JPH02280676A - Vibration wave motor - Google Patents

Abstract

PURPOSE:To suppress noise by setting the differential inherent vibration of standing wave having vibration mode lower than the differential inherent vibration which may cause noise. 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 in order to prevent generation of progressive wave in unnecessary mode and the dynamic rigidity is varied. By such arrangement, generation of unnecessary progressive vibration wave can be prevented.

Description

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

[Prior Art] Vibration wave motors, which generate progressive vibration waves in an elastic body and use these vibrations to move a rotor or other moving body, are small and can provide high torque at low speeds, so they have recently become popular in the eye. It was developed by Fukagawa to drive the photographic lens of reflex cameras.

Figure 2 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. 3, a groove IA having a predetermined width t and depth h is provided over the entire circumference on the side that contacts the rotor 3, which will be described later. Furthermore, two groups of drive phases made of piezoelectric elements 2 made of PZT or the like are fixed to the lower part of the elastic body 1 with an adhesive. Ultrasonic drive signals having 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 1 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 that presses into contact with the upper surface of the elastic body 1, and an annular vibration absorber 5 made of rubber or the like is provided at the other end of the rotor 3 as a moving body. Reference numeral 4 denotes an annular photographing 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.
is closely held. The annular connecting plate 22 is fastened to the output transmission body 25 by 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 a moving roller 15 holding a focus lens 27 provided in the optical axis/direction is attached. It engages with a keyway (not shown) in ring 17. The threaded portion 18a of the fixed inner cylinder 18 and the threaded portion 17a of the movable ring 17 are helicoidally coupled, and the movable ring 17 is rotated in the optical axis direction via the connecting rollers 15 due to the rotational movement of the output transmission body 25. It is possible to move to.

In such a configuration, an AF signal from the camera side or
A driving wJ signal from the manual ring 16 causes a vibrating body made of an elastic body and a piezoelectric element to generate progressive vibration waves by a known method, rotates the rotor 3, and finally moves the focus lens 27 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 S moving body, and is approximately uniform as shown in the third figure. 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 vibrating 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 wave 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.

SUMMARY OF THE INVENTION An object of the present invention is to provide a noise-free vibration wave motor that prevents the generation of progressive vibration waves of unnecessary wave numbers without affecting the wavelength of the drive mode.

[Means for Solving the Problems] A typical example for achieving the object of the present invention is to apply an alternating current voltage to the drive electric-mechanical energy conversion means to shift the positional phases of the elastic bodies from each other. In a vibration wave element that excites a plurality of standing waves to form 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, In at least one of the motor components including the elastic body and the pressure member that affect the formation of the elastic vibration waves, the natural frequency difference between the plurality of standing waves in the drive mode excited in the elastic body, A vibration wave motor characterized in that a dynamic stiffness non-uniform portion is provided so that the difference in frequency between a plurality of standing waves in at least one vibration mode other than a progressive vibration wave for driving is smaller than a frequency difference between a plurality of standing waves.

[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 0! It is possible to prevent the occurrence of noise such as noise.

[Embodiment] FIG. 1 is a plan view of an elastic body showing a first 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. 3, and has a plurality of grooves formed on the side of the pressing 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, 14 grooves of 28o (hereinafter referred to as deep grooves) are used to prevent the generation of traveling waves in unnecessary modes. The depth h of the grooves 28a is made slightly deeper, for example, by 0.2 mm, than the other grooves 28a (76 grooves in total) to change the 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 in a lower order mode than the drive mode, so the 3rd, 4th, 5.6th order (
It will occur as a resonance of one of the wave) modes 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, the deep grooves 28b...28h...280 are formed to The aim is to make the dynamic stiffness of 28 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 mode, one wavelength formed on the elastic body 28 has a pitch of 72 degrees. Here, if a five-wave standing wave with the deep groove 28b as a node is generated, the standing wave has an antinode position at the deep grooves 28e, 28h, 281°28j, and 2BI11, and corresponds to the standing wave. Let frc be the natural frequency of the elastic body 28. Furthermore, if five standing waves with an antinode at the deep groove 28b are generated, the standing waves are generated at the deep groove 28b.
8e, 28h, 28128j, and 28m are the node positions, and the natural frequency of the elastic body 28 corresponding to the standing wave is f,
shall be.

In order for the traveling wave of the fifth mode to occur, the natural frequencies f rl and f re of both standing waves must be equal, or the difference in their natural frequencies, 8f, -1fr, -fre, must be small. necessary, and conversely, if this natural frequency difference Δfrs is large, 5
The traveling wave of the next mode is no longer generated.

In general, the natural frequency f when mass 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,>ke, that is, f, , > fre.

Therefore, the natural frequencies f rg and f re in the 5th mode are different in frequency, and the difference is large, so the frequency of the 5th mode, where squealing may occur, can be a traveling wave. Even if the frequency of the mode occurs for some reason, it will not cause squealing.

Furthermore, the effect of preventing the generation of squeal is due to the natural frequency difference Δfr
It is clear that the larger s is, the more noticeable the difference 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, 28+, 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 receives 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, 2
8o makes the dynamic stiffness non-uniform, and the natural frequency difference Δf15. Δ
The formation of traveling waves in the 3rd and 6th modes is prevented by varying fr6 depending on the position of the vibration wave.

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 third-order mode, 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 6 shows the natural frequency difference Δf r of these first-order modes.
n is determined for each mode. , C is the case of Example 1 shown in FIG. 1 (hereinafter, the deep groove pattern in FIG. 1 will be abbreviated as C pattern). As can be seen from Figure 6, the seventh mode for driving also has a natural frequency difference Δ due to the non-uniformity of dynamic stiffness.
fr7 is produced, but its amount is small. Moreover, it occurs when other noises occur. Natural vibration a difference Δfr3+Δft4* of the 3rd, 4th, 5th, and 6th modes Δfr when Δfrs+Δfr8 is the 7th mode? Since it is larger, you can see that the noise prevention effect is great. In other words, it does not adversely affect motor drive and is less likely to generate noise.

FIG. 4 is a plan view of an elastic body showing Example 2 of the present invention.

In the deep groove pattern of the elastic body 29 according to this embodiment, the black portion is slightly deeper than the other grooves 29a, for example, 0.2 m.
It is a m deep groove. This deep groove pattern is different from the deep groove pattern C shown in FIG.
It is the same except for the absence of 8o. In other words, the vibration waves of the 4th and 5th modes become traveling waves. This pattern is effective in preventing occurrence.

The natural frequency difference Δf rn of each mode in this case is indicated by A in FIG. Hereinafter, this deep groove pattern will be referred to as A pattern.

In the A pattern according to this embodiment, the natural frequency difference Δfr15 in the sixth mode can also be increased. In addition, the natural frequency difference Δi? of the seventh mode for driving? is larger than in the case of the above-mentioned C pattern, so the decrease in motor output and efficiency is greater than that of the C-pattern vibration wave motor.
The formation of the next mode traveling wave is prevented.

FIG. 345 shows a plan view of the elastic body 30 according to the third embodiment of the present invention.

In the deep groove pattern of the elastic body 30 according to this embodiment, the black portion is slightly deeper than the other grooves 30a, for example, 0.2 mm deeper. This deep groove pattern is different from the deep groove pattern A of Example 2 shown in FIG.
30b).

This is a pattern in which 30d, 30h, (301), 30J, and 30n are added. In other words, this is the simplest possible squeal prevention pattern of the 3rd-4th-5th-6th mode. In this case, the natural frequency difference Δf rn of each mode is ′
It is indicated by B in the s6 diagram. Hereinafter, this deep groove pattern will be referred to as pattern B. As shown in Figure 6, the natural frequency difference Δfr6 of the 6th mode is about twice as large as that of pattern A, making it difficult for the 6th mode to generate squeal. Ta. Note that since the natural frequency difference Δfr7 of the seventh mode for driving is larger than that of pattern A, the motor output and efficiency are significantly reduced.

In each of the embodiments described above, the groove is 0.2 m deeper than the other grooves.
m depth, but if this depth is further increased, the effect will become even more pronounced.

Further, in each embodiment, the dynamic stiffness of the elastic body is changed by using deep grooves, but the dynamic stiffness of the elastic body can also be changed by increasing or decreasing the added mass or added resistance, or by a combination of these. good.

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 the moving body (rotor 3) shown in FIG. is obtained.

[Effects of the Invention] As described above, according to the present invention, the difference in the natural frequency of the standing wave of the vibration mode of the vibration wave serving as the driving source can be adjusted to Since it is made smaller than the natural frequency difference of the vibration modes, it has the effect of suppressing the generation of noise such as squealing, which has been a major problem in practice, without adversely affecting the drive.

[Brief explanation of drawings]

FIG. 1 is a plan view of an elastic body showing Example 1 of the vibration wave motor according to the present invention, FIG. 2 is a sectional view of a lens barrel, FIG. 3 is a perspective view of the elastic body of the vibration wave motor, and FIG. 4 is a plan view of the elastic body of Example 2, FIG. 5 is a plan view of the elastic body of Example 3, and FIG. 6 is a diagram showing the natural frequency difference of the zero-order mode of the elastic body for each mode. . 1.28.29.30...Elastic body 2...Piezoelectric element 3...Rotor 28b...281...280...Deep groove 29b...
・29f...29k...deep groove 30b...30h
・・30o・・・Deep groove No. 1 Figure Figure Figure Figure Figure Figure (llz) Mode order n

Claims (1)

[Claims] 1. By applying an alternating current voltage to the driving electric-mechanical energy conversion means, a plurality of standing waves whose positional phases are shifted from each other are excited in the elastic body, so that the elastic body has a progressive motion. A vibration wave motor that generates vibration waves and relatively moves the elastic body and a pressure member that is in pressure contact with the elastic body, the vibration wave motor including the above elastic body and pressure member that affect the formation of progressive vibration waves. At least one of the motor components
The natural frequency difference between the plurality of standing waves in the driving mode excited in the elastic body is the frequency difference between the plurality of standing waves in at least one vibration mode other than the progressive vibration wave for driving. A vibration wave motor characterized in that a dynamic rigidity non-uniform portion is provided so that the dynamic rigidity is smaller than that of the vibration wave motor.