JP2003033054A - Ultrasonic motor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the output torque of an ultrasonic motor device and stabilize the movement. SOLUTION: The ultrasonic motor device comprises a stator 1 which consists of a cylindrical piezoelectric element and generates rotary driving power at the end faces of the cylinder on both sides, a base stand 6 which supports the stator 1, the first rotor 21 which slidably pressure-contacts with the end face of the cylinder on one side and performs rotary motion by the rotary driving power, the second rotor 22 which slidably pressure-contacts with the end face of the cylinder on the opposite side and performs rotary motion by rotary driving power, and a pressurizing means which presses the first rotor 21 and the second rotors 22 against each end face of the cylinder of the stator 1. The pressurizing means consists of a spring member 8 interposed between the first rotor 21 and the second rotor 22 arranged apart in axial direction of the cylindrical stator 1.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an ultrasonic motor device. More specifically, the present invention relates to a rotor arrangement structure suitable for a stator having a cylindrical shape.

[0002]

2. Description of the Related Art Conventionally, ultrasonic motors have two types, a standing wave type motor and a traveling wave type motor, which are symmetrical excitation modes in which the center of gravity of the oscillator is fixed, and a disc or cylinder which is an oscillator is, for example, 4 There is known an electrostrictive revolution-type motor in which the center of gravity rotates and moves around the center by excitation in an asymmetric mode in which the amplitude is divided and the left and right amplitudes are reversed, and the outer circumference of the circle is eccentric like a hula hoop. Such an ultrasonic motor (hereinafter, also referred to as a piezo motor) applies a high-frequency AC voltage to a piezoelectric element serving as a stator to generate ultrasonic vibrations of about 20 kHz or more, thereby rotationally driving a rotor pressed against the stator. ing. This type of piezo motor has the advantages that it has a simple structure and is suitable for downsizing and weight reduction, and that high torque can be obtained even at low speed rotation and that driving noise is low and quiet. In particular, the latter electrostrictive revolution type motor generates a 3D revolution torque in which, in addition to the diameter and circumferential direction of the cylindrical revolution element, an axial mode is also coupled, as disclosed in Japanese Patent Laid-Open No. 10-272420. It has the feature that it can be used as a child

[0003]

When the cylindrical revolution element is used as the stator as described above, a rotational driving force is generated on both end faces thereof. On the other hand, the conventional rotor has an annular shape, and is pressed against one end surface of the cylindrical revolving rotor to take out revolving torque such as rotational motion. The end surface on the opposite side of the cylindrical revolution element was placed in an open state even though it similarly generated a rotational driving force. In such a structure, the rotational driving force generated by the stator is not sufficiently taken out as a driving torque, and further higher torque has been desired.

Further, in a conventional ultrasonic motor, an annular rotor is brought into pressure contact with an end surface of a cylindrical stator to extract driving torque such as rotational movement. Unless the rotor is brought into pressure contact with the cylindrical end surface of the stator, which is a sliding surface, with a proper pressure, torque and rotation speed cannot be obtained, and uneven rotation occurs. Conventionally, since the rotor is pressed against only one end face of the stator, the pressing force cannot always be made uniform and uniform, which has been a cause of unstable operation of the motor.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, it is an object of the present invention to increase the output torque of an ultrasonic motor device and stabilize its operation. The following measures have been taken to achieve this purpose. That is, the ultrasonic motor device according to the present invention comprises a stator that is composed of a cylindrical piezoelectric element and that generates rotational driving force on the cylindrical end faces on both sides, a base that supports the stator, and a cylinder end face on one side. A first rotor that is dynamically pressed to rotate by the rotational driving force; a second rotor that is slidably pressed against the opposite cylindrical end surface to rotate by the rotational driving force; The first rotor and the second rotor are composed of a pressurizing unit that presses the cylindrical end surface of the stator. Preferably, the first rotor and the second rotor are connected to each other and integrally rotate. Further, the pressurizing means is composed of a spring member interposed between a first rotor and a second rotor which are separately arranged in the axial direction of the cylindrical stator. In addition, the cylindrical end faces of both sides of the stator generate an orbital torque by electrostrictive orbital resonance, and the first rotor and the second rotor take out the electrostrictive orbital resonance torque as a direct rotation motion.

According to the present invention, the rotor is pressed against both cylindrical end surfaces of the stator. Vibrations generated on both cylindrical end surfaces of the stator are converted into rotational force by each rotor, and both rotors are integrally and rotatably connected. As a result, the output torque can be increased as compared with the conventional case. Further, a spring member such as a coil spring is inserted between a pair of rotors arranged on both end surfaces of the stator to pressurize each rotor to the stator. As a result, the pressure contact force of the rotor with respect to the stator can be made uniform and uniform, which leads to stabilization of the rotating operation.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic sectional view showing an embodiment of an ultrasonic motor device according to the present invention. As shown in the figure, the present ultrasonic motor device is an electrostrictive revolving rotor type motor including a 3D revolving torque generator disclosed in, for example, Japanese Unexamined Patent Publication No. 10-272420 mentioned above, and includes a stator 1 and a pair of rotors 21. , 22, a base 6 and a pressurizing means. The stator 1 is composed of a cylindrical piezoelectric element and generates a rotational driving force on the upper and lower cylindrical end surfaces. Stator 1
Are fixed to the base 6 with an adhesive 6a or the like. The adhesive 6a is for preventing the stator 1 from rotating and moving, and is preferably made of elastic silicone rubber or the like. If strongly fixed to the base 6, the rotational driving force of the stator 1 may be impaired. The radial position of the outer peripheral surface of the stator 1 is restricted by the positioning portion 6b provided on the base 6. In this state of positioning, the stator 1 is fixed to the base 6 by the adhesive 6a. A bottom plate 7 is attached to the bottom of the base 6 to support the motor from below.

The first rotor 21 is slidably pressed against the lower cylindrical end surface of the stator 1 to rotate by the rotational driving force of the stator 1. In the illustrated example, the first rotor 21 is made of a cylindrical metal member or the like, is arranged concentrically with the cylindrical axis Z of the stator 1, and performs a rotational movement about the cylindrical axis Z. More specifically, the first rotor 21
Has a cylindrical shape with a flange portion, and is in contact with the lower end surface of the stator 1 on the upper surface of the flange portion. On the other hand, the second rotor 22 slidably presses against the upper cylindrical end surface of the stator 1 and performs rotational movement by the rotational driving force of the stator 1. In the illustrated example, the second rotor 22 is made of an annular metal member or the like, is arranged concentrically with the cylindrical axis Z of the stator 1, and performs a rotational motion about the cylindrical axis Z.

The first rotor 21 and the second rotor 22 are connected to each other and integrally rotate. As a result, the output torque of the ultrasonic motor device can be increased. Specifically, the key member 26 is formed on the upper end of the cylinder of the first rotor 21. On the other hand, a key groove 28 corresponding to the key member 26 is formed on the inner peripheral portion of the second rotor 22. First
The key member 26 on the side of the rotor 21 and the key groove 28 on the side of the second rotor 22 are connected to each other, and the two rotors 21 and 22 integrally rotate about the cylindrical axis Z.

The pressurizing means presses the first rotor 21 and the second rotor 22 against the lower and upper end surfaces of the stator 1. In the present embodiment, this pressurizing means is composed of a spring member 8 such as a coil spring, and is interposed between the first rotor 21 and the second rotor 22 which are arranged separately in the axial direction of the cylindrical stator 1. The spring member 8 acts so that the pair of rotors 21 and 22 pull each other. By this pulling force,
The first rotor 21 and the second rotor 22 are uniformly and uniformly pressed against the corresponding cylindrical end faces of the stator 1. As a result, between the first rotor 21 and the stator 1 and the second rotor 21
The frictional force generated between the rotor 22 and the stator 1 becomes uniform and uniform, which leads to stabilization of the operation of the ultrasonic motor device.

The ultrasonic motor shown in FIG. 1 is used as a power source for a lens driving device for a camera, and the drawing includes a lens barrel 3 of the camera driven by the ultrasonic motor. The lens barrel 3 is equipped with lenses 33 and 34,
Moreover, it is attached to the base 6 so as to be linearly displaceable in the optical axis Z direction of the lens. The optical axis Z of the lens and the stator 1
The cylindrical axes Z of are coincident with each other. A stopper 32 is formed on the lens barrel 3 and engages with a guide shaft 40 planted on the base 6. The lens barrel 3 is a stopper 32
The rotation is restricted by and the linear displacement is performed along the guide shaft 40 in the optical axis Z direction. The stopper 32 engaged with the guide shaft 40 has a lens barrel 3
The spring 41 for backlash is attached.

Here, the first rotor 21 has a cylindrical shape as described above, and the helicoid gear 25 is formed on the inner peripheral surface thereof. A helicoid gear 35 is also formed on the outer peripheral surface of the lens barrel 3. Helicoid gear 25 on the first rotor 21 side and helicoid gear 35 on the lens barrel 3 side
Are engaged with each other. When the first rotor 21 rotates,
The lens barrel 3 also tries to rotate due to the engagement of the helicoid gear described above, but since the rotational displacement is restricted by the stopper 32, the lens barrel 3 is linearly displaced along the guide shaft 40 in the optical axis Z direction. At this time, the second rotor 22 is also the first
Since it is connected to the rotor 21, the rotational movement generated in the second rotor 22 is also converted into the linear movement of the lens barrel 3 via the first rotor 21. Such an optical axis Z of the lens barrel 3
The linear displacement along the direction is used for zooming and focusing of the camera.

FIG. 2 is a schematic perspective view showing the entire structure of the ultrasonic motor (piezo motor) shown in FIG. As shown in the figure, the piezo motor is composed of a cylindrical stator 1, a first rotor 21 pressed against the rear end thereof, and a second rotor 22 pressed against the front end of the stator 1 as well. Although not shown, the first rotor 21 and the second rotor 22 are connected to each other inside the stator 1. Electrodes 11, 12, 13, and 14 are formed on the outer peripheral surface of the cylindrical stator 1. Although not shown, electrodes are also formed on the inner peripheral surface of the cylinder. The electrodes formed on the outer peripheral surface of the cylinder are divided into four, and AC driving voltages A, B, AX, and BX having different phases are applied to the electrodes. The A-phase voltage and the B-phase voltage are 90 degrees out of phase with each other. Also, A phase voltage and A
The X-phase voltages are 180 degrees out of phase. In other words,
The A phase and the AX phase have opposite polarities. Similarly, the B phase and the BX phase have opposite polarities.

FIG. 3 is a schematic cross-sectional view of the stator shown in FIG. As shown in the figure, an electrode 10 for applying a reference potential is formed on the entire inner peripheral surface of the cylindrical stator 1 made of a piezoelectric element such as ceramics. Four-divided driving electrodes 11 to 14 are formed on the outer peripheral surface of the cylinder. These four-divided electrodes 11 to 14 have four-phase AC voltages A whose phases are mutually shifted by 90 degrees,
B, AX and BX are applied.

The operation of the piezoelectric motor shown in FIGS. 2 and 3 will be described with reference to FIG. In the piezo motor, the ultrasonic vibration that serves as a power source has a constant resonance frequency, so that the current has a substantially constant value. The resonator has a high Q and the rising of the vibration amplitude is considered to be within one cycle, and can be regarded as a non-inertial mechanism. The current changes only within the range affected by the load inertia. Although various configurations of the piezo motor having such characteristics have been developed, the electrostrictive revolution type is particularly effective. The electrostrictive revolution type uses a resonator that can directly excite uniform torque over the entire peripheral surface, instead of changing vibration into torque as in the conventional case. There are two types of conventional ultrasonic transducers, a standing wave type and a traveling wave type, but both can be excited only in a symmetric mode with a fixed center of gravity. On the contrary, when the cylinder is excited in a mode in which the left and right expansions are reversed, the center of gravity vibrates away from the center. When this asymmetrical excitation is performed, a cylindrical resonance mode which cannot be observed by the conventional symmetrical excitation is obtained. Therefore, when the electrode of the stator cylinder is divided into, for example, four parts and excited by rotating electric fields having different phases by 90 degrees, resonance of a mode in which the center of gravity rotates around the center is observed, as shown in FIG. At this time, the outer circumference of the circle keeps its original shape,
Since it is eccentric like a hula hoop, the oscillator revolves around the revolution. In the electrostrictive revolution rotor having such a configuration, the direct rotation mode is excited and a strong revolution torque is uniformly generated on the peripheral surface.
At the same time, a strong torque in the direction perpendicular to the diameter is generated on the upper and lower end surfaces of the cylindrical stator. This revolution torque is taken out as the rotation motion of the pair of rotors that are directly in pressure contact with the stator.

FIG. 5 is a waveform diagram of A-phase, B-phase, AX-phase and BX-phase voltages applied to each of the four divided stator electrodes. As shown in the figure, the B phase is shifted by 90 degrees, the AX phase is shifted by 180 degrees, and the BX phase is shifted by 270 degrees with respect to the A phase. In this way, a rotating electric field is formed by applying alternating voltage with different phases by 90 degrees to the stator,
In response to this, the stator directly excites the revolution mode.

Finally, FIG. 6 shows a drive circuit for the piezo motor. As shown, a pair of drive signals A and AX
Is applied to a pair of electrodes of the stator 1 facing each other via the H bridge A. Similarly, another pair of signals B, B
X is also applied to the other pair of stator electrodes facing each other via the H bridge B. Each H-bridge is a driver circuit for supplying a sufficient output current to the stator electrode in response to an input signal.

[0018]

As described above, according to the present invention, in the ultrasonic motor device using the cylindrical stator, the pair of rotors are in pressure contact with the upper and lower end surfaces of the stator. Since the pair of rotors are connected to each other and integrally rotate, the output torque of the ultrasonic motor can be increased as compared with the conventional case. In addition, a spring member that generates tension is interposed between a pair of rotors that are separately arranged in the axial direction of the cylindrical stator, and each rotor is pressed against the end surface of the corresponding stator. Thereby, the operation of the ultrasonic motor can be stabilized.

[Brief description of drawings]

FIG. 1 is a schematic partial cross-sectional view showing an embodiment of an ultrasonic motor device according to the present invention.

FIG. 2 is a schematic perspective view showing an appearance of an ultrasonic motor device according to the present invention.

FIG. 3 is a cross-sectional view of the ultrasonic motor device according to the present invention.

FIG. 4 is a schematic diagram for explaining the operation of the ultrasonic motor device according to the present invention and the generation of revolution torque.

FIG. 5 is a waveform diagram for explaining the operation of the ultrasonic motor device according to the present invention.

FIG. 6 is a drive circuit diagram of an ultrasonic motor device according to the present invention.

[Explanation of symbols]

1 ... Stator, 21 ... First rotor, 22 ...
2nd rotor, 6 ... base, 8 ... spring member,

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kiyoji Hosono             2-18-10 Shimura, Itabashi-ku, Tokyo Nidec             Sankopal Co., Ltd. (72) Inventor Kiyoshi Toma             2-18-10 Shimura, Itabashi-ku, Tokyo Nidec             Sankopal Co., Ltd. F-term (reference) 2H044 BE05 BE07 BE20                 5H680 AA01 AA19 BB13 BB16 BB19                       BC01 CC02 DD15 DD23 DD53                       DD57 DD59 DD66 DD74 DD85                       DD88 DD98 EE07 EE12 EE20                       FF08 FF33 FF38

Claims (4)

[Claims] 1. A stator comprising a cylindrical piezoelectric element for generating a rotational driving force on both end faces of a cylinder, a base for supporting the stator, and a cylinder end face on one side slidably press-contacted to each other. A first rotor that makes a rotational movement by a rotational driving force, a second rotor that makes a rotational movement by a rotational driving force by slidably contacting the opposite cylindrical end surface, a first rotor and a second rotor An ultrasonic motor device comprising a pressurizing means for pressing the rotor against each cylindrical end surface of the stator. 2. The ultrasonic motor device according to claim 1, wherein the first rotor and the second rotor are connected to each other and integrally rotate. 3. The ultrasonic motor device according to claim 1, wherein the pressurizing means comprises a spring member interposed between a first rotor and a second rotor, which are separately arranged in an axial direction of a cylindrical stator. . 4. The stator generates revolving torque due to electrostrictive revolution resonance at both end faces of the cylinder, and the first rotor and the second rotor take out the electrostrictive revolution resonance torque as direct rotation motion. The ultrasonic wave device described.