JPH0799787A - Driving circuit for ultrasonic motor - Google Patents

Abstract

PURPOSE:To simplify the construction of an ultrasonic motor device and to make it small in size by a method wherein an electric signal outputted by a movement detecting means using a magnetic-electrical energy conversion element is transmitted in superposition on a conductor impressing a sine wave voltage on an electrical- mechanical energy conversion element. CONSTITUTION:When sine wave voltages in the vicinity of a resonant frequency of which phases are shifted by an angle of 90 degrees from each other are impressed on a first piezoelectric element 4 and a second piezoelectric element 5, a rotor of an ultrasonic motor rotates and an alternating voltage of a frequency proportional to a rotational speed is generated in a coil 35 by a magnet 34 rotating integrally with the rotor. This alternating voltage is amplified by an amplifier 46 provided in an internal circuit part 53 of the motor and it is superposed on a conductor 45 impressing a driving voltage and is transmitted to an external motor control circuit part 52. Then, only a rotation signal is separated in a signal separating circuit 47 and inputted to a rotational speed control circuit 49. According to this constitution, the number of conductors 45 connecting the internal circuit part 53 of the ultrasonic motor with the external motor control circuit part 52 can be reduced and an ultrasonic motor device can be made small in size.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor drive circuit, and more particularly to an ultrasonic motor drive circuit that rotates by utilizing vibration generated by an electro-mechanical energy conversion element.

[0002]

2. Description of the Related Art Conventionally, various ultrasonic motors using ultrasonic vibrators have been proposed, and an example will be described with reference to FIGS. 6 and 7.

FIG. 6 is a perspective view showing an example of a conventional ultrasonic motor, showing a laminated state of the motor. Further, FIG. 7 shows an assembled sectional view of a half of the ultrasonic motor from the central axis.

As shown in the figure, the first and second piezoelectric elements 4 and 5 each having a substantially circular plate shape with a hollow circular portion formed at the center are
The sliding oscillator is polarized so that the polarization direction (arrow) is perpendicular to the axis. Further, the polarization directions of the first piezoelectric element 4 and the second piezoelectric element 5 are displaced by 90 °.

Electrode plates 6, 7 and 8 are arranged above the first piezoelectric element 4, below the second piezoelectric element 5 and between the first piezoelectric element 4 and the second piezoelectric element 5, respectively. There is.
The resonator 9 is made of a material excellent in vibration transmission, and an insulating member is formed in a thin film on the surface where the resonator 9 is installed. A through hole 10 through which the fastening member 3 penetrates is provided at the center of the resonator 9, and the end surface of the resonator 9 is fastened from the direction of the end surface of the ultrasonic transducer 11 to the piezoelectric elements 4 and 5. A conical cup-shaped hollow portion 12 is formed so as not to come into contact with 3.

Further, the resonator 9 has a groove 14 that divides a part of the resonator 9 into eight equal parts in the direction from the direction in which the rotor 13 is installed to the direction in which the piezoelectric elements 4 and 5 are installed. And eight displacement magnifying vibrating pieces 15 are formed in parallel with. Further, on the outer peripheral side surface of the resonator 9, grooves 16 and 17 having a predetermined depth are formed in a concentric circle shape with the outer periphery in a portion which becomes a node of bending vibration and in the vicinity of a base of the displacement magnifying vibration piece 15. Has been done.

On the end face of the rotor 13 on the resonator 9 side, a magnet 34 is equally divided into four poles and the rotor 34 is magnetized.
It is glued so that it is coaxial with 3.

On the other hand, the resonator 18 arranged on the other end face of the piezoelectric elements 4 and 5 is also made of the same material as that of the resonator 9, and has a threaded portion 19 for coupling with the fastening member 3 at the center thereof. Is formed, and a taper 20 is formed on the outer circumference. A projecting portion 21 is formed around the central axis at the projecting end of the taper 20 to reduce the contact area with an external fixing member.

As shown in the figure, the ultrasonic transducer 11 includes the first piezoelectric element 4, the second piezoelectric element 5, the electrode plates 6, 7,
8, the resonator 9 and the crimp nut 2 in a state where the resonator 9 is passed through the bolt 3 having two screw parts as fastening members.
It is sandwiched between two. The bolt 3, which is the fastening member, is made of an insulating ceramic material so that the resonator 9 and the resonator 18 are not electrically connected.

The bolt 3 constitutes an ultrasonic transducer 11 by pressure bonding and supports a rotor 13 having a pressing mechanism on the end face of the ultrasonic transducer 11.

In addition, a sinusoidal voltage near the resonance frequency, which is 90 ° out of phase with each other, is applied to the electrode plate 6 and the electrode plate 7,
The voltage is applied from a drive circuit (not shown) through a conductor, and the electrode plate 8 is connected to the ground by the conductor.

Further, below the magnet 34 above the crimp nut 22, there is a coil 35 formed by winding a conductive wire 36 on a bobbin 35a in which a winding groove is formed in four equal parts. A hole formed in the central portion of 35a is inserted and fixed by the bolt 3.

In the ultrasonic motor described above, when a sinusoidal voltage near the resonance frequency with a phase difference of 90 ° is applied to the two sets of piezoelectric elements 4 and 5, the ultrasonic vibrator 11 rotates about the central axis. Flexural vibration occurs. As a result, an elliptical motion that rotates around the central axis is generated on the end surface of the ultrasonic transducer 11, and the rotor 13 that is pressed and installed rotates. Further, when the phase difference of the drive voltage is 180 °, the ultrasonic oscillator 11 causes an elliptic motion of reverse rotation, and the rotor 13 rotates in reverse.

Further, the magnetic flux which is linked to the coil 34, which is a rotation detector composed of a magnetic-electrical energy conversion element disposed in the vicinity of the magnet 34, is changed by the magnet 34 which rotates simultaneously with the rotor 13, A voltage or frequency signal proportional to the rotation speed of the rotor 13 is generated in the magnetic-electrical energy conversion element.

The signal proportional to the rotation speed is guided to the outside by a conductor wire provided separately from the conductor wire for applying the sinusoidal voltage to the two sets of piezoelectric elements 4 and 5, and is connected to the drive circuit. .

[0016]

However, in the above-mentioned conventional technical means, in order to drive the ultrasonic motor, a rotating wire constituted by a conductive wire for supplying electric power to the piezoelectric element and a magnetic-electrical energy conversion element is used. A conductor for guiding a signal proportional to the rotation speed detected by the detector to an external ultrasonic motor control circuit is separately required. As a result, a large number of conductors connecting the ultrasonic motor and the motor control circuit impede miniaturization of the ultrasonic motor device.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a driving circuit for a smaller ultrasonic motor with a simple structure.

[0018]

In order to achieve the above object, a drive circuit for an ultrasonic motor according to the present invention is provided with two resonators for transmitting and expanding ultrasonic vibrations, and between these two resonators. And an electro-mechanical energy conversion element that generates ultrasonic vibration by applying a sinusoidal voltage, and a fastening that forms an ultrasonic vibrator by crimping and fixing the two resonators and the electro-mechanical energy conversion element. Means and
A driven member that is moved by an elliptical motion generated on the end face of the resonator, a magnetic body that is fixed to the driven member and is magnetized, and a magnetic flux that generates an electric signal by interaction with the magnetic flux of the magnetic body. A movement detecting means using an electric energy converting element, and transmitting the electric signal by superimposing the electric signal on a conducting wire to which the sine wave voltage is applied.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing an ultrasonic motor according to the first embodiment of the present invention, showing a laminated state of the ultrasonic motor. Further, FIG. 2 shows an assembly cross-sectional view of the ultrasonic motor, which is half of the central axis. In this embodiment, a piezoelectric element having silver vapor deposited on the voltage application surface is used as the electromechanical energy conversion element. Further, FIG. 1 shows only the motor internal circuit portion 53 (see FIG. 3) that is integrally formed with the ultrasonic motor in the drive circuit of the ultrasonic motor of the present embodiment. The external motor control circuit portion 52 (see FIG. 3) disposed apart from is not shown.

As shown in the figure, the first piezoelectric element 4 and the second piezoelectric element 5 each having a substantially circular disk shape having a hollow circular portion are both constituted by a sliding oscillator, and the polarization direction indicated by the arrow in the figure is It is polarized so that it is perpendicular to the axis. And the first
The polarization directions of the piezoelectric element 4 and the second piezoelectric element 5 are 90 degrees relative to each other.
They are arranged offset.

Further, above the first piezoelectric element 4, below the second piezoelectric element 5, and between the first piezoelectric element 4 and the second piezoelectric element 5.
The electrode plates 6, 7, and 8 are respectively disposed between and.

The resonator 9 is made of a material excellent in vibration transmission (aluminum alloy, stainless steel, phosphor bronze, duralumin, titanium alloy, etc.). Electrode plate 6
An insulating member is formed in a thin film on the installation surfaces of and.

Further, a through hole 10 through which the fastening member 3 penetrates is provided at the center of the resonator 9, and the resonance is performed in the direction from the end face of the ultrasonic transducer 11 to the piezoelectric elements 4 and 5. A conical cup-shaped hollow portion 12 is formed so that the end surface of the container 9 does not come into contact with the fastening member 3.

Further, in the resonator 9, the direction in which the rotor 13 is installed is changed from the direction in which the piezoelectric elements 4 and 5 are installed.
A groove 14 that divides a part of the resonator 9 into eight equal parts is formed in parallel with the central axis to form eight displacement magnifying vibrating pieces 15.
Also, on the outer peripheral side surface, a portion that becomes a node of bending vibration,
Grooves 16 and 17 having a predetermined depth are formed concentrically with the outer periphery in the vicinity of the base of the displacement magnifying vibration piece 15.

On the surface of the rotor 13 on the resonator 9 side, permanent magnets 34 magnetized into four poles are equally divided.
It is adhered integrally so as to be coaxial with 3.

The resonator 18 arranged on the other end surface of the first piezoelectric element 4 and the second piezoelectric element 5 is also made of the same material as that of the resonator 9. A screw portion 19 that is coupled to the fastening member 3 is formed at the center of the resonator 18, and the outer peripheral surface of the resonator 18 is formed with a taper 20 downward. A projecting portion 21 is formed around the central axis at the projecting end of the taper 20 to reduce the contact area with an external fixing member.

The ultrasonic oscillator 11 is a fastening member (bolt) having two screw portions which are fastening members for the first piezoelectric element 4, the second piezoelectric element 5, the electrode plates 6, 7, 8 and the resonator 9. ) 3 and the resonator 18 and the crimp nut 22 in a state of being penetrated.
Sandwiched between them, after applying epoxy adhesive between each component,
It is formed by pressure bonding and curing the adhesive. The fastening member 3 is made of an insulating ceramic material so that the resonator 9 and the resonator 18 are not electrically connected to each other.

The fastening member 3 is formed by crimping the ultrasonic oscillator 11, and supports the rotor 13 having a pressing mechanism on one end surface of the resonator 9 without the ultrasonic oscillator 11. In this embodiment, a pressing mechanism is used in which the amount of crimping the disc spring 23 can be varied by the nut 24. The rotor 13 of this embodiment is made of an aluminum alloy material and treated with an oxalic acid alumite sliding member, and two thin spring flange portions 25 are formed in the vicinity of the contact portion with the ultrasonic transducer 11 (resonator 9). The fastening member 3 is rotatably supported via a bearing 42. Further, the natural frequency of the contact portion of the rotor 13 is set higher than the drive frequency of the ultrasonic transducer 11.

Further, above the nut 22 and below the permanent magnet 34, magnetic wire-to-electric energy conversion is formed by winding a conducting wire 36 around a bobbin 35a having a winding groove formed in four equal parts. The coil 35, which is an element, is inserted and fixed by a fastening member 3 through a hole provided at the center of the bobbin 35a. A conductor wire 50 is connected to the other end of the conductor wire 36.

On the other hand, a circuit board 51 is inserted and fixed to the outside of the resonator 18 by the fastening member 3 on the side of the fixing member.

FIG. 3 is a block diagram showing a simplified electrical structure of the entire drive circuit of the ultrasonic motor of this embodiment.

As shown in this figure, a sine wave voltage near the resonance frequency, which is 90 ° out of phase with each other, is applied to the drive circuit 4 in the external motor control circuit section 52 on the electrode plate 6 and the electrode plate 7.
4 is applied through a lead wire 45, and the electrode plate 8 is connected to the ground by a lead wire 45.

Both ends of the coil 35 are connected via a conductor 50 to an amplifier 46 provided on the circuit board 51.
The output terminal of the amplifier 46 connected to the input terminal (included in the motor internal circuit section 53) is connected to the conductor 45. A terminal of the lead wire 45 on the side of the external motor control circuit 52 is connected to an output terminal of the drive circuit 44 and an input terminal of the signal separation circuit 47, on which a rotation signal is superimposed on the motor driving sine wave voltage.

The lead wire 45 is used for the motor internal circuit section 5.
3 is connected to the input terminal of the rectifier circuit 48, and the output terminal of the rectifier circuit 48 is connected to the power supply terminal of the amplifier 46. Further, the output of the signal separation circuit 47 is connected to the input terminal of the rotation speed control circuit 49, and the output of the rotation speed control circuit 49 is input to the drive circuit 44.

FIG. 4 is a block diagram showing the rotation speed control circuit 49 in more detail.

As shown in the figure, the rotation speed control circuit 49
Is provided with a phase comparison circuit 55 for comparing the phase of the signal from the signal separation circuit 47 and the signal of the reference signal oscillation circuit 54. The phase comparison circuit 55 generates a DC voltage proportional to the phase difference between the two input signals. The output DC voltage is input to the voltage controlled oscillation circuit 56 and the oscillation circuit is proportional to the input DC voltage. It is designed to generate a signal of the specified frequency. The output of the voltage controlled oscillation circuit 56 is input to the drive circuit 44, adjusted to a predetermined voltage, and then supplied to the motor through the conductor 45 to control the rotation of the motor.

Next, the operation of this embodiment will be described.

When a sinusoidal voltage near the resonance frequency with a phase difference of 90 ° from each other is applied to the two sets of the first piezoelectric element 4 and the second piezoelectric element 5, the ultrasonic transducer 11 is bent to rotate about the central axis. Vibration occurs. Thereby, the ultrasonic transducer 1
Elliptic motion rotating around the central axis occurs on the end face of 1.
The rotor 13 pressed and installed on one end surface of the resonator 9 rotates. When the phase difference of the driving voltage is set to 180 °, a reverse elliptical motion is generated in the ultrasonic transducer 11, which causes
The rotor 13 rotates in the reverse direction.

Further, the magnetic flux linked to the coil 35 arranged in the vicinity thereof is changed by the magnet 34 which rotates integrally with the rotor 13, and the induction of the coil 35 is proportional to the rotational speed of the rotor 13. Voltage is generated. The generated induced voltage becomes an alternating voltage, and its frequency is proportional to the rotation speed.

The alternating voltage proportional to the rotation speed is amplified in the vicinity of the motor, that is, by the amplifier 46 provided on the circuit board 51, and is superimposed on the lead wire 45 for applying the drive voltage to the external motor control circuit section. Up to 52 are transmitted.

Then, in the signal separating circuit 47 in the external motor control circuit section 52, the drive signal of the substantially resonant frequency of the first piezoelectric element 4 and the second piezoelectric element 5 and the rotation signal lower than the drive signal frequency are combined. Only the rotation signal is separated from the generated signal.

The rotation signal is input to the rotation speed control circuit 49 in the external motor control circuit section 52, and the phase of the signal is compared with the signal of the reference signal oscillation circuit 54 by the phase comparison circuit 55. The phase comparison circuit 55 generates a DC voltage proportional to the phase difference between the two input signals. The output DC voltage of the phase comparison circuit 55 is the voltage controlled oscillation circuit 56.
The oscillator circuit generates a signal having a frequency proportional to the input DC voltage. The output of the voltage controlled oscillation circuit 56 is input to the drive circuit 44, adjusted to a predetermined voltage, and then supplied to the motor through the lead wire 45 to control the rotation of the motor.

The DC voltage obtained by rectifying the drive voltage of the first piezoelectric element 4 and the second piezoelectric element 5 by the rectifier circuit 48 drives the amplifier as a power supply voltage source of the amplifier 46.

According to the present embodiment as described above, the rotation signal detected by the magnetic-electrical energy conversion element is transmitted by being superposed on the conductor wire for applying the sine wave voltage to the electric-mechanical energy conversion element. , The number of conductors connecting the ultrasonic motor and the motor control circuit can be reduced,
The device using the ultrasonic motor can be downsized,
Also, the cost of wiring can be reduced.

Next, a second embodiment of the present invention will be described.

FIG. 5 is a perspective view showing the ultrasonic motor of the second embodiment.

The second embodiment is an embodiment in which the magnetic-electrical energy conversion element is a Hall element, and the other structure is the same as that of the first embodiment. Therefore, only the difference will be explained here. , And the description of other equivalent parts will be omitted. Further, only the arrangement of the magnetic-electric energy conversion element is shown, and other constituent members such as an electrode plate are omitted.

In the second embodiment, the permanent magnet 34 is used as the magnetized magnetic body as in the first embodiment.
The Hall element 40, which serves as a rotation signal generator, is adhesively connected to the printed wiring board 38. In the second embodiment, a flexible wiring board is used as the printed wiring board 38. In the second embodiment, a flexible printed wiring board 38 is used as the conductive wire 45. In the first embodiment, the amplifier 46 and the rectifier circuit 48 arranged on the circuit board 51 are the printed wiring boards. It is arranged on the plate 38.

Next, the operation of the second embodiment will be described.

The magnetic flux linked to the Hall element 40 is changed by the magnet 34 fixed to the rotor 13 and rotating integrally with the rotor 13. As a result, a voltage change having a frequency proportional to the rotation speed of the rotor 13 is generated in the Hall element 40.

The generated voltage change is due to the printed wiring board 38.
It is amplified by the amplifier 46 arranged above and taken out to the outside by the conductor on the printed wiring board 38.
The Hall current given to 0 is given by a DC voltage obtained by rectifying the drive voltage of the piezoelectric element by the rectifier circuit 48.

According to the drive circuit of the ultrasonic motor of the second embodiment, the Hall effect is utilized, so that the rotor 13
The magnetic flux can be detected even when the rotor is stopped, and the position as well as the speed of the rotor 13 can be detected. Furthermore, the hall element 40, the amplifier 46, and the rectifier circuit 48 can be formed on the same printed wiring board 38, and the ultrasonic motor can be further downsized.

[0054]

As described above, according to the present invention, it is an object of the present invention to provide a drive circuit for a smaller ultrasonic motor with a simple structure.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of an ultrasonic motor according to a first embodiment of the present invention.

FIG. 2 is a side sectional view showing a half of a central axis of the ultrasonic motor in a section.

FIG. 3 is a block diagram showing an electrical configuration of an entire drive circuit of the ultrasonic motor of the first embodiment.

FIG. 4 is a block diagram showing a rotation speed control circuit in the drive circuit for the ultrasonic motor of the first embodiment.

FIG. 5 is a perspective view showing a configuration of an ultrasonic motor according to a second embodiment of the present invention.

FIG. 6 is a perspective view showing an example of a conventional ultrasonic motor.

FIG. 7 is an assembled sectional view showing an example of a conventional ultrasonic motor.

[Explanation of symbols]

 3 ... Fastening member 4 ... 1st piezoelectric element 5 ... 2nd piezoelectric element 6,7,8 ... Electrode plate 9,18 ... Resonator 11 ... Ultrasonic vibrator 13 ... Rotor 34 ... Permanent magnet 35 ... Coil 36 ... Conductor wire 44 ... Driving circuit 45, 50 ... Conducting wire 46 ... Amplifier 47 ... Signal separating circuit 48 ... Rectifying element 49 ... Rotation speed control circuit 51 ... Circuit board 52 ... External motor control circuit section 53 ... Motor internal circuit section

Claims (1)

[Claims] 1. A resonator for transmitting and expanding ultrasonic vibration, and an electro-mechanical energy conversion element which is arranged between these two resonators and generates ultrasonic vibration by applying a sinusoidal voltage. Fastening means for crimping and fixing the two resonators and the electro-mechanical energy conversion element to form an ultrasonic oscillator, a driven member which is moved by an elliptic motion generated on the end face of the resonator, and the driven member. A magnetic substance fixed to a member and magnetized; and a movement detecting means using a magnetic-electric energy conversion element for generating an electric signal by the interaction of the magnetic flux of the magnetic substance. Is superposed on a conducting wire to which the sine wave voltage is applied and transmitted, and a drive circuit for an ultrasonic motor.