JPH0447754Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an alarm clock using a piezoelectric buzzer or an electromagnetic buzzer.

[Prior Art] Conventionally, for example, in systems that selectively emit multiple types of alarm tones using a common piezoelectric buzzer, changing the basic drive frequency lowers the sound pressure, so changing the modulation frequency is necessary. It is differentiated.

[Problems to be solved by the invention] Generally, the sound pressure-frequency characteristics of a piezoelectric buzzer are
As shown in the figure, the basic drive frequency is _a
Limited to. Incidentally, ₁ is the resonant frequency of the diaphragm, ₂ is the resonant frequency due to the horn effect, and the drive frequency is determined by taking into account variations depending on the product.
It is set to a frequency _a between ₁ and ₂ .
If frequencies ₁ and ₂ are set to different values, the sound pressure will decrease, so it is preferable to set them as close as possible.

If you try to drive the device at frequency _b , for example, in order to produce a different sound that is distinguishable from frequency _a , the sound pressure will drop significantly, making it impossible to obtain a loud alarm sound.

For this reason, in the past, the basic drive frequency was kept constant and the modulation frequency was changed to differentiate between sounds. However,
Even if only the modulation frequency is changed, the drawback of reduced sound pressure still cannot be eliminated. For example, if a sound pressure of 90db is obtained when continuously driven at the basic drive frequency, 8Hz
When adding a modulated wave of , the sound pressure drops to about 86db.

The present invention is designed to prevent the sound pressure from decreasing even if the basic drive frequency is changed.

[Means for solving the problem] The present invention brings the diaphragm into contact with a regulating member that defines the effective outer diameter of the diaphragm during a selection operation to select one of a plurality of drive frequencies. Alternatively, by separating the diaphragms, the effective outer diameter of the diaphragm is changed, thereby achieving the above object.

[Example] In FIG. 1, 1 is a diaphragm, and a piezoelectric vibrator 2
is fixed. Reference numeral 3 denotes a horn portion, into which the outer peripheral end of the diaphragm 1 is fixed by adhesive or the like. Reference numeral 4 denotes a holding member constituting a regulating member, and its rising portion 4a has a ring-shaped planar shape.
The outer diameter _D2 is set smaller than the effective outer diameter _D1 of the diaphragm 1. The holding member 4 is configured so that it can be lowered from the illustrated state as shown in FIG. 2 by, for example, a manual switch (not shown) and pressed against the diaphragm 1.

In the state shown in FIG. 1, the sound pressure-frequency characteristics are set to exhibit the characteristics shown in FIG. 3, and at this time, a is used as the driving frequency. Therefore, a sound with frequency a is generated at maximum sound pressure.

When changing the alarm sound, the presser member 4 is lowered by a switch as shown in FIG. 2 to press the diaphragm 1. Therefore, the effective outer diameter of the diaphragm 1 is set to _D2 , and the sound pressure-frequency characteristics at this time are set as shown in FIG. Furthermore, the driving frequency is changed to b by changing the above-mentioned switch. Therefore, the sound of frequency b is generated without reducing the sound pressure.

In this way, the effective outer diameter of the diaphragm is changed as the drive frequency is changed, so the frequencies a and b are
The sound is generated at maximum volume without reducing the sound pressure.

Note that in the above example, the presser member was moved, but the horn side may be moved.

In addition, as an alarm sound, a melody with frequencies _{1 to 2 is used in the state shown in Figure 1, and a melody with frequencies 1} to ₂ is used in the state shown in Figure 2.
It is also possible to play _two or _three melodies.

Further, in the above example, the entire periphery of the diaphragm is pressed by the pressing member, but it may be pressed at only a few points without pressing the entire periphery.

Further, the invention is not limited to piezoelectric buzzers, but can be similarly applied to electromagnetic buzzers.

Note that the present invention can also be applied to a timer that generates an alarm sound after a set time, and this is also included within the technical scope of the present invention.

[Effect of the invention] According to the invention, with the selection of the driving frequency,
Since the effective outer diameter of the diaphragm is switched by bringing the regulating member and the diaphragm into contact or apart, it is possible to selectively generate a plurality of alarm sounds without reducing the sound pressure.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing one embodiment of the present invention, Fig. 2 is a sectional view showing another operating mode of Fig. 1, and Figs. 3 and 4 respectively show sound pressure-frequency characteristics. FIG. 1... Vibration plate, 2... Piezoelectric vibrator, 4... Pressing member.

Claims (1)

[Scope of utility model registration request] An alarm clock that generates an alarm sound by piezoelectrically or electromagnetically driving a diaphragm has a regulating member that can freely come into contact with and separate from the diaphragm and that defines the effective outer diameter of the diaphragm, and has multiple types. Along with a selection operation of selecting one of the drive frequencies, the regulating member and the diaphragm are brought into contact with or separated from each other, and the effective outer diameter of the diaphragm is changed in accordance with the drive frequency selected above. An alarm clock characterized by: