JP3216498B2 - Induction heating cooker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an induction heating cooker.

[0002]

2. Description of the Related Art In recent years, induction heating cookers for inducing eddy currents in the bottom of a load pan by using a high-frequency magnetic field for heating have attracted attention as clean, safe, and highly heat-efficient cooking means. Furthermore, in addition to the desktop type in which the operation and display unit is integrated with the main unit and placed on a table or the like, a built-in induction heating cooker in which the operation unit and the main unit are separated has been developed, and In order to increase the output, an induction heating cooker of AC200V input has been developed.

[0003] In this way, the equipment used with AC200V is designed so that the metal part can be grounded for safety.
In many cases, a ground wire is provided. However, there is a possibility that high frequency noise generated from the induction heating cooker may leak to the commercial power supply line via the ground wire. In addition, in the induction heating cooker of a type in which the operation / display section is separated, a high-frequency current is supplied to a connection line connecting the operation section / display section and a control circuit in the main body. In some cases, it affected electronic equipment.

Conventionally, the following measures have been proposed to solve the above problems. First, 61-
As shown in Japanese Patent No. 16621, an induction heating cooker is proposed in which an earth coil is provided between a metal case of a main body and an earth pin to prevent high frequency noise from leaking from an earth wire to a commercial AC power supply. .

[0005] Alternatively, as shown in Japanese Patent Application Laid-Open No. 3-127484, a ring core is provided so as to surround a signal line connecting a control circuit of a separately arranged operation display device and a main body frequency converter, and the signal line is provided. There has been proposed an induction heating cooker configured to suppress supply of a high-frequency component of a frequency conversion device to a signal line and suppress high-frequency noise radiated to the surroundings by a signal line serving as an antenna.

[0006] Alternatively, as disclosed in Japanese Patent Application Laid-Open No. 5-41275, a signal line connecting a frequency conversion device provided in a main body to an operation unit or a display unit which is separately arranged, and a conductive wire whose one end is grounded. An induction heating cooker is provided, which is provided with fixing means for maintaining a proximity state with a wire over a predetermined length, reduces radiation efficiency of the signal line as an antenna, and suppresses high-frequency noise radiated from the signal line to the surroundings. ing.

[0007]

However, in the conventional configuration, there has been a case where high-frequency noise of a fixed frequency is not reduced. In addition, there has been a problem in that high-frequency noise at a constant frequency increases, affects peripheral devices, and the like.

[0008] The present invention solves the above-mentioned problems, and reduces high-frequency noise that leaks to a commercial power supply or radiates to the surroundings.
It is an object of the present invention to provide an induction heating cooker in which electronic components can operate normally even when an electrostatic object comes into contact with an operation unit or a display unit which is separately arranged from a grounded main body casing.

[0009]

In the induction heating cooker according to the present invention, the signal line, the second grounding portion provided on the metal portion of the operation portion or the display portion, and the first grounding portion of the main body housing are provided. Since it has the proximity maintaining means for maintaining the proximity state with the conductive wire to be connected over a predetermined length, there is little high frequency noise leaking to the commercial power supply or radiating to the surroundings, and the operation separated from the grounded main body housing An induction heating cooker in which electronic components operate normally even when an electrostatic object comes into contact with the display unit or the display unit is obtained.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention according to claim 1 of the present invention provides a frequency converter including a heating coil, a resonance capacitor, and a switching semiconductor, a control circuit for controlling the frequency converter, a frequency converter, A main body housing for accommodating the control circuit, a first grounding portion provided on a conductive portion of the main body housing connected to the ground via a ground wire, and an operation portion or a display portion arranged at a location remote from the control circuit A signal line for electrically connecting the control unit and the control circuit; a second grounding unit provided on a metal unit of the operation unit or the display unit; and a conductive line for connecting the second grounding unit and the first grounding unit. Wire and said conductive
A proximity holding unit for maintaining a proximity state between the signal line and the signal line over a predetermined length, wherein the second grounding unit and the first
In this configuration, an inductor is inserted into a conductive line between the grounding portions.

As a result, a large potential is generated at a high frequency with respect to the ground due to the time-varying current generated when the switching semiconductor of the frequency converter is cut off or turned on and the inductance of the distribution line serving as the current path. Since the potential of the signal line connecting the control circuit for driving the switching semiconductor and the input circuit or the display circuit with respect to the ground greatly fluctuates at a high frequency,
When the length of the signal line is increased, the radiation amount of electromagnetic waves which becomes a kind of dipole antenna becomes a kind of dipole antenna. And a conductive line connecting the grounding portion of the main body and the first grounding portion of the main body housing has a proximity maintaining means for maintaining a predetermined length, so that the noise component is distributed to a signal line serving as an antenna. The high frequency flows to the ground via a capacitance distributed between a grounded conductive line and a signal line. Therefore, when the signal line connecting the control circuit and the input circuit or the display circuit is viewed as an antenna, this antenna reduces the radiation efficiency of radiating an electric field to the surrounding space, and the amount of high-frequency energy of noise radiated to the surrounding space Decrease.

On the other hand, the power supply line connecting the main body and the commercial power supply can be regarded as a kind of receiving dipole antenna. The electric field radiated from the connection line connecting the above-mentioned control circuit and the input circuit or the display circuit induces a high-frequency noise voltage between the power supply lines connecting the main body and the commercial power supply, so that the noise terminal voltage in the commercial power supply increases and However, according to the configuration of the present invention, as described above, the efficiency of the connection line serving as the radiation antenna for radiating the electric field to the space is reduced, and thus the high frequency transmitted to the power supply line is reduced. And the level of high-frequency noise leaked to the commercial power line can be reduced.

When a person charged with static electricity touches or near a conductive part provided on the operation unit or the display unit, the second grounding part connected to the conductive part passes through a conductive wire to form a main body casing. Discharged to ground via the first ground. Since the grounded conductive line and the signal line connecting the operation unit or the display unit are kept close to each other for a predetermined length, the magnetic coupling between them is large, and when static electricity stored in the human body is discharged. The spike-like discharge current flowing through the grounded conductive line induces a high voltage on the signal line by magnetic induction, and this voltage may damage the microcomputer or other semiconductors. In this configuration, the inductor is inserted into the conductive wire between the second ground portion provided and the first ground portion provided in the main body housing, so that the di / dt and peak value of the discharge current are suppressed, and The induced voltage level can be suppressed to prevent the microcomputer and other semiconductors from being destroyed.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, an inductor inserted into a conductive line between the second grounding portion and the first grounding portion is provided near the second grounding portion. , The high-frequency current flowing through the conductive wire connecting the second grounding part of the operating unit or display unit and the first grounding part of the main unit (the signal connecting the operating unit or display unit to the frequency converter of the main body) It becomes difficult to block the current transmitted to the conductive line by coupling with the distributed capacitance from the line, and the above-mentioned specific signal line and the grounded conductive line are brought close to each other so that high-frequency noise is generated from the signal line. It is possible to prevent the effect of leakage to the power supply line and the surrounding space from being reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) In FIG. 1, a power plug 1 is for connecting to a 200 V commercial power supply, has a blade for ground connection, and is provided at terminals of power supply wires 2a and 2c and a ground wire 2b. The power supply lines 2a and 2c each having a length of about 2 m are connected to the input portion of the filter 4 inside the main body housing 3 and are connected to the ground line 2a.
The terminal b is connected to the same potential part as the first ground part A provided on the metal part of the exterior part of the main body housing 3.

The display operation unit 11 includes an LED 12, a tact switch 13, and a power switch 14. LED12
Alternatively, the tact switch 13 is connected to a control circuit 9 including a microcomputer of the main body through signal lines 15a to 15d each having a length of about 2 m.
The signal lines 15a to 15d are passed through a tube 18, and a conductive line 16 and a conductive line 17
a, 17b are passed through. Both ends of the conductive wire 16 having a length of about 2 m are connected to a first grounding portion A of the main body housing 3 and a second grounding portion B provided on a metal portion of an exterior portion of the display operation portion 11. The inductor 16 is connected to the ferrite core in the main body housing 3 by winding a conductive wire around the turn two times. The power switch 14 is connected by conductive lines 17a and 17b so that one side of the AC power line input to the main body can be turned on and off.

A rectifying circuit (included in the circuit block 6) for rectifying a commercial power supply voltage, a rectified low-frequency current is supplied to the heating coil 5 and a resonance capacitor (included in the circuit block 6), and the like. A frequency converter 8 including an inverter circuit for converting a high-frequency current by a transistor 7 and the like, a filter 4 and a control circuit 9 are provided.

The operation of the induction cooking device configured as described above will be described. When the power switch 14 is turned on, the commercial power voltage input from the power plug 1 is input to the frequency converter 8 and rectified. Tact switch 13
Is pressed, the control circuit 9 inputs this signal, turns on the LED 12 of the display / operation unit 11, and sets the transistor 7
Is turned on and off, and the low-frequency DC obtained by rectifying the commercial power supply voltage is supplied to the heating coil 5 and the resonance capacitor for about 25 minutes.
A resonance current of kHz is generated and converted into a high-frequency current.

In operation, since the current cut off by the transistor 7 is a large current and has a sharp rising and falling waveform, high-frequency noise is superimposed on the emitter potential of the transistor 7 and the potential is extremely unstable with respect to the ground. It is.
The signal lines 15a to 15d are connected to the LED 12 and the tact switch 13, and the emitter potential of the transistor 7 is substantially the same. The signal lines 15a to 15d are approximately 2
m, and the potential fluctuates at a high frequency, which may cause an antenna.However, since the conductive wire 16 grounded by the tube 18 is close to the antenna, the radio wave radiation efficiency as the antenna decreases, High frequency noise radiated to the surroundings can be suppressed.

On the other hand, when a user charged with static electricity touches the conductive portion connected to the second grounding portion B of the exterior portion of the operation display portion 11, the conductive wire 16 and the first conductive line 16 extend from the second grounding portion B. A discharge current flows to the ground via the ground portion A and the ground wire 2b. When the discharge current increases, the signal lines 15a to 15d passed through the tube 18 together with the conductive line 16
Then, a high-frequency current is induced by a magnetic field generated by the discharge current, and a high-voltage is generated. This high voltage is applied to the control circuit 9
Is applied to the semiconductor element and destroyed. However, since the inductor 10 in which the conductive wire is wound around the ferrite core is provided, the rise time di / dt of the discharge current is suppressed, the voltage level induced on the signal lines 15a to 15d is suppressed, and the control circuit 9 Electronic components can be prevented from being destroyed.

As described above, according to the first embodiment, the second grounding section B provided on the metal section of the operation section display section 11 is connected to the second grounding section B and the first grounding section A. A structure is provided in which the inductor 10 is inserted into the conductive line 16 by providing a tube 18 for maintaining the proximity state between the conductive line 16 and the signal lines 15a to 15d for a predetermined length. The noise can be reduced, and the electronic components of the control circuit 9 can be prevented from being destroyed when an electrostatically charged user touches the grounded metal part of the operation display unit 11.

Embodiment 2 Hereinafter, Embodiment 2 of the present invention will be described with reference to FIG. The difference between FIG. 2 and FIG. 1 showing the first embodiment is that the grounding section B of the operation display section 11 and the main body casing 3 are different.
That is, the inductor 21 connected to the conductive line 20 connecting to the grounding section A is provided inside the operation display section 11, that is, near the second grounding section B.

With the above configuration, the first embodiment can prevent the control circuit components in the main body housing from being destroyed by the discharge current generated when the user touches the ground metal part of the operation display unit 11. Can be obtained similarly. The signal lines 15a to 15d are close to the conductive line 20, and the high-frequency components of the signal lines 15a to 15d are flowing into the conductive line 20 using the distributed capacitance therebetween as a path, and this flows from the first ground to the ground. To suppress radiation of high-frequency noise from the signal lines 15a to 15d to the space.
The inductor 1 is located near the first grounding portion of the main body housing 3 as shown in FIG.
When 0 is provided, the inductor 10 blocks or resonates the high-frequency current flowing into the ground, and the signal line 15a
Or the possibility that high-frequency noise radiated from 15d to the space cannot be suppressed.

However, as shown in FIG. 2, since the inductor 21 is provided inside the operation display unit 11, that is, near the second grounding unit B, the conductive line 2 is connected to the signal lines 15a to 15d.
Blocking of the high-frequency current flowing into zero by the inductor 21 can be made extremely small.

According to the second embodiment as described above, the second
Since the inductor 21 inserted into the conductive line 20 between the grounding portion B and the first grounding portion A is disposed near the second grounding portion B,
It is possible to prevent the control circuit components in the main body housing from being destroyed by a discharge current generated when the user touches the grounded metal part of the operation display unit 11, and to control the level of high-frequency noise radiated from the signal lines 15a to 15d by the inductor 21. Can be prevented from increasing.

In the first embodiment, the lengths of the conductive lines 16 and the connection lines 15a to 15d are set to approximately 2 m, but the present invention is not limited to this. Also connection line 1
The tubes 18 maintain the proximity of the conductive wires 16 with the wires 5a to 15d. However, the tubes 18 may be bundled and fixed with a fixed band or the like. It is desirable to maintain the proximity state near the frequency converter side, but it is not necessary to maintain the proximity state with the conductive line 16 over the entire length of the connection lines 15a to 15d.

[0027]

As described above, according to the present invention, a signal line for electrically connecting an operation unit or a display unit and a control circuit arranged at a place remote from a control circuit of a main body housing is provided. Proximity holding means for holding a proximity state of a conductive wire connecting the second grounding portion provided on the conductive portion and the first grounding portion of the main body housing over a predetermined length,
Since the inductor is inserted into the conductive wire connected between the first and second grounding portions, the leakage level of high-frequency noise is low, and the control circuit of the device can be operated even if the charged user touches the operation portion or the display portion. It is possible to provide an induction heating cooker of a type in which the operation unit or the display unit is less likely to cause a trouble such as a breakdown.

According to the present invention, it is possible to prevent the inductor inserted into the conductive line connected between the first and second ground portions from reducing the radiation noise reduction effect in the above invention. .

[Brief description of the drawings]

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

FIG. 2 is a circuit block diagram according to a second embodiment of the present invention.

[Explanation of symbols]

 2c ground wire 3 main body housing 5 heating coil 8 frequency converter 9 control circuit 10 inductor 11 operation display unit 15a to 15d signal wire 16 conductive wire 18 tube (proximity holding means) 20 conductive wire 21 inductor A first grounding portion B Second grounding part

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-114471 (JP, A) JP-A-5-41275 (JP, A) JP-A-3-127484 (JP, A) 7181 (JP, B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05B 6/12

Claims (2)

(57) [Claims] A frequency converter including a heating coil, a resonance capacitor, and a switching semiconductor; a control circuit for controlling the frequency converter; a main body housing for accommodating the frequency converter and the control circuit; A first grounding portion provided on a conductive portion of the main body housing connected by a ground wire, and a signal for electrically connecting an operation portion or a display portion disposed at a location remote from the control circuit to the control circuit. A second ground unit provided on the operation unit or the display unit; a conductive line connecting the first ground unit and the second ground unit; and a proximity of the conductive line and the signal line. An induction heating cooker comprising proximity holding means for holding a state over a predetermined length, wherein an inductor is inserted into a conductive wire between the second grounding portion and the first grounding portion. 2. The induction heating cooker according to claim 1, wherein an inductor inserted into a conductive line between the second grounding part and the first grounding part is disposed near the second grounding part.