JP2007184180A - Induction heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating cooker capable of restraining sound of a pot generated at the start of heating an object to be heated made of metal having low resistance. <P>SOLUTION: The induction heating cooker has a plurality of induction heating parts composed of a direct current output; an arm circuit electrically connected to both ends of the direct current output, composed of two switching elements turning on and off alternately; a resonance circuit formed by serially connecting a heating coil and a resonance capacitor; a control means connecting one end of the resonance circuit to a connection point of the arm circuit, and the other end to the direct current output, controlling heat amount of the object to be heated by driving the arm circuit with a constant frequency and by changing a conduction rate. The control means has a pot material judging function judging the material of the metal put on the heating coil. The pot material judging function drives the arm circuit and performs the above judgement by setting turn-on period of the switching element at one side to minimum value, and discretely changing turn-on period of the switching element at the other side from small value to large value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an induction heating cooker used for general household and business use.

  Conventionally, this type of induction heating cooker has a DC power source, a heating coil for heating a pan, and a first switching element connected in series, a resonance capacitor connected in series to the heating coil, and the first An inverter circuit including a second switching element connected in series with the switching element and a control unit thereof, the control unit including an oscillator, a variable conduction ratio setting unit, a conduction ratio detection unit, and an input detection unit; Having the two switching elements alternately conducted and the conduction ratio being variable, the conduction ratio detecting unit detecting the conduction ratio, and the output of the input detecting means and the output of the conduction ratio detecting unit Is detected as an inappropriate load (see, for example, Patent Document 1).

  FIG. 5 shows a conventional induction heating cooker described in Patent Document 1. As shown in FIG. As shown in FIG. 5, 41 is a DC output obtained by rectifying a commercial power supply, 42 is an inverter circuit, an arm circuit 43 including a first switching element 43a and a second switching element 43b connected in series, and an upper part thereof A heating coil 44a for placing a heated object 44f such as a pan on and a resonance circuit 44 in which a resonance capacitor 44b is connected in series, and both ends of the arm circuit 43 are connected to the DC output 41, The intermediate connection point of the arm circuit 43 is connected to one end of the resonance circuit 44, and the other end of the resonance circuit 44 is connected to one end of the DC output.

  Reference numeral 45 denotes a control means for driving the first switching element 43a and the second switching element 43b, and the first switching element 43a and the second switching element 45b are oscillated by an oscillator 45a that oscillates at a constant oscillation frequency and a variable conduction ratio setting unit 45b. The conduction time of the switching element 43b is set. Further, the control unit 45 includes a conduction ratio detection unit 45c that detects the conduction ratio set by the variable conduction ratio setting unit 45b, and an input detection unit 41c that detects an input current.

  The operation of the induction heating cooker configured as described above will be described below with reference to FIGS.

  In FIG. 5, the DC output 41 obtained by rectifying the commercial power supply is turned on and off alternately by the control means 45 by the first switching element 43 a and the second switching element 43 b that are constituent elements of the arm circuit 43, thereby returning to the resonance circuit 44. A high-frequency current is supplied to heat an object to be heated such as a pan placed on the heating coil 44a. At this time, the first switching element 43a and the second switching element 43b are alternately driven by the conduction time set by the variable conduction ratio setting unit 45b connected to the oscillator 45a that oscillates at a constant oscillation frequency. Further, when the variable conduction ratio setting unit 45b changes the conduction ratio, the conduction time of the first switching element 43a and the second switching element 43b changes with the constant frequency, and the input changes. FIG. 6 shows the relationship between the conduction ratio set by the variable conduction ratio setting unit 45b and the input current detected by the input detection means 41c when the type of the object to be heated is changed in the inverter circuit 42 that performs the above control. Show.

  As can be easily understood from FIG. 6, by taking the relationship between the conduction ratio and the input, it is possible to clearly distinguish a small object to be heated such as a knife from a heated object made of a nonmagnetic material such as stainless steel. . Therefore, by setting an appropriate load detection line as shown in FIG. 6, it is possible to easily determine whether the load is appropriate. The input from the input detection means 41c and the conduction ratio detected by the conduction ratio detection unit 45c are compared, and if it is above the appropriate load detection line, it is judged as an inappropriate load, and if it is below, it is judged as an appropriate load. If so, the control means 45 stops driving the arm circuit 43.

  As described above, the stainless steel load is detected as an appropriate load by comparing the output of the input detection means 41c and the output of the continuity ratio detection unit 45c, and a small load such as a knife is improperly loaded when the input is increased. It can be detected, and a large input does not enter the small load, which is excellent in safety.

  On the other hand, in the conventional configuration, the output of the oscillator 45a oscillating at a constant oscillation frequency is converted into the conduction time of the first switching element 43a and the conduction time of the second switching element 43b by the variable conduction ratio setting unit 45b. When the conduction time of the first switching element 43a is increased to increase the input current to the inverter circuit 42, the control means 45 drives the first switching element 43a with the minimum conduction time at the start of heating. When the operating frequency is constant, the current of the heating coil 44a is commutated while the second switching element 43b is conducting, and depending on the material of the object to be heated (load) placed on the heating coil 44a. There is a possibility that the current of the heating coil 44a becomes excessive.

As a result, an excessive current suddenly flows into the heating coil 44a at the start of heating, and the current is suddenly induced in the heated object such as a pan placed on the heating coil 44a to vibrate. It generated a sound like hitting a pot.
Japanese Patent No. 2532661

  However, in the conventional configuration, the first switching element 43a and the second switching element 43b are alternately arranged at the conduction ratio set by the variable conduction ratio setting unit 45b connected to the oscillator 45a that oscillates at a constant oscillation frequency. Further, the input to the inverter circuit 42 is changed by changing the conduction ratio. Therefore, it is possible to reduce the input as much as possible by setting the conduction ratio to the minimum set value.

  Here, when the conduction ratio is set to the minimum setting value, for example, the conduction time of the first switching element 43a is minimized, while the current waveform of each part when the conduction time of the second switching element 43b is maximized. Is shown in FIG.

  FIG. 7A shows a case where the object to be heated is made of an iron material, and FIG. 7B shows a case where the object to be heated is made of an aluminum material. The solid line represents the current voltage waveform of the first switching element 43a. The current of the heating coil 44a is indicated by a broken line. In FIG. 7A, the current of the heating coil 44a does not commutate and the amplitude is small, but in FIG. 7B, the current of the heating coil 44a commutates while the first switching element 43a is off, and the aluminum material is used. Since the resistivity is small, the coil current does not attenuate and the amplitude increases. The amplitude is larger in the heating coil 44a by about 6 times in the case of an aluminum material to be heated than in the case of an iron material to be heated. Therefore, since the eddy current generated in the object to be heated is also large in the aluminum material, the pan vibrates due to the repulsive force, and there is a problem that a sound like hitting is generated.

  In addition, when controlling the inverter having the circuit configuration of FIG. 5, the conduction ratio is fixed to about ½ in addition to the method of controlling the input by varying the conduction ratio by driving at a constant frequency as described in the conventional example. There is also a method of controlling the input by changing the frequency. However, in an induction heating cooker having a plurality of heating coils, there arises a problem that an interference sound is generated due to a shift in operating frequency that occurs when a plurality of burners are simultaneously heated.

  The present invention solves the above-described conventional problems, has a pan material discrimination function for discriminating the pan material at the start of heating, and sets the on time of one switching element to the minimum set value at the start of heating. By discriminating from a small set value to a large set value and driving the inverter circuit to make a discrimination, the operating frequency shift that occurs when multiple burners are heated simultaneously is made more than an audible frequency and interference noise is suppressed. And providing an induction heating cooker that performs control to suppress a pot sound that occurs when an object to be heated composed of a metal having a low resistivity such as an aluminum material is placed on a heating coil and starts heating. With the goal.

  In order to solve the above-described conventional problems, an induction heating cooker according to the present invention includes a DC output obtained by rectifying a commercial power supply and two switching units that are electrically connected to both ends of the DC output and alternately turned on and off. An arm circuit in which elements are connected in series; a resonance circuit in which a heating coil and a resonance capacitor are connected in series; one end of the resonance circuit is connected to a connection point of the arm circuit, and the other end is connected to a DC output; And a control means for controlling the amount of heating of the object to be heated by varying the conduction ratio and driving the constant current ratio, the control means comprising a plurality of induction heating sections, the control means of the metal mounted on the heating coil It has a pan material discriminating function for discriminating the material. At the start of heating, the pan material discriminating function discretes the on time of one switching element from the minimum set value to the large set value while the on time of one switching element is set to the minimum set value. Target Changes to one in which it was decided to perform the determination to drive the arm circuit.

  In the present invention, the control means drives the arm circuit at a constant frequency and varies the amount of heating of the object to be heated according to the conduction ratio, thereby preventing the generation of interference sound due to the deviation of the operating frequency with the adjacent induction heating unit.

  Furthermore, in order to prevent the pan noise generated at the start of heating, the on-time of one switching element is kept at the minimum set value at the start of heating, the other on-time is set to a small set value, and the heating amount of the object to be heated is determined by the conduction ratio. The arm circuit is driven at an operating frequency higher than the variable frequency.

  As a result, the current of the heating coil is commutated while the other switching element is turned on, and the state where the amplitude of the heating coil current becomes excessive depending on the material of the object to be heated is suppressed, and the other switching element is turned on. If it is determined that the material to be heated has an excessive current amplitude when the time is set to a large setting value, the heating is stopped.

  In addition, when it is determined that the material to be heated does not have an excessive current amplitude, the ON time of one switching element is kept at the minimum setting value, and the ON time of the other switching element is set to a large setting value, that is, Since it changes discretely to the operating frequency for controlling the amount of heating, it is possible to achieve control that avoids interference sound due to frequency shift and also reduces the pot noise at the start (heating start).

  The induction heating cooker of the present invention, for example, when a user places an object to be heated made of an aluminum material on a heating coil and starts heating, sounds such as hitting a pot called “Katsutsu”. This is advantageous in that it is possible to control the current flowing in the heating coil at a constant frequency by changing the conduction ratio of the arm circuit.

  According to a first aspect of the present invention, there is provided a direct current output obtained by rectifying a commercial power supply, an arm circuit in which two switching elements that are electrically connected to both ends of the direct current output and alternately turned on and off are connected in series, a heating coil, A resonance circuit in which a resonance capacitor is connected in series, one end of the resonance circuit is connected to a connection point of the arm circuit, and the other end is connected to a direct current output, and the arm circuit is driven at a constant frequency to change a conduction ratio to be covered. A plurality of induction heating units having control means for controlling the heating amount of the heated object, the control means having a pan material discrimination function for discriminating the material of the metal placed on the heating coil, The pan material discriminating function discriminates by driving the arm circuit by discretely changing the ON time of one switching element from the small setting value to the large setting value at the start of heating and setting the ON time of the other switching element to the minimum setting value. Do.

  As a result, the current of the heating coil is commutated while the other switching element is turned on, and depending on the material of the object to be heated, an excessive heating coil current amplitude is suppressed, and the other switching element is turned on. If it is determined that the material to be heated has an excessive current amplitude when the time is set to a large setting value, the heating can be stopped.

  Therefore, for example, when a user places an object to be heated made of an aluminum material on a heating coil and starts heating, the generation of a sound like hitting a pot called “Katsutsu” can be suppressed. In addition, when heating a highly heated object (load) such as stainless steel or iron material, a constant frequency current is supplied to the heating coil, and the heating amount of the object to be heated is determined by the continuity ratio of the arm circuit. Can be controlled.

  In the second invention, in particular, when the other switching element described in the first invention is discretely changed from a small set value to a large set value, the operating frequency and the on time of the set value having a small on time are set. Set so that the difference from the larger set value is greater than the variable frequency.

  Thereby, in the induction heating cooker having a plurality of induction heating units, when one side of the burner is being heated, even if the remaining burner starts heating at a high frequency as described in the first invention, the operation is performed. Since the frequency difference is set to be higher than the audible frequency, the generation of interference sound can be suppressed.

  According to a third aspect of the invention, the control means includes a power supply phase detection means for detecting the phase of the commercial power supply according to the first invention, and discretely changes the ON time of the switching element from a small set value to a large set value. When the commercial power supply is set to near zero volts, the operating frequency is changed at a timing when the heating coil current is small. Therefore, the pot generated when the frequency is changed discretely while suppressing the amount of current in the heating coil. Can suppress vibration.

  According to a fourth aspect of the invention, in particular, the control means according to the first aspect of the invention comprises coil current detection means for detecting the current of the heating coil, and the ON time of the switching element is discretely changed from a small set value to a large set value. After the change, if the current flowing through the heating coil is equal to or greater than the predetermined discriminating value for identifying the aluminum material, it is determined that the pan material discriminating function is erroneously discriminated, and the arm circuit drive is stopped, depending on the material to be heated. Even if an excessive resonance current is generated, the pot noise generated when heating is stopped can be suppressed by controlling the coil current when heating is stopped to be equal to or less than the set value.

  In particular, the fifth invention includes a series circuit of an auxiliary capacitor and a switch in parallel with the resonance circuit described in the first invention, and the control means is placed on the heating coil by the pan material discrimination function. If the metal material is determined to be non-magnetic, once the drive of the arm circuit is stopped, the control means closes the contact of the switch and connects the auxiliary capacitor to increase the capacity of the resonant capacitor. Even when a non-magnetic material to be heated is placed on the heating coil, the resonance frequency of the resonance circuit is lowered, preventing the current flowing through the heating coil from commutating and preventing an increase in coil current. It is possible to suppress an increase in the amount of current induced in the pan when heating is started and when heating is stopped, and to prevent the generation of pan noise.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited by the form of this invention.

(Embodiment 1)
FIG. 1 shows a circuit configuration of an induction heating cooker according to the first embodiment of the present invention.

  In FIG. 1, reference numeral 1 denotes a direct current output, which includes a 1a commercial power source and a 1b rectifier as components, and also includes an input detection means 1c for detecting a current output from the direct current output 1 and input to the inverter circuit 2. . The inverter circuit 2 includes an arm circuit 3 and a resonance circuit 4, and the arm circuit 3 includes a first switching element 3a and a second switching element 3b connected in series. Although not particularly shown in the figure, each of the first switching element 3a and the second switching element 3b includes a reverse conducting diode, and is configured to be capable of zero current switching. The resonance circuit 4 is configured by connecting a heating coil 4a and a resonance capacitor 4b in series on which an object to be heated 4f such as a pan is placed and cooked. Both ends of the arm circuit 3 are connected to the DC output 1, a connection point of two switching elements in the arm circuit 3 is connected to one end of the resonance circuit 4, and the other end of the resonance circuit 4 is connected to one end of the DC output 1. Connected.

  Further, the resonance circuit 4 has a series circuit of an auxiliary capacitor 4c and a switch 4d, and the series circuit is connected in parallel with the resonance capacitor 4b. The resonance circuit 4 includes a coil current detection unit 4e that detects whether an excessive current is flowing through the heating coil 4a.

  The control means 5 includes a first conduction time output 5a for driving the first switching element 3a in the inverter 2 and a second conduction time output 5b for driving the second switching element 3b. The conduction time output 5a and the second conduction time output 5b alternately output conduction time to supply a high-frequency current to the resonance circuit 4, and change the conduction ratio at a constant frequency to be placed on the heating coil 4a. The amount of heating of the heated object 4f is controlled.

  5c is a power supply phase detection means for detecting the phase of the commercial power supply 1a. The output time of the first conduction time output 5a and the second conduction time output 5b is determined when the output of the commercial power supply 1a is in a phase near zero volts. It has changed. 5d is a pan material discriminating function. In this embodiment, when the first conduction time output 5a outputs the minimum conduction time when the information of the coil current detection means 4e and the input visual inspection means 1c is obtained, To determine.

  The operation and action of the circuit configuration of the induction heating cooker configured as described above will be described below with reference to FIGS. 2, 3, and 4.

  First, in FIG. 1, the DC output 1 obtained by rectifying the commercial power source 1a is resonated by alternately turning on and off the first switching element 3a and the second switching element 3b which are constituent elements of the arm circuit 3 by the control means 5. A high frequency current is supplied to the circuit 4 to heat an object to be heated 4f such as a pan placed on the heating coil 4a. At this time, the first conduction time output 5a and the second conduction time output 5b operate at the same frequency, and after operating for a predetermined time at a high frequency (f1) only at the start of heating start, The frequency is changed to a predetermined frequency (f2) for controlling.

  Thereafter, the first conduction time output 5a and the second conduction time output 5b continue to be output at a constant frequency (f2), and the on-time of the first conduction time output 5a is increased to increase the second conduction time. By reducing the ON time of the output 5b, the conduction ratio is varied, and the heating amount to the heated object 4f is controlled.

  FIG. 2 shows how the first conduction time output 5a, the second conduction time output 5b, and the current of the heating coil 4a change during startup.

  The ON output of the first conduction time output 5a at the start of heating is the minimum output time (ta1) as described in FIG. 2A, and the second conduction time is output during the OFF period of the first conduction time output 5a. The output 5b outputs an on signal (tb1). At this time, the current flowing through the heating coil has a high resistivity if the object to be heated 4f is made of iron or non-magnetic stainless steel, so the amplitude of the current flowing through the heating coil 4a is small as shown in FIG. In the case of aluminum material, since the resistivity is small, the amplitude of the current flowing in the heating coil 4a is large as shown in FIG. 2 (a) and exceeds the set value, so that the pan material is discriminated as a low resistivity material such as aluminum material. It is possible to stop the heating operation as a pan not suitable for induction heating.

  Subsequently, the control means 5 detects the phase of the commercial power supply 1a by means of the power supply phase detection means 5c, and in this embodiment, when the fourth zero volt voltage phase comes, as shown in FIG. The ON time of the conduction time output 5b of 2 is increased from (tb1) to (tb2). At this time, as shown in FIG. 2 (b), the current flowing through the heating coil 4a is not commutated if it is an iron material, but if it is a nonmagnetic material such as nonmagnetic stainless steel, the second conduction time output (tb2) is To approach the resonance period. The current flowing through the heating coil 4a is commutated to increase the amplitude. However, since the resistivity is large, the current at the time of commutation is attenuated and does not reach a level where a pan sound is generated. However, in the case of an aluminum material with a low resistivity, the current of the heating coil 4a does not attenuate the current at the time of commutation as shown by the dotted line, and the second conduction time output (tb2) approaches the resonance period and the current becomes large. Therefore, a pot sound is generated.

  When the value is greater than the set value for non-magnetic discrimination, it is determined that the material is a non-magnetic material, and the first conduction time output 5a and the second conduction time output 5b are temporarily stopped, and the control means 5 switches the switch 4d. After turning on, the arm circuit 3 is again driven by the first conduction time output 5a and the second conduction time output 5b to start induction heating.

  If it exceeds the set value for aluminum discrimination, it is judged that the pan is not suitable for induction heating, heating is stopped, and it is not indicated in the figure that the pan is not suitable for induction heating. Inform the user using the means and the notification means.

  FIG. 3 shows a solid line for the current waveform of the heating coil 4a when the switch 4d is turned on and a broken line for the current of the heating coil 4a when the switch 4d is turned off when the material of the object to be heated 4f is nonmagnetic stainless steel. Is shown. When the switch 4d is off, the resonance period of the heating coil 4a and the resonant capacitor 4b is close to the second conduction time output (tb2) due to the influence of the non-magnetic material to be heated 4f. Current commutates and the current amplitude increases. However, when the switch 4d is turned on, the resonance capacitor 4b and the auxiliary capacitor 4c are connected in parallel, so that the resonance period becomes large, the current of the heating coil 4a becomes small amplitude without commutation, and the conduction ratio is variable with a constant frequency. Thus, the heating amount of the article to be heated 4f can be controlled.

  FIG. 4 shows judgment criteria when the pan material discrimination function 5d discriminates based on the outputs of the coil current detection means 4e and the input detection means 1c. At this time, the first conduction time output 5a outputs the minimum conduction time (ta1), and the area of FIG. 4A shows the minimum conduction time (tb1) at the frequency at which the second conduction time output 5b is high. The pan material discrimination area is shown, and the pan (heated material 4f) made of a non-magnetic material with low resistivity (for example, aluminum material) has a low input and a large coil current. Corresponds to the area shown by diagonal lines. When it is determined that the object to be heated 4f is a non-magnetic material such as an aluminum material and has a low resistivity (within the hatched area), the second conduction time output 5b is set to a minimum conduction time setting value at a low operating frequency ( Before changing to tb2), the heating operation is stopped to prevent the generation of pot sound. If it is determined that the material has a high resistivity, the second conduction time output 5b is continuously changed to the minimum conduction time setting value (tb2) at a low operating frequency, and FIG. ) To determine the pot material.

  The area of FIG. 4B shows a pan material discrimination area at the minimum conduction time (tb2) at a frequency where the second conduction time output 5b is low. In this case, in the present embodiment, the main distinction is made between the nonmagnetic material and the magnetic material. When it is determined that the material is a nonmagnetic material, the heating is temporarily stopped, the switch 4d is turned on, and then the first conduction is performed. The operation starts from the minimum time (ta1) of the time output 5a and the minimum time (tb2) of the second conduction time output 5b. In addition, even if it is a non-magnetic material, when it is determined that the material has a low resistivity, the heating is stopped and a display / notification indicating that it is not suitable for induction heating is performed. If the material is non-magnetic and has a high resistivity, by turning on the switch 4d, increasing the output time of the first conduction time output 5a and decreasing the output time of the second conduction time output 5b, It becomes possible to control the heating amount by varying the conduction ratio at a constant operating frequency.

  As described above, in the present embodiment, as described above, the first switching element 3a is driven with the minimum conduction time, and the heating amount is controlled for the conduction time of the second switching element 3b. When heating is started at a time (tb1) that is shorter than the conduction time (tb2) corresponding to the operating frequency used at the time, the current of the heating coil 4a is commutated even if the object to be heated 4f is a non-magnetic material. By setting the continuity time not to be used, the amount of current flowing through the heating coil 4a is suppressed, and the current induced in the object to be heated 4f is suppressed, so that a pot called “Katsutsu” generated at the start of heating is struck. The generation of sound can be prevented.

  Further, the operating frequency (f1) when the conduction time of the second switching element 3b is small (tb1) and the operating frequency (f2) when the conduction time of the second switching element 3b is large (tb2). Is set to be equal to or higher than the frequency (approximately 20 kHz) that is considered to be an audible region, so that the operating frequency is normally set to be constant (f2), and the heating amount is controlled at the start-up (when the conduction ratio is variable). When operating at a high frequency only (when heating is started), the interference sound is not heard by the user, and the current induced in the pan is also suppressed to prevent the sound of hitting the pan from occurring. Can do.

  The control means 5 includes a power supply phase detection means 5c, and changes the conduction time of the second switching element 3b from a small time (tb1) to a large time (tb2) near the phase where the commercial power supply 1a becomes zero volts. Thereby, since a frequency can be switched with a phase with little electric current which flows into the heating coil 4a, generation | occurrence | production of the pan sound accompanying the electric current change of the heating coil 4a can be prevented.

  Further, the control means 5 detects the current of the heating coil 4a by the coil current detection means 4e, and after the conduction time of the second switching element 3b is changed from the small time (tb1) to the large time (tb2), the heating coil When the current flowing through 4a is equal to or greater than the limit threshold value for generating a pan sound, the driving of the arm circuit 3 is stopped immediately, so that even if an excessive resonance current is generated due to the material of the article to be heated 4f, heating is performed. The pot sound can be suppressed by setting the coil current at the time of stopping to a predetermined value or less.

  Further, when the material of the object to be heated 4f is a non-magnetic material by the pan material discrimination function 5d, in the present embodiment, the coil current detection means 4e for detecting the current of the heating coil 4a and the input to the inverter circuit 2 It is determined based on the information from the input detection means 1c for detecting the current. If it is determined that the object is a non-magnetic material to be heated, the heating is once stopped, the switch is turned on, and then again. By adopting a configuration in which the heating ratio of the object to be heated 4f is fixed to a frequency for controlling the amount of heating and the conduction ratio is varied, the resonance circuit of the resonance circuit can be obtained even when a nonmagnetic material to be heated is placed on the heating coil. Resonance frequency is lowered and the current flowing in the heating coil can be prevented from commutating to prevent an increase in the coil current, thus suppressing an increase in the amount of current induced in the pan when heating starts and stops. And the generation of pot sound Gukoto can.

  In the first embodiment, a diagram is shown in which a transformer is used as a means for detecting the current of the heating coil 4a. However, since the current of the heating coil 4a corresponds to the voltage of the resonant capacitor 4b, It goes without saying that the same effect can be obtained by detecting the voltage.

  As described above, the induction heating cooker according to the present invention is a pot called “kotsutsu” when a user places an object to be heated made of aluminum material on a heating coil and starts heating. It is possible to control the current flowing in the heating coil at a constant frequency by changing the conduction ratio of the arm circuit, so that for example induction with multiple induction heating burners In a heating cooker, the present invention can also be applied to uses such as a control system for an induction heating cooker having a function of suppressing a pot sound generated at the start of heating or during heating.

The block diagram of the induction heating cooking appliance in the 1st Embodiment of this invention The figure which shows the operation | movement waveform of a switching element and a heating coil at the time of the heating start of this invention The figure which shows the operation waveform of each part at the time of a heating start at the time of discriminating the nonmagnetic pan of this invention The figure which shows the pan material discrimination | determination area at the time of the heating start of this invention Block diagram of a conventional induction heating cooker Diagram showing conventional aptitude load detection area The figure which shows the operation waveform of each part when the conventional to-be-heated material is aluminum material

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC output 1a Commercial power supply 1b Rectifier 1c Input detection means 2 Inverter circuit 3 Arm circuit 3a 1st switching element 3b 2nd switching element 4 Resonance circuit 4a Heating coil 4b Resonance capacitor 4c Auxiliary capacitor 4d Switch 4e Coil current detection means 4f Object to be heated (pan) (load)
5 Control means 5a First conduction time output 5b Second conduction time output 5c Power supply phase detection means 5d Pan material discrimination function

Claims (5)

A direct current output obtained by rectifying a commercial power supply, an arm circuit in which two switching elements that are electrically connected to both ends of the direct current output and alternately turned on and off are connected in series, a heating coil and a resonance capacitor are connected in series. Connect the resonant circuit and one end of the resonant circuit to the connection point of the arm circuit and the other end to a DC output, and drive the arm circuit at a constant frequency to vary the conduction ratio to control the heating amount of the object to be heated. A plurality of induction heating units having control means, the control means has a pan material discrimination function for discriminating the material of the metal placed on the heating coil, the pan material discrimination function, Induction heating cooking that discriminates by driving the arm circuit discretely by changing the ON time of one of the switching elements to the minimum set value and the other ON time from a small set value to a large set value at the start of heating. . When the ON time of one switching element is set to the minimum setting value and the other ON time is discretely changed from a small setting value to a large setting value, the control means has a large operating frequency with a small setting value. The induction heating cooker according to claim 1, wherein a difference between operating frequencies of set values is set to be equal to or higher than an audible frequency. The control means includes power supply phase detection means for detecting the phase of the commercial power supply, and the commercial power supply discretely changes the on-time of the switching element from a small set value to a large set value at a phase near zero volts. 2. The induction heating cooker according to 2. The control means is provided with a coil current detection means for detecting the current of the heating coil, and when the ON time of the switching element is discretely changed from a small set value to a large set value, and the current flowing through the heating coil is equal to or larger than the set value The induction heating cooker according to any one of claims 1 to 3, wherein the operation of the arm circuit is stopped by determining that the pan material determination function is erroneously determined. In parallel with the resonance circuit, a series circuit of an auxiliary capacitor and a switch is provided, and when the control means determines that the metal material placed on the heating coil is a non-magnetic material by the pan material discrimination function, the arm The induction heating cooker according to claim 1, wherein the driving of the circuit is temporarily stopped, the switch is turned on to change the resonance frequency of the resonance circuit, and then the arm circuit is driven again to start heating.