JPH0744856B2 - Ultrasonic motor - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ultrasonic motor used for OA equipment, toys, etc., and more particularly to a small ultrasonic motor having a small rotor diameter.

[Prior Art] An ultrasonic motor is capable of obtaining a high torque at a low rotation and having a stop holding force as compared with a conventional electromagnetic motor
It has advantages such as low electromagnetic noise, and is used for autofocus of cameras and power motors for automobiles.

20 and 21 are schematic views showing the structure of a conventional ultrasonic motor, which is a metal plate provided with a ring-shaped comb tooth-shaped protrusion.
A disc-shaped rotor 104 is pressed onto a stator having a structure in which two piezoelectric ceramic discs 102 and 103 are adhered to the back side of the surface where the protrusions are formed. The piezoelectric ceramic discs 102 and 103 have polarization directions that are evenly divided and opposite to each other, and these two piezoelectric ceramic plates are bonded to each other with a shift of half the division angle.

[Problems to be Solved by the Invention] As can be seen from FIG. 20, in the conventional ultrasonic motor,
Since the ultrasonic vibration of the stator is transmitted to the rotor in a plane, it is necessary to increase the diameters of the stator and the rotor in order to increase the driving torque. Therefore, the practical minimum diameter of the conventional ultrasonic motor was limited to 20 to 30 mm.

Further, as can be seen from FIG. 20, in the conventional ultrasonic motor, there are drawbacks that the stator is composed of many parts and thus the characteristic variations are small and the manufacturing cost of the motor is high. .

Then, the technical subject of this invention is providing the small ultrasonic motor which reduced the diameter of the rotor, and is providing the ultrasonic motor whose diameter of a rotor is 20 mm or less.

Another technical object of the present invention is to provide an ultrasonic motor having a small number of components and a low manufacturing cost.

[Means for Solving the Problems] According to the present invention, a pair of rotors can be rotated with respect to the vibrator at the both ends of a pipe-shaped piezoelectric elliptical motion oscillator that performs an elliptical motion in which both ends include a circle. In the ultrasonic motor arranged in pressure contact, the vibrator has a pipe-shaped bolt having a threaded outer periphery through a hollow portion of a piezoelectric ceramic cylinder, and a screw of the bolt is attached to both ends of the vibrator. There is obtained an ultrasonic motor characterized by being fixed by tightening a ring-shaped metal threaded on the inner peripheral part for screwing with.

According to the present invention, in the ultrasonic motor in which a pair of rotors are arranged in pressure contact with the vibrators at the both ends of the pipe-shaped piezoelectric elliptic motion vibrators that perform elliptic motions including circular ends, The vibrator is an ultrasonic motor characterized in that a ring-shaped friction member made of a material selected from the group including metal, ceramics, and synthetic resin is joined to both ends of a piezoelectric ceramic hollow cylinder.

Further, according to the present invention, in any one of the ultrasonic motors, the rotor includes a shaft having a threaded end that penetrates the hollow portion of the vibrator, and a pressure screw that is screwed into both ends of the shaft. As a result, an ultrasonic motor characterized by being pressed against both ends of the piezoelectric vibrator is obtained.

Further, according to the present invention, in any one of the ultrasonic motors described above, the vibrator is disposed at a position divided into four along the circumference of the outer peripheral surface of the piezoelectric ceramic hollow cylinder, in the longitudinal direction of the piezoelectric ceramic hollow cylinder. 4 divided electrodes are provided in parallel with each other, the divided electrodes facing each other of the divided electrodes are electrically connected, and a DC voltage is applied between the respective electrodes, so that the piezoelectric ceramic cylinder is perpendicular to the longitudinal direction. An ultrasonic motor characterized by being polarized is obtained.

[Operation] In the ultrasonic motor of the present invention, a DC voltage is applied to the piezoelectric elliptical motion oscillator to polarize it, and a first AC voltage equal to the resonance frequency of the oscillator is applied to a predetermined portion. Then, bending vibration in a plane including the central axis is generated.

Similarly, a second AC voltage having a frequency equal to the resonance frequency of the piezoelectric elliptical motion oscillator is applied to a portion different from the above, and bending in a plane including the central axis intersects the bending vibration direction. Make it vibrate. The phases of the flexural vibrations in these two directions are shifted (preferably 90 °), specifically, the phases of the first and second AC voltages are shifted (preferably
90 °) makes it possible to excite elliptical motion including circular motion at both ends of the piezoelectric elliptical motion oscillator. The elliptical motion including the circle of the end face is provided at the end, and is converted into rotational motion by the rotor arranged in pressure contact with the end of the piezoelectric elliptical motion oscillator.

EXAMPLES Examples of the present invention will be described in detail below with reference to the drawings.

A first embodiment of the present invention will be described.

FIG. 1 is a perspective view showing a structural example of an ultrasonic motor according to the first embodiment of the present invention. In this figure, the ultrasonic motor is provided with a pipe-shaped piezoelectric elliptical motion oscillator 20 whose vibration nodes are supported by support rings 21 and 21 ', and arranged at both ends of the pipe-shaped piezoelectric elliptical motion oscillator 20. It also has cup-shaped rotors 22 and 22 'and screws 24 and 24' for pressing the cup-shaped rotors 22 and 22 'under constant pressure. This screw 24,2
4'is screwed to a shaft (not shown) passing through the pipe-shaped piezoelectric elliptical motion oscillator 20.

FIG. 2 is a schematic diagram showing the structure of the piezoelectric elliptical motion oscillator according to the first embodiment of the present invention. In this figure, the split electrodes 11, 1 are arranged parallel to the length direction of the piezoelectric ceramic hollow cylinder 10.
2,13,14 are applied.

FIG. 3 is a cross-sectional view of the piezoelectric ceramic hollow cylinder 10 shown in FIG. 2. In FIG. 3 (a), the broken line arrow indicates that the divided electrodes 11 and 13 are electrically connected by a connecting line 15 and a + terminal is provided. The divided electrodes 12 and 14 are electrically connected by a connecting line 16 to form one terminal, and a polarization direction is shown when a DC voltage is applied between the two terminals to perform polarization processing. The piezoelectric ceramic hollow cylinder 10 includes divided electrodes 11 to polarized electrodes 12 and 14.
To the polarization electrodes 12 and 11 from the divided electrode 13.

FIG. 3 (b) is a diagram showing the operating principle of the piezoelectric ceramic hollow cylinder 10 polarized as shown in FIG. 3 (a).
In this figure, the divided electrodes 11 and 12 adjacent to each other are connected by a connecting line 17 to form a + terminal, and the pair of adjacent divided electrodes 13 and 14 connected to each other via a connecting line 18 are used as a-terminal to apply a DC voltage. The state of strain generated in the cross-sectional direction of the piezoelectric ceramic hollow cylinder in the case of is shown. In FIG. 3B, the electric field is divided electrode 11 and divided electrode 14 indicated by solid arrows.
And between the divided electrodes 12 and 13, the direction of polarization and the direction of the electric field between the divided electrode 11 and the divided electrode 14 are the same direction, the elongation strain in the circumferential direction occurs, Split electrode
Between 12 and 13, the direction of polarization and the direction of electric field are opposite to each other, and a contraction strain in the circumferential direction occurs. As a result,
In FIG. 3 (b), the piezoelectric ceramic hollow cylinder is
Bend to bulge downward in the length direction. When the direction of the applied voltage is reversed, the bending direction is also reversed.

FIG. 4 is an explanatory diagram of a vibrating state when an AC voltage is applied to the piezoelectric ceramic hollow cylinder that is polarized as shown in FIG. In FIG. 4 (a), split electrodes 11,1
When a first AC voltage having a first phase which is equal to the resonance frequency of the flexural vibration of the piezoelectric ceramic hollow cylinder is applied between the four electrodes and between the divided electrodes 12 and 13, the piezoelectric ceramic hollow cylinder 10 is moved as shown in FIG. ) 1st in the direction of arrow 19
Generates bending vibration. In FIG. 4 (b), similarly, a second alternating current having a second phase which is equal to the resonance frequency of the bending vibration of the piezoelectric ceramic hollow cylinder between the divided electrodes 11 and 12 and between the divided electrodes 14 and 13. When a voltage is applied, the piezoelectric ceramic hollow cylinder generates a second bending vibration in a direction perpendicular to the direction of the arrow shown in FIG. 4 (a).

Therefore, by shifting the phases of the first and second bending vibrations in the two directions shown above, specifically, the respective first vibrations
By shifting the first and second phases of the AC drive voltage for exciting the second and second bending vibrations, a circular motion or an ellipse as shown in FIG. You can excite the movement.

FIG. 5 to FIG. 7 are a perspective view and a structural schematic view of each part used for explaining the structure of the ultrasonic motor according to the first embodiment of the present invention. In FIG. 5, the nodes of vibration of bending vibration of the piezoelectric elliptical motion oscillator 20 are supported by support rings 21, 21 'having the same shape.

FIG. 6 is a perspective view showing a structural example of the cup-shaped rotors 22, 22 'used in the ultrasonic motor according to the first embodiment of the present invention.

FIG. 7 is a perspective view showing an example of a shaft 23 for press-contacting the cup-shaped rotors 22, 22 'of the ultrasonic motor according to the first embodiment of the present invention. In this figure, at both ends of the shaft 23,
Screws are provided. Support ring 2 shown in FIG.
The shaft 23 shown in FIG. 7 is inserted into the hollow portion of the pipe-shaped piezoelectric elliptical motion oscillator 20 provided with 1, 21 ′, and both ends of this pipe-shaped piezoelectric elliptical motion oscillator 20 are shown in FIG. When the cup-shaped rotors 22 and 22 'are mounted, the screws 24 and 24 are respectively screwed onto the shaft 23, and both ends of the pipe-shaped piezoelectric elliptical motion oscillator 20 are pressed with a constant pressure, the rotors 22 and 22' are The rotational force is transmitted to the cup-shaped rotors 22 and 22 'to complete the ultrasonic motor 1 rotating together with the shaft 23.

A second embodiment of the present invention will be described.

FIG. 8 is a perspective view showing a configuration example of an ultrasonic motor according to the second embodiment of the present invention. In this figure, the ultrasonic motor 2 includes a pipe-shaped piezoelectric elliptical motion oscillator 40 whose vibration nodes are supported by support rings 41 and 41 ', and a pipe-shaped piezoelectric elliptical motion oscillator 40. The cup-shaped rotors 42, 42 'and the screws 44, 44 for pressing the cup-shaped rotors 42, 42' with a constant pressure. This screw is screwed onto a shaft (not shown) passing through the pipe-shaped piezoelectric elliptical motion oscillator 40.

FIG. 10 is a perspective view showing a pipe-shaped piezoelectric elliptical motion oscillator 40 of the ultrasonic motor 2 according to the second embodiment of the present invention. The pipe-shaped piezoelectric elliptical motion oscillator 40 can be operated in the same manner as the pipe-shaped piezoelectric elliptical motion oscillator 20 according to the first embodiment.

FIG. 9 is a perspective view of components constituting the piezoelectric elliptical motion oscillator 40 of the ultrasonic motor shown in FIG. The piezoelectric ceramic hollow cylinder 10 shown in FIG.
The pipe-shaped bolt 31 shown in FIG. 7B is penetrated, and the metal rings 32 and 32 'shown in FIG. It is tightened and fixed by being screwed into the part,
The piezoelectric elliptical motion oscillator 40 shown in FIG. 10 is completed.

The pipe-shaped bolt 31 is threaded at least in the vicinity of both ends thereof and loosely penetrates into the hollow portion of the piezoelectric ceramic hollow cylinder 10.

11 to 13 are a perspective view and a schematic view of the structure of each part used for explaining the structure of the ultrasonic motor according to the second embodiment of the present invention. In FIG. 11, the nodes of vibration of the piezoelectric elliptical motion oscillator shown in FIG. 10 are supported by support rings 41, 41 ′ made of a ring-shaped frame member.

FIG. 12 is a perspective view showing a structural example of the cup-shaped rotors 42, 42 'used in the ultrasonic motor according to the second embodiment of the present invention.

FIG. 13 is a perspective view showing an example of a shaft for press-contacting the cup-shaped rotors 42, 42 'of the ultrasonic motor according to the second embodiment of the present invention. In this figure, screws are provided at both ends of the shaft 43.

The shaft 43 shown in FIG. 13 is inserted into the hollow portion of the pipe-shaped piezoelectric elliptical motion oscillator 40 shown in FIG. 11, and both ends of this pipe-shaped piezoelectric elliptical motion oscillator 40 are shown in FIG. When the cup-shaped rotors 42, 42 'are mounted, the screws 44, 44 are respectively screwed onto the shaft 43, and both ends of the pipe-shaped piezoelectric elliptical motion oscillator 20 are pressed against each other with a constant pressure, the rotors 42, 42' are attached. The rotational force is transmitted, and the cup-shaped rotors 42, 42 'complete an ultrasonic motor that rotates together with the shaft 43.

In FIG. 8, the shape of the cup-shaped rotors 44, 44 'is such that the diameter of the bottom is smaller than the diameter of the opening, and the tapered portion inside the cup is brought into contact with the pipe-shaped piezoelectric elliptical motion oscillator which is the stator. And the two rotors are
Since the spring is pressed against this stator, the rotor is automatically positioned and rotates stably without using bearings.

A third embodiment of the present invention will be described.

FIG. 14 is a perspective view showing a structural example of an ultrasonic motor according to the third embodiment of the present invention. In this figure, the ultrasonic motor 3 is provided with a pipe-shaped piezoelectric elliptical motion oscillator 60 in which vibration nodes are supported by support rings 61 and 61 ', and arranged at both ends of the pipe-shaped piezoelectric elliptical motion oscillator 60. Cup-shaped rotor
62, 62 'and screws 64, 64 for pressing the cup-shaped rotors 62, 62' under constant pressure. The screws 64, 64 'are screwed onto a shaft (not shown) passing through the cavity of the pipe-shaped piezoelectric elliptical motion oscillator 60.

FIG. 15 shows a piezoelectric elliptical motion oscillator 60 which constitutes an ultrasonic motor according to the third embodiment of the present invention. The piezoelectric elliptical motion oscillator 60 performs elliptical motion vibration like the piezoelectric elliptical motion oscillator according to the first embodiment.

FIG. 16 is an inclined view of the components that make up the piezoelectric elliptical motion oscillator 60 shown in FIG. On both sides of the piezoelectric ceramic hollow cylinder 10 shown in FIG. 16 (a), the metal rings 52, 52 'shown in FIG. 16 (b) are fastened and fixed.

17 to 19 are a perspective view and a schematic view of the structure of each part used for explaining the structure of the ultrasonic motor according to the second embodiment of the present invention. In FIG. 17, the nodes of vibration of flexural vibration of the piezoelectric elliptic motion oscillator shown in FIG. 10 are supported by support rings 61, 61 ′ made of a ring-shaped support frame.

FIG. 18 is a perspective view showing a structural example of the cup-shaped rotors 62, 62 'used in the ultrasonic motor according to the embodiment of FIG. 3 of the present invention.

FIG. 19 is a perspective view showing an example of a shaft 63 for press-contacting the cup-shaped rotors 62, 62 'of the ultrasonic motor according to the third embodiment of the present invention. In this figure, both ends of the shaft 63 are
It is threaded.

The shaft 63 shown in FIG. 19 is inserted into the hollow portion of the pipe-shaped piezoelectric elliptical motion oscillator 60 shown in FIG. 17, and both ends of this pipe-shaped piezoelectric elliptical motion oscillator 60 are shown in FIG. When the cup-shaped rotors 62, 62 'are mounted, the screws 64, 64' are screwed onto the shaft 43, and both ends of the pipe-shaped piezoelectric elliptical motion oscillator 20 are pressed with a constant pressure, the rotors 62, 62 'are attached. The rotational force is transmitted to the cup-shaped rotors 62, 62 ', and the ultrasonic motor that rotates together with the shaft 63 is completed.

In Fig. 14, the shape of the cup-shaped rotors 64, 64 'is such that the diameter of the bottom is smaller than the diameter of the opening and the tapered portion inside the cup is brought into contact with the pipe-shaped piezoelectric elliptical motion oscillator that is the stator. And the two rotors are
Since the spring is pressed against the stator, the rotor is automatically positioned and rotates stably without using bearings.

[Effects of the Invention] As described above, in the ultrasonic motor of the present invention,
Since the shape of the piezoelectric elliptical motion oscillator for generating the driving force is simple and the two vibration modes for generating the elliptical vibration including the circle are the same bending mode, the structure is simple and the variation of the vibration characteristics is small. A small number of ultrasonic motors can be obtained.

Further, in the ultrasonic motor of the present invention, the number of parts for forming the pipe-shaped piezoelectric elliptical motion oscillator, which is the stator, is smaller than that of the conventional ultrasonic motor, and an ultrasonic motor without a bearing can be manufactured. It is also advantageous in terms of cost.

Further, in the present invention, since the pipe-shaped piezoelectric elliptical motion oscillator is used as the piezoelectric elliptical motion oscillator, the rotor diameter is set as the rotor diameter for applications where the torque may be small.
It is possible to obtain a small motor of 10 mm or less.

[Brief description of drawings]

FIG. 1 is a perspective view showing the configuration of an ultrasonic motor according to the first embodiment of the present invention, and FIG. 2 is a piezoelectric elliptical motion oscillator used in the ultrasonic motor according to the first embodiment of the present invention. 3A and 3B are schematic views showing the structure, FIG. 3A and FIG. 3B are sectional views for explaining the operation principle of the piezoelectric ceramic hollow cylinder shown in FIG. 2, and FIG. 4A and FIG. FIG. 5 is a perspective view for explaining bending vibration of a piezoelectric ceramic hollow cylinder, and FIG. 5 is a piezoelectric elliptical motion oscillator and ring-shaped support used for explaining the structure of an ultrasonic motor according to a first embodiment of the present invention. FIG. 6 is a perspective view showing a frame, FIG. 6 is a perspective view showing a structural example of a cup-shaped rotor used in the ultrasonic motor according to the first embodiment of the present invention, and FIG. 7 is a first embodiment of the present invention. A perspective view showing an example of a shaft for press-contacting a cup-shaped rotor of the ultrasonic motor. FIG. 8 is a perspective view showing a configuration example of an ultrasonic motor according to a second embodiment of the present invention. FIG. 9 is a perspective view of components constituting the piezoelectric elliptical motion oscillator used in the ultrasonic motor according to the second embodiment of the present invention shown in FIG. FIG. 10 is a perspective view showing a piezoelectric elliptical motion oscillator of an ultrasonic motor according to the second embodiment of the present invention. First
FIG. 11 to FIG. 13 are perspective views and schematic diagrams of the respective parts for explaining the structure of the ultrasonic motor according to the second embodiment of the present invention, and FIG. 14 is the third embodiment of the present invention. FIG. 15 is a perspective view showing the configuration of such an ultrasonic motor, FIG. 15 is a perspective view showing a piezoelectric elliptical motion oscillator according to a third embodiment of the present invention, and FIG.
FIGS. 17 to 19 are perspective views of the components constituting the piezoelectric elliptical motion oscillator shown in the drawings, and FIGS. 17 to 19 are perspective views of the components for explaining the structure of the ultrasonic motor according to the third embodiment of the present invention. FIG. 20 is a schematic view of the structure, and FIGS. 20 and 21 are schematic views showing the structure of an ultrasonic motor according to a conventional example. In the figure, 10 is a piezoelectric ceramic hollow cylinder, 11, 12, 13, and 14 are divided electrodes, 15, 16, 17, and 18 are connection lines, 19 is an arrow, 20 is a pipe-shaped piezoelectric elliptical motion oscillator, and 21, 21 'are Support ring, 22,22 '
Is a cup-shaped rotor, 23 is a shaft, 24 and 24 'are pressure welding screws, 3
1 is a pipe-shaped bolt, 32, 32 'is a metal ring, 40 is a pipe-shaped piezoelectric elliptical motion oscillator, 41, 41' is a support ring, 42, 42 '
Is a cup-shaped rotor, 43 is a shaft, 44 and 44 'are pressure welding screws, 5
2,52 'metal ring, 60 is a piezoelectric piezoelectric elliptical motion oscillator,
61, 61 'is a ring-shaped support frame, 62, 62' is a cup-shaped rotor, 63 is a shaft, 64, 64 'are screws, 101 is a metal cylinder, 102, 103
Is a piezoelectric ceramic disk, and 104 is a disk-shaped rotor.

Front page continuation (56) References JP-A-63-224681 (JP, A) JP-A-63-240380 (JP, A) Proc. October 3, 63, P. 827-828 (Fig. 4)

Claims (4)

[Claims] 1. An ultrasonic motor in which a pair of rotors are arranged in pressure contact with the vibrators at the opposite ends of a pipe-shaped piezoelectric elliptical motion vibrator that makes an elliptical motion including circles at both ends. The child penetrates the hollow portion of the piezoelectric ceramic cylinder with a pipe-shaped bolt having a threaded outer periphery, and is attached to both ends of the vibrator at an inner portion for screwing with the screw of the bolt. An ultrasonic motor characterized by being fixed by tightening a threaded ring-shaped metal. 2. An ultrasonic motor in which a pair of rotors are arranged in pressure contact with the oscillators at the opposite ends of a pipe-shaped piezoelectric elliptical oscillator that performs an elliptic motion including circular ends. The child is an ultrasonic motor characterized in that a ring-shaped friction member made of a material selected from the group including metal, ceramics, and synthetic resin is joined to both ends of a piezoelectric ceramic hollow cylinder. 3. The ultrasonic motor according to claim 1, wherein the rotor has a threaded shaft at both ends which penetrates the hollow portion of the vibrator, and a pressure contact screw screwed to both ends of the shaft. An ultrasonic motor, wherein the piezoelectric vibrator is pressed against both ends of the piezoelectric vibrator. 4. The ultrasonic motor according to any one of claims 1 to 3, wherein the vibrator is formed by dividing the piezoelectric ceramic hollow into four positions along a circumference of an outer peripheral surface of the piezoelectric ceramic hollow cylinder. Four divided electrodes are provided in parallel to the length direction of the cylinder, the divided electrodes facing each other of the divided electrodes are electrically connected, and a DC voltage is applied between the respective electrodes, so that the piezoelectric ceramic cylinder is elongated. An ultrasonic motor characterized by being polarized at right angles to the vertical direction.