JP3190073B2 - Vibration wave motor and device with vibration wave motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric-to-mechanical energy conversion device joined to a vibrating body for supplying electric energy to vibrate the vibrating body to rotate the driving surface of the vibrating body. The vibrating body and the contact body that has come into contact with the vibrating body.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration wave motor for relatively rotating , particularly a vibration wave motor suitable for optical equipment such as a camera and office equipment such as a printer, and an apparatus provided with the vibration wave motor.

[0002]

2. Description of the Related Art Conventionally, as an ultrasonic motor as a vibration wave motor, a type in which an annular elastic body undergoes bending vibration and a lens driving moving body is driven by a frictional force, such as an AF mechanism for a camera, etc. In practical use. However, since this conventional type has a ring shape, it is relatively expensive as a unit including a pressurizing mechanism, and disadvantageous in cost for a motor which does not require a hollow. Therefore, a motor of the type shown in FIGS. 2 and 3 which is a solid type and has a simple structure such as a pressurizing system has been proposed in recent years.

Here, the motor according to the proposal will be briefly described with reference to FIGS.

FIG. 2 is a perspective view of a vibrating body of a rod-shaped ultrasonic motor, and FIG. 3 is a longitudinal sectional view showing a motor configuration diagram.

[0005] An electro-mechanical energy conversion element (hereinafter PZ)
Due to a1 and a2), the vibrating body generates a primary bending vibration as shown in FIG.

Reference numeral C denotes a bolt having a cylindrical shape with a thin upper portion. PZTa1 and a2 are sandwiched and fixed between structural members b1 and b2 as vibrating members made of metal such as brass or stainless steel having relatively small attenuation.

The shape of the cylindrical portion m is such that the displacement of the vibrating body at the time of vibration near the upper portion where it is connected to the fixing member g constituting the vibrating body
Is determined so that is small.

The moving body d is connected to the fixed member forming the vibrating body through the spring case f and the coil spring h through the bearing e, and is in pressure contact with the upper surface of the vibrating body .

The primary bending modes generated in PZTa1 and a2 are excited in two directions in the direction having a positional phase difference of 90 ° in the θ direction and are shifted by 90 ° in time. (FIG. 4) performs an elliptical motion. The direction of movement is determined by the shape of the vibrating body.
Performs elliptical motion in a plane inclined at an angle α with respect to the axis. At this time, the moving body in pressure contact is driven by friction.

[0010]

By the way, FIG.
Since the amplitude of such an ultrasonic motor is extremely small (on the order of μm), the following problems occur in consideration of actual machining accuracy. The amount of warpage shown below is defined in a direction perpendicular to the drive surface, and the direction of vibration is defined by an angle formed with a perpendicular to the drive surface.

The structural member b1 as a vibrating body is processed by a lathe or the like. As shown in FIG. 5, even when processed with high precision, a warp (x) having a flatness of about 0.2 to 0.8 μm is generated. ing. Further, the deformed shape is almost a two-fold shape represented by sin2θ. By the way, although a warp is similarly observed in an annular ultrasonic motor used for an AF actuator of a lens, the wave number generated in the vibrating body is generally large and is not as sharp as that of the rod-shaped ultrasonic motor. The reason will be described below.

FIG. 6 shows an annular ultrasonic motor (the horizontal axis is the θ coordinate of the developed annular ring). In FIG. 6A, i represents the warp shape of a 1 μm vibrator, and Status
3 shows the shape of the contact portion in a state (not vibrating).
In (b), j indicates a vibration displacement of 0.5 μm of five waves, and (c) indicates a state in which the moving body d is in contact with a superposition of both.

Similar figures are shown in FIGS. 12 and 13, but FIG.
Then, the peak position of the warp (B in the figure) and the phase difference of the vibration wave are 0, FIG. 12 shows the case of 180 °, and FIG. 13 shows the case of 90 °,
In any state, the moving body cannot make contact with all the peaks of the wave (crests: thick line in the figure), but it can be seen that the moving body comes into contact with at least one of the crests and can always obtain the driving force from the vibrating body .

On the other hand, a plurality of bending vibrations in different directions are determined.
The ultrasonic motor of the type that excites with a temporal phase difference is equivalent to one-wave drive. When the state shown in FIG. 7 is reached, the wave front indicated by the arrow C does not contact the moving body d, The body d can hardly obtain the driving force. Therefore, the motor becomes extremely inefficient.

That is, FIG. 7 (a) shows a warp deformation i, FIG. 7 (b) shows a vibration displacement j, and this composite (i + j) is shown in FIG. Do not contact with

FIG. 11 shows a vibrating body of a conventional inefficient vibration wave motor. This vibrator has a vibration direction (α)
At 60 °, the warpage of the contact surface was 0.8 μm. Also, the amplitude
The drive frequency that takes the upper limit is as high as 64.8 kHz, and heat is generated from a relatively small amplitude, so large amplitude is difficult.If an amplitude of 1.5 μm or more is generated, the internal loss of the vibrator suddenly increases, and the efficiency is significantly reduced. Or low-power driving.
Here, the vibration displacement at the contact part of the vibrating body (depending on the vibration amplitude)
Is the length a of the vector indicated by the arrow in FIG.
The magnitude of the axial displacement component is represented by the vector
The angle that the torque makes with the axis, that is, when the driving surface of the vibrating body is stationary
Let α be the angle formed by the perpendicular line to be drawn.

However, the amplitude ( movement amount a due to vibration amplitude )
Is 1.5 μm or less (a ≦ 1.5 μm), the vibration direction α = 60 °, and the warpage of the contact surface is 0.8 μm (x = 0.8 μm)
Therefore, the condition x <a · cosα is not satisfied, and there is a moment when the moving body does not contact the peak (wavefront) of the peak of the driving wave of the vibrating body. For this reason, the friction driving force is not transmitted to the moving body, and cannot be output efficiently.

By the way, when the phase relationship between the wave and the warp is as shown in FIG. 7, the condition that the wave front having a high feed rate can contact the moving body, that is, the wave front and the moving body can contact over the entire time domain. Is determined by the relationship between the amount of warpage and the magnitude of the wave amplitude.

By the way, in a motor formed in a rod shape, contact / non-contact is determined by a component in a direction perpendicular to the driving surface. In FIG. 4, when the mass point displacement of the contact portion with the rotor indicated by the arrow is a, the above-described component in the vertical direction is a · cos α, and this component only needs to be larger than the warpage amount x of the surface. .

[0020]

Therefore, the displacement determined by the contact diameter of the contacting member which comes into contact with the vibrating body and rotates relative to the vibrating body, the driving frequency, and the rotation speed of the motor specifications.
0 <x <a · c for a and the amount of warpage x determined by the size and shape of the processing machine to be used and the member b1 of the vibrating body.
If the vibration angle α is determined to be osα, an efficient motor can be realized.

The principle of the present invention has been described above by taking as an example a case where the vibrating body is warped and the contact body driving surface is not ideally warped. When the warp of the vibrating body and the warp of the contact body drive surface are in opposite phases in the phase state of the warp of the vibrator and the warp of the vibrator, as shown in FIG. It becomes severe.

In this case, if the warp of the contact body driving surface is w, then 0 < x + w <acosα.

Further, the rare, the influence of the chucking during lathing may have cause warping of three fold (Sin3shita made shape), the phase relationship between the sled and the vibration displacement of the vibrating body 17 When the wave head C
Cannot contact the contact body driving surface d, and the motor efficiency is deteriorated as described above. At this time, the conditions under which the contact body driving surface comes into contact with the wave front are the same as those described above.

Also, irregularities having a very fine pitch such as surface roughness are defined by their envelopes.

[0025]

FIG. 1 shows an embodiment of an ultrasonic motor as a vibration wave motor according to the present invention.

The ultrasonic motor as the vibration wave motor according to the present embodiment has basically the same structure as the ultrasonic motor shown in FIGS. 2 and 3, and the warpage (x) of the contact surface of the rotor R.
Have variations in the range of about 0.2 μm to 0.8 μm. On the other hand, the vibrating body is subject to power supply conditions, heat generated by the motor, etc.
Displacement obtained at the point of contact with rotor R (due to amplitude motion
The maximum amount of movement was about 1.5 μm to 2.5 μm-p.
In addition, o and p show a half amplitude.

The vibration direction (α) of the vibrator is 39
°. Here, the vibration direction (α) is the vibration method of the vibrating body.
The direction is the angle between the drive surface and the perpendicular when the drive surface is stationary. Also,
The movement amount a due to the amplitude motion due to the vibration of the contact portion of the vibrating body is
The shape of the vibrator and the voltage applied to the vibrator or the voltage
A value that changes with the wave number, etc., obtained by measurement or calculation
Is a value that can be

That is, a = 1.5 μm-2.5 μm,
α = 39 °, and the value of acos α (Z-direction component) is 1.
It is 2 μm to 1.9 μm. From this, the amount of warpage (x) satisfies a condition smaller than acos α.

When this ultrasonic motor was actually driven, a large output could be efficiently taken out.

From the above, it can be said that, in a single-wave driven ultrasonic motor, the smaller the vibration direction α is, the more practically (in an ideal plane, there is no such a thing), the more the output can be taken out. .

To do this, as shown in FIG.
What is necessary is just to give a shape such that the inclination of the deflection function shown by the one-dot chain line near the rotor contact portion is large, that is, the angle β is large.

This can be realized by reducing t and μ in the shape of the vibrating body shown in FIG. Further, even if the vibrating body has the same shape, it differs depending on the contact diameter with the rotor. For example, α ₂ shown in FIG. 1 is larger than α, and it is usually advantageous to make contact on the outer diameter side.

FIGS. 9 and 10 show examples of vibrating body shapes in which the inclination β of the axis becomes large.

In the embodiment shown in FIG. 9, the size of the t portion is reduced, the rigidity is reduced, the mass of the upper portion is increased, and β is increased.

In the embodiment shown in FIG. 10, the length H in the axial direction of the constricted portion of the vibrator is increased and β is increased.

Although the above embodiment has been described with reference to the case where the driving surface of the vibrating body which comes into contact with the rotor is planar for reasons such as easiness of processing, the same effect can be obtained even if the driving surface is tapered. Is obtained.

FIG. 14 shows a vibration having a tapered shape on the driving surface.
1 shows an example of a body .

In this embodiment, the driving surface is located at 4 degrees with respect to the axis of the vibrating body.
5 ° and the vibration direction is 48 °, so α = 3 °,
Since the flatness of the driving surface was 0.5 μm, good motor efficiency was obtained even at a vibration amplitude of 0.6 μm.

Using the motor according to the invention in FIG.
1 shows a configuration for driving a certain device.

Reference numeral 1 denotes a gear coaxially connected to the moving body 2 for transmitting a rotation output to the gear 1 to drive a device having a gear meshing with the gear 3. In order to detect the rotational position and rotational speed of the moving body 2 and the apparatus, an optical encoder slit plate 5 is disposed coaxially with the gear 3 and the position and speed are detected by a photocoupler 4.

[0041]

As described above, according to the present invention, depending on the machining accuracy of the driving surface of the vibrating body, the contact
The state where the body and the drive surface are not in contact with each other is eliminated, and the effect that the efficiency of the motor can be improved can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of an ultrasonic motor according to the present invention.

FIG. 2 is a perspective view of a conventional ultrasonic motor.

FIG. 3 is a longitudinal sectional view of a conventional ultrasonic motor.

FIG. 4 illustrates the principle of the present invention.

FIG. 5 is a diagram showing warpage of a vibrating body .

FIG. 6 is a diagram showing a warp and a vibration displacement of a vibrating body, a combination thereof, and a contact state with a rotor.

FIG. 7 is a view showing the warpage and vibration displacement of the vibrating body after a certain time has elapsed from the state of FIG.

FIG. 8 is a side view of a vibrating body according to another embodiment.

FIG. 9 is a side view of a vibrating body according to another embodiment.

FIG. 10 is a side view of a vibrating body according to another embodiment.

FIG. 11 is a side view of a conventional vibrating body .

FIG. 12 is a diagram illustrating a warp and a vibration displacement of a vibrating body, a combination thereof, and a contact state with a rotor for explaining the principle of the present invention.

FIG. 13 is a view showing a warp and a vibration displacement of the vibrating body after a certain time has elapsed from the state of FIG. 12, and a combination thereof, and a state of contact with the rotor.

FIG. 14 is a diagram of a vibrating body according to another embodiment of the present invention.

FIG. 15 is a sectional view of an apparatus using an ultrasonic motor according to the present invention as a drive source.

FIG. 16 illustrates the principle of the present invention.

FIG. 17 illustrates the principle of the present invention.

[Explanation of symbols]

a1, a2: Piezoelectric element (PZT) b1, b2: Vibration
Body structure c: Bolt with pin d: Vibrating body e: Bearing f: Spring case g: Vibrating body fixing member h: Coil spring α: Vibration direction A: Contact position with moving body x: Warpage amount a: Vibration amplitude B: Warpage Peak β: deflection angle C: vibration crest

Claims (2)

(57) [Claims] An electric signal for driving is applied to an electro-mechanical energy conversion element sandwiched by a vibrating body,
Bending vibrations in a plurality of different directions are excited with a predetermined temporal phase difference on a driving surface which is an end surface of the vibrating body, and the vibration body is driven by one-wave driving of the vibration by synthesizing the plurality of bending vibrations. A rotating motion is generated on the driving surface, and the contact body and the vibrating body that press against the driving surface at the end surface are relatively rotated, and an inherent warpage is present on the end surface of the driving surface, In the vibration wave motor, the rotational motion has a vibration direction about a mass point of the driving surface and has a vibration amplitude, wherein the bending direction of the bending vibration excited by the vibration body is the vibration direction of the vibration body at a contact portion with the contact body. Α is the angle between the drive surface and the vertical line when the drive surface is stationary, a is the amount of movement due to the amplitude motion of the vibration of the contact portion of the vibrating body, and x is the amount of warpage of the end face of the vibrating body at the contact surface with the contact body. Then, 0 <x <
A vibration wave motor driven under a condition a that satisfies a · cos α. 2. An apparatus provided with a vibration wave motor, comprising: the vibration wave motor according to claim 1 as a driving source; and a driven member driven by the vibration wave motor.