JPS61233988A - 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 Field of Industrial Application The present invention relates to an electric oven type induction heating cooker used in general households.

BACKGROUND OF THE INVENTION Conventionally, this type of induction heating cooker has attracted general attention because of its merits such as safety and cleanliness because it is a flameless cooker.

However, since the price is too high for a function that only allows heating and cooking, it has not become widespread, and since the direction of price reduction has reached its technical limit, it can be said that there will be a trend toward adding more functions in the future.

One of the current features is the temperature control function (for tempura, heat retention, etc.) or the timer function, but recently other functions (for example, boiling detection function...・It is desired for this induction heating cooker to notify when the water in the pot boils, etc., and the means to do so has become a technical issue.

Conventionally, the method generally used as a boil detection function is to bring a temperature-sensitive element such as a thermistor into direct contact with or in close proximity to the pot, which is the object to be heated, until the temperature of the pot reaches 10.
The point at which the temperature stabilized at 0'C was defined as a boiling state.

However, when this means is applied to an induction heating cooker, the configuration is as shown in FIG. 4, the detection performance is significantly poor, and the detection characteristics are affected by the degree of depression d in the bottom of the pot 2, the thickness T of the bottom of the pot 2, etc. Figure 4 shows this situation in the form of a temperature graph.

In the same figure, & is the characteristic when the degree of depression d in the bottom of the pot 2 is significant, and even if the water temperature reaches 100° C., the detection part temperature B does not reach the set value and a detection delay time td occurs. The same picture Suha pot 2
This characteristic occurs when the bottom thickness T is large, and because the heat capacity of the pot 2 is large and the bottom thickness Tp is large, the temperature at the bottom of the bottom (top plate 3 side) and the top surface temperature of the bottom (water side) are different. Due to the difference, the detection part temperature B reaches the set value first, and the water temperature is ts.
The temperature would reach 100'C after waiting time. In this way, simply detecting that the detection part temperature B has reached a predetermined value may result in early detection or delayed detection.

Problems to be Solved by the Invention It goes without saying that this problem can be considerably improved by bringing the temperature sensing element 1 as close as possible to the object to be detected (water in this case); , make a hole in the top plate 3 and force the temperature sensing element 1 to protrude above the top plate 3 so as to contact the bottom surface of the pot 2, or make the temperature sensing element 1 into a probe shape and insert it into the water in the pot 2. This means that the biggest advantage of induction heating cookers, such as cleanliness and ease of cleaning, will be significantly impaired.

The present invention has been made in view of this point, and an object of the present invention is to provide an induction heating cooker that realizes boiling detection with a simple configuration without impairing the cleanliness of the induction heating cooker.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a vibration detection section that indirectly detects vibrations generated in or on the pot during boiling, and uses signals from the vibration detection section to detect heating. The output is reduced to enter a heat retention state, or a display or notification is provided.

Function The present invention detects the boiling state of the water in the pot by detecting the boiling state of the water in the pot as the vibration of the pot, as well as the vibration of the top plate or the vibration of the housing, regardless of the temperature of the top plate. Therefore, the boiling state can be reliably detected.

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

In the figure, 6 is a pot which is an object to be heated, which is placed on the top plate 6, and a heating coil 7 placed at the bottom of the top plate 3.
A high-frequency magnetic field is supplied to generate heat through induction heating, and the water 8 contained therein is heated by the heat and boils. Further, reference numeral 9 denotes a high frequency power supply section which supplies a high frequency current to the heating coil 7, and is configured so that its output is controlled by a control circuit 1o. Reference numeral 11 denotes a vibration detection unit that monitors the vibration of the top plate e, detects the vibration that occurs when water 8 in the pot 5 boils, outputs it to the control circuit 1o, and outputs it to the high frequency power supply unit 9. Operating or displaying or informing unit 1 to reduce or stop the output
3 to inform the user that the water 8 in the pot 6 has boiled. Reference numeral 12 denotes a vibration detection section, which is replaced by a high frequency power supply section 9 instead of the top plate 6. It shows a state where it is attached to a housing 14 that houses the heating coil 7 and the display or notification section 13, and its operation is the same as that of the vibration detection section 11. - Figure 2 shows frequency analysis graphs of vibrations 15 when the water 8 is not boiling and 16 when it is boiling. As can be seen from this, there is a large difference in the frequency band from 2KHz to 12KHz.

Normally, induction heating cookers have a high frequency power supply section 9 made up of an inverter that oscillates at 20 to 50 KHz, so a considerable level of vibration occurs at a vibration wave number that matches the oscillation frequency. Of course. Therefore, in boiling detection according to the present invention, it is necessary to detect vibration frequency components lower than the oscillation frequency.

Effects of the Invention As described above, according to the present invention, boiling detection can be realized with an extremely simple configuration, and the detection delay, which was a serious problem with the conventional temperature detection method in induction heating cookers, can be realized. , it is possible to completely solve problems such as early detection, accurately detect when boiling occurs, and notify the user whether to switch to the warm state or not.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an induction heating cooker according to an embodiment of the present invention, Fig. 2 is a vibration frequency analysis graph according to an embodiment of the present invention, and Fig. 3 is a boiling detection configuration of a conventional induction heating cooker. Block Diagram. FIGS. 4a and 4b are graphs showing the detection characteristics. 6... Pot %6... Top plate, 7... Heating coil, 8... Water, 9... High frequency power supply section, 10... ...Control circuit, 11.12...
...Vibration detection section, 13...Display/notification section, 14
・・・・・・Hedron. Name of agent: Patent attorney Toshio Nakao and 1 other person
3rgJ Figure 4 (a) 7M56 at one time in Ichirinin!・・・Jinn Aiko 2...Oke 3...Chan Sales 4...jJrJ Hot Koi 4/

Claims (2)

[Claims] (1) A top plate on which an object to be heated is placed, a heating coil placed below the top plate that supplies a high-frequency magnetic field to the object to be heated and heats it by induction, and a high-frequency coil that supplies a high-frequency current to the heating coil. It has a power supply unit, a casing that houses the high-frequency power supply unit and the heating coil, a vibration detection unit that detects vibrations of the top plate or the casing, and a control circuit that controls the high-frequency power supply unit, An induction heating cooker that stops or reduces the output of the high frequency power supply section, or displays or notifies the output of the high frequency power supply section via the control circuit in response to a signal from the vibration detection section. (2) If, among the vibration frequency components of the top plate on which the object to be heated is placed, a component lower than the oscillation frequency of the high-frequency power supply exceeds a predetermined value, whether to stop or reduce the output of the high-frequency power supply; Alternatively, the induction heating cooker according to claim 1, which displays or informs.