JP2009004099A - Induction heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress occurrence of interference sound, in an induction heating cooker having three induction heating openings. <P>SOLUTION: The induction heating cooker is provided with two heating coils 101, 201 arranged near the front surface of a main body, a heating coil 301 arranged on the back side between the above heating coils, and inverters 100, 200 and 300 supplying power to the heating coils. The inverters of the two heating coils arranged near the front surface of the main body carry out output control of the heating coils 101, 102 by making frequencies of conducting current variable. The inverter of the heating coil 301 arranged on the back side of the main body carries out output control of the heating coil 301 by making a frequency of conducting current fixed and on-off duty cycle variable. Thus, a frequency used for the heating coil 301 arranged on the back side is set higher than the highest frequency in a frequency band used for the heating coils arranged near the front surface. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an induction heating cooker.

  There has been proposed a heating cooker in which the stove provided at the center back of the main body is also an induction heating system, and all three stoves are induction heating systems (see, for example, Patent Document 1).

  The induction heating cooker itself generates heat by the eddy current generated by the high-frequency magnetic lines generated from the heating coil acting on the metal pan bottom as a load, and at the same time, the heating coil and the metal are heated by electromagnetic interaction. High-frequency vibration is generated due to the force acting between the pans. Since this high-frequency vibration is equal to the frequency of the current flowing through the heating coil, it is highly likely that the sound wave will be outside the audible frequency range and cannot be recognized by the user. However, when a plurality of induction heating type stoves are used at the same time, an interference sound (beat sound) is generated due to the frequency difference between the currents. When this component is present in the audible frequency range, the sound becomes recognizable to the user, and there is a problem that it feels harsh. In order to avoid such a state, the thing which makes the frequency of the electric current which flows into a some heating coil the same frequency is proposed. Specifically, there is a method of controlling the power by fixing the drive frequency of the inverter and changing the conduction ratio of the switching element (see, for example, Patent Document 2).

  Moreover, what makes the frequency difference of the electric current which flows into a some heating coil the high frequency outside an audible frequency range is proposed. Specifically, for example, there is a method of providing a difference of 20 kHz in the frequency of the current supplied to the two heating coils (for example, see Patent Document 3).

JP 2004-319350 A JP 2003-264056 A JP 2005-149737 A

  However, in the above prior art, in Patent Document 2, when the frequency of the current flowing through the plurality of heating coils is set to the same frequency, power control is performed at a fixed frequency in a half-bridge type or SEPP type inverter configuration. In this case, it is necessary to keep the switching element ON time of the upper and lower arms constant in total. In other words, the on / off duty ratio control per cycle is performed. However, since the energization ratio of the switching elements is biased, the loss generated in each element becomes unbalanced, the volume difference based on the shape of the heat sink, and the cooling There will be a difference in efficiency.

  Furthermore, since the resonance state varies depending on the load material and the load position, a cooling design with a margin must be performed. That is, it is necessary to increase the size of the switching element itself, increase the volume of the heat sink, increase the size of the cooling fan, and so on, which makes it difficult to reduce the size.

  In addition, since the resistance component that contributes to the heat generated by the metal load increases as the frequency of the current flowing through the heating coil increases, the heating efficiency generally increases. Since it is necessary to set the lowest frequency possible, there is a problem that the efficiency when low power is applied is lowered.

  Moreover, in the thing of patent document 3, when setting the frequency difference of the electric current which flows into a some heating coil out of an audible area, it is materialized when there are two heating coils, but in the case of three, it is 2 respectively. It is necessary to set so that the inverter drive frequency difference is outside the audible range in the combination of three and the combination of three.

For example, inverter 1: 20 kHz
Inverter 2: 40 kHz
Inverter 3: 60 kHz
When operating at each driving frequency, the difference in driving frequency between the inverters is 20 kHz. Therefore, even if an interference sound component of this frequency is generated, it is outside the audible frequency range and is not recognized as a sound by the user.

  However, if the drive frequency of the inverter is changed due to a change in the thermal power level, a change in the material of the load, or the like from such an operation state, the above condition is not satisfied.

For example, in the case where 20 kHz is provided as a range in which the inverter drive frequency is changed due to a change in the thermal power level of each inverter, a change in the material of the load, or the like, if each drive frequency difference is ensured to 20 kHz,
For example, inverter 1: 20 to 40 kHz
Inverter 2: 60-80kHz
Inverter 3: 100 to 120 kHz
This is the drive frequency range. However, there is a problem that the drive frequency range of the inverter cannot be realized because it exceeds the range (20 to 100 kHz) permitted in the induction heating cooker.

  In addition, in order to be able to heat with any material and shape load, it is necessary to cope with each driving frequency, so it is essential to switch the resonance constant over a wide range, switching the number of turns of the heating coil, Since a plurality of resonant capacitors must be mounted and their switching circuit is required, the circuit becomes very complicated and not realistic.

  The objective of this invention is providing the induction heating cooking appliance which solves the said subject and reduces generation | occurrence | production of an interference sound (beat sound).

  The object is to provide a plurality of induction heating coils arranged to heat each of the plurality of cooking pans, a plate for covering the plurality of induction heating coils and placing a cooking pan, and power to the plurality of induction heating coils. And a plurality of inverters that supply power controlled to have a predetermined frequency to any one of the induction heating coils, and the frequency is controlled to be variable. And an inverter for supplying electric power to any other induction heating coil.

  In addition, a plate on which a cooking pan is placed, a plurality of induction heating coils that generate eddy currents on the bottom of the cooking pan placed on the plate, and any induction of power with variable on / off duty ratio This is achieved by an induction heating cooker including an on / off duty ratio variable type inverter that is supplied to the heating coil and a frequency variable type inverter that supplies electric power with a variable driving frequency to the other induction heating coil.

  Furthermore, two induction heating coils arranged near the front surface of the main body, one induction heating coil arranged near the back of these induction heating coils, and a plate for covering the upper surface of these induction heating coils and placing a cooking pan In addition, in the induction heating cooker provided with an inverter for supplying electric power to these induction heating coils, the inverters of the two induction heating coils arranged near the front surface of the main body can vary the frequency of the energized current. In the induction heating coil, the inverter of one induction heating coil arranged at the back of the main body performs the output control of the induction heating coil by changing the on / off duty ratio of the current to be applied, The frequency used for the heating coil arranged at the back is higher than the highest frequency of the frequency band used for the heating coil arranged at the front side. Is achieved by the Ku set the induction heating cooker.

  Furthermore, two induction heating coils arranged near the front surface of the main body, one induction heating coil arranged near the back of these induction heating coils, and a plate for covering the upper surface of these induction heating coils and placing a cooking pan And an induction heating cooker provided with an inverter for supplying electric power to the induction heating coils, the two induction heating coil inverters arranged closer to the front surface of the main body are induction heated by making the drive frequency variable. The output of the coil is controlled, and the inverter of one induction heating coil arranged at the back of the main body controls the output of the induction heating coil by fixing the drive frequency and varying the on / off duty ratio, The frequency used for the heating coil arranged in the above is set higher than the highest frequency of the frequency band used for the heating coil arranged near the front surface. It is achieved by the induction heating cooker.

  Furthermore, two induction heating coils arranged near the front surface of the main body, one induction heating coil arranged near the back of these induction heating coils, and a plate for covering the upper surface of these induction heating coils and placing a cooking pan And a variable frequency inverter that changes the power supplied by changing the frequency of the current flowing in the resonance circuit provided with the induction heating coil disposed near the front surface of the main body, and the induction heating coil disposed near the back. A duty ratio variable inverter that changes power supplied by changing an on / off duty ratio of a current flowing in the resonance circuit, and the frequency of the current supplied to the heating coil arranged at the back is near the front surface. This is achieved by an induction heating cooker set higher than the highest frequency of the frequency band of the current supplied to the heating coil disposed in the.

  The induction heating cooker of the present invention can reduce the occurrence of interference sound (beat sound) generated by the frequency difference between the high-frequency currents flowing through the respective heating coils.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is an external perspective view of an induction cooking device showing an embodiment of the present invention. The induction heating cooker shown in FIG. 1 is a built-in induction heating cooker in which three pan mounting portions 6 a, 6 b, 6 c are provided on a plate 3. In addition, the present Example is not limited to the built-in type fitted into the system kitchen, but may be a stationary induction heating cooker placed on the kitchen.

  The main body 2 of the induction heating cooker is incorporated by being dropped from the upper surface of the system kitchen 1 and installed. After installation, a roaster (grill) 4 and an operation panel 5 (described later) of the main body 2 can be operated from the front portion of the system kitchen 1.

  The operation panel 5 is located on the front surface of the main body 2 and is a kangaroo type opening / closing mechanism. FIG. 1 shows a state in which the operation panel 5 is closed, and FIG. 2 shows an upper surface in a state in which the operation panel 5 is opened.

  A roaster 4 is disposed on the left side of the front surface of the main body 2. A handle 11 is attached to the front side of the roaster door 32 that closes the front opening of the roaster 4. The roaster 4 is for baking fish, pizza, and the like, and is not dedicated to grilling fish. Therefore, the roaster 4 may be called a grill or an oven. The roaster 4 may be arranged on the right side of the front surface of the main body 2 by replacing the operation panel 5.

  A cooking pan (not shown) for cooking is placed on a plate 3 made of heat-resistant glass or the like disposed on the upper surface of the main body 2. A cooking pan (not shown) can be cooked by being placed on the pan placement portions 6 a, 6 b, 6 c drawn on the plate 3. The pan mounting portions 6a, 6b, and 6c are a pan mounting portion 6a on the left side near the front surface of the main body 2 on the upper surface of the plate 3, and a pan mounting portion 6b on the right side near the front surface. A pan placing portion 6c is disposed on the side. And the heating coil (induction heating coil) 101, 201, 301 for heating a pan below each pan mounting part 6a, 6b, 6c on both sides of the plate 3 is installed. Details of the electric circuit around the heating coil will be described later with reference to FIG.

  The pan placing part 6 c is located on the back side of the main body 2. For this reason, when a hand was extended to the back pan mounting part 6c in the state where the pan was placed on the front pan mounting part 6a, 6b, the pan was placed on the front pan mounting part 6a, 6b. It is difficult to cook by moving the hand at the pot mounting portion 6c at the back due to steam generated during cooking from the pot. Therefore, the kind of cooking performed in the pot mounting portion 6c at the back is suitable for cooking that the cook does not need to move much, mainly cooking such as stew and heat insulation.

  In addition, since stew and heat retention require only a small heating power, and the maximum power consumption of the induction heating cooker is limited, the heating power (maximum output) of the heating coil 301 installed in the pot mounting portion 6c at the back is set to the front. It is set so as to be weaker than the heating power (maximum output) of the heating coils 101 and 201 installed corresponding to the pan mounting part 6a and the pot mounting part 6b, and to reduce power consumption.

  In addition, the magnitude | size of the induction heating cooking appliance main body 2 provided under the top plate 3 in a present Example is united with the opening dimension of the attachment hole provided in the countertop of the system kitchen 1 incorporating the main body 2. FIG. The opening dimensions are a width of 560 mm and a depth of 460 mm as defined in JIS, and the dimensions of the main body 2 excluding the front portion where the roaster 4 and the operation panel 5 are provided are adjusted to the opening dimensions.

  Therefore, the plate 3 has a width of about 600 mm and a depth of about 400 mm according to the opening size of the mounting hole. The heating coils 101 and 201 are arranged on the left and right sides near the front surface of the main body 2 within this range. A heating coil 301 is disposed at the center back.

  In FIG. 2, the display 97 indicates that the heating method for all three pot placement units 6a, 6b, and 6c is based on the induction heating method, and the center of the plate 3 or the pot placement unit 6a and the pot placement. By providing a display 97 in the vicinity of the straight line connecting the centers of the parts 6b, even if a cooking pan or the like is placed on the pan placing parts 6a, 6b, 6c, the display is not hidden, and the plate 3 is almost at the center. It can be easily seen that the three heating systems are the induction heating system by looking at the arranged display 97.

  1 and 2, a frame 14 is provided to protect the peripheral end surface of the plate 3. It consists of a frame front 14a attached to the upper upper edge of the front side of the plate 3, a frame rear 14b attached to the rear upper edge of the plate 3, a 14c attached to the right upper edge, and a frame left 14d attached to the left upper edge. ing.

  In this embodiment, the frame 14 is divided into four pieces, but the frame 14 can be an integral type, two pieces or any number of pieces, and it is not necessary to be attached to the four sides of the plate 3. Only two sides on the front and rear sides or only two sides on the left and right sides may be used.

  Inside the main body 2, heating coils 101, 201, 301, which are heat generating members, and electronic parts are provided, and an air inlet 7 for sucking air from the outside of the main body 2 is provided to cool these. . The intake port 7 is located on the right side of an exhaust port 8 (described later) on the rear frame 14 b on the upper surface of the main body 2. The air sucked through the air inlet 7 is on the side 14 b where the roaster 4 is provided on the rear surface 14 b of the upper surface of the main body 2 after cooling the heating coils 101, 201, 301 and electronic components that generate heat inside the main body 2. Is discharged to the outside through an exhaust port 8 provided at the outside. Further, air in the main body 2 warmed by the waste heat of the roaster 4 is also discharged from the exhaust port 8 at the same time.

  The operation of the heating coils 101, 201, 301 will be described. Operations such as energization of the heating coils 101, 201, 301 and setting of energization power are performed by the upper surface operation unit 9 provided on the front frame 14 a in front of the plate 3. This is done by key operation.

  Next, a display that reflects the result of the operation performed by the upper surface operation unit 9 will be described. The contents corresponding to the key operation of the upper surface operation unit 9 are displayed on the upper surface display unit 10 disposed on the near side of the plate 3 placed on the upper surface of the main body 2 and on the back side of the plate 3. The contents to be displayed are the display of the thermal power set by the upper surface operation unit 9, the time display for timer cooking, the display of the set oil temperature for fried food, and the like.

  FIG. 3 is a principal block diagram of the induction heating cooker. In FIG. 3, an AC power source 117 includes a first inverter 100, a second inverter 200, a third inverter 300, a heating coil 101, a heating coil 201, and a heating coil connected to each inverter 100, 200, 300. Power is supplied to 301. And the pan which is a load is arrange | positioned in the upper part vicinity of these heating coils 101,201,301, an eddy current is produced in a load by sending a high frequency current to each heating coil 101,201,301, and a pan is self-heated. .

  The first inverter 100 and the second inverter 200 employ a variable frequency control method in which the frequency of the output power is variable as the output control of the heating coils 101 and 201. For this reason, in this embodiment, the first or second inverter is also called a frequency variable inverter. The third inverter 300 employs a fixed frequency control method in which the frequency of the energized current is fixed and the on / off duty ratio is varied as output control of the heating coil 301. For this reason, in this embodiment, the third inverter is also called a fixed frequency inverter or an on / off duty ratio variable inverter. Here, fixing the frequency means controlling the frequency to be a predetermined frequency, and it goes without saying that there may be some fluctuation in the frequency.

  Each inverter 100, 200, 300 determines the power supplied to the load according to an instruction from the main control unit 118. Further, the inverter 100, 200, 300 feeds back the control state to the main control unit 118.

  The main control unit 118 is connected to the upper surface operation unit 9. When the user operates the upper surface operation unit 9, the main control unit 118 makes a request for setting the energization of the heating coils 101, 201, 301, the power supplied to the heating coils 101, 201, 301, etc. 9, the inverter 100, 200, 300 is instructed based on the information, or the input information is displayed on the upper surface display unit 10. The main control unit 118 also performs energization control (not shown) such as the roaster 4 other than the heating coils 101, 201, and 301.

  FIG. 4 is a block diagram of the frequency variable control type inverter 100. Note that the inverter 200 has the same configuration, and a description thereof will be omitted. In FIG. 4, the alternating current supplied from the alternating current power source 117 is converted into direct current by the rectifying means 102. The rectifying means 102 is connected to a switching unit constituted by a series body of switching elements 103 and 105. Switching elements 103 and 105 are connected to diodes 104 and 106 in antiparallel, respectively. A resonance circuit unit composed of the heating coil 101 and the resonance capacitor 107 is connected between the connection point of the switching elements 103 and 105 and the reference potential of the DC voltage converted by the rectifier 102. Snubber capacitors 108 and 109 are connected to the switching elements 103 and 105, respectively.

  The switching elements 103 and 105 are exclusively turned on and off at a high frequency, whereby a high-frequency resonance current is supplied to the resonance circuit unit configured by the heating coil 101 and the resonance capacitor 107, and a load arranged near the heating coil 101 is heated. Is done.

  The input current conversion unit 112 converts the output signal of the detection unit 111 that detects the AC current input from the AC power source 117 to an appropriate level and outputs the converted signal to the control unit 110. The input voltage detection means 113 detects the AC voltage of the AC power supply 117, converts it to an appropriate level, and outputs it to the control means 110. The inverter current detection means 115 outputs the current flowing in the resonance circuit section. The signal is converted to an appropriate level and output to the control unit 110.

  When the control unit 110 inputs a target power level instruction to be applied to the load from the main control unit 118, the control unit 110 sets the drive frequency of the switching elements 103 and 105 so that the output power of the inverter 100 becomes a target value. To control.

  The control unit 110 calculates the inverter power input to the load from the input from the input current conversion unit 112 and the input from the input voltage detection unit 113, and becomes a target to be applied to the load input from the main control unit 118. A signal for exclusive on / off control of the switching elements 103 and 105 is supplied to the level converter 116 so that the power level is input. The level converter 116 converts the drive level to an appropriate drive level and outputs an on / off signal to the switching elements 103 and 105. Further, the control unit 110 controls the power supplied to the load by changing the on / off frequency of the switching elements 103 and 105 via the level conversion unit 116. The control unit 110 outputs these control states to the main control unit 118.

  FIG. 5 is a schematic diagram showing the relationship between the drive frequency of the frequency variable type inverter 100 and the inverter power supplied to the load. Since the same applies to the inverter 200, the description thereof is omitted.

The load of the inverter 100 is composed of a combination of an equivalent inductance and an equivalent resistance composed of a heating coil 101 and a load such as a pan, and a resonance capacitor 107. The maximum power W _peak can be given when current flows at the resonance frequency f ₀ . When the switching elements 103 and 105 are driven at a frequency higher than this frequency, the inverter power applied to the load decreases as shown in FIG.

Actually, since the equivalent inductance and the equivalent resistance change depending on the material of the load (pan), the frequency f ₁ higher than the resonance frequency f ₀ is set as the minimum frequency of the variable frequency, and the load is rated at this minimum frequency f _1. The power W _max is given. Further, as the drive frequency is further increased, the inverter power is reduced, but since the cutoff current of the switching elements 103 and 105 is reduced, the loss of the switching elements 103 and 105 is increased. The heat generation of the 103 and 105 and the snubber capacitors 108 and 109 is increased. Therefore, in consideration of these losses, the maximum frequency f ₂ of the variable frequency is set on the high frequency side so that the minimum power W _min can be given to the load at the maximum frequency f ₂ . As described above, the relationship between the drive frequencies of the inverter 100 is f ₀ <f ₁ <f _2.
(For example, f ₀ = 18 kHz, f ₁ = 20 kHz, f ₂ = 40 kHz).

Note that the inverter power at f ₂ is the minimum power that the inverter 100 can continuously control, but when a lower power is applied to the load, a method using on / off duty control of energization of the inverter 100 is employed. You may do it.

In this way, the inverter 100 controls the power supplied to the heating coil 101 in the drive frequency range f _{1 to} f ₂ (range of ₂₀ kHz to 40 kHz).

  FIG. 6 is a block diagram of an inverter 300 that employs a fixed frequency control method. In FIG. 6, the rectifier 302 converts the alternating current supplied from the alternating current power source 117 into a direct voltage. A switching unit constituted by a series body of switching elements 303 and 305 is connected to the rectifying means 302.

  Switching elements 303 and 305 are connected to diodes 304 and 306 in antiparallel, respectively. A resonance circuit unit constituted by the heating coil 301 and the resonance capacitor 307 is connected between the connection point of the switching elements 303 and 305 and the reference potential of the DC voltage converted by the rectifier 302. Snubber capacitors 308 and 309 are connected to the switching elements 303 and 305, respectively. The resonant capacitor 307 is connected to the freewheeling diode 317 so that the anode is at the reference potential of the DC voltage and the cathode is at the connection point with the heating coil 301.

  The switching elements 303 and 305 are exclusively turned on and off at a high frequency, thereby supplying a high-frequency resonance current to the resonance circuit unit composed of the heating coil 301 and the resonance capacitor 307, so that a load arranged in the vicinity of the heating coil 301 is applied. Heated.

  The input current conversion unit 312 is connected to a detection unit 311 that detects an AC current supplied from the AC power source 117. The input current conversion unit 312 converts the output signal of the detection unit 311 to an appropriate level that matches the input of the control unit 310 and outputs the converted signal to the control unit 310. The input voltage detection means 313 detects the AC voltage supplied from the AC power supply 117, converts it to an appropriate level according to the input of the control means 310, and outputs it to the control means 310. The inverter current detection unit 315 converts the output signal from the detection unit 314 that detects the current flowing through the resonance circuit unit to a level appropriate for the input of the control unit 310 and outputs the converted signal to the control unit 310.

  When control unit 310 receives a target power level instruction to be applied to the load from main control unit 118, control unit 310 adds up ON time of switching element 303 and switching element 305 so that the output power of inverter 300 becomes a target value. Is fixed and the frequency is fixed, and the power supplied to the heating coil 301 is controlled by making the ratio of the ON time and the period (ON / OFF duty ratio) of the switching element 303 variable.

  The control unit 310 calculates the inverter power input to the load from the output from the input current conversion unit 312 and the output from the input voltage detection unit 313, and applies the target applied to the load input from the main control unit 118. A signal for exclusive on / off control of the switching elements 303 and 305 is converted to an appropriate drive level via the level conversion unit 316 and output to the switching elements 303 and 305 so that the power level becomes the same. By making the ON / OFF times of the switching elements 303 and 305 variable, the ratio of the ON time and period (ON / OFF duty ratio) of the switching element 303 is set to a desired ratio, and the power supplied to the heating coil 301 is controlled. The control unit 310 outputs these states to the main control unit 118.

  Next, detailed operation of the inverter 300 will be described. When the switching element 305 is turned on after the switching element 303 is turned off, a resonance current flows from the reference potential side of the DC voltage to the switching element 305 via the heating coil 301. When the voltage generated in the resonance capacitor 307 falls below the reference potential of the DC voltage, the current flows to the switching element 305 via the heating diode 301 via the freewheeling diode 317 connected in parallel with the resonance capacitor 307. Current continues to flow until the switching element 305 is turned off. When the switching element 305 is turned off and the switching element 303 is turned on again after a predetermined time has elapsed, a current can be passed through the heating coil 301 at a constant period.

  Since the inverter 300 is a fixed frequency control method, it is necessary to drive the inverter 300 at a frequency at which maximum power can be supplied to the load. In the frequency variable control method of FIG. 5, when a low power is applied to the load, it can be driven at a high frequency. In the fixed frequency control method, the frequency at which the maximum power is applied and the frequency at which the low power is applied are the same frequency. The equivalent resistance R (R∝√f, f: drive frequency) of the load is smaller than that of the variable frequency control method, and the heating efficiency of the load when low power is applied to the load is reduced. In addition, since the loss of the return diode 317 itself due to the current flowing through the return diode 317 occurs, the circuit loss of the inverter 300 is larger than that of the inverters 100 and 200. That is, it is desirable that the maximum power that inverter 300 can provide to the load be smaller than the maximum power that inverters 100 and 200 provide to the load. Therefore, it is desirable that the fixed frequency control type inverter 300 is disposed in the back with the maximum power smaller than the set maximum power of the variable frequency control type inverters 100 and 200.

FIG. 7 is a schematic diagram showing the relationship between the on / off duty ratio of the inverter 300 of the fixed frequency control method and the inverter power. The load of the inverter 300 is a combination of the equivalent inductance and equivalent resistance formed by the heating coil 301 and the pan, and the resonance capacitor 307. The drive frequency of the inverter 300 is the resonance frequency and the on / off duty ratio of the switching elements 303 and 305 is 50. %, The maximum power W _peak can be input. Actually, the driving is performed at a frequency slightly higher than the resonance frequency, and the switching element 303 at that time is set so that the rated power W _max can be input when the on / off duty ratio of the switching element 303 is less than 50%. When the resonance frequency is f ₃ and the drive frequency is f ₄ , the frequency relationship is f ₃ <f ₄
(For example, f ₃ = 55 kHz, f ₄ = 60 kHz).

FIG. 8 is a diagram showing the relationship between the drive frequency of inverters 100, 200, and 300 and inverter power. The inverter power of the heating coil 101 is denoted by W _L , the inverter power of the heating coil 201 is denoted by W _R , and the inverter power of the heating coil 301 is denoted by W _C. The resonance frequencies of the heating coils 101, 201, 301 are set to f _L0 , f _R0 , f _C0 , and the inverters 100, 200 when the maximum set power W _max (rated power) is supplied to the heating coils 101, 201, 301, respectively. , 300 are indicated by f _L1 , f _R1 , f _C1 , and the drive frequencies when the minimum set power W _min is supplied to the heating coils 101, 201, 301 are indicated by f _L2 , f _R2 , f _C2. Yes.

The inverter 300 is a fixed frequency control method, and f _C0 <f _C1 and f _C1 = f _C2 .

The inverters 100 and 200 of the heating coils 101 and 201 near the front surface of the main body 2 basically have the same component configuration, and show the same drive frequency-inverter power change if they have the same load (pan). Therefore, the resonance frequencies f _R0 and f _L0 and the maximum frequencies f _R2 and f _L2 that are the minimum set power W _min are the same frequency, but actually the resonance frequencies are different when the load is different.

Accordingly, FIG. 8 shows an example of a state where the equivalent inductance of the load of the left heating coil 101 near the front is slightly large, and the resonance frequency f _L0 is lower than f _R0 because the equivalent inductance is large. In either case, the maximum set power W _max (rated power) can be input at frequencies f _L1 and f _R1 higher than the resonance frequencies f _L0 and f _R0 .

  The drive frequency at which the rated power can be input varies depending on the load of different materials and shapes, and the position of the load on the heating coils 101 and 201. In any case, a frequency slightly higher than the resonance frequency is set to the lowest drive frequency. The frequency.

Thus, the drive frequencies of the inverters 100 and 200 are driven in a frequency band of, for example, f _{L1 to} f _R2 , and the drive frequency ranges of the inverters 100 and 200 of the heating coils 101 and 201 have a range that overlaps each other.

Further, even when the left and right heating coils 101 and 201 are heating a load of the same material shape, the driving frequency of the inverters 100 and 200 at that time differs if the set power is different. . In this case, if the drive frequency of the right heating coil 201 is f _R and the drive frequency of the left heating coil 101 is f _L , | f _R −f _L |
Interference noise (beating sound) component is generated (because the vibration components of the heating coils 101 and 201 and the load become sound). If this is in the audible range (approximately 20 Hz to 15 kHz), it may be recognized as a sound. If the amplitude of the interference sound component is large, that is, if the inverter power being input is large, the cook actually It becomes a recognizable sound.

  However, since the distance between the centers of the left and right heating coils 101 and 201 near the front surface is about 30 to 40 cm, they are separated as distances that interfere with each other. The interference sound based on the center-to-center distance has low sound pressure as a sound that can be actually recognized by the cooker, so that the sound during cooking (sound of boiling water, sound of fried food, sound of internal cooling fan, etc.) Often buried and not bothered.

  However, since the distance between the heating coils 101, 201 on the left and right sides near the front surface and the heating coil 301 on the back side is closer than the distance between the left and right heating coils 101, 201 (about 20 to 30 cm), there is an influence. Cheap.

Therefore, as shown in FIG. 8, the inverter driving frequency of the back heating coil 301 is shifted to a higher side, and the frequency f _C1 is higher than the highest frequencies f _R2 to f _L2 of the inverter driving frequencies of the front heating coils 101 and 201. And the number of turns of the heating coil 301 at the back is adjusted so that the resonance frequency f _C0 is also increased.

At this time, when the front side heating coils 101 and 201 are driven at the highest frequencies f _L2 and f _R2 , assuming that the driving frequency of the back heating coil 301 is f _C ,
| F ₂ −f _C |
Interference sound component is generated.

Since this interference sound component has a fixed driving frequency for the back heating coil 301, the frequency component of the frequency difference becomes a low frequency in the case of the combination having the highest driving frequency for the heating coils 101 and 201 near the front, which is harsh. Prone. The frequency difference Δf at this time is Δf = f _C1 −f ₂ (f ₂ : f _R2 or f _L2 )
It is. In this combination, the inverter power difference ΔW between the front heating coils 101 and 201 and the rear heating coil 301 is ΔW = W _cmax −W _min
It is.

  Here, the amplitude of the interference sound component generated by the drive frequencies having different frequencies is the interference sound component when the amplitude of each high-frequency vibration is small, that is, when the inverter power is small, or when the inverter power difference ΔW is large to some extent. As a result, the user is less likely to recognize the sound.

For example, if W _min = 0.3 kW and ΔW> 500 (W), there is little concern. The power difference ΔW that is difficult to recognize as a sound at this time varies depending on the distance between the front heating coils 101 and 201 and the rear heating coil 301, so that the power difference ΔW is changed depending on the arrangement of the heating coils 101, 201, and 301. If set, it is possible to prevent the interference sound from becoming a problem.

  As described above, the output control of the heating coil by the inverter of the two heating coils arranged near the front surface is performed by changing the frequency of the energized current, and the inverter of the one heating coil arranged near the back is used. The output control of the heating coil is performed by fixing the frequency of the energized current and varying the on / off duty ratio, and further, it is placed farther away than the highest frequency of the frequency band used for the heating coil placed near the front. By setting the frequency used for the heating coil high, it is possible to prevent the generated interference sound from becoming a problem.

Also, the difference ΔW between the minimum inverter power W _{min at} the maximum frequency in the driving frequency range of the front heating coils 101 and 201 and the maximum inverter power W _{cmax at} the frequency f _C1 of the back heating coil 301 is greater than or equal to a predetermined power difference. By setting so as to become, it is possible to prevent the generated interference sound from becoming even more problematic.

In addition, in the setting as described above, when the loads are close to each other and the difference between the driving frequencies is in the audible frequency region, the sound pressure may increase, which may be harsh. If it is set higher than 15 kHz so that Δf itself is out of the audible range, the interference sound can be prevented from becoming a problem. For example,
f ₂ = 40 (kHz)
When
f _C1 = 60 (kHz)
By setting to, the lowest interference component is Δf = | 60−40 | = 20 (kHz)
Therefore, Δf is outside the audible frequency region and basically cannot be recognized by the cooker in any combination of load and power.

  As already described, if the inverter driving frequency band of the front heating coils 101 and 201 and the inverter driving frequency of the back heating coil 301 are set so that there is no overlapping area, the same load (pan) is used. Therefore, the resonance frequency of the resonance circuit composed of the heating coil, the load, and the resonance capacitor is greatly different.

Here, the same load is used in all cases, and the inductance component of the resonance circuit is an equivalent inductance taking into account the coupling inductance between the inductance of the heating coil and the load. The equivalent inductance L and the resonance capacitor are used. The resonance frequency f is determined by the capacitance C. The definition of the resonance frequency f is f = 1 / (2π√ (L · C))
Therefore, in order to obtain a different resonance frequency f, it is only necessary to change the resonance capacitor capacitance C, but in actuality, the actual power loss (by the combination of the heating coils 101, 201, 301 and the load) The equivalent resistance that generates heat changes with the inverter drive frequency, and the value of the equivalent resistance increases in the high frequency range, making it difficult for current to flow. When the equivalent inductance L increases with the equivalent resistance, power is supplied to the load. It becomes impossible.

  Therefore, the number of turns of the back heating coil 301 is reduced as compared with the heating coils 101 and 201 disposed near the front surface at the same time as the drive frequency of the inverter 300 with respect to the back heating coil 301 is set high, and the inductance L of the heating coil 301 is reduced. Should be set lower.

  In this embodiment, the value of the equivalent inductance L of the heating coils 101 and 201 is 43 μH (20 kHz), the value of the equivalent resistance is 1.2Ω (20 kHz), and the value of the equivalent inductance L of the heating coil 301 is 21.2 μH (60 kHz). The equivalent resistance value was set to 1.2Ω (60 kHz).

  Thereby, even if the drive frequency of the inverter 300 with respect to the back heating coil 301 is set high (60 kHz), sufficient current flows, and sufficient power can be supplied to the load.

As described above, the frequency used for the heating coil 301 arranged at the back is set higher than the maximum frequency f _{2 of the} frequency band used for the heating coils 101 and 201 arranged near the front, and the front-side heating coils 101 and 201 are set. In comparison with the above, by reducing the inductance value of the back heating coil 301, it is possible to supply sufficient power to the load and reduce interference noise.

  Next, appropriate rated power distribution to the heating coils 101, 201, and 301 will be described. In actual cooking, the most frequently used heating coil is one of the two heating coils 101 and 201 located closer to the front surface for the user. This is because cooking operations (e.g., preheating the pot, adding food, stirring, etc.) are the easiest. These heating coils 101 and 201 are required to have a large heating power and to be able to change the heating power frequently.

  On the other hand, the heating coil 301 on the back side may be behind the load placed on the front side heating coils 101 and 201 and may not be easily cooked. Suitable for cooking without. That is, it is a cooking method that continues heating with relatively low power for a long time, such as stewed cooking.

  Therefore, the heating coil 301 arranged on the back side is sufficient even if the rated power is lower than that of the heating coils 101 and 201 on the front side. By setting as such, the heating coil 301 having a reduced number of turns. (If the heating coil 301 with a reduced number of turns is supplied with the same power as the front heating coils 101 and 201, it is necessary to pass a larger current, and the heating coil 301 itself) Loss will increase).

  As described above, the maximum power of the inverters 100 and 200 of the front heating coils 101 and 201 is set larger than the maximum power of the inverter 300 of the back heating coil 301. That is, by setting the maximum power of the inverter 300 of the back heating coil 301 to be lower than the maximum power of the inverters 100 and 200 of the front heating coils 101 and 201, the loss of the back heating coil 301 can be reduced. Therefore, it is not necessary to increase the size of the switching element itself, increase the volume of the heat sink, increase the size of the cooling fan, and the like, and the size can be reduced.

  Next, the positional relationship between the heating coils 101, 201, and 301 will be described. FIG. 9 is a schematic view of the installation surface shape of the heating coils 101, 201, 301 in the present embodiment. In an induction heating cooker having a plurality of heating coils of a built-in type that is dropped into the system kitchen 1 and a stationary type, generally in the depth direction with respect to the lateral length W facing the user. The length D is set short (for example, W = 60 cm, D = 40 cm).

  When three heating coils 101, 201, 301 are arranged, it is common to arrange them at the left and right sides near the front and the center near the back as shown in FIG.

  However, the positional relationship between the heating coils 101, 201, and 301 is wide between the left and right sides near the front surface, and the gap between the front side right and the back center and the front side left and the back center is narrow. This is to obtain the cooking space on the plate 3 most efficiently.

The center distance between each of the heating coils 101, 201, 301 is D _LR between the heating coil 101 and the heating coil 201, D _LC between the heating coil 101 and the heating coil 301, and D _RC between the heating coil 201 and the heating coil 301. Then D _LR > D _LC
D _LR > D _RC
Arrange so that In addition, since it will become difficult to suppress generation | occurrence | production of an interference sound if _DLR is shortened, it is better to keep away as much as possible.

  As already described, since the distance between the heating coils 101 and 201 on the left and right sides of the front surface is large by arranging in this way, even in the inverters 100 and 200 using the same frequency range, the interference sound is kept low. It is possible.

  At the same time, the distance between the front-side right heating coil 201 and the back center heating coil 301 and the distance between the front-side left heating coil 101 and the back center heating coil 301 are closer than the distance between the centers of the heating coil 101 and the heating coil 201, for example. However, since a configuration in which interference sound cannot be suppressed or recognized in this embodiment is adopted, no problem occurs.

  Therefore, as the arrangement of the heating coils 101, 201, 301, in the triangle formed by the center of each of the heating coils 101, 201, 301, the distance between the centers of the front heating side left heating coil 101 and the front side right heating coil 201 is It is set longer than the center distance of the heating coils 101, 201, 301 of the front side left heating coil 101 and the back center heating coil 301, and the front side right heating coil 201 and the back center heating coil 301, respectively.

  With such a configuration, it is possible to make a combination of heating units that are easy to use as induction heating cookers while suppressing components of interference sounds generated between the heating coils 101, 201, and 301.

  Accordingly, by setting the setting constants of the inverters 100, 200, and 300 and the positional relationship between the heating coils 101, 201, and 301 in this embodiment to values as shown in FIG. The generation of interference sound caused by the frequency difference between the high-frequency currents flowing through the 101, 201, and 301 can be reduced.

  By setting each set constant of each inverter 100, 200, 300 and the positional relationship between the heating coils 101, 201, 301 to values as shown in FIGS. 9 and 10, the respective heating coils 101, 201, 301 are provided. The generation of interference sound caused by the frequency difference between the high-frequency currents flowing through can be reduced.

  Thus, the variable frequency output control type inverters 100 and 200 having a frequency range that overlaps each other can change the power to be applied to the load by controlling the frequency, and the circuit configuration is relatively simple. Therefore, the operation suitable for the load impedance can be performed at low cost.

  By applying the induction heating cooker including the inverters 100 and 200 of such a control system to an induction heating cooker having three heating units (a stove), and using the configuration described in this embodiment. The generation of interference sound generated by the frequency difference between the high-frequency currents flowing through the respective heating coils 101, 201, 301 can be reduced.

  In addition, a fixed frequency control type inverter 300 is used for the heating coil 301 at the back, and although the loss is slightly increased as compared with the variable frequency output control method, the rated power is lowered corresponding to the cooking pattern of the user. By setting the optimum inductance of the heating coil, it is possible to suppress unbalanced heat generation of the switching element and increase loss due to reduced efficiency, thereby suppressing a decrease in heating efficiency, thus reducing the size and simplifying the cooling structure. Is possible.

  In addition, since the circuit configuration of the inverters 100 and 200 can be made relatively simple to reduce the generation of interference noise, a low-cost induction heating cooker can be provided.

It is an external appearance perspective view of the induction heating cooking appliance which shows one Example of this invention. It is explanatory drawing which shows the upper surface of an induction heating cooking appliance. It is a principal part block diagram of an induction heating cooking appliance. FIG. 4 is an internal block diagram of the frequency variable control type inverter of FIG. 3. It is a schematic diagram which shows the relationship between the drive frequency of the inverter of a frequency variable type control system, and the inverter electric power thrown into load. FIG. 4 is an internal block diagram of the fixed frequency control type inverter of FIG. 3. It is a schematic diagram which shows the relationship between the on-off duty ratio of the inverter of a frequency fixed control system, and inverter electric power. It is the figure which showed the relationship between the drive frequency of an inverter, and inverter electric power. It is the schematic of the installation surface shape of a heating coil. It is a figure explaining the setting constant example of the inverter and heating coil of this invention.

Explanation of symbols

2 Body 3 Plate 100, 200, 300 Inverter 101, 201, 301 Heating coil

Claims (15)

A plurality of induction heating coils arranged to heat each of the plurality of cooking pans, a plate for covering the plurality of induction heating coils and mounting the cooking pans, and a plurality of power supplies to the plurality of induction heating coils And an inverter
The plurality of inverters are:
An inverter that supplies power controlled to a predetermined frequency to any induction heating coil;
An induction heating cooker comprising: an inverter that supplies electric power controlled to be variable in frequency to any other induction heating coil. The induction heating cooker according to claim 1,
The inverter that supplies power controlled to have the predetermined frequency is a fixed frequency inverter,
The inverter that supplies electric power controlled to be variable in frequency is a frequency variable inverter,
The induction heating cooker characterized in that the drive frequency of the fixed frequency inverter is higher than the maximum frequency of the variable frequency inverter. In the induction heating cooker according to claim 1 or 2,
An induction heating cooker characterized in that a distance between the fixed frequency inverter and the variable frequency inverter is within 30 cm. A plate on which to put a cooking pot;
A plurality of induction heating coils for generating eddy currents in the cooking pan bottom placed on the plate;
An on / off duty ratio variable type inverter that supplies power with variable on / off duty ratio to any induction heating coil;
A variable frequency inverter that supplies power with variable driving frequency to other induction heating coils;
An induction heating cooker comprising: The induction heating cooker according to claim 4,
The induction heating cooker characterized in that the drive frequency of the on / off duty ratio variable type inverter is higher than the maximum frequency of the frequency variable type inverter. The induction heating cooker according to claim 4 or 5,
The induction heating cooker characterized in that a distance between the variable on-off duty ratio inverter and the variable frequency inverter is within 30 cm. Two induction heating coils arranged near the front surface of the main body, one induction heating coil arranged near the back of the induction heating coils, a plate for covering the upper surface of these induction heating coils and placing a cooking pan, In an induction heating cooker equipped with an inverter that supplies power to these induction heating coils,
The inverter of the two induction heating coils arranged near the front of the main body performs output control of the induction heating coil by changing the frequency of the current to be energized,
The inverter of one induction heating coil arranged at the back of the main body performs output control of the induction heating coil by varying the on / off duty ratio of the current to be energized,
The induction heating cooker which set the frequency used for the heating coil arrange | positioned near the said back higher than the highest frequency of the frequency band used for the heating coil arrange | positioned near the said front surface. Two induction heating coils arranged near the front surface of the main body, one induction heating coil arranged near the back of the induction heating coils, a plate for covering the upper surface of these induction heating coils and placing a cooking pan, In an induction heating cooker equipped with an inverter that supplies power to these induction heating coils,
The inverter of the two induction heating coils arranged near the front of the main body performs output control of the induction heating coil by making the drive frequency variable,
The inverter of one induction heating coil arranged at the back of the main body performs output control of the induction heating coil by fixing the drive frequency and varying the on / off duty ratio,
The induction heating cooker which set the frequency used for the heating coil arrange | positioned near the said back higher than the highest frequency of the frequency band used for the heating coil arrange | positioned near the said front surface.   8. The setting is made such that the difference between the power at the highest frequency in the frequency band used for the induction heating coil disposed near the front surface and the maximum power of the induction heating coil disposed near the back is a predetermined value or more. Or the induction heating cooking appliance of 8.   The induction heating cooker according to any one of claims 7 to 9, wherein a range of frequencies used for the induction heating coils arranged near the front surface is set to have a range overlapping each other.   11. The frequency according to claim 7, wherein a frequency used for the induction heating coil disposed closer to the back is set higher by 15 kHz or more than a maximum frequency of a frequency band used for the induction heating coil disposed closer to the front surface. Induction heating cooker.   The induction heating cooker according to any one of claims 7 to 11, wherein an inductance value of the induction heating coil arranged near the back is set lower than an inductance value of the induction heating coil arranged near the front surface.   The induction heating according to any one of claims 7 to 11, wherein the maximum power of the inverter of the induction heating coil arranged near the front surface is set larger than the maximum power of the inverter of the induction heating coil arranged near the back. Cooking device.   The distance between the center of the induction heating coil disposed near the front surface is closer to the front surface than the center of the induction heating coil disposed near the front surface and the center of the induction heating coil disposed near the back surface. The induction heating cooker according to any one of claims 7 to 13, wherein the induction heating coil is set to be longer than a distance between the centers of the induction heating coil and the induction heating coil arranged at the back.   Two induction heating coils arranged near the front surface of the main body, one induction heating coil arranged near the back of the induction heating coils, a plate for covering the upper surface of these induction heating coils and placing a cooking pan, A frequency variable inverter that changes power supplied by changing a frequency of a current flowing in a resonance circuit provided with an induction heating coil arranged near the front surface of the main body and an induction heating coil arranged near the back are provided. A duty ratio variable inverter that changes power supplied by changing the on / off duty ratio of the current flowing through the resonance circuit, and the frequency of the current supplied to the heating coil arranged at the back is arranged near the front surface Induction heating cooker set higher than the highest frequency of the frequency band of the current supplied to the heating coil.

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