GB2418794A

GB2418794A - Mobile phone with piezoelectric vibrator

Info

Publication number: GB2418794A
Application number: GB0421970A
Authority: GB
Inventors: James Ching Sik Lau; Guo Wei Li; Kai Cheng; Hing Po Tsang
Original assignee: Johnson Electric SA
Current assignee: Johnson Electric SA
Priority date: 2004-10-02
Filing date: 2004-10-02
Publication date: 2006-04-05
Also published as: GB0421970D0

Abstract

A mobile telephone comprises a housing 10 and a vibrator 11 in the housing characterised in that the vibrator is an elongate piezoelectric vibrator connected at one end to the housing for causing the housing to vibrate. The piezoelectric vibrator may comprise an elongate deformable metal bar 12, which may be plate-like and an elongate ceramic element 13 bonded to one or both sides of the bar, which may be polarised normal to the elements. A driving circuit and batteries may drive the vibrator, and may excite first order bending wave resonance in the vibrator. The ceramic element may be a multilayer piezoceramic element.

Description

24 1 8794

A MOBILE TELEPHONE

Field of the Invention

This invention relates to a mobile telephone. s

Background Art

Mobile telephones conventionally make use of an electro-magnetic motor to cause the mobile telephone to vibrate when set to operate in a vibration mode. These motors are relatively expensive, bulky and to some extent unreliable.

Summary of the Invention

The present invention seeks to provide a mobile telephone with an improved vibrator.

According to the present invention, there is provided a mobile telephone comprising a housing and an elongate piezoelectric vibrator connected at one end to the housing for causing the housing vibrate.

Preferably, the housing contains one or more batteries and a driving circuit for the piezoelectric vibrator.

Preferably, the piezoelectric vibrator comprises an elongate deformable metal bar and an elongate ceramic element bonded to at least one side of the bar.

Preferably, the piezoelectric vibrator has an elongate ceramic element bonded to each of two opposite sides of the bar.

Preferably, the or each elongate ceramic element is of plate-like form.

Preferably, the two elongate ceramic elements are polarised in opposite directions normal to the respective planes of the two elements.

Preferably, the driving circuit is designed to excite first order bending resonance in the vibrator.

It is thus possible to provide a mobile telephone with a vibrator of simple construction, compact size, high reliability and high efficiency.

Brief Description of the Drawings

One preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a sectional view through part of the housing of one embodiment of a mobile telephone according to the present invention, and Figure 2 is an enlarged view showing the manner of operation of the piezoelectric vibrator shown in Figure 1.

Detailed Description of the Preferred Embodiment

Referring firstly to Figure 1, there is shown therein part of the housing or shell 10 of a mobile telephone and an elongate piezoelectric vibrator 11 fixed at one end, such as by adhesive, to an interior surface of the housing 10. The location of the mount between the housing 10 and the vibrator 11 could be important as this may affect the transfer of vibrations to the housing, but this will be decided on a case by case basis according to the design of the mobile telephone and a compromise may need to be made according to available space. The mount is preferably in the form of a relatively rigid post 14 extending from the inner surface of the housing 10 so as to transfer the vibrations from the vibrator 11 to the housing 10. The post 14 spaces the vibrator 11 sufficiently from the casing to avoid the free end of the vibrator from coming into contact with the casing in use.

The vibrator 11 comprises an elongate deformable metal bar 12, typically of steel, aluminium or copper, and elongate ceramic element 13 bonded to each of two opposite sides of the bar 12.

The bar 12 is of rectangular or square cross-section and the ceramic elements 13 are of plate-like configuration. The ceramic elements 13 are polarised in opposite directions normal to the respective planes of the element 13 so that when energised i with an AC voltage signal one will expand whilst the other contracts and vice versa to cause the bar 12 to bend to and fro as shown by the arrows in Figure 2.

The vibrator 11 is powered by the battery or batteries of the mobile telephone and a driving circuit (not shown) for the piezoelectric vibrator 11 is provided within the telephone housing 10.

The driving circuit is designed to apply an AC voltage signal to the two ceramic elements 13 at a frequency (typically in the range 100 Hz to 300 Hz) which is tuned to match the natural frequency of the first order bending vibration of the vibrator 11 so as to excite first order bending resonance vibration in the vibrator 11. This will cause the free end of the vibrator 11 to bend to and fro (as shown in Figure 2) and this, together with the reaction force at its fixed end, will cause the housing 10 to vibrate.

The embodiment described above is given by way of example only and various modifications will be apparent to persons skilled in the art without departing from the scope of the invention as defined by the appended claims. For example, the vibrator may comprise an elongate deformable metal bar having an elongate ceramic element bonded to one side only of the bar. Also, the or each ceramic element may comprise two or more layers of piezoelectric material.

Claims

1. A mobile telephone comprising a housing (10) and a vibrator (11) in the housing characterized in that the vibrator is an elongate piezoelectric vibrator connected at one end to the housing for causing the housing to vibrate.

2. A mobile telephone as claimed in claim 1, wherein the housing (10) contains one or more batteries and a driving circuit for the piezoelectric vibrator.

3. A mobile telephone as claimed in claim 1 or claim 2, wherein the piezoelectric vibrator (11) comprises an elongate deformable metal bar (12) and an elongate ceramic element (13) bonded to at least one side ofthe bar.

4. A mobile telephone as claimed in claim 3, wherein the piezoelectric vibrator (11) has an elongate ceramic element (13) bonded to each oftwo opposite sides of the bar.

5. A mobile telephone as claimed in claim 3 or claim 4, wherein the or each elongate ceramic element (13) is of plate-like form.

6. A mobile telephone as claimed in claim 5, when dependent on claim 4, wherein the two elongate ceramic elements (13) are polarised in opposite directions normal to the respective planes of the two elements.

7. A mobile telephone as claimed in claim 2 or any one of claims 3 to 6, when dependent on claim 2, wherein the driving circuit is designed to excite first order bending resonance in the vibrator (11).

8 A mobile telephone as claimed in claim 3, wherein the ceramic element is a multilayer piezoceramic element.