JPH0569439B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Industrial Application Field The present invention relates to an alarm notification circuit that is mainly used in jar rice cookers, microwave ovens, etc., and is equipped with a self-oscillating sounding element. (b) Prior Art Conventionally, an alarm notification circuit using a self-oscillating sounding body causes the sounding body to generate sound at a constant ringing frequency in response to a signal output from, for example, a CPU. (C) Problems to be Solved by the Invention Therefore, in this type of conventional alarm notification circuit, the sounding body always sounds at a fixed pitch, so it cannot cope with cases where it is necessary to notify at multiple pitches. There was a problem. The present invention has been made in consideration of these circumstances, and provides an alarm notification circuit that uses a self-oscillating sounding body and is capable of producing sounds at different pitches. (d) Means for Solving the Problems This invention provides a sounding body formed by pasting a thin metal plate on the back side of a ceramic thin plate having two electrodes on its surface, the sounding body, and the sounding body capable of vibrating. an oscillation circuit that causes the sounding body to oscillate; a driving voltage is applied to the oscillation circuit intermittently intermittently, and the cycle is arbitrarily set while maintaining the intermittent time ratio constant; The oscillation circuit causes the sounding element to self-oscillate intermittently when the intermittent frequency of the driving voltage is lower than the resonant frequency of the sounding element, and the oscillation circuit causes the sounding element to self-oscillate intermittently when the intermittent frequency of the driving voltage is lower than the resonant frequency of the sounding element. When it is more than
The present invention provides an alarm notification circuit comprising a circuit for separately excitation oscillation of a sounding body at the intermittent frequency, the pitch of the sounding body being arbitrarily adjustable. The above self-oscillating type sounding body has an electrode 1 as shown in FIG.
When voltage is applied to the polymer of 1, ceramic thin plate 12, and metal thin plate 13, the polymer expands and contracts in a direction determined by its polarity. Therefore, when an alternating current voltage is applied to the polymer, the polymer causes bending vibration and produces sound waves. For example, a piezoelectric ceramic sounding body OS6-21D (manufactured by Sumitomo Electric Industries, Ltd.) is used. Further, this sounding body SP1 is supported by a cylindrical resonance case 14 whose resonance frequency matches the free resonance frequency of the sounding body SP1, as shown in FIG. Furthermore, the self-oscillation circuit includes, for example, a fifth
As shown in the figure, an oscillation circuit is used which is constructed by modifying the so-called common-emitter Hartley oscillator by using the equivalent inductance and equivalent capacitance of the sounding body SP1, and using a transistor Q1 and four resistors R1 to R4. A voltage E is applied to this to drive it. (E) Effect When a constant voltage is applied as a power source to the oscillation circuit, the oscillation circuit causes the sounding body to oscillate at the resonant frequency, so the alarm notification is performed at a pitch of a constant pitch. However, if the power supply voltage of the oscillation circuit is periodically interrupted and the intermittent period is changed to approach the period of the resonant frequency of the sounding body, the frequency of the sounding body is affected and changed thereby. Therefore, using the self-oscillating sounding body and its oscillation circuit, it is possible to issue alarms of various different pitches. (F) Embodiments The present invention will be described in detail below based on embodiments shown in the drawings. Note that this invention is not limited to this. FIG. 1 is an electric circuit diagram showing an embodiment of the present invention, in which 1 is a self-oscillating sounding body, 1a is a ceramic thin plate, 1b and 1c are electrodes, 1d is a metal thin plate,
2 is an oscillation circuit, 2a is a transistor, 2b, 2
c, 2d, and 2e are resistors, and 3 is a CPU that intermittently supplies the voltage from the DC power source 4 to the oscillation circuit.
In addition, in this embodiment, the self-oscillating sounding body 1 has an OS6-
21D (manufactured by Sumitomo Electric Industries, Ltd.), for transistor 2a
2SC1815 (manufactured by Toshiba), resistors 2b, 2c, 2d, 2
100KΩ, 10KΩ, 1KΩ, and 10KΩ are used for e, respectively. Figures 2a and 2b are explanatory diagrams schematically showing temporal changes in the vibration waveform Vs of the sounding body 1 when the voltage supplied from the DC power supply 4 is intermittent and applied as the voltage Vp by the CPU 3. be. In FIG. 1, when the intermittent voltage Vp is supplied from the CPU 3 to the oscillation circuit 2, if the ON period T2 of the voltage Vp is longer than the resonance period T1 of the sounding body 1 as shown in FIG. 1 is the voltage Vp that oscillates with the period T1 during the ON period T2 of the voltage Vp.
Since the presence and absence of vibration is repeated in correspondence with the period T3, the sounding body 1 emits a vibratory sound with a fundamental frequency corresponding to the period T3. Furthermore, as shown in FIG. 2b, if the on-period T2 of the voltage Vp is shorter than the resonance period T1 of the sounding body 1, the sounding body 1
While vibrating during the on-period T2 of Vp, the presence or absence of vibration is repeated in correspondence with the period T3 of the voltage Vp, and the sounding body 1 generates a vibration sound with a fundamental frequency corresponding to the period T3 of the voltage Vp. Table 1 shows an example of the results of actually measuring the frequency of the voltage Vp and the fundamental frequency of the sounding body 1 in this example.

【table】

[Table] According to Table 1, the fundamental frequency of the sounding body is the voltage
It changes almost correspondingly to the frequency of Vp, indicating that it is possible to change the pitch even in an alarm notification circuit using a self-oscillating sounding body. (G) Effects of the Invention According to the present invention, an alarm notification circuit is provided that is capable of producing sounds of different pitches using a self-oscillating sounding body. Furthermore, when the intermittent frequency of the driving voltage is lower than the resonant frequency of the sounding element, the alarm notification circuit causes the sounding element to self-oscillate intermittently, and when the intermittent frequency of the driving voltage is equal to or higher than the resonant frequency of the sounding element, Since the sounding body is separately excited to oscillate at the intermittent frequency, the setting range of the pitch to be sounded can be extremely widened.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing an embodiment of the present invention, FIGS. 2a and 2b are explanatory diagrams showing temporal changes in the input voltage of the oscillation circuit of FIG. 1 and the vibration waveform of the sounding body,
FIG. 3 is an explanatory diagram showing the operating principle of the sounding body, FIG. 4 is an explanatory diagram showing an example of a resonance case, and FIG. 5 is an explanatory diagram showing an example of an oscillation circuit. 1... Self-oscillation type sounding body, 2... Oscillation circuit, 3...
...CPU, 4...DC power supply.

Claims (1)

[Claims] 1. A sounding body formed by pasting a thin metal plate on the back side of a ceramic thin plate having two electrodes on the surface, the sounding body, a resonance case that supports and houses the sounding body so as to vibrate, and the sounding body. The oscillation circuit includes an oscillation circuit that oscillates, and a power supply that applies a drive voltage intermittently to the oscillation circuit periodically and can arbitrarily set the cycle while maintaining the intermittent time ratio constant. When the intermittent frequency of the driving voltage is lower than the resonance frequency of the sounding body, the sounding body is intermittently self-oscillated, and when the intermittent frequency of the drive voltage is higher than the resonance frequency of the sounding body, the sounding body is externally excited at the intermittent frequency. Consists of a circuit that oscillates,
An alarm notification circuit characterized in that the pitch of the sounding body can be arbitrarily adjusted.