JPH01238471A - Input controller for ultrasonic motor - Google Patents

Abstract

PURPOSE:To stabilize an output torque by forming the pole width of a piezoelectric element and the width of a feedback electrode in two types. CONSTITUTION:The elastic member 1 of an ultrasonic motor is formed in a circular shape in its outer periphery, an annular ground electrode 2 is mounted on one end face of its axial direction, an annular piezoelectric element 3 is provided on the outer face of the electrode, and a voltage applying electrode 4 is disposed on the outer face of the element. The element 3 is partitioned into two sets of semi-circular-arc shaped parts, and gaps of 0.5 and 1.5 times as large as its width are formed at opposite boundaries of the ends of both partitions. The electrode 4 is divided corresponding to the two partitions of the element 3, and so connected directly or through a phase shifter 6 to a high frequency power source 5 as to apply cos and sin voltages having 90 deg. out of phase. A vibration is generated at the element 3 by the applied voltage to rotate a rotor 7. In this case, a voltage generated from a feedback electrode 8 is output, and the voltage and frequency of the power source 5 are controlled by an input controller 9.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to an ultrasonic motor in which a piezoelectric body generates traveling waves in an elastic body to rotate a rotor. The present invention relates to an input control device that controls frequency.

``Prior art'' As shown in Fig. 4, a conventional ultrasonic motor has a piezoelectric body attached to a polar body, and the piezoelectric body is divided into two groups, and a positive pole and a negative pole are connected at a pitch of 172 wavelengths. It is polarized at the intersection of 1 and 1. Further, the two sets of piezoelectric sections are arranged with a 1/4 wavelength shift, and high frequency voltages having phases different by 90 degrees are applied to the two sets of piezoelectric sections, respectively, to generate traveling waves in the elastic body. The traveling wave rotates or linearly moves a moving element (including one that moves linearly and one that moves rotationally like a rotor) that is in pressure contact with the elastic body.

The high frequency voltage applied to each piezoelectric section is made to resonate by making its frequency equal to the natural frequency of the elastic body, but the temperature of the ultrasonic motor itself.

The resonant frequency tends to shift due to the state in which the mover is pressed against the elastic body, the friction of the mover, etc. For this reason, a feedback electrode is provided at the boundary between the two sets of piezoelectric parts, and the vibration from the adjacent piezoelectric part causes a voltage change in the piezoelectric part of the feedback electrode part. Then, the input control circuit receives the voltage change via the feedback electrode,
The input control circuit controls the high-frequency voltage source to improve the drive efficiency of the ultrasonic motor.

"Problem to be Solved by the Invention" Conventionally, in order to control the high frequency voltage applied to the piezoelectric material, a feedback electrode is provided at the boundary between two sets of piezoelectric material parts. Due to the influence of the body parts, the piezoelectric body of the feedback electrode part was sometimes subjected to different vibrations. Furthermore, with the conventional polarization pattern of piezoelectric bodies, it is difficult to stabilize the traveling waves generated in the elastic body.

For this reason, it is not possible to accurately detect whether or not the piezoelectric material in the feedback electrode section is generating a predetermined traveling wave in the elastic material, and the input control to the piezoelectric material may become insufficient or the traveling wave may become unstable. As a result, there are problems such as variations in the rotational speed or output torque of the ultrasonic motor.

Therefore, an object of the present invention is to stabilize the rotational speed or output torque by improving the polarization pattern of a piezoelectric material attached to the stator of an ultrasonic motor.

"Means for Solving the Problems" The present invention provides a method for attaching an annular piezoelectric body to the surface of an elastic body having a circular outer periphery, dividing the piezoelectric body into two parts, each having a diameter of 8"
High frequency voltages with different phases are applied via piezoelectric electrodes,
The rotor is pressed against the elastic body that generates traveling waves in the elastic body, and the rotor rotates in response to the traveling waves.Feedback is provided at the boundaries of each piezoelectric body section divided into 0 sections. A voltage generated therein is inputted to an input control circuit, and the high frequency voltage and frequency applied to the piezoelectric body are controlled by the input control circuit. Then, both sections of the piezoelectric body are polarized by making them alternately successive to + and - poles, respectively.

A gap of approximately the same width as the feed electrode was provided between the feedback electrode and the polarized portions of the piezoelectric material located on both sides.

In addition, in order to stabilize the rotational speed or output torque of the ultrasonic motor, in addition to the above, both sections of the piezoelectric body are polarized alternately and continuously to + and - poles, respectively, and the width of the feedback electrode is The length of the applied voltage is 1/4 wavelength, and the width of each polarized part in both sections of the piezoelectric body is 3/8 wavelength long, and the width of each remaining polarized part is 1/2 wavelength long. was formed.

"Operation" In the above-mentioned means, in which the piezoelectric bodies in two sections are alternately and continuously polarized to positive and negative poles, and the feedback electrode is provided with a spacing of approximately the same distance as itself, the piezoelectric body The feedback electrode is less likely to be induced by the high-frequency voltage applied to the polarized portion of the piezoelectric body. Therefore, the input control circuit can accurately control the high-frequency voltage applied to the piezoelectric body, improving the driving efficiency of the ultrasonic motor.

Also, in the second method, in which the width of each polarization of the piezoelectric body in the two sections and the width of the feed bank electrode were formed to a predetermined width, the driving efficiency of the ultrasonic motor could also be improved. This is because the high frequency voltage is applied to a wider range of the piezoelectric body, and there are fewer non-driven parts of the piezoelectric body.

"Example" A first embodiment of the present invention will be described with reference to FIG. 1.2.

The Y-type body 1 has a circular outer circumference, an annular earth electrode 2 is attached to one end surface in the axial direction, an annular piezoelectric body 3 is provided on the outer surface of the earth electrode 2, and an application electrode is further provided on the outer surface. 4 is placed. Note that if the elastic body 1 is directly grounded, the ground electrode 2 becomes unnecessary.

The piezoelectric body 3 is divided into two sets of t-arc-shaped parts, and at the opposing boundaries of the ends of both sections, rjJ of 1/2 of the 1 polarized part of the piezoelectric body and 1.5 times the width, which will be described later, are formed. Intervals are provided. Each section of the piezoelectric body is then polarized in succession, alternating between a seed and a single pole. Note that the unit width of each polarization of the piezoelectric material is
The angle with respect to the center of the piezoelectric body is set to be, for example, 25.71'', which is the length of 172 wavelengths of the applied high-frequency voltage.The application electrode 4 is divided corresponding to two sections of the piezoelectric body 3. 90 to each application electrode portion 4.
``The applying electrode 4 of each part is directly connected to the high frequency power source 5, and the other is connected via the phase shifter 6 so that the CO3 voltage and the sine voltage having different phases are applied.

When a voltage is applied to the voltage application electrode 4, vibration occurs in the piezoelectric body 3, which generates a traveling wave in the elastic body 1, and furthermore, the rotor 7, which is in pressure contact with the elastic body 1, receives the traveling wave and rotates. There is. Note that the diameter of the piezoelectric body 3 is 45 mm,
The diameters of the rotor 7 and the elastic body 1 also correspond to the piezoelectric body 3. One polarization of the piezoelectric body (applied voltage 1/
A feedback electrode 8 having a width of 1/2 (the length of two wavelengths) is arranged so that the generated voltage can be taken out from the piezoelectric body 3 at that portion. It should be noted that an interval of approximately the same width as the feedback electrode 8 is provided between the feedback electrode 8 and the polarized portions of the piezoelectric bodies on both sides thereof. The feedback electrode 8 is connected to an input control circuit 9.
The voltage and frequency of the high frequency voltage source 5 are controlled according to the voltage generated in the piezoelectric body 3 at the feedback electrode 8 portion. Although the piezoelectric portion at the position of the feedback electrode 8 is used as a negative pole, it may also be used as a negative pole.

Next, a second embodiment will be explained with reference to FIG.

In this embodiment, as in the previous embodiment, the piezoelectric body 3 is divided into two parts, and corresponding application electrodes 4 are provided, and a feedback electrode 8 is arranged on one side between the opposing ends of the two parts. There is a very small gap between the other ends to prevent electrical conduction between the electrodes on both sides. Each of the two sections of piezoelectric body 3 is polarized into five polarities, and the child seeds and one pole are arranged alternately in the whole. Also, among the various polarizations of the piezoelectric material,
Each polarization of the piezoelectric bodies up to the fourth from the feed eight electrode 8 side is set to a width (length of 1/2 wavelength of the applied voltage) such that the angle with respect to the center of the piezoelectric body is, for example, 36°, The width of the fifth polarized portion 3a, 3a is 3/8 wavelength of the applied voltage. The reason why the width of the fifth polarized portion is made small in this way is to effectively utilize the drive area of the piezoelectric body.

Note that the width of the feedback electrode 8 is 1/of the applied voltage.
The piezoelectric body 3 is formed to have four wavelengths, and the diameter of the piezoelectric body 3 is 30I, and the diameters of the elastic body 1 and the rotor 7 also correspond to the piezoelectric body 3, but the other configurations are the same as those of the previous embodiment.

In the above embodiment, each polarization width of the piezoelectric body and [11 of the feedback electrode 8] are expressed as a predetermined ratio to the wavelength of the applied voltage, but the same effect can be obtained as long as the range approximates these values. be.

"Effects of the Invention" The ultrasonic motor input control device of the present invention has the polarization width of the piezoelectric body and the width of the feedback electrode of the two types described above, so that the induction of the high frequency voltage applied to the piezoelectric body can be controlled by the feedback electrode. This makes it possible to accurately control the applied high-frequency voltage. Therefore, the traveling waves generated in the elastic body are stabilized, and the rotational speed or output torque of the ultrasonic motor can be kept stable. Furthermore, since the piezoelectric body can be effectively driven over a wide range, the driving efficiency of the ultrasonic motor is good.

[Brief explanation of the drawing]

FIG. 1 is a front view of the ultrasonic motor part of the present invention, FIG. 2 is a system diagram of the input control device of the ultrasonic motor, FIG. 3 is a plan view showing the polarization pattern of the piezoelectric body of the second embodiment, and FIG. FIG. 4 is a system diagram of a conventional input control device for an ultrasonic motor. l; Elastic body 3; Piezoelectric body 4; Electrode 5; High frequency voltage source 8; Feedback electrode 9; Input control circuit

Claims (2)

[Claims] (1) Attach an annular piezoelectric body to the surface of an elastic body whose outer periphery is circular, divide the piezoelectric body into two, and each
゜By applying high frequency voltages with different phases through the piezoelectric electrodes, a traveling wave is generated in the elastic body, and the traveling wave enables the rotor that is in pressure contact with the elastic body to rotate. In an input control device for an ultrasonic motor, a feedback electrode is provided at the boundary, and an input control circuit controls the applied high-frequency voltage and frequency according to the voltage generated therein. Ultrasonic waves that are polarized in alternating and continuous polarity and negative polarity, and that an interval of approximately the same width as the feedback electrode is provided between the feedback electrode and the polarized portions of the piezoelectric body located on both sides. Motor input control device. (2) By attaching an annular piezoelectric body to the surface of an elastic body with a circular outer circumference, dividing the piezoelectric body into two parts, and applying high frequency voltages with a phase difference of 90° to each part through piezoelectric electrodes. A traveling wave is generated in the elastic body, and the rotor pressed against the elastic body is made to rotate by the traveling wave.A feedback electrode is provided at the boundary between the two piezoelectric body parts, and an input signal is input according to the voltage generated there. In an input control device for an ultrasonic motor in which the applied high-frequency voltage and frequency are controlled by a control circuit, both sections of the piezoelectric body are polarized alternately and continuously as a positive pole and a single pole, respectively, and a feedback electrode is used. The width of each polarized portion in both sections of the piezoelectric body is 3/8 wavelength long, and the width of each remaining polarized portion is 1/2 wavelength long. An input control device for an ultrasonic motor, characterized in that the input control device is formed to have a length of .