JPS61128492A - 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] [Technical Field of the Invention] This invention generates a high-frequency magnetic field from a heating coil and applies it to steel, which is a load, to generate an eddy current in the pot, thereby reducing eddy current loss. This invention relates to an induction heating cooker that performs cooking using self-heating of a pot based on the above.

[Technical background of the invention and its problems]

Recently, induction heating cookers have been developed that are capable of heating not only iron and 18-8 stainless steel pots, but also aluminum and copper pots, and are already in practical use.

By the way, in an induction heating cooker, when cooking, the current generated in the pot is in the opposite direction to the current flowing through the heating coil - for this reason, a repulsive force acts between the pot and the heating coil,
If the steel (including the food) is light, there is a problem with the pot floating off the top plate.

However, if the material of the pot is iron with high magnetic permeability, the magnetic force between the pot and the heating coil is large, and a strong attractive force acts there, so even if the above repulsive force occurs, it will The pot will never float.

However, if the material of the pot has low magnetic permeability and low resistance, such as aluminum or copper, a large current is passed through the chain in order to increase the input resistance of the heating coil to the same level as that of iron. The repulsive force between them becomes extremely large. Moreover, since aluminum and copper are non-magnetic materials,
There is no magnetic attraction between the steel and the heating coil.

Therefore, in the case of light steel such as aluminum or copper, the pot will float off the top plate, and if the top plate is even slightly tilted, the pot will move on the top plate, which is dangerous. Moreover, if the pot on the top plate moves from its correct setting position, proper heating will not be possible, which will adversely affect the quality of the cooking.

[Purpose of the invention]

This invention was made in view of the above circumstances,
The purpose of this is to prevent heating while the pot is floating above the top plate, thereby improving safety and, in general, improving reliability by ensuring only proper heating is possible at all times. Our objective is to provide an excellent induction heating cooker.

[Summary of the invention]

This invention provides an induction heating cooker that generates a high-frequency magnetic field from a heating coil and applies it to a pot on a top plate to inductively heat the pot, in which the weight of the pot placed on the top plate is A weight sensor, a weight detection means for detecting the weight of the steel based on the output of the weight sensor, and a material detection means for detecting the material of the steel are provided, and if the material of the steel is aluminum or copper and the weight of the steel is Cooking is prohibited in cases where the amount is light.

[Embodiments of the invention]

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

In FIGS. 1 and 2, reference numeral 1 denotes a commercial AC power source, and a rectifier circuit consisting of a diode bridge 3 and a smoothing capacitor 4 is connected to this power source 1 via a relay contact 2b. A high frequency inverter circuit 5 is connected to the output end of this rectifier circuit, and a heating coil 6 is connected to this high frequency inverter circuit 5. Here, the high-frequency inverter circuit 5 includes a resonant capacitor that forms a resonant circuit together with the heating coil 6, and a high-frequency current is caused to flow through the heating coil 6 by exciting the resonant circuit by turning on and off a switching element. It looks like this. Furthermore, the high-frequency inverter circuit 5 has a function of detecting the phase of the high-frequency current flowing through the heating coil 6 and correcting the on/off timing of the switching element according to the detected phase to cause the resonant circuit to stably oscillate. ing.

A top plate 7 on which a pot is placed is disposed near the heating coil 6. A weight sensor 8 is provided approximately at the center of the surface of the top plate 7. This weight sensor 8 is, for example, a strain gauge, and its resistance value changes depending on the strain generated in response to pressure. Therefore, when the steel 9 is placed on the top plate 7, the resistance value of the weight sensor 8 changes depending on the weight of the pot.

On the other hand, 10 is a weight detection circuit, and the weight sensor 8 is connected to this weight detection circuit 10, and a material detection circuit 11 is also connected thereto. This material detection circuit 11 has a current transformer 12 installed in the resonant circuit to detect the high frequency current flowing through the heating coil 6, and the detected high frequency current causes the pot 9 on the top plate 7 to
This is to detect the material of the material.

Here, a specific example of the weight detection circuit 10 is shown in FIG.

In Figure 3, 20! A Wheatstone bridge 20 has the all sensor 8 as one side, and a constant DC voltage obtained from a constant voltage power supply circuit 21 is applied to the Wheatstone bridge 20 . And Wheatstone Bridge 2
The voltage ■0 generated at input resistors 21, 22 . Feedback resistor 2
3. and an operational amplifier 24, which amplifies the signal and supplies it to a non-inverting input terminal (+) of a comparator circuit 26. Further, a constant DC voltage vd is applied to a parallel circuit of a resistor 28 and a capacitor 29 via a resistor 27, and the voltage generated in the parallel circuit is supplied as a reference voltage to the inverting input terminal (-) of the comparator circuit 26. I have to. Roughly speaking, the output of the comparison circuit 26 and the material detection circuit 12
The outputs of the AND circuit 30 are supplied to both input terminals of the AND circuit 30, respectively. The output of the AND circuit 30 is NPN via the resistor 31.
The voltage is applied between the base and emitter of the type transistor 32. A constant DC voltage Vd is applied to the relay 2 between the collector and emitter of the transistor 32.

Next, the operation in the above configuration will be explained.

Place the pot on top plate γ and turn on power 1.

Then, the high frequency inverter circuit 5 operates, and a high frequency current flows through the heating coil 6. At this time, the high frequency current flowing through the heating coil 6 is detected by the current transformer 12, and the material detection circuit 1
1 detects the material of the pot 9. The material detection circuit 11
If the material of the pan 9 is iron with high magnetic permeability or 18-8 stainless steel with high resistance, a logic "0" signal will be output to the weight detection circuit 10, but if the material of the pot 9 has low magnetic permeability and low resistance. In the case of aluminum or copper, a logic "1" signal is output.

On the other hand, the weight of s19 (including the weight of the food) is applied to the weight sensor 8, and a voltage Vo corresponding to the weight of the pot 9 is generated in the Wheatstone bridge 20.

In this case, the lighter the weight of [9, the higher the voltage Vo.

Voltage VO is amplified by amplifier circuit 25 and supplied to comparison circuit 26 . In this way, if the weight of the pot 9 is below a certain value, the output of the comparison circuit 26 becomes logic "1".

Therefore, if the material 19 is aluminum or copper having low magnetic permeability and low resistance, and the weight is below a certain value, the output of the AND circuit 30 becomes logic "1" and the transistor 32 is turned on. When the transistor 32 turns on,
Relay 33 operates and contact 2b opens. When the contact 2b is opened, the operation of the high frequency inverter circuit 5 is stopped,
High frequency current no longer flows through the heating coil 6. In other words, heating operation is prohibited.

however,! Even if the material of i9 is aluminum or copper, which has low magnetic permeability and low resistance, if the weight is above a certain value, the output of the AND circuit 30 becomes logic "0" and the transistor 32 remains off.

If transistor 32 is off, relay 2 will not operate and contact 2b will remain open. Therefore,
The operation of the high frequency inverter circuit 5 continues, and the heating coil 6
The pot 9 self-heats due to the high frequency magnetic field emitted from the pot.

In addition, the material of the pot 9 may be iron with high magnetic permeability or high resistance, or 18-
8 stainless steel, the output of the material detection circuit 11 becomes logic "0", so the output of the comparison circuit 26, that is, the output of the AND circuit 30 becomes logic "0" regardless of the weight of the pot 9. Therefore, the relay 33 does not operate, the high frequency inverter circuit 5 continues to operate, and f9 self-heats due to the high frequency magnetic field emitted from the heating coil 6.

That is, when the material of the pot 9 is aluminum or copper and is light, the pot 9 is pushed against the top plate 7 by the repulsive force caused by the current generated in the pot 9 and the current generated in the heating coil 6.
If the top plate 7 is tilted, the top plate 19 will move on top of the top plate 7, creating a very dangerous situation, but heating operations in such a dangerous situation are prohibited to ensure safety. It is something to do. Moreover, since heating is prohibited when the 8119 is moved on the top plate 7, that is, when the pot 9 is deviated from the correct set position, only proper heating is possible at all times, improving reliability.

In the above embodiment, only one weight sensor 8 was provided on the top plate 7, and the weight of the pot 9 was directly applied to this weight sensor 8, but as shown in FIGS. 4(a) and (b), Alternatively, a plurality of weight sensors 8, for example, four weight sensors 8, may be provided between the top plate 7 and the casing of the cooking device, and the weight of the pot 9 may be indirectly applied to these weight sensors 8 via the top plate 7. good. Further, the weight sensor 8 may be embedded in the top plate 7. Although a case has been briefly described in which a strain gauge is used as a weight sensor, the present invention is not limited thereto, and for example, a pressure sensitive diode, a pressure sensitive transistor, or a device using a spring may be used.

In addition, this invention is not limited to the above-mentioned embodiment, and it goes without saying that various modifications can be made without changing the gist.

〔Effect of the invention〕

As described above, according to the present invention, there is a weight sensor to which the weight of the pot placed on the top plate is applied, a weight detection means for detecting the weight of the steel based on the output of the weight sensor, and a detection means for detecting the material of the steel. Since the present invention includes a material detection means for detecting the material and a control means for controlling the heating operation according to the detection result of the material detection means and the detection result of the weight detection means, heating can be performed while the pot is floating on the top plate. This makes it possible to improve safety and provide a highly reliable induction heating cooker that always enables proper heating.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an embodiment of the present invention, Fig. 2 is a top plate and weight sensor shown in Fig. 1 viewed from above, and Fig. 3 is a diagram of the weight detection circuit in the same embodiment. The specific configuration diagrams, FIGS. 4(a) and 4(b), show a modification of the same embodiment, where (a) is a side view of the top plate and weight sensor, and (b) is a diagram of (a). It is a view seen from above. 6...Heating coil, 7...Top plate, 8...
・Weight sensor, 9... Pot, 10... Weight detection circuit,
11...Material detection circuit. Applicant's agent: Bench/Built-in Takehiko Suzue Figure 4 (a) (b)

Claims (1)

[Claims] In an induction heating cooker that generates a high-frequency magnetic field from a heating coil and applies it to a pot on a top plate to inductively heat the pot, a weight sensor that measures the weight of a pot placed on the top plate; weight detection means for detecting the weight of the pot based on the output of the weight sensor;
Induction heating cooking characterized by comprising a material detection means for detecting the material of the pot, and a control means for controlling the heating operation according to the detection result of the material detection means and the detection result of the weight detection means. vessel.