Patent ID: 12196306

DETAILED DESCRIPTION

Hereinafter, an example embodiment of the present application will be described with reference to the drawings.

FIG.1is a schematic view of a robot100equipped with a wave reducer1according to one example embodiment. For example, the robot100is what is called an industrial robot that performs operations such as conveyance, processing, and assembly of components in a manufacturing line of an industrial product. As shown inFIG.1, the robot100includes a base frame101, an arm102, a motor103, and the wave reducer1.

The arm102is pivotally supported with respect to the base frame101. The motor103and the wave reducer1are incorporated in a joint between the base frame101and the arm102. When a drive current is supplied to the motor103, a rotational motion is output from the motor103. The rotational motion output from the motor103is decelerated by the wave reducer1and transmitted to the arm102. Due to this, the arm102pivots with respect to the base frame101at a speed after deceleration.

As described above, the robot100includes the wave reducer1. As described below, since a first terminal43and a second terminal44of the wave reducer1are arranged at circumferentially different positions, the probability that a load is applied at the same time is low. Therefore, for example, even if one of the first terminal43and the second terminal44no longer functions, the probability that the other terminal functions is high. This makes it possible to achieve the robot100having a high reliability.

Subsequently, a detailed structure of the wave reducer1will be described.

Hereinafter, a direction parallel to a central axis9of the wave reducer1is referred to as “axial”, a direction orthogonal to the central axis9of the wave reducer1is referred to as “radial”, and a direction along an arc about the central axis9of the wave reducer1is referred to as “circumferential”. The “parallel” mentioned above includes “substantially parallel”. The “orthogonal” mentioned above includes “substantially orthogonal”.

FIG.2is a longitudinal cross-sectional view of the wave reducer1according to one example embodiment.FIG.3is a transverse cross-sectional view of the wave reducer1viewed from A-A position inFIG.2. To avoid complication of the drawings, hatching that indicates a cross section is not shown inFIG.3. The wave reducer1is a device that decelerates a rotational motion at a first rotational speed obtained from the motor103to a second rotational speed slower than the first rotational speed. The wave reducer1includes an internally toothed gear10, an annular body20, and a wave generator30.

As described below, in the wave reducer1, the first terminal43and the second terminal44are arranged at circumferentially different positions. Therefore, there is a low probability that a load is simultaneously applied to the first terminal43and the second terminal44. Therefore, for example, even if one of the first terminal43and the second terminal44no longer functions, the probability that the other terminal functions is high. This makes it possible to achieve the wave reducer1having a high reliability.

The internally toothed gear10is an annular gear about the central axis9. The internally toothed gear10is fixed to the arm102. The internally toothed gear10meshes with the annular body20. The internally toothed gear10is arranged radially outside an external tooth22described below. Rigidity of the internally toothed gear10is sufficiently higher than rigidity of a body21described below of the annular body20. For this reason, the internally toothed gear10can be regarded as a substantially rigid body. The internally toothed gear10has a plurality of internal teeth11. The plurality of internal teeth11protrude radially inward from a radially inner surface of the internally toothed gear10. The plurality of internal teeth11are arrayed at a constant pitch in the circumferential direction on an inner periphery of the internally toothed gear10.

The annular body20is an annular gear that is flexurally deformable. The annular body20is fixed to the base frame101. The annular body20is supported rotatably about the central axis9. As shown inFIGS.2and3, the annular body20has a base23. The annular body20of the present example embodiment further includes the body21, a plurality of the external teeth22, and a thick part24.

The body21is a tubular part extending in a direction including an axial component from a radial end of the base23described below. In the present example embodiment, one axial end of the body21is connected to the base23. The body21extends from the radially inner end of the base23toward the other axial side. The end on the other axial side of the body21is positioned radially outside the wave generator30and radially inside the internally toothed gear10. Since the body21has flexibility, the body21is radially deformable. In particular, the other axial end of the body21is radially displaceable more than another part.

The plurality of external teeth22protrude radially outward from a radially outer surface of the body21. The plurality of external teeth22are arranged on the radially outer surface of the other axial end of the body21. The plurality of external teeth22are arrayed at a constant pitch in the circumferential direction. A part of the plurality of external teeth22and a part of a plurality of the internal teeth11described above mesh with each other. The number of the internal teeth11included in the internally toothed gear10is slightly different from the number of the external teeth22included in the annular body20.

The base23surrounds the central axis9and expands in a direction intersecting the central axis9. The base23preferably extends along a plane orthogonal to the central axis9. The base23expands radially outward from an end on one axial side of the body21. The base23has an annular shape surrounding the central axis9. Since the base23is thin, it is slightly flexurally deformable.

The thick part24is an annular part positioned radially outside the base23. The thick part24further expands radially outward from the radially outer end of the base23. The axial thickness of the thick part24is larger than the axial thickness of the base23. The thick part24is fixed to the base frame101with, for example, a bolt.

The wave generator30is a mechanism that generates flexural deformation in the annular body20. The wave generator30is arranged radially inside the external teeth22. The wave generator30of the present example embodiment includes a cam31and a flexible bearing32. The cam31is supported rotatably about the central axis9. A radially outer surface of the cam31has an elliptical shape when viewed in the axial direction. The flexible bearing32is a flexurally deformable bearing. The flexible bearing32is arranged between the radially outer surface of the cam31and the radially inner surface of the body21of the annular body20. Accordingly, the cam31and the body21can rotate at different rotational speeds.

An inner ring of the flexible bearing32comes into contact with the radially outer surface of the cam31. An outer ring of the flexible bearing32comes into contact with the radially inner surface of the body21. For this reason, the body21is deformed in an elliptical shape along the radially outer surface of the cam31. As a result, the external teeth22of the annular body20and the internal teeth11of the internally toothed gear10mesh with each other at two location corresponding to both ends of a major axis of the ellipse. At other circumferential positions, the external teeth22and the internal teeth11do not mesh with each other.

The cam31is connected to an output shaft (not illustrated) of the motor103. When the motor103is driven, the cam31rotates at the first rotational speed about the central axis9. Due to this, the major axis of the above-described ellipse of the annular body20also rotates at the first rotational speed. Then, the meshing position between the external teeth22and the internal teeth11also changes at the first rotational speed in the circumferential direction. As described above, the number of the internal teeth11of the internally toothed gear10is slightly different from the number of the external teeth22of the annular body20. Due to this difference in the number of teeth, the meshing position between the external teeth22and the internal teeth11slightly changes in the circumferential direction every rotation of the cam31. As a result, the annular body20rotates about the central axis9with respect to the internally toothed gear10at the second rotational speed slower than the first rotational speed.

The annular body20includes a torque sensor40. The torque sensor40is a sensor for detecting torque applied to the base23. As shown inFIG.2, the torque sensor40includes a first substrate41. That is, the annular body20includes the first substrate41. The first substrate41is fixed to the base23. The base23has a surface231that intersects the central axis9and expands in an annular shape about the central axis9. The surface231is a plane on one axial side of the base23. The first substrate41is fixed to the surface231of the base23.

FIG.4is a partial longitudinal cross-sectional view of the annular body20near the first substrate41.FIG.5is a plan view of the first substrate41. As shown inFIGS.4and5, the first substrate41includes an insulating layer411and a resistance wire412.

The insulating layer411is a flexibly deformable. The insulating layer411expands in a direction intersecting the central axis9. The insulating layer411has an annular shape about the central axis9. The insulating layer411is made from resin that is an insulator or an inorganic insulating material. The insulating layer411is arranged on the surface231of the base23.

The resistance wire412is formed on a surface of the insulating layer411. That is, the resistance wire412is arranged on the base23. A conductive metal is used as a material of the resistance wire412. For example, a copper alloy, a chromium alloy, or copper is used as a material of the resistance wire412. The resistance wire412includes a first resistance wire portion W1and a second resistance wire portion W2. That is, the annular body20includes the first resistance wire portion W1and the second resistance wire portion W2. The resistance values of the first resistance wire portion W1and the second resistance wire portion W2change in accordance with the strain of the base23.

The first resistance wire portion W1and the second resistance wire portion W2are arranged on a plane on one axial side of the base23. In the present example embodiment, the first resistance wire portion W1and the second resistance wire portion W2are arranged on a plane on one axial side of the first substrate41. The second resistance wire portion W2is arranged radially outside relative to the first resistance wire portion W1. By arranging the first resistance wire portion W1and the second resistance wire portion W2on one surface of the base23as described above, it becomes easy to wire the first resistance wire portion W1and the second resistance wire portion W2.

The first resistance wire portion W1includes an inner first resistance wire portion W11and an outer first resistance wire portion W12. The outer first resistance wire portion W12is arranged radially outside relative to the inner first resistance wire portion W11.

The inner first resistance wire portion W11has a plurality of first regions Ra and Rb. The plurality of first regions Ra and Rb are arranged at intervals in the circumferential direction. In the present example embodiment, the inner first resistance wire portion W11has two of the first regions Ra and Rb. Each of the two first regions Ra and Rb is provided in a semicircular arc shape in a range of about 180° about the central axis9. The two first regions Ra and Rb are arranged concentrically and line-symmetrically. The radial distance from the central axis9to the first region Ra is substantially equal to the radial distance from the central axis9to the first region Rb.

FIG.6is a partial plan view of the first substrate41. As shown inFIG.6, each of the plurality of first regions Ra and Rb includes a region in which a first site r1extending in a direction having both radial and circumferential components is repeatedly arranged in the circumferential direction. Specifically, the two first regions Ra and Rb each extend in the circumferential direction with one conductive wire bent in a zigzag manner. A plurality of the first sites r1are arrayed circumferentially in a posture substantially parallel to each other. The first site r1of the first region Ra, which is one of the two first regions Ra and Rb, is inclined to one circumferential side with respect to the radial direction. The first site r1of the first region Rb, which is the other, is inclined to the other circumferential side with respect to the radial direction. The inclination angle of the first site r1with respect to the radial direction is 45°, for example. Ends of the first sites r1adjacent circumferentially to each other are alternately connected radially inside or radially outside. Thus, the plurality of first sites r1are connected in series as a whole.

The outer first resistance wire portion W12has a plurality of first regions Rc and Rd. The plurality of first regions Rc and Rd are arranged at intervals in the circumferential direction. In the present example embodiment, the outer first resistance wire portion W12has two of the first regions Rc and Rd. Each of the two first regions Rc and Rd is provided in a semicircular arc shape in a range of about 180° about the central axis9. The two first regions Rc and Rd are arranged concentrically and line-symmetrically. The radial distance from the central axis9to the first region Rc is substantially equal to the radial distance from the central axis9to the first region Rd.

As shown inFIG.6, each of the plurality of first regions Rc and Rd includes a region in which the first site r1extending in a direction having both radial and circumferential components is repeatedly arranged in the circumferential direction. Specifically, the two first regions Rc and Rd each extend in the circumferential direction with one conductive wire bent in a zigzag manner. A plurality of the first sites r1are arrayed circumferentially in a posture substantially parallel to each other. The first site r1of the first region Rc, which is one of the two first regions Rc and Rd, is inclined to the other circumferential side with respect to the radial direction. The first site r1of the first region Rd, which is the other, is inclined to one circumferential side with respect to the radial direction. The inclination angle of the first site r1with respect to the radial direction is 45°, for example. Ends of the first sites r1adjacent circumferentially to each other are alternately connected radially inside or radially outside. Thus, the plurality of first sites r1are connected in series as a whole.

The second resistance wire portion W2includes an inner second resistance wire portion W21and an outer second resistance wire portion W22. The outer second resistance wire portion W22is arranged radially outside relative to the inner second resistance wire portion W21.

The inner second resistance wire portion W21has a plurality of second regions Re and Rf. The plurality of second regions Re and Rf are arranged at intervals in the circumferential direction. In the present example embodiment, the inner second resistance wire portion W21has two of the second regions Re and Rf. Each of the two second regions Re and Rf is provided in a semicircular arc shape in a range of about 180° about the central axis9. The two second regions Re and Rf are arranged concentrically and line-symmetrically. The radial distance from the central axis9to the second region Re is substantially equal to the radial distance from the central axis9to the second region Rf.

As shown inFIG.6, each of the plurality of first regions Re and Rf includes a region in which a second site r2extending in a direction having both radial and circumferential components is repeatedly arranged in the circumferential direction. Specifically, the two second regions Re and Rf each extend in the circumferential direction with one conductive wire bent in a zigzag manner. A plurality of the second site r2are arrayed circumferentially in a posture substantially parallel to each other. The second site r2of the second region Re, which is one of the two second regions Re and Rf, is inclined to one circumferential side with respect to the radial direction. The second site r2of the second region Rf, which is the other, is inclined to the other circumferential side with respect to the radial direction. The inclination angle of the second site r2with respect to the radial direction is 45°, for example. Ends of the second sites r2adjacent circumferentially to each other are alternately connected radially inside or radially outside. Thus, the plurality of second sites r2are connected in series as a whole.

The outer second resistance wire portion W22has a plurality of second regions Rg and Rh. The plurality of second regions Rg and Rh are arranged at intervals in the circumferential direction. In the present example embodiment, the outer second resistance wire portion W22has two of the second regions Rg and Rh. Each of the two second regions Rg and Rh is provided in a semicircular arc shape in a range of about 180° about the central axis9. The two second regions Rg and Rh are arranged concentrically and line-symmetrically. The radial distance from the central axis9to the second region Rg is substantially equal to the radial distance from the central axis9to the second region Rh.

As shown inFIG.6, each of the plurality of first regions Rg and Rh includes a region in which the second site r2extending in a direction having both radial and circumferential components is repeatedly arranged in the circumferential direction. Specifically, the two second regions Rg and Rh each extend in the circumferential direction with one conductive wire bent in a zigzag manner. A plurality of the second site r2are arrayed circumferentially in a posture substantially parallel to each other. The second site r2of the second region Rg, which is one of the two second regions Rg and Rh, is inclined to the other circumferential side with respect to the radial direction. The second site r2of the second region Rh, which is the other, is inclined to one circumferential side with respect to the radial direction. The inclination angle of the second site r2with respect to the radial direction is 45°, for example. Ends of the second sites r2adjacent circumferentially to each other are alternately connected radially inside or radially outside. Thus, the plurality of second sites r2are connected in series as a whole.

FIG.7is a circuit diagram of a first bridge circuit C1including four of the first regions Ra, Rb, Rc, and Rd of the first resistance wire portion W1. As shown inFIGS.6and7, the first resistance wire portion W1has a first connection region W13connected to the four first regions Ra, Rb, Rc, and Rd. The four first regions Ra, Rb, Rc, and Rd are connected via the first connection region W13. Thus, the first bridge circuit C1is formed.

The first region Ra and the first region Rb are connected in series in this order. The first region Rc and the first region Rd are connected in series in this order. Then, the row of the two first regions Ra and Rb and the row of the two first regions Rc and Rd are connected in parallel between a + pole and a − pole of a power source voltage. A middle point M11between the two first regions Ra and Rb and a middle point M12between the two first regions Rc and Rd are connected to a first voltmeter V1.

A resistance value of each of the first sites r1changes in accordance with torque applied to the region where the resistance wire412is arranged. That is, in the present example embodiment, the resistance value of each of the first sites r1of the four first regions Ra, Rb, Rc, and Rd changes in accordance with the torque applied to the base23. For example, when the base23is applied with torque toward one circumferential side about the central axis9, the resistance value of each of the first sites r1of the two first regions Ra and Rd decreases, and the resistance value of each of the first sites r1of the other two first regions Rb and Rc increases. On the other hand, when the base23is applied with torque toward the other circumferential side about the central axis9, the resistance value of each of the first sites r1of the two first regions Ra and Rd increases, and the resistance value of each of the first sites r1of the other two first regions Rb and Rc decreases. As described above, the two first regions Ra and Rd and the two first regions Rb and Rc show resistance value changes reversely to each other with respect to the torque.

When the resistance value of each of the four first regions Ra, Rb, Rc, and Rd changes, a potential difference between the middle point M11of the two first regions Ra and Rb and the middle point M12of the two first regions Rc and Rd changes, and thus a measurement value of the first voltmeter V1also changes. Therefore, the orientation and the magnitude of the torque applied to the base23can be detected based on the measurement value of the first voltmeter V1.

FIG.8is a circuit diagram of a second bridge circuit C2including four of the second regions Re, Rf, Rg, and Rh of the second resistance wire portion W2. As shown inFIGS.6and8, the second resistance wire portion W2has a second connection region W23connected to four second regions Re, Rf, Rg, and Rh. In the present example embodiment, the four second regions Re, Rf, Rg, and Rh are connected via the second connection region W23. Thus, the second bridge circuit C2is formed.

The second region Re and the second region Rf are connected in series in this order. The second region Rg and the second region Rh are connected in series in this order. Then, the row of the two second regions Re and Rf and the row of the two second regions Rg and Rh are connected in parallel between the + pole and the − pole of the power source voltage. A middle point M21between the two second regions Re and Rf and a middle point M22between the two second regions Rg and Rh are connected to a second voltmeter V2.

A resistance value of each of the second sites r2changes in accordance with torque applied to the region where the resistance wire412is arranged. In the present example embodiment, the resistance value of each of the second sites r2of the four second regions Re, Rf, Rg, and Rh changes in accordance with the torque applied to the base23. For example, when the base23is applied with torque toward one circumferential side about the central axis9, the resistance value of each of the second sites r2of the two second regions Re and Rh decreases, and the resistance value of each of the second sites r2of the other two second regions Rf and Rg increases. On the other hand, when the base23is applied with torque toward the other circumferential side about the central axis9, the resistance value of each of the second sites r2of the two second regions Re and Rh increases, and the resistance value of each of the second sites r2of the other two second regions Rf and Rg decreases. As described above, the two second regions Re and Rh and the two second regions Rf and Rg show resistance value changes reversely to each other with respect to the torque.

When the resistance value of each of the four second regions Re, Rf, Rg, and Rh changes, a potential difference between the middle point M21of the two second regions Re and Rf and the middle point M22of the two second regions Rg and Rh changes, and thus a measurement value of the second voltmeter V2also changes. Therefore, the orientation and the magnitude of the torque applied to the base23can be detected based on the measurement value of the second voltmeter V2.

As described above, the torque sensor40of the present example embodiment includes two bridge circuits of the first bridge circuit C1and the second bridge circuit C2. Therefore, even when an abnormality occurs in any one of the bridge circuits, the torque can be detected by the other bridge circuit. When an abnormality occurs in any one of the bridge circuits, the abnormality can be detected.

The first bridge circuit C1and the second bridge circuit C2may be connected in parallel to a common power source voltage or may be connected to different power source voltages. That is, different power source voltages may be used for each bridge circuit. In a case where different power source voltages are used for each bridge circuit, even when some of the power source voltages fail to function normally, a normal voltage is supplied from another power source voltage to at least one bridge circuit. Therefore, the torque can be detected by the bridge circuit.

As shown inFIG.5, the torque sensor40includes the first terminal43and the second terminal44. That is, the annular body20has the first terminal43and the second terminal44. The first terminal43and the second terminal44are arranged on the base23. In the present example embodiment, the first terminal43and the second terminal44are arranged on the surface231of the base23. The first terminal43and the second terminal44are formed of a conductive metal.

The first terminal43is electrically connected to the end of the first resistance wire portion W1. The first resistance wire portion W1is electrically connected, via the first terminal43, to a signal processing circuit described below. The second terminal44is electrically connected to the end of the second resistance wire portion W2. The second resistance wire portion W2is electrically connected, via the second terminal44, to the signal processing circuit described below.

The first terminal43is arranged at a first position P1in the circumferential direction. The second terminal44is arranged at a second position P2in the circumferential direction. The first position P1and the second position P2are circumferentially separated from each other. Specifically, a central angle θ formed by the first position P1, the central axis9, and the second position P2is equal to or greater than 90° when viewed in the axial direction. Thus, when the first terminal43and the second terminal44are arranged at circumferentially different positions, it is possible to reduce the probability that a load is simultaneously applied to the first terminal43and the second terminal44, as compared with a case where the first terminal43and the second terminal44are arranged at the same circumferential position. Therefore, for example, even if one of the first terminal43and the second terminal44no longer functions, the probability that the other terminal functions can be increased. Therefore, the torque applied to the base23can be detected by at least any one of the first resistance wire portion W1and the second resistance wire portion W2.

When the circumferential width of at least one of the first terminal43and the second terminal44is wide, the circumferential center of the first terminal43is only required to be the first position P1, and the circumferential center of the second terminal44is only required to be the second position P2. That is, the central angle θ formed by the first position P1, the central axis9, and the second position P2is only required to be defined as a central angle formed by the circumferential center of the first terminal43, the central axis9, and the circumferential center of the second terminal. InFIG.5, a part of an imaginary line connecting the circumferential center of the first terminal43and the central axis9and a part of an imaginary line connecting the second terminal44and the central axis9are each indicated by a broken line. Therefore, the central angle formed by the broken line and the central axis9is equal to the central angle θ.

As shown inFIG.5, in the present example embodiment, the first terminal43extends from the end of the first resistance wire portion W1in a direction away from the central axis9. The second terminal44extends from the end of the second resistance wire portion W2in a direction away from the central axis9. This makes it possible to arrange the first terminal43and the second terminal44at positions further away from each other. This makes it possible to further reduce the probability that a load is simultaneously applied to the first terminal43and the second terminal44. Therefore, for example, even if one of the first terminal43and the second terminal44no longer functions, the probability that the other terminal functions can be further increased.

When viewed in the axial direction, the central angle θ, formed by the first position P1, the central axis9, and the second position P2, is more desirably equal to or greater than 175° and equal to or less than 185°. This makes it possible to arrange the first terminal43and the second terminal44at positions further away from each other. Therefore, it is possible to further reduce the probability that the first terminal43and the second terminal44are simultaneously disconnected. When viewed in the axial direction, the central angle θ, formed by the first position P1, the central axis9, and the second position P2, is only required to be, for example, 180°.

The first resistance wire portion W1and the first terminal43are separate members. That is, the first resistance wire portion W1and the first terminal43are manufactured separately and then electrically connected. This can improve the manufacturing efficiency of the torque sensor40.

Specifically, the torque sensor40includes a first anisotropic conductive film431. That is, the annular body20has the first anisotropic conductive film431. The first anisotropic conductive film431is arranged between the first resistance wire portion W1and the first terminal43. Specifically, the end of the first resistance wire portion W1and the end of the first terminal43are crimped via the first anisotropic conductive film431. Due to this, the end of the first resistance wire portion W1and the end of the first terminal43are fixed and electrically connected. Thus, use of the first anisotropic conductive film431makes it possible to simultaneously perform fixing and electric connection of the first resistance wire portion W1and the first terminal43. This can further improve the manufacturing efficiency of the torque sensor40.

The second resistance wire portion W2and the second terminal44are separate members. That is, the second resistance wire portion W2and the second terminal44are manufactured separately and then electrically connected. This can improve the manufacturing efficiency of the torque sensor40.

Specifically, the torque sensor40includes a second anisotropic conductive film441. That is, the annular body20has the second anisotropic conductive film441. The second anisotropic conductive film441is arranged between the second resistance wire portion W2and the second terminal44. Specifically, the end of the second resistance wire portion W2and the end of the second terminal44are crimped via the second anisotropic conductive film441. Due to this, the end of the second resistance wire portion W2and the end of the second terminal44are fixed and electrically connected. Thus, use of the second anisotropic conductive film441makes it possible to simultaneously perform fixing and electric connection of the second resistance wire portion W2and the second terminal44. This can further improve the manufacturing efficiency of the torque sensor40.

As described above, cyclic flexural deformation occurs in the annular body20when the wave reducer1is driven. Therefore, an output signal of the first resistance wire portion W1and an output signal of the second resistance wire portion W2include a component reflecting torque originally desired to measure and an error component (ripple error) caused by cyclic flexural deformation of the annular body20. The ripple error changes in accordance with the rotation angle of rotational motion input to the annular body20.

Therefore, the torque sensor40of the present example embodiment performs correction processing (ripple correction) for canceling the ripple error. Hereinafter, this ripple correction will be described.

As shown inFIG.5, the resistance wire412of the present example embodiment further includes a third resistance wire portion W3. The third resistance wire portion W3is a resistance wire for detecting the rotation angle of rotational motion input to the annular body20.

The third resistance wire portion W3has a plurality of third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp. In the present example embodiment, the third resistance wire portion W3has eight of the third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp. The plurality of third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp are arranged at intervals in the circumferential direction. In the present example embodiment, the eight third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp are arranged at equal intervals in the circumferential direction. The plurality of third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp are each formed of one conductive wire. Each of the third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp expands in an arc shape along the circumferential direction.

Each of the third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp includes a third site r3. The third site r3extends in the circumferential direction. However, the third site r3extending in the circumferential direction may be repeatedly arranged in the radial direction. The third site r3may extend in the radial direction. The third site r3extending in the radial direction may be repeatedly arranged in the circumferential direction.

Among the eight third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp, four of the third regions Ri, Rk, Rm, and Ro that are not adjacent to one another are connected to one another to form a third bridge circuit C3.FIG.9is a circuit diagram of the third bridge circuit C3. As shown inFIG.9, the third region Ri and the third region Rk are connected in series in this order. The third region Ro and the third region Rm are connected in series in this order. Then, the row of the two third regions Ri and Rk and the row of the two third regions Ro and Rm are connected in parallel between the + pole and the − pole of the power source voltage. A middle point M31between the two third regions Ri and Rk and a middle point M32between the two third regions Ro and Rm are connected to a third voltmeter V3.

Among the eight third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp, the remaining four of the third regions Rj, Rl, Rn, and Rp are connected to one another to form a fourth bridge circuit C4.FIG.10is a circuit diagram of the fourth bridge circuit C4. As shown inFIG.10, the third region Rp and the third region Rn are connected in series in this order. The third region Rj and the third region Rl are connected in series in this order. Then, the row of the two third regions Rp and Rn and the row of the two third regions Rj and Rl are connected in parallel between the + pole and the − pole of the power source voltage. A middle point M41between the two third regions Rp and Rn and a middle point M42between the two third regions Rj and Rl are connected to a fourth voltmeter V4.

When the wave reducer1is driven, the base23of the annular body20has generation of a circumferentially elongating part (hereinafter referred to as “elongation part”) and a circumferentially contracting part (hereinafter referred to as “contraction part”). Specifically, two elongation parts and two contraction parts are alternately generated in the circumferential direction. That is, the elongation part and the contraction part are alternately generated at intervals of 90° in the circumferential direction about the central axis9. Then, a location where the elongation part and the contraction part are generated rotates at the first rotational speed.

The resistance value of each of the eight third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp changes in accordance with the circumferential elongation and contraction of the base23. For example, when the above-described elongation part overlaps a certain third region, the resistance value of the third region increases. When the above-described contraction part overlaps a certain third region, the resistance value of the third region decreases.

In the example ofFIG.5, when the contraction part overlaps the third regions Ri and Rm, the elongation part overlaps the third regions Rk and Ro. When the elongation part overlaps the third regions Ri and Rm, the contraction part overlaps the third regions Rk and Ro. Therefore, in the third bridge circuit C3, the third regions Ri and Rm and the third regions Rk and Ro show resistance value changes reversely to each other.

In the example ofFIG.5, when the contraction part overlaps the third regions Rp and Rl, the elongation part overlaps the third regions Rn and Rj. When the elongation part overlaps the third regions Rp and Rl, the contraction part overlaps the third regions Rn and Rj. Therefore, in the fourth bridge circuit C4, the third regions Rp and Rl and the third regions Rn and Rj show resistance value changes reversely to each other.

FIG.11is a graph showing time change of the measurement value v3of the third voltmeter V3of the third bridge circuit C3and the measurement value v4of the fourth voltmeter V4of the fourth bridge circuit C4. The horizontal axis of the graph ofFIG.11indicates time. The vertical axis of the graph ofFIG.11represents a voltage value. When the wave reducer1is driven, sinusoidal measurement values v3and v4that cyclically change are output from the third voltmeter V3and the fourth voltmeter V4, respectively, as shown inFIG.11. A cycle T of the measurement values v3and v4corresponds to ½ times a cycle of the first rotational speed. An orientation of the rotational motion to be input can be determined based on whether a phase of the measurement value v4of the fourth voltmeter V4is advanced by ⅛ cycle (by ¼ cycle of the measurement values v3and v4) of the first rotational speed with respect to the phase of the measurement value v3of the third voltmeter V3, or is delayed by ⅛ cycle (by ¼ cycle of the measurement values v3and v4) of the first rotational speed with respect to the phase of the measurement value v3of the third voltmeter V3.

The signal processing circuit described below can detect the rotation angle of the rotational motion input to the annular body20based on the measurement value v3of the third voltmeter V3and the measurement value v4of the fourth voltmeter V4. Specifically, for example, the signal processing circuit includes a storage unit that stores a function table in which a combination of the measurement value v3of the third voltmeter V3and the measurement value v4of the fourth voltmeter V4is associated with the rotation angle. The signal processing circuit outputs the rotation angle by inputting the measurement values v3and v4to the function table.

The ripple error changes sinusoidally with respect to a rotation angle of the annular body20. The signal processing circuit calculates the above-described ripple error in accordance with the rotation angle having been output. Thereafter, the output signal of the first resistance wire portion W1and the output signal of the second resistance wire portion W2are corrected using the calculated ripple error. As a result, the signal processing circuit can output, with higher accuracy, the torque applied to the annular body20.

As described above, the resistance wire412of the present example embodiment includes the third resistance wire portion W3. For this reason, it is possible to detect the rotation angle of rotational motion input to the annular body20. Therefore, he output signal of the first resistance wire portion W1and the output signal of the second resistance wire portion W2can be corrected in accordance with the rotation angle.

Without calculating the rotation angle described above, the signal processing circuit may multiply the measurement values v3and v4of the third voltmeter V3and the fourth voltmeter V4by a predetermined coefficient, and synthesize them with the output signal of the first resistance wire portion W1and the output signal of the second resistance wire portion W2. This reduces processing load on calculation of the rotation angle. Therefore, it is possible to improve the calculation speed of the signal processing circuit.

In the present example embodiment, the third resistance wire portion W3is arranged radially outside relative to the first resistance wire portion W1and the second resistance wire portion W2. However, the third resistance wire portion W3may be arranged radially inside relative to the first resistance wire portion W1and the second resistance wire portion W2. The third resistance wire portion W3may be arranged radially outside the first resistance wire portion W1and radially inside the second resistance wire portion W2.

The wave reducer1further includes a housing50and a second substrate60. As shown inFIG.2, the housing50is positioned on one axial side of the annular body20. The housing50covers the annular body20from one axial side. The housing50is stationary relative to the annular body20.

The second substrate60is fixed to the housing50. Therefore, the second substrate60rotates at the second rotational speed about the central axis9together with the housing50. Therefore, the second substrate60is stationary relative to the first terminal43and the second terminal44.

The second substrate60includes the signal processing circuit. The first terminal43and the second terminal44are electrically connected to the signal processing circuit. Therefore, the signal processing circuit is electrically connected to the first resistance wire portion W1via the first terminal43, and is electrically connected to the second resistance wire portion W2via the second terminal44. The signal processing circuit is also electrically connected to the third resistance wire portion W3.

The signal processing circuit detects torque applied to the base23based on output signals from the first resistance wire portion W1and the second resistance wire portion W2. More specifically, the signal processing circuit detects the torque applied to the base23based on the output signals of the first voltmeter V1and the second voltmeter V2. The signal processing circuit detects the rotation angle of the rotational motion input to the annular body20based on the output signal from the third resistance wire portion W3. More specifically, the signal processing circuit detects the rotation angle of the rotational motion input to the annular body20based on the output signals of the third voltmeter V3and the fourth voltmeter V4.

As described above, the wave reducer1of the present example embodiment is equipped with the second substrate60having the signal processing circuit. This can unitize the wave reducer1and the second substrate60.

Hereinafter, the first example of the housing50will be described.

FIG.12is a plan view of the housing50according to the first example.FIG.13is a perspective view of the housing50according to the first example. As shown inFIGS.12and13, the housing50has a wall portion51. The housing50of the present example further includes a housing base52. The housing base52expands in a direction intersecting the central axis9. The wall portion51protrudes axially from the edge of the housing base52. The wall portion51extends circumferentially. The second substrate60is arranged on the radially inside the wall portion51. This can suppress interference between the second substrate60and a site outside the wave reducer1. By relatively fixing the second substrate60and the wall portion51, positional displacement of the second substrate60is suppressed. The second substrate60can be easily positioned with respect to the housing50at the time of manufacturing the wave reducer1.

The wall portion51of the present example includes a first wall portion511and a second wall portion512. The first wall portion511has one circumferential end511aand another circumferential end511b. The second wall portion512is circumferentially adjacent to the first wall portion511. The second wall portion512has one circumferential end512aand another circumferential end512b. A first gap513exists between the one circumferential end511aof the first wall portion511and the other circumferential end512bof the second wall portion512. A second gap514exists between the other circumferential end511bof the first wall portion511and the one circumferential end512aof the second wall portion512. The first terminal43is arranged in the first gap513. The second terminal44is arranged in the second gap514. More specifically, the end of the first terminal43is arranged in the first gap513, and the end of the second terminal44is arranged in the second gap514.

Thus, by arranging the first terminal43not in the wall portion51but in the first gap513, it is possible to suppress the first terminal43from axially protruding from the wall portion51. By arranging the second terminal44not in the wall portion51but in the second gap514, it is possible to suppress the second terminal44from axially protruding from the wall portion51.

As shown inFIG.12, the housing50includes a first connector53and a second connector54. The first connector53is arranged radially inward the first gap513. The second connector54is arranged radially inward the second gap514. The first connector53and the second connector54are electrically connected to the signal processing circuit.

The first terminal43is connected to the first connector53. Specifically, the first terminal43is inserted into the first connector53. Due to this, the first terminal43is electrically connected to the signal processing circuit via the first connector53. The second terminal44is connected to the second connector54. Specifically, the second terminal44is inserted into the second connector54. Due to this, the second terminal44is electrically connected to the signal processing circuit via the second connector54.

As described above, in the present example, the first terminal43is inserted into the first connector53, and the second terminal44is inserted into the second connector54. Due to this, the first terminal43and the second terminal44can be easily connected to the signal processing circuit on the second substrate60.

In the present example, the circumferential length of the first wall portion511and the circumferential length of the second wall portion512are the same. The circumferential length of the first gap513and the circumferential length of the second gap514are the same. That is, the circumferential interval between the one circumferential end511aof the first wall portion511and the other circumferential end512bof the second wall portion512and the circumferential interval between the other circumferential end511bof the first wall portion511and the one circumferential end512aof the second wall portion512are the same. Thus, by evenly arranging the first wall portion511and the second wall portion512in the circumferential direction, it is possible to suppress circumferential variations in the weight of the housing50.

As shown inFIG.12, the first wall portion511and the second wall portion512have a plurality of protrusions515protruding radially inward. The plurality of protrusions515each have a recess or a hole516. The housing50is fixed to the thick part24of the annular body20with a bolt. At this time, the bolt is inserted into the recess or the hole516of the protrusion515.

As shown inFIG.12, the plurality of protrusions515are arranged line-symmetrically with respect to a line L connecting the circumferential center of the first gap513and the circumferential center of the second gap514. That is, the plurality of protrusions515are arranged line-symmetrically with respect to the line L connecting the circumferential center between the one circumferential end511aof the first wall portion511and the other circumferential end512bof the second wall portion512and the circumferential center between the other circumferential end511bof the first wall portion511and the one circumferential end512aof the second wall portion512. Thus, by line-symmetrically arranging the plurality of protrusions515, it is possible to further suppress circumferential variations in the weight of the housing50.

As shown inFIG.12, in the present example, the plurality of protrusions515are arranged at equal intervals in the circumferential direction. This can further suppress circumferential variations in the weight of the housing50.

As shown inFIG.12, the plurality of protrusions515include the protrusion515arranged at the one circumferential end511aof the first wall portion511, the protrusion515arranged at the other circumferential end511bof the first wall portion511, the protrusion515arranged at the one circumferential end512aof the second wall portion512, and the protrusion515arranged at the other circumferential end512bof the second wall portion512. As described above, by arranging the protrusions515at the circumferential ends of the first wall portion511and the second wall portion512, it is possible to improve the rigidity of the first wall portion511and the second wall portion512.

Next, the second example of the housing50will be described. Hereinafter, differences from the first example will be mainly described. The equal parts to those of the first example will not be given repeated descriptions.

FIG.14is a perspective view of the housing50according to the second example. As shown inFIG.14, the housing50includes the housing base52. The housing base52expands in a direction intersecting the central axis9. The second substrate60is arranged on the surface of the housing base52. More specifically, the second substrate60is arranged on the surface on one axial side of the housing base52. This stably supports the second substrate60.

As shown inFIG.14, the housing50has a plurality of protrusions517. The plurality of protrusions517protrude axially from the edge of the surface of the housing base52. More specifically, the plurality of protrusions517protrude toward one axial side from the edge of the surface on one axial side of the housing base52. The plurality of protrusions517each have a recess or a hole518. The housing50is fixed to the thick part24of the annular body20with a bolt. At this time, the bolt is inserted into the recess or the hole518of the protrusion517.

A first gap519exists between two protrusions517of the plurality of protrusions517. A second gap520exists between other two protrusions517of the plurality of protrusions517. The first gap519and the second gap520are arranged at circumferentially different positions. The first terminal43is arranged in the first gap519. The second terminal44is arranged in the second gap520. More specifically, the end of the first terminal43is arranged in the first gap519, and the end of the second terminal44is arranged in the second gap520.

Thus, by arranging the first terminal43not in the protrusion517but in the first gap519, it is possible to suppress the first terminal43from axially protruding from the protrusion517. By arranging the second terminal44not in the protrusion517but in the second gap520, it is possible to suppress the second terminal44from axially protruding from the protrusion517.

As shown inFIG.14, in the present example, the plurality of protrusions517are arranged at equal intervals in the circumferential direction. This can suppress circumferential variations in the weight of the housing50.

Although the example embodiment of the present disclosure has been described above, the present disclosure is not limited to the above example embodiment.

In the above example embodiment, both the first resistance wire portion W1and the second resistance wire portion W2are arranged on the surface on one axial side of the first substrate41. However, the first resistance wire portion W1may be arranged on the surface on one axial side of the first substrate41, and the second resistance wire portion W2may be arranged on the surface on the other axial side of the first substrate41. In this case, the first terminal43may be arranged on the surface on one axial side of the first substrate41, and the second terminal44may be arranged on the surface on the other axial side of the first substrate41. In this way, since both surfaces of the first substrate41are used, it is possible to widely ensure a region where the first resistance wire portion W1and the second resistance wire portion W2are arranged. The first terminal43and the second terminal44are arranged at positions further away from each other. Therefore, it is possible to further reduce the probability that a load is simultaneously applied to the first terminal43and the second terminal44.

In the above example embodiment, both the first resistance wire portion W1and the second resistance wire portion W2are arranged on the surface on one axial side of the base23. However, the first resistance wire portion W1may be arranged on the surface on one axial side of the base23, and the second resistance wire portion W2may be arranged on the surface on the other axial side of the base23. In this case, the first terminal43may be arranged on the surface on one axial side of the base23, and the second terminal44may be arranged on the surface on the other axial side of the base23. In this way, since both surfaces of the base23are used, it is possible to widely ensure a region where the first resistance wire portion W1and the second resistance wire portion W2are arranged. The first terminal43and the second terminal44are arranged at positions further away from each other. Therefore, it is possible to further reduce the probability that a load is simultaneously applied to the first terminal43and the second terminal44.

In the above example embodiment, both the first resistance wire portion W1and the second resistance wire portion W2are arranged on the first substrate41. However, any one of the first resistance wire portion W1and the second resistance wire portion W2may be arranged on the first substrate41, and the other of the first resistance wire portion W1and the second resistance wire portion W2may be arranged on the surface of the base23not via the substrate. By arranging at least any one of the first resistance wire portion W1and the second resistance wire portion W2on the first substrate41, it is possible to improve reliability and mass productivity of resistance wires. However, both the first resistance wire portion W1and the second resistance wire portion W2may be arranged on the surface of the base23not via the substrate.

In the above example embodiment, the wave reducer1has one second substrate60. However, the wave reducer1may have two second substrates60. The two second substrates60may be fixed to the housing50. In this case, the two second substrates60each has the signal processing circuit. The first terminal43is connected to the signal processing circuit arranged on one of the two second substrates60. The second terminal44is connected to the signal processing circuit arranged on the other of the two second substrates60. The two second substrates60may be stacked and arranged on the surface of the housing50. This can more widely ensure a region where the signal processing circuit is arranged.

In the above example embodiment, the first terminal43is arranged in the first gap of the housing50, and the second terminal44is arranged in the second gap of the housing50. However, the housing50may have a through hole axially penetrating the housing base52. At least any one of the first terminal43and the second terminal44may be inserted into the through hole. This can shorten the wiring paths of the first terminal43and the second terminal44.

The housing50may have a first terminal insertion part formed of a groove or a hole and a second terminal insertion part formed of a groove or a hole. The first terminal insertion part is, for example, the first gap or the through hole described above. The second terminal insertion part is, for example, the second gap or the through hole described above. The first terminal insertion part and the second terminal insertion part are arranged at circumferentially different positions. The first terminal43is inserted into the first terminal insertion part. The second terminal44is inserted into the second terminal insertion part.

Thus, when the first terminal43and the second terminal44are arranged at circumferentially different positions, it is possible to reduce the probability that a load is simultaneously applied to the first terminal43and the second terminal44, as compared with a case where the first terminal43and the second terminal44are arranged at the same circumferential position. Therefore, for example, even if one of the first terminal43and the second terminal44no longer functions, the probability that the other terminal functions can be increased. Therefore, the torque applied to the base23can be detected by at least any one of the first resistance wire portion W1and the second resistance wire portion W2.

In the above example embodiment, the first terminal43is connected to the first resistance wire portion W1for detecting the torque applied to the base23. However, the first resistance wire portion to which the first terminal43is connected may be a resistance wire portion for detecting another physical quantity. For example, the first resistance wire portion to which the first terminal43is connected may be a resistance wire portion for detecting the rotation angle of the rotational motion input to the annular body20as in the third resistance wire portion W3of the above example embodiment.

In the above example embodiment, the second terminal44is connected to the second resistance wire portion W2for detecting the torque applied to the base23. However, the second resistance wire portion to which the second terminal44is connected may be a resistance wire portion for detecting another physical quantity. For example, the second resistance wire portion to which the second terminal44is connected may be a resistance wire portion for detecting the rotation angle of the rotational motion input to the annular body20as in the third resistance wire portion W3of the above example embodiment.

That is, the first resistance wire portion to which the first terminal43is connected may be a resistance wire portion having a resistance value changing in accordance with the strain of the base23. The second resistance wire portion to which the second terminal44is connected may be a resistance wire portion having a resistance value changing in accordance with the strain of the base23in order to detect the same physical quantity as that of the first resistance wire portion.

In the above example embodiment, the resistance wire412includes the third resistance wire portion W3for detecting the rotation angle of the rotational motion input to the annular body20. In addition to this, the resistance wire412may further include a fourth resistance wire portion W4for detecting the rotation angle of the rotational motion input to the annular body20.FIG.15is a plan view of the first substrate41according to the modification.

Similarly to the third resistance wire portion W3, the fourth resistance wire portion W4includes a plurality of fourth regions Rq, Rr, Rs, Rt, Ru, Rv, Rw, and Rx. The plurality of fourth regions Rq, Rr, Rs, Rt, Ru, Rv, Rw, and Rx are arranged at intervals in the circumferential direction. The fourth regions Rq, Rr, Rs, Rt, Ru, Rv, Rw, and Rx each have a fourth site extending circumferentially or radially. The four fourth regions Rq, Rs, Ru, and Rw are connected to one another to form a bridge circuit. The four fourth regions Rr, Rt, Rv, and Rx are connected to one another to form a bridge circuit.

In this way, the rotation angle of the rotational motion input to the annular body20can be detected not only in the third resistance wire portion W3but also in the fourth resistance wire portion W4. In the example ofFIG.15, the fourth resistance wire portion W4is arranged radially inside relative to the first resistance wire portion W1. In this case, for example, the ripple correction of a detection signal of the second resistance wire portion W2is preferably performed by the detection signal of the third resistance wire portion W3, and the ripple correction of a detection signal of the first resistance wire portion W1is preferably performed by the detection signal of the fourth resistance wire portion W4.

However, the fourth resistance wire portion W4may be arranged radially outside the first resistance wire portion W1and radially inside the second resistance wire portion W2. The fourth resistance wire portion W4may be arranged radially outside relative to the second resistance wire portion W2.

The annular body20of the above example embodiment is what is called a “hat-shaped” flexible externally toothed gear in which the base23expands radially outward from the body21. The hat-shaped flexible externally toothed gear is excellent in that a space on radially inside the body21can be effectively used. However, the annular body20may be what is called a “cup-shaped” flexible externally toothed gear in which the base23expands radially inward from the body21. The internally toothed gear10may be fixed to the base frame101, and the annular body20may be fixed to the arm102. In that case, the housing50may be a part of a robot arm102.

In the example embodiment, the wave reducer1equipped on the robot100has been described. However, the wave reducer1having a similar structure may be equipped on another device such as an assist suit or an automatic guided vehicle.

In addition, detailed configurations of the annular body, the wave reducer, and the robot may be appropriately changed without departing from the gist of the present disclosure. The elements appearing in the above example embodiment and modifications may be appropriately combined as long as no contradiction occurs.

The present disclosure is applicable to, for example, an annular body, a wave reducer, and a robot.

Features of the above-described example embodiments and the modifications thereof may be combined appropriately as long as no conflict arises.

While example embodiments of the present disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims.