JP2003123955A - Induction heating cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce noise from an apparatus in a simple constitution since there are problems of increasing the cost, and complicating the structure by arranging an aluminum shield material for a countermeasure against the high level noise as a result of superimposition of radiation noise in both polarity of a commercial power source since always performing operation of an inverter part in a constant period regardless of the polarity of the commercial power source in a conventional method. SOLUTION: An operation period of the inverter part in one polarity and the other polarity of the commercial power source is changed, and a difference is caused in a frequency of the radiation noise in both polarity, and as a result, the level of the radiation noise can be reduced by preventing the superimposition in the same frequency.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an induction heating cooker used in general households.

[0002]

2. Description of the Related Art Induction heating cookers are becoming popular in general households because of their features such as safety, cleanliness and high efficiency. Particularly, in recent years, a device having two or more burners has become widespread as a main cooker placed in a kitchen.

The induction heating cooker has a problem that when two adjacent burners operate at different frequencies, an offensive pan noise is generated due to interference from other burners. As a countermeasure against this, by having two or more switching elements and turning them on and off alternately, the current applied to the heating coil or the operating frequency of the inverter is made constant even if the pot material and input power change. Is proposed.

A conventional induction heating cooker will be described below with reference to FIG. In FIG. 12, 1 is a commercial power supply, 2 is a rectifier circuit for rectifying the commercial power supply 1, 3 is a heating coil, 4a and 4b are switching elements, and 5 is a switching element 4a, 4b. An inverter unit 14 for supplying the power is a control unit for controlling on / off of the switching elements 4a and 4b.

Next, the operation will be described with reference to FIG.
13A and 13B show ON / OFF patterns of the switching elements 4a and 4b. These two switching elements are provided with an off period for a certain period of time, and they are controlled to repeat on and off in sequence, and by changing the on / off ratio, various types of pots can be used and input power can be changed. It is common to do.

Further, in the steady heating state, the inverter section 5 is operated in a stable state with a constant cycle with respect to the commercial power source as shown in FIGS. 13 (c) and 13 (d).

[0007]

On the other hand, in the induction heating cooker, 100% of the magnetic flux output from the main body of the apparatus for inductively heating the pan is not absorbed by the pan.
Although it is a small part, it is radiated into space. This radiated energy may affect other devices as noise, and thus needs to be reduced.

As described above, in the induction heating cooker of the conventional example, since the inverter section is always operated at a constant cycle regardless of the polarity of the commercial power source, radiation noise in both polarities of the commercial power source is superimposed. As a result, the level becomes high, and there is a problem in that the structure is complicated at a high cost such as providing an aluminum shield member as a countermeasure.

The present invention has been made in view of the above points, and an object thereof is to reduce noise radiated from a device body with a simple structure.

[0010]

In order to solve the above-mentioned problems, the present invention changes the operating period of the inverter section in one polarity of the commercial power source and the other polarity so as to reduce the frequency of noise radiated in both polarities. By making a difference and, as a result, preventing superimposition at the same frequency, the level of radiation noise can be reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 is achieved by turning on / off a commercial power source, a rectifying circuit for rectifying the commercial power source, a heating coil, two or more switching elements, and the switching element. An inverter unit that supplies a high-frequency current to the heating coil and an ON / OFF frequency of the switching element are provided with a difference between one polarity and the other polarity of the commercial power source, and the same polarity is controlled at a constant frequency, and A polarity-dependent control unit that controls the ON / OFF of the switching element so that the input power is substantially constant in each polarity is provided. With this configuration, the operating frequency of the inverter unit with two polarities of the commercial power source is determined. Can be changed, resulting in a difference in the frequency of the radiated noise in both polarities, and superposition at the same frequency By preventing the of the is obtained by allowing the level reduction of the radiation noise.

According to a second aspect of the present invention, a commercial power source, a rectifying circuit that rectifies the commercial power source, a heating coil, and an input current detection unit that detects an input current from the commercial power source for each polarity. Two or more switching elements, an inverter section that supplies a high-frequency current to the heating coil by turning on / off the switching elements, and an on / off frequency of the switching elements between one polarity of the commercial power supply and the other polarity. And a polarity-dependent control unit for controlling the switching element to be turned on and off so that the input current is constant in each polarity, with the same polarity. This allows the input current to be controlled independently in both polarities even when the inverter is driven by changing the operating frequency in both polarities. , It is possible to control to stabilize the input current.

According to a third aspect of the present invention, the heating coil current detecting section for detecting the current applied to the heating coil for each polarity of the commercial power source and the heating coil current detected by the heating coil current detecting section are predetermined. A control unit for each polarity of the commercial power source so as not to exceed a predetermined value, and a polarity-dependent control unit for controlling on / off of the switching element so that the heating coil current is constant in each polarity of the commercial power source. Since the current applied to the heating coil can be controlled for each polarity of the commercial power source, it is possible to prevent one of the heating coil currents from becoming excessively large, and thus highly reliable control is possible.

According to a fourth aspect of the present invention, the switching element voltage detecting section for detecting the voltage applied to the switching element for each polarity of the commercial power source, and the voltage detected by the switching element voltage detecting section are predetermined predetermined values. And a polarity-dependent control unit that controls on / off of the switching element for each polarity of the commercial power source so as not to exceed a value, and controls so that the switching element voltage is constant in each polarity of the commercial power source. Since the voltage applied to the switching element can be controlled for each polarity of the commercial power source, it is possible to prevent one of the switching element voltages from becoming excessively large, and thus highly reliable control is possible.

According to a fifth aspect of the present invention, a commercial power source, a rectifying circuit for rectifying the commercial power source, a heating coil, two or more switching elements, and the heating coil by turning on / off the switching element. An inverter unit that supplies a high-frequency current, a control unit that controls the switching element at a constant frequency in one polarity, and an on-time addition unit that adds the on-time of the other polarity by a predetermined value to the on-time of the one polarity. Is provided, and the other control simply adds a predetermined value for the on-time to the on / off control of one polarity, so the frequency of both polarities is very simple. Can be changed.

According to a sixth aspect of the present invention, a commercial power source, a rectifying circuit that rectifies the commercial power source, a heating coil, two or more switching elements, and the heating coil by turning on / off the switching element are provided. An inverter unit that supplies a high-frequency current, a control unit that controls the switching element at a constant frequency in one polarity, and an off-time addition unit that adds the off-time of the other polarity by a predetermined value to the off-time of the one polarity. Is provided, and the other control only adds a predetermined constant off time to the on / off control of one polarity, so the frequency of both polarities is very simple. Can be changed.

According to a seventh aspect of the present invention, a commercial power source, a rectifying circuit that rectifies the commercial power source, a heating coil, two or more switching elements, and the heating coil by turning on / off the switching element are provided. An inverter unit that supplies high-frequency current, a control unit that controls the switching element at a constant frequency in one polarity, and an ON time and an OFF time in the one polarity are multiplied by a constant ratio to turn on the other polarity. The configuration is such that a multiplication unit for calculating the time and the off time is provided, and the on / off control of one polarity is simply the multiplication of the on time and the off time by a predetermined constant ratio. Therefore, it is possible to change the frequencies of both polarities with an extremely simple structure.

According to an eighth aspect of the present invention, in an induction heating cooker having a plurality of induction heating burners, when the frequency is changed according to the polarity change of the commercial power source, the changes are synchronized for all the burners. With this configuration, even if a difference in frequency is provided between the polarities of multiple burners, the operating frequency of each burner can always be kept the same, preventing the occurrence of interference noise due to the frequency difference. can do.

[0019]

EXAMPLES Example 1 Examples of the present invention will be described below.
A description will be given with reference to the drawings. In FIG. 1, 1 is a commercial power source, 2 is a rectifying circuit for rectifying the commercial power source 1, 3 is a heating coil, 4a and 4b are switching elements, and 5 is a switching element 4a, 4b. The inverter unit 6 for supplying the power supplies the ON / OFF frequencies of the switching elements 4a and 4b between one polarity of the commercial power source 1 and the other polarity, and controls the constant frequency at the same polarity, and Is a polarity-dependent control unit that controls on / off of the switching elements 4a and 4b so that the input power becomes substantially constant.

Next, the operation will be described with reference to FIG.
2A shows a voltage waveform diagram of the commercial power supply 1, and FIG. 2B shows an operation cycle of the inverter unit 5 at that time. When the commercial power supply 1 has a positive polarity, the cycle operates at T1 and a negative polarity. Sometimes it operates in cycle T2. As a result, as shown in (c), since the conventional configuration operates at a constant period T0, the radiation noise as the fundamental wave is concentrated and superposed on the frequency f0 of 1 / T0 and becomes a high level. On the other hand, in the embodiment of the present invention, since the period is changed to T1 and T2 depending on the polarity of the commercial power source 1, the radiation noise of the fundamental wave is also dispersed to f1 and f2 which are 1 / T1 and 1 / T2, The level can be lowered as shown. The second wave and thereafter can be reduced for the same reason.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings. In FIG.
1 is a commercial power supply, 2 is a rectifier circuit that rectifies the commercial power supply 1, 3
Is a heating coil, 4a and 4b are switching elements, 5
Is an inverter unit that supplies a high frequency current to the heating coil 3 by turning on and off the switching elements 4a and 4b,
Reference numeral 7 denotes an input current detection unit that detects the input current from the commercial power supply 1 for each polarity, and 61 provides a difference in the on / off frequencies of the switching elements 4a and 4b between one polarity of the commercial power supply 1 and the other polarity. It is a polarity-specific control unit that controls the switching elements 4a and 4b so that the input currents detected by the input current detection unit 7 are constant in each polarity at a constant frequency.

With the above configuration, even when the operating frequency is changed in both polarities of the commercial power source 1 to drive the inverter section 5, the input current can be controlled independently in both polarities, so that the input current can be controlled in a stable manner. Is possible.

(Embodiment 3) A third embodiment of the present invention will be described below with reference to the drawings. In FIG.
1 is a commercial power supply, 2 is a rectifier circuit that rectifies the commercial power supply 1, 3
Is a heating coil, 4a and 4b are switching elements, 5
Is an inverter unit that supplies a high frequency current to the heating coil 3 by turning on and off the switching elements 4a and 4b,
Reference numeral 8 is a heating coil current detection unit that detects the current applied to the heating coil 3 for each polarity of the commercial power supply 1, and 62 is a heating coil current detected by the heating coil current detection unit 8 that does not exceed a predetermined value. As described above, the polarity-based control unit controls the switching of the switching elements 4a and 4b so that the heating coil current is constant in each polarity of the commercial power source 1 while controlling the polarity of the commercial power source 1.

With the above configuration, the current applied to the heating coil 3 can be controlled for each polarity of the commercial power source 1, so that one of the heating coil currents can be prevented from becoming excessive, so that the switching elements 4a, 4b, etc. are excessively large. Highly reliable control is possible without applying a current.

(Embodiment 4) A fourth embodiment of the present invention will be described below with reference to the drawings. In FIG.
1 is a commercial power supply, 2 is a rectifier circuit that rectifies the commercial power supply 1, 3
Is a heating coil, 4a and 4b are switching elements, 5
Is an inverter unit that supplies a high frequency current to the heating coil 3 by turning on and off the switching elements 4a and 4b,
Reference numeral 9 denotes a switching element voltage detection unit that detects the voltage applied to the switching element 4a for each polarity of the commercial power supply 1, and 63
Controls on / off of the switching elements 4a and 4b for each polarity of the commercial power supply 1 so that the voltage detected by the switching element voltage detection unit 9 does not exceed a predetermined value. It is a polarity-dependent control unit that controls the polarity to be constant.

With the above configuration, since the voltage applied to the switching element 4a can be controlled for each polarity of the commercial power source 1, it is possible to prevent the switching element voltage of one polarity from becoming excessively large. Highly reliable control is possible without applying a voltage.

(Fifth Embodiment) A fifth embodiment of the present invention will be described below with reference to the drawings. In FIG.
1 is a commercial power supply, 2 is a rectifier circuit that rectifies the commercial power supply 1, 3
Is a heating coil, 4a and 4b are switching elements, 5
Is an inverter unit that supplies a high frequency current to the heating coil 3 by turning on and off the switching elements 4a and 4b,
Reference numeral 10 is a control unit that controls the switching elements 4a and 4b at one frequency with a constant frequency, and 11 is an ON time addition unit that adds the ON time of the other polarity by a predetermined value to the ON time of the one polarity. The operation will be described with reference to FIG. FIG. 7A
Shows the time chart of the commercial power source 1, (b) shows the on time of the switching element 4b at that time, and (c) shows the off time. As shown in (b), a predetermined value t3 is added to the ON time T3 for one polarity on the other side. As a result, it is possible to change the frequencies of both polarities with a simple structure.

(Embodiment 6) A sixth embodiment of the present invention will be described below with reference to the drawings. In FIG.
1 is a commercial power supply, 2 is a rectifier circuit that rectifies the commercial power supply 1, 3
Is a heating coil, 4a and 4b are switching elements, 5
Is an inverter unit that supplies a high frequency current to the heating coil 3 by turning on and off the switching elements 4a and 4b,
Reference numeral 10 is a control unit that controls the switching elements 4a and 4b at a constant frequency in one polarity, and 12 is an off time addition unit that adds the off time of the other polarity by a predetermined value to the off time of one polarity. The operation will be described based on 9. 9A shows a time chart of the commercial power supply 1, FIG. 9B shows an ON time of the switching element 4b at that time, and FIG. 9C shows an OFF time. As shown in (c), the off time T in one polarity
On the other hand, a predetermined value t6 is added to 6. As a result, it is possible to change the frequencies of both polarities with a simple structure.

(Embodiment 7) A seventh embodiment of the present invention will be described below with reference to the drawings. In FIG. 10, 1 is a commercial power source, 2 is a rectifying circuit for rectifying the commercial power source 1, 3 is a heating coil, 4a and 4b are switching elements, and 5 is a switching element 4a, 4b. Is a switching element 4a having one polarity,
The control unit for controlling 4b at a constant frequency, 13 is for the on time and the off time in one polarity determined by 10,
It is a multiplication unit that calculates the on-time and off-time of the other polarity by multiplying by a fixed ratio.

Next, the operation will be described with reference to FIG. 11A shows a time chart of the commercial power supply 1, FIG. 11B shows an ON time of the switching element 4b at that time, and FIG. 11C shows an OFF time. As shown in (b) and (c), the ON time T7 in one polarity is obtained by multiplying the other by a predetermined value p, and similarly, the OFF time of 4b is also obtained by multiplying T8 by q. . As a result, it is possible to change the frequencies of both polarities with a simple structure.

(Embodiment 8) An eighth embodiment of the present invention will be described below. The present invention relates to an induction heating cooker having a plurality of induction heating burners, and when changing the frequency according to the polarity change of the commercial power source described in Example 1, Example 5, Example 6 and Example 7, This burner is configured to synchronize its changes, and even if a plurality of burners have a difference in frequency between polarities, the operating frequency of each burner can always be kept the same. It is possible to prevent the generation of interference sound due to the frequency difference.

In this embodiment, the polarity-dependent control unit,
The input current detection unit, heating coil current detection unit, switching element voltage detection unit, ON time addition unit, OFF time addition unit, multiplication unit, etc. are shown in the block diagram, but the same applies when software processing is performed by microcomputer programming. is there.

Also, as for the inverter, two switching elements are used, but the same applies to three or more switching elements.

[0034]

As described above, according to the first aspect of the present invention, the ON / OFF frequency of the switching element is made different between one polarity of the commercial power source and the other polarity, and the same polarity is used depending on the input power. Since it can be controlled at a constant frequency without changing the operating frequency of the inverter section in the two polarities of the commercial power source, as a result, a difference occurs in the frequency of the noise radiated in both polarities, and they are superimposed at the same frequency. The level of radiation noise can be reduced by preventing the noise from occurring.
According to the invention described, by the polarity-dependent control unit that controls the on / off of the switching element so that the input current is constant in each polarity, even when driving the inverter by changing the operating frequency in both polarities, Since the input current can be controlled independently, stable input current control is possible.

According to the third aspect of the present invention, there is provided a heating coil current detector for detecting the current applied to the heating coil for each polarity of the commercial power supply, and the current applied to the heating coil is supplied to the polarity of the commercial power supply. Since it is possible to control each heating coil, it is possible to prevent one heating coil current from becoming excessively large, and highly reliable control is possible.

According to the fourth aspect of the present invention, there is provided a switching element voltage detector for detecting the voltage applied to the switching element for each polarity of the commercial power source, and the voltage applied to the switching element is for the polarity of the commercial power source. Since it is possible to control each switching element, it is possible to prevent one of the switching element voltages from becoming excessively high, and it is possible to perform highly reliable control.

According to the fifth aspect of the invention, the ON / OFF control of one polarity is performed by adding only a predetermined value for the ON time to the other control. The frequency of sex can be changed.

According to the sixth aspect of the present invention, the ON / OFF control of one polarity is simply performed by adding a predetermined constant OFF time to the other control. The frequency of sex can be changed.

According to the invention described in claim 7, since the ON / OFF control of one polarity is the other control only by multiplying the ON time and the OFF time by a predetermined constant ratio, a very simple structure. You can change the frequency of both polarities.

According to the eighth aspect of the present invention, in the induction heating cooker having a plurality of induction heating burners, when the frequency is changed according to the polarity change of the commercial power source, the changes are synchronized for all the burners. Even if multiple burners are provided with a difference in frequency between polarities, the operating frequency of each burner can always be kept the same, thus preventing the occurrence of interference noise due to the frequency difference. You can

[Brief description of drawings]

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

FIG. 2A is a voltage waveform diagram of a commercial power supply in the first embodiment of the present invention, FIG. 2B is an operation period diagram of the inverter unit, and FIG. 2C is a radiation noise level of a fundamental wave and a second wave. Figure

FIG. 3 is a block diagram of an induction heating cooker according to a second embodiment of the present invention.

FIG. 4 is a block diagram of an induction heating cooker according to a third embodiment of the present invention.

FIG. 5 is a block diagram of an induction heating cooker according to a fourth embodiment of the present invention.

FIG. 6 is a block diagram of an induction heating cooker according to a fifth embodiment of the present invention.

FIG. 7A is a voltage waveform diagram of a commercial power supply in a fifth embodiment of the present invention, FIG. 7B is a time chart of the ON time of the switching element 4b, and FIG. 7C is a time chart of the OFF time of the switching element 4b.

FIG. 8 is a block diagram of an induction heating cooker according to a sixth embodiment of the present invention.

9A is a voltage waveform diagram of a commercial power supply in a sixth embodiment of the present invention, FIG. 9B is a time chart of the ON time of the switching element 4b, and FIG. 9C is a time chart of the OFF time of the switching element 4b.

FIG. 10 is a block diagram of an induction heating cooker according to a seventh embodiment of the present invention.

FIG. 11A is a voltage waveform diagram of a commercial power supply in a seventh embodiment of the present invention, FIG. 11B is a time chart of the ON time of the switching element 4b, and FIG. 11C is a time chart of the OFF time of the switching element 4b.

FIG. 12 is a block diagram of a conventional induction heating cooker.

FIG. 13A is a switching element 4a in a conventional example.
Of the ON / OFF pattern of (b), the time chart of the ON / OFF pattern of the switching element 4b (c), the voltage waveform diagram of the commercial power supply (d), the operation cycle diagram of the inverter section

[Explanation of symbols]

1 Commercial power supply 2 rectifier circuit 3 heating coils 4a, 4b switching element 5 Inverter section 6 Polarity-based control unit 7 Input current detector 8 Heating coil current detector 9 Switching element voltage detector 10 Control unit 11 On-time adder 12 Off-time adder 13 Multiplier

Claims (8)

[Claims] 1. A commercial power source, a rectifying circuit for rectifying the commercial power source, a heating coil, two or more switching elements, and an inverter section for supplying a high-frequency current to the heating coil by turning on / off the switching elements. When,
The switching element is provided with a difference between one polarity and the other polarity of the commercial power source, the constant polarity is controlled at the same polarity, and the input power is substantially constant at each polarity. An induction heating cooker comprising a polarity-dependent control unit that controls on / off of elements. 2. A commercial power source, a rectifying circuit for rectifying the commercial power source, a heating coil, an input current detection unit for detecting an input current from the commercial power source for each polarity, and two or more switching elements. , An inverter section that supplies a high-frequency current to the heating coil by turning on and off the switching element, and an on-off frequency of the switching element is provided with a difference between one polarity and the other polarity of the commercial power source and the same polarity. In the above, the induction heating cooker is comprised of a polarity-dependent control unit that controls the switching element so that the input current is constant in each polarity so that the input current is constant. 3. A heating coil current detector for detecting the current applied to the heating coil for each polarity of the commercial power supply, and the heating coil current detected by the heating coil current detector does not exceed a predetermined value. 2. The induction heating according to claim 1, further comprising: a control unit for each polarity of the commercial power source, and a polarity-dependent control unit for controlling on / off of the switching element so that the heating coil current is constant in each polarity of the commercial power source. Cooking device. 4. A switching element voltage detecting section for detecting a voltage applied to the switching element for each polarity of a commercial power source, and a voltage detected by the switching element voltage detecting section so as not to exceed a predetermined value. The induction heating cooker according to claim 1, further comprising a polarity-dependent control unit that controls ON / OFF of the switching element for each polarity of the commercial power source and controls so that the switching element voltage is constant in each polarity of the commercial power source. 5. A commercial power source, a rectifying circuit for rectifying the commercial power source, a heating coil, two or more switching elements, and an inverter section for supplying a high-frequency current to the heating coil by turning on / off the switching elements. When,
An induction heating cooker provided with a control unit that controls the switching element at a constant frequency in one polarity and an on-time addition unit that adds an on-time of the other polarity by a predetermined value to the on-time of the one polarity. 6. A commercial power source, a rectifying circuit for rectifying the commercial power source, a heating coil, two or more switching elements, and an inverter section for supplying a high-frequency current to the heating coil by turning on / off the switching elements. When,
An induction heating cooker provided with a control unit that controls the switching element at a constant frequency in one polarity and an off-time addition unit that adds an off-time of the other polarity by a predetermined value to the off-time of the one polarity. 7. A commercial power source, a rectifying circuit for rectifying the commercial power source, a heating coil, two or more switching elements, and an inverter section for supplying a high-frequency current to the heating coil by turning on / off the switching elements. When,
A control unit that controls the switching element at a constant frequency in one polarity, and a multiplication unit that calculates the on time and the off time of the other polarity by multiplying the on time and the off time of the one polarity by a constant ratio. Induction heating cooker provided. 8. An induction heating cooker having a plurality of induction heating burners, wherein when the frequency is changed with the polarity change of the commercial power source, the change is synchronized for all burners. Or the induction heating cooker according to 6 or 7.