JP2959159B2 - Induction heating cooker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating cooker having a resonance capacitor switching means for switching a resonance capacitor of an inverter circuit.

[0002]

2. Description of the Related Art In recent years, it has been proposed to heat a cooking pot with an inverter suitable for each cooking pot by switching a resonance capacitor.

Conventionally, this type of induction heating cooker has been configured as shown in FIG. Hereinafter, the configuration will be described.

As shown in the figure, an AC power supply 1 is rectified by a diode bridge 2 and smoothed by a smoothing capacitor 3 to form a DC power supply. The heating coil 4, transistors 5 and 6, diodes 7 and 8, and a resonance capacitor 9 are provided. , 10 constitute an inverter circuit 11. Resonant capacitor 1
0 is a relay 12 constituting a resonance capacitor switching means.
To connect or disconnect the capacitor 9 in parallel. Thus, the inverter circuit 11 has two states. That is, a state in which the resonance capacitor 10 is separated from the inverter circuit 11 (hereinafter, referred to as inverter I
And a state in which the resonance capacitor 10 is connected to the inverter circuit 11 (hereinafter, referred to as an inverter II). Inverter I is adapted to heat a magnetic pan and inverter II is adapted to heat a non-magnetic pan. The output of the input current detection circuit 13 and the output of the resonance capacitor voltage detection circuit 14 are respectively input to an input AN0 of a microcomputer (hereinafter referred to as a microcomputer) 15.
And AN1 which constitute an accessory detection circuit 16 for determining whether the load is an accessory of a predetermined level or less.
4 shows the output VAN0 of the input current detection circuit 13 of each load and the output VA of the resonance capacitor voltage detection circuit 14.
9 shows the relationship of N1 (VAN0-VAN1 characteristic),
In the inverter I as shown in FIG.
In the inverter II as shown in FIG.
The area is divided by the VAN0-VAN1 characteristics of SUS304t1.6, and two of an area where the load is determined to be a small object (hereinafter referred to as small object detection) (hereinafter referred to as a small object area) and an area where the load is determined not to be a small object (hereinafter referred to as an operation area). Divided into two areas. (SUS304t1.6 means a non-magnetic stainless steel pan with a pan bottom thickness of 1.6 mm, and enamel φ20 cm means an enamel pan with a pan bottom diameter of 20 cm.) A pan detection circuit 17 for determining whether the load is a magnetic pan or a non-magnetic pan based on the operation state is connected to the microcomputer 15. The drive circuit 18
Drives the inverter circuit 11 by the output of the microcomputer 15, and the drive circuit 19 drives the relay 12 by the output of the microcomputer 15.

The operation of the above configuration will be described. First, a load (f) SUS having a load in the accessory area shown in FIG.
In the case of 304t1.8 or a load (g) knife, when started by the inverter I, the accessory detection circuit 16 determines that the load is an accessory, stops the operation of the inverter circuit 11, and starts the inverter I again after a while. Is repeated.
Next, the load is in the operation region shown in FIG.
In the case of the pot of (d), when started by the inverter I, the accessory detection circuit 16 determines that the load is not an accessory, and the load (a) enamel φ20 cm and the load (c) enamel φ8 are magnetic pans.
cm is heated by the inverter I, and the load (b) SU detected by the pan detection circuit 17 as a non-magnetic pan
S304t1.0 and load (c) SUS304t1.4 are heated by the inverter II.

[0006]

In such a conventional induction heating cooker, the load (e) SUS304t shown in FIG.
As shown in 1.6, V near the boundary between the accessory area and the operation area
In the case of a load having the AN0-VAN1 characteristic, the small object detection circuit 16 may not detect the small object with the inverter I but may detect the small object with the inverter II. The operation at this time will be described. When activated by the inverter I, the accessory detection circuit 16 determines that the load is not an accessory, and the pan detection circuit 17 detects that the load is a non-magnetic pan. Switches from inverter I to inverter II. In the case of the inverter II, the accessory detection circuit 16 determines that the load is an accessory, and stops the operation of the inverter circuit 11. As a result, the inverter circuit 11 returns to the initial state of the inverter I, starts again with the inverter I, and repeats the above operation. When such an operation is performed, the inverter circuit 11 repeats the operation of switching from the inverter I to the inverter II, returning to the inverter I, and switching to the inverter II.
Has a problem that the relay 12 is repeatedly turned on and off, and the deterioration of the relay 12 is accelerated.

An object of the present invention is to solve the above-mentioned problem, and an object of the present invention is to improve the durability of a relay by preventing a relay for connecting a resonance capacitor to an inverter circuit from operating even if a small object detecting operation is repeated.

[0008]

In order to achieve the above object, the present invention provides a heating coil for heating a cooking pot, an inverter circuit for supplying a high-frequency current to the heating coil, and a control circuit for controlling the inverter circuit. Wherein the inverter circuit includes a plurality of resonance capacitors, and resonance capacitor switching means for connecting or disconnecting at least one of the resonance capacitors to or from the inverter circuit, wherein the control circuit comprises the inverter A first operating state detecting means for detecting an operating state of the circuit; and a second operating state detecting means, wherein the resonance capacitor switching means specifies whether to connect or disconnect when starting the inverter circuit. After the start, the resonance capacitor is connected according to the output of the first operation state detecting means. The second operation state detection means determines the operation state of the inverter circuit, and stops the operation of the inverter circuit when determining that the load is a small object of a predetermined level or less. The problem solving means is that the level is easier to determine as a small one before switching the connection state of the resonance capacitor after the resonance capacitor switching means is started than after switching.

[0009]

According to the present invention, since the above-mentioned problem solving means makes it easier to detect a small object in the state of the inverter before the resonance capacitor is switched than in the state of the inverter after the resonance capacitor is switched, the state before the resonance capacitor is switched is changed. The load that has not been detected will not be detected after the resonance capacitor is switched, but if the load is started and then started, it will always be detected before the resonance capacitor is switched. Even if the operation is repeated, the relay is not repeatedly turned on and off, and the deterioration of the relay is not accelerated.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. The same components as those in the conventional example are denoted by the same reference numerals, and description thereof is omitted.

As shown in the figure, a microcomputer 20 receives an output of a small object detection circuit (first operation state detection means) 16 and an output of a pan detection circuit (second operation state detection means) 17 and a drive circuit 18. And the relay 12 is switched via the drive circuit 19 to operate the inverter circuit 11 in the state of the inverter I and the state of the inverter II. Here, in the inverter I as shown in FIG. 2A, (a) SUS304t1.4
The load is divided into a small object region and an operation region by the VAN0-VAN1 characteristic of FIG. 2B. In the inverter II shown in FIG.
-The load is divided into a small object region and an operation region by dividing by a VAN1 characteristic. Load (e) VAN of SUS304t1.6
The 0-VAN1 characteristic is a small object region in the inverter I and an operation region in the inverter II. The level at which the small object detection circuit 16 determines that the load is a small object is easier for the inverter I than for the inverter II. doing.

The operation of the above configuration will be described. First, the load (e) SUS in which the load is in the accessory area shown in FIG.
In the case of 304t1.6, (f) SUS304t1.8 or (g) knife, when started by the inverter I, the accessory detection circuit 16 determines that the load is an accessory, stops the operation of the inverter circuit 11, and after a while The operation is started again by the inverter I, the small object is detected again, and the above operation is repeated.
In this case, although the accessory detection operation is repeated, since the inverter circuit 11 remains unchanged as the inverter I, the ON / OFF of the relay 12 is not repeated. Next, in the case of the pots of the loads (a) to (c) in the operation region shown in FIG. 2, when the inverter I starts, the accessory detection circuit 16 does not detect the accessory, and the magnetic pot (a) enamel φ20 cm (C) The enamel φ8 cm is heated by the inverter I, and the load (b) SUS304t1.0 detected as a non-magnetic pan by the pan detection circuit 17 is heated by the inverter II. Further, in the inverter I, a load (d) SUS30 near the boundary between the accessory area and the operation area.
Regarding 4t1.4, if a small object is detected after starting by the inverter I, the operation becomes the same as the loads (e) to (g), and the relay 12
Is not repeated, and if no small object is detected after the start by the inverter I, the inverter circuit 11 is switched to the inverter II.
As shown in FIG. 2B, the load region (f) SUS304t1.4 is an operation region, and the load region (b) SUS304t1. The operation is the same as 0, and the one started by Inverter I becomes Inverter II
There is no small object detection after switching to.

As described above, according to the induction heating cooker according to the embodiment of the present invention, the small object region is set so that the small object can be detected more easily by the inverter I than by the inverter II. The small object detection is performed by the inverter I, and even if the small object detection operation is repeated, there is no ON / OFF operation of the relay 12, and the durability of the relay 12 does not deteriorate.

[0014]

As is apparent from the above embodiment, according to the present invention, small objects can be detected more easily before the resonance capacitor is switched than after the resonance capacitor is switched. Since the resonance capacitor switching means does not operate, deterioration of the portion used as the resonance capacitor switching means can be prevented, and a highly reliable inverter circuit can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an induction heating cooker according to one embodiment of the present invention.

FIG. 2 is a diagram illustrating a small object region and an operation region of the induction heating cooker.

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

FIG. 4 is a diagram illustrating a small object region and an operation region of the induction heating cooker.

[Explanation of symbols]

 Reference Signs List 4 heating coil 9 resonance capacitor 10 resonance capacitor 11 inverter circuit 12 relay (resonance capacitor switching means) 16 accessory detection circuit (first operation state detection means) 17 pan detection circuit (second operation state detection means)

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirofumi Noma 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-4-26094 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H05B 6/12 334

Claims (1)

(57) [Claims] 1. A heating coil for heating a cooking pot, an inverter circuit for supplying a high-frequency current to the heating coil, and a control circuit for controlling the inverter circuit, wherein the inverter circuit includes a plurality of resonance capacitors, Resonance capacitor switching means for connecting or disconnecting at least one of the resonance capacitors to or from the inverter circuit, wherein the control circuit detects first operation state detection means for detecting an operation state of the inverter circuit; ,
And a second operation state detecting means, wherein the resonance capacitor switching means is set to be either connected or disconnected when the inverter circuit is started, and outputs the output of the first operation state detecting means after the start. The second operating state detecting means determines the operating state of the inverter circuit and determines that the load is a small object of a predetermined level or less. An induction heating cooker in which the operation of step (i) is stopped, and the discrimination level is easier to discriminate as a small one before switching the connection state of the resonance capacitor after the resonance capacitor switching means is started than after switching.