JPH0340773A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To drive a motor under optimum conditions by disposing a piezoelectric plate polarized circumferentially between a supporting plate at the center of a stator and a torsional vibration exciting piezoelectric ceramic element, and leading resonance state detecting electrodes from the main surface of the plate. CONSTITUTION:A disc-like or annular piezoelectric ceramic plate 13 polarized circumferentially for detecting a torsional vibration state is disposed between a supporting plate 15 and a torsional vibration exciting piezoelectric ceramic element 12. Resonance state detecting metal electrodes are formed on both side surfaces of the plate 13, and electric terminals 131, 132 are led therefrom. Accordingly, since whether the torsional vibration state is resonant or nonresonant can be detected, a motor can be driven in a state that its driving frequency is always resonance frequency of the torsional vibration. Thus, even if environments such as temperature, etc., is varied, it can be always continuously driven under optimum conditions.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention uses a piezoelectric vibrator as a stator, excites ultrasonic tank circular vibration in the stator, and rotates a rotor press-welded to the stator through frictional force. This relates to ultrasonic motors.

(Prior Art) As an example of an ultrasonic motor having a configuration in which a vertical-torsion composite piezoelectric vibrator is used as a stator and a rotor is pressed against the end face of the stator to generate rotational force, the one proposed by the present inventors is particularly proposed. It is disclosed in JP-A-63-149726. A side sectional view of the configuration of this ultrasonic motor is shown in FIG. The following description will be made with reference to the drawings.

A cylindrical or cylindrical piezoelectric ceramic element 11 for longitudinal vibration excitation polarized in the thickness direction and a piezoelectric ceramic element 12 for torsional vibration excitation polarized in the circumferential direction are mounted together with a support plate 15 in a cylindrical shape similar to both piezoelectric elements. Alternatively, a stator sandwiched between cylindrical elastic bodies 16 and 17 is used, and AC voltages having the same frequency and different phases are applied from an AC power source to the piezoelectric ceramic element 11 for longitudinal vibration excitation and the piezoelectric ceramic element 12 for torsional vibration excitation, respectively. This excites ultrasonic elliptical vibrations on the end face of the stator. At this time, if the driving frequency is made to match the resonant frequency of the torsional vibration of the stator, ultrasonic elliptic vibration with a very large vibration amplitude in the circumferential direction of the stator can be obtained. A rotor 21 is arranged on the end face of the stator, and the rotor 21 is pressed against the stator by installing a bearing 22, a spacer 23, a spring 24, and a nut 25 on a shaft 26 fixed to the stator. There is. In this way, by pressing the rotor against the stator that is in a state of ultrasonic elliptic vibration, a strong rotational force is generated in the rotor.

(Problems to be Solved by the Invention) The conventional ultrasonic motor shown in Fig. 3 has no choice but to be driven at a preset frequency, so temperature changes and load fluctuations may cause the ultrasonic motor's torsional vibration resonance frequency to change. When the frequency changes, there is a problem in that the drive frequency deviates from the resonance frequency of torsional vibration, resulting in a slow rotation speed.

(Means for Solving the Problems) The present invention provides an ultrasonic motor that excites ultrasonic elliptical vibration using a vertical-torsion compound vibrator as a stator, and generates rotational force by press-contacting a rotor to the stator. A piezoelectric ceramic plate polarized in the circumferential direction is placed between the support plate in the center and the piezoelectric ceramic for torsional vibration excitation without being connected to a drive power source, and a piezoelectric ceramic plate is arranged from the main surface of the piezoelectric ceramic plate for resonance state detection. This is an ultrasonic motor characterized by a structure in which electrodes are taken out.

(Function) FIG. 1 is a cross-sectional view showing a configuration example of a stator portion of an ultrasonic motor according to the present invention. This will be explained below with reference to the drawings.

The source of mechanical energy is a piezoelectric ceramic element 11 for longitudinal vibration excitation, which is cylindrical or cylindrical and polarized in the thickness direction, and a torsion polarized in the circumferential direction, as in the conventional ultrasonic motor shown in FIG. The stator has a structure in which a piezoelectric ceramic element 12 for vibration excitation is sandwiched between support plates 15. In the ultrasonic motor of the present invention, in addition to these two drive piezoelectric ceramic elements, a disk or annular piezoelectric ceramic plate 13 polarized in the circumferential direction is used to detect torsional vibration states in conjunction with a support plate 15. It is arranged between the excitation piezoelectric ceramic elements 12. Metal electrodes are formed on both sides of this piezoelectric ceramic plate 13, and electrical terminals 131 and 132 are taken out from there.

Further, a spacer 14 is arranged to maintain electrical insulation between the metal electrode and the stator. Piezoelectric ceramic element 1
1.12.13 and spacer 14 together with support plate 15,
A cylindrical or cylindrical elastic body 16.1 similar to a piezoelectric element
Let the thing sandwiched in step 7 be the stator.

111° and 112° from the piezoelectric ceramic element 11 for longitudinal vibration excitation and the piezoelectric ceramic element 12 for torsional vibration excitation, respectively.
．． Take out the electrical terminals 121 and 122 (Figure 2). An AC voltage V, = A, sin ωt is applied between the electronic terminals 111 and 112 from an AC power source for longitudinal vibration drive. on the other hand,
Between the electric terminals 121 and 122, an AC voltage vT=ATS with the same frequency and different phase is applied from an AC power source for torsional vibration drive.
Apply in(ωt+Φ). By applying an alternating current voltage to the two piezoelectric ceramic elements in this manner, ultrasonic elliptical vibration, which is a combination of longitudinal vibration and torsional vibration, is excited.

When the stator in Fig. 1 is in a state of torsional vibration, the displacement of torsional vibration is expressed as u = B sin (ωt + Φ + 0), and ■ If the driving frequency is lower than the resonance frequency, O'< e < 90°
,■If the driving frequency is equal to the resonant frequency, e=90',
■If the driving frequency is higher than the resonance frequency, 90'<
There is a relationship of e < isoo. Also, the vibration distortion is S=
−Csin(ωt+Φ+e). Here, the amount of strain C is a function of position, and this C is largest near the support plate 15, which is the position of the vibration node. Therefore,
If the piezoelectric ceramic plate 13 is placed adjacent to the support plate 15, a voltage V8=-A35in(ωt+Φ10e
) occurs. This voltage (8) O changes depending on the vibration state as shown above. Conversely, by measuring this 0, it is possible to know the deviation between the drive frequency and the resonance frequency.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 2 is a sectional view of an ultrasonic motor showing one embodiment of the present invention. In Figure 2, 11 is a cylindrical piezoelectric ceramic element for longitudinal vibration excitation, and 12
It is a stack of two sheets. The top and bottom surfaces of each ceramic plate are metallized, and the ceramic plates are stacked with thin metal plates for taking out the electrodes in between so that the directions of polarization alternate. The electrodes taken out from the thin metal plate are externally connected to an AC power source for longitudinal vibration driving through electric terminals 111112, and a voltage 1 is applied thereto.

On the other hand, reference numeral 12 denotes a cylindrical piezoelectric ceramic element for torsional vibration excitation, which is made by laminating eight ceramic pieces polarized in the circumferential direction and having an outer diameter of 20 mm, an inner diameter of 8 mm, and a thickness of 1 mm. The lamination method is the same as that of the piezoelectric ceramic element 11, and the piezoelectric ceramic element 11 is connected to an AC power supply for driving torsional vibration externally through electric terminals 121 and 122, and a voltage 7 is applied. 13 is a disk-shaped piezoelectric ceramic plate for detecting torsional vibration state, with an outer diameter of 20 mm;
It is a piezoelectric ceramic plate polarized in the circumferential direction with an inner diameter of 8 mm and a thickness of 0.5 mm, and the upper and lower main surfaces are metallized and electrical terminals 131 and 132 are connected. 14 is an alumina plate for insulation, outer diameter 20 mm N inner diameter 8 mm, thickness 0.5 mm
It is. In Fig. 2, alumina plates 14 are arranged on both main surfaces of the piezoelectric ceramic plate 13, but the driving power source and torsional vibration state detection voltage are connected to a common ground, and this time an insulator is used for the metal support plate 15. For example, the alumina plate 14 can be omitted. two driving piezoelectric ceramic elements 11, 12;
Piezoelectric ceramic plate 13 for torsional vibration detection, alumina plate 14
is sandwiched between cylindrical metal elastic bodies 16 and 17 to constitute a stator.

A shaft 26 is fixed to the upper part of the stator. Furthermore, a cylindrical rotor 21 is arranged so as to be in contact with the stator, and a bearing 22, a spacer 23, a coil spring 24
, a nut 25 presses the rotor 21 against the stator. The characteristics of the ultrasonic motor change depending on the pressure force of the rotor, and this pressure force can be adjusted to an optimum value by tightening the nut 25.

The resonance frequency of torsional vibration of this ultrasonic motor was 32.3 kHz as a result of impedance measurement. When this ultrasonic motor was driven at 27kHz, which is lower than the resonance frequency, the torsional vibration drive voltage ■7 and the torsional vibration state detection voltage ■8
The phase difference 0 was 18°. From here, as the drive frequency increases, the phase difference e also increases, reaching 90' at 32.1kHz near the resonance frequency, and 163' at 36kHz.
It became ゜.

(Effects of the Invention) As described above, according to the present invention, it is possible to detect whether the state of torsional vibration is resonant or non-resonant. Can drive a motor. Therefore, it has the advantage that it can always continue to be driven under optimal conditions even if the environment such as temperature changes, and has great industrial value.

[Brief explanation of drawings]

FIG. 1 is a structural sectional view showing an example of the stator section of the present invention,
FIG. 2 is a sectional view showing an embodiment of the ultrasonic motor of the present invention;
FIG. 3 is a side sectional view of a conventional ultrasonic motor. In the figure, 11... Piezoelectric ceramic element for longitudinal vibration drive, 12... Piezoelectric ceramic element for torsional vibration drive, 1
3... Piezoelectric ceramic plate for torsional vibration state detection, 14.
...Insulating plate, 15...Metal support plate, 16.17...
- Metal elastic body, 21... Rotor, 22... Bearing, 23... Spacer, 24... Coil spring, 25... Nut, 26... Shaft, 111, 112° 121, 122. 131.132...Electrical terminal.

Claims (2)

[Claims] (1) In an ultrasonic motor that includes a stator having a longitudinal-torsional composite vibrator in which a longitudinally vibrating piezoelectric element and a torsionally vibrating piezoelectric element are arranged via a support plate, and a rotor that is press-welded to the stator, the stator An ultrasonic motor characterized by a structure in which a piezoelectric ceramic plate polarized in the circumferential direction and having electrodes formed on both sides is arranged between a support plate in the center and a torsionally vibrating piezoelectric element. (2) The ultrasonic wave according to claim 1, wherein the piezoelectric ceramic plate polarized in the circumferential direction and having electrodes formed on both sides is disposed between the support plate and the torsionally vibrating piezoelectric element with an insulating plate interposed therebetween. motor.