JP2002165470A - Ultrasonic motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance durability of an ultrasonic motor, while increasing the drive torque. SOLUTION: A rotor R including an output shaft 1 is supported rotatably for a stator S; a plurality of vibration bodies 3 which are driven, with a plurality of excitation elements 2 being provided within a space formed by the stator S and the rotor R; the end part 3A of this vibration body 3 is formed into spherical surface; and a traction oil T is provided between the end part 3A of this vibration body 3 and the contact surface 10 of the rotor 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor for supporting a rotor rotatably around an axis with respect to a stator, and a plurality of rings in a ring shape centered on the axis with respect to a support surface of the stator facing the rotor. A plurality of vibrators driven by the excitation elements are arranged, and biasing means for pressing the vibrators against the pressure contact surface of the rotor is provided. Each of the vibration elements is driven by driving each of the excitation elements according to a set rule. The present invention relates to an ultrasonic motor configured to generate a traveling wave in a body and apply a rotating force to a rotor by the traveling wave.

[0002]

2. Description of the Related Art In a conventional ultrasonic motor, a vibrating body is pressed against a pressure contact surface of a rotor by urging a stator and a rotor in an approaching direction by urging means such as a spring. The rotor is rotated by driving it in accordance with the rules to generate a traveling wave on the vibrating body and applying the traveling wave to the pressure contact surface of the rotor. This ultrasonic motor has a good surface in that it generates a high-torque torque even at low-speed rotation, and a high holding force (braking force) is obtained when the rotor is pressed against the stator when stopped. Therefore, in the conventional ultrasonic motor, a clean state is maintained between the vibrating body and the pressure contact surface in order to reliably apply a rotational force from the vibrating body to the rotor.

[0003]

However, in the conventional ultrasonic motor, the vibrating body and the pressure contact surface of the rotor are in direct contact with each other with a strong force, and the vibrating body vibrates to generate a rotational force on the rotor. Because of this structure, wear is easily generated on the pressure contact surfaces of the vibrating body and the rotor, and the durability is low. In addition, since the ultrasonic motor obtains a high torque even at a low speed rotation as described above, it is desired to further enhance its effectiveness, and it is necessary to use a structure in which the vibrating body is more strongly pressed against the rotor. It is also the current situation.

An object of the present invention is to rationally construct an ultrasonic motor capable of increasing driving torque and durability at the same time.

[0005]

The features, functions and effects of the ultrasonic motor according to the first aspect of the present invention are as follows. [Features] A plurality of excitation elements driven by a plurality of excitation elements in a ring shape around the axis with respect to a stator supporting surface opposed to the rotor while supporting the rotor rotatably about the axis with respect to the stator. Arranging the vibrating body, and comprising biasing means for pressing the vibrating body against the pressure contact surface of the rotor, generating a traveling wave in each vibrating body by driving each of the excitation elements according to a set rule, In an ultrasonic motor configured to apply a rotational force to the rotor by the traveling wave, traction oil is interposed at a contact portion between the vibrator and the rotor.

According to the above feature, traction oil is interposed between the vibrating member and the pressure contact surface of the rotor, so that the vibrating member does not directly contact with the pressure contact surface of the rotor. When the vibrating body is displaced by the vibration of the body toward the pressure contact surface of the rotor, a high pressure is applied to the traction oil, and a shear force is generated in the traction oil interposed in the area where the pressure was applied. Then, a rotational force is applied to the rotor from the vibrator by the shearing force. As a result, not only is the pressure contact force between the vibrating body and the pressure contact surface of the rotor increased to obtain a high torque, but also because the vibrating body and the rotor do not directly contact each other, their wear is suppressed and an ultrasonic motor with high durability is provided. It was composed. In particular, the one in which the traction oil is interposed between the vibrating body and the rotor can increase the urging force, so that a higher torque can be obtained at low speed rotation.

The features, functions and effects of the ultrasonic motor according to the second aspect of the present invention are as follows. (Features) In the ultrasonic motor according to claim 1, a storage space for the traction oil is formed between the stator and the rotor, and the traction oil stored in the storage space is combined with the vibrator when the excitation element is driven. The point is that an oil replenishing means for sending the oil to a contact portion with the rotor is provided.

According to the above-mentioned features, when the excitation element is driven, the oil replenishing means sends traction oil to the contact area between the vibrating body and the rotor, so that the traction is provided at the contact area between the vibrating body and the rotor. Not only does the amount of oil never run short, but also the traction oil can be circulated, so that it is possible to avoid deterioration of the traction oil and to avoid a local temperature rise. As a result, the durability is further improved,
It has become possible to maintain high performance for a long period of time by reducing the frequency of traction oil replacement.

The features, functions and effects of the ultrasonic motor according to claim 3 of the present invention are as follows. (Features) In the ultrasonic motor according to claim 2, the oil supply means is orthogonal to the vibration direction of the vibrating body so as to send traction oil to a contact portion between the vibrating body and the rotor when the vibrating body is vibrated, or The point is that it is composed of a plurality of feed surfaces formed on the outer surface of the vibrator in a substantially orthogonal posture.

According to the above feature, the traction oil sent from the feed surface during the vibration operation of the vibrator is sent along the outer surface of the vibrator toward the contact surface between the vibrator and the rotor. Become. As a result, traction oil can be supplied between the rotor and the vibrator without using a pump or the like.

The features, functions and effects of the ultrasonic motor according to claim 4 of the present invention are as follows. [Features] In the ultrasonic motor according to claim 2, the oil supply means is constituted by a guide groove formed in the rotor so as to apply a feed force to the traction oil with the rotation of the rotor.

[Operation / Effect] According to the above feature, when the rotor rotates, the traction oil sent by the guide groove is sent in the direction of the contact surface between the rotor and the vibrating body. As a result, traction oil can be supplied between the rotor and the vibrator without using a pump or the like.

The features, operations and effects of the ultrasonic motor according to claim 5 of the present invention are as follows. [Features] The ultrasonic motor according to any one of claims 1 to 4, wherein the vibrating body is formed by forming a tip portion in contact with the press contact surface into a tapered shape.

According to the above feature, the vibrating body is formed into a shape in which the side of the pressure contact surface is tapered, so that when the tip of the vibrator is pressed against the pressure contact surface of the rotor by vibration, the vibrating force is generated. Are concentrated at the tip to generate a high pressure contact force, and the traction oil is likely to generate a shear force. In other words, it is necessary to apply a relatively high pressure to generate a shearing force on the traction oil.However, simply forming the tip of the vibrating body into a tapered shape generates a high pressure contact force to reliably generate the shearing force. Will be generated. As a result, the rotor can be reliably rotated by simply changing the shape.

The features, functions and effects of the ultrasonic motor according to claim 6 of the present invention are as follows. [Features] In the ultrasonic motor according to claim 5, the tip of the vibrator is formed into a spherical shape, and the center of the rotation shaft center is located on a portion of the rotor where the tip of the vibrator contacts. The groove is concentric with the groove, and the radius of curvature of the groove is set to be larger than the radius of curvature of the tip of the vibrator.

According to the above feature, the traction oil stays in the groove, and the spherically shaped tip of the vibrator comes into contact with the inside of the groove. Since the radius of curvature is larger than the radius of curvature of the spherical surface at the tip of the tip of the vibrating body, the tip of the vibrating body comes into contact with a small contact surface, making the pressure per unit area extremely high and ensuring the traction oil A shear force is generated. As a result, traction oil is interposed between the tip of the vibrating body and the pressure contact surface of the rotor, and the rotor is reliably rotated.

The features, functions and effects of the ultrasonic motor according to claim 7 of the present invention are as follows. [Feature] The ultrasonic motor according to any one of claims 1 to 6, wherein the stator and the rotor form a closed internal space, and the traction is performed with respect to a portion connected to the internal space and the external space. The point is that an oil seal for preventing oil leakage is arranged.

[Operation / Effect] According to the above feature, the oil seal prevents the traction oil stored in the internal space from leaking by providing the oil seal at a portion connected to the internal space and the external space. as a result,
A good rotation state can be continuously maintained by the internal traction oil.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, a rotor R having an output shaft 1 is rotatably supported on a stator S, and a plurality of excitation elements 2 are provided in a space formed by the stator S and the rotor R. The ultrasonic motor includes a plurality of vibrators 3 driven by the ultrasonic motor. This ultrasonic motor is designed for a drive source for driving an electric wheelchair, a drive source for adjusting the inclination of a bed, a drive source for a nursing care robot, and a drive source for obtaining assist force in nursing equipment. Although it is small, it can make use of the point that it generates a high torque torque at the time of low-speed rotation and obtains a high braking force at the time of rotation stop.

The stator S is supported by a fixed member 13 such as a frame. The stator S is formed of a disk made of an iron material or an aluminum material, and has a through hole 4 centered on a rotation axis X at the center. A plurality of vibrators 3 are provided on the surface facing the rotor R, the plurality of vibrators 3 being driven by the plurality of excitation elements 2 in a ring shape around the rotation axis X with respect to the stator S. The rotor R is formed by integrally forming a disk-shaped portion 5 facing the stator S and a drum-shaped portion 6 covering the periphery of the stator with an iron material or an aluminum material. The output shaft 1 is fixed.

The output shaft 1 of the rotor R is connected to the stator S
Of the output shaft 1 and a ball bearing 7 provided on the output shaft 1 while being rotatable around the axis X and slidably movable in the direction of the axis X via a ball bearing 7. , A compression coil spring 9 is provided as a biasing means, so that the biasing force from the compression spring 9 acts on the side where the stator S and the rotor R are brought closer to each other, so that the distal end of the vibrating body 3 is brought into contact with the pressure contact surface of the rotor R. 10 is pressed. Further, an oil seal 11 is provided between the through hole 4 and the output shaft 1, and an oil seal 12 is provided between the outer periphery of the stator S and the outer periphery of the drum-shaped portion 6 of the rotor R.

In this ultrasonic motor, a plurality of excitation elements 2 such as piezoelectric elements and electrostrictive elements are provided on the support surface of the stator S.
Are arranged in a ring-shaped area centered on the rotation axis X, and a traveling wave is generated in the vibrating body 3 by supplying AC driving power having a predetermined phase relationship to each of the excitation elements 2. And a rotational force is applied to the rotor R.

In particular, in the ultrasonic motor according to the present invention, the vibrating body 3 is formed into a tapered shape using an iron material or an aluminum material, and the traction oil T is filled in a space formed between the stator S and the rotor R. It has a characteristic in that it is sealed. FIG. 1 and FIG. 2 show a typical embodiment. In this embodiment, three vibrators 3 are provided in the diameter direction of the stator S for one excitation element 2, so that the rotating shaft core is provided. The vibrators 3 are arranged concentrically in three rows as viewed in a direction along X. In addition, with respect to the pressure contact surface 10 of the rotor R at a position facing each of the vibrators 3, 3
Rows of concave grooves 10A are formed.

Each of the vibrators 3 has a tip 3A formed into a hemispherical surface and a conical surface 3B connected thereto, and is formed into a conical shape as a whole. Also, the concave groove 10A is finished to a smooth surface having a circular cross section, and the hemispheric surface is also finished to a smooth surface. The radius z of the concave groove 10A is larger than the radius y of the hemisphere. By setting, the tip 3A of the vibrating body 3 is configured to contact with a very small area at the bottom of the groove 10A (the groove 1 in FIG. 2).
0A and the tip of the vibrating body 3 are separated from each other,
Each is always in pressure contact with the urging force of the compression coil spring 9). The center portion of the disk-shaped portion 5 of the rotor R is formed to be thin, and when the output shaft of the ultrasonic motor is set to be vertical, the traction oil T can be stored in the center portion. As shown in FIG. 2, the level L of the liquid level of the traction oil T is set.

As shown in FIG. 3, the conical surface 3B of the vibrating body 3
A plurality of feed surfaces 17 having a posture substantially orthogonal to the vibration direction (vertical direction in the figure) of the vibrating body 3 and a guide surface 18 having a posture along the vibrating direction of the vibrating body 3 are continuously provided. Thus, the oil supply means F is formed. A rubber material is used for an oil seal 12 provided between the outer periphery of the stator S and the inner periphery of the drum-shaped portion 6 of the rotor R. As shown in FIG. Shape 6
A blocking surface 19 that is fitted and supported in a groove 6A formed on the inner surface of the traction oil and that prevents leakage of the traction oil T and a guide surface 20 that allows the traction oil T to flow into the contact side with the stator S are continuous. The traction oil T is formed to prevent leakage of the traction oil T. The peripheral surface on the side of the stator S with which the oil seal 12 contacts is made of titanium or magnesium having a low friction coefficient and high wear resistance. Member 21 made of a material or ring member 2 coated with a fluororesin represented by Teflon (registered trademark)
1 is provided.

As shown in FIG. 2, the stator S and the rotor R
The air passage 24 communicating with the space defined by
And a membrane filter 25 for preventing the leakage of the traction oil T while allowing the air to flow through the air passage 24, and when the air in the internal space expands due to a temperature change. However, even if it contracts, it allows air to flow while preventing traction oil from leaking.

With this configuration, the excitation element 2
When a rotational force is applied to the rotor R from the rotor R, the tip of the vibrating body 3 comes into pressure contact with the bottom of the concave groove 10A of the rotor R in an extremely small area. Since the traction oil T always intervenes between the bottom of the R groove 10A and the traction oil T, not only does not come into direct contact with each other but also a strong pressure acts on such a small area, so that the traction oil T is subjected to shearing force. And vibrator 3
Is transmitted to the rotor R to reliably apply a rotational force to the rotor R. Further, the traction oil T is more easily retained on the inner surface of the concave groove 10A than the flat surface, so that the traction oil T is reliably interposed when the front end of the vibrating body 3 and the bottom surface of the concave groove 10A come into contact. .

When the vibrating body 3 vibrates, the feed surface 17 as the oil replenishing means F formed on the conical surface 3B is used.
The traction oil T is sent to the distal end side of the vibrating body 3 through the
The traction oil T is always supplied to the space between the bottom of A and the pressure contact surface 10, so that not only the shortage of the traction oil T in this region is suppressed but also the oil is circulated in this region. , To suppress the temperature rise.

[Alternative Embodiment] The structure of the ultrasonic motor described above is a basic configuration, and alternative embodiments of each part of the ultrasonic motor will be described below. In this alternative embodiment, those having the same functions as those of the embodiment are denoted by the same reference numerals and symbols as in the embodiment.

[Rotor Shape] As shown in FIG. 5, a boss portion 5A fitted to the output shaft 1 is provided at the center of the disk-shaped portion 5 of the rotor R at a position closer to the stator S than the pressure contact surface 10. The boss portion 5A is formed in a protruding shape, and a concave portion 5B is formed on the outer surface of the rotor R corresponding to the boss portion 5A to reduce the rigidity of the rotor R. Form 5C.

Further, as shown in FIG. 6, a blocking surface 15 for blocking the flow of the traction oil T from the groove 10A and a flow of the traction oil T to the groove 10A are located near the pressure contact surface 10 as shown in FIG. A large number of concentric grooves are formed so that the cross-sectional shape becomes a saw-tooth shape with the guide surface 16 which allows the above.

That is, according to this configuration, not only the volume of the internal space becomes small, the amount of traction oil T used can be reduced, but also when the ultrasonic motor is used in the posture shown in FIG. Also, while promoting the inflow of the traction oil T into the portion of the press contact surface 10, the outflow from the press contact surface 10 is suppressed, and the traction oil T can be used effectively.

[Shape of vibrating body] Since the vibrating body 3 comes into contact with the rotor R at a high pressure, transmission through the traction oil T is reliably performed. It is effective to reduce the area in contact with the press contact surface 10. For this reason, in the embodiment, a plurality of vibrators 3 are provided for one excitation element 2,
By making each tip 3A contact the pressure contact surface 10 of the rotor R, it is possible to reduce the contact area at each tip 3A, and to surely apply a rotational force using the plurality of vibrators 3. did. However, considering the problem of the arrangement space of the vibrating body 3 and the easiness of processing, the configuration shown in FIG. 7 is also proposed. Note that FIG. 7 shows a perspective view of the vibrating body 3 and a cross-sectional view at a portion indicated by an arrow in the upper and lower directions.

That is, as shown in FIG. 7A, the vibrating body 3 is formed into an elliptical cone, and the tip 3A is formed into an elliptical sphere. As shown in (b), the vibrating body 3 is formed into a pentagonal plate-like material, and the tip 3A is formed into an arc while maintaining the plate thickness. As shown in (c), the vibrating body is formed into a triangular shape, and the tip 3A is formed into an arc shape while maintaining the plate thickness. As shown in (d), the vibrating body 3 is made of a plate-like material having a plurality of protrusions 3C formed in a comb shape, and each protrusion 3C is formed in a conical shape, and each of the protrusions 3C is formed. The tip 3A is formed into a spherical shape. As shown in (e), the vibrating body 3 is made of a plate-like material having a plurality of protruding portions 3C formed in a comb shape, and each protruding portion 3C has a long axis set in the radial direction of the stator S. While being formed into an elliptical cone,
The tip 3A of C is formed into an elliptical sphere. As shown in (f), the vibrating body 3 is made of a plate-like material having a plurality of protrusions 3C formed in a comb shape, and each protrusion 3C has a long axis set in the circumferential direction of the stator S. In addition to molding into an elliptical cone, the tip 3A of each of the protrusions 3C is molded into an elliptical sphere. As shown in (g), the vibrating body 3 is made of a plate-like material having a plurality of protruding portions 3C formed in a comb shape, and each protruding portion 3C is formed into a tapered shape. While maintaining the shape. As shown in (h), the vibrating body 3 is made of a plate-like material having a plurality of protrusions 3C formed in a comb shape, and the tip 3A of each protrusion 3C is formed in an arc shape while maintaining the plate thickness. Molding. As shown in (i), the vibrating body 3 is made of a plate-like material having a plurality of protruding portions formed in a comb tooth shape, and the tip 3A of each protruding portion 3C is formed into a flat surface while maintaining the plate thickness. .

[Surface Shape of Conical Surface of Vibrating Body] The combination of the feed surface 17 and the guide surface 18 formed on the conical surface 3B of the vibrating body 3 shown as the oil replenishing means F in the above embodiment is used as a traction oil. Considering the setting of the replenishment amount of T and the easiness of processing, as shown in FIGS.
It is also possible to set the degree and shape of the inclination as shown in FIG.

[Shape of Region Near Pressure Contact Surface] When the rotation direction of the rotor R is limited to only one direction, as shown in FIG. Guide grooves 23 are formed on the rotation axis X side (center side) and the counter rotation axis side (outer circumference side) from the pressure contact surface 10 so as to guide the traction oil T to the pressure contact surface 10 to supply oil. Means F is constituted. When the rotation direction of the rotor R can be switched to either the normal rotation or the reverse rotation, the traction oil T is applied to the pressure contact surface 10 with the rotation of the rotor R in either direction in FIG. A guide groove 23 having two kinds of characteristics for guiding is provided on the rotation axis center side (center side) with respect to the press contact surface 10;
Oil supply means F formed on the anti-rotation shaft center side (outer circumference side)
Is configured. By configuring the oil replenishing means F in this manner, the traction oil T is replenished between the distal end 3A of the vibrating body 3 and the press contact surface 10, and the inconvenience of the shortage of the traction oil T in this portion is eliminated. In addition, the temperature rise can be suppressed.

[Shape of Pressure Contact Surface] In the above-described embodiment, three vibrating bodies 3 are provided for the excitation element 2. However, as shown in FIG. On the other hand, it is possible to form the flat pressure contact surface 10 of the rotor R so as to correspond to the one provided with one vibrating body 3,
Further, as shown in FIG. 10 (b), it is also possible to form a single guide surface 10A with respect to the pressure contact surface of the rotor R.

[Shape of Oil Seal] In the above-described embodiment, the configuration in which the oil seal 12 is fitted and supported in the groove 6A of the disk-shaped portion 6 of the rotor R has been described. Conceivable. That is, in the case where the rotation direction of the rotor R is limited to only one direction, FIG.
As shown in (a) and (b), a single groove is spirally formed in the material of the oil seal 12 to form the blocking surface 19 and the guide surface 20, and the direction of formation of the spiral is changed. The traction oil T is set to return to the inside when the rotor R rotates. According to this configuration, when the rotor R rotates, the oil seal 12 not only prevents the leakage, but also positively sends the oil in the return direction, thereby exhibiting good sealing performance.

Further, as shown in FIG. 12A, a space 12A serving as a gap or a bubble is formed inside the oil seal 12 so that the oil seal 12 is configured to be more flexible and resistant to vibration. FIG.
2 (b), the blocking surface 19 of the oil seal 12
Lip 19A extending from the end of the
Is formed, and the lip 19A is formed so as to be bent in a direction in which the traction oil T is prevented from leaking, so that the oil is reliably prevented from leaking. FIG.
As shown in the figure, the oil seal 12 is fitted and supported on the outer periphery of the stator S, and a ring having a low friction coefficient and high wear resistance is provided on the inner peripheral surface of the rotor R with which the oil seal 12 comes into contact. The member 21 is provided.

[Urging Means] Since the ultrasonic motor has a structure in which the vibrating body 3 is pressed against the rotor R, the output shaft 1 is locked when not driven, and for example, fine adjustment of the rotation angle of the output shaft 1 is performed. Even if it is desired, the output shaft 1 cannot be rotated. Therefore, an ultrasonic motor was configured as shown in FIG.

That is, the basic configuration of the stator S, the rotor R, the excitation element 2, the vibrating body 3, and the like is basically the same as that of the above-described embodiment, and the position is determined by the stopper 30 provided on the output shaft 1. A pressure plate 31 provided with a ball bearing 7 in a regulated state and disposed on the side of the ball bearing 7
A thickening mechanism 32 formed by laminating piezoelectric elements is interposed as an urging means at a position surrounding the output shaft 1 between the motor and the stator S. In addition, the thickening mechanism 32 stacks piezoelectric elements in the strain direction, draws the rotor R toward the stator S via the output shaft 1 during driving, and presses the tip 3A of the vibrating body 3 against the press-contact surface 10 of the rotor R. And reduce the pressure contact force when not driven,
Alternatively, the positional relationship between the rotor R and the distal end 3A of the vibrating body 3 is set so as to cancel the pressing force, and the thickening amount of the thickening mechanism 32 is set. With this configuration, when controlling the rotation of the ultrasonic motor, the thickening mechanism 3 is used.
In the state where the driving power is supplied to the piezoelectric element 2, the rotation of the output shaft 1 can be controlled by controlling the driving power supplied to the excitation element 2. When the output shaft 1 is rotated by the force from, the drive power to the piezoelectric element of the thickening mechanism 32 is released, so that the output shaft 1 can be rotated with a small force.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of an ultrasonic motor.

FIG. 2 is a sectional view of an ultrasonic motor.

FIG. 3 is an enlarged sectional view of a vibrating body.

FIG. 4 is a sectional view showing an oil seal.

FIG. 5 is a sectional view showing an ultrasonic motor according to another embodiment.

FIG. 6 is a cross-sectional view showing a shape of a position near a pressure contact surface in another embodiment.

FIG. 7 is a diagram showing a plurality of types of vibrators according to another embodiment.

FIG. 8 is a cross-sectional view showing shapes of a plurality of types of conical surfaces according to another embodiment.

FIG. 9 is a diagram showing shapes of plural types of guide grooves in another embodiment.

FIG. 10 is a diagram showing a plurality of types of press contact surfaces and a vibrating body in another embodiment.

FIG. 11 is a diagram showing the entirety and a cross section of an oil seal according to another embodiment.

FIG. 12 is a sectional view showing a plurality of types of oil seals according to another embodiment.

FIG. 13 is a sectional view showing an ultrasonic motor according to another embodiment.

[Explanation of symbols]

 2 Exciting element 3 Vibrating body 9 Urging means 10 Pressure contact surface F Oil replenishing means R Rotor S Stator T Traction oil

Claims (7)

[Claims] A rotor is rotatably supported around an axis with respect to a stator, and is driven by a plurality of excitation elements in a ring shape around the axis with respect to a support surface of the stator facing the rotor. Equipped with a plurality of vibrators and biasing means for pressing the vibrators against the pressure contact surface of the rotor, and generating a traveling wave on each of the vibrators by driving each of the excitation elements according to a set rule. An ultrasonic motor configured to apply a rotational force to the rotor by the traveling wave, wherein traction oil is interposed in a contact portion between the vibrator and the rotor. 2. A storage space for the traction oil is formed between the stator and the rotor, and the traction oil stored in the storage space is sent to a contact portion between the vibrator and the rotor when the excitation element is driven. 2. The ultrasonic motor according to claim 1, further comprising oil replenishing means. 3. The vibrating body in a posture orthogonal to or substantially perpendicular to the vibration direction of the vibrating body so that the oil replenishing means sends traction oil to a contact portion between the vibrating body and the rotor when the vibrating body vibrates. 3. The ultrasonic motor according to claim 2, comprising a plurality of feed surfaces formed on an outer surface of the ultrasonic motor. 4. The ultrasonic motor according to claim 2, wherein said oil replenishing means comprises a guide groove formed in the rotor so as to apply a feed force to traction oil as the rotor rotates. 5. The vibrating body is formed by shaping a tip portion in contact with the pressure contact surface into a tapered shape.
The ultrasonic motor according to any one of claims 1 to 4. 6. A concave groove which is formed in a spherical shape at a tip end of said vibrating body, and which is concentric with a center of said rotary shaft center with respect to a part of said pressing surface which comes into contact with a front end of said vibrating body. 6. The ultrasonic motor according to claim 5, wherein a radius of curvature of the concave groove is set to be larger than a radius of curvature of a tip portion of the vibrator. 7. A closed internal space is formed by the stator and the rotor, and an oil seal for preventing leakage of the traction oil is disposed in a portion connected to the internal space and the external space. Item 7. The ultrasonic motor according to any one of Items 1 to 6.