JPH0515153B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the wave number of vibration waves of a vibration wave motor driven by progressive vibration waves.

As disclosed in, for example, Japanese Patent Laid-Open No. 52-29192, a vibration wave motor converts the vibration motion generated when a frequency voltage such as alternating current or pulsating current is applied to an electrostrictive element into rotational motion or one-dimensional motion. It is something that converts. Compared to conventional electromagnetic motors, this motor does not require windings, so it has a simpler and smaller structure, and has the advantage of providing high torque even when rotating at low speeds and having a small moment of inertia. Therefore, it has been attracting attention recently.

The vibration wave motor known from the above publications uses standing vibration waves generated in the vibrator to frictionally drive a moving body such as a rotor in one direction when it converts vibration motion into rotational motion. The vibrating body and the movable body come into frictional contact during the forward motion of vibration, and separate during the backward motion. Therefore, the vibrating body and the movable body must have a structure in which they contact each other in a minute range, that is, a structure close to point or line contact, which results in poor friction drive efficiency.

Recently, there are vibration wave motors that have been improved in this respect and drive a moving body by friction using progressive vibration waves generated in a vibrating body.

FIG. 1 shows a schematic diagram of its main parts.

In the figure, 1 is an electrostrictive element, for example PZT (lead zirconate titanate), and 2 is a vibrating body made of an elastic material.
An electrostrictive element 1 is attached. The vibrating body 2 and the electrostrictive element 1 are held on the stator (not shown) side. Reference numeral 3 denotes a moving body which is pressed into contact with the vibrating body 2 and forms a rotor.

FIG. 2 is a side view showing the relationship between the electrostrictive element 1 and the vibrating body 2. The electrostrictive element 1 includes a plurality of elements 1a ₁ , 1
a ₂ , 1a ₃ ... and 1b ₁ , 1b ₂ , 1b ₃ ... are bonded, and one group of electrostrictive elements 1a ₁ , 1a ₂ ,
1a ₃ ..., the other groups of electrostrictive elements 1b ₁ , 1b ₂ ,
1b ₃ ... are arranged shifted by 1/4 wavelength of the wavelength λ of the vibration wave. Each electrostrictive element 1a ₁ , 1 in one group
a ₂ , 1a ₃ . . . are arranged at a pitch of 1/2 wavelength so that the polarization of adjacent ones is opposite. + and - in the figure indicate polarity. The electrostrictive elements 1b ₁ , 1b ₂ , 1b _{3 .} . . in the other group also have a pitch of 1/2 wavelength, and adjacent ones have opposite polarities. A single electrostrictive element having a size equal to the size of these electrostrictive elements arranged side by side may be prepared and then polarized to the pitch described above. Electrodes for applying voltage are deposited on both polarized surfaces of the electrostrictive element.
Formed by writing, etc.

In a vibration wave motor with such a configuration, the electrostrictive elements 1a ₁ , 1a ₂ , 1a ₃ , 1a ₄ . . . in one group have V ₀
Apply an AC voltage of Sinωt. The other group of electrostrictive elements 1b ₁ , 1b ₂ , 1b ₃ , 1b ₄ ... has V ₀ Cosωt
Apply an AC voltage of Therefore, each electrostrictive element has a phase shift of 180 degrees with respect to the polarization direction between adjacent elements, and alternating current voltages with a phase shift of 90 degrees between the two groups are applied, causing stretching vibration. This vibration is transmitted to the vibrating body 2, which bends and vibrates in accordance with the arrangement pitch of the electrostrictive element 1. When the vibrating body 2 protrudes at the position of every other electrostrictive element, the position of every other electrostrictive element retracts. On the other hand, as described above, one group of electrostrictive elements is at a position shifted by 1/4 wavelength from the other group, and the phase of the bending vibration is shifted by 90 degrees, so the vibration waves are synthesized and propagate. While the AC voltage is applied,
The vibrations are excited one after another and are transmitted through the vibrating body 2 as progressive bending vibration waves.

The progress state of the waves at this time is shown in Figure 3 a, b, c,
It is shown in d. The progressive bending vibration wave is now pointing to arrow X.
Suppose you move in the direction. 0 is the center plane of the vibrating body in the resting state, and in the vibrating state it is in the state shown by the chain line 6,
The stress due to bending is balanced on this neutral plane 6.
Looking at the cross section 7 perpendicular to the neutral plane 6, no stress is applied to the intersection line 5 of these two surfaces, and the cross section only vibrates vertically. At the same time, the cross section 7 is pendulum vibrating left and right about the intersection line 5. In the state shown in FIG. 5A, a point P on the intersection line between the cross section 7 and the surface of the movable body side 1 of the vibrating body 2 is the right dead center of left-right vibration, and only upward movement occurs. In pendulum vibration, when the intersection line 5 is on the positive side of the wave (above the center plane 0), stress is applied to the left (in the direction opposite to the wave's progress), and when the intersection line 5 is on the negative side of the wave (also below), stress is applied to the right. directional stress is applied.
That is, in the figure a, when the intersection line 5' and the cross section 7' are in the former state, stress F' is applied to the point P', and when the intersection line 5'' and the cross section 7' are in the latter state, the stress F' is applied to the point P'. join. The waves progress,
As shown in b, when the intersection line 5 comes to the positive side of the wave, point P moves to the left and at the same time moves upward. At c, point P moves only to the left at the top dead center of vertical vibration. In d, there is a leftward movement and a downward movement. The wave further advances, moving to the right and downward,
After moving to the right and upward, it returns to state a. When this series of movements is combined, the point P is moving in a spheroid. As shown in Figure c, on the line where point P touches the moving body 3, the movement of the point P causes the moving body 3 to move.
Frictionally driven in the X′ direction.

Vibration wave motors driven in this manner have not yet achieved sufficient drive efficiency. The present inventors conducted various experiments and considered the cause of the problem. As a result, they discovered that one of the causes was that the peaks of the waves on the vibrating body were in contact with the moving body at multiple points. In conventional vibration wave motors,
Since the arrangement pitch of the electrostrictive element with respect to the vibrating body is set as described above, the wavelength becomes as expected. However, it is not set how many wave numbers of that wavelength occur in the vibrating body. Many waves are generated on the vibrating body, and the peaks of the waves come into contact with the moving body at multiple points. However, due to non-uniformity in the materials of the electrostrictive element and the vibrating body, the amplitude of the waves is also not constant. Therefore, there is a peak of the wave that does not come into contact with the moving object, and the entire wave does not participate in driving. Therefore, efficiency deteriorates.

Even if a vibrating body is pressed against the moving body in order to bring the full wave into contact with the moving body, efficiency does not improve. This is because, as shown in FIG. 4, the velocity of the X'-direction component of the spheroidal motion is different between the peak A of the wave and the slightly shifted point B. It is difficult to improve the accuracy of the electrostrictive element, vibrating body, and moving body in order to uniformly contact many waves with the moving body. This is especially difficult when the wavelength is short and the amplitude is small.

The present invention was made in view of the above-mentioned facts, and an object of the present invention is to provide a vibration wave motor with high drive efficiency by improving the structure of the vibrator.

In order to achieve this object, the present invention applies a frequency voltage to an electrostrictive element, and uses progressive vibration waves generated in a vibrating body connected to the electrostrictive element to drive a moving body connected to the vibrating body. The vibration wave motor is characterized in that a progressive vibration wave generated in the vibrating body has a wave number of 3.

The embodiments shown in the drawings will be described in detail below to clarify the structure of the present invention.

FIG. 5 shows an embodiment of the arrangement of electrostrictive elements of a vibration wave motor to which the present invention is applied. An electrostrictive element 1a ₁ is attached to the circumferential vibrating body 2 (omitted in this figure).
and 1a ₂ are arranged with 1/2 wavelength width each. The electrostrictive elements 1b ₁ and 1b ₂ are also arranged with a 1/2 wavelength width. The electrostrictive elements 1a ₁ and 1a ₂ and the electrostrictive elements 1b ₁ and 1b ₂ are arranged to be shifted by 1/4 wavelength, respectively. Therefore, the vibrating body 2 includes the electrostrictive elements 1a ₁ , 1a ₂ and the electrostrictive elements 1b ₁ , 1
b Not touching ₂ , the margin on one side is 1/4 wavelength and the margin on the other is 3/4 wavelength.

When an AC voltage is applied to the electrostrictive elements arranged in this way as described above, an electric current of Y=Y ₀ Sin2π(t/T) ・Sin2π(x/λ) is generated on the electrostrictive elements 1a ₁ and 1a ₂ side. On the strain elements 1b ₁ and 1b ₂ side, Y=Y ₀ Sin{2π(t/T)−π/2} ・Sin{2π(x/λ−π/2}) (T is period, t is time, A standing wave is generated where λ is the wavelength, x is the position on the circumference, and Y ₀ is the amplitude. These two standing waves are generated one after another and are combined to form a traveling wave. At this time, the traveling wave The number of waves is 3 per revolution of the vibrating body 2. That is, the peak of the wave of the vibrating body 2 drives the movable body 3 while supporting it at three points.

Therefore, there is no gap between the peak of the wave of the vibrating body 2 and the movable body 3, and all the waves drive the movable body 3, improving driving efficiency.

Since the wave number is small (the wavelength is long), the amplitude increases accordingly. Therefore, it is not necessary to improve the surface precision of the electrostrictive element, vibrating body, and moving body as much as in the conventional ones, and the manufacturing is easy. Vibration waves occur not only in the circumferential direction of the vibrating body but also in the width direction, and vibration waves in the width direction adversely affect the drive of the moving body. Since the wavelength is longer than the length of the vibrating body in the width direction, vibrations in the width direction are less likely to occur. Therefore, generation of vibration waves that have an adverse effect can be suppressed.

FIG. 6 shows an arrangement of electrostrictive elements in another embodiment of a vibration wave motor to which the present invention is applied. In this example, two electrostrictive elements 1a ₁ and 1a ₂ each have a ratio of 1/
Three electrostrictive elements 1b ₁ and 1b ₂ arranged with two wavelength width
and 1b ₃ are arranged with a 1/2 wavelength width each. The electrostrictive elements 1a ₁ , 1a ₂ and the electrostrictive elements 1b ₁ , 1b ₂ , 1b ₃ are arranged with a shift of 1/4 wavelength, respectively. Therefore, the vibrating body 2 includes the electrostrictive elements 1a ₁ , 1a ₂ and the electrostrictive elements 1b ₁ ,
The margin on one side not touching 1b ₂ and 1b ₃ is 1/4 wavelength,
The other margin is also 1/4 wavelength. The number of waves generated in the vibrating body is three. In the present invention, since the number of vibration waves generated in the vibrating body is three, the surface accuracy of the vibrating body, the surface accuracy of the electrostrictive element as an electro-mechanical energy conversion element, and the surface accuracy of the moving body are as low as those of the conventional one. There is no need for high precision, and therefore the vibration wave motor can be manufactured at low cost.Also, since the number of vibration waves is 3, it is possible to control the moving object as an object compared to the case of 1 wave or 2 waves. It can be stably supported and driven. Note that 2 is the vibrating body, 3 is the object, 1a ₁ , 1
Each of a ₂ , 1b ₁ , 1b ₂ , and 1b ₃ constitutes a conversion element.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the main parts of a vibration wave motor, Figure 2
4 is a diagram explaining the driving principle of a vibration wave motor, FIG. 5 is a diagram showing an example of an arrangement of electrostrictive elements of a vibration wave motor to which the present invention is applied, and FIG. 6 is a diagram showing another implementation. It is the same figure as an example. 2 is a vibrating body, 3 is a moving body, 1a ₁ , 1a ₂ and 1
b ₁ and 1b ₂ are electrostrictive elements, and λ is a wavelength.

Claims (1)

[Claims] 1. A vibrating body 2, an object 3 in contact with the vibrating body 2 and driven by the vibrating body 2, and electro-mechanical energy conversion elements 1a ₁ , 1a ₂ , 1 that excite the vibrating body 2
b ₁ , 1b ₂ , 1b ₃ , and the conversion elements 1a ₁ , 1a ₂ , 1b ₁ , 1b ₂ , 1b ₃ vibrate so as to excite three vibration waves in the vibrating body 2. A vibration wave motor placed on the body 2.