JP2538032B2 - High frequency heating device with pyroelectric element sensor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency heating device using a pyroelectric element sensor that generates a signal by the pyroelectric effect of hot steam or the like.

2. Description of the Related Art The mechanism of a conventional high-frequency heating device will be described with reference to the drawings.

FIG. 6 shows a conventional high-frequency heating device with a humidity sensor. When cooking is carried out, the water in the food boils and the humidity in the heating chamber suddenly changes from a decrease to an increase. Since the humidity sensor detects this point, it is possible to determine the end of cooking. That is, with the configuration shown in FIG. 6, the voltage of the reference voltage power supply 33 is detected by dividing the resistance value change of the humidity sensor 32 and the resistance 34 to control the device. (For example, Japanese Patent Laid-Open No. 53-77365) There is also a means for using a pyroelectric element sensor instead of the humidity sensor as shown in FIG. Heat is exchanged between the pyroelectric element sensor 1 and water vapor, and a thermal change causes a polarization current, and the polarization current is detected to control the device.
(For example, JP-A-62-37624) Problem to be Solved by the Invention However, when the humidity sensor is used as described above,
Since gas and oil in food adhere to the humidity sensor during cooking and the detection sensitivity decreases, it is necessary to evaporate the deposits on the humidity sensor with a heater for refresh heating processing etc. each time cooking is performed. However, there is a problem that extra power and cost are generated.

There is also a method of using a pyroelectric element sensor instead of the humidity sensor, but there is a drawback that the pyroelectric element sensor itself has temperature characteristics and the heating end time is extended as the temperature of the pyroelectric element sensor itself rises. there were.

The present invention solves the conventional problems, and an object of the present invention is to provide means for detecting the cooked state of food with a simple configuration.

Means for Solving the Problems In order to solve the above problems, a high-frequency heating device with a pyroelectric element sensor of the present invention is a heating chamber for storing an object to be cooked,
Radio wave radiating part that radiates electromagnetic waves to the cooking object to cook, cooling fan that cools the radio wave radiating part, exhaust path that discharges water vapor from the cooking object to the outside of the heating chamber, and cooked state of the cooking object. A pyroelectric element sensor for detecting and a controller for controlling various device operations are provided, and the controller controls to stop the oscillation of the radio wave radiating part for a certain period at the start of cooking.

Action With the above configuration, the present invention controls the oscillation of the radio wave radiating unit to be stopped for a certain period at the start of cooking, and thus has an action of discharging hot air and residual moisture in the heating chamber.

Practical Example FIG. 1 shows a high-frequency heating device with a pyroelectric element sensor according to an embodiment of the present invention.

The output of the pyroelectric element sensor 1 enters the controller 2, and the controller 2 controls the operations of the radio wave radiating section 3 and the cooling fan 4 according to the signal.

Food 6 is arranged in the heating chamber 5, and a part of the cooling air of the radio wave radiation unit (magnetron in this case) 3 is cooled by the cooling fan 4.
Is introduced into the heating chamber 5 via the duct 7. A solid arrow 8 shows a part of the cooling air, and a solid arrow 9 shows air containing water vapor and oil generated from the food. The air containing the steam and oil generated from the cooling air and the food passes through the exhaust unit 10 and is exhausted to the outside from the louver 12 of the body cover 11.

On the other hand, there is another suction hole 13 in the heating chamber 5, and a part of vapor 14 passes through the suction hole 13 and transfers heat to the pyroelectric element sensor 1 and is then discharged from the louver 15 of the body cover 11 to the outside. .

The cooling air 16 from the cooling fan 4 is also used for cooling the pyroelectric element sensor 1 and sucking out a part 14 of the vapor. The cooling air blows the outside air 17 into the holes 18 in the body cover 11.
It is supposed to be taken from.

Although the cooking is controlled by the above configuration, when the cooking is repeated, the exhaust passage 10, the suction hole 13, and the pyroelectric element sensor 1 in which hot air and residual moisture are swirling in the heating chamber 5 It may be wet with water droplets or the temperature may rise abnormally. If it is used as it is, a signal may be generated due to the steam generated when the water drops dry (a cause of erroneous detection), or the difference ΔT between the sensor temperature and the steam temperature may decrease due to the increase in the sensor temperature, and the output may drop. (Cause of missed detection).

In the present invention, the oscillation of the radio wave is stopped for a certain time at the start of cooking,
The above problem is solved by rotating only the cooling fan 4 to promote evaporation of water droplets and lower the sensor temperature.

FIG. 2 is a characteristic diagram showing the relationship between the peak value of the sensor output and time, where a is a state without hot air and residual moisture, b is a state with a little hot air and residual moisture, and c is hot air and residual moisture. Indicates that there is a large amount of humidity.

In the case of a, the difference between the signals before and after boiling is large, and the threshold voltage that serves as the determination criterion for detection can be easily determined. However, in the case of c, there is almost no difference between the signals before and after boiling, and it is difficult to determine where to consider detection, and the threshold voltage cannot be used for determination.

Therefore, in order to improve the reliability of detection, it is necessary to remove hot air and residual moisture and always perform cooking in the state of a.

FIG. 3 is a block diagram showing an example of the configuration of the controller 2.

The output of the pyroelectric sensor 1 passes through the low pass filter 19,
The signal is amplified by the amplifier 20, compared with the threshold voltage by the comparator 21, and if it is considered that the cooking is completed, the signal is sent from the microcomputer 22 to the radio wave radiating section 3 and the cooling fan 4 as an operation stop signal.

Further, when cooking is started by the start button 23, the microcomputer 22 operates only the cooling fan 4 for a certain period of time, the radio wave radiating section 3 is not energized, and the signal from the comparator 21 is not read.

FIG. 4 shows an external view of an example of the pyroelectric element sensor 1, and FIG. 5 shows a sectional view.

The pyroelectric element sensor 1 is mounted on a metal plate 24 such as stainless steel,
The pyroelectric electron 25 is attached with an adhesive 26 such as a silicon-based adhesive, the lead wire 29 is taken out from the two Ag electrodes 27 and 28 of the pyroelectric element 25, and connected to the controller 2 by the connector 30. In addition, the pyroelectric element 25 is covered with the coating material 31 also for fixing the lead portion 29.

In the case of actual steam detection, the steam hits the metal plate 24 and transfers heat. This heat is transmitted to the pyroelectric element 25 through the adhesive 26, a signal corresponding to the temperature change ΔT is generated by the pyroelectric effect, and is transmitted from the lead wire 29 to the controller 2.

EFFECTS OF THE INVENTION As described above, according to the high frequency heating device with a pyroelectric element sensor of the present invention, the following effects can be obtained.

(1) The oscillation of the radio wave emission part is stopped for a certain period of time at the start of cooking to remove hot air and residual moisture in the heating chamber, so even if repeated heating is performed, there is no false detection or missed detection, and a stable cooking finish. Can provide status.

(2) Compared with the absolute humidity sensor and the ultrasonic microphone, the pyroelectric element sensor has advantages that it is simple in configuration and handling and generates a signal by itself, so that a power source is unnecessary.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a high-frequency heating device with a pyroelectric element sensor showing an embodiment of the present invention, FIG. 2 is a characteristic diagram of the pyroelectric element sensor with respect to time, and FIG. 3 is a block diagram of a controller. 4 and 5 are block diagrams of a pyroelectric element sensor, FIG. 6 is a block diagram of a high frequency heating apparatus with an absolute humidity sensor, and FIG. 7 is a block diagram of a conventional high frequency heating apparatus with a pyroelectric element sensor. 1 ... Pyroelectric sensor, 2 ... Controller, 3 ... Radio wave radiating part,
4 ... Cooling fan, 5 ... Heating chamber, 10 ... Exhaust passage.

Front Page Continuation (72) Inventor Kimiaki Yamaguchi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-61-32386 (JP, A)

Claims (1)

(57) [Claims] 1. A heating chamber for storing an article to be cooked, a radio wave radiating section for radiating electromagnetic waves to the article to be cooked, a cooling fan for cooling the radio wave radiating section, and steam emitted from the article to be cooked. An exhaust path for escaping to the outside of the heating chamber, a pyroelectric element sensor for detecting the cooked state of the food to be cooked, and a controller for controlling the operation of various devices, the controller being the fixed time at the start of cooking. A high-frequency heating device with a pyroelectric element sensor configured to stop the oscillation of the radio wave emission part.