JPS6389079A - Oscillatory-wave motor - Google Patents

Abstract

PURPOSE:To stabilize the pressurization of a vibrator, and to increase an output and improve efficiency by constituting the shape, size and material of the vibrator for a progressive wave type oscillatory-wave motor under specific conditions. CONSTITUTION:An oscillatory-wave motor is organized of a ring-shaped piezoelectric element 1, a ring-shaped elastic body 2, a cylindrical moving body 3, a ring-shaped fixing body 4, a circular pan-shaped connecting member 5, etc. The ring-shaped elastic body 2 is constructed of a main vibrating section 2a, an auxiliary vibrator 2b and a fixing section 2c, the mode of Vibrations of the elastic body 2 is an expansion mode, and the mode of vibrations is selected as shown in formula when width in the axial direction of the vibrator is represented by (h) (where R represents the central radius of the vibrator, (b) the radial width of the vibrator, nu a Poisson's ratio, K wave number and thetathe angle of thread). Accordingly, the pressurization of the vibrator can be stabilized, and an output can be increased and efficiency improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention uses progressive vibration waves generated in a ring-shaped vibrating body to frictionally and rotationally drive a mobile body that is in pressurized contact with the ring-shaped vibrating body. This invention relates to a type of traveling wave vibration wave motor.

(Background of the Invention) A vibration wave motor uses vibrational motion that occurs in a vibrating body when a frequency voltage is applied to an electro-mechanical energy conversion element (hereinafter referred to as a piezoelectric element) such as a piezoelectric element, an electrostrictive element, or a magnetostrictive element. It is used to drive moving bodies, and compared to conventional single-magnetic motors, it does not require windings, so it has the advantage of being simpler and smaller in structure, and can obtain high torque even when rotating at low speeds, and has attracted attention in recent years. ing. Among them, what is called a ring-shaped traveling wave vibration excitation wave motor generates a standing wave whose phase is shifted by 90 degrees in a ring-shaped vibrating body in terms of time by 90".
The superposition of these standing waves generates a traveling wave that travels in the circumferential direction of the vibrating body, and a moving body that is in pressure contact with this is caused by the traveling wave (actually, the traveling wave It's something that grazes in the opposite direction.

Ring-shaped traveling wave vibration wave motors include the so-called surface-facing type, in which the vibrating body and the 8-moving body are in contact with each other in a plane perpendicular to the rotation of the motor (center axis of the ring-shaped vibrating body), and the vibrating body skipping type. There is a so-called circumferentially opposed type in which the moving body contacts the inner and outer cylindrical surfaces of the motor around its rotation axis, but the former has been the mainstream in the past. The reason for this is that in the latter case, since the cylindrical surfaces are in contact, it is difficult to pressurize the vibrating body and the moving body uniformly, the structure is complex and high machining accuracy is required, and furthermore, it is difficult to excite the desired vibration. This is because a cylindrical piezoelectric element is required, which is extremely difficult to process.

Furthermore, a vibration wave motor of the circumferentially opposed type in which the vibrating body and the movable body are screw-fitted has been proposed, but the optimum screw thread angle and axial direction of the vibrating body to increase efficiency are not well understood. Futa.

(Objective of the Invention) An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional example in a circumferentially opposed traveling wave type vibration wave motor, and at the same time, to further increase output and efficiency.

(Summary of the Invention) A vibration wave motor of the present invention includes a ring-shaped elastic body having a thread on the inside or outside, a means for generating a progressive vibration wave that travels in the circumferential direction in the ring-shaped elastic body, and and a movable body that is in a screw-fitting relationship with the ring-shaped elastic body and is driven by progressive vibration waves generated in the ring-shaped elastic body, and the vibration mode excited in the ring-shaped vibrating body is a stretching mode, and the ring-shaped It is characterized by the width of the vibrating body in the axial direction.

(However, R is the central radius of the ring-shaped vibrating body, b is the radius in its radial direction, ν is Poisson's ratio, K is the number of waves riding on the entire circumference of the ring-shaped vibrating body, and θ is the thread angle of the screw.) (Embodiment of the Invention) FIG. 1 is an elevational view of the right half of the structure of a motor unit according to an embodiment of the present invention, in which 1 is a ring plate-shaped piezoelectric element;
2 is a metal ring-shaped elastic body, 3 is a cylindrical moving body, 4 is
5 is a ring-shaped fixing body, 5 is a disk-shaped connecting member, 7 is a lead wire, 8.9.10 is a fixing screw, 11.12 is a conductive paste and adhesive, and 6 is a lead wire holder.

FIG. 2 is a perspective view of the elastic body 2. FIG. The elastic body 2 consists of three parts 2a, 2b, and 2c, where 2a is a main vibrating part, 2b is an auxiliary pendulum, and 2c is a fixed part. The main vibrating part 2a is bonded to the piezoelectric element 1 at its end face, and is also what is called the main body of the vibrating body, in which a traveling wave is generated and transmitted to the trapezoidal screw part 2d provided on the inner diameter 111. .

The auxiliary system element 2b has a radial thickness that is thinner than that of the main vibration part 2a, and extends from the neutral axis position of the main vibration part 2a in the axial direction. There are three (same number as the wave number), and they are connected to the fixed part 2C.

The piezoelectric element 1 is adhered to the end face of the main S excitation part 2a of the elastic body 2 made of Bs, thereby forming a vibrating body. The elastic body 2 is fixed to the fixed body 4 at its fixing portion 2c using screws 10. A trapezoidal screw 2d (
The pitch is 0.5 mm+), and the screw surface is made of Ni.
It is hardened by plating.

The movable body 3 is provided with a trapezoidal screw 3d on its outer diameter surface, and engages with the trapezoidal screw 2d of the elastic body 2. Mobile object 3 is AI
W, and the surface of the threaded portion 3d is hard alumite treated. The movable body 3 has screws 9 attached to the disc-shaped connecting member 5.
The output of the motor can be taken out from the connecting member 5. Simply put, the principle of operation is that the piezoelectric element 1 transmits progressive vibration waves to the trapezoidal threaded portion 2d of the main vibrating portion 2a of the elastic body 2.
The movable body 3 is rotated by the contact of the screw portion and simultaneously moved in the direction of rotation @O.

FIG. 3 is a plan view of the piezoelectric element 1, in which (a) is the outer surface (front) and FIG. 3 (b) is the adhesive surface (back) of the elastic body 2 with the main vibrating portion 2a. Electrodes indicated by diagonal lines in the figure are formed on both the front and back surfaces by Ni sputtering, forming a fan-shaped pattern. The (+) and (-) marks on the back side (b) indicate that the polarization process has been performed by applying + and - DC voltages to the front side (a) in advance, respectively. When a voltage of the same polarity is applied to a region subjected to (+) polarization treatment and a region subjected to (−) polarization treatment, the expansion and contraction in the circumferential direction are opposite to each other. The electrode 1a is a fat electrode that generates one standing wave called so-called A phase, and is composed of a plurality of (+) and (-) fan-shaped electrodes each having a length λ/2 with respect to the wavelength λ (+) and (-). The circumference of the main vibrating part 2a of the ring-shaped elastic body 2 is made to be an integral number (K) times the wavelength λ of the standing wave. If K is the wave number of the standing wave riding on the Aa drive electrode 1a, the Aa drive electrode 1a forms a fan-shaped electrode group with a length of K-1)λ/2. In FIG. 3, since the wave number is 3, the A-phase drive electrode 1a is a fan-shaped electrode group corresponding to λ. Similarly, the electrode 1b is a driving electrode that generates another standing wave called the so-called B phase, and is a fan-shaped electrode group of (K-1)λ/2 like the A-phase driving electrode 1a. The A-phase and B-phase driving electrode groups 1a and Ib are spatially out of phase by 90°, that is, λ/4, and the electrode 1e exists between them. Although the electrode 1e is not directly related to motor drive, it is polarized in order to reduce the influence of distortion during the polarization process on the entire piezoelectric element.

The electrode 1c is a so-called S-phase vibration detection electrode, and is used to take out the displacement voltage due to the inverse piezoelectric effect caused by vibration, apply feedback control to the voltage applied to the A-B phase electrode and drive frequency, and use it to monitor vibration. Ru.

Similar to electrode 1e, electrode 1d is designed to reduce strain during polarization treatment. Although it has been processed, it is used here as a so-called C-phase common electrode. The back side of piezoelectric element 1 (
b) is bonded to the end face of the elastic body 2 under high pressure, and from a macroscopic perspective, the elastic body 2 and the back electrode are all in electrical contact and form an electrically integrated conductor. Elastic body 2 and surface (
The electrode 1d in a) is electrically coupled from the side with a conductive paste 11 such as Ag, and becomes a C-phase common electrode. surface(
In a), electrode 1a.

lb, Id, and Ic are lead wires 20a and 20b.

20d and 20c with a conductive adhesive 22, and serve as A-phase, B-phase, C-phase, and S-phase electrodes, respectively. Lead wires 20a-20d are coupled to an external drive circuit (not shown).

By an external power supply (not shown), V=V is applied to the A-phase drive electrode 1a with respect to the C-phase electrode. An alternating voltage of sinωt is applied, and V = V, sin (
When an alternating voltage of ωt±-) is applied, spatially λ/4
A that is mutually offset by π/2 and temporally offset from each other by π/2
As a result of the synthesis of the phase standing wave and the B-phase standing wave, a traveling wave with a wavelength λ that travels in the circumferential direction is generated in the main vibration part 2a of the elastic body 2, and the direction of the traveling wave is the same as the temporal direction of both standing waves. Switching is performed depending on the positive or negative of the above-mentioned phase difference, and the motor is rotated in the forward or reverse direction.

Here, the vibration mode generated in the main vibrating portion 2a of the elastic body 2 as described above will be explained with reference to FIGS. 6(a) and 6(b). In this embodiment, the expansion/contraction mode is used. In this mode, the displacement of the mass point is the main vibration part 2a of the ring-shaped elastic body 2.
It is a combination of longitudinal vibrations that occur in the circumferential direction and lateral vibrations that occur in the radial direction, and is like a ring-shaped combination of longitudinal vibration modes that occur in a rod-shaped vibrating body. In the displacement coordinates of the ring cross section shown in Fig. 6(a), the radial displacement U and the circumferential displacement W are u = Acos (to θ + ψ1) cos (ωt + ψ2)
−・・ 0w = KAcos (Kθ+ψ,)co
It is expressed as s(ωt+ψ2)...■. Here, A is the amplitude, K is the wave number, θ is the angular position of the ring cross section, ω is the frequency of the applied alternating voltage, and ψ1 and ψ2 are the phase shifts. FIG. 6(b) shows the displacements of U and W of the main vibrating part 2a of the ring-shaped elastic body 2, where 24a is the inner diameter of the main vibrating part 2a of the vibrating body, 24b is the center line, and 24c is the outer diameter. be. There is a radial displacement U and a circumferential displacement W, and the cross-sectional shape of the ring changes slightly due to Poisson deformation due to expansion and contraction. In FIG. 4(b), the Poisson deformation is shown extremely large for the sake of explanation. Reference numeral 25 represents the contact surface (threaded portion 3a) of the third moving body 3, which has a contact portion of several points when the wave number is K, and this moves and rotates in the circumferential direction along with the traveling wave. Therefore, if the threaded portions 2d and 3d were not used, the movable body 3 would perform only rotational motion, but since the threaded portion is provided, it moves while making a screw movement in the screw feeding direction.

FIG. 4 is a schematic diagram of a cross section of the vibrating body in the expansion/contraction mode. 18 is a vibrating body and corresponds to the main vibrating section 2a.

The vibrating body 18 has a radius of R, a radial width of b, and an axial width of h.

In order to explain the vibration state of the expansion and contraction mode, ■.

■In the formula, for simplicity, if we set ψ1=ψ2=0゜1=0, then u = Acos Kφ, w = KAcosKφ
□ ■If the radial displacement at the contact point p of the corner of the vibrating body 18 with the moving body is ΔU, and the axial displacement Δ・l, taking Poisson deformation into consideration, □ ■ Here, ν is Poisson's ratio. .

Therefore, if θ is the angle between the ring surface and the screw thread on the pressing direction W side of the movable body, the displacement direction (angle) ψ of p is expressed as □ ■, and the following relationship is desired.

□ ■■Formula means that it is sufficient to tilt θ until the displacement 16 of p matches the component 17a in the direction perpendicular to the screw surface of pressurization W17 (when the equality sign in formula ■ holds true). . ■From the formula, formula 0 gives the limit in the radial direction of the vibrating body, and 0
Good output can be obtained if the shape, dimensions, and material of the vibrating body satisfy the conditions of the formula.

FIG. 5 shows actual measured data on human output characteristics of a prototype machine according to an embodiment of the present invention having the configuration shown in FIG. The horizontal axis is the axial load,
On the vertical axis, a curve 13a represents the 8th shift speed of the moving body 3 in the axial direction, and a curve 13b represents the input power (power consumption) at that time.

In the above, the shape of the screw is not limited to a trapezoidal screw, but may be a triangular screw, and the number, pitch, number of threads, length, etc. of the screw threads may be appropriately determined as necessary. In addition, a screw may be provided on the outer diameter side of the vibrating body, a screw may be provided on the inner diameter side of the ring-shaped hyperactive body to engage the two, and a screw may be provided on the inner and outer diameter sides of the ring-shaped fHL"J body. It is also possible to provide an embodiment in which these are screwed to a moving body located inside the vibrating body and a ring-shaped moving body located outside the vibrating body.

Further, although the above embodiment uses a vibrating body supported by an auxiliary vibrator, the present invention is also applicable to a type supported by a vibration absorber such as felt.

(Effects of the Invention) As explained above, according to the present invention, the shape, dimensions, and material of the vibrating body of a traveling wave type vibration wave motor are made to meet specific conditions, thereby stabilizing the pressurization of the vibrating body. This makes it possible to increase output and efficiency, and furthermore, the number of motor components is small, making it low cost and compact.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the motor unit configuration according to an embodiment of the present invention, Fig. 2 is a perspective view of the elastic body in Fig. 1, and Fig. 3 (a).
, (b) is a plan view of the pressure T4 element in the above embodiment, Fig. 4 is a schematic diagram of a cross section of the vibrating body, Fig. 5 is a measured graph of input/output characteristics of the embodiment of the present invention, Fig. 6 (a), (b) is an explanatory diagram of the operation in the expansion/contraction mode. 1 is a piezoelectric element, 2 is an elastic body, 3 is a moving body, 4 is a fixed body,
2a is the main vibrating part, 2b is the auxiliary vibrator, 2c is the fixed part. [9f] Figure 6(b)

Claims (1)

[Claims] 1. A ring-shaped elastic body having a thread on the inside or outside;
a means for generating a progressive vibration wave that propagates in the circumferential direction in the ring-shaped elastic body;
a moving body driven by progressive vibration waves generated in the ring-shaped elastic body, the vibration mode excited in the ring-shaped vibrating body is a stretching mode, and the width h in the axial direction of the ring-shaped vibrating body is h≦{(2πR)/(νK)+b}tan(π/2−θ
) A vibration wave motor characterized by the following. (However, R is the center radius of the ring-shaped vibrating body, b is its radial width, ν is Poisson's ratio, K is the number of waves riding on the entire circumference of the ring-shaped vibrating body, and θ is the thread angle of the screw.)