Temperature compensated piezoelectric buzzer

摘要

A buzzer includes a piezoelectric diaphragm and a housing enclosing the diaphragm and defining a resonating chamber. The chamber includes a sound port and has an optimal resonating frequency fHt at a temperature T defined by fHt=(vt/2π)(√(A/voL)) were vt is the velocity of sound waves in air at a temperature T, A is the effective area of the sound port, vo is the volume of the resonating chamber, and L is the effective length of the sound port. A temperature compensating member moves in response to changes in temperature to change the value of √(A/voL) at a rate and in a manner that balances the change in 1/vt across that same temperature range, thereby reducing changes in the product (vt/2π)(√(A/voL)) and consequently reducing any changes that would otherwise occur in fHt across that temperature range, thereby holding the value of fH substantially constant across the temperature range.

主权项

1. A piezoelectric buzzer, comprising:
a) a diaphragm that can be vibrated by a piezoelectric material powered by an electric current to produce a buzzing sound; b) a housing substantially enclosing said diaphragm, wherein said housing defines a resonating chamber that includes at least one sound emission port that provides a passageway for sound waves emitted by the diaphragm to leave the resonating chamber, and wherein said resonating chamber has an optimal resonating frequency at a temperature T defined by:
fH=v/2π(√(A/voL)) wherein: v is the velocity of sound waves in air at a temperature T,
A is the effective area of the sound emission port,vo is the volume of the resonating chamber, andL is the effective length of the sound emission port; and c) a bimetal temperature compensator that moves in response to a change in temperature across a temperature range of at least 200° C. to reduce the value of √(A/voL) at substantially the same rate as the value of 1/v changes in response to that same temperature change, and thereby to hold the value of fH substantially constant across said temperature range.