JP2009127923A - Microwave oven - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microwave oven capable of controlling an output by detecting a spark generated during heating. <P>SOLUTION: The sound generated accompanied by the spark is guided to a microphone 10 disposed on a place of a good temperature condition by a sound guide path 11, and a sound is detected to determine the spark by a microcomputer 14 as a spark determining means and to control the motion of a magnetron 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a microwave oven having a device for detecting, by sound, sparks generated by microwave power feeding in the presence of metal contact in a heating chamber.

  A microwave oven is a device that heats food by absorbing microwaves, but sparks are generated on the metal end face, such as when metal products such as metal containers and aluminum foil are brought into contact with each other and when using metal-decorated tableware. At that time, loud sounds and sparks are generated, which may cause anxiety to the user. In addition, when sparks are generated, if the supply of microwaves is not controlled promptly, the sparks may burn into the oil of the food and produce smoke. In order to avoid such a situation, it is possible to control the microwave oven by detecting the occurrence of a spark sound with an acoustic sensor. Conventionally, there has been proposed a microwave oven that detects an acoustic variation in a heating chamber to detect a finished state of food (see Patent Document 1).

FIG. 11 is a side sectional view of a conventional microwave oven described in Patent Document 1. In FIG. Microwaves generated by the magnetron 108 are guided into the heating chamber 110 by the waveguide 109 and absorbed by the food 111. The steam generated from the food is detected by the humidity sensor 112 and the thermistor 113. In addition, the microphone 114 attached to the side surface of the heating chamber 110 detects the sound generated in the heating stage of the food 111 to detect the finish of the food 111. In addition, sounds other than the food 111 (for example, wind noise of the fan 115 and driving sound of the turntable motor 116) are detected by the microphones 117 and 118, and compared with the data of the microphone 113 that detects the finished sound of the food 111. Is done. Output data from the humidity sensor 112, the thermistor 113, and the microphones 114, 117, and 118 are input to the control unit 120 through the detection circuit 119, and the control unit 120 controls the oscillation of the magnetron 108 through the driver 121.
Japanese Patent Publication No. 3-25697

  The configuration of detecting the finish of the food 111 inside the heating chamber 110 by the conventional microphones 114, 117, 118 detects the state of the heating chamber 110 by sound, but completely considers the occurrence of a spark. It was not possible to detect the spark as it was.

  In view of the above, an object of the present invention is to provide a configuration in which a spark set is detected with a microphone installed outside a heating chamber, and a spark is detected, control of a microwave oven is stopped, and the like is detected reliably.

  In order to solve the above-mentioned conventional problems, a microwave oven according to the present invention includes a heating chamber for placing food, a magnetron for supplying microwaves for heating the food in the heating chamber, a microphone for detecting an acoustic state in the heating chamber, and And a sound guide path for guiding sound from the heating chamber to the microphone, and a signal processing means for detecting spark information in the heating chamber from the output of the microphone and a spark determination means.

  Accordingly, it is possible to detect a spark sound with a microphone installed outside the heating chamber, and to perform control such as spark determination and microwave stop.

  When a spark occurs, the microwave oven according to the present invention promptly guides the sound generated along with the spark to the microphone through the sound guide path, and detects the spark information in the heating chamber from the output of the microphone. Since the occurrence of a spark can be detected from the output of the determination means and the heating output can be reduced or stopped, the user's anxiety can be removed, and smoke generated by the spark in the heating chamber can be prevented.

  According to a first aspect of the present invention, there is provided a heating chamber for placing food, a magnetron for supplying microwaves for heating the food in the heating chamber, a microphone for detecting an acoustic state in the heating chamber, and a guide for guiding sound from the heating chamber to the microphone. It has a signal processing means for detecting spark information in the heating chamber from the sound path and the output of the microphone, and a spark determination means. When a spark occurs, the spark sound is guided to the microphone through the sound guide path and the output of the microphone. Since the signal processing means and the spark determination means can detect the occurrence of sparks and reduce or stop the heating output, the user's anxiety can be removed and smoke from the sparks in the heating chamber can be prevented. I can do things.

  The second invention has a plurality of sound guide paths for guiding the spark sound from the heating chamber to the microphone, particularly in the first invention. It makes it possible to make a judgment.

  According to a third invention, in particular, in the first to second inventions, a printed circuit board is provided at the end of the sound guide path, and a microphone is installed on the printed circuit board, and the microphone is fixed to the end of the sound guide path. Thus, the sound transmitted through the sound guide path can be reliably detected by the microphone.

  According to a fourth aspect of the present invention, in particular, in the first to third aspects of the invention, the opening portion on the side near the heating chamber of the sound guide path is opposed to the opening portion of the heating chamber wall surface through a cushioning material. For example, mechanical vibration other than the spark sound is prevented from being transmitted to the sound path, and the detection accuracy of the spark sound is improved.

  A fifth invention has a heating chamber for placing food, a magnetron for supplying microwaves for heating the food in the heating chamber, and a printed circuit board. The printed circuit board includes a heating control circuit, a microphone, and an output of the microphone. The signal processing means for detecting the spark information in the heating chamber and the spark determination means are installed, and has a sound guide path for guiding sound from the heating chamber to the microphone, and is related to the spark detection together with the heating control circuit on the same printed circuit board. Since the components can be collected and the spark sound can be reliably guided to the printed circuit board through the sound guide path, it is possible to realize spark detection with high accuracy and low manufacturing cost.

  In a sixth aspect of the invention, in particular, in the first to fifth aspects of the invention, the sound guide path is formed of a metal tube, and can transmit high-frequency sound such as spark sound with high efficiency.

  In the seventh aspect of the invention, particularly in the first to sixth aspects of the invention, the sound guide path is tapered at both ends, so that sound collection from the spark source and sound emission to the microphone can be performed efficiently. Can do.

  In the eighth invention, in particular, in the first to seventh inventions, the microphone is an electret condenser microphone, which is small in size, has good sound collection performance, and can capture sound with high efficiency even in a high frequency range. It can be detected reliably.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a partially cutaway configuration diagram of a microwave oven according to the first embodiment of the present invention.

  In FIG. 1, the microwave generated by the magnetron 1 that is a microwave generation source passes through the inside of the waveguide 2 and is supplied from the bottom surface of the heating chamber 3 to the heated object 4 inside the heating chamber 3. A fan 5 that sends cooling air for the magnetron 1, a high-voltage transformer 6, a high-voltage capacitor 7, and a high-voltage diode 8 that are components for supplying high voltage to the magnetron 1 are installed outside the heating chamber 3. In addition, a sound guide path 11 is provided outside the heating chamber 3 for transmitting a spark sound inside the heating chamber 3 to the microphone 10 through a punching hole 9 formed in the wall surface of the heating chamber 3. The output signal of the microphone 10 is input to the signal processing means 13 through the DC-cutting capacitor 12 and is subjected to signal processing. The output of the signal processing means 13 is an analog / digital conversion input of the microcomputer 14 which is a spark determination means. Input to terminal 15.

  If it is determined from the digitally converted voltage level that a spark sound is generated, it is output from the digital output terminal 16 of the microcomputer 14 and the relay circuit (not shown) is opened to stop the microwave oscillation. The spark sound generated in a state where the end surfaces of the aluminum foil 17 covered with the object to be heated 4 are in light contact with each other in the above configuration is detected by the microphone 10 and the signal is processed by the signal processing means 13 (amplification, filtering, Rectification, smoothing), the microcomputer 14 serving as a spark determination means determines that a spark has occurred, and performs a microwave oscillation stop operation.

  FIG. 2 shows a circuit diagram of the signal processing means 13.

  The DC component of the output of the microphone 10 is cut by the capacitor 12 and becomes the input of the amplifier 18, and is amplified to a voltage that does not saturate the signal because the subsequent signal processing is easy (50 times in FIG. 2). The output of the amplifier 18 attenuates a signal of 10 kHz or less via a first-stage high-pass filter 19 and a second-stage high-pass filter 20. Low-frequency sound signals such as wind noise generated by the fan 5 are removed by the cascaded high-pass filters 19 and 20. In FIG. 2, the cut-off frequency of the first-stage high-pass filter 19 is set to 9.4 kHz, and the cut-off frequency of the next-stage high-pass filter 20 is set to 14.5 kHz.

  Here, the output of the high-pass filter 20 is a signal that swings up and down with 2.5V as a reference. The half-wave rectifier circuit 21 includes diodes 22 and 23 and an operational amplifier 24, and performs half-wave rectification with an input voltage of 2.5V as a reference. The half-wave rectifier circuit output is input to a smoothing circuit 28 including a resistor 26 and a capacitor 27 via a buffer circuit 25, and the output of the smoothing circuit 28 is input to an analog / digital conversion input terminal 15 of the microcomputer 14. The

  FIG. 3 shows the frequency characteristics of the overall high-pass filter. As shown in FIG. 3, a large attenuation characteristic of about 60 dB is realized when the frequency is changed by one digit at 10 kHz or less. The reason why the high-pass filter characteristics having a pass band of 10 kHz or more is effective is that the spark sound and the sound generated in the actual cooking are analyzed as a result of the frequency analysis of the spark sound and the components having the frequency of 10 kHz or more are found to be significant. .

4 shows the waveform of the half-wave rectifier circuit 21, FIG. 4 (a) shows the input waveform, and FIG. 4 (b) shows the output waveform. The output waveform is input to the smoothing circuit 28 via the buffer circuit 25. Since the operation reference voltage of the half-wave rectifier circuit is 2.5V, the smoothing circuit also operates with 2.5V as the lowest level.

  As shown in FIG. 1, the restriction of the installation location of the microphone 10 can be removed by guiding the sound generated in the heating chamber 3 through the sound guide path 11 to an arbitrary place. In particular, there is a possibility that high-temperature steam or food debris may jump out around the punching hole 9. If the microphone 10 is installed on the immediate side even outside the punching hole 9, the function can be sufficiently performed by heat and dirt. is expected. Therefore, by installing the sound guide path 11, the performance of the microphone 10 can be ensured, and a highly reliable spark detection with a high degree of freedom of installation location can be realized.

  In the present embodiment, the hole 9 is formed in the side wall of the heating chamber 3, but the present invention is not limited to this, and is generated with microwave power feeding in the presence of metal contact in the heating chamber 3. It may be formed on the back wall, ceiling wall, or bottom wall of the heating chamber 3 as long as the spark sound can be collected.

(Embodiment 2)
FIG. 5 is a partially cutaway configuration diagram of a microwave oven according to the second embodiment of the present invention.

  The difference from the first embodiment is that a path for guiding the spark sound in the heating chamber 3 to the microphone 10 is added from the punching hole 29 at the back of the heating chamber to the microphone 10 by the sound guide path 30. By adding the sound guide path 30, the inside of the heating chamber 3 is monitored for sparks from two places, and the accuracy of detecting the spark is improved.

(Embodiment 3)
Next, FIG. 6 is a partially cutaway configuration diagram of a microwave oven according to the third embodiment of the present invention. A printed circuit board 32 is installed on the end surface of the sound guide path 11 opposite to the heating chamber 3 by means of a mounting bracket 31, and the microphone 10 is mounted on the printed circuit board 32. With this configuration, the positional relationship between the opening of the microphone 10 and the sound guide path 11 is determined, and the sound transmitted through the sound guide path 11 can be efficiently guided to the microphone 10.

(Embodiment 4)
Next, FIG. 7 is a partially cutaway configuration diagram of a microwave oven according to the fourth embodiment of the present invention. A packing 33 made of heat-resistant rubber or the like is sandwiched between the sound guide path 11 and the punching hole 9 of the heating chamber 3, and an impact such as vibration accompanying heating of the microwave oven is transmitted to the sound guide path 11. It is preventing that. The presence of the packing 33 not only mitigates noise due to impact, but also prevents the spark sound from diffusing and can efficiently transmit the spark sound to the microphone 10 to improve the accuracy of detecting the spark sound. Can do.

(Embodiment 5)
Next, FIG. 8 is a partially cutaway configuration diagram of a microwave oven according to the fifth embodiment of the present invention. In the embodiment of the present invention, the electronic components constituting the microphone 10 and the signal processing means 13 are installed on the control board 34 of the microwave oven, and the control board 34 itself is placed in the lower part outside the heating chamber 3. It is. The sound guide path 11 is configured to lead from the punching hole 9 of the heating chamber 3 to the microphone 10. In addition, by installing the microphone 10 on the control board 34, there is no need for a routing cable, connection parts, and the like, and the distance between the microphone 10 and the signal processing means 13 is shortened, so that the noise resistance is improved. It is possible to omit the mounting bracket.

Further, since the sound guide path 11 is made of a metal pipe, the sound conduction characteristics in the high frequency range are improved by the rigidity of the material, so that the high frequency component contained in the spark sound is also conducted to the microphone 10 and the spark sound detection accuracy is improved. Can be achieved.

(Embodiment 6)
Next, FIG. 9 is an external view of the sound guide path 11 in the sixth embodiment of the present invention. By configuring the sound collection port 38 and the radiation port 39 of the sound guide path 11 in a tapered shape, the sound from the punching hole 9 is collected and the sound is radiated to the microphone 10 and the spark detection is performed with high accuracy. I can do things.

(Embodiment 7)
Next, FIG. 10 is a circuit configuration diagram of an electret condenser microphone 40 in the seventh embodiment of the present invention. The electret element 41 that stores the charge semipermanently is used as an electrode, and the change in capacitance caused by the vibration of the diaphragm 42 due to sound is impedance-converted by the field-effect transistor 43 and extracted as a change in voltage. Yes. The electret condenser microphone 40 operates with a power supply voltage of at most several volts, and the power supply input terminal and the output terminal are supplied from the power supply 45 through the resistor 46 to the same terminal 44. The output from the terminal 44 is cut in the DC component by the capacitor 12 and used for signal processing in the subsequent stage. In addition, since the electret condenser microphone 40 is small and produced in large quantities, it is possible to realize a spark detection configuration that is inexpensive in terms of cost.

  As described above, in the microwave oven according to the present embodiment, the sound information associated with the spark in the heating chamber 3 is guided to the microphone 10 installed in a place with a good temperature environment by the sound guide path 11, and the spark detection is performed. Since oscillation can be controlled, a safe and highly reliable microwave oven can be realized.

  As described above, the device for detecting sparks by sound of a microwave oven according to the present invention can be used as a safety device not only for cooking in a microwave oven but also for electrical appliances in general, and can also be used as a detection sensor for a safety device for preventing abnormal operation. it can.

The partial notch block diagram of the microwave oven in the 1st Embodiment of this invention Circuit diagram of signal processing means in the first embodiment of the present invention Frequency characteristic diagram of high-pass filter in the first embodiment of the present invention (A) Characteristic diagram showing input waveform of half-wave rectifier circuit in first embodiment of the present invention, (b) Characteristic diagram showing output waveform of same circuit Partial cutaway configuration diagram of a microwave oven in the second embodiment of the present invention Partial cutaway configuration diagram of a microwave oven according to a third embodiment of the present invention Partial cutaway configuration diagram of a microwave oven according to the fourth embodiment of the present invention Partial cutaway configuration diagram of a microwave oven in the fifth embodiment of the present invention External view of sound guide path in the sixth embodiment of the present invention The circuit block diagram of the electret condenser microphone in the 7th Embodiment of this invention Side cross-sectional view of a conventional microwave oven

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetron 3 Heating chamber 6 High voltage transformer 7 High voltage capacitor 8 High voltage diode 9, 29 Punching hole 10 Microphone 11, 30 Sound guide path 12 Capacitor 13 Signal processing means 14 Microcomputer (spark judgment means)
19, 20 High-pass filter 31 Mounting bracket 32 Printed circuit board 33 Packing 34 Control board 38 Sound collecting port
39 Radiation port 40 Electret condenser microphone

Claims (8)

A heating chamber for placing food, a magnetron for supplying microwaves for heating the food in the heating chamber, a microphone for detecting an acoustic state in the heating chamber, and a sound guide path for guiding sound from the heating chamber to the microphone And a microwave oven comprising: signal processing means for detecting spark information in the heating chamber from the output of the microphone; and spark determination means. The microwave oven according to claim 1, further comprising a plurality of sound guide paths for guiding sound from the heating chamber to the microphone. The microwave oven according to claim 1 or 2, wherein a printed circuit board is installed at the end of the sound guide path opposite to the heating chamber, and a microphone is provided on the printed circuit board. The microwave oven according to any one of claims 1 to 3, wherein the opening portion of the sound guide path on the side close to the heating chamber is disposed so as to face the opening portion of the heating chamber wall surface with a cushioning material interposed therebetween. A heating chamber for placing food; a magnetron for supplying microwaves for heating the food in the heating chamber; and a printed circuit board. The printed circuit board includes a heating control circuit, a microphone, and the heating from the output of the microphone. A microwave oven provided with a signal processing means for detecting indoor spark information and a spark determination means, and having a sound guide path for guiding sound from the heating chamber to the microphone. 6. The microwave oven according to claim 1, wherein the sound guide path is formed of a metal tube. The microwave oven according to any one of claims 1 to 6, wherein the sound guide path is tapered at both ends. The microwave oven according to any one of claims 1 to 7, wherein the microphone is an electret condenser microphone.

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