JP2628044B2 - Ultrasonic motor input control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ultrasonic motor in which a moving member is moved by generating a traveling wave in an elastic body by a piezoelectric body.
The present invention relates to an input control device that controls a high-frequency voltage input to a piezoelectric body.

[Prior art] Conventional ultrasonic motors have a piezoelectric body attached to an elastic body as shown in FIG. 6, divide the piezoelectric body into two sets, and make a positive pole and a negative pole at a pitch of 1/2 wavelength of the input high frequency. A piezoelectric electrode having alternating poles is provided, and high-frequency voltages having different π / 2 wavelengths are applied to two sets of piezoelectric members to generate a traveling wave in the elastic body. The traveling wave causes the moving element pressed against the elastic body to rotate or linearly move.

The high-frequency voltage applied to each piezoelectric body is resonated so that its frequency is equal to the natural frequency of the elastic body, but the temperature of the ultrasonic motor itself, the state of pressure of the movable body against the elastic body, The resonance frequency is likely to shift due to friction or the like.
For this reason, a feedback electrode is provided at the boundary between the two sets of piezoelectric members, and a voltage change is caused in the piezoelectric member of the feedback electrode by vibration from the piezoelectric member adjacent thereto. Then, the input control circuit receives the voltage change via the feedback electrode, and the input control circuit controls the high-frequency voltage to improve the driving efficiency of the ultrasonic motor.

"Problems to be solved by the invention" Conventionally, in order to control the high-frequency voltage applied to the piezoelectric body,
Although the feedback electrode is provided at the boundary between the two piezoelectric members, the piezoelectric member of the feedback electrode receives different vibrations due to the influence of each piezoelectric member on both sides of the feedback electrode. It was found in many experiments by the inventors.

For this reason, the piezoelectric body of the feedback electrode portion cannot accurately detect whether or not a predetermined traveling wave is generated in the elastic body, and input control to the piezoelectric body cannot be sufficiently performed. If the control is insufficient, there is a problem that the rotational speed or output torque of the ultrasonic motor varies.

“Means for Solving the Problems” The present invention provides a method of attaching a piezoelectric body along the surface of an elastic body, dividing the piezoelectric body into two parts, and applying a high-frequency voltage different by π / 2 wavelength to each of the piezoelectric electrodes. , Thereby generating a traveling wave in the elastic body. A moving element is pressed against the elastic body, and the moving element receives a traveling wave and moves. A feedback electrode is provided at the boundary between the two sections of the piezoelectric body, and a voltage generated therefrom is input to an input control circuit, and the input control circuit controls a high-frequency voltage applied to the piezoelectric body. The first electrodes of the piezoelectric portions located on both sides of the feedback electrode are made to have different polarities, and the feedback electrode is divided into two sizes, each of which has a positive pole and a negative pole. The piezoelectric body does not receive different vibrations from both sides.

In addition, one of the intervals between the feedback electrode and the piezoelectric portions on both sides thereof may be cut off.

[Operation] In the above-mentioned means, the feedback electrode is divided into two parts, each having a positive electrode and a negative electrode, or one of the electrodes of the piezoelectric portion on both sides of the feedback electrode. Since the piezoelectric body in the space between the feedback electrode and the feedback electrode is cut off, the piezoelectric body in the feedback electrode section does not receive different vibrations from the piezoelectric bodies on both sides, and the piezoelectric body in the feedback electrode section is elastic. The displacement according to the vibration of the traveling wave generated in the body can be accurately detected. Therefore, the high frequency voltage applied to the piezoelectric body can be accurately controlled by the input control circuit, and the driving efficiency of the ultrasonic motor can be improved.

"Embodiment" A first embodiment of the present invention will be described with reference to FIGS.

A ring-shaped earth electrode 2 is attached to one end face in the axial direction of the annular elastic body 1, a ring-shaped piezoelectric body 3 is provided on an outer surface of the earth electrode 2, and a positive electrode and a negative electrode are provided on the outer surface.
The pole electrodes 4 are alternately and continuously arranged. If the elastic body 1 is directly grounded, the ground electrode 2 becomes unnecessary. The pitch of each of the + and-electrodes 4 provided on the piezoelectric body 3 is half the wavelength of the applied high-frequency voltage. The piezoelectric body 3 is divided into two semicircular sets with a space between the boundary positions, and in each section, as shown in FIG. 2, a pair of electrodes 4 having a positive pole and a negative pole is provided in this embodiment. Four pairs are provided for each. The electrodes 4 are directly connected to the high-frequency voltage source 5 and the other is connected to the phase shifter 6 so that the cos voltage and the sin voltage, which are different from each other by π / 2 wavelength, are applied to the two sets of the piezoelectric bodies 3 respectively. Connected via.

When a voltage is applied, vibrations are generated in the two sets of the piezoelectric members 3, thereby generating a traveling wave in the elastic body 1, and further, the moving member 7 pressed against the elastic body 1 is rotated by receiving the traveling wave. Has become.

One of the intervals between the electrode boundaries of the two sections of the piezoelectric body 3 is 3/4.
It is a wavelength, and the feedback electrode 8 is arranged at the interval, so that the generated voltage can be taken out from the piezoelectric body 3 in that portion. Although the feedback electrode 8 is arranged close to one of the adjacent piezoelectric members, it may be located at any position within the interval. The feedback electrode 8 is connected to an input control circuit 12, and the input control circuit 12 controls the high-frequency voltage source 5 according to the voltage generated on the piezoelectric body of the feedback electrode 8 portion. The electrodes 4a and 4b of the piezoelectric portion on both sides of the feedback electrode 8 may have a positive or negative polarity as long as they have the same polarity, and the feedback electrode 8 may have a positive or negative polarity.

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

This embodiment is applied when the first electrodes 4a and 4b of the piezoelectric portions located on both sides of the feedback electrodes 8a and 8b have polarities different from each other, and the feedback electrodes 8a and 8b are half of the first embodiment. Two lengths were used.

The two feedback electrodes 8a and 8b are composed of a positive electrode and a negative electrode, each having a different polarity from the electrodes 4a and 4b of the adjacent piezoelectric body, but having the same polarity. Is also good. And two feedback electrodes 8a, 8b
Are connected to the input control circuit 12, respectively. In this case, the input control circuit 12 receives voltage signals from the two feedback electrodes 8a and 8b, and compares the two voltages with a voltage when a predetermined traveling wave is generated to switch the high-frequency voltage source 5 Control.

 Next, a third embodiment will be described with reference to FIGS.

This embodiment is applied irrespective of the polarity of the feedback electrode 8 and the electrodes 4a and 4b of the piezoelectric portions on both sides thereof. Then, the piezoelectric body at the interval between the feedback electrode 8 and one of the right and left electrode portions (4a in this embodiment) adjacent thereto is cut. Vibration from the adjacent piezoelectric body portion is not transmitted to the piezoelectric body in the feedback electrode 8 portion through the cut portion 10. Other configurations are the same as those of the first embodiment.

In the above three embodiments, the elastic body is formed in a ring shape and the system is rotated. However, the present invention is directed to an ultrasonic motor in which the elastic body is formed in a straight line and the moving element is moved in a linear direction. Also applicable to

[Effect of the Invention] In the input control device for an ultrasonic motor according to the present invention, since the feedback electrode is composed of two positive and negative electrodes, the feedback electrode and the piezoelectric electrode on one side adjacent thereto are connected to the feedback electrode. Is cut off, the piezoelectric body of the feedback electrode portion does not receive two different types of vibration. Therefore, the voltage generated in the piezoelectric body of the feedback electrode portion can accurately detect whether or not a predetermined traveling wave is generated, and by controlling the input high-frequency voltage based on the detected value, the driving efficiency of the ultrasonic motor can be reduced. Can be improved.

[Brief description of the drawings]

FIG. 1 is a front view of an ultrasonic motor part of the present invention, FIG. 2 is a system diagram of an input control device of the ultrasonic motor, FIG. 3 is a plan view showing an arrangement state of electrodes of the second embodiment, FIG. FIG. 5 is a plan view showing the arrangement of electrodes in the third embodiment, FIG. 5 is a partially cutaway front view of FIG. 4, and FIG. 6 is a system diagram of a conventional ultrasonic motor input control device. 1: Elastic body, 3: Piezoelectric body 4: Electrode, 5: High frequency voltage source 8: Feedback electrode 12: Input control circuit, 10: Cutting section

Claims (2)

(57) [Claims] An elastic body is provided by attaching a piezoelectric body along the surface of an elastic body, dividing the piezoelectric body into two parts, and applying high-frequency voltages having different π / 2 wavelengths to each other through a piezoelectric body electrode. A traveling wave is generated, and the moving element pressed against the elastic body can be moved by the traveling wave. A feedback electrode is provided at the boundary between the two divided piezoelectric members, and input control is performed in accordance with the voltage generated thereby. In the input control device for an ultrasonic motor, wherein the applied high-frequency voltage is controlled by a circuit, the first electrodes of the piezoelectric portions located on both sides of the feedback electrode are made to have different polarities, and the feedback electrode is , A positive pole and a negative pole. 2. A method of mounting a piezoelectric body along the surface of an elastic body, dividing the piezoelectric body into two parts, and applying high-frequency voltages different by π / 2 wavelength to the respective elastic bodies through piezoelectric electrodes. A traveling wave is generated, and the moving element pressed against the elastic body can be moved by the traveling wave. A feedback electrode is provided at the boundary between the two divided piezoelectric members, and input control is performed in accordance with the voltage generated thereby. In the input control device for an ultrasonic motor, wherein the applied high-frequency voltage is controlled by a circuit, the piezoelectric member is disposed at one of two intervals between the feedback electrode and the electrodes of the piezoelectric portions located on both sides of the feedback electrode. An input control device for an ultrasonic motor, wherein the input control device is in a cutting state.