JPS6282692A - induction heating cooker - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION This invention relates to an induction heating cooker equipped with a pot overheat protection function.

Conventional technology In order to improve safety, induction heating cookers are often equipped with a function called overheat protection. This overheating protection function
This is to prevent the pot from overheating when it is placed on a baking tray and becomes dry, and it automatically stops heating if it gets overheated. This overheat protection function is achieved by providing a temperature detection element using, for example, a thermistor 2 on the back surface of the top plate 1 as shown in Fig. 3, and connecting the thermistor 2 to a temperature detection circuit 3 as shown in Fig. 6. . When the output of the temperature detection circuit 3 reaches a level preset in the heating control circuit 4, power supply to the heating coil 5 is stopped, and when the output falls to a separately set level, power supply to the heating coils is stopped. It is designed to restore the .

Generally, when the temperature of the pot 6 placed on the top plate 1 is detected by the thermistor 2 provided on the back surface of the top plate 1, there is a delay in response between the two. Therefore, the more rapid the temperature change in the pot 6, the more likely a temperature difference will occur between the pot 6 and the thermistor 2. This is clear from FIG.

In FIG. 7, A is the setting level at which the heating control circuit 4 stops supplying power to the heating coil, and B is the setting level at which the heating control circuit 4 stops supplying power to the heating coil.
is the setting level at which the power supply to the heating coil 5 is restored,
a is the temperature change of the thermistor 2 when a pot with a large heat capacity such as a thick-walled cast iron pot is boiled, b is the temperature change of the pot at that time, and C is a temperature change when a pot with a small heat capacity such as a thin-walled pot is boiled. The temperature change of the thermistor 2, d, indicates the temperature change of the pot at that time. That is, as shown in FIG. 7, the temperature of the thermistor 2 is constant at levels A and B at which the heating control circuit 4 stops and restores power supply to the heating coil 5, that is, when the overheating protection function operates. The maximum temperature f when a thin-walled pot with a small heat capacity is used for dry cooking is much higher than the maximum temperature e when a thick-walled pot with a large heat capacity is used for dry cooking.

Problems to be Solved by the Invention However, with the conventional configuration, when a thin-walled pot with a small heat capacity is used for empty cooking, the temperature of the pot becomes extremely high, which is not only dangerous, but also causes the pot to deform and become unusable. If a small amount of oil was in the pot, the oil would reach a temperature close to its autoignition temperature, posing a fire hazard.

Therefore, an object of the present invention is to provide an induction heating cooker that can prevent the temperature of the pot from reaching a high temperature even when using a thin-walled pot with a small heat capacity.

The induction heating cooker of the present invention, which solves the above-mentioned problem, includes a temperature detection element that detects the temperature of the pot, and detects the temperature and temperature change rate of this temperature detection element, and detects the temperature. The heating control means controls the power supply to the heating coil so that the power supply is within a predetermined level, and the heating control means lowers the temperature within the predetermined level range when the temperature change rate is greater than the predetermined level. The configuration is such that the power supply is controlled.

For production The effect of this technical means is as follows.

In other words, the rate of temperature rise, that is, the rate of temperature change when a pot with a small heat capacity is boiled is greater than when a pot with a large heat capacity is boiled, so this rate of temperature change is detected at the same time as the temperature, and the temperature change is detected. If the rate is higher than a predetermined level, the overheat protection function operation level is preset according to the value, that is, the predetermined level range of temperature is lowered to prevent the pot from being overheated to a high temperature.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings. In FIG. 1, a thermistor 7, which is a temperature sensing element, is provided on the back surface of the top plate. The thermistor 7 is connected to a temperature detection circuit 8 and a temperature change rate detection circuit 9 that constitute the heating control means 13, and the outputs of the temperature detection circuit 8 and temperature change rate detection circuit 9 are connected to an overheat protection temperature setting circuit. 1
o is input. If the input signal from the temperature change rate detection circuit 9 is larger than a preset level, the overheat protection temperature setting circuit 10 lowers the overheat protection temperature setting value according to the magnitude of the signal and sets the temperature. It has a function of comparing the input signal from the detection circuit 8 and comparing the input signal from the temperature detection circuit 8 with the preset overheat protection temperature set value if it is lower than a preset level. There is. The above circuit and the heating control circuit 11 constitute a heating control means 13. As a result of the comparison by the overheat protection temperature setting circuit 10, if the signal from the temperature detection circuit is larger, the output from the heating control circuit 11 to the heating coil 12 is stopped, and heating of the pot is stopped.

FIG. 2 shows how the temperatures of the thermistor 7 and the pot change at this time. In the figure, q is the temperature change of the thermistor when a pot with a large heat capacity is boiled, h is the temperature change of the pot at that time, l is the temperature change of the thermistor when a pot with a small heat capacity is boiled, i indicates the temperature change of the pot at that time. In other words, the temperature change rate of both thermistors 7, that is, the amount of change in the thermistor temperature change curves q and l at the same time t, is that e in the small heat capacity pot is larger than k in the large heat capacity pot, so the overheat protection operating temperature is corrected to a temperature lower than C in the heat capacity pot. The maximum temperature reached by the pot at this time is m for the heat capacity pot and n for the small heat capacity pot.
Therefore, both have almost the same temperature.

In this way, when a small heat capacity pot is cooked dry, the risk of the pot being heated to an extremely high temperature can be prevented, and the pot can be prevented from deforming and becoming unusable due to dry cooking. .

In the above embodiment, the thermistor was installed on the back side of the top plate 14 to detect the temperature of the pot, but as shown in FIG. The thermistor 7 is arranged within the notch 16. In this example as well, the same effects as in the previous embodiment can be obtained.

Furthermore, Fig. 5 shows a configuration in which the heat receiving part A of the thermistor is exposed to improve thermal response.
When the warp E is large, the characteristics shown in FIG. 7 will be obtained if the present invention is not used. Therefore, by using the present invention, the same effect as in the above embodiment can be obtained.

Effects of the Invention As described above, the present invention detects the temperature of the temperature sensing element and the rate of temperature change, and when the rate of temperature change is greater than a predetermined level, automatically adjusts the operating level of the overheating protection function according to the magnitude. This feature prevents pots with low heat capacity from reaching high temperatures, which tend to reach high temperatures in a short period of time when empty cooking. Therefore, there is no risk of the pot reaching extremely high temperatures due to dry cooking, which prevents the pot from deforming and becoming unusable.Also, even if the pot is heated with a small amount of oil in it, the temperature of the oil will cause it to ignite. Fires can be prevented and safety can be improved without reaching dangerous temperatures near the point.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an overheat protection circuit of an induction heating cooker according to an embodiment of the present invention, Fig. 2 is a temperature change characteristic diagram of the same, Fig. 3 is a longitudinal cross-sectional view of the induction heating cooker, Fig. 4, FIG. 6 is a sectional view of a main part showing another embodiment of the present invention, FIG. 6 is a block diagram of an overheat protection circuit of a conventional induction heating cooker, and FIG. 7 is a temperature change characteristic diagram of the same. Completed...Thermistor (temperature change element), 8...
...Temperature detection circuit, 9...Temperature change rate detection circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 2 - tS---C sword cutout Figure 5 Figure 6 Figure 7 Ginmon-

Claims (1)

[Claims] A temperature sensing element that detects the temperature of the pot, and a heating control means that detects the temperature of the temperature sensing element and the rate of temperature change, and controls the power supply to the heating coil so that the temperature is within a predetermined level, In the induction heating cooker, the heating control means lowers the temperature within a predetermined level range to control power supply to the heating coil when the rate of temperature change is greater than a predetermined level.