JPH02280677A - Vibration wave motor - Google Patents

Abstract

PURPOSE:To suppress noise by providing a portion having uneven dynamic rigidity in an elastic body. CONSTITUTION:A vibration wave motor comprises an elastic body 28, a piezoelectric element, a rotor, and the like. The elastic body 28 is formed into a ring and a plurality of grooves are provided at the side of pressure contact face. Forty grooves 28b-28o are made slightly deeper than other groove 28a and the dynamic rigidity is varied in order to prevent generation of progressive wave in unnecessary mode, and 7th order mode of outward bending vibration of ring face is employed as the driving mode. By such arrangement, generation of unnecessary mode is prevented.

Description

[Detailed description of the invention] [Fields of use of soil collection a] The present invention relates to a vibration wave motor.

[Prior Art] Photographic wave motors, which generate progressive vibration waves in an elastic body and use these vibrations to move a moving body such as a rotor, have become popular in recent years because they are small and can provide high torque at low speeds. -Used to drive the photographic lens of reflex cameras.

Figure 6 is a vertical cross-sectional view of a single-lens reflex camera lens incorporating a vibration wave motor for driving the lens. As shown in FIG. 7, a groove IA having a predetermined length 4I51t and a depth h is provided over the entire circumference on the side that contacts the rotor 3, which will be described later. Further, at the bottom of the elastic body 1, there is a
'Two groups of drive phases, etc. for driving consisting of piezoelectric elements 2 such as ZT are fixed with an adhesive. Ultrasonic drive signals with different phases are applied to the two groups of drive phases consisting of the piezoelectric elements 2 as electro-mechanical energy conversion elements by a known method, and in response to these signals, the elastic body When the elastic body 1 vibrates, a progressive vibration wave that rotates in the circumferential direction of the elastic body 1 forming the vibrating body is generated. Reference numeral 3 denotes an annular rotor having an end in pressurized contact with the upper surface of the elastic body 1, and the other end of the rotor 3 as a moving body has an annular vibration absorber 5 made of rubber or the like.
is provided. Reference numeral 4 denotes an annular vibration insulator made of felt or the like, and the insulator 4 receives pressing force from two disc springs 9 superimposed on each other via a felt base 8 .

The aforementioned rotor 3 is connected to the connecting plate 22 via the aforementioned vibration absorber 5.
The annular connecting plate 22 that is closely held is fixed to the output transmitting body 25 by tightening screws (not shown). The output transmission body 25 that rotates around the optical axis is a ball 10.
A ball bearing is constructed using ball races 13 and 14. Ball races 13 and 14 are the outer cylinder 12 of the photographic lens.
The outer cylinder 12 is combined with the fixed cylinder 11 and fixed to the camera mount 19.

A connecting roller 15 is fixed to the tip of the output transmitting body 25, and engages with a keyway (not shown) of a movable ring 1f that holds a focus lens 2f provided in the optical axis direction. Fixed inner cylinder 1B
The threaded portion 18a of the movable ring 1f and the threaded portion 17a of the movable ring 1F are helicoidally coupled, and the movable ring 17 can be rotated and moved in the optical axis direction via the connecting rollers 15 by the rotational movement of the output transmission body 25.

In such a configuration, an AP signal from the camera side or
A driving signal from the manual ring 16 causes a vibrating body made of an elastic body and a piezoelectric element to generate progressive vibration waves using a known method, rotates the rotor 3, and finally moves the focus lens 27 nine times in the optical axis direction. , to adjust the focus.

In such a vibration wave motor, the vibrating body is formed of a uniform member so that the progressive vibration wave for driving has the same amplitude and the same wavelength at any position on the vibrating body, and is made of a substantially uniform member as shown in Fig. 147. It has a structure.

[Problems to be Solved by the Invention] However, in the conventional vibration wave motor described above, flatness errors after machining of the imaging body, the movable body, or their holding members cause a surface pressure ram on the contact surface between the vibrating body and the movable body. Due to this cause, a progressive vibration wave having a wavelength different from that of the driving progressive vibration wJ@ grows, and noise may be generated from the contact surface between the vibrating body and the moving body.

When the progressive vibration waves having the wavelengths that generate this noise were analyzed, it was found that the unnecessary progressive vibration waves had one wavelength or multiple wavelengths.

An object of the present invention is to prevent the generation of traveling waves of unnecessary wave numbers without affecting the wavelength of the drive mode, and to provide vibration-free vibration waves.

[Means for Solving the Problems] A typical example for achieving the object of the present invention is to apply an alternating current voltage to first-steer drive electric-mechanical energy conversion means having a predetermined positional phase difference with each other. In a vibration wave motor that forms a progressive vibration wave in the elastic body and relatively moves the elastic body and a pressure member that is in pressure contact with the elastic body, the elastic body or a support member of the elastic body The natural frequency difference between the standing waves in the drive mode excited in the elastic body is greater than the frequency difference between the standing waves in at least one vibration mode other than the progressive vibration wave for driving. The vibration wave motor is characterized in that the dynamic stiffness non-uniform portions are provided so as to be small, and the dynamic stiffness non-uniform portions are made equal or close to each other for each driving electro-mechanical energy conversion means.

[Function] In the vibration wave motor having the above configuration, even if an unnecessary vibration mode occurs, the natural frequency difference between the standing waves in that mode is larger than the natural frequency difference between the standing waves in the drive mode. ,
The formation of traveling waves in unnecessary modes is prevented without affecting the formation of traveling waves in the drive mode, and the generation of noise such as @ noise can be prevented. By making the positions equal or close to each other, it is possible to prevent the dynamic stiffness uneven portion from affecting the drive.

[Embodiment] FIG. 1 is a plan view of an elastic body showing an embodiment of a vibration wave motor according to the present invention.

The elastic body 28 according to this embodiment is formed in an annular shape as shown in FIG. 7, and has a plurality of grooves formed on the pressure contact surface of the movable body (not shown) in order to increase the amplitude.

In this embodiment, 90 grooves are formed at a pitch of 4°, and in addition to the purpose of expanding the amplitude described above, the grooves shown in black in the figure are used to prevent the generation of traveling waves in unnecessary modes. 28b, 28c.

211d, 28e, 28f, 28g, 28h, 281.
28J, 28, 281.28m.

The depth h of the 14 grooves 28n and 28o (hereinafter referred to as deep grooves) is set to be slightly smaller than the other grooves 28a (76 grooves in total), for example, 0.
2 ■ Deepening and changing dynamic rigidity. It should be noted that the vibrating body of this embodiment is configured to use the seventh mode (seven wave mode) of the ring out-of-plane bending vibration as the drive mode.

Therefore, the noise that occurs when the motor is driven is caused by the drive itself.
Since it is a lower order mode than the 3rd, 4th, 5.6th order (
Waves) or a combination of them. In addition, in the motor shown in the conventional example,
The secondary mode hardly occurred, probably because it was unstable considering the contact state between the elastic body and the moving body.

In the vibration wave motor having the elastic body 28 having such a structure with non-uniform dynamic stiffness, prevention of squealing will be described below, taking as an example a case where an unnecessary fifth-order mode occurs.

The principle of formation of a progressive vibration wave is that it is formed by combining two standing waves that have the same wavelength (λ) and frequency and are shifted in position by λ/4 from each other in phase. Therefore, in order to prevent the generation of traveling waves in unnecessary modes, the elastic body 28
It is only necessary to make sure that the natural frequencies of the two standing waves in the unnecessary modes formed above are not equal, and for this purpose, in this embodiment, deep grooves 28b...28h...28° are formed to reduce the elasticity. The dynamic rigidity of the body 28 is made non-uniform.

In the formation of a traveling wave, two standing waves have a positional phase of λ
The shift of /4 means that if the antinode of one standing wave is at any point in the circumferential direction of the elastic body 28, there must be a node of the other standing wave at that point.

In the vibration wave of the fifth-order mode, one wavelength formed on the elastic body 28 has a pitch of 72°. Here, the deep groove 28b
If five standing waves with nodes are generated, the antinode positions of the standing waves are deep grooves 28e, 28h, 281°, 28J, and 28m, and the natural vibration of the elastic body 28 corresponding to this standing wave Let the number be frc. In addition, 5 with the deep groove 28b as its belly
If a standing wave of waves is generated, the standing wave is deep groove 28
e, 28h, 28i.

28J and 28m are the node positions, and the natural frequency of the elastic body 28 corresponding to this standing wave is f.

In order to generate a fifth-order traveling wave, it is necessary that the natural frequencies f and ftc of both standing waves are equal, or that the difference in natural frequencies, Δrra-1f-f, e1, is small. On the other hand, if this natural frequency difference Δrrs is large, the fifth-order mode traveling wave will not be generated.

Generally, natural frequency f1 when purchase is m and stiffness is k
Since the thickness of the elastic body is thin in the deep groove part, the bending rigidity is small.Therefore, the bending rigidity when the deep groove position is the antinode is ke, and the bending rigidity when the deep groove position is the node. Then, when the position of the deep groove is used as a node, since the thickness of the plate at the antral position is thick, k,>kc, that is, f□>fre.

Therefore, the natural frequencies f in the fifth mode, and f
The frequency of vibration is different from re, and the difference is large, so the frequency of the 5th mode, which can cause squealing, can become a traveling wave. Even if the frequency of the 5th mode occurs for some reason, This does not cause any squealing.

In addition, the effect of preventing the occurrence of this squeal is due to the natural frequency difference Δf,
It is clear that the larger the value, the more conspicuous it is.

The above explanation is for the case where the unnecessary mode is the 5th mode, but
In the elastic body 28 of this embodiment, in addition to the fifth-order mode,
Formation of traveling waves is also prevented in unnecessary modes such as the 6th mode, 4th mode, and 3rd mode, as in the case of the 5th mode.

That is, in the case of the fourth mode, the deep grooves 28b and 28f.

In 28g, 28L, and 28, 281 makes the dynamic stiffness non-uniform, and makes the natural frequency difference Δfr4 different depending on the position of the vibration wave, thereby preventing the formation of a fourth-order mode traveling wave.

However, in this case, the 90 grooves formed on the elastic body 28 at equal pitches all around the circumference are not divisible by 4, so the center position is set between the deep grooves 28f, 28g, (28 and 281). The pitch is 90'', which is one wavelength of the next mode.

In addition, in the case of the third mode and the sixth mode, the deep groove 28c,
28d, 28f, 28g, 28, 281.28n,
28o makes the dynamic stiffness non-uniform, and the specific moving number difference Δf, 3.
By varying Δfr8 depending on the position of the vibration wave, the formation of traveling waves in the third and sixth modes is prevented.

However, in this case as well, the deep grooves 28c and 28d and the deep groove 28f
, 28g, deep groove 28, 281, deep groove 28n, 28
1 in the case of 3rd order, with the center position between each of o.
In the case of 72 wavelengths and the 6th mode, the pitch is 60°, which is one wavelength.

Figure 3 shows the natural frequency difference Δf? of these first modes. ,
1 is obtained for each mode.

As can be seen from Fig. 3, the seventh mode for driving also has an inherent difference in the number of moving images Δfr? due to non-uniformity of dynamic stiffness. However, the amount is small, and it also occurs when other noises occur. Specific imaging number difference Δf13 in 3rd, 4th, 5th, and 6th modes. Δ
f, 4°Δf15. Δf, Δfr when 6 is the 7th mode? Since it is larger, it can be seen that the noise prevention effect is greater. In other words, it has less negative impact on motor drive and has zero effect! % loss is less likely to occur.

That is, the natural frequency difference Δfrn of each of these modes largely depends on the deep groove pattern as shown in FIG. 1, that is, the average partial pattern of dynamic stiffness.

FIG. 2 is a plan view of the piezoelectric element 30 of this embodiment. That is, this is a view of the piezoelectric element 30 bonded to the elastic body 28 of FIG. 1, viewed from the back side.

The electrode group indicated by 30^ is the A-phase driving electrode, which is a collection of electrodes of λf/2 of the wavelength λf of the 7-wave drive. (Illustrated) shows the applied voltage during polarization treatment, respectively. The electrode group indicated by 30B is a B-phase drive electrode group, and is formed at a position shifted by λ1/4 phase with respect to the A-phase drive electrode. The A-phase drive electrode 30^ and the B-phase drive electrode 30B are line symmetrical with respect to the plane of symmetry 31. When driving the motor, the A phase drive electrode 30
Alternating voltages whose phases are temporally shifted by ±90 degrees are applied to the A and B phase drive electrodes 30B.

FIG. 4 shows θ from the plane of symmetry 29 of the elastic body 28 shown in FIG.
The vibration wave of the first mode in the direction corresponds to one wavelength of each mode (φ.

= 360°), the dynamic stiffness non-uniform part (first
This is a diagram in which the substantial sum R of the deep grooves shown in black is calculated.

Therefore, the relationship is θ=θll/n. 32.33°34
．． 35 is the case of vibration modes that produce noise, such as the third, fourth, fifth, and sixth modes, respectively. As shown in Figure 4,
Each mode has a phase φ of approximately 90°. The maximum of R at the position where is shifted,
Taking the minimum. In other words, the non-uniformity of dynamic stiffness is approximately 90°.
The maximum and minimum occur where the phase shifts, making it the most difficult form to become a traveling wave. FIG. 5 is a diagram similar to FIG. 4, but in the case of the seventh-order mode 36 for driving. From this figure, it can be seen that the maximum and minimum differences in R are smaller than in other modes. In other words, there is little adverse effect on the traveling wave of the seventh mode.

However, it is not zero. Now, when the two symmetry planes of the deep groove pattern of the elastic body 28 and the symmetry plane 31 of the piezoelectric element 30 are made to match, the antinode position of the A-phase standing wave (B The node position of the B-phase standing wave when only phase 30B is driven), P2゜P4 is the antinode position of the B-phase standing wave (
The node position of the A-phase standing wave). Since the values of R for P and -P4 are equal, it can be seen that the non-uniformity of dynamic stiffness has a similar effect on the A-phase and B-phase drive electrodes.

In other words, the natural frequency of the A-phase standing wave and the natural frequency of the B-phase standing wave match and do not adversely affect the drive.However,
The symmetry plane 29 of the deep groove pattern of the elastic body 28 and the piezoelectric element 30
If the plane of symmetry 31 is shifted, the antinode position of the A-phase standing wave (nodal position of the B-phase standing wave) %P61P8 becomes the antinode position of the B-phase standing wave (nodal position of the A-phase standing wave), or The opposite is true.

In this case, the value of R of Ps (P9) and P7 is
8*P is larger than the R value of 6. In other words, due to the non-uniformity of dynamic stiffness, the natural frequency of the A-phase standing wave is lower than the B
The natural frequency of the phase standing wave becomes high and the unevenness of the traveling wave becomes large.For this reason, it is best to match the plane of symmetry 29 of the elastic body 28 and the plane of symmetry 31 of the piezoelectric element to the driving wave. It turns out that it does not have any negative effects.

Note that the above-mentioned substantial sum R of the dynamic stiffness non-uniform parts is calculated by assuming that the size of one of the dynamic stiffness non-uniform parts is Rol, and approximating the shape of bending vibration by Sin, and considering the sum of the entire elastic body ring. and R(φ1)=, Σ Ral I sin
(N0 section +φ, 1) 11■1, where k is the number of parts with non-uniform dynamic stiffness.

If the dynamically non-uniform portion is a deep groove as in this embodiment, R(φn) represents the distribution of the total sum of the deep grooves depending on the traveling wave position (φn).

4 and 5 show the case where R, l=1.6 In the case of this embodiment, as described above, when the antinode of vibration is located at the position where R is large, k becomes small. In other words, f7 is small. Therefore, the natural frequency of the mode that becomes the antinode of vibration becomes the minimum at the maximum position of R, and the natural frequency of the mode that becomes the antinode of vibration becomes the maximum at the minimum position of R. In fact, traveling waves that cause noise have frequencies between these maximum and minimum natural frequencies. Therefore, the larger the difference in their natural frequencies, the more noisy the traveling waves will be, moving away from the resonance point, making the field of view very small, and eventually attenuating them.

Although the above embodiment has been described using an example in which the deep groove is 0.2 mm deeper than the other grooves, it is clear that the effect will be greater if this amount is increased, and the present invention is not limited to this value.

Furthermore, in addition to changing the groove depth as described above, the dynamic stiffness can also be changed by increasing or decreasing the added mass or added resistance, or by changing the dynamic stiffness by a combination of these. Furthermore, the same effect can be obtained by making not only the dynamic stiffness of the elastic body uniform but also the dynamic stiffness of peripheral members such as the rotor and vibration insulator 4 shown in FIG. 6 non-uniform. Furthermore, the pattern of non-uniform dynamic stiffness is not limited to this embodiment, and any pattern may be used as long as the dynamic stiffness is equal or close to each other for each drive phase.

[Effects of the Invention] As explained above, according to the present invention, for example, by providing a dynamic stiffness non-uniform portion in an elastic body, it is possible to generate waves other than traveling waves for driving without using electric control means such as an electric circuit. The formation of traveling waves for driving can be prevented, noise such as squealing during driving can be suppressed, and the formation of traveling waves for driving is not affected.

[Brief explanation of drawings]

Fig. 1 is a plan view of an elastic body showing Embodiment 1 of the vibration wave motor according to the present invention, Fig. 2 is a plan view showing the arrangement of piezoelectric elements, and Fig. 3 is the natural frequency of the zero-order mode of the elastic body. Figures 4 and 5 show the changes in dynamic stiffness depending on the phase of the zero-order mode, Figure 6 is a cross-sectional view of the lens barrel, and Figure 7 shows the difference for each mode. FIG. 1.28: Elastic body 2.30: Piezoelectric element 3: Rotor 4: Vibration insulator 28b...28i...280: Deep groove and 4 others Diagram mode order n

Claims (1)

[Scope of Claims] 1. By applying an alternating current voltage to drive electric-mechanical energy conversion means having a predetermined positional phase difference with each other, a progressive vibration wave is formed in the elastic body, and the elastic body and the In a vibration wave motor that relatively moves a pressure member that is in pressure contact with an elastic body, a standing wave of a driving mode excited in the elastic body is applied to either the elastic body or a supporting member of the elastic body. The dynamic stiffness non-uniform portion is provided so that the natural frequency difference is smaller than the frequency difference of the standing wave in at least one vibration mode other than the progressive vibration wave for driving, and each of the electric-mechanical energy for driving A vibration wave motor characterized in that the dynamic stiffness non-uniformity portions of the converting means are equal or close to each other. 2. The vibration wave motor according to claim 1, wherein the dynamic stiffness non-uniform portion is formed in a line-symmetrical pattern. 3. The two groups of electric-mechanical energy conversion means are arranged line-symmetrically with a predetermined positional phase difference, and coincide with or slightly deviate from the plane of line-symmetrical symmetry of the pattern of the dynamic stiffness non-uniform portion. The vibration wave motor according to claim 2, characterized in that: 4. The vibration wave motor according to claim 1, 2, or 3, wherein the dynamic rigidity nonuniform portion is provided in an annularly formed elastic body.