JPH0474951B2 - - Google Patents

Description

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

An object of the present invention is to provide a novel vibration wave motor as described above, which has an extremely simple structure.

In order to achieve the above object, the present invention has a plurality of electrostrictive elements 3a and 3b arranged and bonded with a phase difference on the outer surface 2a of a hollow truncated cone-shaped annular vibrating body 2, and each of the electrostrictive elements Applying a frequency voltage to 3a and 3b to generate a progressive vibration wave in the vibrating body 2,
This vibration wave motor is characterized in that the vibration waves frictionally drive a movable body 1 brought into pressure contact with the vibrating body 2.

FIG. 1 is a partially cutaway side view of a vibration wave motor to which the present invention is applied.

A vibration absorber 4 made of felt or rubber is attached to the stepped portion of the fixed cylinder 5 serving as the base, and an electrostrictive element 3 as an electro-mechanical energy conversion element is attached thereto.
A metal vibrating body 2 is attached to which the metal vibrating body 2 is bonded, and each is made so that it does not rotate. A thrust roller bearing 10 consisting of rollers 9 and seats 6 is pressed by an adjustment ring 7 screwed onto a fixed cylinder 5 and a spring 8, and presses a rotating body 1 as a movable member against the surface of a vibrating body 2.

FIG. 2 shows a disassembled state of the vibrating body 2 and electrostrictive element 3 of the vibration wave motor having the above structure.

The annular vibrating body 2 made of metal has a hollow truncated cone shape, and a plurality of electrostrictive elements 3 are bonded to its outer surface 2a. The reason why the vibrating body 2 is shaped like this is because the inner diameter D ₁ and the outer diameter D ₂ of the vibrating body 2 are
While it is necessary to minimize the difference between
This is to ensure a sufficient axial width of the electrostrictive element 3 and a sufficient contact area between the vibrating body 2 and the rotating body 1 to obtain high torque. However, the cylindrical shape is not preferable because the mechanism for pressing the rotating body 1 against the vibrating body 2 becomes complicated.

The electrostrictive element 3 consists of two groups of elements, a plurality of electrostrictive elements 3a and a plurality of electrostrictive elements 3b, each of the electrostrictive elements 3a is arranged at a pitch of 1/2 of the wavelength λ of the vibration wave, and the electrostrictive elements 3a are arranged at a pitch of half the wavelength λ of the vibration wave. The elements 3b are also arranged at a pitch of λ/2. Note that a plurality of electrostrictive elements 3a (or 3b) may be used as a single element without arranging them, and the element may be polarized at the pitch. The mutual pitch between the electrostrictive elements 3a and 3b is (n ₀ +1/4)λ (correct n ₀ =0, 1, 2,
3...) A shifted phase difference arrangement is made. A lead wire 11a is connected to the absorber 4 side to each of the electrostrictive elements 3a, and a lead wire 11b is connected to each of the electrostrictive elements 3b.
are connected, each of which has a power supply 6a and a 90° phase 6b.
(See Figure 3). Further, a lead wire 11c is connected to the metal vibrating body 2 and connected to an AC power source 6a.

The operation of the vibration wave motor configured as described above is as follows.

FIG. 3 shows how vibration waves are generated in the motor. Electrostrictive element 3 bonded to metal vibrating body 2
a and 3b are shown adjacent to each other for convenience of explanation, but since they satisfy the above-mentioned phase shift condition of λ/4, the electrostrictive elements 3 of the motor shown in FIG.
This is substantially equivalent to the arrangements a and 3b.
The graphs in each of the electrostrictive elements 3a and 3b extend when the alternating current voltage is on the positive side, and contract when the AC voltage is on the positive side.

The metal vibrating body 2 is used as one electrode of the electrostrictive elements 3a and 3b, and the electrostrictive element 3a is supplied with V from the AC power source 6a.
An AC voltage of =V ₀ sin ωt is applied to the electrostrictive element 3b, and λ/
An AC voltage of V ₀ sin (ωt±π/2) with a four-phase shift is applied. + or - in the equation is switched by the phase shifter 6b depending on the direction in which the moving body 1 (omitted in this figure) is moved, and when switched to the + side, the +90° phase shifts to the positive direction. When it moves and switches to the - side, the -90° phase slips and it moves in the opposite direction. Now switched to the negative side, the electrostrictive element 3b has V=V ₀ sin
Assume that a voltage of (ωt−π/2) is applied. If the electrostrictive element 3a alone vibrates with the voltage V=V ₀ sinωt, vibrations due to the presence as shown in figure a will occur, and only the electrostrictive element 3b will vibrate with the voltage V=V ₀ sinωt alone.
When the vibration is caused by (ωt−π/2), vibration due to a standing wave as shown in b occurs. When the two phase-shifted alternating currents are simultaneously applied to each of the electrostrictive elements 3a and 3a, the vibration waves become progressive. A is time t=
2nπ/ω, B is t=π/2ω+2nπ/ω, C is t=
π/ω+2nπ/ω, D is when t=3π/2ω+2nπ/ω, and the wavefront of the vibration wave advances in the x direction.

Such progressive vibration waves are accompanied by longitudinal waves and transverse waves, and as shown in FIG.
If we pay attention to this, it is rotating in a counterclockwise elliptical motion with a vertical amplitude u and a lateral amplitude w. Since the movable body 1 is in contact with the surface of the vibrating body 2 and is in contact only with the apex of the vibrating surface, it is driven by the component of the longitudinal amplitude u of the elliptical motion of the mass points A, A'... at the apex. Then, the moving body 1 moves in the direction of arrow N.

If the phase is shifted by +90° using a 90° phase shifter, the vibration wave will proceed in the 1x direction, and the moving body 1 will move in the opposite direction to the N direction.

As described above, the vibration wave motor driven by progressive vibration waves can be switched between forward and reverse directions with an extremely simple configuration.

In addition, the velocity at the apex of mass point A is V = 2πfu
(f is the frequency), and the moving speed of the moving body 1 depends on this, and also depends on the lateral amplitude W because it is driven by friction due to pressurized contact. That is, the moving speed of the moving body 1 is proportional to the magnitude of the elliptical motion of the mass point A, and the magnitude of the elliptical motion is proportional to the voltage applied to the electrostrictive element.

Since the frictional drive of the moving body 1 is performed at the apex of the wave surface of the progressive vibration wave of the driving body 2, the resonance of the wave surface in the direction of the apex (Z-axis direction in Figure 4) improves drive efficiency. It is necessary to do so.

Since the vibrating body 2 in the embodiment is annular, the ring diameter D of the vibrating body 2 must satisfy the relationship: wavelength λ=π/nD (n is a natural number) for resonance to occur.
However, the center diameter D of the ring is the average diameter of the inner diameter D ₁ and the outer diameter D ₂ of the ring, and has a relationship of D=(D ₁ +D ₂ )/2.

In order to achieve efficient resonance, it is necessary to minimize the difference between the inner diameter D ₁ and outer diameter D ₂ of the ring.
Therefore, as mentioned above, the vibrating body 2 is shaped like a truncated cone.

As explained above, since the vibration wave motor of the present invention utilizes progressive vibration waves, it can easily be switched between forward and reverse directions by simply changing the timing of shifting the phase of the applied AC voltage. Since the vibrating body 2 has a truncated conical shape, the difference between the inner diameter and the outer diameter of the vibrating body 2 can be reduced while the width of the piezoelectric element 3 remains wide, and dynamic efficiency can be improved. In addition, since the rotating body 1 and the vibrating body 2 come into contact with each other at the conical surfaces, an alignment effect occurs that automatically brings the centers of the two closer together, resulting in smooth rotation.
The larger contact area improves rotational efficiency and reduces wear due to friction.

The above-mentioned vibration wave motor can be used as a drive source for all types of equipment, including driving the aperture, zoom, etc. of lens barrels of still cameras, cine cameras, television cameras, and the like.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway side view of an embodiment of a vibration wave motor to which the present invention is applied, FIG. 2 is an exploded enlarged perspective view of the vibrating body and electrostrictive element of the vibration wave motor of the present invention, and FIG.
FIG. 4 is an explanatory diagram of the operating principle of the vibration wave motor. 1 is a moving body, 2 is a vibrating body, 3 is an electrostrictive element, and 4 is a vibration absorber.

Claims (1)

[Claims] 1. A vibration wave motor having an annular vibrating body 2 and a movable element 1, the vibrating body 2 having a hollow truncated conical shape, and having a plurality of electrical-mechanical energy converters joined to an outer peripheral surface 2a. Element 3
a, 3b to generate progressive vibration waves on the surface, and the movable element 1 is driven by being pressed against the inner circumferential surface of the vibrating body 2.