JP2003178861A - Induction heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating cooker with a superb compliance with detection of load temperature. <P>SOLUTION: By providing an output control means 18 for controlling an output of an inverter 14 and a load temperature detection means 19 for detecting temperature or its change of a load 15 through detection of a volume of an object for control or its change controlled by the output control means 18, compliance with detection of load temperature is improved as compared with a case where temperature detection of a load is performed with a thermistor or the like. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an induction heating cooker,
In particular, the present invention relates to a cooker for inductively heating a load made of a low resistance metal such as aluminum or copper.

[0002]

2. Description of the Related Art A conventional induction heating cooker will be described below with reference to FIG. The commercial power source 1 is rectified by the rectifying element 2, and the smoothing means 3 supplies the DC power to the inverter 4. In the inverter 4, the switching element 7 is driven to generate the high frequency magnetic field in the heating coil 6 and induce the load 5. It is to heat. Here, in order to control the power to the load 5, the output control unit 8 controls the frequency of the switching element 7, and the input detection unit 9 controls the input current. That is, in frequency control, power control is performed by changing the drive frequency of the switching element. The temperature of the load 15 is detected by providing a temperature detecting element such as a thermistor on the top plate of the cooking device.

[0003]

In the above conventional induction heating cooker, the thermal time constant of the temperature detecting portion for detecting the temperature of the load 5 is large, and the detection delay with respect to the temperature change of the load 5 occurs. . Further, when the load 5 is a metal having a low melting point such as aluminum, there is a problem that the temperature detection of the load may be delayed and the load 5 may be damaged when the load temperature rises rapidly such as when the load 5 is burned out. is doing.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide an induction heating cooker having good followability in detection of load temperature.

[0005]

In order to achieve the above-mentioned object, the induction heating cooker of the present invention detects the control target amount of the output control means for controlling the output of the inverter or the change thereof to detect the load. It has a load temperature detecting means for detecting a temperature or a temperature change.

As a result, it is possible to provide an induction heating cooker having a good followability in detecting the load temperature.

[0007]

A first aspect of the present invention is a heating coil for generating a high frequency magnetic field by an inverter to induction heat a load, an output control means for controlling the output of the inverter, and a control controlled by the output control means. By using an induction heating cooker having a load temperature detecting means for detecting a load temperature or a temperature change by detecting a target amount or a change in the load amount, the load can be detected as compared to a load temperature detecting device such as a thermistor. Good followability of temperature detection and no damage to load.

The invention described in claim 2 provides the induction heating cooker according to claim 1 for displaying or notifying the load temperature detected by the load temperature detecting means, so that the followability of the detection of the load temperature is improved. , Will be easy to use.

According to the third aspect of the present invention, the induction heating cooker according to the first or second aspect of the present invention, which controls the output of the inverter corresponding to the load temperature, has a good followability in detecting the load temperature. It has good cooking performance.

The invention described in claim 4 stops the inverter when the load temperature becomes abnormally high.
By using the induction heating cooker according to any one of 3 above, the followability of detection of the load temperature is good, and the safety is high.

[0011]

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2.

As shown in the figure, the commercial power source 11 is rectified by the rectifying element 12, and the DC power is supplied to the inverter 14 by the smoothing means 13. In the inverter 14, the switching element 17 is driven to generate a high frequency magnetic field in the heating coil 16 to inductively heat the load 15. In order to control the power to the load 15, the output control unit 18 changes the drive frequency of the switching element 17, and the input detection unit 21 that detects the input current controls the input current. That is, the output control means 18 is operated with the drive frequency as the control target amount of the inverter 14 so that the input current becomes the set value. The load temperature detecting means 19 detects a load temperature or a temperature change by detecting a controlled object amount controlled by the output control means 18 or a change thereof.

In this embodiment, a resonance capacitor is connected in series with the heating coil 16 to form a SEPP inverter. The input power characteristic has a peak of the resonance frequency of the heating coil 16 and the resonance capacitor. When a low-resistance metal such as aluminum or copper is induction-heated as the load 15, the resonance Q of the heating coil 16 and the resonance capacitor in the state where the load 15 is magnetically coupled is large, so that the drive frequency-input power characteristic of FIG. As shown, the input power changes sharply with respect to the frequency. As the temperature of the load 15 rises, the resonance Q of the heating coil 16 and the resonance capacitor Q
Becomes smaller, and the input power characteristics change as indicated by the dotted line in FIG. 2 according to the temperature change. Therefore, the output control means 18 changes the drive frequency so that the input current becomes the set value. The temperature of the load 15 is detected by detecting the change in the drive frequency by the load temperature detecting means 19.

In particular, when a low resistance metal such as aluminum or copper is induction-heated as the load 15, the resonance coil Q of the heating coil 16 and the resonance capacitor in the state where the load 15 is magnetically coupled has a large Q, so that the load 15 becomes steep with respect to the frequency. Input power changes. Therefore, it is possible to easily realize the change of the driving frequency, and the time delay of the temperature detection does not occur. That is, an induction heating cooker with good followability of load temperature detection is realized.

Further, the temperature of the load 15 can be displayed by a liquid crystal or LED (not shown), or an alarm sound or a synthetic voice can be used to notify the user of the load temperature at high speed, which is a convenient induction heating cooker. Is realized.

Further, the output control means 18 controls the output of the inverter 14 according to the output of the load temperature detection means 19 to rapidly heat the load 15 until the load temperature reaches a constant temperature, for example, which has good cooking performance. Induction heating cooker is realized.

Further, the load temperature detecting means 19 detects that the load temperature becomes abnormally high, such as heating the load 15 in the absence of food, and the inverter 14 is stopped to heat the load 15. By stopping it, the safer induction heating cooker is realized by preventing further increase in load temperature.

In this embodiment, the inverter structure is so-called SEPP, but it goes without saying that it is not necessary to be particular about this. Further, although the drive frequency is set as the control target amount in the present embodiment, the effect of the present invention can be obtained also by the on-duty of the switching element or the input voltage of the inverter. Although the input current is used as the control target, the same effect can be obtained with the output current, the heating coil voltage or current, the resonance capacitor voltage or current, or the like. Further, it goes without saying that the load temperature detection accuracy can be improved by using the temperature detection element such as the conventional thermistor and thermocouple together.

[0019]

As described above, the induction heating cooker according to the present invention detects the temperature of the load or the temperature change of the load by detecting the control target amount of the output control means for controlling the output of the inverter or the change thereof. However, the followability of the detection of the load temperature is good, and the load is not damaged.

[Brief description of drawings]

FIG. 1 is a block diagram of an induction heating cooker that is an embodiment of the present invention.

FIG. 2 is a diagram showing a drive frequency-input power characteristic of the induction heating cooker.

FIG. 3 is a block diagram of a conventional induction heating cooker.

[Explanation of symbols]

14 Inverter 15 load 16 heating coil 18 Output control means 19 Load temperature detection means 21 Input detection means

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Atsushi Fujita             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Yuji Fujii             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 3K051 AA02 AA07 AB14 AC07 AC12                       AC52 AC53 AD02 AD17 AD26                       AD28 AD29 CD03

Claims (4)

[Claims] 1. A heating coil for generating a high-frequency magnetic field by an inverter to inductively heat a load, an output control means for controlling the output of the inverter, and a load by detecting a controlled object amount controlled by the output control means or a change thereof. An induction heating cooker having a load temperature detecting means for detecting a temperature or a temperature change. 2. The induction heating cooker according to claim 1, wherein the load temperature detected by the load temperature detecting means is displayed or notified. 3. The induction heating cooker according to claim 1, wherein the output control of the inverter is performed according to the load temperature. 4. The induction heating cooker according to claim 1, wherein the inverter is stopped when the load temperature becomes abnormally high.