Piezoelectric motor, piezoelectric motor control method, and robot

Abstract

To provide a piezoelectric motor, a piezoelectric motor control method, and a robot that can exhibit excellent driving efficiency.SOLUTION: A piezoelectric motor includes a driven body that rotates around a rotation axis, a first piezoelectric vibrator that transmits driving force to the driven body, a moving mechanism that moves in a direction in which the first piezoelectric vibrator approaches to and separates from the rotation axis, and a second piezoelectric vibrator that transmits driving force to the moving mechanism. The moving mechanism includes a screw shaft that is arranged along the direction and rotates around an axis by the driving force of the second piezoelectric vibrator, and a holding portion which is threaded with the screw shaft and holds the first piezoelectric vibrator.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a piezoelectric motor, a control method for a piezoelectric motor, and a robot. [Background technology]

[0002] For example, Patent Document 1 discloses a vibration actuator having three vibrator parts arranged at equal intervals on the same circumference and a ring-shaped driven body that rotates when driven by these three vibrator parts. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-068112 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the vibration actuator of Patent Document 1, the three vibrator parts are located on the same circumference. Therefore, if the diameter of the driven body is large, the vibration actuator is suitable for high torque / low speed, and conversely, if the diameter of the driven body is small, the vibration actuator is suitable for low torque / high speed. Therefore, it is difficult to drive with excellent energy efficiency over a wide speed range. [Means for solving the problem]

[0005] The piezoelectric motor of the present invention includes a driven body that rotates around a rotation axis, A first piezoelectric vibrator that transmits a driving force to the driven body; a moving mechanism that moves the first piezoelectric vibrator in a direction toward or away from the rotation shaft; and a second piezoelectric vibrator that transmits a driving force to the movement mechanism.

[0006] The method for controlling a piezoelectric motor of the present invention includes: A first piezoelectric vibrator that transmits a driving force to the driven body; a moving mechanism that moves the first piezoelectric vibrator in a direction toward or away from the rotation shaft; A method for controlling a piezoelectric motor having a second piezoelectric vibrator that transmits a driving force to the moving mechanism, When accelerating the driven body, As the rotation speed of the driven body increases, the first piezoelectric vibrator is moved in a direction approaching the rotation shaft.

[0007] The robot of the present invention includes a first member and a second member which are interconnected; and the piezoelectric motor that displaces the second member relative to the first member. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a piezoelectric motor according to a first embodiment of the present invention. [Diagram 2] 2 is a plan view of a base of the piezoelectric motor of FIG. 1 as viewed from below. [Diagram 3] FIG. 2 is a plan view showing a first piezoelectric vibrator and a second piezoelectric vibrator. [Figure 4] FIG. 4 is a diagram showing a drive signal applied to a piezoelectric vibrator. [Diagram 5] 4 is a plan view showing a driving state of a first piezoelectric vibrator and a second piezoelectric vibrator. FIG. [Figure 6] FIG. [Figure 7] 4 is a graph showing the relationship between rotation speed and torque. [Figure 8] FIG. 11 is a plan view showing a moving mechanism of a piezoelectric motor according to a second embodiment. [Figure 9] FIG. 4 is a perspective view showing a slider of the moving mechanism. [Figure 10] FIG. 11 is a perspective view showing a robot according to a third embodiment of the present invention. [Figure 11]4 is a cross-sectional view showing a joint portion between a first arm and a second arm. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A piezoelectric motor, a control method for a piezoelectric motor, and a robot according to the present invention will be described in detail below with reference to preferred embodiments shown in the accompanying drawings.

[0010] First Embodiment FIG. 1 is a cross-sectional view showing a piezoelectric motor according to a first embodiment of the present invention. FIG. 2 is a plan view showing a base of the piezoelectric motor of FIG. 1 from below. FIG. 3 is a plan view showing a first piezoelectric vibrator and a second piezoelectric vibrator. FIG. 4 is a diagram showing a drive signal applied to the piezoelectric vibrator. FIG. 5 is a plan view showing a drive state of the first piezoelectric vibrator and the second piezoelectric vibrator. FIG. 6 is a plan view showing a biasing member. FIG. 7 is a graph showing the relationship between rotation speed and torque.

[0011] 3, 5, and 6 each show three mutually orthogonal axes, the X-axis, the Y-axis, and the Z-axis, as coordinate axes specific to the piezoelectric vibrator. In the following, the direction along the X-axis will also be referred to as the X-axis direction, the direction along the Y-axis as the Y-axis direction, and the direction along the Z-axis as the Z-axis direction. The side of each axis indicated by an arrow will also be referred to as the "plus side," and the side opposite the arrow as the "minus side."

[0012] The piezoelectric motor 100 shown in Figure 1 has a base 200, a rotor 300 as a driven body rotatable around a rotation axis O relative to the base 200, a first piezoelectric vibrator 400A that rotates the rotor 300 around the rotation axis O, a moving mechanism 500 that moves the first piezoelectric vibrator 400A in the radial direction of the rotor 300, a second piezoelectric vibrator 400B that transmits driving force to the moving mechanism 500, an encoder (not shown) that detects the amount of rotation of the rotor 300, a case 700 that houses these, and a control device 800 that controls the driving of the first and second piezoelectric vibrators 400A, 400B.

[0013] In the piezoelectric motor 100, the driving force of the first piezoelectric vibrator 400A is transmitted to the rotor 300, causing the rotor 300 to rotate around the rotation axis O. In addition, the driving force of the second piezoelectric vibrator 400B is transmitted to the moving mechanism 500, causing the first piezoelectric vibrator 400A to move in the radial direction of the rotor 300. Then, the position of the first piezoelectric vibrator 400A is changed according to the rotation speed of the rotor 300 and the magnitude of the output load. With this configuration, for example, compared to the conventional case in which the position of the first piezoelectric vibrator 400A is fixed, a wider range of rotation speed of the rotor 300 can be secured. In addition, by changing the position of the first piezoelectric vibrator 400A according to the required rotation speed and required torque, excellent driving efficiency can be achieved.

[0014] The rotor 300 has an output shaft 310 extending along the rotation axis O, and a disk-shaped rotor body 320 fixed to the output shaft 310. The rotor 300 is supported by the base 200 and the case 700 via bearings B1, and is rotatable relative to them about the rotation axis O. In addition, both ends of the output shaft 310 protrude from the case 700, and are connected to separate members at those portions.

[0015] The base 200 is disposed above the rotor 300. The base 200 has a recess 220 that opens on its upper surface, and a rod 710 extending from the case 700 is inserted into the recess 220. This restricts the rotation of the base 200 around the rotation axis O relative to the case 700. The base 200 is biased toward the rotor 300 by a compression spring S disposed on the rod 710. The base 200 has an annular recess 210 that opens on its lower surface. The recess 210 is disposed concentrically with the output shaft 310 so as to surround the output shaft 310. The first piezoelectric vibrator 400A and a part of the moving mechanism 500 are disposed inside the recess 210. That is, the recess 210 functions as a housing that houses the first piezoelectric vibrator 400A and the moving mechanism 500.

[0016] The movement mechanism 500 has a plurality of ball screws 510 arranged around a rotation axis O, and a gear 520 that drives all of the ball screws 510 collectively. Each ball screw 510 has a screw base 511 fixed to the base 200, a screw shaft 512 rotatably supported by the screw base 511, and a slider 513 that moves in the axial direction of the screw shaft 512 by the rotation of the screw shaft 512. The slider 513 also holds the first piezoelectric vibrator 400A. Each screw shaft 512 has a head 512a that protrudes toward the outer periphery of the base 200. Each head 512a has teeth formed on its outer periphery and is screwed with the gear 520 via the teeth.

[0017] The gear 520 is disposed on the upper side of the base 200. The gear 520 is supported by the base 200 via a bearing B3 and is rotatable around a rotation axis O relative to the base 200. The gear 520 has an annular main body 521 that is slightly larger than the base 200, and an annular flange 522 that protrudes downward from the outer edge of the main body 521 and is disposed so as to surround the base 200. The flange 522 has teeth formed on its lower surface and is screwed with the head 512a of each screw shaft 512 via the teeth. In addition, the second piezoelectric vibrator 400B is pressed against the inner peripheral surface 521a of the main body 521.

[0018] As shown by the solid arrow in FIG. 1, when the gear 520 rotates forward around the rotation axis O due to the driving force of the second piezoelectric vibrator 400B, all the screw shafts 512 rotate forward around the central axis J, and accordingly, all the sliders 513 move along the central axis J toward the inner periphery, i.e., toward the rotation axis O. As a result, all the first piezoelectric vibrators 400A move together in a direction toward the rotation axis O. On the other hand, as shown by the dashed arrow in FIG. 1, when the gear 520 rotates backward around the rotation axis O due to the driving force of the second piezoelectric vibrator 400B, all the screw shafts 512 rotate backward around the central axis J, and accordingly, all the sliders 513 move along the central axis J toward the outer periphery, i.e., in a direction away from the rotation axis O. As a result, all the first piezoelectric vibrators 400A move together in a direction away from the rotation axis O.

[0019] In this way, according to the moving mechanism 500, all the first piezoelectric vibrators 400A can be moved collectively by simply rotating the gear 520. Also, if the rotation of the screw shaft 512 is stopped, the first piezoelectric vibrators 400A can be stopped in place. This simplifies the configuration of the moving mechanism 500. Also, since the distances from the rotation axis O of all the first piezoelectric vibrators 400A are uniform and an equal driving force is transmitted from each of the first piezoelectric vibrators 400A to the rotor 300, the rotor 300 can be rotated smoothly with excellent energy efficiency.

[0020] The moving mechanism 500 has been described above, but the moving mechanism 500 is not particularly limited as long as it can move the first piezoelectric vibrator 400A in a direction approaching or moving away from the rotation axis O. For example, as shown in FIG. 2, in this embodiment, the central axis J of each screw shaft 512 is aligned along the radial direction of the rotor 300, but is not limited to this, and may be inclined with respect to the radial direction of the rotor 300. In addition, in this embodiment, a plurality of ball screws 510 are arranged, but is not limited to this, and the number of ball screws 510 may be one. In other words, the number of first piezoelectric vibrators 400A may be one. In addition, in this embodiment, a plurality of ball screws 510 are arranged at equal intervals around the rotation axis O, but may be arranged at uneven intervals.

[0021] Next, the first and second piezoelectric vibrators 400A and 400B will be described. The first and second piezoelectric vibrators 400A and 400B have the same configuration. As shown in Fig. 3, the first and second piezoelectric vibrators 400A and 400B each have a vibration part 411, a support part 412 that supports the vibration part 411, a connection part 413 that connects the vibration part 411 and the support part 412, and a convex transmission part 414 arranged at the tip of the vibration part 411.

[0022] The vibration part 411 has a thickness direction in the Z-axis direction and is a plate-like shape extending in the XY plane including the X-axis and the Y-axis. The vibration part 411 has driving piezoelectric elements 420A to 420F and a detection piezoelectric element 420G for detecting the vibration of the vibration part 411. In the center of the vibration part 411, the piezoelectric elements 420C and 420D are arranged side by side in the Y-axis direction. On the positive side of the X-axis direction of the piezoelectric elements 420C and 420D, the piezoelectric elements 420A and 420B are arranged side by side in the Y-axis direction, and on the negative side of the X-axis direction, the piezoelectric elements 420E and 420F are arranged side by side in the Y-axis direction. Each of these piezoelectric elements 420A to 420F expands and contracts in the Y-axis direction when electricity is applied. However, the number and arrangement of the driving piezoelectric elements are not particularly limited as long as they can excite the vibration part 411 to a desired vibration.

[0023] The detection piezoelectric element 420G is disposed between the piezoelectric elements 420C and 420D. The piezoelectric element 420G receives an external force corresponding to the vibration of the vibrating portion 411, and outputs a detection signal corresponding to the received external force. Therefore, the driving state of the piezoelectric motor 100 can be detected based on the detection signal output from the piezoelectric element 420G. The number and arrangement of the detection piezoelectric elements are not particularly limited as long as they can detect the vibration of the vibrating portion 411. The detection piezoelectric elements may be omitted.

[0024] These piezoelectric elements 420A to 420F are configured, for example, by sandwiching a piezoelectric body between a pair of electrodes. The constituent material of the piezoelectric body is not particularly limited, and for example, piezoelectric ceramics such as lead zirconate titanate (PZT), barium titanate, lead titanate, potassium niobate, lithium niobate, lithium tantalate, sodium tungstate, zinc oxide, barium strontium titanate (BST), strontium bismuth tantalate (SBT), lead metaniobate, lead scandium niobate, etc. may be used as the piezoelectric body, in addition to the above-mentioned piezoelectric ceramics, polyvinylidene fluoride, quartz, etc. may also be used. The method of forming the piezoelectric body is not particularly limited, and it may be formed from a bulk material, or may be formed using a sol-gel method or a sputtering method.

[0025] The transmission part 414 is provided at the tip of the vibration part 411 and protrudes from the vibration part 411 to the negative side in the Y-axis direction. In the first piezoelectric vibrator 400A, the transmission part 414 is in contact with the upper surface of the rotor main body 310. Therefore, the vibration of the vibration part 411 is transmitted to the rotor 300 via the transmission part 414. In the second piezoelectric vibrator 400B, the transmission part 414 is in contact with the inner circumferential surface 521a of the gear 520. Therefore, the vibration of the vibration part 411 is transmitted to the gear 520 via the transmission part 414.

[0026] For example, when the drive signal V1 shown in FIG. 4 is applied to the piezoelectric elements 420A and 420F, the drive signal V2 is applied to the piezoelectric elements 420C and 420D, and the drive signal V3 is applied to the piezoelectric elements 420B and 420E, as shown in FIG. 5, the vibration part 411 vibrates in an expanding and contracting manner in the Y-axis direction while vibrating in a bending manner in the X-axis direction, and these vibrations are combined, and the tip of the transmission part 414 performs an elliptical motion that draws an elliptical orbit in the counterclockwise direction as shown by the arrow A1. In the first piezoelectric vibrator 400A, the rotor 300 is sent out in the circumferential direction by such an elliptical motion of the transmission part 414, and the rotor 300 rotates forward around the rotation axis O. On the other hand, in the second piezoelectric vibrator 400B, the gear 520 is sent out in the circumferential direction by such an elliptical motion of the transmission part 414, and the gear 520 rotates forward around the rotation axis O. When the waveforms of the drive signals V1 and V3 are switched, the rotor 300 and the gear 520 rotate in the opposite directions. The term "elliptical motion" as used herein includes not only motion whose path coincides with an ellipse, but also motion whose path is slightly deviated from an ellipse, such as a circle or oval.

[0027] For convenience of explanation, the stretching vibration of vibrating part 411 in the Y-axis direction is also referred to as "reciprocating vibration", and the bending vibration in the X-axis direction is also referred to as "bending vibration". The reciprocating vibration is excited by application of drive signal V2 to piezoelectric elements 420C and 420D, and the bending vibration is excited by application of drive signals V1 and V3 to piezoelectric elements 420A, 420B, 420E, and 420F. Therefore, the reciprocating vibration is controlled by drive signal V2, and the bending vibration is controlled by drive signals V1 and V3.

[0028] As shown in FIG. 6, the first piezoelectric vibrator 400A is held by the slider 513 via the biasing member 490A. The biasing member 490A biases the first piezoelectric vibrator 400A toward the rotor 300, and presses the transmission part 414 against the upper surface of the rotor main body 320. This allows the driving force of the first piezoelectric vibrator 400A to be efficiently transmitted to the rotor 300. The second piezoelectric vibrator 400B is held by the base 200 via the biasing member 490B. The biasing member 490B biases the second piezoelectric vibrator 400B toward the gear 520, and presses the transmission part 414 against the inner peripheral surface 521a of the gear 520. This allows the driving force of the second piezoelectric vibrator 400B to be efficiently transmitted to the gear 520.

[0029] The biasing members 490A and 490B have a holding portion 491 that holds the support portion 412, a fixed portion 492 that is fixed to an object, and spring groups 493 and 494 that connect the holding portion 491 and the fixed portion 492. The biasing member 490A is fixed to the slider 513 with the spring groups 493 and 494 in a deflected state, and biases the first piezoelectric vibrator 400A toward the rotor 300 by using the restoring forces of the spring groups 493 and 494. On the other hand, the biasing member 490B is fixed to the base 200 with the spring groups 493 and 494 in a deflected state, and biases the second piezoelectric vibrator 400B toward the gear 520 by using the restoring forces of the spring groups 493 and 494. However, the configuration of the biasing members 490A and 490B is not particularly limited. Also, the biasing members 490A and 490B may be omitted. For convenience of explanation, the biasing members 490A and 490B are omitted from the illustrations except in FIG.

[0030] In this way, the first piezoelectric vibrator 400A is pressed against the rotor 300 by the biasing member 490A. Therefore, when the driving of the first piezoelectric vibrator 400A is stopped, the first piezoelectric vibrator 400A acts as a brake that prevents the rotor 300 from rotating, and the rotation angle of the rotor 300 can be maintained. Similarly, the second piezoelectric vibrator 400B is pressed against the gear 520 by the biasing member 490B. Therefore, when the driving of the second piezoelectric vibrator 400B is stopped, the second piezoelectric vibrator 400B acts as a brake that prevents the gear 520 from rotating, and the rotation angle of the gear 520 can be maintained. In this way, according to the piezoelectric motor 100, the first and second piezoelectric vibrators 400A and 400B function as both a driving source and a brake, so there is no need to provide a brake separately in addition to the driving source. Therefore, the piezoelectric motor 100 can be made smaller in size.

[0031] The control device 800 is, for example, configured from a computer, and includes a processor for processing information, a memory communicatively connected to the processor, and an external interface. The memory also stores a program executable by the processor, and the processor reads and executes the program stored in the memory. Such a control device 800 receives a command from a host computer (not shown) and drives the first and second piezoelectric vibrators 400A and 400B based on the command.

[0032] In this embodiment, all the first piezoelectric vibrators 400A are controlled collectively, and all the second piezoelectric vibrators 400B are controlled collectively. This simplifies the circuit configuration. However, this is not limited to this, and for example, the first and second piezoelectric vibrators 400A and 400B may be divided into several groups and controlled for each group, or all the first and second piezoelectric vibrators 400A and 400B may be controlled independently.

[0033] The configuration of the piezoelectric motor 100 has been described above. In such a piezoelectric motor 100, as described above, the first piezoelectric vibrator 400A can be moved along the radial direction of the rotor 300 by driving the second piezoelectric vibrator 400B. In this way, by moving the first piezoelectric vibrator 400A along the radial direction of the rotor 300, the separation distance D between the rotation axis O and the first piezoelectric vibrator 400A can be changed. This makes it possible to ensure a wider rotation speed range of the rotor compared to a conventional piezoelectric motor in which the separation distance D is fixed.

[0034] 7, for example, by moving the first piezoelectric vibrator 400A to the outermost side and setting the separation distance D to the maximum value Dmax, the rotor 300 can be rotated with a low rotation speed but a large torque. Conversely, by moving the first piezoelectric vibrator 400A to the innermost side and setting the separation distance D to the minimum value Dmin, the rotor 300 can be rotated with a low torque but a high rotation speed. Therefore, according to the piezoelectric motor 100, for example, like a CVT (Continuously Variable Transmission) of an automobile, the position of the first piezoelectric vibrator 400A can be changed according to the required rotation speed and required torque to select an optimal driving state, and therefore excellent driving efficiency can be exhibited.

[0035] For example, when accelerating the rotor 300 from a stopped state, a larger torque is required compared to when rotating the rotor 300 at a constant speed. In this way, when a larger torque is required, the rotor 300 can be accelerated with excellent drive efficiency by increasing the separation distance D. Then, by gradually decreasing the separation distance D as the rotation speed increases, the rotor 300 can be accelerated to a higher speed range. In this way, when accelerating the rotor 300, the first piezoelectric vibrator 400A is moved in a direction approaching the rotation axis O as the rotation speed of the rotor 300 increases, so that the rotor 300 can be accelerated with excellent drive efficiency.

[0036] Also, in the case where only a small torque is required to maintain the rotational speed, the rotational speed can be maintained with less energy by making the separation distance D sufficiently small.

[0037] Also, when decelerating and stopping the rotor 300, a large torque is required, just as when accelerating. Therefore, by gradually increasing the separation distance D as the rotation speed decreases, the rotor 300 can be decelerated and stopped with excellent drive efficiency. In this way, when decelerating the rotor 300, by moving the first piezoelectric vibrator 400A in a direction away from the rotation axis O as the rotation speed of the rotor 300 decreases, the rotor 300 can be decelerated with excellent drive efficiency.

[0038] For example, there may be cases where the first piezoelectric vibrator 400A needs to be moved to a predetermined position before the piezoelectric motor 100 is driven. In this case, the first piezoelectric vibrator 400A can be easily moved without rotating the rotor 300 by driving the second piezoelectric vibrator 400B while the first piezoelectric vibrator 400A is reciprocatingly vibrating. As described above, when the first piezoelectric vibrator 400A is not driven, the first piezoelectric vibrator 400A is pressed against the rotor 300. Therefore, when the first piezoelectric vibrator 400A is not driven, it is difficult to move the first piezoelectric vibrator 400A. In addition, if the first piezoelectric vibrator 400A is driven with elliptical vibration, the rotor 300 rotates and the rotation angle fluctuates.

[0039] In contrast, when the first piezoelectric vibrator 400A is vibrating back and forth, no force is generated to send out the rotor 300, and the rotor 300 is prevented from rotating. Furthermore, the first piezoelectric vibrator 400A repeatedly comes into contact with and separates from the rotor 300, so that the brake is essentially released. Therefore, by driving the second piezoelectric vibrator 400B while the first piezoelectric vibrator 400A is vibrating back and forth, the first piezoelectric vibrator 400A can be easily moved without rotating the rotor 300.

[0040] The second piezoelectric vibrator 400B functions as a sensor that detects the output load applied to the output shaft 310 when stopped, i.e., when no driving is performed to move the first piezoelectric vibrator 400A. In other words, the second piezoelectric vibrator 400B also serves as a sensor that detects the output load. The output load applied to the output shaft 310 is transmitted to the second piezoelectric vibrator 400B through the rotor 300, the first piezoelectric vibrator 400A, and the moving mechanism 500. Therefore, a stress according to the output load is applied to the second piezoelectric vibrator 400B, and the detection piezoelectric element 420G is distorted by the stress, and a detection signal according to the distortion is output from the second piezoelectric vibrator 400B.

[0041] Therefore, the control device 800 may calculate the output load based on the detection signal output from the second piezoelectric vibrator 400B, calculate the optimum torque required to rotate the rotor 300 from the calculated output load, calculate the separation distance D at which the calculated optimum torque can be generated, and move the first piezoelectric vibrator 400A to the calculated separation distance D. This allows the rotor 300 to rotate with a torque that can counter the output load, and the piezoelectric motor 100 is driven smoothly. Note that, if the rotation speed of the rotor 300 cannot be maintained when the calculated optimum torque is generated, the separation distance D can also be controlled to provide a larger torque within a range in which the rotation speed can be maintained.

[0042] The piezoelectric motor 100 and its control method have been described above. As described above, the piezoelectric motor 100 includes the rotor 300 as a driven body rotating around the rotation axis O, the first piezoelectric vibrator 400A that transmits a driving force to the rotor 300, the moving mechanism 500 that moves the first piezoelectric vibrator 400A in a direction approaching or moving away from the rotation axis O, and the second piezoelectric vibrator 400B that transmits a driving force to the moving mechanism 500. With this configuration, a wider speed range can be secured by changing the position of the first piezoelectric vibrator 400A. In addition, by changing the position of the first piezoelectric vibrator 400A according to the required rotation speed and required torque, the rotor 300 can be rotated with excellent driving characteristics.

[0043] As described above, the moving mechanism 500 has the screw shaft 512 that rotates around its axis by the driving force of the second piezoelectric vibrator 400B and is arranged along the direction of approaching and moving away from the rotation axis O, and the slider 513 that is screwed onto the screw shaft 512 and serves as a holding section that holds the first piezoelectric vibrator 400A. By rotating the screw shaft 512, the first piezoelectric vibrator 400A can be moved in the direction of approaching and moving away from the rotation axis O. Furthermore, by stopping the rotation of the screw shaft 512, the first piezoelectric vibrator 400A can be held in place. This simplifies the configuration of the moving mechanism 500.

[0044] As described above, the moving mechanism 500 has a plurality of screw shafts 512 and a gear 520 that rotates the plurality of screw shafts 512 collectively. This allows the plurality of first piezoelectric vibrators 400A to be moved collectively in a direction approaching or moving away from the rotation axis O. This simplifies the configuration of the moving mechanism 500. In addition, the distances of all the first piezoelectric vibrators 400A from the rotation axis O are uniform, and uniform driving force is transmitted from each of the first piezoelectric vibrators 400A to the rotor 300, so the rotor 300 can be rotated smoothly with excellent energy efficiency.

[0045] As described above, the second piezoelectric vibrator 400B also serves as a sensor that detects the output load. This makes it possible to control the position of the first piezoelectric vibrator 400A so that a torque corresponding to the output load is generated. This improves the driving characteristics of the piezoelectric motor 100. Furthermore, the piezoelectric motor 100 can be made smaller than when a sensor is provided separately from the second piezoelectric vibrator 400B.

[0046] As described above, the control method for piezoelectric motor 100 includes rotor 300 that rotates around rotation axis O, first piezoelectric vibrator 400A that transmits driving force to rotor 300, movement mechanism 500 that moves first piezoelectric vibrator 400A in a direction toward or away from rotation axis O, and second piezoelectric vibrator 400B that transmits driving force to movement mechanism 500, and when accelerating rotor 300, moves first piezoelectric vibrator 400A in a direction toward rotation axis O as the rotation speed of rotor 300 increases. This allows rotor 300 to accelerate smoothly.

[0047] As described above, in the control method for the piezoelectric motor 100, when decelerating the rotor 300, the first piezoelectric vibrator 400A is moved in a direction away from the rotation axis O as the rotation speed of the rotor 300 decreases. This allows the rotor 300 to be decelerated smoothly.

[0048] Furthermore, as described above, when the first piezoelectric vibrator 400A is moved toward or away from the rotation axis O while the rotor 300 is stopped, the first piezoelectric vibrator 400A is vibrated back and forth in the direction toward or away from the rotor 300. This allows the first piezoelectric vibrator 400A to be moved smoothly toward or away from the rotation axis O.

[0049] <Second embodiment> Fig. 8 is a plan view showing a movement mechanism of a piezoelectric motor according to a second embodiment, and Fig. 9 is a perspective view showing a slider of the movement mechanism.

[0050] The piezoelectric motor of this embodiment is similar to the control method of the piezoelectric motor of the first embodiment described above, except for the configuration of the moving mechanism 500. In the following description, the present embodiment will be described with a focus on the differences from the previous embodiment, and the description of the similarities will be omitted. In FIG. 8, the same reference numerals are used for the same configurations as the previous embodiment.

[0051] As shown in FIG. 8 and FIG. 9, the moving mechanism 500 of this embodiment has a plurality of sliders 513 and a plurality of guides 530 that guide each slider 513 to be movable in the radial direction of the rotor 300. A first piezoelectric vibrator 400A and a second piezoelectric vibrator 400B are held by each slider 513. Each second piezoelectric vibrator 400B faces a circumferential direction perpendicular to the radial direction of the rotor 300, and is pressed against the base 200 by a biasing member 490B (not shown). Therefore, by driving the second piezoelectric vibrator 400B, the slider 513 can be moved in the radial direction of the rotor 300 along the guide 530. According to such a configuration, for example, compared to the first embodiment described above, the screw shaft 512 and the gear 520 are not necessary, so that the moving mechanism 500 can be made simple in configuration and small in size.

[0052] In this embodiment, as shown in FIG. 8, the multiple second piezoelectric vibrators 400B include a second piezoelectric vibrator 400B' facing the forward rotation direction C1 of the rotor 300, and a second piezoelectric vibrator 400B" facing the reverse rotation direction C2 of the rotor 300. With this configuration, when the rotor 300 rotates forward, the output load applied during rotation is applied to the second piezoelectric vibrator 400B" facing the reverse rotation direction of the rotor 300, and a detection signal corresponding to the output load is output from the second piezoelectric vibrator 400B". Conversely, When the rotor 300 rotates in the reverse direction, the output load applied during the rotation is applied to the second piezoelectric vibrator 400B' facing the forward rotation direction of the rotor 300, and a detection signal according to the output load is output from the second piezoelectric vibrator 400B'. Therefore, whether the rotor 300 rotates forward or backward, the output load applied at that time can be detected. However, the second piezoelectric vibrator 400B is not particularly limited, and for example, all the second piezoelectric vibrators 400B may face either the forward rotation direction or the reverse rotation direction of the rotor 300.

[0053] As described above, the moving mechanism 500 of the present embodiment has the slider 513 as a holding part that holds the first piezoelectric vibrator 400A and the second piezoelectric vibrator 400B and moves in a direction toward or away from the rotation axis O by the driving force of the second piezoelectric vibrator 400B. This simplifies the configuration of the moving mechanism 500.

[0054] The second embodiment as described above can also achieve the same effects as the first embodiment described above.

[0055] <Third embodiment> Fig. 10 is a perspective view showing a robot according to a third embodiment of the present invention, Fig. 11 is a cross-sectional view showing a joint portion between a first arm and a second arm.

[0056] 10 is capable of performing operations such as supplying, removing, transporting, and assembling precision equipment and the parts that constitute the equipment. Such a robot 1000 is a six-axis articulated robot, and has a base 1100 that is fixed to the floor or ceiling, and a manipulator 1200 that is supported by the base 1100.

[0057] The manipulator 1200 is a robotic arm that moves with multiple degrees of freedom by having multiple interconnected arms, and has a first arm 1210 rotatably connected to the base 1100, a second arm 1220 rotatably connected to the first arm 1210, a third arm 1230 rotatably connected to the second arm 1220, a fourth arm 1240 rotatably connected to the third arm 1230, a fifth arm 1250 rotatably connected to the fourth arm 1240, a sixth arm 1260 rotatably connected to the fifth arm 1250, and an end effector 1270 attached to the sixth arm 1260.

[0058] Any one selected from the first to sixth arms 1210 to 1260 and the end effector 1270 can be the first member, and any one selected from the rest of the first members can be the second member. Also, for example, if the end effector 1270 has a plurality of relatively movable members, such as a pair of claws for gripping a workpiece, one of the claws can be the first member and the other claw can be the second member. In the illustrated configuration, the first arm 1210 is the first member R1, and the second arm 1220 is the second member R2.

[0059] The robot 1000 also includes a first arm rotation mechanism 1310 that is disposed at the joint between the base 1100 and the first arm 1210 and rotates the first arm 1210 relative to the base 1100, a second arm rotation mechanism 1320 that is disposed at the joint between the first arm 1210 and the second arm 1220 and rotates the second arm 1220 relative to the first arm 1210, a third arm rotation mechanism 1330 that is disposed at the joint between the second arm 1220 and the third arm 1230 and rotates the third arm 1230 relative to the second arm 1220, and a fourth arm rotation mechanism 1330 that is disposed at the joint between the third arm 1230 and the fourth arm 1230. 240 and rotates the fourth arm 1240 relative to the third arm 1230, a fifth arm rotating mechanism 1350 arranged at the joint between the fourth arm 1240 and the fifth arm 1250 and rotates the fifth arm 1250 relative to the fourth arm 1240, a sixth arm rotating mechanism 1360 arranged at the joint between the fifth arm 1250 and the sixth arm 1260 and rotates the sixth arm 1260 relative to the fifth arm 1250, and an end effector driving mechanism 1370 that drives the end effector 1270. The robot 1000 also has a robot control unit 1400 that controls the driving of the first to sixth arm rotating mechanisms 1310 to 1360 and the end effector driving mechanism 1370.

[0060] A piezoelectric motor 100 is mounted as a power source in some or all of the first to sixth arm rotation mechanisms 1310-1360 and the end effector drive mechanism 1370, and the corresponding first to sixth arms 1210-1260 and end effector 1270 are driven by the piezoelectric motor 100. Therefore, the robot 1000 can enjoy the effects of the piezoelectric motor 100 described above, and can achieve excellent drive efficiency.

[0061] Here, as described above, in the piezoelectric motor 100, the first piezoelectric vibrator 400A moves and the separation distance D is variable. Therefore, the piezoelectric motor 100 also functions as a reducer by changing the separation distance D. In other words, the piezoelectric motor 100 also functions as a reducer. Therefore, as shown in FIG. 11, in the first arm rotation mechanism 1310, the case 700 is fixed to the first arm 1210, the output shaft 310 is fixed to the second arm 1220, and no reducer is provided between the rotor 300 and the second arm 1220 to reduce the rotation of the rotor 300. Therefore, the first arm rotation mechanism 1310 can be made smaller. The same applies to the second to sixth arm rotation mechanisms 1320 to 1360 and the end effector drive mechanism 1370.

[0062] As described above, the first piezoelectric vibrator 400A also functions as a brake that stops the rotation of the rotor 300 and maintains the relative positions of the connected arms by stopping its drive. Therefore, as shown in Fig. 11, the first arm rotation mechanism 1310 is not provided with a brake that stops the rotation of the rotor 300 in addition to the piezoelectric motor 100. This makes it possible to reduce the size of the first arm rotation mechanism 1310. The same applies to the second to sixth arm rotation mechanisms 1320 to 1360 and the end effector drive mechanism 1370.

[0063] As described above, the robot 1000 has the first arm 1210 as a first member and the second arm 1220 as a second member which are interconnected, and the piezoelectric motor 100 which displaces the second arm 1220 relative to the first arm 1210. Therefore, the robot 1000 can enjoy the effects of the piezoelectric motor 100 and can achieve excellent driving efficiency.

[0064] The third embodiment as described above can also achieve the same effects as the first embodiment described above.

[0065] The piezoelectric motor, the control method for the piezoelectric motor, and the robot of the present invention have been described above based on the illustrated embodiment, but the present invention is not limited thereto, and the configuration of each part can be replaced with any configuration having a similar function. Any other configuration may be added to the present invention. The embodiments may be appropriately combined. In the above embodiment, the configuration in which the control method for the piezoelectric motor is applied to a robot has been described, but the control method for the piezoelectric motor can also be applied to various electronic devices that require driving force other than robots, such as printers and projectors. [Explanation of symbols]

[0066] 100...piezoelectric motor, 200...base, 220...recess, 210...recess, 300...rotor, 310...output shaft, 320...rotor body, 400A...first piezoelectric vibrator, 400B...second piezoelectric vibrator, 400B'...second piezoelectric vibrator, 400B"...second piezoelectric vibrator, 411...vibration section, 412...support section, 413...connection section, 414...transmission section, 420A...piezoelectric element, 420B...piezoelectric element, 420C...piezoelectric element, 420D...piezoelectric element, 420E...piezoelectric element, 420F...piezoelectric element, 420G...piezoelectric element, 490A...urging member, 490B...urging member, 491...holding portion, 492...fixed portion, 493...spring group, 494...spring group, 500...movement mechanism, 510...ball screw, 511...screw base, 512...screw shaft, 512a...head, 513...slider, 520...gear, 521...main body, 521a...inner peripheral surface, 522...flange, 530...guide, 700...case, 71 0...rod portion, 800...control device, 1000...robot, 1100...base, 1200...manipulator, 1210...first arm, 1220...second arm, 1230...third arm, 1240...fourth arm, 1250...fifth arm, 1260...sixth arm, 1270...end effector, 1310...first arm rotating mechanism, 1320...second arm rotating mechanism, 1330...third arm rotating mechanism, 1340...fourth arm rotating mechanism , 1350...fifth arm rotation mechanism, 1360...sixth arm rotation mechanism, 1370...end effector drive mechanism, 1400...robot control unit, A1...arrow, B1...bearing, B3...bearing, C1...forward rotation direction, C2...reverse rotation direction, D...separation distance, Dmax...maximum value, Dmin...minimum value, J...center axis, O...rotation axis, R1...first member, R2...second member, S...compression spring, V1...drive signal, V2...drive signal, V3...drive signal

Claims

1. A driven body that rotates around a rotation axis; A first piezoelectric vibrator that transmits a driving force to the driven body; a moving mechanism that moves the first piezoelectric vibrator in a direction toward and away from the rotation shaft; 、 a second piezoelectric vibrator that transmits a driving force to the moving mechanism, The moving mechanism holds the first piezoelectric vibrator and the second piezoelectric vibrator. a piezoelectric motor having a holding portion that moves in the direction by the driving force of an electric vibrator; -

2. The moving mechanism rotates around an axis by the driving force of the second piezoelectric vibrator and moves along the direction. A screw shaft arranged as follows: a holding portion that is screwed onto the screw shaft and holds the first piezoelectric vibrator. Piezoelectric motor.

3. The moving mechanism includes a plurality of the screw shafts, and a gear for collectively rotating the plurality of screw shafts. -

4. 4. The piezoelectric transducer according to claim 1, wherein the second piezoelectric vibrator also serves as a sensor for detecting an output load.

13. The piezoelectric motor according to claim 1 .

5. A driven body that rotates around a rotation axis; A first piezoelectric vibrator that transmits a driving force to the driven body; a moving mechanism that moves the first piezoelectric vibrator in a direction toward and away from the rotation shaft; 、 A method for controlling a piezoelectric motor having a second piezoelectric vibrator that transmits a driving force to the moving mechanism. And, When accelerating the driven body, A direction in which the first piezoelectric vibrator approaches the rotation shaft as the rotation speed of the driven body increases. A method for controlling a piezoelectric motor, comprising: moving the piezoelectric motor in a direction opposite to the axis of rotation of the motor;

6. When decelerating the driven body, The first piezoelectric vibrator is moved away from the rotation shaft as the rotation speed of the driven body decreases.

6. The method for controlling a piezoelectric motor according to claim 5, further comprising the step of moving the piezoelectric motor in a direction opposite to the direction of the piezoelectric actuator.

7. When the first piezoelectric vibrator is moved in the direction while the driven body is stationary, The first piezoelectric vibrator is vibrated in a reciprocating manner in a direction approaching and moving away from the driven body. A method for controlling a piezoelectric motor according to claim 5 or 6.

8. an interconnected first member and a second member; 5. The method according to claim 1, wherein the second member is displaced relative to the first member. A robot comprising: a piezoelectric motor mounted on said actuator;

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