JP2011152026A - Rotary drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce size and weight for a rotary drive device using a wave motion gear mechanism. <P>SOLUTION: A piezo-rotor 14 is provided in a rotatable manner inward in the radial direction of a flex spline 12. The flex spline 12 is depressed outward in the radial direction by a long depressing part 14b on the piezo-rotor 14 to engage outer teeth 12a of the flex spline 12 with inner teeth 11c of a circular spline 11. A flexible movable part 14c is formed on the piezo-rotor 14, and a voltage is applied to a piezoelectric element 16 attached to the movable part 14c to generate distortion repeatedly. This deforms the movable part 14c with acceleration repeatedly, thereby generating inertia continuously in the piezo-rotor 14 for rotation. Rotation of the piezo-rotor 14 moves a circumferential position where the outer teeth 12a is engaged with the inner teeth 11c, and rotation of the piezo-rotor 14 is decelerated to be output in the flex spline 12. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rotary drive device using a wave gear mechanism.

  There has been a conventional technique related to a rotary drive device that uses a wave gear mechanism to decelerate and output a rotary drive force (see, for example, Patent Document 1 and Patent Document 2). The wave gear mechanism used by these is generally called Harmonic Drive (registered trademark). The flex spline is in contact with the outer peripheral surface of the cam body forming the wave generator via a bearing, and the radius of the flex spline. And a circular spline provided outward in the direction.

  Internal teeth are formed on the inner peripheral surface of the circular spline, and fewer external teeth are formed on the outer peripheral surface of the flexspline than the inner teeth of the circular spline. Only two places on the circumference of the teeth mesh with the inner teeth of the circular spline. In this mechanism, by driving the cam body of the wave generator, the portion where the external teeth and the internal teeth mesh with each other moves on the circumference, and the rotational driving force is decelerated and output at the flexspline.

  Since such a rotational drive device uses a wave gear mechanism, it can take a large reduction ratio, and can cope with various output loads or fluctuations.

JP 2004-346960 A JP 7-332442 A

However, in the rotary drive device disclosed in Patent Document 1 and Patent Document 2 described above, the cam body of the wave generator is driven by the electric motor, and therefore the electric motor is disposed axially outward of the wave generator. The entire apparatus must be lengthened in the axial direction and the weight is increased. Therefore, it is necessary to form a mounting space for the rotary drive device in consideration of the size of the electric motor.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a small and lightweight rotary drive device.

  In order to solve the above-described problem, a structural feature of the invention of the rotary drive device according to claim 1 is a circular spline having a ring-shaped portion and a plurality of internal teeth on the inner peripheral surface of the ring-shaped portion. By forming a flexible annular portion, the outer peripheral surface of the annular portion has fewer external teeth than the inner teeth of the circular spline, and is arranged radially inward of the circular spline. By pressing the flexspline where the outer teeth face the inner teeth and several locations on the inner peripheral surface of the flexspline radially outward toward the circular spline, only a part of the outer teeth are pressed against the inner teeth. And a wave generator that rotates and moves the pressing part with respect to the flexspline, and the flexing line is rotated and moved by the wave generator. While the line is deflected, the position on the circumference where the external teeth and the internal teeth mesh is moved, and by fixing one of the circular spline and the flexspline, the wave is generated on the other of the circular spline and the flexspline. In a rotary drive device in which rotation by the generator is decelerated and output, the wave generator is provided so as to be rotatable with respect to the flexspline inwardly in the radial direction of the flexspline. A rotary pressing member that abuts at the abutting portion and presses the flex spline against the circular spline is formed. The rotary pressing member is formed with a deformable shape variable portion, and the shape variable portion is distorted according to an electric signal. The strain variable element is attached, the strain element repeatedly generates strain, and the shape variable part is repeatedly applied. By deformed with a degree to generate a continuously inertial force to the rotation pressing member, it is that the rotary pressure member is rotated by an inertia force.

  The structural feature of the invention according to claim 2 is that, in the rotary drive device according to claim 1, the strain element is formed of any one of a piezoelectric element, a magnetostrictive element, an electrostrictive element, and a shape memory element. It is.

  According to a third aspect of the present invention, in the rotary drive device according to the first or second aspect, the rotary pressing member has a pressing portion formed in an elongated shape, and a central portion in the longitudinal direction of the pressing portion is provided. Inner teeth that are rotatably provided around the center and are formed at two locations facing each other across the center of the circular spline by contacting the inner surface of the flexspline at the abutting portions at both ends of the pressing portion. And a movable portion that protrudes in a direction different from the longitudinal direction from a midway portion of the pressing portion in the longitudinal direction is provided as the shape variable portion, and a strain element is attached to the movable portion, and the strain element is generated. That is, the movable portion is bent in the rotation direction due to the distortion, and an inertial force is generated in the rotation pressing member.

  The structural feature of the invention according to claim 4 is the rotary drive device according to claim 1 or 2, wherein the rotary pressing member is formed in a long shape, and is provided to be rotatable around a central portion in the longitudinal direction. By abutting the inner peripheral surface of the flexspline at the abutting portions at both ends, the outer teeth are engaged with the inner teeth formed at two locations facing each other across the center of the circular spline, and at least one side of the rotation center. A movable portion that can be bent in the rotation direction is formed as the shape variable portion between the end portion, and a strain element is attached to the movable portion, and the movable portion is bent and rotated by strain generated in the strain element. Inertial force is generated in the member.

  According to a fifth aspect of the present invention, in the rotary drive device according to the first or second aspect, the rotary pressing member is arranged so that the three or more pressing portions form a uniform angle with each other from the rotation center. The outer teeth are engaged with a plurality of locations on the circumference of the inner teeth by extending the contact portions of the end portions of the pressing portions to the inner peripheral surface of the flexspline, and at least one pressing portion has the shape described above. The variable portion is formed so as to be able to bend in the rotation direction and has a strain element attached thereto, and the pressing portion is bent due to the strain generated in the strain element, and inertia force is generated in the rotary pressing member.

  A structural feature of the invention according to claim 6 is that the rotary drive device according to any one of claims 1 to 5 is attached to the rotary pressing member and is elastically deformable in a rotation direction of the rotary pressing member. A vibration system including a member and a vibration weight; and a control device that causes the strain element to generate a strain near a resonance frequency of the vibration system.

  According to a seventh aspect of the present invention, in the rotary drive device according to the sixth aspect, the vibration system protrudes radially outward in the same phase in the circumferential direction as the abutting portion of the pressing member and rotates. It is fixed to the pressing member.

  The structural feature of the invention according to claim 8 is the rotary drive device according to any one of claims 1 to 7, wherein the circular spline or the flexspline has a shaft that rotatably supports the rotary pressing member at the center of rotation. That is, the holding part is formed.

  The structural feature of the invention according to claim 9 is that in the rotational drive device according to any one of claims 1 to 8, the rotational speed detecting means for detecting the output rotational speed of the circular spline or flexspline, and the strain element A rotation control unit that controls an electric signal to be supplied, and the rotation control unit reduces unevenness of the output rotation speed due to the rotation position of the circular spline or the flexspline based on the output rotation speed detected by the rotation speed detection unit. Thus, the electric signal supplied to the strain element is controlled.

  According to a tenth aspect of the present invention, there is provided a structural feature of the rotary drive device according to any one of the first to eighth aspects, further comprising reference speed setting means for forming a reference rotation speed of the circular spline or flexspline, and rotation control. The means is to control an electric signal supplied to the strain element in accordance with a deviation between the output rotation speed detected by the rotation speed detection means and the reference rotation speed set by the reference speed setting means.

  According to the rotary drive device of the first aspect, the wave generator includes a rotary pressing member that is in contact with several locations on the inner peripheral surface of the flexspline at the abutting portion and presses the flexspline against the circular spline. A strain element is attached to the variable shape portion formed on the rotary pressing member, and the strain pressing element repeatedly generates strain to deform the variable shape portion with repeated acceleration, and the inertia force generated thereby causes the rotary pressure member to rotate. Therefore, the mechanism for driving the wave generator can be arranged radially inward of the flexspline, and there is no need to provide an electric motor or the like outside the wave generator in the axial direction. It can be reduced in size and weight in the axial direction.

  In addition, since the rotary pressing member is driven using inertial force, the rotational speed of the rotary pressing member is changed by changing the weight of the shape variable portion or the acceleration of deformation thereof, and eventually the circular spline or flexure is changed. The rotational speed of the spline can be changed. Further, by changing the weight of the shape variable portion or the acceleration of its deformation, it is possible to cope with the load received by the circular spline or flexspline.

  In addition, since the distortion element can be operated by an electric signal in a high audible outside region, it is possible to provide a rotary drive device with a low operating sound.

  According to the rotary drive device according to claim 2, since the strain element is formed of any one of a piezoelectric element, a magnetostrictive element, an electrostrictive element, and a shape memory element, a strain amount according to an electric signal to be supplied. The rotation of the rotary pressing member can be easily controlled.

  According to the rotary drive device of the third aspect, the flex spline is pressed at the abutting portions at both ends of the pressing portion to mesh the outer teeth with the inner teeth, and the strain element is attached to the movable portion protruding from the pressing portion. By bending in the rotational direction and generating an inertial force in the rotary pressing member, the pressing portion that presses the flexspline and the movable portion that is deformed by the strain element can be formed in different parts in the rotating pressing member. For this reason, each rigidity is set freely, the movable part is easily bent while maintaining the rigidity of the pressing part, the flex spline can be surely pressed by the pressing part, and the inertial force generated in the rotary pressing member is increased. Can be made.

  According to the rotary drive device of the fourth aspect, the flexspline is pressed at the contact portions at both ends of the rotary pressing member to engage the outer teeth with the inner teeth, and between the rotation center and at least one end portion. By forming a movable part and attaching a strain element and bending the movable part to generate an inertial force on the rotary pressing member, the pressing part that presses the flexspline and the movable part are integrally formed. For this reason, it is not necessary to provide a shape variable part specially, a rotation pressing member can be reduced in size and weight, and the inertia force required in order to rotate a rotation pressing member can be reduced.

  According to the rotary drive device of the fifth aspect, the three or more pressing portions extend radially from the rotation center of the rotary pressing member so as to form an equal angle with each other, and the flex spline is formed at the contact portion of each end portion. Since the rotary pressing member can evenly contact the inner peripheral surface of the flexspline at three or more locations on the circumference by providing the pressure, a portion that supports the rotary pressing member is provided on the circular spline or flexspline. Even if it does not exist, a rotation press member can rotate stably.

  According to the rotation drive device of the sixth aspect, the vibration system including the elastic member that can be elastically deformed in the rotation direction of the rotation pressing member and the vibration weight is attached to the rotation pressing member, and the strain element is near the resonance frequency of the vibration system. The vibration weight is greatly vibrated by generating distortion in the rotary pressing member, thereby applying a larger rotational torque to the rotary pressing member, and increasing and stabilizing the output torque from the circular spline or flex spline. Can do.

  According to the rotary drive device of the seventh aspect, the vibration system protrudes radially outward at the same phase in the circumferential direction as the abutting portion of the pressing member and is fixed to the rotating pressing member. However, a large rotational torque can be reliably applied to the rotary pressing member at the abutting portion that abuts against the inner peripheral surface of the flexspline, and the output torque from the circular spline or flexspline can be increased and stabilized.

  According to the rotary drive device according to the eighth aspect, the circular spline or the flexspline is formed with the shaft holding portion that rotatably supports the rotary press member at the center of rotation. It can rotate stably inward in the radial direction.

  In addition, when a plurality of strain elements are attached to the rotation pressing member, the rotation pressing member can be stably rotated without losing the balance even if only some of the strain elements are distorted. Can do.

  According to the rotational drive device of the ninth aspect, the electric signal supplied to the strain element is controlled based on the detected output rotational speed so as to reduce the unevenness of the output rotational speed due to the rotational position of the circular spline or flexspline. By doing so, the rotational speed of the circular spline or flex spline can be kept constant and smoothly rotated. Therefore, abnormal noise due to uneven output rotation speed can also be reduced.

  According to the rotational drive device of the tenth aspect, the reference rotational speed of the circular spline or the flexspline is formed, and is supplied to the strain element according to the deviation between the detected output rotational speed and the set reference rotational speed. By controlling the electrical signal, the circular spline or flexspline can be easily controlled to reach the target rotational speed.

2 is a cross-sectional view taken along line AA in FIG. 2 when the harmonic gear device according to the first embodiment of the present invention is cut by a cross section perpendicular to the output rotation axis. BB sectional view of the harmonic gear device shown in FIG. C part enlarged view (a) of the harmonic gear device shown in FIG. 1 and an enlarged view when the movable part is bent (b) Simplified plan view for explaining the operating principle of the harmonic gear device Overall block diagram showing a rotary drive system including a harmonic gear device The figure which showed the electric signal waveform supplied to a piezoelectric element Diagram showing output voltage waveform of rotation speed sensor before and after execution of rotation unevenness control The figure which showed the electric signal waveform supplied to a piezoelectric element at the time of execution of rotation nonuniformity control The figure which showed the electric signal waveform by another form supplied to a piezoelectric element at the time of execution of rotation nonuniformity control Simplified plan view of a harmonic gear device according to a modified embodiment of the first embodiment Simplified plan view of the harmonic gear device according to the second embodiment Simplified plan view of a harmonic gear device according to a modified embodiment of the second embodiment Simplified plan view of a harmonic gear device according to Embodiment 3 Partial enlarged view of the piezo rotor according to the fourth embodiment. Sectional drawing of the harmonic gear apparatus by Embodiment 5 The figure which shows operation | movement of the harmonic gear apparatus by Embodiment 5. First Modification of Harmonic Gear Device According to Embodiment 5 Second Modification of Harmonic Gear Device According to Embodiment 5

<Embodiment 1>
Based on FIG. 1 thru | or FIG. 9, the harmonic gear apparatus 1 by Embodiment 1 of this invention is demonstrated. In the description, the direction of the rotation axis means the direction along the output rotation axis of the harmonic gear device 1, that is, the vertical direction in FIG. Further, the vertical direction in the description means the vertical direction in FIG.

  FIG. 1 is a cross-sectional view of the harmonic gear device 1 according to the present embodiment taken along line AA in FIG. The harmonic gear device 1 is formed by a circular spline 11, a flex spline 12, a gear cover 13, and a piezo rotor 14 (corresponding to a wave generator and a rotary pressing member of the present invention).

  The circular spline 11 is formed in a substantially dish shape from a metal material or a hard synthetic resin material. A circular ring-shaped part 11b is formed on the outer peripheral edge of the bottom part 11a of the circular spline 11 so as to extend in the direction of the rotation axis. A plurality of inner teeth 11c (in this case) are formed on the inner peripheral surface of the ring-shaped part 11b. Corresponding to the internal teeth of the invention). Further, a through hole 11d (corresponding to the shaft holding portion of the present invention) is formed at the center of the bottom portion 11a. The circular spline 11 is fixed so as not to rotate by a fixing member (not shown).

The flex spline 12 is formed in an annular shape from a metal material or a synthetic resin material, and is provided so as to be rotatable with respect to the circular spline 11. Outer teeth 12 a (corresponding to the outer teeth of the present invention) are formed on the outer peripheral surface of the flexspline 12, which is fewer than the inner teeth 11 c of the circular spline 11.
The valley portion of the outer teeth 12a is formed to be thin, whereby the flex spline 12 has flexibility. The flex spline 12 is disposed radially inward of the circular spline 11, so that the outer teeth 12a faces the inner teeth 11c.

  The gear cover 13 is integrally formed of a synthetic resin material or a metal material, and has a substantially lid shape. The gear cover 13 includes a flat upper surface portion 13a and a side surface portion 13b extending downward from the upper surface portion 13a in FIG. The lower end of the side surface portion 13 b is in contact with the ring-shaped portion 11 b of the circular spline 11, and the gear cover 13 is formed to be rotatable with respect to the circular spline 11.

  On the inner peripheral surface of the side surface portion 13 b of the gear cover 13, the same number of internal teeth 13 c as the outer teeth 12 a of the flexspline 12 are formed. For this reason, the gear cover 13 can rotate at the same speed as the flex spline 12 by the inner teeth 13c meshing with the outer teeth 12a. Further, an output shaft portion 13 d protrudes upward from the upper surface portion 13 a of the gear cover 13.

  The piezo rotor 14 is integrally formed of a synthetic resin material, and has a cylindrical support shaft portion 14a fitted in the through hole 11d of the circular spline 11 via a bearing member 15, and a length formed above the support shaft portion 14a. A scale-like pressing portion 14b is provided, and a movable portion 14c (corresponding to the shape variable portion of the present invention) protrudes from the pressing portion 14b.

  The pressing portion 14b is formed in a substantially plate shape extending in the vertical direction in FIG. 1, and the above-described support shaft portion 14a is connected to the center portion in the longitudinal direction. The support shaft portion 14a is rotatably inserted into the through hole 11d, and the piezo rotor 14 is rotatably supported by the circular spline 11 around the central portion of the pressing portion 14b.

  The piezo rotor 14 is disposed radially inward of the flex spline 12, and contact portions 14 b 1 for pressing the inner peripheral surface of the flex spline 12 are formed at both ends of the press portion 14 b. The pair of contact portions 14b1 presses the inner peripheral surface of the flexspline 12 outward in the radial direction toward the circular spline 11, thereby the outer teeth 12a formed at the pressed portion of the flexspline 12. Only meshes with the inner teeth 11 c formed at two positions facing each other across the center of the circular spline 11 and the inner teeth 13 c of the gear cover 13.

  Moreover, the movable part 14c protrudes from the center part of the longitudinal direction of the press part 14b in the substantially right angle direction with respect to the direction where the press part 14b is extended. As shown in FIG. 3A, the movable portion 14c is formed in a thin plate shape so that it can be bent, and a weight portion 14c1 having a predetermined weight is formed at the tip thereof.

  A piezoelectric element 16 (corresponding to a strain element of the present invention) sandwiched between a pair of electrodes 17a and 17b is attached to one side surface of the movable portion 14c. The piezoelectric element 16 is formed of piezoelectric ceramic, Rochelle salt, crystal, or the like, and is a known piezo element that generates a strain amount corresponding to a voltage applied between the electrodes 17a and 17b.

  As shown in FIG. 2, terminals 18a and 18b (positive terminal 18a and negative terminal 18b) for supplying electric power to the piezoelectric element 16 from the outside are attached to the support shaft portion 14a. The positive terminal 18a is connected to one of the electrodes 17a and 17b of the piezoelectric element 16 described above, and the negative terminal 18b is connected to the remaining electrodes 17a and 17b (details are not shown).

  As shown in FIG. 2, when a positive side of the DC power source is connected to the positive terminal 18a and a negative side is connected to the negative terminal 18b and a voltage is applied to the piezoelectric element 16, distortion occurs in the piezoelectric element 16. When the piezoelectric element 16 is distorted, the movable portion 14c is formed so as to bend in the clockwise direction in FIG. 1 over the entire portion between the connection portion with the pressing portion 14b and the tip (see FIG. 1). 3 (b) shown).

  As shown in FIG. 4, when the movable portion 14c starts to bend clockwise with a predetermined acceleration due to the strain generated in the piezoelectric element 16, the rotational torque is applied to the piezo rotor 14 by the movement of the weight portion 14c1 at the tip of the movable portion 14c. appear. That is, the weight of the weight portion 14c1 is m, the acceleration generated in the weight portion 14c1 due to the bending of the movable portion 14c is a, and the weight from the rotation center P of the piezo rotor 14 (the center position of the support shaft portion 14a supported by the through hole 11d). When the distance to the part 14c1 is L, a rotational torque of T = ma · L acts. When this rotational torque is set to be larger than the resistance force in the piezo rotor 14, the piezo rotor 14 starts to rotate clockwise around the flex spline 12 around P.

  At this time, the counterclockwise reaction force acts on the piezo rotor 14 due to the bending of the movable portion 14c. However, since the reaction force acts near the rotation center of the piezo rotor 14, the force prevents the piezo rotor 14 from rotating clockwise. Must not.

  By applying a voltage to the piezoelectric element 16 once, the rotational torque acting on the piezo rotor 14 acts on the piezo rotor 14 as an inertial force. Therefore, even if the voltage applied to the piezoelectric element 16 is released, the piezo rotor 14 rotates. Keep doing. There is a sliding resistance between the inner peripheral surface of the flexspline 12 and the abutting portion 14b1 of the piezo rotor 14, and in the vicinity where the amount of bending of the movable portion 14c is maximized, the weight portion 14c1 has a reverse direction. Thus, the piezo rotor 14 continues to rotate until the above-described inertial force disappears due to the resistance force.

  Further, by repeatedly turning on and off the voltage applied to the piezoelectric element 16, distortion is repeatedly generated in the piezoelectric element 16. As a result, the movable portion 14 c is repeatedly deformed with acceleration, and an inertial force is continuously generated in the piezo rotor 14, so that the piezo rotor 14 continuously rotates clockwise in the flexspline 12.

  The rotation of the piezo rotor 14 causes the contact portion 14b1 to move on the circumference while sliding with respect to the inner peripheral surface of the flex spline 12, thereby rotating the pressing portion of the flex spline 12. As a result, the position on the circumference where the outer teeth 12a and the inner teeth 11c mesh is moved clockwise while the flexspline 12 is bent.

  Therefore, when the circular spline 11 is fixed, the flexspline 12 rotates in the opposite direction (counterclockwise) to the piezo rotor 14, and at the output shaft portion 13 d of the gear cover 13 that can rotate at the same speed as the flexspline 12. The rotation by the piezo rotor 14 is decelerated and output. When the output shaft portion 13d is rotated in the opposite direction (clockwise) to that described above, the connection of the power source to the electrodes 17a and 17b of the piezoelectric element 16 may be reversed.

  As shown in FIG. 5, the rotational drive system according to the present embodiment (corresponding to the rotational drive device of the present invention) includes the above-described harmonic gear device 1, controller 2 (corresponding to the rotational control means of the present invention), rotational speed. A sensor 3 (corresponding to the rotation speed detecting means of the present invention), an operational amplifier 4 and a reference voltage setting unit 5 (corresponding to the reference speed setting means of the present invention) are provided.

  The rotational speed sensor 3 is disposed in the vicinity of the output shaft portion 13d of the gear cover 13, and generates a voltage signal corresponding to the detected rotational speed of the output shaft portion 13d (equal to the rotational speed of the flex spline 12). The voltage signal from the rotation speed sensor 3 is input to the non-inverting input terminal of the operational amplifier 4. A reference voltage setting unit 5 is connected to the inverting input terminal of the operational amplifier 4, and a voltage signal corresponding to the target rotational speed of the harmonic gear device 1 set by the reference voltage setting unit 5 is input.

  The controller 2 is connected to the output terminal of the operational amplifier 4 and the reference voltage setting unit 5, and the terminals 18 a and 18 b formed on the support shaft portion 14 a are connected to the controller 2. The controller 2 is connected to a power source (not shown) and controls the supply voltage to the terminals 18a and 18b.

  As shown in FIG. 6, the controller 2 repeatedly supplies an electric signal with the maximum voltage Vs between the terminals 18a and 18b with a period Ts. The voltage Vs and the period Ts of the electric signal are set to values necessary for continuously rotating the piezo rotor 14.

  Further, as shown in FIG. 6, the electric signal generated by the controller 2 has a gradual decrease gradient with respect to the voltage increase gradient. Therefore, the bending acceleration at the time of return is smaller than the bending acceleration at the time of deformation of the movable portion 14c, so that rotational torque in the opposite direction is not generated in the piezo rotor 14.

  Based on the rotational speed of the output shaft portion 13 d detected by the rotational speed sensor 3, the controller 2 reduces unevenness in the rotational speed due to the rotational position of the flexspline 12 (which agrees with the rotational position of the output shaft portion 13 d of the gear cover 13). As described above, the electric signal supplied to the piezoelectric element 16 is controlled.

  The controller 2 detects the voltage value detected by the rotation speed sensor 3 (a value corresponding to the rotation speed of the output shaft portion 13d is detected) and the reference voltage set by the reference voltage setting unit 5 (of the flex spline 12). The electrical signal supplied to the piezoelectric element 16 is controlled (rotational unevenness control) according to the deviation from the target rotational speed (which is set to a value corresponding to the reference rotational speed that is the target rotational speed).

  For example, as shown by a solid line in FIG. 7, when the rotational position of the output shaft 13d (the rotational position of the flex spline 12) is around 90 degrees, the detection voltage of the rotational speed sensor 3 is lower than the reference voltage by a predetermined amount. As shown in FIG. 8, at the rotational position, an electric signal of voltage Vs is supplied to the piezoelectric element 16 at a period Th (<Ts). Thereby, the frequency of occurrence of bending in the movable portion 14c increases, and the rotational speed of the piezo rotor 14 can be increased (indicated by a broken line in FIG. 7).

  At this time, the greater the deviation between the detected voltage of the rotation speed sensor 3 and the reference voltage, the closer the rotation speed of the piezo rotor 14 can be to the reference rotation speed by shortening the cycle of the electrical signal.

  Unlike the case described above, when the detection voltage of the rotation speed sensor 3 is higher than the reference voltage by a predetermined amount such that the rotation position of the output shaft portion 13d is near 180 degrees, the cycle of the electric signal supplied to the piezoelectric element 16 is set. It goes without saying that the rotation speed of the piezo rotor 14 may be reduced by increasing the length.

  In addition, when the detected voltage of the rotation speed sensor 3 is lower than the reference voltage by a predetermined amount, instead of shortening the cycle of the electric signal supplied to the piezoelectric element 16, as shown in FIG. An electric signal having a voltage Vh (> Vs) may be supplied. Thereby, the acceleration which generate | occur | produces in the weight part 14c1 increases, and the rotational speed of the piezo rotor 14 can be increased. In this case, it is desirable to suppress the increase in the period of the electric signal by making the voltage decrease gradient slightly steep.

  When changing the voltage of the electrical signal, the greater the deviation between the detected voltage of the rotational speed sensor 3 and the reference voltage, the greater the maximum voltage of the electrical signal, thereby bringing the rotational speed of the piezo rotor 14 closer to the reference rotational speed. be able to.

  Further, in order to reduce unevenness in the rotational speed due to the rotational position of the flexspline 12, both the period and voltage of the electrical signal supplied to the piezoelectric element 16 may be changed in a superimposed manner.

  According to this embodiment, the wave generator is provided with the piezo rotor 14 that contacts the two inner peripheral surfaces of the flex spline 12 and presses the flex spline 12 against the circular spline 11. The piezoelectric element 16 is attached to the movable portion 14c, and distortion is repeatedly generated in the piezoelectric element 16 to deform the movable portion 14c with repeated acceleration. The piezoelectric rotor 14 is rotated by the inertial force generated thereby. Can be arranged radially inward of the flexspline 12, and there is no need to provide an electric motor or the like outside the flexspline 12 in the axial direction, and the entire harmonic gear device 1 is reduced in size and weight in the axial direction. Can do.

  Further, since the piezo rotor 14 is driven using inertial force, the rotation speed of the piezo rotor 14 is changed by changing the weight of the movable portion 14c or the acceleration of the deformation thereof, and thus the flex spline 12 is rotated. The speed can be changed. Further, by changing the weight of the movable portion 14c or the acceleration of its deformation, it is possible to cope with the load received by the output shaft portion 13d.

  Moreover, since the piezoelectric element 16 can be operated by an electric signal in a high audible outside region, the harmonic gear device 1 with a low operating sound can be obtained.

  Further, since the piezoelectric element 16 is attached to the movable portion 14c, the amount of strain can be changed according to the supplied voltage, and the rotation control of the piezo rotor 14 can be easily performed.

  Further, based on the detected rotational speed of the output shaft portion 13d, the electrical signal supplied to the piezoelectric element 16 is controlled so as to reduce the unevenness of the rotational speed due to the rotational position of the flex spline 12, thereby The rotation speed can be kept constant and can be rotated smoothly. Therefore, abnormal noise due to uneven output rotation speed can also be reduced.

  Further, a reference voltage corresponding to the target rotational speed of the flexspline 12 is set, and an electric signal to be supplied to the piezoelectric element 16 according to a deviation between the detected detection voltage of the rotational speed sensor 3 and the set reference voltage. By controlling, it is possible to easily control the flexspline 12 so as to reach the target rotational speed.

  Further, the flex spline 12 is pressed at both ends of the pressing portion 14b to engage the outer teeth 12a with the inner teeth 11c, and the piezoelectric element 16 is attached to the movable portion 14c protruding from the pressing portion 14b to bend in the rotational direction. By generating an inertial force in the piezo rotor 14, in the piezo rotor 14, a pressing portion 14 b that presses the flexspline 12 and a movable portion 14 c that is bent by the piezoelectric element 16 can be formed in different parts. Therefore, each of the rigidity is set freely, the movable part 14c is easily bent while maintaining the rigidity of the pressing part 14b, the flex spline 12 can be reliably pressed by the pressing part 14b, and inertia generated in the piezo rotor 14 The power can be increased.

  The circular spline 11 is formed with a through hole 11 d that rotatably supports the piezo rotor 14 via the bearing member 15, so that the piezo rotor 14 can stably rotate inward in the radial direction of the flexspline 12. it can.

<Modification of Embodiment 1>
As shown in FIG. 10, as a modification of the first embodiment, the harmonic gear device 1 according to the first embodiment may not include a support structure (through hole 11 d) for the piezo rotor 14 </ b> D by the circular spline 11. According to this modification, since the piezo rotor 14D is not restrained by the circular spline 11 at the rotation center (indicated by P in FIG. 10), the piezo rotor 14D can rotate following the inner peripheral surface of the flexspline 12. The two opposing locations of the flexspline 12 can be pressed with good balance.
Since other configurations in the present modification are the same as those of the harmonic gear device 1 according to the first embodiment, detailed description thereof is omitted.

<Embodiment 2>
FIG. 11 is a simplified diagram of the harmonic gear device according to the second embodiment. In the present embodiment, the piezo rotor 14E is formed in a long shape, and a support shaft portion 14E1 projects in a direction perpendicular to the paper surface in FIG. Since the support shaft portion 14E1 is fitted to the through hole 11d of the circular spline 11 via the bearing member 15, the piezo rotor 14E is supported by the circular spline 11 so as to be rotatable around the central portion in the longitudinal direction. ing.

  Further, the piezo rotor 14E includes a long pressing portion formed radially outward from the support shaft portion 14E1, and abuts the inner peripheral surface of the flex spline 12 at the abutting portion at the tip thereof. The outer teeth 12a of the circular spline 11 are meshed with each other at two locations facing each other across the center.

Further, the pressing portion includes a movable portion 14E2 (corresponding to the shape variable portion of the present invention) that can bend in the rotational direction between the rotation center (indicated by P in FIG. 11) of the piezo rotor 14E and the contact portion at the tip. And the piezoelectric element 16 is attached to each movable portion 14E2. Further, a weight portion 14E3 having a predetermined weight is formed at the tip of each pressing portion so as to also serve as a contact portion. Thereby, due to the distortion generated in the piezoelectric element 16, each movable portion 14E2 is bent and an inertial force is generated, and the piezo rotor 14E rotates clockwise.
In the present embodiment, the bendable movable portion 14E2 including the piezoelectric element 16 may be formed only in the pressing portion protruding in one direction from the rotation center of the piezo rotor 14E.

  According to this embodiment, the flex spline 12 is pressed at the abutting portion at the tip of the pressing portion of the piezo rotor 14E to engage the outer teeth 12a with the inner teeth 11c, and the movable portion is at least one side of the rotation center and the pressing portion. 14E2 is formed, the piezoelectric element 16 is attached, the movable portion 14E2 is bent, and an inertial force is generated in the piezo rotor 14E, so that the movable portion 14E2 that can be bent is integrally formed with the pressing portion that presses the flexspline 12. ing. For this reason, it is not necessary to provide a shape variable part specially, the piezo rotor 14E can be reduced in size and weight, and the inertia force required in order to rotate the piezo rotor 14E can be reduced.

  Further, since the circular spline 11 supports the piezo rotor 14E at the center of rotation, even if only one of the pair of piezoelectric elements 16 is applied with a voltage to bend only the one movable portion 14E2, the piezo rotor 14E is It can rotate stably without breaking the balance.

<Modification of Embodiment 2>
As shown in FIG. 12, as a modification of the second embodiment, the harmonic gear device according to the second embodiment may be configured not to include a support structure (through hole 11d) for the piezoelectric rotor 14F by the circular spline 11.

  Since other configurations in the present modification are the same as those of the harmonic gear device according to the second embodiment, detailed description thereof is omitted.

<Embodiment 3>
FIG. 13 is a simplified diagram of the harmonic gear device according to the third embodiment. In the present embodiment, the three pressing portions 14G1 extend radially from the rotation center (indicated by P in FIG. 13) of the piezo rotor 14G so as to form an equal angle with each other. The contact portion is in contact with the inner peripheral surface of the flexspline 12.
Thereby, the outer teeth 12a of the flexspline 12 are meshed with three locations on the circumference of the inner teeth 11c of the circular spline 11. Further, a weight portion 14G2 is also provided at the tip of each pressing portion 14G1 as a contact portion. Further, one of the pressing portions 14G1 is formed so as to be able to bend in the rotation direction, and has a piezoelectric element 16 attached thereto. One of the pressing portions 14G1 (in the present invention) due to distortion generated in the piezoelectric element 16 (Which also serves as a shape variable portion) bends and an inertial force is generated in the piezo rotor 14G.

  In the present embodiment, the piezo rotor 14G may include four or more pressing portions 14G1 extending radially from the rotation center, and these may form an equal angle with each other. Further, two of the pressing portions 14G1 shown in FIG. 13 may be formed to be deflectable, and the piezoelectric element 16 may be attached, or all (three) pressing portions 14G1 may be formed to be flexible, The piezoelectric element 16 may be attached.

  According to the present embodiment, the three pressing portions 14G1 extend radially from the rotation center of the piezo rotor 14G so as to form an equal angle with each other, and the flex spline 12 is pressed at each end portion, whereby the piezo rotor. Since 14G can abut evenly on the inner peripheral surface of the flexspline 12 at three locations on the circumference, the piezo rotor 14G can be stably rotated even if the circular spline 11 is not provided with a structure for supporting the piezo rotor 14G. Can do.

<Embodiment 4>
FIG. 14 is a partially enlarged view of the piezo rotor according to the fourth embodiment. This embodiment is an embodiment in which the piezo rotor 14 shown in FIG. 1 is changed, and a mounting groove 14b2 is formed in the pressing portion 14b instead of the movable portion 14c being not provided in the pressing portion 14b. An earth electrode 17e is inserted and fixed in the mounting groove 14b2.

  A pair of piezoelectric elements 16 are attached to both surfaces of the ground electrode 17e so as to sandwich the ground electrode 17e. Both piezoelectric elements 16 have the same specifications. Furthermore, the application electrodes 17c and 17d are arranged so as to abut on the surface of each piezoelectric element 16 that is not in contact with the ground electrode 17e.

  In the configuration described above, the ground electrode 17e is always connected to the negative side of the DC power supply. One of the application electrodes 17c and 17d is connected to the positive side of the DC power supply, and the other is connected to the negative side of the DC power supply. Therefore, a voltage from a DC power source is applied to only one of the pair of piezoelectric elements 16 provided with the ground electrode 17e interposed therebetween, and no voltage is applied to the other.

  As a result, distortion occurs only in the piezoelectric element 16 to which a voltage is applied, and bending occurs in either direction (upward or downward in FIG. 14) together with the ground electrode 17e.

  By switching the side of the application electrodes 17c and 17d that is connected to the positive side of the DC power source and switching the piezoelectric element 16 to which the voltage is applied, the bending direction can be reversed. As a result, the rotation direction of the piezo rotor 14 can be selected and the rotation direction of the output shaft portion 13d can be switched. Further, according to the configuration described above, it is not necessary to form the movable portion 14 c in the piezo rotor 14.

<Embodiment 5>
A harmonic gear device 21 according to Embodiment 5 will be described with reference to FIGS. 15 and 16. In this embodiment, in Embodiment 1, a vibration system 24 including an elastic member 22 that can vibrate in the rotation direction of the piezo rotor 14 (rotation pressing member) and a vibration weight 23 is attached to the piezo rotor 14, and the controller 2 (rotation control device). ) Is different from the harmonic gear device 1 according to the first embodiment only in that the piezoelectric element 16 (strain element) generates a strain in the vicinity of the resonance frequency of the vibration system 24, and only the difference will be described below.

  A gap 25 is formed in the output rotation axis direction between the tip of the flex spline 12 and the inner end face of the bottom part 11a of the circular spline 11, and the inner peripheral surface of the ring-like part 11b of the circular spline 11 is opposed to the gap 25. Thus, a large-diameter annular groove 11e is formed, and a storage space 26 for storing the vibration system 24 is formed. An elastic member 22 capable of vibrating in the rotational direction of the piezo rotor 14 in the storage space 26 is erected outward in the radial direction at the contact portion 14b1 of the pressing portion 14b, and a vibrating weight 23 is annularly formed at the free end of the elastic member 22. It is fixed in the groove 11e. That is, the vibration system 24 protrudes radially outward in the same phase in the circumferential direction as the contact portion 14 b 1 of the pressing portion 14 b and is fixed to the piezo rotor 14, and the vibration system 24 is stored in the storage space 26.

  When the controller 2 applies, for example, an electric signal of a voltage having a gradually decreasing gradient with respect to the voltage rising gradient to the bimorph type piezoelectric element 16 at a high frequency, the piezoelectric element 16 is applied, for example, clockwise to the side to which the voltage is applied. Therefore, the movable portion 14c bends with a small deflection acceleration at the time of return relative to the deflection acceleration at the time of deformation, and an inertial force is continuously generated in the piezo rotor 14 (FIG. 16A). Since the vibration weight 23 has a mass and the elastic member 22 has an elastic coefficient, when vibration is input to the elastic member 22 of the vibration system 24 from the pressing member 14b, the vibration weight 23 swings like a pendulum (FIG. 16B). )). When the vibration of the vibration weight 23 is detected by a detection means (not shown), the controller 2 changes the frequency or duty ratio of the electric signal so that the pressing portion 14b can also swing (FIG. 16 (c)). It is made to rotate to a direction (FIG.16 (d)).

  That is, the controller 2 starts to apply a voltage to the piezoelectric element 16 when the vibration weight 23 starts to swing clockwise (rotation direction), and returns the deflection when the vibration weight 23 is most accelerated in the clockwise direction. Start decreasing the voltage. Then, the controller 2 reduces the frequency of the electric signal to around the resonance frequency of the vibration system 24 in accordance with the vibration of the vibration weight 23. As a result, the vibration weight 23 vibrates greatly to apply a larger rotational torque to the piezo rotor 14, and the output torque from the flex spline 12 can be increased and stabilized. Furthermore, since the vibration system 24 protrudes radially outward with the same phase in the circumferential direction as the contact portion 14 b of the piezo rotor 14 and is fixed to the piezo rotor 14, the vibration weight 23 that vibrates greatly is the inner peripheral surface of the flexspline 12. A large rotational torque can be reliably applied to the piezo rotor 14 by the abutting portion 14b abutting on the piezoelectric rotor 14.

When the piezo rotor 14 starts to rotate in the clockwise direction, the controller 2 rotates according to the rotational position of the flexspline 12 based on the rotational speed of the output shaft portion 13d detected by the rotational speed sensor 3, as in the first embodiment. The voltage, frequency, duty ratio, etc. of the electric signal supplied to the piezoelectric element 16 are controlled so as to reduce the nonuniformity.

In this embodiment, the vibration system 24 is attached to the abutting portion 14b1 of the pressing portion 14b of the piezo rotor 14. However, the vibration system 24 may be attached to the rotation center portion of the piezo rotor 14 so as to protrude radially outward on the opposite side of the movable body 14c. Good.

<Modification of Embodiment 5>
In the first modification of the fifth embodiment, as shown in FIG. 17, in the second embodiment, the elastic member 22 that can vibrate in the rotational direction of the piezo rotor 14E has a contact portion of the pressing portion integrally formed with the movable portion 14E2. The vibrating weight 23 is fixed to the free end of the elastic member 22 and is erected outwardly in the radial direction on the weight portion 14 </ b> E <b> 3. That is, the vibration system 24 is fixed to the piezo rotor 14E so as to protrude outward in the radial direction with the same phase in the circumferential direction as the contact portion of the pressing portion.

  In the second modification of the fifth embodiment, as shown in FIG. 18, in the third embodiment, the vibration system 24 is fixed to the weight portion 14G2 that also serves as the contact portion of the three pressing portions 14G1 so as to protrude outward in the radial direction. Has been.

<Other embodiments>
The present invention is not limited to the above-described embodiments, and can be modified or expanded as follows.

  The strain element attached to the piezo rotor 14 is not limited to the piezoelectric element 16, and any one of a magnetostrictive element, an electrostrictive element, a shape memory element, and the like may be used. The shape memory element in this case is an element that generates strain by applying an electric signal to the shape memory material and heating it. For the strained portion of the strain element, a metal material, an organic polymer material, a ceramic material, or a composite material thereof can be used.

Further, the flexspline 12 and the gear cover 13 may be integrally formed.
Alternatively, the flex spline 12 may be fixed so as not to rotate, and a rotational output may be obtained from the circular spline 11.

  Further, since the inertial force generated in the piezo rotor 14 is determined by the weight of the movable part 14c and the acceleration at the time of bending, the weight part 14c1 formed at the tip of the movable part 14c is not necessarily required, and the movable part 14c itself Depending on the weight and the acceleration at the time of bending, it may be provided as appropriate.

  Further, in order to reduce unevenness in the rotational speed due to the rotational position of the flexspline 12, the average rotational speed of the flexspline 12 at all rotational positions is calculated, and the rotational speed detected by the rotational speed sensor 3 and the rotation of the flexspline 12 are calculated. The electric signal supplied to the piezoelectric element 16 may be controlled in accordance with the deviation from the average speed.

  Moreover, the attachment position with respect to the press part 14b of the movable part 14c of the piezo rotor 14 may be any position as long as it is between the both ends of the press part 14b, and the protruding direction is not necessarily perpendicular to the press part 14b. Also good.

  In addition, the strain direction of the piezoelectric element 16 when a voltage is applied can be used in any direction. Therefore, the attachment position and the attachment direction of the piezoelectric element 16 to the movable portion 14c are not limited to the configuration disclosed in the above-described embodiment.

  In the drawings, 1 is a harmonic gear device, 2 is a controller (rotation control means), 3 is a rotation speed sensor (rotation speed detection means), 5 is a reference voltage setting unit (reference speed setting means), 11 is a circular spline, and 11b is Ring-shaped portion, 11c is inner teeth (inner teeth), 11d is a through hole (shaft holding portion), 12 is a flex spline, 12a is outer teeth (outer teeth), 14, 14D, 14E, 14F, and 14G are piezo rotors (wave motions) Generator, rotating pressing member), 14b and 14G1 are pressing parts, 14c and 14E2 are movable parts (shape variable parts), 16 is a piezoelectric element (straining element) 22 is an elastic member, 23 is a vibrating weight, and 24 is a vibrating system. Show.

Claims (10)

A circular spline having a ring-shaped portion and having a plurality of internal teeth on the inner peripheral surface of the ring-shaped portion;
It is formed so as to have a flexible annular portion, and has a smaller number of outer teeth than the inner teeth of the circular spline on the outer peripheral surface of the annular portion, and is arranged radially inward of the circular spline. A flexspline in which the outer teeth face the inner teeth;
By pressing several locations on the inner peripheral surface of the flexspline radially outward toward the circular spline, only a part of the outer teeth are engaged with the inner teeth and the flexspline is pressed against the flexsplines. A wave generator for rotating the part;
With
When the pressing portion in the flexspline is rotated by the wave generator, the position on the circumference where the external teeth and the internal teeth mesh is moved while the flexspline is bent, and the circular spline and By fixing one of the flexsplines, in the other of the circular spline and the flexspline, the rotation drive device that outputs the rotation by the wave generator decelerated,
The wave generator is
Inwardly in the radial direction of the flexspline, the flexspline is provided so as to be rotatable with respect to the flexspline. A rotation pressing member for pressing,
The rotary pressing member is formed with a deformable shape variable portion,
A strain element that generates strain according to an electrical signal is attached to the shape variable portion,
A strain is repeatedly generated in the strain element, and the shape variable portion is deformed with repeated acceleration, whereby an inertial force is continuously generated in the rotary pressing member, and the rotary pressing member is caused by the inertial force. A rotation drive device characterized by rotating.   2. The rotation drive device according to claim 1, wherein the strain element is formed of any one of a piezoelectric element, a magnetostrictive element, an electrostrictive element, and a shape memory element. The rotary pressing member has a pressing portion formed in a long shape, and is provided to be rotatable around a central portion in the longitudinal direction of the pressing portion. The flexspline is in contact portions at both ends of the pressing portion. The outer teeth are engaged with the inner teeth formed at two locations facing each other across the center of the circular spline, and the longitudinal direction of the pressing portion extends from the middle portion of the pressing portion. A movable portion protruding in a different direction as the shape variable portion, the strain element is attached to the movable portion,
3. The rotation drive device according to claim 1, wherein the movable portion is bent in a rotation direction due to a strain generated in the strain element, and an inertial force is generated in the rotation pressing member. The rotary pressing member is formed in a long shape, is provided so as to be rotatable around a central portion in the longitudinal direction, and contacts the inner peripheral surface of the flexspline at the contact portions at both ends, thereby The movable part that is meshed with the internal teeth formed at two locations facing each other across the center of the circular spline and that can be bent in the rotational direction between the rotational center and at least one end is variable in shape. Formed as a part, the strain element is attached to the movable part,
3. The rotation drive device according to claim 1, wherein the movable portion is bent by a strain generated in the strain element, and an inertial force is generated in the rotation pressing member. The rotation pressing member extends radially from the rotation center so that three or more pressing portions form an equal angle with each other, and the contact portion of each end portion of the pressing portion is formed on the inner peripheral surface of the flexspline. By abutting, the outer teeth are meshed with a plurality of locations on the circumference of the inner teeth, and at least one of the pressing portions is formed as the shape variable portion so as to be able to bend in the rotation direction, and the strain element is Installed,
3. The rotation drive device according to claim 1, wherein the pressing portion is bent by a strain generated in the strain element, and an inertial force is generated in the rotation pressing member. A vibration system attached to the rotation pressing member and including an elastic member capable of elastic deformation in the rotation direction of the rotation pressing member and a vibration weight;
6. The rotary drive device according to claim 1, further comprising: a control device that generates a strain in the strain element in the vicinity of a resonance frequency of the vibration system.   The rotation drive device according to claim 6, wherein the vibration system protrudes radially outward at the same phase in the circumferential direction as the contact portion of the rotation pressing member and is fixed to the rotation pressing member. .   8. The shaft holding portion that supports the rotary pressing member so as to be rotatable about a rotation center is formed in the circular spline or the flex spline. 9. Rotation drive device. A rotational speed detecting means for detecting an output rotational speed of the circular spline or the flexspline;
Rotation control means for controlling an electric signal supplied to the strain element;
With
The rotation control means includes
Based on the output rotation speed detected by the rotation speed detection means, an electric signal supplied to the strain element is controlled so as to reduce unevenness of the output rotation speed due to the rotation position of the circular spline or the flexspline. The rotation drive device according to claim 1, wherein the rotation drive device is a rotation drive device. Reference speed setting means for forming a reference rotational speed of the circular spline or the flexspline,
The rotation control means includes
An electrical signal supplied to the strain element is controlled in accordance with a deviation between the output rotation speed detected by the rotation speed detection means and the reference rotation speed set by the reference speed setting means. The rotation drive device according to any one of claims 1 to 8.

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