JPH0570276B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an induction heating cooker equipped with a temperature control function.

[Technical background of the invention and its problems]

In general, an induction heating cooker generates a high-frequency magnetic field from a heating coil and applies it to the pot on the top plate to generate an eddy current in the pot, and heats the pot by self-heating due to eddy current loss. I have to. Some such induction heating cookers have a temperature control function, an example of which is shown in FIG.

In FIG. 6, a top plate 2 is provided on the upper surface of the cooking device main body 1.
A pot 3 is placed on top. A temperature sensor 4 is attached approximately to the center of the back surface of the top plate 2. Further, a temperature setting knob 5 is provided on the side of the main body 1, and this temperature setting knob 5 is connected to a temperature setting device 6 inside the main body 1. Furthermore, in the main body 1, the temperature setting knob 5
Nearby there is a temperature display section 7 which is a notification means.
is provided. This suitable temperature display section 7 is connected to the main body 1
It has a light emitting diode 8 inside, and by transmitting the light emitted from the light emitting diode 8 to the outside, it notifies the user that the food in the pot 3 is at an appropriate temperature. A heating coil 9 is provided within the main body 1 at a position facing away from the back surface of the top plate 2. Further, provided within the main body 1 are an inverter circuit 10 that supplies a high frequency current to the heating coil 9, a power transformer 11, a control circuit board 12, a cooling fan 13, and the like.

That is, as shown in FIG. 7, during cooking, the detected temperature Tth of the temperature sensor 4 is taken in, and the temperature
and a set temperature preset by the temperature setting device 6, and the heating output is controlled to be turned on or off depending on the comparison result. And the detected temperature
When Tth reaches the appropriate temperature, the light emitting diode 8 is activated to emit light, thereby informing that the food in the pot 3, such as oil for tempura, is at the appropriate temperature.

However, in such an induction heating cooker, since the top plate 2 exists between the pot 3 and the temperature sensor 4, there is a difference between the detected temperature Tth and the actual temperature of the pot 3, as shown by the broken line in FIG. An error will occur between the temperature and the temperature Ta. In particular, this error is noticeable when the temperature rises at the start of cooking, and even if the detected temperature Tth reaches the appropriate temperature and the appropriate temperature is displayed, the temperature ta of the pot 3 remains lower than that, which adversely affects the quality of the cooking. There are problems such as giving users a sense of distrust.

Therefore, as shown in Fig. 8, some devices display the appropriate temperature after a certain period of time t after the detected temperature Tth reaches the set temperature _T1 , but since the certain period of time t is fixed, it is possible to Display is not possible. Furthermore, Fig. 8 shows the temperature change when the pot 3 is large, and when the pot 3 is small, the temperature Ta of the pot 3 is higher than the set temperature _T1 as shown in Fig. 9. The appropriate temperature is displayed. In order to eliminate such problems, the above-mentioned fixed time t
It is conceivable to set it for a long time. In this case, even if the pot 3 is large, if the above-mentioned fixed time is short, the temperature of the pot 3 will be lower than the set temperature and it will not necessarily be possible to accurately display the appropriate temperature. It is necessary to lengthen the fixed time t. In this case, considering not only the size of the pot but also the amount and type of food in the pot, it is necessary to set the predetermined time t longer with a sufficient margin. If you do this, the temperature of the pot 3 will eventually converge to the set temperature, so you can get a good appropriate temperature indication, but if the temperature of the pot reaches the appropriate temperature early, it will be wasted until the subsequent appropriate temperature indication. This consumes time and there is a delay in displaying the appropriate temperature, and as a result, there is a risk that the oil in the pot 3 will be left in a high temperature state before cooking has started.
It wastes power.

[Purpose of the invention]

This invention was made in view of the above circumstances, and its purpose is to be able to accurately and quickly notify the appropriate temperature state, and to prevent food in a pot from being left in a high temperature state for a long time. To provide an induction heating cooker that can be used without unnecessary power consumption and that does not consume power unnecessarily.

[Summary of the invention]

This invention provides a comparison means for comparing the temperature detected by a temperature sensor and a set temperature, a control means for controlling heating output on and off according to the comparison result of the comparison means, and a number of times the temperature detected by the temperature sensor reaches the set temperature. This device is provided with a counting means for counting, and a notifying means for notifying that the pot is at a proper temperature when the count value of the counting means reaches a set value.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

First, the overall configuration is the same as that shown in FIG.

As shown in FIG. 2, a DC voltage Vcc is applied to a series circuit between a resistor 21 and a temperature sensor (negative characteristic thermistor) 4, and a series circuit between a resistor 22 and a temperature setter (variable resistor) 6. . The voltage generated at the temperature sensor 4 (corresponding to the detected temperature Tth) and the voltage generated at the temperature setter 6 (corresponding to the set temperature) are supplied to the comparator 24. This comparator 24 has a feedback resistor 25 for providing hysteresis in the output. Thus, the output of the comparator 24 is supplied as a heating output control signal S to a heating operation section (not shown), and is also supplied to an input terminal of a counter circuit 26. Further, the voltage generated at the temperature sensor 4 and the voltage generated at the interconnection point of the resistors 28 and 29 are supplied to a comparator 27.
The output of the counter circuit 26 is supplied to the reset input terminal R of the counter circuit 26. A light emitting diode 8 is connected to the output end of the counter circuit 26 via a resistor 30. Here, when the logic "0" signal is supplied to the reset input terminal R, the counter circuit 26 counts the pulse signal supplied to the input terminal, and the count value Nc is set to a set value n (for example, "5"). When this is reached, a logic "1" signal is output from the output terminal.

Next, the operation of the above configuration will be explained with reference to FIG.

While placing the pot 3 on the top plate 2,
The set temperature is adjusted using the temperature setting knob 5, and the cooking start operation is performed. Then, the inverter circuit 10 operates, a high frequency current flows through the heating coil 9, and a high frequency magnetic field is emitted from the heating coil 9. This high frequency magnetic field is applied to the pot 3 through the top plate 2, thereby causing the pot 3 to self-heat.

As the temperature of the pot 3 increases, it is detected by the temperature sensor 4. Detected temperature Tth of temperature sensor 4
reaches T ₃ , the output of comparator 27 becomes logic “0”
As a result, the counter circuit 26 becomes operable. Then, when the detected temperature Tth further increases and reaches the set temperature _T1 , the output of the comparator 24 becomes logic "1", the operation of the inverter circuit 10 is stopped, and the oscillation output is turned off. When the detected temperature Tth falls to _T2 , which is slightly lower than the set temperature _T1 , due to this turning off, the output of the comparator 24 becomes logic "0", and the inverter circuit 10 operates again, turning on the oscillation output. . In this way, the heating output is turned on and off repeatedly, and the detected temperature Tth becomes the set temperature.
Each time T ₁ is reached and the output of the comparator 24 becomes logic "1", it is counted by the counter circuit 26. Then, the count value Nc of the counter circuit 26
When becomes the set value n, the output of the counter circuit 26 becomes logic "1" and the light emitting diode 8 emits light. At this time, the actual temperature Ta of pot 3 is the set temperature
T ₁ has been reached, and an accurate appropriate temperature display will be performed. Thereafter, when the detected temperature Tth drops to _T3 due to the addition of food to the pot 3, the output of the comparator 27 becomes logic "1" and the counter circuit 26 is reset. When the counter circuit 26 is reset, its output becomes logic "0" and the light emitting diode 8 is turned off.

FIG. 3 shows the temperature change when the pot 3 is small. In this case as well, when the count value Nc of the counter circuit 26 reaches the set value n, the appropriate temperature is displayed, and at this time the actual temperature Ta of the pot 3 is displayed. is the set temperature T ₁
matches.

In this way, the number of times the detected temperature Tth of the temperature sensor 4 reaches the set temperature _T1 is counted, and when the count value reaches the set value, the appropriate temperature is displayed. Even if the optimum temperature period differs due to differences in the amount and type of food, this can be accurately and quickly detected and displayed immediately.

Therefore, unlike the case where the appropriate temperature is displayed after a sufficiently long period of time has elapsed from the detection of the set temperature, as was previously thought, there is no delay in displaying the appropriate temperature, and therefore, there is no delay in displaying the appropriate temperature. It is possible to eliminate the risk of food (oil) being left in a high temperature state for a long time, and it is highly suitable for frying food using oil, and it also prevents wasted power consumption.

In the above embodiment, the comparators 24, 27, the counter 26, etc. were used to control the appropriate temperature display, but as shown in FIG. 4, the appropriate temperature display control was performed using a microcomputer. Good too. That is, as shown in Figure 4,
A DC voltage Vcc is applied to the temperature sensor 4 via a resistor 41, and the voltage generated at the temperature sensor 4 is supplied to the microcomputer 40 via an A/D (analog/digital) converter 42.
The microcomputer 40 outputs a heating output control signal S and also supplies a driving voltage to the light emitting diode 8 via a resistor 43. FIG. 5 shows the control of the microcomputer 40.

Furthermore, in the above embodiment, the set value n for the count value Nc of the counter circuit 26 was set to "5";
The numerical value is not limited and may be determined as appropriate depending on the situation. Furthermore, although the appropriate temperature display section 7 having the light emitting diode 8 is used as a notification means, the present invention is not limited thereto, and a buzzer, a sound generator, or the like may be used.

〔Effect of the invention〕

As described above, according to the present invention, the comparison means for comparing the detected temperature of the temperature sensor and the set temperature;
A control means for controlling the heating output on and off according to the comparison result of the comparison means, a counting means for counting the number of times the temperature detected by the temperature sensor reaches the set temperature, and when the count value of the counting means reaches the set value. Since we have installed a notification means to notify that the pot is at the appropriate temperature, even if the optimum temperature period varies depending on the size of the pot, the amount of food in the pot, or even the type, the appropriate temperature state can be detected accurately and quickly. This can prevent the food in the pot from being left in a high temperature state for a long time, and also prevent unnecessary consumption of electricity, which is particularly important in terms of safety when cooking fried foods using oil. It is possible to provide an induction heating cooker that has excellent practical effects, such as being extremely advantageous.

[Brief explanation of the drawing]

Fig. 1 is a diagram for explaining the operation of one embodiment of the present invention, Fig. 2 is a configuration diagram of the main part of the control circuit in the same embodiment, and Fig. 3 is the operation when the pot is small in the same embodiment. FIG. 4 is a configuration diagram showing a modification of the control circuit in the same embodiment,
FIG. 5 is a flowchart for explaining the operation of the modified example, FIG. 6 is an overall configuration diagram of an embodiment of the present invention and a conventional induction heating cooker, and FIG.
FIG. 8 and FIG. 9 are diagrams for explaining the operation of the conventional induction heating cooker, respectively. 2... Top plate, 3... Pan, 4... Temperature sensor, 6... Temperature setter, 24, 27... Comparator, 26... Counter, 7... Appropriate temperature display section (notification means), 8... ...Light emitting diode.

Claims (1)

[Scope of Claims] 1. In an induction heating cooker that induction heats a pot on a top plate by applying a high-frequency magnetic field to the pot, a device is provided on the back side of the top plate to detect the temperature of the pot on the top plate. a temperature sensor, a comparison means for comparing a temperature detected by the temperature sensor with a set temperature, a control means for controlling heating output on and off according to a comparison result of the comparison means, and a temperature detected by the temperature sensor is set. An induction heating cooker comprising: a counting means for counting the number of times the temperature is reached; and a detecting means for notifying that the pot is at a proper temperature when the count value of the counting means reaches a set value. 2. The induction heating cooker according to claim 1, wherein the comparison means, control means, counting means, and notification means are microcomputers.