JPH0722491U - Non-contact load detection means for induction heating device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a non-contact load detecting means for an induction heating device that is small in size, inexpensive, and highly accurate. [Structure] The load detection unit 5 includes an antenna unit 6 and a load detection unit 7. The antenna unit 6 is provided in the vicinity of the switching element 3 that induction-heats the member to be heated 2 and is turned on.
The high frequency generated from the switching element 3 is detected by turning off and supplying a high frequency current to the induction heating coil L ₂ . The load detection unit 7 detects the load state in the vicinity of the induction heating coil L _{2 in} a non-contact manner based on the detection signal from the antenna unit 6.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a non-contact load detecting means for an induction heating device.

[0002]

[Prior art]

 In recent years, an induction heating device such as an electric rice cooker in which a member to be heated such as an inner pot is induction-heated by an induction heating coil has been developed and provided. In such an induction heating device, it is necessary to detect the presence or absence of the member to be heated and whether the member to be heated is normally heated from the viewpoint of heating control or safety.

Therefore, conventionally, as shown in FIG. 5, the current transformer 10 is provided near the switching element 3 to detect the voltage. That is, a large amount of current flows through the switching element 3 when the inner pot 2 is present, and a high voltage is obtained by converting the output of the current transformer 10 into a voltage, while a low voltage is obtained when the inner pot 2 is not present. Therefore, this voltage change is detected.

[0004]

[Problems to be solved by the device]

 However, the current transformer 10 is expensive and requires a large occupied space. In addition, the voltage change when detecting the presence or absence of the inner pot 2 is not stable due to the assembly accuracy, etc., so adjustment was required for each product. In view of the above problems, it is an object of the present invention to provide a non-contact load detecting means for an induction heating device that is small in size, inexpensive, and highly accurate.

[0005]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the present invention is arranged in the vicinity of a switching element for inductively heating a member to be heated by turning on / off and applying a high frequency current to the induction heating coil, and is generated from the vicinity of the switching element. It comprises an antenna section for detecting a high frequency and a load detection section for detecting a load state in the vicinity of the induction heating coil based on a detection signal from the antenna section.

[0006]

【Example】

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a part of an electric circuit of an electric rice cooker which is an induction heating device, for example. A full-wave rectified voltage is supplied to the terminals. This voltage is smoothed by the coil L ₁ and the capacitor C ₁ and then supplied to the resonance circuit 1 composed of the induction heating coil L ₂ and the capacitor C ₂ . The induction heating coil L ₂ is disposed below the member to be heated (inner pot) 2 in a non-contact manner and generates a magnetic field by energization to induction-heat the inner pot 2. Resistors R ₁ and R ₂ and a switching element 3 are connected in parallel to the resonance circuit 1. A resistor between the resistors R ₁ and R ₂ is connected to a synchronizing circuit (not shown). The switching element 3 has an IGBT 4 and a diode D _1, and the IGBT 4 is adapted to be turned on and off at high speed by a control signal from the synchronous circuit.

The high frequency generated from the IGBT 4 is detected by the load detecting means 5. The load detecting means 5 comprises an antenna unit 6 and a load detecting unit 7, and the antenna unit 6 is arranged near the IGBT 4. The high frequency in the antenna section 6 is converted into a detection voltage by the _two diodes D ₂ , D ₃ and the capacitor C ₃ , and noise is removed by the amplifier 8 to be input to the load detection section 7. It The load detection unit 7 can determine the load state based on the detected voltage, and can detect the presence or absence of the inner pot 2 by a display lamp (not shown) or the like. The antenna portion 6 can be easily manufactured by forming a pattern on the printed board P with copper foil or the like.

Next, the detection of the presence or absence of the inner pot 2 by the load detecting means 5 of the induction heating device having the above-mentioned configuration will be described. That is, the detected voltage is displaced as shown in C of FIG. 3 when the inner pot 2 is present, and is displaced as shown in C of FIG. 4 when it is not present. Therefore, by setting the threshold value to 2.8 V, for example, if the detection voltage is lower than this threshold value, it can be determined that there is an inner pot, and if it is higher, it can be determined that there is no inner pot 2. .

In addition, in the case where a small magnetic material such as a spoon is erroneously arranged near the induction heating coil L ₂ instead of the inner pot 2 by newly providing a small object detection threshold value outside the threshold value. Can be detected. That is, since the detection voltage of a small magnetic material is higher than that of the inner pot 2, a value higher than the detection voltage obtained by a magnetic material that may be erroneously placed is used as the small object detection threshold. do it.

[0010]

[Effect of device]

 As is clear from the above description, the load detecting means of the induction heating device according to the present invention has a simple structure in which only a diode or the like is provided, and therefore, it is cheaper than the conventional transformer. And it can be manufactured compactly. In addition, since the change in the detection voltage appears remarkably depending on the load condition, the accuracy is higher than in the past, and it is possible to determine not only the presence or absence of the member to be heated but also the small magnetic material.

[Brief description of drawings]

FIG. 1 is a partial electric circuit diagram of an induction heating device according to an embodiment.

FIG. 2 is a partial perspective view of a printed circuit board on which the electric circuit of FIG. 1 is provided.

FIG. 3 is a graph showing a relationship between time and detected voltage when there is a member to be heated.

FIG. 4 is a graph showing the relationship between the detection voltage and the time when there is a small member to be heated.

FIG. 5 is a partial electric circuit diagram of an induction heating device according to a conventional example.

[Explanation of symbols]

3 ... switching device, 4 ... IGBT, 5 ... load detecting means, 6 ... antenna unit, 7 ... load detector, L ₂ ... induction heating coil.

Claims (1)

[Scope of utility model registration request] 1. An antenna unit arranged near a switching element for inductively heating a member to be heated by turning on / off a high-frequency current to the induction heating coil and detecting a high frequency generated near the switching element. And a load detecting section for detecting a load state in the vicinity of the induction heating coil based on a detection signal from the antenna section, the non-contact load detecting means of the induction heating apparatus.