 .

[0017] Figure 7 is a front view showing the first internal tooth member of the flexspline type gear device to which the sensor device according to the fourth embodiment is applied.

[0018] Figure 8 is a front view of the first internal tooth member of the flexspline type gear device to which the sensor device according to the fifth embodiment is applied.

[0019] In the figure: 1 - gear device, 30 - vibration generator shaft, 30A - vibration generator, 32 - first external tooth portion (external gear), 33 - second external tooth portion (external gear), 41 - first internal tooth member, 411 - first internal tooth portion, 412 - internal tooth annular portion, 413 - external connecting portion, 414 - easily deformable portion, 415 - columnar member, 416, 416-1 to 416-7 - strain gauge (detection portion), 417 - measuring device, 417G - measuring device (correction portion), 418 - processing circuit, 42 - second internal tooth member, 421 - second internal tooth portion, 60, 60G - sensor device, 61 - Wheatstone bridge circuit (correction portion), O1 - rotation axis, R1, R2 - resistor. DETAILED DESCRIPTION

[0020] Hereinafter, embodiments of the present application will be described in detail with reference to the drawings.

[0021] [First Embodiment]

[0022] In this first embodiment, a flexspline type gear device 1 (rotary device) is exemplified as an object (i.e., an object device) of which a state quantity is detected, and a sensor device 60 detects a strain (state quantity) of the flexspline type gear device 1 using a strain gauge 416 (detection portion) (refer to Figure 2 ). In addition, the strain detected by the sensor device 60 is used for torque detection of the flexspline type gear device 1.

[0023] [Flexspline Type Gear Device]

[0024] Figure 1 is an axial sectional view showing the flexspline type gear device 1 to which the sensor device 60 according to the first embodiment of the present application is applied.

[0025] In addition, in the following description, a direction parallel to the rotation axis O1 is referred to as an axial direction, a circumferential direction of a circle centered on the rotation axis O1 is referred to as a circumferential direction, and a radial direction of the circle centered on the rotation axis O1 is referred to as a radial direction.

[0026] The flexspline gear device 1 is, for example, a speed reduction device. The flexspline gear device 1 is not particularly limited in use and can be applied to various uses, for example, can be used for driving a joint of a collaborative robot that works in cooperation with a person. The flexspline gear device 1 includes a vibration body shaft 30, a vibration body bearing 31, a first external tooth portion 32 (external gear), a second external tooth portion 33 (external gear), a first internal tooth portion 411, a second internal tooth portion 421, a housing 43, a first cover 44, a second cover 45, a third cover 49, bearings 46, 47, a main bearing 48, and stop rings 51, 52.

[0027] The vibration body shaft 30 is a hollow cylindrical shaft that rotates about the rotation axis O1 and has a vibration body 30A having a non-circular (for example, elliptical) shape in a cross section perpendicular to the rotation axis O1 (shaft right angle cross section) and shaft portions 30B, 30C provided on both axial sides of the vibration body 30A. The elliptical shape is not necessarily a geometrically strict ellipse and can include a substantially elliptical shape. The shaft portions 30B, 30C are shafts having a circular shape in a cross section perpendicular to the rotation axis O1. In addition, the vibration body shaft 30 can be a solid shaft.

[0028] The first internal tooth portion 411 is configured by providing teeth on a portion of an inner periphery of a first internal tooth member 41 that is an internal gear having rigidity.

[0029] The second internal tooth portion 421 is configured by providing teeth on a portion of an inner periphery of a second internal tooth member 42 having rigidity.

[0030] The first external tooth portion 32 and the second external tooth portion 33 are provided integrally on an outer periphery of one metal cylindrical base portion 34 having flexibility and are arranged on one side and the other side in the axial direction. These first external tooth portion 32, second external tooth portion 33, and base portion 34 configure an external gear.

[0031] Furthermore, the first external tooth portion 32 is engaged with the first internal tooth portion 411, and the second external tooth portion 33 is engaged with the second internal tooth portion 421.

[0032] The vibration body bearing 31 is, for example, a roller bearing and is disposed between the vibration body 30A and the base portion 34 in which the first external tooth portion 32 and the second external tooth portion 33 are formed. With the vibration body bearing 31, the vibration body 30A and the first external tooth portion 32 and the second external tooth portion 33 are able to rotate relatively.

[0033] The vibration generator bearing 31 has an outer ring 31a embedded inside the base 34, a plurality of rolling elements (rollers) 31b, and a retainer 31c that holds the plurality of rolling elements 31b.

[0034] The plurality of rolling elements 31b have a first group of rolling elements 31b arranged radially inside the first outer tooth portion 32 and the first inner tooth portion 41 and arranged in the circumferential direction, and a second group of rolling elements 31b arranged radially inside the second outer tooth portion 33 and the second inner tooth portion 42 and arranged in the circumferential direction. These rolling elements 31b roll on the outer circumferential surface of the vibration generator 30A and the inner circumferential surface of the outer ring 31a as rolling surfaces. The vibration generator bearing 31 can also have an inner ring that is separate from the vibration generator 30A. Also, the vibration generator bearing 31 can omit the outer ring 31a and use the inner circumferential surface of the base 34 as an outer ring side rolling surface. The type of rolling element is not particularly limited, and for example, a ball can also be used. Also, the number of rows of rolling elements is not limited to two, and can be one row or three or more rows.

[0035] The stop rings 51, 52 are arranged on both axial sides of the first outer tooth portion 32, the second outer tooth portion 33, and the vibration generator bearing 31, and restrict movement of the first outer tooth portion 32, the second outer tooth portion 33, and the vibration generator bearing 31 in the axial direction.

[0036] The housing 43 covers the outer circumferential side of the second inner tooth member 42. An outer ring portion of a main bearing 48 is formed on the inner circumferential portion of the housing 43, and the housing 43 supports the second inner tooth member 42 so as to be rotatable via the main bearing 48. The housing 43 is joined to the first inner tooth member 41 via a joining member such as a bolt, for example.

[0037] The main bearing 48 is, for example, a cross roller bearing, and has a plurality of rolling elements arranged between an inner ring portion integrated with the second inner tooth member 42 and an outer ring portion integrated with the housing 43. The type of main bearing 48 is not particularly limited, and for example, can be composed of a plurality of bearings (angular contact ball bearings, tapered bearings, etc.) arranged in the axial direction between the second inner tooth member 42 and the housing 43, or can be a four-point contact ball bearing. Also, the main bearing 48 can have a dedicated inner ring and outer ring that are different from the second inner tooth member 42 and the housing 43.

[0038] Also, an oil seal 541 is provided between the housing 43 and the second inner tooth member 42 and on the output side of the main bearing 48, and suppresses the outflow of lubricant to the axial outer side (the output side).

[0039] The first cover 44 is joined to the third cover 49 via a joining member such as a bolt, which is not shown, for example, and the third cover 49 is joined to the first inner tooth member 41 and the housing 43 via a joining member such as a bolt, which is not shown, for example.

[0040] Further, the first cover 44 covers the first outer tooth portion 32 and the first inner tooth portion 411 from the output opposite side in the axial direction. The first cover 44, the third cover 49, the first inner tooth member 41, and the housing 43 are directly or indirectly coupled to an external member (for example, a base end side arm member of a collaborative robot).

[0041] Further, the side on which the reduced speed movement is output to the external member (also referred to as an object member. For example, one of the members that mutually perform power transmission of a main device in which the flex engagement gear device 1 is assembled as a component, etc.) is referred to as an output side, and the side opposite to the output side in the axial direction is referred to as an output opposite side. A bearing 46 is provided between the first cover 44 and the shaft portion 30B of the vibration generating body shaft 30, and thus the vibration generating body shaft 30 is rotatably supported by the first cover 44. Further, a ball bearing is exemplified as the bearing 46, but other radial bearings can be used.

[0042] Further, an oil seal 542 is provided at a position between the first cover 44 and the shaft portion 30B of the vibration generating body shaft 30 and further on the output opposite side than the bearing 46, and suppresses the lubricant from flowing out to the outside in the axial direction (the output opposite side).

[0043] The second cover 45 is coupled to the second inner tooth member 42, for example, via a coupling member 533 such as a bolt, and covers the second outer tooth portion 33 and the second inner tooth portion 421 from the output side in the axial direction. The second cover 45 and the second inner tooth member 42 are coupled to an external member (for example, a base end side arm member of a collaborative robot) that rotates relatively with respect to an external member coupled to the first inner tooth member 41 and the like (the external member is a member that rotates relatively with respect to the external member).

[0044] A bearing 47 is provided between the second cover 45 and the shaft portion 30C of the vibration generating body shaft 30, and thus the vibration generating body shaft 30 is rotatably supported by the second cover 45. Further, a ball bearing is exemplified as the bearing 47, but other radial bearings can be used.

[0045] Further, an oil seal 543 is provided at a position between the second cover 45 and the shaft portion 30C of the vibration generating body shaft 30 and further on the output side than the bearing 47, and suppresses the lubricant from flowing out to the outside in the axial direction (the output side). Further, the second cover 45 can be integrated with the second inner tooth member 42.

[0046] Further, a seal O-ring 551 is attached between the first inner tooth member 41 and the housing 43.

[0047] Likewise, a seal O-ring 554 is installed between the first inner tooth member 41 and the third cover 49, a seal O-ring 552 is installed between the third cover 49 and the first cover 44, and a seal O-ring 553 is installed between the second inner tooth member 42 and the second cover 45.

[0048] Therefore, the inside space of the flex engagement gear device 1 (a space in which the meshing portions of the first outer tooth portion 32 and the first inner tooth portion 411, the meshing portions of the second outer tooth portion 33 and the second inner tooth portion 421, the main bearing 48, the bearings 46, 47, and the vibration body bearing 31 exist) becomes a lubricant-enclosed space in which a lubricant is enclosed, and is sealed by the oil seals 541 to 543 or the O-rings 551 to 554.

[0049] Figure 2 FIG. 1 is a perspective view of the first inner tooth member 41. As shown in FIG. 1, the first inner tooth member 41 includes an inner tooth annular portion 412 in which the first inner tooth portion 411 is formed on an inner periphery, an outer portion linking portion 413 which links to an outer portion member together with the housing 43 and the third cover 49, and a deformation-easy portion 414 which is structured to be more easily deformed (greater deformation amount) than the inner tooth annular portion 412 when a torque acts on the first inner tooth member 41. Figure 2

[0050] The inner tooth annular portion 412 is annular and has the first inner tooth portion 411 (inner tooth) formed on an inner peripheral surface thereof.

[0051] The outer portion linking portion 413 is annular and is located at an outermost periphery of the first inner tooth member 41. On the outer portion linking portion 413, a plurality of mounting holes for mounting an outer portion member are formed at regular intervals in a circumferential direction, penetrating the outer portion linking portion 413 in an axial direction. The outer portion linking portion 413 can be directly linked to the outer portion member, or can be linked to the outer portion member via the first cover 44 or the third cover 49.

[0052] The deformation-easy portion 414 is composed of a plurality of columnar members 415 which are discontinuously provided between the inner tooth annular portion 412 and the outer portion linking portion 413 in the circumferential direction.

[0053] The columnar members 415 extend from an outer periphery of the inner tooth annular portion 412 toward a radially outer side, and link to an inner periphery of the outer portion linking portion 413. In this example, a case in which the deformation-easy portion 414, the inner tooth annular portion 412, and the outer portion linking portion 413 are formed in one piece from the same material (for example, a metal material, a resin material, or the like) is illustrated.

[0054] Further, a case in which the columnar members 415 are provided at four places at regular intervals in the circumferential direction is illustrated. That is, the columnar members 415 are respectively arranged at both ends in two diametric directions which are orthogonal to each other of the first inner tooth member 41.​

[0055] The intervals in the circumferential direction of each columnar member 415 are preferably equal, but this is not essential. Also, the number of columnar members 415 can be increased or decreased.

[0056] The axial width (thickness) of the outer linking portion 413 and the columnar member 415 is equal, and is smaller than the axial width of the inner toothed annular portion 412. Also, the axial width of the columnar member 415 can be different from the axial width of the outer linking portion 413, for example, it can be made smaller than the axial width of the outer linking portion 413, provided that the strength for ensuring the torque transmission function is sufficient. Also, the columnar member 415 can have a recess that accommodates the strain gauge 416.

[0057] Also, on the plane on the output side inside the radial direction of the outer linking portion 413, a ridge 413a that protrudes toward the output side is formed over the entire circumferential direction, and is fitted (latch-fitted) into a recess on the opposite side of the output of the housing 43.

[0058] [Deceleration action]

[0059] If a rotational motion is input from a motor or the like that is not shown in the drawing, so that the vibration body shaft 30 rotates, the motion of the vibration body 30A is transmitted to the first outer tooth portion 32 and the second outer tooth portion 33. At this time, the shape of the first outer tooth portion 32 and the second outer tooth portion 33 is restricted to a shape that corresponds to the shape of the outer circumferential surface of the vibration body 30A, and when viewed from the axial direction, it is flexed into an elliptical shape that has a major axis portion and a minor axis portion. Also, the major axis portion of the first outer tooth portion 32 engages with the first inner tooth portion 411 of the fixed first inner tooth member 41. Therefore, the first outer tooth portion 32 and the second outer tooth portion 33 do not rotate at the same rotational speed as the vibration body 30A, but the vibration body 30A relatively rotates inside the first outer tooth portion 32 and the second outer tooth portion 33. Also, along with this relative rotation, the first outer tooth portion 32 and the second outer tooth portion 33 are flexibly deformed in a manner that moves the positions of the major axis and the minor axis in the circumferential direction. The deformation period is proportional to the rotation period of the vibration body shaft 30.

[0060] When the first outer tooth portion 32 and the second outer tooth portion 33 are flexibly deformed, the position of the major axis moves, and thus the engagement position between the first outer tooth portion 32 and the first inner tooth portion 411 changes in the rotational direction. Here, if the number of teeth of the first outer tooth portion 32 is set to 100 and the number of teeth of the first inner tooth portion 411 is set to 102, the engagement position is sequentially shifted by one tooth per rotation, and thus the first outer tooth portion 32 rotates (spins). If the numbers of teeth are set as described above, the rotational motion of the vibration body shaft 30 is transmitted to the first outer tooth portion 32 at a deceleration ratio of 100:2.

[0061] On the other hand, the second external tooth 33, which shares a base 34 with the first external tooth 32, meshes with the second internal tooth 421. Therefore, due to the rotation of the vibrator shaft 30, the meshing position between the second external tooth 33 and the second internal tooth 421 also changes in the rotational direction. Furthermore, the number of teeth in the second internal tooth 421 is set to be the same as the number of teeth in the second external tooth 33. Therefore, the second external tooth 33 and the second internal tooth 421 do not rotate relative to each other, and the rotational motion of the second external tooth 33 is transmitted to the second internal tooth 421 with a reduction ratio of 1:1. Thus, the rotational motion of the vibrator shaft 30 is reduced to a reduction ratio of 100:2 and then transmitted to the second internal tooth component 42 and the second cover 45. Moreover, this reduced rotational motion is output to the external components.

[0062] [Sensor Device]

[0063] like Figure 2 As shown, the sensor device 60 includes strain gauges 416-1 to 416-4, which serve as detection units, and measuring devices 417 connected to each strain gauge 416-1 to 416-4, which are mounted on each columnar member 415 of the first internal tooth member 41.

[0064] All the strain gauges 416-1 to 416-4 mentioned above are strain gauges with the same structure, characteristics and performance. Therefore, when there is no need to distinguish them and to describe them uniformly, they are collectively referred to as "strain gauge 416".

[0065] Strain gauges 416-1 and 416-3 are respectively disposed on one and the other of two columnar components 415 located at both ends in the diametrical direction, and strain gauges 416-2 and 416-4 are respectively disposed on one and the other of two columnar components 415 located at both ends in another diametrical direction orthogonal to the aforementioned diametrical direction.

[0066] In addition, in the following description, the configuration of two strain gauges 416-1 and 416-3 located at both ends in the diametrical direction and the configuration of two strain gauges 416-2 and 416-4 located at both ends in the other diametrical direction are referred to as "diagonal configurations". The configurations of two strain gauges 416-1 and 416-2, two strain gauges 416-1 and 416-4, two strain gauges 416-3 and 416-2, and two strain gauges 416-3 and 416-4 that are not "diagonal configurations" are referred to as "non-diagonal configurations".

[0067] Also, in the rotational operation of the flex engagement gear device 1, the strain gauge 416 being located on the "long axis side" of the vibration generator 30A indicates that it is located within a prescribed angular range on both sides in the circumferential direction from the center of the long axis of the vibration generator 30A. Also, it is possible to recognize that the strain gauge 416 is located closer to the long axis than the short axis of the vibration generator 30A as being located on the "long axis side".

[0068] Also, the strain gauge 416 being located on the "short axis side" of the vibration generator 30A indicates being located closer to the short axis than in the case of being located on the long axis side (a case of being located outside the long axis side), and it is possible to indicate being located within a prescribed angular range on both sides in the circumferential direction from the center of the short axis of the vibration generator 30A.

[0069] The prescribed angle in the "long axis side" or "short axis side" is, for example, within a range of 45° in each of the two directions from the center of the long axis or short axis, but it can also be set to be narrower.

[0070] Here, a case is exemplified in which the strain gauge 416 is installed in the direction of detecting the radial direction expansion and contraction strain in the columnar member 415.

[0071] In addition, the direction of the strain detected by the strain gauge 416 is not limited only to the radial direction, but can also be the circumferential direction, the axial direction, or an oblique direction that is a combination thereof.

[0072] When torque acts on the first inner tooth member 41 (specifically, when the outer coupling portion 413 is coupled to the outer member, the first inner tooth 411 receives engagement reaction force resulting in torque acting on the first inner tooth member 41), the easily deformable portion 414 (the columnar member 415) deforms more than the inner tooth ring portion 412. As a result, the radial direction expansion and contraction strain generated in the columnar member 415 also becomes larger. Since the strain of this columnar member 415 is related to the torque, by detecting the strain by the strain gauge 416, it is possible to acquire the torque.

[0073] Each strain gauge 416 is connected to a measurement device 417. In addition, in Figure 2 Here, a state in which only one strain gauge 416 is connected is illustrated, but in fact, all of the strain gauges 416 are connected to the measurement device 417.

[0074] The strain gauge 416 has a characteristic in which the resistance value changes according to the strain, and thus the measurement device 417 is able to acquire the strain by receiving a detection signal (for example, a voltage signal) indicating the resistance value of each strain gauge 416.

[0075] In the flexion engagement gear device 1, the columnar members 415 on the long axis side of the generally elliptical vibration generating body 30A are most contracted. The measuring device 417 is provided with a rotation detection device (omitted from the drawing) that detects the rotation angle of the vibration generating body 30A, and acquires the strain detection signal from each strain gauge 416 at the time when the rotation angle at which each columnar member 415 is on the long axis side of the vibration generating body 30A is detected.

[0076] Also, the measuring device 417 stores a data table in which the detection value indicated by the strain detection signal of the strain gauge 416 on the long axis side of the vibration generating body 30A is associated with the torque value, and thus the torque value can be acquired by referring to the data table. In addition, the measuring device 417 can acquire the torque value by calculation from the detection value of each strain gauge 416 without using the data table.

[0077] Since each strain gauge 416 performs the first detection and the second detection in which the amount of strain generated is smaller than that of the first detection, according to the rotation angle of the vibration generating body 30A, the measuring device 417 corrects (temperature compensates) the variation in the detection value of the first detection due to external disturbance (ambient temperature) from the detection value of the second detection performed by the other strain gauge 416 when each strain gauge 416 performs the first detection.

[0078] Here, the other strain gauge 416 that performs the second detection is preferably one in which the amount of strain (amount of state) generated is smaller than that of the strain gauge 416 that performs the first detection, and the ambient temperature is substantially the same as that of the strain gauge 416 that performs the first detection. This can be achieved by adjusting the arrangement of the strain gauge 416 that performs the first detection and the other strain gauge 416 that performs the second detection, or the detection timing of the strain gauge 416 that performs the first detection and the other strain gauge 416 that performs the second detection.

[0079] In this first embodiment, an example in which the adjustment of the arrangement of the strain gauge 416 that performs the first detection and the strain gauge 416 that performs the second detection is implemented is described.

[0080] Figure 3 (A) is a circuit diagram of a Wheatstone bridge circuit 61 in which two strain gauges 416 are arranged diagonally, Figure 3 (B) is an equivalent circuit diagram thereof.

[0081] The Wheatstone bridge circuit 61 has first to fourth paths 611 to 614. Also, one end portion of the first path 611 and one end portion of the third path 613 are connected to the positive side of a voltage supply source. Also, one end portion of the second path 612 and one end portion of the fourth path 614 are connected to the negative side (ground side) of the voltage supply source.

[0082] Further, the Wheatstone bridge circuit 61 has a junction of the other end of the first path 611 and the other end of the second path 612 and a junction of the other end of the third path 613 and the other end of the fourth path 614, and the measuring device 417 detects a potential difference between these two junctions as a strain detection signal.

[0083] The measuring device 417 has two sets of the Wheatstone bridge circuit 61 in which two strain gauges 416 are assembled in a non-diagonal configuration.

[0084] In the present embodiment, for example, the strain gauge 416-1 and the strain gauge 416-2 are assembled in one of the Wheatstone bridge circuits 61, and the strain gauge 416-3 and the strain gauge 416-4 are assembled in the other of the Wheatstone bridge circuits 61. Alternatively, the two strain gauges 416 can be in other combinations in a non-diagonal configuration.

[0085] In Figure 3 The Wheatstone bridge circuit 61 composed of the combination of the strain gauges 416-1 and 416-2 is illustrated in (A) in FIG. 6, and the Wheatstone bridge circuit 61 composed of the combination of the strain gauges 416-1 and 416-2 is described, and the other of the Wheatstone bridge circuits 61 is omitted from the description.

[0086] The description of the other of the Wheatstone bridge circuits 61 can be replaced with the strain gauges 416-3 and 416-4 in the following description, respectively.

[0087] In the above-described Wheatstone bridge circuit 61, the strain gauge 416-1 is provided on the first path 611, the strain gauge 416-2 is provided on the second path 612, and the resistors R1 and R2 are provided on the third path 613 and the fourth path 614, respectively.

[0088] The resistors R1 and R2 are equal to the resistance value of the strain gauge 416 in a state in which no strain is generated at normal temperature (for example, 20 [°C]).

[0089] As Figure 3 As illustrated in the equivalent circuit diagram of (B) in FIG. 6, in the Wheatstone bridge circuit 61, the strain gauges 416-1 and 416-2 connected in series and the resistors R1 and R2 connected in series are connected in parallel between the positive side and the negative side of the voltage supply source.

[0090] Further, the measuring device 417 acquires a potential difference between the strain gauges 416-1 and 416-2 and between the resistors R1 and R2 as an output voltage e (a strain detection signal).

[0091] When the supply voltage from the voltage supply source is set to E and the resistance values of the strain gauges 416-1, 416-2, the resistor Rl, and the resistor R2 are set to εl to ε4, respectively, the output voltage e becomes the following equation (1).

[0092] e = (K / 4) · (εl - ε2 - ε3 + ε4) · E... (1)

[0093] In addition, K is a strain coefficient, which is generally set to about 2.0.

[0094] Since ε3 = ε4, the output voltage e becomes the following equation (2), and becomes a value that is proportional to the difference between the resistance values (outputs) of the strain gauges 416-1 and 416-2.

[0095] e = (K / 4) · (εl - ε2) · E... (2)

[0096] The characteristics of the resistance values of the strain gauges 416 corresponding to the strain vary depending on the ambient temperature, and thus in order to accurately detect the strain, temperature compensation corresponding to the ambient temperature at the time of detection needs to be performed.

[0097] As described above, the flexure engagement type gear device 1 mainly generates heat from the engaged portions of the first inner tooth portion 411 and the first outer tooth portion 32 and the engaged portions of the second inner tooth portion 421 and the second outer tooth portion 33, and in the first inner tooth member 41, the heat is transmitted from the inner tooth annular portion 412 to the external connecting portion 413. At this time, the plurality of columnar members 415 existing therebetween all transmit heat under the same conditions, and thus the strain gauges 416-1 to 416-4 always become approximately the same ambient temperature.

[0098] Furthermore, the strain gauges 416-1 and 416-2 are arranged diagonally, and thus, for example, when one of the strain gauges 416-1 is located on the long axis side of the rotating vibration generator 30A, the other strain gauge 416-2 is located on the short axis side of the vibration generator 30A. Thus, the strain amount of the columnar member 415 in which the strain gauge 416-2 is provided is sufficiently small compared to the columnar member 415 in which the strain gauge 416-1 is provided. For example, the strain gauge 416-2 is in a state in which the strain is hardly generated.

[0099] That is, at the time of the first detection in which the strain amount (state amount) detected by one of the strain gauges 416-1 located on the long axis side of the vibration generator 30A becomes large, the strain amount (state amount) detected by the other strain gauge 416-2 located on the short axis side is sufficiently small compared to the first detection, that is, the second detection.

[0100] The detection value obtained from the strain gauge 416-1 by the above-mentioned first detection is a value to which a variation value caused by the ambient temperature at that time is added to a value corresponding to the amount of strain generated on the columnar member 415. On the other hand, the detection value obtained from the strain gauge 416-2 at the same time based on the second detection becomes only the variation value caused by the ambient temperature at that time because the amount of strain of the columnar member 415 is sufficiently small.

[0101] As described above, the Wheatstone bridge circuit 61 outputs an output voltage e that is proportional to the difference between the resistance values (outputs) of the strain gauge 416-1 and the strain gauge 416-2. Therefore, the output voltage e detected when the strain gauge 416-1 is located on the long axis side becomes a value obtained by subtracting the variation value caused by the ambient temperature from the value corresponding to the amount of strain generated on the columnar member 415 (a detection value that has been temperature-compensated).

[0102] In addition, the strain gauge 416-1 and the strain gauge 416-2 are arranged non-diagonally, and therefore, when the strain gauge 416-2 is located on the long axis side and the first detection is performed, the strain gauge 416-1 is located on the short axis side and the second detection is performed, and therefore, the detection value of the strain gauge 416-2 can also be temperature-compensated.

[0103] Also, as for the strain gauge 416-3 and the strain gauge 416-4, since the same Wheatstone bridge circuit 61 is also configured, the strain detection can also be performed while being temperature-compensated.

[0104] [Technical Effects of the First Embodiment]

[0105] The above-mentioned sensor device 60 has the Wheatstone bridge circuit 61 that acquires a detection value based on the first detection when the amount of strain on the columnar member 415 is large and a detection value based on the second detection in which the strain is small compared to the first detection, and corrects the detection value of the first detection based on the detection value of the second detection, and therefore, it is possible to suppress the influence of the temperature change that becomes external disturbance when the strain is detected, and thus it is possible to perform the strain detection with higher accuracy. Also, since the strain can be detected with higher accuracy, it is also possible to detect the torque of the flexo-mesh gear device 1 with higher accuracy.

[0106] Also, in the Wheatstone bridge circuit 61 of the sensor device 60, different strain gauges 416 are used (for example, the first detection and the second detection are performed by the strain gauge 416-1 and the strain gauge 416-2 in the example of (A) in FIG. 10). Figure 3

[0107] Therefore, it is possible to simultaneously perform the first detection and the second detection, and therefore, it is possible to achieve the shortening of the entire time of the measurement process.

[0108] ​Further, in a case where the sensor device 60 sequentially performs the first detection and the second detection in association with the rotational operation of the flexspline device 1 using a plurality of strain gauges 416, the strain is detected using the strain gauge 416 (for example, 416-1) that performs the first detection, and correction is performed based on the detection of the strain gauge 416 (for example, 416-2) that performs the second detection at the same time.

[0109] Therefore, the strain detection in association with the temperature compensation can be performed without preparing a dedicated strain gauge (temperature compensation strain gauge) for the correction, and thus the number of necessary strain gauges 416 can be reduced.

[0110] Further, it is not necessary to secure a space for disposing the temperature compensation strain gauge, and thus miniaturization of the object device can be achieved.

[0111] Further, the flexspline device 1 as the object device is a rotational device that performs a rotational operation, and the sensor device 60 performs the first detection and the second detection in association with the rotational operation of the flexspline device 1, and thus the strain detection in association with the temperature compensation can be continuously performed in the rotational operation.

[0112] In particular, since the object device is the flexspline device 1, the long axis position of the vibration generator 30A rotates, and thus the strain detection in association with the temperature compensation can be periodically and continuously performed in association with the rotational operation by disposing a plurality of strain gauges 416 around the long axis position.

[0113] In addition, the Wheatstone bridge circuit 61 is exemplified as the correction unit, but the correction unit is not limited to the Wheatstone bridge circuit, and other circuits or the like that can perform correction such as subtraction of a detection value of a strain detection signal of the strain gauge 416 that performs the second detection from a detection value of a strain detection signal of the strain gauge 416 that performs the first detection can be used as the correction unit.

[0114] [Second Embodiment]

[0115] Figure 4 is a front view of the first inner tooth member 41D of the flexspline device 1 to which the sensor device according to the second embodiment of the present application is applied.

[0116] In the above-described first embodiment, the structure in which four strain gauges 416 are disposed at equal intervals in the circumferential direction is exemplified, but the number of strain gauges 416 is not limited to the above, and can be an odd number.

[0117] For example, as shown in Figure 4 seven columnar members 415 can be provided, and the strain gauges 416-1 to 416-7 can be respectively provided on the columnar members 415.

[0118] In the case of adopting the above configuration, for example, in a state where the strain gauge 416-1 is located on the long axis side of the oscillation body 30A, the strain gauges 416-2, 416-3, 416-6, and 416-7 that are not diagonally arranged with the strain gauge 416-1 become the short axis side. That is, when the strain gauge 416-1 is located on the long axis side and detects a large strain amount, the strain gauges 416-2, 416-3, 416-6, and 416-7 are located on the short axis side and the detected strain amount becomes sufficiently small. Therefore, when the detection value based on the first detection is acquired based on the strain gauge 416-1, it is preferable to acquire the detection value based on the second detection from any one of the above-described strain gauges 416-2, 416-3, 416-6, and 416-7.

[0119] For example, with respect to each strain gauge 416, by configuring a Wheatstone bridge circuit 61 constituted by the strain gauge 416 and the other strain gauges 416 that are not diagonally arranged, even in the case where the number of mounted strain gauges 416 differs like the first inner tooth member 41D, the same strain detection as the first inner tooth member 41 can be performed.

[0120] In addition, in the second embodiment, instead of the Wheatstone bridge circuit as the correction unit, another circuit or the like that can perform correction such as subtracting the detection value of the strain detection signal of the strain gauge 416 that performs the second detection from the detection value of the strain detection signal of the strain gauge 416 that performs the first detection can be used as the correction unit.

[0121] [Third Embodiment]

[0122] Figure 5 is a perspective view of the first inner tooth member 41E of the flexspline type gear device 1 to which the sensor device according to the third embodiment of the present application is applied.

[0123] In the above-described first inner tooth member 41, the easily deformable portion 414 is constituted by four columnar members 415 that are discontinuously arranged in the circumferential direction, but is not limited thereto.

[0124] In the first inner tooth member 41E, the easily deformable portion 414E is formed by a ring-shaped flat plate that is continuous in the circumferential direction between the inner tooth ring portion 412 and the outer linking portion 413.

[0125] However, as shown in the axial cross-sectional view of Figure 6 the easily deformable portion 414E, the axial thickness d3 is set to be smaller than both the axial thickness d1 of the inner tooth ring portion 412 and the axial thickness d2 of the outer linking portion 413.

[0126] Furthermore, a plurality of strain gauges 416 are mounted on any one of the flat surfaces in the easily deformable portion 414E at equal intervals in the circumferential direction. Here, a case where four strain gauges 416 are provided is exemplified. In addition, the number of strain gauges 416 is not limited to four, and the number of strain gauges 416 can be increased or decreased.

[0127] Each of the strain gauges 416 is installed in a direction to detect a tensile strain in the radial direction.

[0128] Thus, in the first inner tooth member 41E, the easily deformable portion 414E is provided in a flat plate shape continuously in the circumferential direction, and the axial thickness d3 thereof is set to be smaller than the axial thickness d1 of the inner tooth annular portion 412 and the axial thickness d2 of the outer linking portion 413. Therefore, when the flexion engagement type gear device performs torque transmission, the easily deformable portion 414E is more easily deformed than the inner tooth annular portion 412, and as a result, a tensile strain is also easily generated in the radial direction, and thus, higher-precision torque detection can be performed as with the easily deformable portion 414. In addition, the axial thickness d3 of the easily deformable portion 414E only needs to be at least smaller than the axial thickness d1 of the inner tooth annular portion 412, and can be the same as or larger than the axial thickness d2 of the outer linking portion 413.

[0129] In addition, the easily deformable portion 414E is made to be easily deformed by being provided with a thin thickness, but can be formed of a softer metal material or a softer resin material than the other portions (the inner tooth annular portion 412, the outer linking portion 413) without changing the thickness thereof.

[0130] Furthermore, in the first to third embodiments, the easily deformable portion 414, 414E is provided on the first inner tooth member 41, 41D, 41E, but this is not necessarily required.

[0131] A plurality of strain gauges 416 can be provided at a plurality of locations on the first inner tooth member on which a strain is generated based on the rotational motion of the flexion engagement type gear device 1 and the same temperature is transmitted.

[0132] [Fourth Embodiment]

[0133] Figure 7 is a front view showing the first inner tooth member 41F of the flexion engagement type gear device 1 to which the sensor device according to the fourth embodiment of the present application is applied.

[0134] The sensor device 60 provided on the above-described first inner tooth member 41 is configured such that each of the strain gauges 416 provided at equal intervals in the circumferential direction performs the first detection when located on the long axis side of the vibration generator 30A, and the other strain gauges 416 in a non-diagonal arrangement located on the short axis side at the same time perform the second detection.

[0135] That is, all of the strain gauges 416 provided on the first inner tooth member 41 perform the first detection and the second detection, and there is no strain gauge that is exclusively provided to perform only the second detection.

[0136] In contrast, the sensor device according to the fourth embodiment includes a dedicated strain gauge 416a that performs only the second detection without performing the first detection (detection of the state quantity). The strain gauge 416a is a strain gauge that has the same structure, characteristics, and performance as the strain gauges 416.

[0137] The first inner tooth member 41F has a columnar member 415a that extends from the outer periphery of the inner tooth ring 412 toward the radial direction outer side like the columnar member 415, and the extending end portion of which does not contact the external connecting portion 413, and the strain gauge 416a is provided on the columnar member 415a.

[0138] The columnar member 415a is configured to have the same material as the columnar member 415 and the same width and thickness, and thus transmits the same degree of temperature as the columnar member 415. On the other hand, the columnar member 415a does not contact the external connecting portion 413, and thus has a structure in which strain does not occur even on the long axis side of the vibration body 30A when the flexspline gear device 1 performs a rotational operation.

[0139] By mounting the strain gauge 416a on the columnar member 415a, the strain gauge 416a can perform the second detection in an environment temperature that is almost the same as the other strain gauges 416 and in a state in which the influence of the strain change caused by the rotational operation of the flexspline gear device 1 is almost excluded.

[0140] Further, when the flexspline gear device 1 performs a rotational operation, the sensor device according to the fourth embodiment performs temperature compensation by subtracting the detection value of the strain detection signal based on the second detection of the strain gauge 416a from the detection value of the strain detection signal based on the first detection of the strain gauge 416 on the long axis side of the vibration body 30A, and thus can accurately detect strain.

[0141] In this case, the connection of the strain gauge 416a is switched by the Wheatstone bridge connection at the time of the first detection by each strain gauge 416, and thus each strain gauge 416 and the strain gauge 416a constitute the Wheatstone bridge circuit 61.

[0142] Alternatively, software processing can be performed in which, if each strain gauge 416 performs the first detection, the detection value of the first detection is corrected (subtracted) based on the detection value of the second detection of the strain gauge 416a.

[0143] [Fifth Embodiment]

[0144] Figure 8 is a front view of the first inner tooth member 41G of the flexspline gear device 1 to which the sensor device 60G according to the fifth embodiment of the present application is applied.

[0145] In the sensor device 60 described above, the first detection and the second detection are performed by different strain gauges 416, and the strain detection with temperature compensation is performed based on the detection values of the strain detection signals based on each strain detection.

[0146] In contrast, in the sensor device 60G, each strain gauge 416 performs the first detection when positioned on the long axis side of the vibration generating body 30A, and performs the second detection when positioned on the short axis side by the rotation of the vibration generating body 30A, and the temperature compensation is performed by subtracting the detection value of the strain detection signal based on the second detection performed by the same strain gauge 416 from the detection value of the strain detection signal based on the first detection performed by the strain gauge 416.

[0147] Therefore, the sensor device 60G does not use the Wheatstone bridge circuit 61 that performs the strain detection and the temperature compensation at the same time as the correction section.

[0148] The sensor device 60G has a plurality of processing circuits 418 for detecting the resistance value connected to each strain gauge 416, and a measuring device 417G as the correction section connected to each processing circuit 418.

[0149] Further, the measuring device 417G further has a storage section that stores the detection value of the strain detection signal at the time of the first detection and the detection value of the strain detection signal at the time of the second detection for each strain gauge 416. Further, if the most recent detection value at the time of the first detection and the most recent detection value at the time of the second detection for each strain gauge 416 are prepared in the storage section, the measuring device 417G calculates the detection value of the strain with temperature compensation for each strain gauge 416.

[0150] In the sensor device 60G of the fifth embodiment described above, each strain gauge 416 performs the first detection and the second detection in an arbitrary order, and performs the strain detection with temperature compensation for each strain gauge 416 based on the detection value based on the first detection and the detection value based on the second detection acquired by the same strain gauge 416.

[0151] Therefore, it is not necessary to provide a dedicated strain gauge for performing the second detection, and it is not necessary to prepare a pair of the strain gauge 416 for performing the first detection and the other strain gauge 416 for performing the second detection, and thus it is possible to achieve the simplification of the structure, the ease of manufacturing, the reduction in the number of components, and the like.

[0152] Further, when a plurality of strain gauges 416 are provided, it is not necessary to select a configuration in which the ambient temperatures of the strain gauges 416 become equal, and thus it is possible to ensure the degree of freedom in design.

[0153] Further, as long as the above-described structure, it is possible to reduce the strain gauges 416 to one.

[0154] Further, the flexspline gear device 1 as the target device performs the first detection when each strain gauge 416 is positioned on the long axis side of the vibration body 30A, and performs the second detection when positioned on the short axis side, and performs the strain detection with temperature compensation based on the detection values thereof.

[0155] As described above, the sensor device 60G can particularly well perform the strain detection in the flexspline gear device 1 in which each strain gauge 416 easily obtains the opportunity to periodically perform the first detection and the second detection.

[0156] [Others]

[0157] The fine portions shown in each of the above embodiments can be appropriately changed within the scope of the gist of the present application.

[0158] For example, in the sensor device of each of the above embodiments, as the target device, the description has been made taking the case of the cylindrical flexspline gear device, but it can be well applied to flexspline gear devices other than the cylindrical one, such as a cup type or a top hat type, and the like.

[0159] Further, in the sensor device of each of the embodiments, as the target device, it is not limited to the flexspline gear device, but can be applied to other devices that perform various actions such as a rotation action or a linear action, such as a motor, a linear motor, a ball screw device, an injection molding machine, and the like. At this time, in the case of adopting a structure having a plurality of strain gauges, it is preferable to arrange a plurality of strain gauges around a member that performs a rotation action or to arrange a plurality of strain gauges in the action range of a member that performs a linear action.

[0160] Further, as the detection unit, the strain gauge is exemplified, but it is not limited thereto, and the structure of the above sensor device can be applied to all sensors that need to be corrected such as temperature compensation. As the detection unit other than the strain gauge, for example, a magnetic sensor or a vibration sensor, and the like can be exemplified.

[0161] Further, in the embodiment, the correction is performed by subtracting the detection value of the second detection from the detection value of the first detection, but as long as the detection value of the first detection is corrected based on the detection value of the second detection, the correction method is not particularly limited. For example, it can be subtracted from the detection value of the first detection after multiplying the detection value of the second detection by a prescribed coefficient.

Claims

1. A sensor device for detecting a specified strain, characterized in that, The sensor device has: a detection section that performs a first detection and a second detection that produces a smaller amount of strain than the first detection, a correction section that corrects a detection value of the first detection based on a detection value of the second detection, a plurality of the detection sections perform the first detection and the second detection in conjunction with an action of an object device, the object device is a flexspline gear device that has a generally elliptical shape with a shaft right angle cross section, the first detection is performed by a detection section on a long axis side of the oscillation body, and the second detection is performed by a detection section on a short axis side of the oscillation body.

2. The sensor device according to claim 1, further comprising: a rotation detection device that detects a rotation angle of the oscillation body.

3. The sensor device according to claim 1 or 2, wherein: the plurality of detection sections include two strain gauges that are not diagonally arranged.

4. The sensor device according to claim 3, wherein: two sets of Wheatstone bridge circuits are provided that assemble the two strain gauges that are not diagonally arranged.

5. The sensor device according to claim 4, wherein: a first strain gauge is provided on one of two columnar members that are provided on both end portions in a diameter direction, and a third strain gauge is provided on the other of the two columnar members, a second strain gauge is provided on one of two columnar members that are provided on both end portions in another diameter direction that is orthogonal to the diameter direction, and a fourth strain gauge is provided on the other of the two columnar members, the first strain gauge and the second strain gauge are assembled in one of the two sets of Wheatstone bridge circuits, and the third strain gauge and the fourth strain gauge are assembled in the other of the two sets of Wheatstone bridge circuits.

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