JPH0255917B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to an induction heating cooker having a temperature control function.

(b) Conventional technology Conventionally, temperature control using an induction heating cooker involves installing a temperature detecting means such as a thermistor on the back of the top plate on which cooking utensils such as a pot are placed, and using the temperature detecting means to detect the heat received from the cooking pot. This is accomplished by detecting the temperature, comparing the detected temperature with a set temperature by the temperature setting means, and controlling the oscillation of the switching element so that the detected temperature and the set temperature become equal. A cooker having such a configuration is excellent in terms of low cost and ease of use.

However, as mentioned above, such induction heating cookers are configured with a temperature detection means on the back of the top plate, so if a pot with high thermal conductivity is used with the center of the bottom raised, There is a delay in the transmission of heat from the bottom of the pot to the temperature detection element, and at the beginning of cooking, the temperature of the pot is higher than the temperature T _A detected by the temperature detection means, and the temperature T _B of the food increases accordingly. As shown in FIG. 2, there was a problem in that the temperature of the food in the pot could not be accurately maintained at a predetermined temperature T. In addition, although the bottom of the pot is flat, if the pot is made of a material with poor thermal conductivity, the cooking temperature inside the pot may be lower than the detected temperature T _A detected by the temperature detection means at the beginning of cooking. There was an inconvenience that the material temperature T _B became low as shown in Figure 4.

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 Patent Application Laid-Open No. 1983-1987 developed a technology to display light emitting light while assuming that the temperature was stable.
This is shown in Publication No. 91690.

(c) Problems to be solved by the invention However, in the case of a pot with high thermal conductivity and whose bottom is in close contact with the top plate, even at the start of cooking, the temperature detected by the temperature detection means T _A as shown in Figure 3. The temperature of the food in the pot and the temperature of the food in the pot T _B are approximately equal, and if the temperature of the food is stabilized after a delay of 3 to 4 minutes after the detected temperature reaches the set temperature, unnecessary power and heating time will be wasted. There was a problem with becoming.

The present invention is not affected by the type of cooking utensil, and aims to immediately notify when the temperature of the food to be cooked almost reaches the detected temperature, thereby eliminating undesirable power consumption and wasting of heating time. do.

(d) Means for solving the problem Temperature detection means for detecting the temperature of cooking utensils via the top plate, temperature setting means for setting the temperature, and temperature detection means and temperature setting means for the temperature detection means. a comparison means for comparing the set temperatures; an operation control means for controlling the operation of the switching element so that the detected temperature becomes equal to the set temperature based on the output from the comparison means; and a delay means for performing a delay operation for a desired time until the temperature of the food in the cooking utensil has almost reached the detected temperature; and a speed detection means for detecting the rising speed of the temperature detected by the temperature detection means.

(E) Effect Since the desired time for the delay in the delay means is changed according to the rising speed of the detected temperature detected by the speed detection means, the temperature of the food in the cooking utensil is exactly at the detected temperature. It is possible to notify when the situation has changed.

(C) Embodiment FIG. 1 is a block circuit diagram of the induction heating cooker of the present invention, and FIG. 5 is a front view of its operating section. In these figures, 1 is a full-wave rectifier circuit that full-wave rectifies the AC power supply voltage, 2 is a choke coil connected to the output terminal of this full-wave rectifier circuit 1, and 3 is a filter capacitor that constitutes a filter circuit together with this choke coil 2. , 4 is an induction heating coil connected to one end of this filter capacitor 3, 5 is a resonant capacitor that forms a resonant circuit together with this induction heating coil 4, and 6 is a switching element such as a transistor connected in parallel to this resonant capacitor 5. , 7 are damper diodes connected in antiparallel to this switching element, and the inverter circuit is constituted by these damper diodes 2 to 7. 8 is AC to the above full wave rectifier circuit 1
an input detection circuit connected to a current transformer 9 that detects input power, and detects input power to the inverter based on a signal from the current transformer 9;
Reference numeral 10 denotes a level setting means for changing the signal level by changing the divided voltage value of a predetermined voltage, which is linked to the adjustment knob 11 and used for both output setting and input setting. 12 is a maximum power setting means for setting the maximum power; 13 is a maximum temperature setting means for setting the maximum temperature setting; 14 is a control selection knob for switching between output control and temperature control; 15. The display on the temperature control display section 16 is switched. 17, 18, and 19 are the first ones that switch in conjunction with the operation of this control selection knob;
These are the second and third changeover switches. These first, second and third changeover switches 17, 18, 19
When the control selection knob 14 is operated to the output control (heating) side, the level at the level setting means 10 is given as the set input power, and the maximum set temperature from the maximum temperature setting means 12 is given as the set temperature. On the other hand, when the control selection knob 14 is operated to the temperature control (tempura) side, the maximum set power in the maximum power setting means 13 is given as the set power, and the level in the level setting means 10 is given as the set temperature. It will be done. 20 is cooking pot 21
The temperature detection means is composed of a thermistor (not shown), etc., which is pressure-welded to the back surface of the ceramic top plate 22 that serves as a mounting plate for the pot 21 through the top plate 22.
Detects the temperature of and outputs this detected temperature. 23
indicates an A/D conversion circuit that A/D converts the above input power, set power, set temperature, and detected temperature at different timings, and A/D converted input power value, set power value, set temperature value, and detected temperature. The values are respectively the first, second, third and fourth latch circuits 24, 25,
It is outputted via 26 and 27. 28 is the first above
The first latch circuit 24 compares the input power value from the second latch circuit 25 with the set power from the second latch circuit 25.
Comparator 29 is a second comparator that compares the set temperature value from the third latch circuit 26 and the detected temperature value from the fourth latch circuit 27. Output is given.
Reference numeral 30 indicates an oscillation control circuit connected to the drive circuit 31 of the switching transistor 6;
The output from the second comparator 28 sets the ON period length of the switching transistor 6, and the output from the second comparator 29 starts oscillation.
Control the stop. 32 is the second comparator 29
A delay circuit connected to the output is shown, and its delayed output is transmitted to the temperature control display section 16. Reference numeral 33 designates a constant temperature detection circuit connected to the fourth latch circuit 27 and receiving the detected temperature value transmitted from the temperature detection means 20 via the latch circuit 27, and the detected temperature value is connected to the level setting means 10. It is detected that a predetermined temperature lower than a settable temperature has been reached, for example 90°C. 34 is a counter that starts counting from the start of temperature control operation and stops counting upon receiving a detection signal from the constant temperature detection circuit; 35 is a delay adjustment circuit that receives the count value of this counter 34; The delay time of the delay circuit 32 is adjusted according to the count value in 35. A specific method for adjusting the delay time by this delay adjustment circuit 35 is that if the count value T is a predetermined value α<β, the delay time is set to zero if α<T<β, and if T<α, the delay time is set to zero. The time is set to a predetermined value T〓, and when T<β, the delay time is set to T〓.

In such an induction heating cooker, the input power detected by the input detection circuit 8 is connected to the A/D converter as described above.
The signal is transmitted to the first comparator 28 via the conversion circuit 23 and the first latch circuit 24. Further, the detected temperature detected by the temperature detection means 20 is detected by the A/D conversion circuit 2.
3. The signal is applied to the second comparator 29 via the fourth latch circuit 27.

In this state, control selection 14 is output controlled (heating)
When operated to the side, the output control display section 15 displays a light emitting display, and the output of the level setting means 10 linked to the level adjustment knob 11 is given as a setting output, and the A/D conversion circuit 23 and the second latch circuit 25
is applied to the first comparator 28 via. on the other hand,
The maximum temperature from the maximum temperature setting means 12 is transferred to the second
is transmitted to the comparator 29. Therefore, the first comparator 28 compares the level set by the level setting means 10 with the input power value, and the oscillation control circuit 30 controls the switching transistor 6 so that they are equal.
Adjust the ON period length. At this time, the second comparator 2
9 compares the detected temperature with the maximum temperature from the maximum temperature setting means 12, and when the detected temperature reaches the maximum temperature,
A signal is given to the oscillation control circuit 30 indicating that the cooking pot 21 has been abnormally heated, and in such a case, the oscillation control circuit 30 stops the inverter oscillation.

On the other hand, when the control selection knob 14 is operated to the temperature control (tempura) side, a light emitting display is made on the temperature control display section 16. In conjunction with this, the first, second, and third changeover switches 17, 18, and 19 are switched, and the maximum power is transferred from the maximum power setting means 12 via the A/D conversion circuit 23 and the second latch circuit 25. At the same time, the level set by the level setting means 10 is applied to the second comparison circuit 29 via the A/D conversion circuit 23 and the third latch circuit 26. Therefore, the oscillation control circuit 30 controls the switching transistor 6 by the signal transmitted from the first comparator 28.
Control so that the ON period becomes the maximum period length. On the other hand, in the second comparator 29, the level setting means 1
The set level from 0 is compared with the detected temperature from the temperature detection means 20, and when the detected temperature exceeds the set level, a signal is output, and this signal causes the oscillation control circuit 30 to stop the inverter oscillation. Therefore, the second comparator 29 and the oscillation control circuit 30 control the detected temperature to be equal to the set level. Also, for the first time after temperature control operation has started,
When the temperature detected by the temperature detection measure 20 reaches the level set by the level setting means 10, a signal is sent from the second comparator 29 to the delay circuit 32, so that the delay circuit 32 is activated. , after a predetermined time delay depending on the state of the fourth changeover switch 33 (including when the delay time is zero), a signal is given to the temperature control display section 16. As a result, the temperature control display section 16
displays a blinking display.

In addition, in this induction heating cooker, the counter 34 starts counting at the same time as the temperature cooking time, and when the temperature detected by the temperature detection means 20 reaches 90°C, a detection signal is obtained from the constant temperature detection circuit 33. This causes the counter 34 to stop counting. In other words, a count value corresponding to the rising speed of the temperature detected by the temperature detection means 20 is held in the counter 34. On the other hand, the delay adjustment circuit 35 determines the characteristics of the pot 21 based on the count value of the counter 34, and
The delay time is adjusted.

That is, here, the count value T is compared with predetermined values α and β (α<β). This α,
β is used to determine the type of pot 21 as described below. Therefore, if β<T, the heat conduction of the pot 21 itself is good and the bottom of the pot is floating, and the pot 2
A pot 2 exhibiting the characteristics shown in FIG. 2, in which heat is easily transferred to the food being cooked in the pot 1, but is difficult to transfer heat to the temperature detecting means 20.
1 is placed, and the delay adjustment circuit 3
5 sets the delay time of the delay circuit 32 to a delay time τx at which the temperature of the food to be cooked is sufficiently stabilized. In contrast,
When the count value T is in the range α<T<β, the pot 2
The heat conduction of 1 itself is good and the bottom of the pot is flat.
It is determined that the pot 21 exhibiting the characteristics shown in FIG. 3, in which the temperature of the food to be cooked and the temperature detected by the temperature detection means 20 rise in a substantially equal state, is placed, and the delay adjustment circuit 35 delays. The delay time of the circuit 32 is made zero. In other words, the blinking display is made as soon as the temperature detected by the temperature detection means 20 reaches the set temperature. Further, when the count value is T<α, the heat conduction of the pot 21 itself is poor and the bottom of the pot is flat, so that heat is difficult to transfer to the food in the pot 21 but is easily transferred to the temperature detection means 20. The delay adjustment circuit 35 determines that the pot 21 exhibiting the characteristics shown in FIG. do.

In this way, in the cooking device of this embodiment, the temperature control display section 16 blinks at the optimum timing when the temperature of the food to be cooked and the temperature detected by the temperature detection means match.

(G) Effects of the Invention As described above, in the induction heating cooker of the present invention, the rate of rise of the temperature detected by the temperature detection means is detected by the speed detection means, and the detected temperature is set according to the rate of rise of the temperature detected by the temperature detection means. Since the delay time from when the temperature is reached to when the alarm is issued is changed, no matter what type of pot is used, the alarm will be issued when the temperature of the food in the pot matches the detected temperature. This eliminates wasted heating power and unnecessary waiting time for cooking, reduces usage costs, and improves cooking efficiency through temperature control.

[Brief explanation of the drawing]

Fig. 1 is a circuit block diagram of an embodiment of the induction heating cooker of the present invention, Figs. 2 to 4 are relationship diagrams of the temperature of the food to be cooked and the temperature detected by the temperature detecting means, and Fig. 5 is a diagram of the cooker of the present invention. FIG. 3 is a front view of the operation unit of FIG. 1...Full wave rectifier circuit, 4...Induction heating coil,
5... Resonance capacitor, 6... Switching transistor, 8... Input detection circuit, 9... Current transformer, 10... Level setting means, 11... Adjustment knob, 12... Maximum power setting means, 13... Maximum temperature setting means, 14... Control selection knob, 16... Temperature control display section, 17, 18, 19, 33... Changeover switch, 20... Temperature detection means, 21... Pot,
22...Top plate, 25...A/D conversion circuit, 28,
29... Comparator, 30... Oscillation control circuit, 32...
...Delay circuit, 33...Constant temperature detection circuit, 34...
...Counter, 35...Delay adjustment circuit.

Claims (1)

[Claims] 1. A DC power supply made by full-wave rectification of AC power supply voltage, an induction heating coil coupled to this DC power supply, a resonant capacitor forming a resonant circuit together with this induction heating coil, and a resonant capacitor connected to the above resonant circuit and forming a resonant circuit. It consists of a switching element for generating a resonant current in the resonant circuit, and a diode connected in antiparallel to this switching element. By controlling the switching element ON and OFF, an oscillating current is generated in the resonant circuit, and the In an induction heating cooker that inductively heats a cooking utensil placed close to the induction heating coil via a plate, the temperature detection means detects the temperature of the cooking utensil via the top plate, and the temperature setting means sets the temperature. and a comparison means for comparing the temperature detected by the temperature detection means with the set temperature of the temperature setting means, and an operation control for controlling the operation of the switching element so that the detected temperature becomes equal to the set temperature based on the output from the comparison means. and a delay means for performing a delay operation for a desired time after the detected temperature reaches the set temperature after the start of oscillation until a state in which the temperature of the food in the cooking utensil almost reaches the detected temperature is ensured. , a notification means that issues a notification after a delay of a desired time by the delay means, and a speed detection means that detects the rising speed of the temperature detected by the temperature detection means, and the temperature detected by the speed detection means An induction heating cooker characterized in that a desired time for delaying the delay means is changed according to a rise speed of the induction heating cooker.