JPH0614477B2 - Heating device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a composite heating device including a heater and a microwave heating means, when an object to be heated causes ignition and combustion,
The present invention relates to a safety control system that detects this and stops the operation of the heating device.

2. Description of the Related Art The high-frequency heating device described in Japanese Utility Model Publication No. Sho 49-1885 is provided with a temperature switch at the exhaust port of the air forcibly passing through the heating chamber, and using this temperature switch to detect an abnormal temperature rise in the heating chamber, Even if food ignites and burns in the heating chamber,
A safety device for quickly stopping high frequency oscillation is disclosed.

According to this, even if the temperature of the food in the heating chamber rises abnormally due to a timer failure or a setting error, and the ignition and combustion are reached,
The temperature switch provided at the exhaust port promptly detects this and stops the operation of the blower and the magnetron, so that it is possible to prevent flame from blowing out from the exhaust port and burning the curtain or wall material near the exhaust port.

Safety devices similar to this are widely used in household high-frequency heating devices such as microwave ovens.

Problems to be Solved by the Invention However, in recent years, with the advent of hybrid heating devices such as oven microwave ovens in which electric heaters and gas burners are incorporated in microwave ovens, the above safety devices must be reexamined. I can not get it.

That is, in such a composite heating device, the temperature inside the heating chamber reaches a maximum of 250 to 300 ° C. even in normal use, and the conventional temperature switch is naturally exposed to a high temperature of around 200 ° C. And since this is normal oven operation, the temperature switch must not operate to stop the power supply to the heating device. Therefore, the operating temperature of the temperature switch will be the maximum temperature in this oven operation with a margin added, and when food inevitably ignites and burns, this cannot be detected quickly, and it takes a considerable time after ignition. Finally, the temperature switch worked and could not fully function as a safety device.

As an example, the operating temperature of the combustion detecting temperature switch in the conventional microwave oven is about 120 ° C., and it operated within 1 to 2 minutes after ignition. However, in the oven microwave oven, the operating temperature of this temperature switch was about 230 ° C., and it finally operated 10 to 15 minutes after ignition. At this time, the cloth such as a cloth covered with the exhaust port was ignited and ignited.

The present invention solves such a conventional problem, and realizes a safety control system that quickly detects the ignition and combustion of food in the heating chamber and stops the operation of the heating device even in the combined heating device. It is a thing.

Means for Solving Problems The heating device of the present invention includes a temperature sensor for detecting the temperature in the heating chamber, the control unit has a counter unit and a storage unit, and the control unit has a heater and microwave heating. Control the power supply to the means.

Operation The control unit according to the heating device of the present invention counts a certain period of time after the heating is started by the counter unit, and interrupts the determination / processing of the ignition and combustion detection by the temperature sensor until this time elapses. After that, the combustion detection temperature stored in the storage means is compared with the temperature in the heating chamber detected by the temperature sensor, and when the detection value of the temperature sensor reaches or exceeds the combustion detection temperature, the heating means is sent to the heating means. To stop the power supply.

Example A heating apparatus according to an example of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram showing the configuration of a heating device as an embodiment of the present invention.

Now, the outer shell 1 has a built-in heating chamber and the like, and the door body 2 closes the opening of the heating chamber so as to be openable and closable. Various commands are input by the operator from the keyboard 3, and the input commands are decoded by the control unit 4. Then, the control unit 4 displays the input heating data and the like on the display unit 5 and starts heating the object to be heated 7 placed in the heating chamber 6. The heating is performed by energizing the heating means 9, 9'through the drivers 8, 8 '. In this embodiment, a magnetron is provided as the second heating means 9'for supplying microwaves to the heating chamber, and an electric heater is provided as the first heating means 9 for increasing the ambient temperature in the heating chamber. Microwaves are radiated from a power supply opening on one wall surface, and electric heaters are arranged on the upper and lower surfaces of the heating chamber 6 to raise the temperature in the heating chamber 6 and enable oven cooking by radiation and convection.

A thermistor or the like is used as the temperature sensor 10, and detects the temperature in the heating chamber 6 as a change in an electric signal such as electric resistance or voltage. The detection circuit 11 is an interface that connects the temperature sensor 10 and the control unit 4. For example, if a thermistor is used as the temperature sensor 10, this and a known precision resistor are connected in series, and a reference voltage is applied to both ends. For example, the resistance value change of the thermistor can be read as a voltage change, and this can be input to the A / D converter of the control unit 4.

The temperature sensor 10 is provided in the exhaust guide 12 and monitors ventilation air in the heating chamber 6 forcibly ventilated by the fan 13.

The loading tray 14 is rotationally driven by the motor 15 to improve the heating unevenness of the object 7 to be heated.

Now, FIG. 1 is a time chart showing the control sequence of the present invention. The figure (a) shows the normal operation by microwave heating, and the figure (b) shows the case where microwave heating is performed immediately after operating the oven, respectively. The heating chamber temperature refers to data detected by the control unit using a temperature sensor.

Here, there are two main points of the present invention. First, the combustion detection is performed only during microwave heating, and second, the combustion detection is interrupted for a certain mask time T _M after the start of heating.

First of all, I explained experimentally that foods in the heating chamber are ignited and burned only by microwave heating due to timer failure or setting error. Combustion tests of various foods were tried, but, for example, in the case of microwave heating, a product having a high-frequency output of 600 watts steadily ignited and combusted in about 20 minutes with one piece of garlic and potato. However, when heated in an oven, it did not ignite even when operated at 250 ° C. for 2 hours. Of course, the charcoal fired
Even if it ignited in a match, it was almost ready to burn, but the point is that the ignition temperature does not seem to reach 250 ° C. In the case of microwave heating, as carbonization progressed, microwave sparks started inside the food and eventually ignited reliably, leading to combustion. From the above process, it can be determined that combustion detection is only required for microwave heating.

Next, the latter (mask time) will be described. In the combined heating device, microwave heating may occur while the heating chamber is still hot after the oven is operated. At this time, if combustion is erroneously detected and heating cannot be started or interrupted, it is a problem. However, if the combustion detection temperature θ _F is increased, the safety performance is lowered as described in “Problems to be solved by the invention”. Therefore, in the present invention, the combustion detection temperature θ _F is 100 to 100, which is the same as the conventional one.
By setting the temperature to about 120 ° C. and providing a masking time T _M instead of it, preparation for high temperature operation after using the oven was performed. That is, even if the temperature of the heating chamber exceeds the combustion detection temperature θ _F until the mask time T _M elapses after the start of heating,
Ignoring this, the combustion detection operation is executed after the lapse of T _M. By this sequence, as shown in Fig. (B), even if the temperature immediately after the start of heating exceeds θ _F , T _M
In the meantime, it surely drops below θ _F and does not hinder microwave heating.

As an example, when the combustion detection temperature θ _F = 120 ° C., the mask time T _M is preferably about 4 minutes. With this setting, even in the microwave heating immediately after the oven at 250 ° C., the temperature in the heating chamber dropped to 95 ° C. when T _M = 4 minutes had elapsed. Especially because it is forcedly ventilated by the fan, 110
It quickly dropped to about ℃ and did not interfere with normal operation.

Of course, in the normal operation (cool operation) in (a), θ _F
= 120 ° C, the combustion can be detected in the same way as the conventional microwave oven alone.
The heating could be stopped in about 2 minutes.

Next, a flow chart which is an example of a control program when this control unit is configured by a microcomputer will be described with reference to FIG.

First, the initialization program RUNs, and the RAM is cleared and the output port is reset (A). Next, the clock is counted and basic data of various counters is created (B). This is the one with the built-in counter,
It will be executed hard. Subsequently, the display data is output to perform a predetermined display on the display unit (C). Since dynamic lighting is generally used, display data is created for this purpose. Then, it is checked whether or not the heating device is in operation (D), and when it is not in operation, the key input is taken in and decoded (E). The operations of the cooking key and the start key are decoded and processed here.

If it is confirmed during operation during the operation check (D), it is first determined whether or not microwave heating is being performed.
(F). Then, in the case of microwave heating, first, the mask time T _M is counted by the T _M counter (G). Next, it is judged whether or not a predetermined mask time T _M has elapsed (H), and after the elapse of T _M , the heating chamber temperature θ becomes the combustion detection temperature θ.
_It is checked whether _F has been reached (I). Therefore, the combustion detection temperature θ _F is stored in the ROM of the microcomputer which is the storage means. Before the lapse of T _M , the combustion detection process is interrupted and the timer counts down (I). Also, when the combustion is not detected in the item I, the timer counts down (J), and when the timer ends (K), the heating is stopped (L).

When combustion is detected in the item I (when θθ _F is reached), heating is stopped (L). By the above processing, if the food is ignited and burned in the heating chamber, this is promptly detected, and the heating device can be safely stopped without the flame blowing out of the body. Further, by setting the mask time, even if microwave heating is performed in a hot heating chamber after using the oven, θ <θ _F can be satisfied before the mask time T _M elapses. Avoids stopping.

Next, the sequence during the oven operation will be described. If it is determined in the F term that the microwave heating is not performed, that is, the oven heating is performed, the temperature of the oven is first adjusted. In the present embodiment, the same temperature sensor as that used for combustion detection is also used for adjusting the temperature of the oven. Then, it is checked whether or not the heating chamber temperature θ has reached the set temperature θ _S (M). If the heating chamber temperature θ has reached the set temperature θ _S , the heater is turned off (N), and if θ _S or less, the heater is turned on. (P).
After the temperature adjustment process, the process proceeds to the timer process.

The above is one example of the control program when the control unit is configured by a microcomputer.

Next, another embodiment relating to the mounting position of the temperature sensor of the present invention will be described.

In FIG. 4A, the temperature sensor is provided not in the exhaust guide 12 but in a part of the side wall of the heating chamber 6. According to this, since the temperature sensor is close to the center of the heating chamber 6, the oven temperature can be adjusted well.

In FIG. 4 (b), the temperature sensor is attached in contact with the upper wall of the heating chamber. According to this, since the temperature sensor is not exposed to the exhaust gas, it is possible to prevent the electric resistance between the terminals from lowering due to dew condensation due to steam or the like generated from food.

Of course, the combustion detecting temperature sensor and the oven temperature adjusting temperature sensor can be separately configured.

EFFECTS OF THE INVENTION As described above, the heating device of the present invention is provided with the temperature sensor for detecting the temperature in the heating chamber, the elapsed time of the mask time T _M is counted by the counter means, and after the elapsed time, it is stored in the storage means. The combustion detection temperature is compared with the temperature of the heating chamber detected by the temperature sensor. When the combustion detection temperature is reached, the power supply to the heating means is stopped, and the following effects can be obtained.

(1) The combustion detection temperature can be set to a low value without considering the oven operating temperature, and even if food is ignited and burned in the heating chamber during microwave heating, this is quickly detected and the heating operation is stopped. Therefore, fire can be prevented.

(2) The temperature sensor for combustion detection can also be used for oven temperature control, which simplifies the system and saves resources.

(3) Even if the temperature sensor is broken, microwave heating can be done only for Max time. Usually microwave heating is 1
Most of them take about 2 minutes, and the mask time is 4
Even if the temperature sensor is broken, microwave heating, which is much more frequently used than the oven, can be performed without any problem even if the temperature sensor is broken. If the sensor is also used as the temperature control sensor as in the item (2), the user notices the failure during the operation of the oven and makes a service call, so that it is possible to avoid using the sensor for a long period of time with the combustion detection function impaired.

[Brief description of drawings]

FIG. 1 is a waveform diagram showing a combustion detection method of a heating device in one embodiment of the present invention, FIG. 2 is a block diagram showing the same configuration, FIG. 3 is a control flowchart of a microcomputer which is the same control unit, and FIG. It is sectional drawing which shows another Example which shows the attachment position of the same temperature sensor. 4 ... control unit, 6 ... heating chamber, 7 ... object to be heated, 9,
9 '... heating means, 10 ... temperature sensor, G ... counter means.

Claims (2)

[Claims] 1. A heating chamber in which an object to be heated is placed, a first heating unit coupled to the heating chamber for raising an ambient temperature in the heating chamber, and a second heating unit for supplying a high frequency wave into the heating chamber. And a temperature sensor for detecting the temperature of the heating chamber, and a control unit for controlling power supply to the first and second heating means. The control unit has counter means, and a predetermined period from the start of heating. The time is counted by the counter means, the detection of the abnormal temperature rise in the heating chamber by the temperature sensor is interrupted until the time elapses, and after the time elapses, the abnormal temperature is stored by the storage means provided in the control unit. If the detected temperature of the temperature rise is read and the detected value of the temperature sensor reaches or exceeds this stored temperature based on the read temperature, the controller is configured to stop the power supply to at least the second heating means. . 2. The heating device according to claim 1, wherein the abnormal temperature rise is detected by the temperature sensor while the second heating means is being powered.