JP2672154B2 - Vibration wave drive - Google Patents

Description

The present invention relates to a vibration wave driving device such as a vibration wave motor,
In particular, it relates to the structure of an elastic body.

[Prior Art] In recent years, in a vibration wave driving device, a plurality of standing waves having different positional and temporal phases are excited in an elastic body formed in, for example, a ring shape, and as a result, an elastic traveling wave is generated in the elastic body. The vibration wave motor of the type in which the moving body is frictionally driven by pressing the moving body against the traveling wave forming surface of the elastic body is structurally advantageous in that the motor can be hollow. For example, it has been put into practical use as an AF actuator that drives a focusing lens by incorporating it in the taking lens barrel of a camera.
Proposals have also been made for use in the drive unit of high-precision positioning mechanisms.

The basic configuration of such an oscillatory wave motor is that two groups of a plurality of driving piezoelectric elements are provided on one surface of an elastic body formed in a ring shape such that the entire circumference is an integral multiple of a certain length λ. Stuck,
These piezoelectric elements are arranged in each group at a pitch of λ / 2 and alternately with opposite expansion and contraction polarities, and are arranged so that there is an odd multiple of λ / 4 between both groups. Has been done.
If an AC voltage is applied only to one of the driving piezoelectric element groups, the center point of each piezoelectric element of the group and the points every λ / 2 from that point are antinode positions, and the antinode of the antinode A standing wave (wavelength λ) of bending vibration is generated over the entire circumference of the elastic body such that the center point between the positions is the node position. Also, if an AC voltage is applied only to the other group, a standing wave is generated similarly, but the positions of the antinodes and nodes are shifted from the standing wave by λ / 4.

Then, when an AC voltage having the same frequency and a temporal phase difference of π / 2 is simultaneously applied to both driving piezoelectric element groups, the standing waves of the both are synthesized, and the elastic body advances in the circumferential direction. A traveling wave (wavelength λ) of bending vibration is generated, and at this time, each point on the other surface of the elastic body having a thickness makes a kind of elliptic motion.
Therefore, if, for example, an annular moving body is brought into pressure contact with the other surface of the elastic body, the moving body is rotationally driven by a circumferential frictional force from the elastic body. The rotation direction can be reversed by switching the phase difference of the alternating voltage applied to the piezoelectric element groups for both driving to positive or negative.

[Problems to be Solved by the Invention] By the way, if the elastic body in the vibration wave motor is a complete ring or a disk having uniform dynamic rigidity, the driving standing wave mode is degenerated, and one driving piezoelectric element is generated. Group drive (Si
The natural frequency due to the n mode) and the natural frequency due to the driving of the other piezoelectric element group (hereinafter referred to as the Cos mode) match.

However, the elastic body has fixing holes and protrusions for fixing to the fixing member, and when the elastic body has an oval shape, the dynamic rigidity of the linear portion and the circular arc portion of the elastic body is In order to prevent the difference and squeal vibration (mainly caused by the generation of low-order in-plane or out-of-plane elastic traveling waves due to the driving wave), one standing wave and the other standing wave in the unnecessary mode There is a case where the natural vibrations in the driving vibration mode Sin mode and the Cos mode are deviated due to the presence of, for example, a non-uniform dynamic rigid portion provided in the elastic body in order to make a difference in natural frequency from the wave. As a result, when trying to obtain a traveling wave by adding two standing waves, the vibration amplitudes of both standing waves are detected, and the voltage ratio applied to both drive piezoelectric element groups so that both amplitudes are equal. The vibration amplitudes of both standing waves are different, unless complicated control is performed such that the phase difference between the two vibration amplitudes is detected and the phase between the applied voltages is controlled so that the specified phase difference is achieved. Since the phase difference also does not reach the specified value, the amplitude of the traveling wave to be formed changes with time, the uniform contact with the pressed moving body cannot be maintained, and the motor output decreases.

An object of the present invention is to provide a vibration wave drive device that solves the above-mentioned problems and can improve the output with a simple configuration.

[Means for Solving the Problems] A first configuration for achieving the object of the present invention is to provide a plurality of standing waves in which electro-mechanical energy conversion means having a positional phase difference are provided and the positional phase differences deviate from each other. A plurality of constants in a vibration mode having a second wavelength different from the first wavelength of the driving vibration mode excited by the elastic body. In order to shift the natural frequency of the standing wave, in the vibration wave driving device in which the dynamic rigidity of the position corresponding to the second wavelength is partially changed, the natural frequencies of the plurality of standing waves in the driving vibration mode are changed. In order to match or substantially match, the dynamic rigidity of the position corresponding to the first wavelength is partially changed.

A second configuration for achieving the object of the present invention is to provide an electro-mechanical energy conversion means having a positional phase difference, to excite a plurality of standing waves whose positional phase differences deviate from each other, and drive progressive vibration. A vibration wave driving device having an elastic body on which a wave is formed, and a mounting means having a non-uniform dynamic rigidity for mounting is partially formed on the elastic body. In order to match or substantially match the natural frequencies, the dynamic rigidity of the position corresponding to the first wavelength of the driving vibration mode excited in the elastic body is partially changed.

A third configuration for achieving the object of the present invention is provided with an electro-mechanical energy conversion means having a positional phase difference, and excites a plurality of standing waves whose positional phases are displaced from each other to drive a progressive vibration wave for driving. In a vibration wave driving device using an elliptical elastic body having a straight line portion and a circular arc portion, the natural frequencies of a plurality of standing waves in the driving vibration mode are made to match or substantially match. Therefore, the dynamic rigidity of the position corresponding to the first wavelength of the driving vibration mode excited in the elastic body is partially changed.

The fourth configuration for realizing the object of the present invention is the third configuration described above.
In the above configuration, the first wavelength is longer in the straight line portion than in the circular arc portion.

A fifth configuration for achieving the object of the present invention is that the position corresponding to the first wavelength in each of the above-described configurations is a position that is an integral multiple of approximately 1/2 wavelength of the first wavelength. .

A sixth configuration for achieving the object of the present invention is a movement of the position with respect to the first wavelength for matching or substantially matching the natural frequencies of a plurality of standing waves in the driving vibration mode in each of the above configurations. The partial change in rigidity is to partially change the dynamic rigidity by forming a groove or a projection at a position corresponding to the first wavelength.

According to a seventh structure for achieving the object of the present invention, a plurality of grooves are formed at substantially equal pitches in the elastic body in each of the above structures, and the dynamic rigidity at a position corresponding to the first wavelength is partially provided. The groove at the position corresponding to the first wavelength is formed so as to have a dynamic rigidity different from that of the other grooves.

[Operation] In the above-described first configuration, the driving vibration mode is not affected by the partial change in the dynamic rigidity at the position corresponding to the second wavelength in order to prevent the occurrence of squeal. , Can be driven efficiently.

In the above-described second configuration, the member for fixing the elastic body to the elastic body and the mounting means such as the mounting hole are provided, and as a result, even if the dynamic rigidity is partially uneven, the effect thereof is the driving vibration. It will fall short of the mode.

In the above-described third configuration, the elastic body has an elliptical shape, so that the driving vibration mode is not affected by the elastic body and the driving can be efficiently performed.

In the above-mentioned fourth configuration, the straight portion can be effectively used for driving.

In the fifth configuration described above, since the dynamic rigidity of the vibration in the drive vibration mode is changed, for example, at the antinode position, the natural frequency of the drive vibration mode can be effectively changed, and The natural frequencies of a plurality of standing waves in the vibration mode can be matched or substantially matched.

In the sixth configuration described above, the dynamic rigidity can be effectively partially changed with a simple configuration.

In the above-mentioned seventh configuration, for example, the groove formed for expanding the vibration amplitude is utilized to easily allow the dynamic rigidity to be partially changed.

EXAMPLES Hereinafter, the present invention will be described in detail based on examples shown in the drawings.

Embodiment 1 FIG. 1 is a plan view of an elastic body showing Embodiment 1 of a vibration wave motor to which a vibration wave driving device according to the present invention is applied, and FIG. 2 is a side view thereof.

The elastic body 1 of the vibration wave motor according to the present embodiment is formed in a ring shape, and the piezoelectric body 2 including a plurality of piezoelectric elements is fixed to one end surface thereof. The piezoelectric body 2 has two groups of driving piezoelectric elements, and a driving circuit (not shown) applies an alternating voltage of 90 ° to the driving piezoelectric element groups of both groups. A standing wave of Sin mode is generated by applying an AC voltage to the piezoelectric element group, and a standing wave of Cos mode is generated by applying an AC voltage to the other piezoelectric element group to form a traveling wave in the elastic body 1. In the present embodiment, the following description will be made on the assumption that a traveling wave of 7 waves (7λ) is formed.

On the other end surface side of the elastic body 1, in order to prevent the generation of traveling waves in unnecessary modes other than the driving seven waves and to prevent the squeal of the motor, the natural frequency of one standing wave in the unnecessary mode and the other A groove a for preventing squeal vibration for forming a difference from the natural frequency of the standing wave is formed, and the groove a is partially formed, for example, at the antinode position of one standing wave in the unnecessary mode. In addition, the rigidity of the elastic body is reduced to prevent squeal vibration.

By the way, due to the uneven dynamic rigidity due to the squeal vibration preventing groove a formed in the elastic body 1 in order to prevent the squeal vibration, both stationary in the drive mode in the drive vibration mode (30 KHz in this embodiment). A difference occurs in the natural frequency of the waves (hereinafter, this phenomenon is referred to as division), and in this embodiment, 100
As mentioned above, it was difficult to excite a uniform traveling wave due to the frequency difference of ~ 200Hz.

Therefore, in the present embodiment, in order to match the natural frequencies of both standing waves in the driving vibration mode, grooves b are formed at every one wavelength at the antinode position of the mode with the higher natural frequency (this embodiment). Is 7-wave drive, so 7).

The reason why the above division can be prevented will be described below with reference to FIG.

Assuming that the modal mass of the out-of-plane vibration is M and the modal stiffness is K, the natural frequency ω is obtained by the following equation.

When the elastic body is made thinner, the decrease ΔK in modal stiffness K is larger than the decrease ΔM in modal mass M, and therefore the natural frequency ω decreases. Further, when the elastic body is partially thinned, the Cos mode is set to a mode having a high natural frequency, and as shown in FIG. 3 (a), when the antinode position is partially thinned by the groove b for each wavelength, As shown in FIG. 3 (b), since the position of the groove b is the node position in the Sin mode, Co having the groove b at the position where the strain is large (antinode position) is used.
Since the decrease amount of ΔK in the s mode is large, the natural frequency ω
Of the Cos mode is remarkable, and if the depth and width of the groove b are changed, the natural frequencies of the Sin mode and the Cos mode will match.

FIG. 4 shows the relationship between the groove depth and the natural frequency difference Δω using the number of grooves b as a parameter, and c is the characteristic when the seven grooves b provided in the elastic body 1 are uniformly deepened. It is a figure which shows the relationship between a frequency difference and a groove depth.

Here, it is not necessary that the number of the grooves b be one for each wavelength in the anti-node of the Cos mode, and it is 14 for each half wavelength (1
It may be 0), or conversely, it may be small, for example, 1 at the antinode position, and in the case of the former with a large number of grooves,
As shown in d of the figure, the machining amount of the groove depth is small, and in the latter case where the number of grooves is small, as shown in f of FIG. 4, the natural frequency difference Δω with respect to the groove machining tolerance. The amount of change is small and the processing accuracy is rough.

In this embodiment, the position of the groove b is located at the antinode position of the Cos mode. However, as shown in FIG.
Within 1/8 wavelength, the effect of the groove b was strongly shown in the Cos mode, and the same effect could be obtained. In this case, the change in the natural frequency difference with respect to the groove depth depends on the groove shape,
When the number is the same as that of the first embodiment, it is smaller than when the groove b is provided at the antinode position as in the first embodiment.

Embodiment 2 FIG. 6 is a schematic perspective view showing Embodiment 2 of the present invention.

In the first embodiment described above, the natural frequencies of the Sin mode and the Cos mode in the drive mode divided by the squealing prevention groove a are made substantially equal by the groove b, but the strain of the driven elastic body is small. Therefore, in order to reduce the internal loss due to the vibration, in this embodiment, instead of the groove b, the protrusion 1 is provided near the neutral surface of the vibration in the elastic body 1, and the antinode or node of the standing wave of the mode having a high natural frequency is provided. A plurality of them are provided at the positions, and the natural frequencies in both modes are matched by the mass of the protrusion.

The protrusion 1 may also be used as a rotation restraining member (not shown) for the elastic body 1 or as a member for receiving pressure from a moving body (not shown).

Embodiment 3 FIG. 7 is a schematic perspective view showing Embodiment 3 of the present invention.

Although the first and second embodiments described above show an example in which the natural vibrations of both standing waves in the drive mode are divided by the squealing prevention groove a, in the present embodiment, the supporting brim 3 provided on the elastic body 1 is shown. A hole 3a for rotation restraint is formed in the hole, and the natural frequency division due to the nonuniform dynamic rigidity caused by screwing with a screw (not shown) is adjusted by the groove b in the same manner as in the first embodiment. Is.

The division of the natural frequency due to the non-uniform dynamic rigidity of the elastic body may be adjusted by providing the non-uniform dynamic rigidity portion on an elastic member support member (not shown) attached to the collar 3 with a screw.

Embodiment 4 FIG. 8 is a schematic perspective view showing Embodiment 4 of the present invention.

In the present embodiment, the elastic body 10 is formed in an oval shape, and the division caused by the difference in dynamic rigidity between the straight portion and the arc portion of the elastic body 10 is matched by the groove b.

In this embodiment, the groove b is not at right angles to the straight part of the elastic body 1 as shown in FIG. 9 (the contour lines shown in the figure show the displacement distribution in the low natural frequency mode). This is because the antinodes of the modes are not distributed at right angles.

In other words, by providing the non-uniform dynamic stiffness part according to the displacement 0 (node) distribution of the low natural frequency mode, the influence on the mode with the low natural frequency is reduced and the mode with the high natural frequency is reduced. The impact on

Fifth Embodiment FIG. 10 is a plan view of an elastic body showing a fifth embodiment of the present invention.
Figure 11 is a side view.

In the present embodiment, the neutral axis of vibration is lowered by forming a plurality of grooves at equal pitches along the circumferential direction on the surface of the elastic body 11 opposite to the surface on which the piezoelectric body 2 is fixed to form a comb tooth shape. In order to improve the motor efficiency and, among the plurality of grooves, the groove a filled in black in the figure is used for the above-mentioned squeal prevention, it is formed deeper or shallower than the other grooves, and is formed deep in this embodiment. In this embodiment, the unnecessary out-of-plane modes of 3, 5, and 6 waves are separated from the 7-wave out-of-plane mode drive.

Further, the groove b is a driving 7-wave mode division prevention groove formed by such a squealing prevention groove a, and has a different depth from the other grooves among the plurality of grooves. It has a depth intermediate to that of the other grooves.

Sixth Embodiment FIG. 12 is a plan view of an elastic body showing a sixth embodiment of the present invention.

In this embodiment, the other surface side of the elastic body 12 has a comb-tooth shape as in the case of the above-described fifth embodiment, and the hole protruding to the inner peripheral side of the elastic body 12 is used.
The vibration mode for driving (out-of-plane 4
As a measure against the splitting of the wave), among the grooves formed to improve motor efficiency, the grooves b ₁ and b ₂ are distributed as shown in Fig. 13 so that the split modes are matched. There is.

That is, assuming that the higher natural vibration mode is the Sin mode, as shown in FIG. 13 (a), the groove b ₁ (1 / 2λ pitch in this embodiment) located at the antinode position of the Sin mode is set to another groove. By making it deeper, the dynamic rigidity in Sin mode is reduced. Therefore, the natural frequency of the Sin mode is lowered. At this time, in the Cos mode, as shown in FIG. 13 (b), since the groove b ₁ is at the node position, the effect of the groove b ₁ on the natural frequency is small.

On the other hand, by making the groove b ₂ (1 / 2λ pitch in this embodiment) at the antinode position of the Cos mode, which is the lower natural vibration mode, shallower than the other grooves, the dynamic rigidity in the Cos mode is increased. Therefore, the natural frequency in Cos mode increases.

It should be noted that the grooves b ₁ and b ₂ do not need to exist at the entire circumference of the elastic body 12 at a 1 / 2λ pitch as described above, and they are in the vicinity of the antinode of each standing wave mode (within ± λ / 8 from the antinode). There may be a gap (same depth as other grooves) in the middle as long as the condition that the groove exists is satisfied.

[Effect of the Invention] In the invention according to claim 1, the driving vibration mode may be affected by partially changing the dynamic rigidity of the position corresponding to the second wavelength in order to prevent the occurrence of squeal. Without it, it can be driven efficiently.

In the invention according to claim 2, as a result of providing the member for fixing the elastic body and the mounting means such as the mounting hole to the elastic body, even if the dynamic rigidity is partially uneven, the influence thereof is the vibration for driving. It will fall short of the mode.

In the invention according to claim 3, since the elastic body has an elliptical shape, the driving vibration mode is not affected and the driving can be efficiently performed.

In the invention according to claim 4, the straight portion can be effectively used for driving.

In the invention according to claim 5, since the dynamic rigidity of the vibration in the drive vibration mode is changed, for example, at the antinode position, the natural frequency of the drive vibration mode can be effectively changed, and The natural frequencies of a plurality of standing waves in the vibration mode can be matched or substantially matched.

In the invention according to claim 6, the dynamic rigidity can be effectively partially changed with a simple structure.

In the invention according to claim 7, for example, it is possible to easily partially change the dynamic rigidity by using the groove formed for expanding the vibration amplitude.

[Brief description of the drawings]

FIG. 1 is a plan view of an elastic body showing a first embodiment of a vibration wave motor to which a vibration wave driving device according to the present invention is applied, FIG. 2 is a side view thereof, and FIGS. 3 (a) and 3 (b) show an embodiment. 1 is a diagram illustrating the principle of No. 1, FIG. 4 is a diagram showing the relationship between the natural frequency difference and the depth of the groove with the number of grooves as a parameter, FIG. 5 is a view of a modification of the first embodiment, and FIG. Example 2 schematic perspective view, FIG. 7 is a schematic perspective view of Example 3, FIG. 8 is a schematic perspective view of Example 4, FIG. 9 is a diagram illustrating the principle of Example 4, and FIG. FIG. 11 is a plan view of the fifth embodiment, FIG. 11 is a side view thereof, FIG. 12 is a plan view of the sixth embodiment, and FIGS. 13 (a) and 13 (b) are views for explaining the principle thereof. 1,10,11,12: elastic body 2: piezoelectric, 3: collar a, b, b _1, b _2: Groove l: projection.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Gen Kanazawa, 770 Shimonoge, Takatsu-ku, Kawasaki-shi, Kanagawa Canon Inc. Tamagawa Plant (72) Inventor Akio Atsuta, 770, Shimonoge, Takatsu-ku, Kawasaki, Kanagawa In-house (72) Inventor Hiroshi Ueda 770, Shimonoge, Takatsu-ku, Kawasaki-shi, Kanagawa Canon Inc. Tamagawa Plant (56) Reference JP-A-2-133076 (JP, A)

Claims (7)

(57) [Claims] 1. An elastic body provided with an electro-mechanical energy converting means having a positional phase difference and exciting a plurality of standing waves having positional phase differences different from each other to form a progressive vibration wave for driving. In order to shift the natural frequencies of a plurality of standing waves in a vibration mode of a second wavelength different from the first wavelength of the vibration mode for driving excited in the elastic body, In a vibration wave driving device in which the dynamic rigidity of the corresponding position is partially changed, in order to make the natural frequencies of a plurality of standing waves in the driving vibration mode match or substantially match, the position corresponding to the first wavelength A vibration wave driving device characterized in that the dynamic rigidity of the is partially changed. 2. An elastic body provided with an electro-mechanical energy conversion means having a positional phase difference and exciting a plurality of standing waves having positional phase differences different from each other to form a progressive vibration wave for driving. A vibration wave drive device in which the elastic body is partially formed with a mounting means that makes the dynamic rigidity non-uniform for mounting, the natural frequencies of a plurality of standing waves in the vibration mode for driving are matched or substantially matched. In order to achieve the above, a vibration wave drive device is characterized in that the dynamic rigidity at a position corresponding to the first wavelength of the drive vibration mode excited in the elastic body is partially changed. 3. An electro-mechanical energy conversion means having a positional phase difference is provided to excite a plurality of standing waves whose positional phases are shifted from each other to form a progressive vibration wave for driving. In a vibration wave driving device using an elliptical elastic body having a straight line portion and a circular arc portion, the elastic body is excited in order to match or substantially match the natural frequencies of a plurality of standing waves in the driving vibration mode. The vibration wave driving device is characterized in that the dynamic rigidity at a position corresponding to the first wavelength of the driving vibration mode is partially changed. 4. The vibration wave driving device according to claim 3, wherein the first wavelength is longer in the straight line portion than in the circular arc portion. 5. The position corresponding to the first wavelength is the first
5. The vibration wave drive device according to claim 1, wherein the vibration wave drive device is located at a position that is an integral multiple of approximately one-half wavelength of the above wavelength. 6. The partial change of the dynamic rigidity of the position with respect to the first wavelength for matching or substantially matching the natural frequencies of a plurality of standing waves in the driving vibration mode is performed in the first wavelength. A groove or a protrusion is formed at a corresponding position to partially change the dynamic rigidity.
Alternatively, the vibration wave driving device according to item 5. 7. The elastic body is formed with a plurality of grooves at substantially equal pitches, and corresponds to the first wavelength in order to partially change the dynamic rigidity of a position corresponding to the first wavelength. 7. The vibration wave drive device according to claim 1, wherein the groove at the position to be formed is formed to have a dynamic rigidity different from that of the other grooves.