JP2669890B2 - Vibration wave drive - Google Patents

Description

TECHNICAL FIELD The present invention relates to an oscillatory wave drive device.

[Prior Art] A vibration wave motor that generates a progressive vibration wave in an elastic body and moves a moving body such as a rotor by this vibration is small in size and can obtain a high torque at a low speed. It was adopted to drive the shooting lens of the camera.

FIG. 2 is a longitudinal sectional view of a photographing lens of a single-lens reflex camera in which a vibration wave motor is incorporated for driving a photographing lens, and 1 is an annular metallic elasticity around the optical axis L of the photographing lens. In the body, a groove 1A having a predetermined width t and a depth h is provided over the entire circumference as shown in FIG. Further, on the lower part of the elastic body 1, two driving phases of the piezoelectric element 2 such as PZT for driving are fixed by an adhesive. Ultrasonic drive signals having different phases are respectively applied to two groups of drive phases composed of the piezoelectric elements 2 as electro-mechanical energy conversion elements by a known method, and the elastic body 1 is responsive to the signals. By vibrating, a progressive vibration wave rotating 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 portion that comes into pressure contact with the upper surface of the elastic body 1. An annular vibration absorber 5 such as rubber is provided at the other end of the rotor 3 as a moving body. Reference numeral 4 denotes an annular vibration insulator formed of felt or the like. The insulator 4 receives a pressing force from two superimposed disc springs 9 via a felt base 8.

The rotor 3 is connected to the connecting plate 22 via the vibration absorber 5 described above.
Is held closely to. The annular connecting plate 22 is fixed to the output transmission body 25 with a tightening screw (not shown). The output transmission body 25 which rotates about the optical axis L as a rotation center uses the ball 10 to form a ball bearing with ball races 13 and 14. The ball races 13 and 14 are fixed to the outer tube 12 of the taking lens, and the outer tube 1
2 is connected to the fixed barrel 11 and fixed to the camera mount 19. The connecting roller 15 is fixed to the tip of the output transmission body 25, and engages with a keyway (not shown) of the moving ring 17 holding a focus lens 27 provided in the optical axis direction. The screw portion 18a of the fixed inner cylinder 18 and the screw portion 17a of the moving ring 17 are helicoid-coupled, and the moving ring 17 can move in the optical axis direction while rotating via the connecting roller 15 by the rotational movement of the output transmission body 25. Becomes

In such a configuration, the AF signal from the camera or
A driving signal from the manual ring 16 generates a progressive vibration wave in a vibrating body composed of an elastic body and a piezoelectric element by a known method, rotates the rotor 3, and finally moves the focus lens 27 in the optical axis direction, The focus is adjusted.

In such a vibration wave motor, the vibrating body has the same driving progressive vibration wave at any position on the vibrating body,
It is formed of a uniform member so as to have the same wavelength, and has a substantially uniform structure as shown in FIG.

[Problems to be Solved by the Invention] However, in the above conventional vibration wave motor,
The flatness error of the moving body or its holding member after processing causes a surface pressure ram on the contact surface between the vibrating body and the moving body,
For this reason, a traveling vibration wave having a wavelength different from that of the driving traveling vibration wave grows, and noise may be generated from a contact surface between the vibration body and the moving body.

The analysis of the traveling vibration wave having a wavelength that generates the noise reveals that the unnecessary traveling vibration wave has one wavelength or a plurality of wavelengths.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a vibration wave driving device that prevents generation of an unnecessary wave number of a progressive vibration wave without affecting the wavelength of a driving mode and does not squeal.

[Means for Solving the Problems] A structure for achieving the object of the present invention is to excite a plurality of standing waves, whose positional phases are shifted from each other, to an elastic body having a plurality of grooves formed at substantially equal pitches. In a vibration wave driving device that forms a driving progressive vibration wave in an elastic body and relatively moves the elastic body and a contact member in pressure contact with the elastic body, a driving vibration mode excited in the elastic body, When viewed in a plurality of vibration modes vibrating at different orders, if there is a groove in the elastic body corresponding to a position of an integral multiple of the half wavelength, the dynamic stiffness between the corresponding groove and another groove When a groove is not present in the elastic body at a position corresponding to an integer multiple of the half wavelength, the dynamic rigidity between the groove on both sides of the corresponding position and another groove is changed. And the vibration wave drive device.

[Operation] In the vibration wave driving device configured as described above, one standing wave in the vibration mode having a different order from the driving vibration mode is
Having a phase difference with the other standing wave, for example, if the position of an integral multiple of half wavelength of one standing wave is the antinode position of vibration, the position of integral multiple of half wavelength of the other standing wave is When changing the dynamic rigidity of the elastic body at the antinode position of this vibration,
The natural frequency of this one standing wave changes. Also, even if the groove does not match the half-wave position of the standing wave,
The same effect can be obtained by changing the dynamic rigidity of the grooves on both sides. As a result, the formation of traveling waves in this vibration mode is prevented, and noise such as squeaking can be prevented in advance.

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

The elastic body 28 according to the present embodiment is formed in an annular shape as shown in FIG. 3, and has a plurality of grooves formed on a moving body (not shown) pressing surface side 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, in order to prevent the generation of a traveling wave in an unnecessary mode, black grooves are shown in the figure. 28b, 28c, 28d, 28e, 28f, 28g, 28h, 28i, 28j, 28k, 28
Depth h of 14 grooves (l, 28m, 28n, 28o) (hereinafter referred to as deep grooves)
Is slightly deeper than other grooves 28a (total of 76), for example, 0.2 mm to change the dynamic rigidity. In addition, the vibrating body of the present embodiment is configured so that the drive mode is the 7th mode (7-wave mode) of the out-of-plane bending vibration.

Therefore, the squeal that occurs when the motor is driven is in the 3rd, 4th, 5th, and 6th (wave) because it is a lower-order mode than the drive mode.
Either of the modes, or a combination thereof, will occur. In the motor shown in the conventional example, the secondary mode was hardly generated, probably because it was unstable considering the contact state between the elastic body and the moving body.

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

The principle of forming a traveling vibration wave is formed by synthesizing two standing waves having the same wavelength (λ) and the same frequency and having a positional phase shift of λ / 4 from each other. Therefore, in order to prevent the generation of the traveling wave of the unnecessary mode, it is sufficient that the natural frequencies of the two standing waves in the unnecessary mode formed on the elastic body 28 do not become equal. Therefore, in this embodiment, The deep grooves 28b ... 28h ... 28o are formed to form the elastic body 28.
The non-uniformity of the dynamic rigidity is achieved.

In the formation of a traveling wave, the two standing waves are out of phase with each other by λ / 4. This means that if there is an antinode of one of the standing waves at an arbitrary point in the circumferential direction of the elastic body 28, There must be another standing wave node.

In the vibration wave of the fifth mode, one wavelength formed on the elastic body 28 has a pitch of 72 °. If it is assumed that five standing waves having nodes at the deep groove 28b are generated, the standing waves are located at the antinodes of the deep grooves 28e, 28h, 28i, 28j, 28m, and the elastic body corresponding to the constant wave Let 28 be the natural frequency of f _rc . Also,
If five standing waves with the deep groove 28b as an antinode are generated,
The standing waves have nodes at the deep grooves 28e, 28h, 28i, 28j, and 28m, and the natural frequency of the elastic body 28 corresponding to the standing waves is represented by f _rs
And

A traveling wave of the fifth order mode is generated, the natural frequency f _rs and f _rc and is equal to or characteristic frequency difference of both the standing _{wave, Δf r5 = | f rs -f} rc | is small Is required, and conversely, if the natural frequency difference Δf _r5 is large, the fifth-order mode traveling wave is not generated.

In general, natural frequency f _r where mass is m and rigidity is k
Is The bending rigidity k is small in the deep groove portion because the elastic plate is thin. Thus the flexural rigidity of the case of the belly position of the deep groove and k _c, the bending rigidity and k _s in the case of a node position of the deep groove, the thickness of the loop position at which a node position of the deep groove is thick Therefore, k _s > k _c, that is, f _rs > f _rc .

Therefore, the natural frequencies f _rs and f _rc in the fifth-order mode
Since the frequency is different from that of, and the difference is large, the frequency of the fifth-order mode that may cause squeal cannot be a traveling wave, and even if the frequency of the fifth-order mode is generated for some reason, Does not cause squeaking.

The effect of preventing this squeal is due to the natural frequency difference Δf.
Obviously, the larger _r5 is, the more remarkable it is.

In the above description, the unnecessary mode is the fifth mode. However, in the elastic body 28 of the present embodiment, in addition to the fifth mode, the unnecessary modes of the sixth mode, the fourth mode, and the third mode are also described. As in the case of the fifth-order mode, the formation of traveling waves is blocked.

That is, in the case of the fourth mode, the deep grooves 28b, 28f, 28g, 28i,
28k, 28l is a dynamic rigidity non-uniform, to prevent the formation of a traveling wave of 4-order modes with different natural frequencies difference Delta] f _r4 at the position of the vibration wave.

However, in this case, since the grooves formed on the elastic body 28 and having a uniform pitch of 90 perimeter are not divisible by 4, the deep groove 28
The middle position of f, 28g (same for 28k, 28l) is the center position and the pitch is 90 °, which is one wavelength of the fourth mode.

In addition, in the case of the third mode and the sixth mode, the deep grooves 28c, 28
d, 28f, 28g, 28k, 28l, 28n, 28o is a dynamic stiffness uneven, tertiary varied natural frequency difference Delta] f _r3, a Delta] f _r6 at the position of the vibration wave, traveling wave formed in the sixth-order mode Prevent.

However, also in this case, the deep grooves 28c, 28d, the deep grooves 28f, 28g,
Centering the middle of the deep grooves 28k, 28l and the deep grooves 28n, 28o, 1/2 wavelength in the 3rd mode, 1 in the 6th mode
The pitch is 60 °, which is the wavelength.

FIG. 6 shows the natural frequency difference Δf _{rn of} these nth modes.
Is obtained for each mode. c is the case of Example 1 shown in FIG. 1 (hereinafter, the deep groove pattern of FIG. 1 is abbreviated as c pattern). As can be seen from FIG. 6, 7 for driving
The natural frequency difference Δf _{r7 in the} next mode is also due to the non-uniform dynamic rigidity.
However, the amount is small. Moreover, it is generated during other noises. Third, fourth, fifth, natural frequency difference 6 order mode _{Δf r3, Δf r4, Δf r5} , have seen the anti-squeal effect is greater because towards Delta] f _r6 is greater than Delta] f _r7 in the case of the seventh-order mode . In other words, it does not adversely affect the motor drive, and squeaking hardly occurs.

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

The deep groove pattern of the elastic body 29 according to this embodiment is a groove in which the black-painted portion is slightly deeper than the other grooves 29a, for example, 0.2 mm deep. This deep groove pattern is the same as the deep groove pattern c shown in FIG. 1 except that there are no deep grooves 28c, 28d, 28n and 28o. In other words, this is a pattern in which the vibration waves of the fourth-order and fifth-order modes are less likely to become traveling waves and the generation of squeal in these modes is prevented. The natural frequency difference Δf _rn of each mode in this case is shown by A in FIG. Hereinafter, this deep groove pattern is referred to as A pattern.

In the pattern A according to the present embodiment, the natural frequency difference Δf _r6 in the 6th mode can also be increased. In addition, 7 for driving
From becoming larger than that of c pattern natural frequency difference Delta] f _r7 Also the of the following modes, is large decrease in the motor output and efficiency as compared with the vibration wave motor of c pattern, formation of a traveling wave of 6-order mode Can be prevented.

FIG. 5 shows a plan view of the elastic body 30 according to the third embodiment of the present invention.

The deep groove pattern of the elastic body 30 according to the present embodiment is a groove in which the black-painted portion is slightly deeper than the other groove 30a, for example, 0.2 mm deep. Compared with the deep groove pattern A of the second embodiment shown in FIG. 4, this deep groove pattern is a deep groove (30b), 30d, which has a pitch of 60 °, which is one wavelength of a uniform gap around the entire circumference, as a measure for preventing squeal of the sixth mode.
This is a pattern in which 30h, (30i), 30j, and 30n are added. In other words, it is the squealing prevention pattern of the third-fourth-fifth-sixth-order mode which is the simplest. The natural frequency difference Δf _rn of each mode in this case is shown by B in FIG. Hereinafter, this deep groove pattern is referred to as a B pattern. As shown in FIG.
The natural frequency difference Δf _r6 in the 6th mode was about twice as large as that in the A pattern, and the squeaking in the 6th mode was less likely to occur. Since the natural frequency difference Δf _r7 of the 7th mode for driving is larger than the A pattern, the motor output and efficiency are greatly reduced.

In each of the embodiments described above, the deep groove is 0.2 mm thicker than the other grooves.
Although the depth is deeper, the effect becomes more remarkable if the depth is further increased.

In each embodiment, the dynamic rigidity of the elastic body is changed by the deep groove. However, the dynamic rigidity of the elastic body may be changed by increasing or decreasing the added mass or the additional resistance, or the dynamic rigidity may be changed by a combination thereof. Good.

Further, not only the dynamic rigidity of the elastic body but also the dynamic rigidity of the moving body (rotor 3) shown in FIG. 2 and peripheral members such as the vibration insulator 4 and the vibration absorber 5 may be non-uniform, and the same effect can be obtained. can get.

[Effects of the Invention] As described above, according to the present invention, the natural frequency difference of the standing wave of the vibration mode of the vibration wave serving as the driving source is determined by the difference of the vibration wave that may generate noise such as squeal. Since the difference is smaller than the natural frequency difference of the vibration mode, there is an effect that generation of noise such as squealing which has been a serious problem in practice can be suppressed without adversely affecting driving.

[Brief description of the drawings]

FIG. 1 is a plan view of an elastic body showing a first embodiment of a vibration wave motor in a vibration wave driving device according to the present invention, FIG. 2 is a sectional view of a lens barrel, and FIG. 3 is a perspective view of an elastic body of the vibration wave motor. FIG. 4 is a plan view of the elastic body of the second embodiment, FIG. 5 is a plan view of the elastic body of the third embodiment, and FIG. 6 is a diagram showing the natural frequency difference of the n-th mode of the elastic body for each mode. It is the figure shown. 1,28,29,30 elastic body 2 piezoelectric element 3 rotor 28b 28i 28o deep groove 29b 29f 29k deep groove 30b 30h 30o deep groove

 ───────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akio Atsuta 770 Shimonoge, Takatsu-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Tamagawa Office of Canon Inc. In-house (72) Inventor Hiroshi Ueda 770 Shimonoge, Takatsu-ku, Kawasaki-shi, Kanagawa Canon Inc. Tamagawa Plant (56) Reference JP-A-61-116979 (JP, A)

Claims (1)

(57) [Claims] 1. An elastic body having a plurality of grooves formed at substantially equal pitches is excited with a plurality of standing waves whose positional phases are shifted from each other to form a progressive vibration wave for driving in the elastic body. In a vibration wave driving device that relatively moves an elastic body and a contact member that is in pressure contact with the elastic body, when viewed in a plurality of vibration modes that vibrate in a different order from the driving vibration mode excited in the elastic body, When a groove exists in the elastic body corresponding to the position of an integral multiple of the half wavelength, the dynamic rigidity of the corresponding groove and another groove is changed to correspond to the position of the integral multiple of the half wavelength. When the elastic body does not have a groove, the dynamic rigidity between the adjacent groove at the corresponding position and another groove is changed.