JP2915139B2 - Bolted Langevin type ultrasonic motor - Google Patents

Description

The present invention relates to a bolted Langevin type ultrasonic motor, and more particularly to a bolted Langevin type ultrasonic motor which applies a motor drive voltage to a piezoelectric element of a stator portion and rotationally drives a rotor portion. Related to motor improvement.

[Prior art] Conventionally, bolt-fastened Langevin type ultrasonic motors have low operating noise, low inertia, and can be instantaneously stopped / started. Simple motor structure Large traveling torque ultrasonic motor compared to electromagnetic motors Higher speed operation possible Single-phase drive possible (Two-phase drive for traveling wave type ultrasonic motor)
Because of these advantages, it can be expected to improve the performance of the product by applying it to existing products using motors, and its practical application is desired.

FIG. 6 shows an example of an ultrasonic motor using such a bolted Langevin type vibrator.

The stator portion 11 of the bolt-fastened Langevin type ultrasonic motor 10 is formed in a cylindrical shape, and a bolt 12 is provided at the center thereof. Blocks 14 and 16 are screwed to the bolt 12 at the upper and lower positions. Each of the blocks 14 and 16 is formed in a cylindrical shape, and is threaded at its center so as to be screwed to the bolt 12.

And, between the blocks 14 and 16, two piezoelectric elements
18a and 18b are arranged. That is, the two piezoelectric elements 18a and 18b are sandwiched between the blocks 14 and 16.

Electrodes 20 are attached to the upper and lower surfaces of one of the piezoelectric elements 18b, and an AC power supply (not shown) is connected to the electrodes 20, so that a motor driving voltage of a predetermined frequency is applied. .

In this manner, when a motor drive voltage of a predetermined frequency is applied to the electrode 20, a vertical vibration is generated in the piezoelectric element 18 in the vertical thickness direction (the direction of the arrow 100). At this time, the longitudinal vibration is transmitted to the blocks 14 and 16, but since the blocks 14 and 16 are screwed to the bolts 12, the screws generate torsional vibration. In this way, a combined vibration of the longitudinal vibration and the torsional vibration is generated on the end surfaces of the block bodies 14 and 16. Therefore, by attaching a rotor (not shown) to the upper end of the block body 14, the rotor is rotationally driven by the combined vibration generated on the end face of the block body 14, whereby a rotational driving force can be obtained.

Various improved techniques of such a bolted Langevin type ultrasonic motor are disclosed in JP-A-63-217984 and JP-A-7-76193.

[Problems to be Solved by the Invention] As described above, the bolted Langevin type ultrasonic motor generates a rotational force by applying a single-phase AC voltage to the piezoelectric element 18 as a motor drive voltage. The generated rotational force changes greatly depending on the frequency of the motor drive voltage, and the rotational force generation efficiency becomes maximum at a specific frequency (hereinafter, referred to as an optimum drive frequency).

The optimum driving frequency is a value unique to each motor, and the bandwidth of this frequency is very narrow.

Further, the value of the optimum driving frequency is not always constant during operation, but changes at any time depending on operating conditions such as a temperature change of an element and a size of a load. Therefore, in order to drive the ultrasonic motor with high efficiency, it is necessary to detect the constantly changing optimal driving frequency and perform feedback control of the frequency of the motor driving voltage.

However, in the related art, the changing optimal driving frequency cannot be electrically detected for the feedback control. Therefore, the frequency of the motor driving voltage is always set to a constant value, or it is considered that the frequency is the optimal driving frequency. The motor must be driven with the frequency set near the frequency, and the feedback control of the frequency of the motor drive voltage cannot follow the changing optimal drive frequency.

Therefore, the conventional bolt-fastened Langevin type ultrasonic motor has a problem that the generation efficiency of the rotational driving force of the ultrasonic motor is low, and sufficient performance cannot be exhibited.

The present invention has been made in view of such a conventional problem, and has as its object to perform feedback control so that the frequency of a motor drive voltage always follows an optimum drive frequency that changes according to operating conditions, so that the optimum An object of the present invention is to provide a bolted Langevin type ultrasonic motor that can be driven in a state.

Means for Solving the Problems To achieve the above object, the present invention applies a motor drive voltage of a predetermined frequency to a piezoelectric element of a stator unit, and rotates a rotor unit by the obtained longitudinal vibration and torsional vibration. In a bolt-fastened Langevin type ultrasonic motor, a longitudinal vibration sensor for extracting longitudinal vibration of the stator portion as an electric signal; a torsional vibration sensor for extracting torsional vibration of the stator portion as an electric signal; Phase comparing means for outputting a phase difference between a signal and an electric signal taken out of the torsional vibration sensor as a phase angle φ, and a phase angle at which the phase angle φ output from the phase comparing means can obtain a preset maximum efficiency. Frequency adjustment means for adjusting the frequency of the motor drive voltage applied to the piezoelectric element so as to be 90 °.

[Operation] The present inventors have conducted various experiments from the viewpoint that if the frequency of the motor drive voltage deviates from the optimum drive frequency, this can be indirectly detected.

As a result of this experiment, no matter how the optimum drive frequency changes, as long as the frequency of the motor drive voltage is controlled to the optimum drive frequency, the phase difference between the longitudinal vibration and the torsional vibration generated in the stator, that is, the phase It has been found that the angle φ always has the value 90 °.

FIGS. 5A and 5B are explanatory diagrams for that purpose.

FIG. 5A is an explanatory diagram showing the phases of the motor drive voltage signal V _{1 of} a predetermined frequency applied to the piezoelectric element, the generated longitudinal vibration signal V _3, and the torsional vibration signal V ₂ . Here, the phase difference between the longitudinal vibration signal V ₃ and torsional vibration signal V ₂ is a phase angle φ of a portion in a broken line in FIG.

Further, FIG. 5 (B) is the frequency f of the driving voltage at constant conditions, the longitudinal vibration signal with respect to the drive voltage signal V ₁
Is a graph showing the relationship between V ₃ and respective phase angles phi ₁ and phi ₂ of the torsional vibration signal V _2. As understood from this graph, the longitudinal vibration signal V ₃ at the optimal driving frequency f _M
The phase angle phi _M between the vibration signal V ₂ torsion that there 90 °. In other words, the difference between the phi ₁ and phi ₂ becomes 90 °.

According to the experiments conducted by the present inventors, if the operating conditions are variously changed, but also changes in the various curves of the diagram showing the relationship between the frequency f and the phase angle phi, phase angle with respect to the optimum drive frequency f _M It was confirmed that φ of 90 ° did not change under any conditions.

The present invention has been made based on such a fact.

In the present invention, first, a phase angle φ _M which is a phase difference between the electric signal V ₃ based on the longitudinal vibration obtained by the longitudinal vibration sensor and the electric signal V ₂ based on the torsional vibration obtained by the torsional vibration sensor is calculated. Detected by phase comparison means. Then, the frequency adjustment means, for feedback control of the frequency of the motor drive voltage so that the phase comparison means the phase angle phi _M obtained from becomes 90 ° is a phase angle obtained with maximum efficiency.

Thus, according to the present invention, the frequency of the motor drive voltage is always controlled to the optimum drive frequency.

Thus, according to the present invention, by adjusting the frequency of the motor drive voltage phase angle phi _M always to be 90 °, it is always possible to drive the bolted Langevin type ultrasonic motor at peak efficiency it can.

Next, a preferred embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a bolted Langevin type ultrasonic motor to which the present invention is applied. The same members as those of the bolted Langevin type ultrasonic motor shown in FIG. 6 are denoted by the same reference numerals, and description thereof will be omitted.

The bolted Langevin type ultrasonic motor 10 of the embodiment
Has a stator portion 11 and a rotor (not shown). The stator portion 11 includes piezoelectric elements 18a and 18b,
And bolts (not shown).

The piezoelectric element 18a, 18b is held between the block body 14, a predetermined motor drive voltages V ₁ through the electrode 20 from the terminal T ₃ and T ₄ are configured to be applied.

Therefore, the application of a motor driving voltage V ₁ of the predetermined frequency to the terminals T ₃ and T _4, the longitudinal vibration is generated piezoelectric element 18a, by 18b, the longitudinal vibration will be transmitted to the block body 14, 16 . Then, the bolts screwed inside the block bodies 14 and 16 generate torsional vibration by the bolts, and the combined vibration of the torsional vibration and the longitudinal vibration is transmitted to the end face of the stator. (Not shown) that is in contact with the rotor is driven to rotate.

One of the features of the bolted Langevin type ultrasonic motor 10 of the present invention is that a longitudinal vibration sensor 28 for detecting a longitudinal vibration signal generated in the stator portion 11 as an electric signal,
And a torsional vibration sensor 30 for detecting a torsional vibration signal generated as a signal as an electric signal. In the present embodiment, each of the vibration sensors 28 and 30 is formed as a piezoelectric vibration sensor including a piezoelectric element and an electrode.

Further, as is well known, the torsional vibration generated in the stator portion 11 includes an abdomen showing a vibration peak and a node having a vibration value of zero, and the positions of the abdomen and the node are determined by the stator portion. Once the shape of 11 is determined, it will always be constant.

For this reason, it is preferable that the torsional vibration sensor 30 is attached to the stator portion 11 so as to be located on the antinode of the generated torsional vibration. In the present embodiment, the predetermined side surface of the block body 16 is designed to satisfy such conditions. Fixed in position.

Thus, the torsional vibration generated in the stator 11, the piezoelectric torsional vibration sensor 30 well detected by this is as torsional vibration signal V _2, the output from the terminal T ₁ and T ₂ is pulled out from the sensor electrode become.

Further, the longitudinal vibration sensor 28 is preferably attached to the stator portion 11 so as to be able to detect longitudinal vibration without being affected by torsional vibration. In the present embodiment, the block body 16 is provided so as to satisfy such properties. Mounted and fixed on the bottom.

When the vertical vibration sensor 28 is mounted on the side surface of the stator 11, it is preferable to provide the vertical vibration sensor 28 at a node where the torsional vibration value is zero.

As a result, the longitudinal vibration generated in the stator unit 11 is properly detected by the longitudinal vibration sensor 28, and the longitudinal vibration signal V ₃
As it will be output from the terminal T ₅ and T ₆ was withdrawn from the sensor electrode.

FIG. 2 shows a drive circuit of the ultrasonic motor according to the embodiment.

The ultrasonic motor 10 of the present embodiment has a VCO 32 called a voltage-controlled oscillator, and an AC voltage of a predetermined frequency output from the VCO 32 is amplified by a power amplifier 34 to a motor drive voltage, and the terminals T ₃ and T _{3 It} is applied to the piezoelectric element 18 via ₄ and drives the ultrasonic motor 10.

In addition, the drive circuit of the embodiment has an output V _{3 of the} longitudinal vibration sensor 28.
A longitudinal vibration sensor signal input circuit 36 but to be input, and a torsional vibration sensor signal input circuit 38 to the output V ₂ of the torsional vibration sensor 30 is inputted, each of these input circuits 36 and 38, the input signal V
_3, converts V ₂ to the appropriate voltage level, respectively, the corresponding phase shift circuit 40a, and outputs toward 40b.

Each of these phase shift circuits 40a and 40b converts only the phase of the input signal and outputs the converted signal.
If the V ₃ and V ₂ are in phase, the output of the phase shifting circuit 40b is performing the phase adjustment so that delayed 90 ° with respect to the output of the phase shift circuit 40a.

The outputs of the phase shift circuits 40a and 40b are input to waveform shaping circuits 42a and 42b, where the input sine wave signal is converted into a square wave signal having the same phase as that of the sine wave signal, and a phase comparator 44
Is input to

The phase comparator 44 is formed so as to detect the phase difference between the two input signals thus input, and to output a positive / negative pulse signal proportional to the phase difference to the loop filter 46.

As described above, in the present embodiment, the input circuits 36 and 38, the phase shift circuits 40a and 40b, the waveform shaping circuits 42a and 42b, and the phase comparator 44 constitute a phase comparing unit as a whole. .

The loop filter 46 is formed so as to remove high-frequency components and noise from the input signal in this way and output a DC voltage obtained by integrating the input pulse signal,
The output voltage is input to the VCO 32. That is, the VCO 32 outputs an AC voltage having a frequency corresponding to the output voltage output from the loop filter 46 to the power amplifier 34. Thus, in the present embodiment, the loop filter 46 and the VCO 32 constitute frequency adjusting means.

The embodiment has the above configuration, and its operation will be described below.

First, when the power supply (not shown) of the circuit is turned on, the VCO32
Outputs an AC voltage having an initial frequency fi. Then, the AC voltage is amplified output as the motor drive voltages V ₁ required to drive the ultrasonic motor 10 by the power amplifier 34, is applied to the terminal T ₃ and T ₄ for driving the ultrasonic motor. The application of this voltage, the longitudinal vibration and torsional vibration is generated in the block body 14, the longitudinal vibration sensor 28 generates a longitudinal vibration signal V ₃ corresponding to the longitudinal vibration, the torsional vibration sensor 30, generating a torsional vibration signal V ₂ corresponding to the torsional vibration.

At this time, the longitudinal vibration signal output from the longitudinal vibration sensor 28
V ₃ is supplied to the vertical vibration sensor signal input circuit 36, it is output dropped to a voltage level suitable for control. On the other hand, the torsional vibration signal V ₂ is supplied to the torsional vibration sensor signal input circuit 38,
Similarly, the voltage is reduced to a voltage level suitable for control and output.

Next, the respective signals in the phase shift circuits 40a and 40b are:
A phase change adjustment is performed. That is, when the input signals V ₃ and V ₂ are in phase in the phase shift circuits 40a and 40b,
The phase adjustment is performed so that the output of “b” always lags the output of the phase shift circuit 40a by 90 ° even if the frequency changes. Thus, if the feedback control so that the output signal of the phase shifting circuit 40a and the phase shift circuit 40b is in phase, and V _3, the phase difference between V ₂ may be 90 °.

Next, the outputs of the phase shift circuits 40a and 40b are supplied to waveform shaping circuits 42a and 42b, respectively, and shaped into square wave signals.

FIG. 3 shows a waveform diagram when the frequency of the drive voltage is feedback-controlled to the optimum drive frequency.

FIGS. 7A and 7B show the waveform shaping circuits 42a and 42a.
2b shows an output signal. In the figure, portions of the Z ₁ represents a phase delay of the output signal of the waveform shaping circuit 42a to the output of the waveform shaping circuit 42b. In this state, the current frequency of the motor drive voltage is not the optimum drive frequency, and the phase angle φ is a value larger than 90 °.
In this case, the phase comparator 44, and outputs relative to the high impedance as shown in FIG. (C), as a pulse width corresponding negative pulse signal Z ₁ is the phase difference.
Also since the output signal of similarly waveform shaping circuit 42b also Z ₂ in FIG. (B) there is a phase lag, and outputs a negative pulse signal having a width corresponding to the delay.

Then, in the portion of the Z ₃ in FIG (B), in a state of phase match of the output signal of the waveform shaping circuit 42a and 42b. If the phases of the output signals of the waveform shaping circuits 42a and 42b match, as described above, the phase shift circuit 40a
And the phase difference between the input signal V _3, V ₂ and 40b is made 90 °. Therefore, the frequency of the motor drive voltage in the state of Z ₃ is
The optimum driving frequency is obtained. At this time, the output of the phase comparator 44 maintains the high impedance state, and no pulse signal is output.

Next, the keep part of Z ₄ and Z ₅ in FIG (B), a phase delay occurs in the output signal of the waveform shaping circuit 42a side. In this case, the phase comparator 44 outputs a positive-side pulse signal having a width corresponding to the delay width.

The loop filter 46 receives a positive or negative pulse signal or a high impedance maintaining signal from the phase comparator 44 as described above, and outputs a predetermined analog voltage signal. FIG. 4D shows the output signal of the loop filter 46. When the input signal of the loop filter 46 is Z ₁ , Z ₂
In the case of a negative pulse as in the state of (1), the output DC voltage decreases. When the output of the phase comparator 44 has a high impedance, the output DC voltage is in a state where the state is maintained. When the input signal is a positive pulse, such as in the case of the Z ₄ and Z _5, the DC voltage at the output rises.

That is, when the phase angle φ is large phase angle than 90 degrees, it is necessary to increase the frequency of the motor drive voltage, the phase angle φ as in the Z ₄ and Z ₅ in the reverse is less than 90 degree phase In the case of a corner, it is necessary to lower the frequency of the motor drive voltage (see the graph of FIG. 5B). Therefore, the VCO 32 changes and adjusts its output frequency according to the input voltage.In the present embodiment, the frequency increases when the voltage of the loop filter 46 decreases, and conversely, when the output voltage of the loop filter 46 increases. Adjust to lower the output frequency.

FIG. 4 (A), (B) and (C), such frequency control of the motor driving voltage is performed, the phase angle of the longitudinal vibration sensor signal V ₃ and the torsional vibration sensor signal V ₂ phi 90 The graph shows the output waveforms of various parts of the circuit when the motor operates at the voltage of the optimal driving frequency, which is maintained at ゜.

In FIG. (A) has a motor drive voltage signal V ₁ which is actually applied, the motor drive voltage longitudinal vibration signal V ₃ generated based on the torsional vibration signal V ₂ is shown. Current driving voltage, since it the best drive frequency, the phase difference φ of V ₃ and V _2, is adjusted to 90 °.

FIG. 7B shows a vertical vibration sensor signal input circuit at this time.
36 shows signal waveforms output from the torsional vibration sensor signal input circuit 38, and shows that each signal waveform is a waveform adjusted to a voltage level suitable for control.
The phase angle φ is 90 °.

FIG. 3C shows signal waveforms output from the waveform shaping circuits 42a and 42b at this time. Here, the waveforms of both outputs are completely in phase. In other words, the phase of the output signals of the waveform shaping circuits 42a and 42b are completely in phase, so that the phase difference between the input signals V ₃ and V ₂ of the phase shift circuits 40a and 40b is controlled to be 90 °. .

Thus, in this embodiment, feedback control of the frequency of the motor drive voltage, the phase difference between the signals V ₃ and V ₂ is
It is possible to control the frequency of the motor drive voltages V ₁ to maintain a 90 °. By controlling in this way, the frequency of the motor drive voltage can be adjusted so as to always follow the optimal drive frequency that varies depending on the size of the load and the temperature of the motor, so that an efficient bolted Langevin type ultrasonic motor can be used. Can be driven.

Note that the present invention is not limited to the above embodiment,
Various modifications can be made within the scope of the present invention.

For example, in the above-described embodiment, the case where the drive circuit of the ultrasonic motor 10 is configured by an analog circuit has been described as an example.
The present invention is not limited to this, and may be configured by a digital circuit as needed, or may be configured to be performed by computer control such as a CPU.

Further, in the above embodiment, using the phase shift circuits 40a and 40b,
Was configured to provide a 90 ° phase difference to the two signals V ₃ and V _2, the present invention is not limited thereto, the phase shift circuit 40a as necessary, without using a 40b, phase comparator 44 There compares the phase of the direct both signals V ₃ and V _2, it is also possible that the phase angle is configured to control such that 90 °.

[Effects of the Invention] As described above, according to the bolt-fastened Langevin type ultrasonic motor according to the present invention, the frequency of the motor drive voltage is feedback-controlled so as to always follow the optimal drive frequency that changes variously based on the operating conditions. be able to.
Thus, the driving of the ultrasonic motor can always be performed in a good state, and the performance of the ultrasonic motor can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view of a bolted Langevin type ultrasonic motor according to the present invention, FIG. 2 is a circuit configuration diagram of an entire driving device of the embodiment, and FIGS. 3 (A) to 3 (D) are operations of the embodiment. 4 (A), 4 (B) and 4 (C) are output waveform diagrams of the respective units during operation at the optimum driving frequency adjusted according to the embodiment, FIG. 5 ( 6A and 6B are explanatory views for explaining the basic principle of the present invention, and FIG. 6 is an explanatory view showing an example of a conventional bolted Langevin type ultrasonic motor. 10 …… Bolted Langevin type ultrasonic motor, 12 ……
Bolts, 14 and 16 Block body 18 Piezoelectric element
20 ... electrode, 22 ... rotor, 30 ... piezoelectric torsional vibration sensor, 32 ... VCO, 34 ... power amplifier, 36 ... drive voltage signal input circuit, 38 ... torsional vibration sensor signal input circuit, 40a,
40b: a phase shift circuit, 42a, 42b: a waveform shaping circuit, 44: a phase comparator, 46: a loop filter.

Continued on the front page (72) Inventor Keisuke Honda 20th Oyamazuka, Oiwa-cho, Toyohashi-shi, Aichi Prefecture Inside Honda Electronics Co., Ltd. Inside of Electronics Co., Ltd. (72) Inventor Yukinobu Tomita 20th Oyamazuka, Oiwa-cho, Toyohashi-city, Aichi Prefecture Inside of Honda Electronics Co., Ltd. In-house (56) References JP-A-63-234881 (JP, A) JP-A-2-228275 (JP, A) JP-A-3-40773 (JP, A) JP-A-3-40774 (JP, A) ) Patent 2604731 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) H02N 2/00

Claims (1)

(57) [Claims] 1. A bolt-fastened Langevin type ultrasonic motor in which a motor drive voltage of a predetermined frequency is applied to a piezoelectric element of a stator part and a rotor part is rotated by the obtained longitudinal vibration and torsional vibration. A longitudinal vibration sensor that extracts vibration as an electric signal; a torsional vibration sensor that extracts torsional vibration of the stator portion as an electric signal; a phase difference between an electric signal extracted by the longitudinal vibration sensor and an electric signal extracted by the torsional vibration sensor As a phase angle φ, and a motor drive applied to the piezoelectric element so that the phase angle φ output from the phase comparison means becomes a phase angle 90 ° at which a preset maximum efficiency is obtained. A frequency adjusting means for adjusting the frequency of the voltage, comprising: a bolted Langevin type ultrasonic motor;