GB2044015A

GB2044015A - Piezoelectric vibration motor

Info

Publication number: GB2044015A
Application number: GB7908158A
Authority: GB
Original assignee: SP P KONSTRUKT I TEKHNOLOG BJU
Current assignee: SP P KONSTRUKT I TEKHNOLOG BJU
Priority date: 1979-03-08
Filing date: 1979-03-08
Publication date: 1980-10-08

Abstract

A piezoelectric vibration motor comprises a multistage concentrator (1) of ultrasonic vibrations whose one stage (2) contacts and takes up vibrations from a piezoelectric cell (5), while the other, driving, stage (3) contacts and drives a rotor (8) arranged coaxially with the concentrator (1). Contacting surfaces (6 and 7) of the driving stage (3) and of the rotor (8) are made tapered so as to form a taper joint. Slots (4) in the one stage (2) serve to transform longitudinal vibrations into torsional vibrations. In a second embodiment (Figure 2, not shown) the driving stage (13) is formed by a set of inclined rods. The vibration motor is mainly intended for use in sound-recording and -reproducing devices. <IMAGE>

Description

SPECIFICATION Vibration motor The present invention relates to electric motors and, more particularly, it relates to vibration motors.

This invention can be used to advantage in sound-recording and -reproducing devices, for example, in electricplayback devices.

The invention resides in that in a vibration motor comprising a multistage concentrator of ultrasonic vibrations whose one stage contacts a piezoelectric cell while the other, driving, stage contacts a rotor arranged coaxially with the concentrator, according to the invention, the contacting surfaces of the concentrator driving stage and of the rotor are made tapered such as to form a taper joint.

Such a structural arrangement of the vibration motor according to the present invention, makes for a considerably improved reliability of the vibration motor and simplified design thereof.

The present invention will now be described in greater detail with reference to specific embodiments thereof, taken in conjunction with the accompanying drawings, wherein: Figure 1 shows the vibration motor of the invention with a concentrator of longitudinal and torsional vibrations, in longitudinal section partially broken away; and Figure 2 shows the vibration motor of the invention with a concentrator of longitudinal vibrations, in longitudinal section.

Referring now to Fig. 1 of the drawings, the vibration motor according to the present invention comprises a multi-stage concentrator 1 of ultrasonic vibrations - a concentrator 1 of longitudinal and torsional vibrations in the herein described embodiment. The concentrator 1 comprises two stages 2 and 3, the former having a larger cross-sectional area. The stage 2 is made as a cylinder over the entire height of whose body slots 4 are provided through part of its depth, said slots serving to transform longitudinal vibrations to torsional ones, one of the ends of said cylinder contacting a piezoelectric cell 5.The stage 3 is a driving one, fashioned as a sleeve whose bottom is provided by the other end face of the cylindershaped stage 2 while a side surface 6 of the stage 3 is partly in contact with a surface 7 of a rotor 8 fashioned as a ring coaxial with the concentrator 1 (both said surfaces further referred to as the contacting surfaces 6 and 7 of the driving stage 3 and of the rotor 8, respectively).

The contacting surfaces 6 and 7 of the driving stage 3 of the concentrator 1 and of the rotor 8 are tapered so as to form a taper joint. The rotor 8 is pressed by a disk 9 of any conventional playback device whose embodiment is not described herein in order not to obscure the essence of the present invention.

Electrodes 10 of the piezoelectric cell 5 are connected to a high-frequency electric oscillator known to those skilled in the art (conventionally shown in the drawing).

We have described a vibration motor embodiment employing a concentrator of longitudinal and torsional vibrations. However, in the vibration motor according to the invention use can be made of a concentrator 11 (Fig. 2) of longitudinal vibrations including two stages 12 and 13. The stage 12 contacts a piezoelectric cell 14. The stage 13 is a driving one, fashioned as rods inclined towards the end face of the stage 12, end surfaces 15 of said rods contacting a surface 16 of a rotor 17 (further referred to as the contacting surfaces 1 5 and 16 of the driving stage 13 and of the rotor 17, respectiveiy).

The contacting surfaces 15 and 16 of the driving stage 13 and of the rotor 1 7 are made tapered so as to form a taper joint. The rotor 1 7 is pressed by the disk 9 of the aforementioned playback device.

Electrodes 18 of the piezoelectric cell 14 are connected to the aforementioned high-frequency electric oscillator.

The operating principle of the vibration motor according to the invention, as shown in Fig. 1, is as follows.

Upon excitation of the piezoelectric cell 5 from the high-frequency electric oscillator, ultrasonic mechanical longitudinal vibrations emerge in said cell. Longitudinal vibrations propagate in the concentrator 1 to be transformed into torsional vibrations thanks to the provision of the slots 4 in the stage 2 and to be increased as a result of difference in the cross-sectional areas of the stages 2 and 3.

In accordance with Poisson effect, nonresonant longitudinal vibrations emerge in the concentrator 1 along with resonant torsional vibrations, the amplitude of said longitudinal vibrations being considerably smaller than that of the torsional ones. Longitudinal vibrations influence the rotor 8 in the axial direction.

Superposition of longitudinal and torsional vibrations produces "helical" vibrations (i.e., vibrations directed at an angle to the end face of the rotor 8).

Owing to the provision of the taper joint between the contacting surface 6 of the driving stage 3 and the contacting surface 7 of the rotor 8, the concentrator 1 by the energy of "helical" vibrations sets to rotation the rotor 8 pressed by the disk 9 of the playback device.

The principle of operation of the vibration motor according to the invention, as shown in Fig. 2, is as follows.

Upon excitation of the piezoelectric cell 14 from the high-frequency electric oscillator, ultrasonic mechanical longitudinal vibrations emerge in said cell. The longitudinal vibrations propagate in the concentrator 11 to be increased owing to the difference in the cross-sectional areas of the stages 12 and 13. The rods of the driving stage 13 cooperate with the end face portion of the rotor 17 at an acute angle, thereby causing an asymmetry of the force of friction in the zone of contact, and, consequently, the rotation of the rotor 17.

Inasmuch as the joint between the rotor 17 and the rods of the driving stage 13 is a taper one, the collision of the rods with the rotor 17 is accompanied by additional wedging, this increasing the asymmetry of the forces of friction and, consequently, the torque.

The vibration motor according to the present invention features a simplified design and improved reliability in operation. In addition, the taper joint between the contacting surfaces of the concentrator driving stage and of the rotor makes for an increased angle of friction between the concentrator and rotor, whereby the required force of pressing can be attained at a smaller than usual mass of the rotor, and the play characteristic of bearings is eliminated.

Claims

1. A vibration motor comprising a multistage concentrator of ultrasonic vibrations whose one stage contacts a piezoelectric cell while the other driving, stage contacts a rotor arranged coaxially with the concentrator; contacting surfaces of the concentrator driving stage and of the rotor being made tapered so as to form a taper joint.

2. A vibration motor substantially as hereinbefore described with references to the accompanying drawings.