Ultrasonic motor and electronic apparatus having ultrasonic motor

An ultrasonic motor comprising:

• a piezoelectric element;
• an oscillator bonded to the piezoelectric element for frictionally driving a moving body by means of an oscillation wave generated in the oscillator in response to elongation and contraction movement of the piezoelectric element;
• an oscillation drive circuit for generating the oscillation wave by self-excited oscillation of the oscillator;
• and
• start/stop signal generating means for generating an output signal for controlling the start/stop state of the ultrasonic motor by bringing the oscillation drive circuit into an active state or a stop state;
• wherein the oscillation drive circuit comprises a power amplifier for amplifying an excitation signal, a capacitive circuit for adjusting a frequency of the excitation signal, and an oscillation starting circuit for generating an oscillation start trigger signal based on the output signal from the start/stop signal generating means;
• and
• wherein the oscillation starting circuit for generating the oscillation start trigger signal is operated to generate the oscillation start trigger signal during a rise time period in which the oscillation drive circuit is brought into an active state and starts oscillation based on the output signal from the start/stop signal generating means.

An ultrasonic motor comprising:

• a piezoelectric element;
• an oscillator bonded to the piezoelectric element for frictionally driving a moving body by means of an oscillation wave generated in the oscillator in response to elongation and contraction movement of the piezoelectric element;
• an oscillation drive circuit for generating the oscillation wave by self-excited oscillation of the oscillator;
• and
• start/stop signal generating means for generating an output signal for controlling the starting and stopping of the ultrasonic motor by bringing the oscillation drive circuit into an active state and a stop state, respectively;
• wherein the oscillation drive circuit comprises a power amplifier for amplifying an excitation signal, a capacitive circuit for adjusting a frequency of the excitation signal, a switching circuit connected in parallel with a capacitive element of the capacitive circuit for short-circuiting terminals of the capacitive element based on the output signal from the start/stop signal generating means, and an oscillation starting circuit for generating an oscillation start trigger signal based on the output signal from the start/stop signal generating means;
• wherein when the oscillation drive circuit is brought into a stop state based on the output signal from the start/stop signal generating means, the switching circuit is turned ON and the terminals of the capacitive element are thereby brought into a short-circuited state to discharge the capacitive element during the stop state;
• and
• wherein when the oscillation drive circuit is brought into an active state based on the output signal from the start/stop signal generating means, the switching circuit is turned OFF and the oscillation starting circuit for generating the oscillation start trigger signal is operated to generate the oscillation start trigger signal during a rise time period of the start of oscillation.

An ultrasonic motor comprising:

• a piezoelectric element;
• an oscillator bonded to the piezoelectric element for frictionally driving a moving body by means of an oscillation wave generated in the oscillator in response to elongation and contraction movement of the piezoelectric element;
• an oscillation drive circuit for generating the oscillation wave by self-excited oscillation of the oscillator;
• and
• start/stop signal generating means for generating an output signal for controlling the starting and stopping of the ultrasonic motor by bringing the oscillation drive circuit into an active state and a stop state, respectively;
• wherein the oscillation drive circuit comprises a power amplifier having switching elements for amplifying an excitation signal, and a capacitive circuit for adjusting a frequency of the oscillation signal;
• and
• wherein the power amplifier of the oscillation drive circuit has an input unit comprising an inverter to provide an output to the switching elements of the power amplifier to compensate for dispersion in switching characteristics of the switching elements so that the switching elements operate at the same phase.

An ultrasonic motor comprising:

• a piezoelectric element;
• an oscillator bonded to the piezoelectric element for frictionally driving a moving body by means of an oscillation wave generated in the oscillator in response to elongation and contraction movement of the piezoelectric element;
• an oscillation drive circuit for generating the oscillation wave by self-excited oscillation of the oscillator;
• and
• start/stop signal generating means for generating an output signal for controlling the starting and stopping of the ultrasonic motor by bringing the oscillation drive circuit into an active state and a stop state, respectively;
• wherein the oscillation drive circuit comprises a power amplifier for amplifying an excitation signal and having an input unit comprising an inverter, a capacitive circuit for adjusting a frequency of the excitation signal and a switching circuit connected in parallel with a capacitive element of the capacitive circuit for short-circuiting terminals of the capacitive element based on the output signal from the start/stop signal generating means;
• and
• wherein when the oscillation drive circuit is brought into a stop state based on the output signal from the start/stop signal generating means, the switching circuit is turned ON and the terminals of the capacitive element are thereby brought into a short-circuited state to discharge the capacitive element during the stop state.

An ultrasonic motor comprising:

• a piezoelectric element;
• an oscillator bonded to the piezoelectric element for frictionally driving a moving body by means of an oscillation wave generated in the oscillator in response to elongation and contraction movement of the piezoelectric element;
• an oscillation drive circuit for generating an oscillation wave by self-excited oscillation of the oscillator;
• and
• start/stop signal generating means for generating an output signal for controlling the starting and stopping of the ultrasonic motor by bringing the oscillation drive circuit into an active state and a stop state, respectively;
• wherein two sets of electrode groups comprising a plurality of electrodes are formed on a surface of the piezoelectric element;
• wherein the oscillation drive circuit comprises two power amplifiers having output terminals which are connected respectively to the two sets of electrode groups formed on the surface of the piezoelectric element to excite the respective electrode groups independently from each other, and a capacitive circuit for adjusting a frequency of an excitation signal;
• wherein a rotational direction of the moving body is switched by selecting which of the two power amplifiers is placed in an active state;
• and wherein the ultrasonic motor further comprises self-excited oscillation rise controlling means for forming an initial signal in the oscillation drive circuit by bringing both of the two power amplifiers into the active state when the ultrasonic motor is started and bringing only one of the power amplifiers into a stop state and starting a driving operation in accordance with the output signal from the start/stop signal generating means after the initial signal has been amplified to the excitation signal by the oscillation drive circuit.

An ultrasonic motor comprising:

• a piezoelectric element;
• two sets of electrode groups comprising a plurality of electrodes formed on a surface of the piezoelectric element;
• an oscillator bonded to the piezoelectric element for frictionally driving a moving body by means of an oscillation wave generated in the oscillator in response to elongation and contraction movement of the piezoelectric element;
• an oscillation drive circuit for generating the oscillation wave by self-excited oscillation of the oscillator, the oscillation drive circuit comprising a plurality of power amplifiers connected in parallel with each other and having an input unit comprising an inverter for amplifying an excitation signal, each power amplifier having output terminals which are connected respectively to the two sets of electrode groups formed on the surface of the piezoelectric element for driving the respective electrode groups independently from each other, and a capacitive circuit for adjusting a frequency of the oscillation signal;
• output adjusting signal generating means for outputting a signal for adjusting an output impedance of the oscillation drive circuit by selecting which of the plurality of power amplifiers is to be activated;
• start/stop signal generating means for generating an output signal for controlling the starting and stopping of the ultrasonic motor by bringing the oscillation drive circuit into an active state and a stop state, respectively;
• wherein a rotational direction of the moving body is switched by switching the one of the power amplifiers placed in an active state based on the output signal from the start/stop signal generating means.