JPH01167981A - Heating condition detecting device - Google Patents

Abstract

PURPOSE:To prevent the extension of the heating finishing time by cooling an electric wave radiator and a piezo-electric element sensor simultaneously by a cooling fan to cool the electric wave radiator in the cooking. CONSTITUTION:A part of a cooling air of an electric wave radiator 7 is led in to a heating chamber 5 by a cooling fan 8 through a duct 9. The air including steam, oil, and the like, generated from the cooling air and the food is delivered from the heating chamber 5 to the outside through an exhaust 12. At the exhaust 12, a piezo-electric element sensor 1 is installed. During the cooking, the cooling fan 8 continues to rotate and cools the piezo-electric element sensor 1 to suppress its temperature rise. As a result, even though the cooking is repeated so many times, the temperature rise rate is constant, and the cooking finishing time can be made constant.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heating state detection device using a piezoelectric element sensor used in a high frequency heating device or the like.

2. Description of the Related Art The mechanism of a conventional heating state detection device such as a 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, the moisture in the food boils and the humidity rapidly changes from decreasing to increasing, so by detecting this point it is possible to determine the end of cooking. Based on this, as shown in FIG.
5 is detected by dividing the voltage of the reference voltage power supply 26 with the resistor 27 to control the equipment. (For example, Japanese Unexamined Patent Publication No. 53-77365) There is also a method of using a piezoelectric element sensor instead of the humidity sensor as shown in FIG. 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. (
(For example, Japanese Unexamined Patent Publication No. 62-37624) 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. Therefore, it is necessary to evaporate the 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 piezoelectric element sensor itself has temperature characteristics, and the heating end time becomes longer as the temperature rises.

The present invention is intended to solve such conventional problems, and aims to provide a means for detecting the heating state of food with a simple configuration.

Means for Solving the Problems In order to solve the above problems, the heating state detection device of the present invention uses a piezoelectric element sensor in place of the conventional humidity sensor. Furthermore, piezoelectric sensors have the disadvantage that the temperature rises when cooking is repeated, and the time required to finish heating is lengthened due to the temperature characteristics. The structure is such that the piezoelectric element sensor is cooled at the same time.

Effects According to the above configuration, the present invention cools the piezoelectric element sensor with the cooling fan for cooling the radio wave emitting part during cooking, and therefore has the effect of suppressing the temperature rise of the piezoelectric element sensor.

Embodiment FIG. 1 shows a high-frequency heating device using a heating state detection device with a piezoelectric element sensor, showing an embodiment of the present invention.

In FIG. 1, the output of a piezoelectric sensor 1 is a voltage amplifying amplifier 2 (hereinafter referred to as a DC blocking amplifier) configured to prevent direct current components from being applied to the sensor and to block direct current components of the sensor voltage output. ), a comparator 3 for voltage comparison, and a controller 4.

Food 6 is placed in the heating chamber 5 , and a portion of the cooling air from the radio wave emitter (magnetron in this case) 7 is guided into the heating chamber 5 by a cooling fan 8 through a duct 9 . A part of the cooling air is shown by a solid arrow line 10, and a part of the air containing water vapor, oil, etc. generated from the food is shown by a dotted arrow line 11. The cooling air and the air containing water vapor and oil generated from the food are removed from the exhaust section 1.
2 and sent out from the heating chamber 5 to the outside.

A piezoelectric element sensor 1 is attached to the exhaust section 12. In this embodiment, the core 1 of the motor that drives the cooling fan 8
3, a winding 17 is wound together with a winding 16 from a power supply glove 14 via a power switch 15, and this winding 17 is connected to a rectifying bridge 18° and a capacitor 19. Resistance 20. A constant-voltage power supply section consisting of a constant-voltage diode 21 is configured, eliminating the need for a transformer for the control circuit. Further, the buzzer 22 is configured to operate according to a signal from the controller 4 when the amplified signal voltage becomes larger than a set threshold voltage ΔVt.

At the same time, the power supply voltage of the radio wave emitting unit 7 is opened in response to a signal from the controller 4, and the cooling fan 8 continues to rotate during cooking to cool the piezoelectric element sensor 1 along the path indicated by the arrow 23, thereby suppressing the temperature rise.

FIG. 2 shows an example of data regarding the signal and noise of the piezoelectric sensor. (a) shows an example of a signal waveform when the water in the refrigerator 5 boils. (b) shows an example of the results of spectrum analysis of this waveform.

It can be seen that when the ultrasonic microphone for 40 kHz is exposed to wind containing warm water vapor, a large signal is output in the 0-50H1 band. The difference between A and A is about 30 dB, and the signal level is several mV. If the water in the refrigerator boils,
1 is before boiling, and 3 is when the high-frequency heating device is not energized.

Figures 3 and 4 show a circuit example of the amplifier 2 having bandpass filter characteristics, which is a combination of a low-pass filter and a bypass filter, and the amplifier output voltage when this circuit is used to heat 400cc of water. An example waveform is shown.

As can be understood from the above results, by comparing the threshold voltage △vt and the signal voltage in the comparator 3 of FIG. In this way, it is possible to know when the food to be cooked has reached the boiling point, and at the same time, by turning off the power supply voltage to the radio wave emitting section 7, heating can be stopped.

FIG. 5 shows the difference between the case where the piezoelectric element sensor is not cooled and the case where it is cooled in terms of the relationship between the cooking completion time and the degree of temperature rise. The piezoelectric element sensor generates polarized current in response to thermal changes, so when cooking is repeated without cooling as in the conventional method, the temperature of the piezoelectric element sensor and its atmosphere rises each time, so the temperature of the piezoelectric element sensor and its atmosphere rises each time. Even if the same amount of warm water vapor collides and exchanges heat, the temperature change will gradually become smaller. Therefore, as shown in FIG. 5(a), each time the cooking is repeated, the temperature rise degree ΔT becomes smaller and the cooking end time t becomes longer.

On the other hand, when cooling the piezoelectric element sensor during cooking, the fifth
As shown in Figure (b), since the temperature rise of the piezoelectric element sensor is suppressed, the degree of temperature rise Δt is constant no matter how many times the cooking is repeated, and the cooking end time t is also the same.

Effects of the Invention As described above, the heating state detection device of the present invention provides the following effects.

(1) During cooking, the piezoelectric element sensor is cooled by a cooling fan for cooling the radio wave emitting part, so even when repeatedly heated, the temperature rise of the piezoelectric element sensor is suppressed, extending the life of the sensor. Since there is no change in the composition of the adhesive between the piezoelectric element and the electrode, stable output can be obtained.

(2) The cooking end time does not vary due to the temperature characteristics of the piezoelectric sensor.

(3) Humidity sensors and gas sensors essentially utilize the grain boundary phenomenon of the sensing element, so in order to prevent clogging of the grain boundaries, the heater is kept warm and the heater is periodically turned on. In terms of maintenance, there are a lot of complicated things to do, such as burning off dirt with a piezoelectric sensor, but piezoelectric sensors do not require such things.

Therefore, there is no need for electricity for heat retention or grilling, making it a power-saving type.

(4) For the same reason as (2), the heating state detection device of the present invention does not require any control parts or special transformer for the heater power to maintain the accuracy of the heat retention heater power, and is inexpensive. . When the heating state detection device of the present invention is used in a high frequency heating device or the like, the cost can be significantly reduced.

(5) As is clear from FIG. 2(b), stable control is possible because the signal is large compared to the noise level caused by electromagnetic noise within the high-frequency heating device and wind noise from the cooling fan.

(6) Furthermore, since a DC blocking amplifier is used, no DC voltage is applied to the piezoelectric element sensor, and changes in element characteristics due to ion conduction or the like can be prevented.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a block diagram of a state in which a heating state detection device according to an embodiment of the present invention is used in a high-frequency heating device, Fig. 2 a,
b is a characteristic diagram of the signal and noise on the piezoelectric element, Fig. 3 is a circuit diagram of an amplifier with band-pass filter characteristics, and Fig. 4 is an amplifier when 400 oa of water is heated using the circuit in Fig. 3. Output voltage waveform diagrams, Figures 5a and b are characteristic diagrams showing the difference in temperature rise and cooking completion time when the piezoelectric element sensor is not cooled and when it is cooled, and Figure 6 is a characteristic diagram showing the difference in cooking completion time when a conventional humidity sensor is used. Block Diagram FIG. 7 is a block diagram using a conventional piezoelectric element sensor. 1...Piezoelectric element sensor, 5...Heating chamber, 7...Radio wave emitting section, 8...Cooling fan, 12...Exhaust Department. Name of agent: Patent attorney Toshio Nakao, 1 person/-
- 1 piezoelectric element °C Sensor 5 - Heating chamber + 2 - 14 m Air 3 houses Fig. 1 Fig. 2 + (7) (b) Fig. 3 v K4 Fig. Rumor - 1 hour Fig. 5 (aλ Time (seconds) (b ) Time (seconds) Figure 6 Figure 7 vT

Claims (1)

[Claims] a heating chamber in which a food to be cooked is housed for cooking; a radio wave emitting section that radiates electromagnetic waves to the food to cook the food; a cooling fan that cools the radio wave emitting section; It is equipped with an exhaust part that releases water vapor to the outside of the heating chamber, and a piezoelectric element sensor that detects the moisture content of the food to be cooked, and is provided with a cooling part for cooling the radio wave emitting part during cooking in order to prevent the influence of the temperature characteristics of the piezoelectric element sensor. A heating state detection device that simultaneously cools the radio wave emitting section and the piezoelectric sensor using a fan.