JPH0442785A - How to drive an ultrasonic motor - Google Patents

Abstract

PURPOSE:To facilitate start of a motor even if a rotor and a stator are in an adhesion state or a high load is applied to the motor by a method wherein a timer is operated by the starting switch of the motor and the voltage of a driving power supply which is inputted to the driving circuit of the motor is elevated by a voltage transforming circuit for a certain period. CONSTITUTION:Piezoelectric devices 2 are bonded to a stator 1 and a progressive wave is generated by applying driving signals which have a phase difference of 90 deg. between each other from a driving circuit 3 to a pair of the electrodes of the piezoelectric devices 2 to make a rotor pressed against the stator 1 rotate. A driving power supply signal is supplied to the driving circuit 3 from a driving power supply 5 through a voltage transforming circuit 5. The voltage transforming circuit 5 is operated for a certain period by a timer 7 when a starting switch 6 is turned ON to transform an output signal into a high voltage signal. With this constitution, when the starting switch 6 is turned ON, the timer 7 operates the voltage transforming circuit 4 for a certain period to elevate the voltage of the driving signal temporarily, so that a motor can be started by a large torque even if the motor is prevented from starting with ease.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application 1] The present invention relates to a method for driving an ultrasonic motor, in which the driving voltage is temporarily increased when starting the motor.

[Prior Art] In an ultrasonic motor, a piezoelectric element bonded to the stator generates a traveling wave in the stator, a spring presses the rotor against the stator, and the traveling wave of the stator rotates the rotor. In addition, the stator is provided with a large number of protrusions radially in order to increase the amplitude of the traveling waves, and a slider as a friction material is glued to the surface where the rotor contacts the many protrusions of the stator, so that the traveling waves of the stator are We are trying to make it work effectively.

[Problem to be solved by the invention] Do not use an ultrasonic motor (if it is stored for a long time, the rotor will continue to be strongly pushed toward the stator side by the spring, so the stator The slider B on the rotor side got stuck in the groove between the many protrusions A of the rotor, and this adhesion phenomenon sometimes made it impossible to start the ultrasonic motor.Also, due to the ambient temperature of the ultrasonic motor, the pressure contact between the rotor and stator The ultrasonic motor may become unable to start because the force changes or a predetermined traveling wave is not generated, and furthermore, when the load on the motor is large, the ultrasonic motor may become unable to start.

Therefore, an object of the present invention is to temporarily increase the voltage of the drive signal when starting the ultrasonic motor, so that the ultrasonic motor can be started easily even when the rotor and stator are stuck or under high load. do.

[Means for Solving the Problems] The present invention is a method for driving an ultrasonic motor that achieves the above-mentioned object, and is a method for driving an ultrasonic motor, which operates a timer that is connected to a start switch of the motor, and the motor drive circuit is activated for a certain period of time. The voltage of the drive power input to the system is increased by a voltage change circuit.

[Function] In the above ultrasonic motor driving method, when the starting switch is
When activated, the timer activates the voltage change circuit for a certain period of time to increase the power supply voltage. For this reason, the drive circuit increases the drive voltage for a certain period of time (T) when the motor starts, as shown in Figure 2, so the amplitude of the traveling wave generated in the stator increases, resulting in a large output and starting the motor. be able to.

[Example] An embodiment of the present invention will be described with reference to FIG.

In the ultrasonic motor, a piezoelectric element 2 is bonded to a stator l, and two sets of electrodes of the piezoelectric element 2 are connected at 90 degrees from a drive circuit 3, respectively.
By applying a drive signal with a phase difference, a traveling wave is generated to rotate a rotor (not shown) that is pressed against the stator. Further, the drive circuit 3 includes a drive power source 5
A driving power signal from the converter is supplied via a voltage change circuit 4, and the voltage change circuit 5 is activated for a certain period of time by a timer 7 when the start switch 6 is turned on, and changes the output signal to a high voltage. There is.

Therefore, when the start switch 6 is turned on when starting the motor, the timer 7 operates the voltage change circuit 4 for a certain period of time, increasing the voltage from the drive power source 5. For this reason, the voltage of the drive signal output from the drive circuit 3 becomes temporarily high, and the motor is started with a large torque even in the starting state.

After the motor is started, the timer 7 expires, the voltage change circuit 4 supplies the voltage from the drive power source to the drive circuit 3 without increasing it, and the rotor is driven to rotate with normal torque.

[Effects of the Invention] According to the present invention, the voltage of the drive signal is increased only when starting the ultrasonic motor to generate high torque, so even if the rotor and stator are stuck or under high load, it is easy to The motor can be started. Also, after the motor starts,
Since the voltage of the drive signal is lowered to the normal state, energy efficiency is poor (there is no such thing).

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the method of driving an ultrasonic motor of the present invention, FIG. 2 is an explanatory diagram showing changes in driving voltage, and FIG.
The figure is an explanatory diagram showing a state in which a conventional ultrasonic motor cannot be started. 1; Stator 2: Piezoelectric element 3; Drive circuit 4; Voltage change circuit 7; Timer
8: Drive power supply Figure 1 Figure 2 Time → Figure 3 Applicant (Co., Ltd.) Co., Ltd. Taisei Electric Seisakusho agent Patent attorney Katsutsugu Maki

Claims (1)

[Claims] In an ultrasonic motor drive method, a driving signal is applied to a piezoelectric element bonded to the stator from a drive circuit connected to a drive power source to generate a traveling wave in the stator, thereby rotating a rotor pressed against the stator. A method for driving an ultrasonic motor, characterized in that a timer is activated by a start switch, and the voltage of a drive power source input to a drive circuit is increased by a voltage change circuit for a certain period of time.