JP2720037B2 - Ultrasonic motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultrasonic motor that is relatively small and can be used in the field of low power consumption. [Summary of the Invention] The present invention is an ultrasonic motor that frictionally drives a moving body by vibrating waves using expansion and contraction motion of a piezoelectric vibrator. The ultrasonic motor is fixedly supported on a center shaft fixed to a fixed base, and is formed of an elastic member. The vibrating body part, the piezoelectric vibrator fixed to the vibrating body part, and the moving body and the vibrating body part which are in pressure contact with the inner part of the outer peripheral part of the vibrating body part and whose central axis is a rotation guide As a configuration having a pressing means for pressing the body, the ultrasonic motor is made thinner, smaller, and more efficient. [Prior Art] Conventionally, as an ultrasonic motor using a piezoelectric vibrator, a standing wave system, a traveling wave system, and the like have been known. For example, the principle of the conventional ultrasonic motor is shown in "New Method / New Principle Motor Development and Practical Points" (1984) published by Japan Industrial Technology Center. As shown in FIG. 4, the movable body 4 has a ring-shaped vibrating body portion 403 and applies a predetermined voltage to the piezoelectric vibrator 404.
The structure to rotate 05 was known. Further, as shown in FIG.
And a structure in which a predetermined voltage is applied to the piezoelectric vibrator 504 to rotate the moving body 505 has been known. For example,
Such a conventional structure is disclosed in JP-A-9-96881 and JP-A-60-174078. [Problem to be Solved by the Invention] In the structure of the ultrasonic motor as described above, for example, according to the structure having the ring-shaped vibrating body portion 403 as shown in FIG. Since the bending traveling wave does not have a node of the vibration, the wave is attenuated by the support mechanism 406 to some extent, so that the electric
This leads to a reduction in mechanical conversion efficiency. Further, according to the structure having the disk-shaped vibrating body portion 503 as shown in FIG.
There is an advantage that it can be fixedly supported at two radii on the fixed base 502 because it is excited in the following vibration mode, but in the case of a thin and small type ultrasonic motor as the object of the present invention, , A decrease in efficiency due to variations in the positions of the nodes and the magnitude of the support area and support force, or a decrease in circuit efficiency due to the drive frequency exceeding 100 kHz due to the excitation in the secondary vibration mode Had problems such as causing [Means for Solving the Problems] To solve the above problems, in the present invention, a fixing means for fixing the ultrasonic motor, a central axis fixed to the fixing means, fixed to the central axis, A vibrating body portion formed of an elastic member, a piezoelectric vibrator fixed to the vibrating body portion, and a moving body having pressure contact with a portion inside the outer peripheral portion of the vibrating body portion and having a central axis as a rotation guide. The structure of the ultrasonic motor, which is relatively small and can be applied to low power consumption applications, is provided by including a vibrating body portion and a pressurizing means for pressurizing the moving body. [Operation] The ultrasonic motor of the present invention is configured such that the moving body is brought into pressure contact with the output take-out position set at a portion inside the outermost periphery of the vibrating body portion, so that the vibration which is the largest displacement portion Compared to a case where the moving body is brought into contact with the outer peripheral portion of the body, the amplitude of the vibrating body is less attenuated, and the rotational motion of the moving body can be efficiently converted. Furthermore, since the support of the vibrating body portion is fixed to the central portion so as to be integrated with the center axis, even a thin and small vibrating body portion can be stably and easily supported without almost attenuating the vibration wave. It becomes possible. Embodiment An embodiment of the present invention will be described below with reference to the drawings. The present invention is directed to a standing wave type or traveling wave type ultrasonic motor. FIG. 2 is a diagram showing an example of a traveling wave generation principle in a traveling wave type ultrasonic motor. 201 is a piezoelectric ceramic,
This is a piezoelectric vibrator made of a piezoelectric crystal, and is polarized at equal intervals with a width b as shown in the figure, and the directions of polarization between adjacent directions are opposite to each other. A conductive material such as silver or nickel is deposited on each piezoelectric vibrator by a method such as evaporation or plating.
Are formed, and they are connected to the signal lines 203 and 204.
, And high-frequency voltages from different signal sources are applied. A gap having a width c is provided between the electrode groups connected by the signal lines 203 and 204, respectively. At this time, the gap having the width c may be either polarized or non-polarized. here,
For convenience of explanation, the distance between the centers of the electrodes sandwiching the width c is a. The mechanism of generation of a traveling wave will be described below with reference to the above figures and symbols. Considering the midpoint of the electrode portion in FIG. 2, a bending vibration wave composed of a traveling wave and a backward wave can be expressed as follows. Asin (ωt−kx) + Asin (ωt + kx) Equation (1) Here, the equation (a) indicates a so-called standing wave. On the other hand, the bending vibration wave caused by the electrode portion shown in FIG. Bsin (ωt−k (x + a) + φ) + Bsin (ωt + k
(X + a) + φ) Equation (2) where k = ω / ν = 2π / λ, λ: wavelength, and phase difference angle with respect to φ: In equation (2), In other words, equation (2) can be expressed as follows. Bsin (ωt−kx + απ) + Bsin (ωt + kx + βπ) Equation (4) Accordingly, the bending vibration wave to be more excited is expressed by a combination of equations (1) and (4). Here, considering the condition for the presence of only the traveling wave component from the expansion formula of equation (4), it can be seen that α is an even number and β is an odd number. Here, from the equation (3), a and φ can be expressed by the following equations using α and β. That is, when (α, β) = (0,1) and (2,3), When (α, β) = (2,1), When (α, β) = (0,3), As a result, when both a and φ are simultaneously satisfied, only the traveling wave component exists. To give an example, Considering the case (1), the expression (1) + the expression (2) is as follows. Asin (ωt−kx) + Asin (ωt + kx) + Bsin (ωt−kx) −Bsin (ωt + k
x) Equation (6) where the amplitude A of the high-frequency voltage signal output from the drive circuit
If A and B are A = B, equation (6) becomes 2Asin (ωt−kx), and it can be seen that only the traveling wave component remains. Also,
In order to drive the motor in the reverse direction, only the backward wave component needs to be left. Therefore, α and β in equation (5) may be reversed so that α is an odd number and β is an even number. Actually, when considering the reference, it is only necessary to shift the phase of the signal to be added by 180 ° as compared with the case of the forward rotation driving. FIG. 3 is a view showing the principle that a traveling wave type ultrasonic motor rotates by a traveling component. Numeral 301 denotes a vibrator, which generates bending vibration because the piezoelectric vibrator is bonded to the elastic member. Here, when a traveling wave to the right is generated according to the principle shown in FIG. 2, the vibrating body 301 draws an elliptical trajectory to the left at one point on the surface portion. Moves in the opposite direction. The above is described in Nikkei Mechanical (1985.9.23) or the like, and a detailed description on that one point on the surface of the vibrating body 301 draws an elliptical locus is also described in the same document. FIG. 1 is a view showing a longitudinal sectional view of an ultrasonic motor according to the present invention. The central shaft 101 is integrated with the fixed base 102 by screwing or driving, and furthermore, the vibrating body 103
Is integrated with the central shaft at the center. At this time, the vibrating body 103 is made of an elastic member such as stainless steel, brass, duralumin, etc.
Will be supported by Also, the center axis 10
1.The mechanical resonance frequency of the fixed base 102 is sufficiently higher than that of the vibrating body composed of the vibrating body part 103, the piezoelectric vibrator 105, etc., so that the supporting structure has almost no vibration leakage or attenuation due to the influence of the support. . The piezoelectric vibrator 105 is at least one or more piezoelectric ceramics having a hole at the center or a piezoelectric ceramic composed of several pieces divided in the circumferential direction, and is provided with several patterns of electrode portions in the circumferential direction and is subjected to polarization processing. The thing is the vibrating body
It is joined to the side opposite to the surface on which the output take-out position 104 of 103 is provided. The moving body 106 is disposed so as to press and contact the output take-out position 104 set on the vibrating body 103 by the pressure adjusting spring 107 with the center axis 101 as a guide of the center of rotation. In this embodiment, the pressure adjusting spring 107 is formed in a plate shape and is set on a portion other than the fixed base 102 or the ultrasonic motor according to the present invention. Pressure is applied. On this occasion,
Assuming that the pressure applied to the moving body 106 by the pressure adjusting spring 107 is N, the friction coefficient between the vibrating body 103 and the moving body 106 is μ, and the distance from the center of the vibrating body 103 to the output extraction position 104 is a,
The torque T generated in the moving body 106 can be approximately T = μNa. The output take-out position 104 is set to efficiently convert the minute flexural vibration amplitude of the vibration wave component excited by the vibrating body including the vibrating body portion 103 and the piezoelectric vibrator 105 into the rotational motion of the moving body 106. This can be achieved by providing a protrusion on at least one of the vibrating body 103 and the moving body 106 such that the vibrating body 103 and the moving body 106 are in contact only in a part of the vibrating body portion 103 in the radial direction. In general, the component that contributes to the rotation of the moving body by the elliptical trajectory caused by the vibration wave has a speed difference and a phase shift in the circumferential direction at each position in the radial direction of the vibrating body portion 103, and these factors are rotation components. As a result mobile
This leads to braking of the 106 rotation movement. Therefore, it is better to provide the output take-out position 104 at a part of the vibrating body portion 103 or the moving body 106 in the radial direction to take out the flexural vibration. Incidentally, one of the features of the present invention is the set position of the output take-out position 104. That is, in applications where the ultrasonic motor according to the present invention is used in a relatively small size and low power consumption, the mechanical resonance frequency of the vibrator is inevitably increased due to the small diameter structure. . In general, if the frequency exceeds 100 kHz, the circuit efficiency of the drive system will inevitably decrease. Therefore, even if the wave number generated in the circumferential direction of the vibrating body is set to 2 to 4, it is excited in the primary vibration mode in the radial direction. Must. When the excitation is actually performed at a driving frequency that causes a primary vibration mode in the radial direction, the amplitude increases as the outer diameter increases, and the amplitude becomes maximum at the outermost circumference. Therefore, it seems that the output take-out position 104 should be set to the outermost periphery of the vibrating body and should be brought into contact with the moving body 106 at this position.
When 6 is brought into contact, the amplitude of the whole vibrating body is extremely attenuated, and as a result, even if rotational motion occurs, only a rotational motion with a small torque can be obtained. That is, the pressure adjusting spring
The pressure applied by 107 cannot be set high, and the motor efficiency also shows a low value. In addition, this output extraction position 104
The closer to the inner circumference, the less the amplitude generated in the vibrating body is attenuated.However, if it is set too close to the central axis, the amplitude itself at that part is small, so this is also In addition, the rotational movement becomes weak. Therefore, assuming that the radius of the vibrating body 103 is r, the relationship with the distance a from the center to the output take-out position 104 has an optimum value. In the case of a vibrating body having a radius of 5 mm and a thickness of 1 mm or less, the value varies depending on the diameter of the central shaft 101, but it is preferable to set the value to approximately 2 / 5r ≦ a ≦ 4 / 5r from the viewpoint of motor efficiency. Details of this will be described later. As described above, the vibrating body 103 and the piezoelectric vibrator 106
When the excitation is performed at a driving frequency such that the vibration mode becomes a primary vibration mode in the radial direction, an output extraction position 104 for frictionally driving the moving body 106 is set at a portion inside the outermost periphery of the vibration body section 103. This greatly contributes to the improvement of the motor efficiency. Note that this embodiment shows a case where the projection which is the output extraction position 104 is set on the moving body 106 side, and the diameter of the moving body 106 is substantially a.
If it is larger, the outer diameter of the vibrating body 106 may be smaller. Further, the vibrating body 103 is thin and has a small diameter because the supporting of the vibrating body 103 is fixedly supported at the center so as to be integrated with the center shaft 101.
Even with the 103, it is possible to stably and easily support the vibration wave without substantially attenuating it. FIG. 6 is a diagram showing a radial behavior of the ultrasonic motor according to the present invention. (A) is a partial longitudinal sectional view of an ultrasonic motor according to the present invention, and (a), (b), and (c) having different positions in the radial direction respectively indicate amplitude measuring sections. As an actual amplitude measuring method, in the case of the ultrasonic motor according to the present invention, since the contact type displacement meter cannot be used because the influence of its own weight cannot be ignored due to its small thickness and small diameter, an optical type A non-contact displacement meter is used. FIGS. 6 (b) and 6 (c) show radial directions a and b when the vibrating body section 602 and the piezoelectric vibrator 603 are excited with vibration waves.
FIG. 6 illustrates the amplitude measured at each of the points b and c.
The shape at this time is such that the wave number excited in the circumferential direction is 3, the outer diameter of the vibrating body 602 and the piezoelectric vibrator 603 is 10 mm, and the thickness is 0.3 m.
m, and the driving voltage was 3 Vp-p and 10 Vp-p. (B) shows the case where the vibrating body 602 is made of stainless steel, the primary mechanical resonance frequency in the radial direction is about 45 kHz, and (c) shows the case where the vibrating body 603 is made of brass. The resonance frequency is about 39.5kHz. Comparing FIGS. 6 (b) and 6 (c), the displacement distribution in the radial direction generally increases toward the outer periphery and becomes maximum at the outermost periphery, regardless of the material and the magnitude of the drive voltage. Is supported. FIG. 7 is a diagram showing the difference in the vibration body amplitude amount due to the difference in the output take-out position, and shows the difference in the vibration body part amplitude amount due to the difference in the contact position between the vibration body part and the moving body. 6 (a) shows a partial longitudinal sectional view of the ultrasonic motor according to the present invention, similarly to FIG. Here, the vibrating body in a state in which the moving body is in contact with the vibrating body part 702 substantially only at the a, b, and c portions, with the portions a, b, and c having different positions in the radial direction as output extraction positions. Are measured. That is to say,
Band-shaped projections are set so as to be in contact with the positions (b) and (c), and the moving bodies are sequentially mounted on the vibrating body section 702 to compare the degree of attenuation of the vibrating body amplitude. The weight of the moving object is 0.3 g. Further, as a method of measuring the frequency characteristic of the vibration body amplitude amount, by utilizing the fact that the piezoelectric vibrator 703 is composed of two circuits, a frequency voltage is swept and applied to one of the piezoelectric vibrators 703 to excite the vibration body to a standing wave excitation. A technique is used in which a back electromotive force generated by the piezoelectric effect on the other circuit side is Fourier-transformed by a spectrum analyzer. FIGS. 6 (b) and 6 (c) show the amplitudes of the moving body near the mechanical resonance point of the moving body by sequentially changing the moving bodies that contact only the positions a, b and c using the above-described method. It is a diagram illustrating the degree of attenuation. Vibrating body part 702 at this time
The shape of the piezoelectric vibrator 703 is the same as that in FIG. 6, and the applied voltage is 5 Vp-p. Also,
(B) shows the case where the vibrating body 702 is made of stainless steel.
(C) also shows that the case where brass is used
It is the same as the figure. Comparing FIGS. 6B and 6C, it can be seen that the maximum amplitude at the resonance point is smaller in B than in B and B than in B regardless of the material. That is, the more the contact position between the moving body and the vibrating body portion is moved to the outer peripheral portion, the more the attenuation increases. It should be noted that “E” in the figure is obtained by examining the frequency characteristics of the vibrating body in a state where the moving body is not mounted, and obviously shows the largest amplitude. However, as long as a moving body of about 0.3 g is placed, the differentiation between A and E is not possible, and even if the moving body is brought into contact with the position of A, the amplitude amount in the almost vibration-free state can be obtained. Will be. As described above, when the results of FIG. 6 and FIG. 7 are combined, when the ultrasonic motor according to the present invention is excited at a drive frequency such that it becomes a primary vibration mode in the radial direction, the number of the outer periphery becomes Although the amount of amplitude increases, conversely, if the moving body is arranged so as to contact only the outer peripheral portion, the amount of attenuation of the amplitude increases, which is inconvenient. That is, it can be said that there is an optimum position for the output take-out position, which is the contact position between the moving body and the vibrating body. And the value is that the attenuation is large when it is moved to the outermost circumference, and that the amplitude is small when it is moved to the innermost circumference, and about 1/5 from the center to the radius r on the motor structure depends on the center shaft 701. Considering that the strength of the movable body against the pressing force or the like may occur if the supporting body is not used, it is desirable that the output take-out position from the vibrating body to the movable body be set to approximately 2 / 5r ≦ a ≦ 4 / 5r. It can be said. Considering the above phenomenon physically, the vibrating body and the piezoelectric vibrator can vibrate in a free state at the outer peripheral part from the output take-out position, which is the amount of attenuation of minute elliptical vibration generated on the surface of the vibrating body. Can be converted as much as possible to the rotational motion of the moving body. Regarding the output take-out position, the outer diameter and
Depending on the thickness, and the difference in the pressing force of the moving body, a more optimal position will be determined, but for the ultrasonic motor according to the present invention, by setting 2 / 5r ≦ a ≦ 4 / 5r, That is, high-efficiency and smooth rotation can be realized even at a low voltage. FIGS. 8 and 9 are plan views of the electrode pattern of the piezoelectric vibrator for traveling wave excitation. The ultrasonic wave motor according to the present invention is joined to one side of the vibrating body so that the traveling wave excitation can be realized. 2 shows a specific electrode pattern of a simple piezoelectric vibrator. FIG. 8 shows a piezoelectric vibrator 801 having a hole in the center portion provided with sector-shaped electrode portions 802a to 802d on one side surface, and the arc length of each electrode portion is determined by the clearance between adjacent electrode portions. It is set to be approximately 1/4 of the traveling wave wavelength excited. Here, it is possible to excite a traveling wave by applying polarization processing to the polarities as shown in the figure and applying the same signal to 802a and 802c, and a signal having a phase difference of 90 ° in time to 802b and 802d. Become. Since the arc length of each electrode portion is 1/4 wavelength as described above, 802a to 802
One wavelength can be formed by four parts of d. Therefore, this embodiment shows a case where the wave number is 3. In the figure, the sign + indicates that a positive electric field has been applied to the back surface of the electrode portion to perform polarization, and the sign − indicates that
This indicates that a negative electric field is applied to the electrode portion on the back surface to perform polarization processing. In this case, the electrode portion on the rear surface may be an electrode having the same shape and the same position as the front surface or a front electrode. FIG. 9 shows an embodiment of another electrode pattern.
The piezoelectric vibrator 901 having a hole at the center has fan-shaped electrode portions 902a to 902d provided on the surface, and a length between the ends of each of the electrode portions is approximately half the arc length of the electrode portions 902a to 902d. Electrodes 903a to 903d corresponding to the above are provided. Here, as shown in the figure, the polarization is applied to the polarity, and 902a is applied in accordance with the rule shown in FIG.
When high-frequency voltages having different phases are input to the electrodes 902d to 902d, a traveling wave component is excited. At this time, another electrode group 903a to 903d is used for detecting the level and phase of the back electromotive voltage generated at the time of excitation of the vibrating body portion as a detection signal to perform frequency tracking and speed change of the ultrasonic motor. In addition to the above, when spurious vibration generated at the time of excitation of the vibrating body portion is remarkable, the intensity of the traveling wave component can be increased by using it for driving. Although the two embodiments have been described in detail as the electrode patterns of the piezoelectric vibrator for exciting a traveling wave, there are many other electrode patterns that can excite a traveling wave. It goes without saying that the invention can be implemented. FIG. 10 is a longitudinal sectional view showing another embodiment of the ultrasonic motor according to the present invention. As in FIG. 1, the central shaft 1001 is integrated with the fixed base 1002 by screwing or driving, and the vibrating body 1003 is integrated with the central shaft 1001 at the central portion to form a central fixed support structure. Has been realized.
The feature of this embodiment is that the vibrating body 1003 and the moving body
This is that a displacement enlargement mechanism 1004 is provided at an output extraction position where the vibration wave component is converted into a rotational motion by contact with the vibration wave component 1006. In general, the maximum value Umax of the lateral velocity component of the elliptical trajectory contributing to the rotational movement of the moving body 1006 is: Umax = −2π ² fξ (T / λ) f: drive frequencyξ: longitudinal amplitude T: vibrating body thickness λ: vibration Since it is expressed as a wave wavelength, it is sufficient to increase the thickness of the vibrating body in terms of shape in order to improve the number of revolutions. However, simply increasing the thickness extremely increases the mechanical hardness and increases the resonance frequency. Therefore, it is advisable to provide a strip-shaped displacement enlarging mechanism 1004 so as to be strip-shaped in the circumferential direction of the vibrating body portion 1003. Here, the set position of the displacement enlarging mechanism 1004 in the radial direction of the vibrating body portion 1003 is approximately 2 / 5r ≦ a ≦ 4 /
5r is preferable in terms of motor efficiency. Further, the displacement enlarging mechanism 1004 may be formed integrally with the vibrating body part 1003, but the cost is high in processing such a denture, so that the displacement enlarging mechanism 1004 is separately formed and vibrated later. It may be integrated with the body part 1003. In this case, the displacement enlarging mechanism 1003 can be formed integrally with plastic. In the present embodiment, unlike the plate-shaped pressure-adjusting spring structure in FIG. 1 described above, a stopper 10 that can be fitted to the center axis 1001 is used as a method for pressing the moving body 1006.
By using a pressure adjusting spring 1007 consisting of a cross spring 09 and the like, and a washer 1008 which also serves as a pressing force adjustment, it is possible to achieve a more compact structure than the above-mentioned pressing mechanism. Further, in the present embodiment, as in FIG. 1, the support of the vibrating body portion 1003 is fixed to the central portion so as to be integral with the center shaft 1001, so that even the vibrating body portion having a small thickness and a small diameter can hardly generate vibration waves. It is possible to stably and easily support without damping. FIG. 11 shows a specific example of the displacement enlarging mechanism, in which a halfway portion in the radial direction of the vibrating body portion 1101 is provided with equally-spaced cut grooves in a band shape, such as a comb-like shape. Realizes the displacement enlargement mechanism 1102. In this case, if the interval between the kerfs is too large, the contact surface with the moving body is reduced, and the rotation speed and the torque are reduced. On the other hand, if the length of the comb teeth is too long, the comb teeth themselves have a vibration mode, and the displacement magnifying mechanism 1102 does not work as a rigid body, which leads to a reduction in motor efficiency. FIG. 12 is a diagram showing an example of motor characteristics of the ultrasonic motor according to the present invention. The target motor specifications are as follows. From the figure, it can be seen that the maximum efficiency is around 16 Vp-p, which is slightly less than 40%. By changing the material of the moving body to a material with a higher friction coefficient, slip at the contact portion between the displacement magnifying mechanism and the moving body is reduced. Therefore, efficiency is slightly improved. In any case, the motor structure according to the present invention can realize high efficiency even in a small-diameter and thin ultrasonic motor. [Effects of the Invention] As described above, the present invention is an ultrasonic motor that frictionally drives a moving body by vibration waves using the expansion and contraction motion of a piezoelectric vibrator, and is fixedly supported on a central axis fixed to fixing means. A vibrating body portion formed of an elastic member, a piezoelectric vibrator fixed to the vibrating body portion, and a moving body having pressure contact with a portion inside the outer peripheral portion of the vibrating body portion and having a central axis as a rotation guide. And a pressurizing means for pressing the vibrating body and the moving body, the following effects are obtained. (1) The ultrasonic motor can be made thinner. (2) The size of the ultrasonic motor can be reduced. (3) The efficiency of the ultrasonic motor can be improved. Therefore, the ultrasonic motor can be applied to the field of precision equipment. For example, if used for an electronic watch motor,
Unprecedented possibilities arise, such as being unaffected by magnetism, reducing the number of wheel train gears due to low speed and high torque, enabling forward and reverse drive, and being strong in holding torque so as to be less susceptible to disturbances.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of an ultrasonic motor according to the present invention, FIG.
FIG. 3 shows the principle of traveling wave generation, FIG. 3 shows the principle of rotation of a traveling wave type ultrasonic motor, FIGS. 4 and 5 are longitudinal sectional views of a conventional ultrasonic motor, and FIGS. c) is an explanatory diagram showing the radial behavior of the ultrasonic motor according to the present invention, FIGS. 7 (a) to 7 (c) are explanatory diagrams showing the difference in the vibrating body amplitude amount due to the difference in the output take-out position, and FIG. And FIG. 9 is a plan view of a traveling wave excitation piezoelectric vibrator electrode pattern. FIG. 10 is a longitudinal sectional view showing another embodiment of the ultrasonic motor according to the present invention.
11 (a) and (b) are a plan view and a cross-sectional view of a displacement magnifying mechanism according to the present invention, and FIG. 12 is a diagram showing an example of motor characteristics of an ultrasonic motor according to the present invention. 101,410,501,601,701,1001 ... Center axis 102,402,502,1002 ... Fixed base 103,403,503,602,702,1003,1101 ... Vibrating body 104 ... Output taking out position 105,201,404,504,603,703,801,901,1005 ... Piezoelectric vibrator 106,405,505,1006 ... Moving body 107,1007 ... Pressure adjusting springs 202, 802, 902, 903: Electrodes 1004, 1102: Displacement expansion mechanism

Claims (1)

(57) [Claims] In an ultrasonic motor that frictionally drives a moving body by a vibration wave using expansion and contraction motion of a piezoelectric vibrator, a fixing unit for fixing an ultrasonic motor; a central axis fixed to the fixing unit; A vibrating body portion fixed and formed of an elastic member; a piezoelectric vibrator fixed to the vibrating body portion; and a pressurized contact with a portion inside the outer peripheral portion of the vibrating body portion, and rotationally guiding the central axis. And a pressurizing unit that presses the vibrating body and the moving body, wherein the vibrating body has a primary vibration having no nodes other than a central portion in a radial direction. An ultrasonic motor characterized in that it is excited at a mode vibration frequency. 2. 2. The ultrasonic motor according to claim 1, wherein the vibrating body portion has an output take-out portion formed of a tooth-like displacement enlarging means that becomes uneven in the circumferential direction.