JPS63209478A - Very fine response ultrasonic motor - Google Patents

Abstract

PURPOSE:To heighten the positioning accuracy, by constituting an ultrasonic motor with an echoless stator. CONSTITUTION:In an echoless responsive stepping motor, a stator of integral structure is constituted with a ceramic piezoelectric disc 30 sandwiched between aluminium discs 33 and 34 in inserting and fastening the tip of a stainless steel belt set in the central hole into a screwed hole in the center of bottom of a torsional connector 37. A rotor 36 is bolted to the upper surface of this stator through bearings and springs inside the shaft of rotor. With the rotor 36 compressedly uprighted, a motor is constituted. In order to prevent the rotor 36 from overshooting, negative phase pulse is applied as soon as the pulse gets extinct. Negative phase vibration will occur as a result and the reverberation will be set off, so that the amplitude gets smaller than the border line and the rotation of the rotor 36 will stop at the same time when the pulse vanishes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ultrasonic stepping motor, and more particularly to improving its step response.

[Conventional technology]

The present inventor has filed numerous patent applications for the results of his research on ultrasonic motors, and among them, the invention of ``Piezoelectric motor using cantilever-shaped torsion ultrasonic vibrator'' (Japanese Patent Application No. 59-172429) This is the basic technology of
For example, "Variable capacitor with ultrasonic motor" (Special 60-2
93631).

By the way, after further development as a stepping motor, we examined the pulse response in detail and found that the pulse was several 1.
When driven with 0 or more electric signals, the amount of displacement is faithfully proportional to the number of pulses, but when there are 10 or less, this relationship deviates, and in particular, the displacement for a single pulse is equivalent to 3 to 4 pulses. It was found that there was a slight overshoot. For example, drive frequency 43.2KHz, rated rotation speed 6Orp
The m motor rotates once at 43,200 pulses per second, so with 10,800 pulses it rotates 90", and with 120 pulses it rotates by 1", but with 12 pulses it rotates for 7 minutes instead of 6 minutes, and with a single pulse it rotates for 7 minutes. It should only rotate for 30 seconds - 0.5 minutes, but it overshoots by about 3 to 4 times and rotates for about 2 minutes.

In other words, there is linear response accuracy up to an angular displacement of 1/4,000 rotations, but there is no expected second-to-second accuracy, and the limit is minute summation, and the response to a single pulse overshoots the expected value by several times. However, it had the disadvantage of lacking high-definition responsiveness.

[Problem that the invention seeks to solve]

The present invention aims to solve the above-mentioned drawback of the conventional ultrasonic motor in that the displacement response to single pulse drive overshoots, and thereby to provide an ultrasonic stepping motor with excellent high-definition response. purpose.

[Means to solve the problem]

It is the fate of conventional ultrasonic motors to have an overshoot response to a single pulse. In an ultrasonic motor, the stator system including the rotor is composed of an ultrasonic resonance system, and a resonance phenomenon occurs when vibrations that match the natural frequency of the motor are applied. Even if the acting vibration is a single pulse, if it resonates, the vibration will continue, creating a reverberant state.

As shown in Figure 3, the amplitude of reverberation attenuates over time, but as long as the amplitude is greater than half of the amplitude a0 of the specified vibration that supports the rotor's rated rotation, the rotor will be displaced by the rotational torque. . In the conventional Φ motor, the amplitude attenuates relatively quickly, and the amplitude becomes a0/2 at the third to fifth reverberation pulses,
After that, there is little attenuation, and the reverberation continues for quite a long time.

Reverberation smaller than the amplitude a0/2 does not rotate the rotor, so to improve the motor's single-pulse response, pulse 1
Immediately after application, reverse phase pulse 2 is applied (Figure 1) to cancel out the reverberation and reduce the amplitude of the reverberation at least a, /
It is better to make it smaller than 2.

〔Example〕

An embodiment of the reverberation-free responsive stepping motor of the present invention is shown in FIG. The structural appearance of the motor used in the examples is a step type of the torsion connector type ultrasonic motor that the present inventor had already proposed and has improved over the years. That is, the outer diameter of 40 m and the inner diameter of 15 B are Pb (
Z, T= )03 series ceramic piezoelectric circle #j: 30.30
sandwiched between aluminum disks 33 and 34 with an outer diameter of 40 m and an inner diameter of 8 milled, thickness Iln and 12.5 mm, and the tip of a stainless steel bolt with a diameter of 8 fi and a length of 27.2 m set in the center hole was twisted into a connector. 37 and tightened to form an integrated stator. A diameter 6H
The motor was constructed by tightening the bolts and aligning the rotor with the optimum pressure No. of about 301 urf.

43.2KH to the lead wire 31.32 connected to the terminal board
When an AC voltage of 100V is applied to the piezoelectric element 30, thickness vibrations are generated in the piezoelectric element 30, which are resonantly amplified by the stator and at the same time converted into elliptical vibrations by the torsion coupler, producing strong ultrasonic waves on the upper surface of the stator. Elliptical vibration occurs, and its vertical vibration component gives buoyancy to the rotor, and its torsional component gives rotational torque, so the rotor rotates vigorously.

Here, even if the sine wave voltage of 43.2 Kk applied to the piezoelectric body is changed to a rectangular wave having the same period, the rotor still rotates vigorously. The rotation speed is 60 rpm, that is, 1 rotation per second. The applied pulses are 432,000 pulses per second, and each pulse rotates for 11/43.200 of 360", or 30 seconds. By the way, the drive pulses are reduced at the same time as the power is turned off. , the rotor rotates a little more and then stops.This extra amount of overshoot is even after applying a large number of pulses 12 as shown by the dotted line in Figure 3.
There is no difference even after the application of a single pulse 11, which is about 3 to 5 pulses. In order to find out the cause of this overshoot, a piezoelectric element 37 was attached as a vibration sensor to the torsion coupler, and changes after the pulse disappeared were measured, and the following was found.

During pulse application, a sine wave vibration 10 occurs even if the pulse is a rectangular wave 12. The same is true for the sinusoidal vibration 13 for a single pulse 1. However, even after the pulse disappears, the oscillation continues indefinitely while gradually attenuating.
It is large at ~5 pulses, and in Figure 3, at the 4th pulse 17, it becomes half the original amplitude of the vibration 13, and the rotor moves up to this point, but after the 5th pulse 18, it reaches the border line 19 with half the amplitude. The rotor will not be able to move because the lower layer will collapse. When the rotor does not move, less energy is consumed and the vibrations are less attenuated, and although the vibrations of the same amplitude move endlessly, the rotor is not affected. The rotor overshoots at about 3 to 5 pulses of vibration with an amplitude larger than the borderline 19. To prevent overshoot, apply reverse phase pulses 2, 4, and 5 immediately after the pulse disappears. Reverse phase vibration occurs, the reverberation is canceled out, and the amplitude becomes smaller than the borderline, and the rotor rotates at the same time as the pulse disappears. Stop.

FIG. 4 shows another embodiment, in which the amplitude of the reverse phase pulse applied immediately after the application of the drive pulse is not made the same as the drive pulse as in the previous embodiment, but the reverse phase pulse with a small amplitude is applied. Multiple voltages were applied.

That is, immediately after the end of the drive pulse 21, pulses 22, 23, and 24 whose amplitude is 50 to 60% of the drive pulse and whose phase is opposite to that of the drive pulse are generated.
When the ultrasonic vibration of the stator was applied, the reverberation became significantly small and became almost negligible as shown in 26. When the reverberation falls below the Borg line 29, no rotational force can be applied to the rotor and the motor will stop rotating. However, even if the amplitude is small, if long-lasting vibrations continue to act on the rotor, the crimping surface will wear out. This could be the cause. However, in this embodiment, when three reverse-phase pulses are applied, the rotor stops at the first pulse, and the reverberation also occurs at the second pulse of the third pulse.
4, the wear became negligible and there was no need to worry about wear.

The motor used in the above-mentioned embodiment has a rated frequency of 43.
2KH1 rated voltage is 100V and no-load rotation speed is 60 rpm. This motor has a width of 11.57 μs and a duty of 50%.
When a square wave voltage of 43.200 pulses was applied, it rotated exactly 360 degrees, and with 10.800 pulses it rotated 90'',
1" for 120 pulses, 6' for 12 pulses, 3 for 1 pulse
It was verified that the pulse number rotated by 0" and a perfect linear relationship between the number of pulses and the rotation angle was established.

〔Effect of the invention〕

As explained above, since the ultrasonic motor of the present invention is configured with a non-reverberant stator, the rotational displacement of the rotor in response to a single pulse is equal to the rotational displacement of one period in a continuous wave, and therefore the rotation of the gold dust We were able to realize an ultrasonic motor with displacement resolution, which not only allows for high positioning accuracy as a motor used in high-definition positioning devices, but also allows us to obtain a linear relationship between the number of pulses and displacement. , the fact that positioning control has become extremely easy is a significant practical effect.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one embodiment of the driving waveform of a high-definition response ultrasonic motor and the corresponding vibration state of the stator according to the present invention, and FIG. 2 is an explanatory diagram showing another embodiment.
Fig. 3 is an explanatory diagram showing the reverberation of a conventional stator, Fig. 4 is an explanatory diagram showing the third embodiment of the present invention, and Fig. 5 is a front view of a high-definition response ultrasonic motor used in the present invention. It is a diagram. 1... Single drive pulse, 2... = Reverberation pulse, 1'2'... Stator vibration for 1 and 2, 3... Continuous Mv<Rus, 4.5...
...m left! ' pulse, 6°7...3,
4. Stator vibration for 5, 11... Drive single pulse, 12. Old... Drive continuous pulse, 10.13
~18...11. Stator vibration for 12, 19.29... amplitude border line, 21.
...Drive single pulse, 22, 23.24...
...Dereverberation pulse, 25.26.26', 26'. 27... Stator vibration for 21, 22, 23.24, 30... Piezoelectric element, 31.32
・Old... Lead wire, 33. 34... Aluminum disc, 35... Torsion connector, 36. Old...
Rotor, 37... Vibration sensor. Figure 1 Figure 2 Figure 3 Figure 4

Claims (3)

[Claims] (1) By using a non-reverberant stator, the rotor will not overshoot after the drive voltage is finished.
Ultrasonic motor with high-definition response, characterized by immediate stopping. (2) The reverberation-free stator according to claim (1), characterized in that the vibration state of the stator after the drive voltage ends is free of vibrations with an amplitude larger than the minimum amplitude necessary to drive the rotor. Ultrasonic motor with high-definition response. (3) The reverberation-free stator described in claim (1) refers to an electric signal such as a sine wave, a rectangular wave, a trapezoidal wave, a triangular wave, etc. in which a single pulse or a plurality of pulses are periodically connected to drive the rotor. Alternatively, after the application of an electrical signal consisting of a continuous wave with a similar waveform is completed, at least one electrical signal of the same waveform and opposite phase is applied subsequently, thereby canceling out the reverberation caused by the driving electrical signal and creating a reverberation-free state. Ultrasonic motor with high-definition response characterized by: