JPS61190889A - 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 B) Industrial Application Field The present invention relates to an induction heating cooker having a temperature control function.

(B) Conventional technology Conventionally, temperature control in induction heating cookers f; involves installing temperature detection means such as a thermistor on the back of the top plate on which cooking utensils such as pots are placed, and detecting the temperature of the heat received from the cooking pot. Detected by means,
This detected temperature is compared with the set temperature by the temperature setting means, and the oscillation of the switching element is controlled so that the detected temperature and the set temperature are equal. A cooker having such a configuration is excellent in terms of low cost and ease of use.

However, as mentioned above, such an induction heating cooker has the configuration C in which the temperature detection means is provided on the back of the top plate, so if a pot with high thermal conductivity is used with the center of the bottom raised, the bottom of the pot Since the heat transfer is delayed, the temperature of the pot becomes higher than the temperature Tth detected by the temperature detection means at the beginning of cooking, and the temperature TB of the food increases accordingly. , as shown in Figure 2 C; 1 in the pot
The temperature of the JI4 physical object greatly exceeded the set temperature TreC, and there was a risk of power loss or fire. In addition, although the bottom of the pot is flat, if the pot is made of a material with poor thermal conductivity, the food in the pot may be lower than the detected temperature Tth detected by the two-temperature detection means at the initial stage of cooking. Temperature TB
There was an inconvenience that the value was lower than C as shown in Fig. 3.

For this reason, after a predetermined time delay of about 3 to 4 minutes after the temperature control operation is started in the induction heating cooker and the detected temperature detected by the temperature detecting means reaches the set temperature for the first time, the food in the cooking utensil is Japanese Unexamined Patent Publication No. 59-91690 discloses a technique for performing light emitting display while assuming that the temperature is stable.

(c) Problems to be solved by the invention However, in the case of a pot whose thermal conductivity is flat and whose bottom is in close contact with the top plate, cooking starts at temperature C; Temperature Tth and v inside the pot! 4. If the temperature TB of the food is approximately equal and the detected temperature is the set temperature, the stable temperature of the food is displayed after a delay of 5 to 4 minutes after the difference, resulting in unnecessary waste of power and heating time. There was a problem.

2) Means for solving the problem Temperature detection means for detecting the temperature of cooking utensils through the top plate;
A temperature setting means for setting the temperature, a comparison means for comparing the temperature detected by the temperature detection means and the set temperature of the temperature setting means, and an output from the comparison means such that the detected temperature becomes equal to the set temperature C; an operation control means for controlling the operation of the switching element, and a shift means for looking at the state of change in the detected temperature after the start of heating and before the detected temperature reaches the set temperature, and shifting the set temperature t in accordance with the detected state C2. It is set up.

E) Function: At the start of heating, the detected temperature is shifted to the set temperature (2) shifted by the shift means, so that the temperature of the food to be cooked can approach the set temperature (;) in a stable state.

f) Embodiment FIG. 1 is a block diagram showing an embodiment of the induction heating cooker of the present invention, in which (1) shows an induction heating coil (2).

Resonant capacitor (3), switching transistor (4)
), a damper diode (5), etc., and a switching transistor (4) vON, O
FF C: From induction heating coil (2) g: Supplying high frequency current, this heating coil (2) C top plate (6)
A cooking pot (7) placed close to the cooking pot (7) is heated by induction. (8) is an input power detection circuit that detects the input power to the inverter (1), and (9) is an input power detection circuit that detects the input power to the inverter (1).
), (IG is a temperature detection circuit consisting of a series connection of a thermistor υ and a resistor (1z) that detects the temperature of the pot (7) from the back of the top plate (6), ( I3 is a temperature setting circuit that sets the temperature of the pot (7), a4 is an input power detection circuit (8), an input power setting circuit (9), a temperature detection circuit a1, and a temperature setting circuit α3.
An analog multiplexer that selects the signal from A/
D conversion circuit (A/D conversion is performed in L9. This A/D
Conversion circuit (input power control means that controls the input power by comparing the detected power given by the 1st eagle with the set power, temperature control means that controls the temperature by comparing the detected temperature and the set temperature, and a temperature control means that controls the time) When heating is selected by the operation mode selection means a, the input power control means operates, and the switching element (4) is turned ON for a certain period of time. When the ON period data pcon is adjusted and the heat retention mode is selected, the set input power w4aoW is set so that the heating output is low.
r; to maintain the heating state. In addition, the operating element 1)
When η is Tempura C; the set input power is set to the highest level 1.
300 Wc and the temperature control means also operates to adjust the set temperature T r e f to 1. ．． When Tref>Tth(D, an oscillation start signal is generated to start the heating operation by inverter C2, and when Tref≦Tth, an oscillation stop signal is generated to stop the heating operation by inverter C2.
This microcomputer (18C is the set temperature Tref
A calculation means for calculating a lower predetermined temperature Tl (for example, Tt-Tref/2), a means for stopping oscillation when the detected temperature Tth becomes Tl (two consecutive times and observing the change ΔTm of this Tth, and a means for calculating the change ΔTm in this Tth); = Depending on the set temperature TrefyT'
refI: Shifting means and detected temperature Tt after re-oscillation
After h reaches T'refc, return the set temperature to the original T r
e f t ; means for returning. (L
8 is a notification means such as a display device, a buzzer, etc., which operates based on a notification signal from the microcomputer. The switching transistor (4) t'ON,
An FF operation control circuit is shown, and the start and stop of oscillation of the inverter circuit (1) is controlled by the oscillation start and stop signal C from the microcomputer (Ie).

In such an induction heating cooker i, when a heating state is selected by the operation mode selection means (one knife), the input control means in the microcomputer (Ie) operates, and the detected input power and the set input power are compared. The ON period data Pcon is adjusted so that the detected input power becomes equal to the set input power C, and the operation control circuit (lI controls the operation of the switching transistor (4) a-r according to this f1. When the heat retention mode is selected by the operation mode selection means, the set input power is set to a low level, for example 400 W, in the microcomputer αQ, regardless of the setting by the input power setting means (9), and the same operation as described above is performed. I do.

This (on the other hand, when the sky mode is set by the operation mode selection means C1?+, the set input power level in the microcomputer (Ie) The level is set to, for example, 1300W, and the power control means accordingly performs heating control of 1300W.At the same time, the temperature control means in the microcomputer αe operates, and the Comparison of the given detected temperature Tth and set temperature Trefg 1. When "t", Tref(Tth) is reached, an oscillation stop signal is sent to the operation control circuit α
When f is heard, an oscillation start signal is sent to the operation control circuit α■. In this way, the temperature of the pot (7) is controlled by intermittent oscillation of the inverter circuit (1).

In addition, this temperature control operation t:@shi, from the set temperature Tref, if the temperature is smaller than this, T1=Tref/29
·calculate. This T1 and the detected temperature Tth are constantly compared, and when the detected temperature Tth reaches T1, the oscillation is temporarily stopped, and this state is detected for a predetermined period of time ΔTm, and whether ΔTm is 4 or not? compare.

If this ΔTm is zero, the pot (
It is determined that the detected temperature Tth of the pan 71 and the temperature of the food such as cooking oil in the pot (71) are approximately equal, and the set temperature [Tref is not changed and oscillation is started again.Then, the detected temperature Tt
When h reaches the set temperature TrefC, the oscillation of the inverter is stopped, and a C2 notification signal is sent to the notification means α to notify fti, sound, etc., and after that, the detected temperature Tref
Temperature control is performed so that th is maintained at the set temperature TrafC2.

On the other hand, if the above ΔTm is not zero, FIG. 3 or 4 C
It is determined that the detected temperature Tth of C2 set (7) and the temperature of the food to be cooked are different by adding two, and the set temperature TrefyT'r is set.
ef (T'ref-Tref- to ΔTm: is a constant), compares the detected temperature Tth and T'ref, and when this Tth reaches T'refs2, the dual inverter oscillation is stopped. 2. The notification signal is sent to the notification means 0 seconds, and 1 notification such as light emission, sound generation, etc. is performed.

That is, in the case shown in FIG. 3 where the temperature of the food to be cooked is lower than the detected temperature Tth, ΔTm is negative C2.

T'ref=mTref−, ΔTm is Tref
) is set high and the temperature of the food being cooked is higher than the detected temperature as shown in Fig. 4, ΔTm becomes positive and Ttre
ΔTm is set to Trefjp lower than fss+Trsf-, and when Tth becomes TIref, the temperature of the cooked food becomes T.
k is adjusted by an appropriate positive number l2 so that refc. Then, in this way, the detected temperature Tth is TIref(=
Each time the oscillation stops, the above T/ref y is gradually brought closer to ≦2 Trefc, and finally C2 is the original set temperature T.
Return to refc. A flowchart illustrating these operations is shown in FIG.

In this embodiment, heating is temporarily stopped and the heating state is observed, but the shift state of the set temperature may be determined by observing ΔTm corresponding to the integrated power from the start of heating.

[Effects of the Invention] As mentioned above, the induction knife n-thermal cooker of the present invention shifts the set temperature by looking at the state of temperature change before the detected temperature reaches the set temperature, so that the temperature of the food to be cooked can be set stably. Button]; Since the C2 button is moved closer to the
It also prevents power loss and abnormally high temperatures of cooked food.
Also, the inconvenience that it takes ≦2 hours to adjust the temperature of the p4 filling to the preset temperature due to insufficient heating, which increases the waiting time for the truth, is also eliminated.

[Brief explanation of drawings]

Fig. 1 is a circuit block diagram of the induction heating cooker of the present invention;
Figures 4 to 4 show changes in the temperature detected by the cooker of the present invention and the temperature of the food to be cooked. Figure 5 is a flowchart showing the operation of the cooker of the present invention. Figures 6 to 88 are conventional Cooker C;
FIG. 3 is a characteristic diagram showing changes in the detected temperature and the temperature of the food to be cooked. (1)...Inverter circuit, (Power...Pot, System...
temperature detection circuit, a3...temperature setting circuit, tilt...microcomputer, ■...operation mode selection means, (1
e...Notification means, function...operation control circuit.

Claims (1)

[Claims] (1) In an induction heating cooker that generates a high-frequency alternating magnetic field in an induction heating coil, the cooking utensils placed close to the heating coil are heated via the top plate. temperature detection means for detecting temperature;
A temperature setting means for setting the temperature, a comparison means for comparing the temperature detected by the temperature detection means and the set temperature of the temperature setting means, and a heating operation so that the detected temperature becomes equal to the set temperature based on the output from the comparison means. an operation control means for controlling the temperature, and a shift means for looking at the state of change in the detected temperature after the start of heating and before the detected temperature reaches the set temperature, and shifting the set temperature in accordance with this state of change. Heating cooker.