JPH0210029A - Microwave oven with piezoelectric element sensor - Google Patents

Abstract

PURPOSE:To detect the heated condition of foodstuffs by the simple constitution of a heating device, without being affected by condensed dew droplets and stain whatsoever, by a method wherein a piezoelectric element sensor which detects the boiled condition of a material to be cooked and produces an output signal is made to closely adhere to the wall surface of a heating chamber. CONSTITUTION:A piezoelectric element sensor 1 is mounted on top of the ceiling plate of a heating chamber 2, and output from the piezoelectric element sensor 1 is sent into a controller 3. An electric power source for an electric wave radiating part 4 and a cooling fan 5 is turned on/off by a signal released out of the controller 3. The piezoelectric element sensor 1 is secured on top of the ceiling plate 11 of the heating chamber 2 in a closely adhering state. Boiled vapor 10 impinges against the ceiling plate 11 of the heating chamber 2 and gives it heat. The heat is conducted within the ceiling plate and transmitted to the piezoelectric element sensor 1 to produce a signal. Since the piezoelectric element sensor 1 is not exposed directly to steam, gas, oil and the like, it can be prevented from being affected by condensed dew droplets and stain.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high-frequency heating device with a piezoelectric element sensor that detects and controls the state of gas generated in response to heating of an object to be cooked.

2. Description of the Related Art A detection method in a conventional high-frequency heating device will be explained with reference to the drawings.

FIG. 6 shows a conventionally used high frequency heating device with a humidity sensor. In the case of a humidity sensor, since the moisture in the food 21\-7 boils and the humidity changes rapidly from decreasing to increasing, it is possible to determine the end of cooking by detecting this point. Based on this, as shown in FIG. 6, changes in the resistance value of the humidity sensor 24 are detected by dividing the voltage of the reference voltage power source 25 with a resistor 26 to control the equipment. (For example, Japanese Unexamined Patent Publication No. 53-77365) Furthermore, as shown in FIG. 7, there is a means of using a piezoelectric element sensor instead of the humidity sensor. Heat is exchanged between the piezoelectric element sensor 1 and water vapor, and the thermal change generates a polarization current, which is detected to control the device. (
Problems to be Solved by the Invention However, when a humidity sensor is used as described above, gas or oil in the food adheres to the humidity sensor during cooking, reducing detection sensitivity. It is necessary to evaporate deposits on the humidity sensor using a heater for refresh heat treatment every time cooking is performed, resulting in the problem of extra power and cost.

There is also a method of using a piezoelectric element sensor instead of a humidity sensor, but the conventional configuration was to attach the piezoelectric element sensor to the exhaust part or steam hole, which has the disadvantage that it receives water vapor directly and condenses, causing the output to fluctuate. was there. moreover,
Humidity sensors are no exception, but the influence of gas, oil, and other contaminants in food cannot be ignored, and the problem remains that the characteristics change.

The present invention solves such conventional problems, and aims to detect the heating state of food with a simple configuration and provide a constant cooking finish state without being affected by condensation or dirt. .

Means for Solving the Problems In order to solve the above problems, the high-frequency heating device with a piezoelectric element sensor of the present invention includes a heating chamber in which a food to be cooked is housed for cooking, and a heating chamber for transmitting electromagnetic waves to the food to be cooked. It is equipped with a radio wave radiating section that radiates and cooks, and a piezoelectric element sensor that detects the S++ rising state of the object to be cooked and gives an output signal, and the piezoelectric element sensor is configured to be in close contact with the wall surface of the heating chamber.

Function: As described above, the present invention has a structure in which the piezoelectric element sensor is brought into close contact with the wall surface of the heating chamber, so that the function of detecting the boiling state of the food to be cooked based on the temperature of the wall surface is achieved with a simple structure.

Example Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a high-frequency heating device with a piezoelectric element sensor showing one embodiment of the present invention. The piezoelectric element sensor 1 is located in a heating chamber 2
The output of the piezoelectric sensor 1 is mounted on the top plate of the controller 3.
The radio wave emitter 4 and the cooling fan 5 are activated by the signal from the controller 3.
The power supply is turned 0N10FF.

A food to be cooked 6 is placed in the heating chamber 2, and the cooling air 7 from the radio wave emitting section 4 is guided into the heating chamber 2 by a cooling fan 5.

Cooling air 7 and air 8 containing water vapor, oil, etc. generated from the food to be cooked are sent out from heating chamber 2 through exhaust port 9. Some of the dl)5 ・\-7 The rising steam 10 hits the heating chamber top plate 11, imparts heat, and conducts heat to the piezoelectric element sensor 1, causing a temperature change.

FIG. 2 shows an example of a detailed mounting configuration of the piezoelectric element sensor. The piezoelectric sensor 1 is mounted on the top plate 11 of the heating chamber in close contact with the top plate 11 of the heating chamber. The boiling steam 10 hits the heating chamber top plate 11 and provides heat. The mechanism is such that heat is conducted inside the top plate and is transmitted to the piezoelectric element sensor 1, which generates a signal.

Since the piezoelectric element sensor 1 is not directly exposed to water vapor, gas, oil, etc., it will not be subject to dew condensation or dirt. Further, the lead wire 12 is for transmitting the generated output.

FIG. 3 shows an example of the configuration of the piezoelectric sensor 1. As shown in FIG. A pair of vapor-deposited electrodes 14 are applied to a lead titanate-based piezoelectric element 13, and one end of the electrodes 14 is electrically contacted and bonded onto a metal plate 16 with an adhesive 15.

An output node 17 is led out from the other end of the electrode 14,
From the metal plate 16 is a glue 18 for connection to ground.
has also been derived. Note that the various types of wires are electrically insulated. The resin 19 integrally seals the piezoelectric element 13, the metal plate 16, and the lead-out portions of the various lead wires 17 and 18 with a non-moisture permeable molding material. These constitute the piezoelectric element sensor 1.

FIG. 4 is a frequency characteristic diagram of the piezoelectric element sensor output.

In contrast to the output A before boiling, the output after boiling is obtained, and boiling can be detected based on the difference between A and B. However, if condensation occurs on the surface of the piezoelectric sensor due to repeated cooking with the conventional mounting configuration, the same amount of boiling steam will only produce a signal about the output shown in FIG. 4. In other words, the output is attenuated from A to A. For this reason, with the conventional mounting configuration, there are problems such as a delay in detection time or no detection at all even if the food to be cooked is already boiling. On the other hand, with the configuration of the present invention, no condensation occurs on the surface of the piezoelectric sensor even if cooking is repeated, and if the food is of the same quantity and quality, the fourth
The output shown in the figure can be obtained, the detection time is constant, and a stable cooking finish can be provided.

7 \-2 FIG. 5 is a block diagram depicting the control portion of FIG. 1 in detail. The output of the piezoelectric element sensor 1 is input to a controller 3, which controls the operation of various devices such as a radio wave emitting section 4 and a cooling fan 5. In the controller 3, a filter 20 selects a pass frequency band, an amplifier 21 amplifies the output to a level that is easy to control, a comparator 22 compares it with a set value, and a microcomputer 23 generates a control signal. For example, before boiling, the output to the microcomputer 23 is lower than the set value of the comparator 22, so the input to the microcomputer 23 remains unchanged, and each device continues to operate.After boiling, the output jumps, which is higher than the set value of the comparator 22, and the input to the microcomputer 23 is reversed. Then, a control signal is issued to stop the operation of each device.

With the configuration described above, there is no condensation on the surface of the piezoelectric element sensor, a stable output is always provided, and a constant cooking finish state can be obtained.

Effects of the Invention As described above, according to the high frequency heating device with a piezoelectric element sensor of the present invention, the following effects can be obtained.

(1) Since the piezoelectric element sensor is configured to be in close contact with the heating chamber wall surface, stable boiling detection can be achieved without condensation or dirt from cooking on the surface of the piezoelectric element sensor, providing a constant state of cooking completion. be able to.

(2) Since there is no output fluctuation due to dew condensation, the design of the circuit and installation is easy, and heaters and various correction elements are not required, resulting in a significant cost reduction.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a high-frequency heating device with a piezoelectric element sensor according to an embodiment of the present invention, and FIG. (b) is a plan view and a sectional view showing how to install the same piezoelectric element sensor, Fig. 3 is a configuration diagram showing an example of the same piezoelectric element sensor, Fig. 4 is a frequency characteristic diagram of the same piezoelectric element sensor output,
FIG. 5 is a block diagram showing the same control method, FIG. 6 is a block diagram of a conventional high-frequency heating device with a humidity sensor, and FIG. 7 is a block diagram of a conventional high-frequency heating device with a piezoelectric element sensor. 1...Piezoelectric element sensor, 2...Heating chamber, 3...Controller, 4...Radio wave/radiation section,
5... Cooling fan.

Claims (1)

[Claims] a heating chamber in which a food to be cooked is stored for cooking; a radio wave emitting section that radiates electromagnetic waves to the food to cook the food;
A high-frequency heating device with a piezoelectric sensor, comprising: a piezoelectric sensor that detects a boiling state of the object to be cooked and provides an output signal, the piezoelectric sensor being in close contact with a wall surface of the heating chamber.