JP2009059605A - Induction heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating cooker preventing abnormal heating of small cooking ingredients, and conducting heating cooking by quickly returning to high heating power even in cooking shaking a pan like stir-fried food. <P>SOLUTION: The induction heating cooker has an inverter (5) converting input current into high-frequency current and supplying to a heating coil; a material detecting part (61) discriminating whether the material of a heating object is in a first region showing that the material should not heat or not by comparing the magnitude of the input current with that of the high-frequency current; and a control part (65) having a heating prevention function stopping the inverter when discrimination results of the material detecting part shows the material exists in the first region. The control part has a stopping delay function continuing operation without stopping the inverter when the detected value of the material detecting part enters the first region after a stopping delay condition at which the input current exceeds a prescribed value is satisfied. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an induction heating cooker that induction-heats a cooking container. In particular, the present invention relates to an induction heating cooker having a function of stopping heating when a non-heated object that is not a heating target, such as a knife or a spoon, is detected.

  2. Description of the Related Art In recent years, induction heating cookers that inductively heat a cooking container placed on a top plate by a heating coil disposed below the top plate have become widespread. The induction heating cooker preferably stops heating when a small object such as a spoon or fork is placed on the top plate or when an object to be heated is not placed on the top plate. Therefore, the conventional induction heating cooker detects whether the object to be heated placed on the top plate is a small object by detecting the input current of the inverter and the high-frequency current flowing through the heating coil. Whether or not is placed on the top plate. The induction heating cooker temporarily stops heating when it is determined that an object to be heated is not placed on the top plate or when it is determined that an accessory is placed. This control is referred to as an accessory heating prevention function (or “no-load detection function”). After the heating is temporarily stopped, after a predetermined time (for example, 3 seconds), the heating operation is started again, and the object to be heated is determined again. The operation of discriminating the object to be heated and the operation of temporarily stopping the heating are repeated for a predetermined time (for example, 30 seconds) from the start of the first heating, and the heating is completely stopped after the predetermined time has elapsed. In this way, the inverter is prevented from abnormally heating, and the inverter is prevented from operating in a state where the object to be heated is not placed.

When cooking with a pan like a stir fry, the pan temporarily leaves the top plate. When the pan moves away from the top plate, the induction heating cooker determines that there is no load and temporarily stops heating. Thereafter, reheating is not performed until a predetermined time (for example, 3 seconds) elapses. If the time from when the heating is temporarily stopped to when the heating is started again is long, the cooking container cannot be continuously heated in a high temperature state. Then, when the induction heating cooking appliance of patent document 1 detects having changed from the state (load state) in which the to-be-heated object is mounted in the top plate to the state (no load state) in which it is not mounted. Judges that cooking is in progress and shortens the pause time, thereby speeding up the thermal power recovery during reheating.
Japanese Patent Laid-Open No. 2-197070

  Patent Document 1 shortens the pause time when the load state changes to the no-load state, but does not continue heating. Therefore, there is a problem that the temperature of the cooking container is lowered because the heating power cannot be restored immediately.

  The present invention provides an induction heating cooker that prevents abnormal heating of small items and can quickly return to a high heating power and perform cooking even when a pan is cooked like a fried food.

  An induction heating cooker according to the present invention includes a top plate on which an object to be heated is placed, a heating coil that is disposed below the top plate and that heats the object to be heated, and an input current that is converted into a high-frequency current. Compare the magnitude of the input current and the magnitude of the high-frequency current with the inverter that supplies the high-frequency current to the inverter, and the comparison result is in the first region indicating that the material of the object to be heated is a material that should not be heated A material detection unit that determines whether the material is within a second region indicating that the material may be heated, and determines the type or shape of the material forming the object to be heated based on the comparison result The control unit has a heating prevention function for stopping the inverter when the determination result of the material detection unit is within the first region, and controls the output of the inverter based on the determination result of the material detection unit. And the When the control unit indicates that the input current exceeds a predetermined value as a stop delay condition and the stop delay condition is satisfied, the determination result of the material detection unit indicates that it has entered the first region. It has a stop delay function that continues the operation without stopping the inverter.

  Here, the “first area” refers to the “small area 23” in FIG. 3, and the “second area” refers to all areas except the small area 23. The kind of material forming the object to be heated means iron, stainless steel, aluminum or the like.

  The inverter may include a switching element for controlling the amount of high-frequency current supplied to the heating coil. In this case, when the conduction time of the switching element is lengthened, the supply amount of the high-frequency current increases, and when the conduction time of the switching element is shortened, the supply amount of the high-frequency current decreases. The control unit preferably makes the conduction time of the switching element when operating the inverter by the stop delay function shorter than the conduction time of the switching element when operating the inverter in the second region.

  The material detection unit may provide a third region around the outside of the first region in the second region, and determine whether the comparison result is in the third region. In this case, when the operation of the inverter is continued by the stop delay function, the control unit sets the switching element under a predetermined driving condition so that the input current is smaller than that before continuing the operation of the inverter by the stop delay function. If the determination result of the material detection unit returns outside the first region and the third region before a predetermined period of time has elapsed since the stop delay function is operated, the stop delay function is canceled and the inverter is released. Is preferably gradually increased to the set value.

  Here, the “third region” corresponds to the “panning area 24” in FIG.

  The induction heating cooker further includes a temperature detection unit (8) that detects the temperature of the object to be heated, and the control unit stops the temperature of the object to be heated detected by the temperature detection unit from exceeding a predetermined temperature. It may be added to the delay condition.

  The said control part may integrate | accumulate the electric power input into an inverter after starting heating, and may add that the integrated electric power exceeds predetermined amount to stop delay conditions.

  The control unit stops the inverter when the determination result of the material detection unit indicates that it is within the first region for a predetermined period after entering the first region from the second region. Also good.

  The material detection unit may provide a third region around the outside of the first region in the second region, and determine whether the comparison result is in the third region. In this case, if the determination result of the material detection unit indicates that the material detection unit is in the fourth region after entering the first region from the second region, the control unit operates the inverter by the stop delay function. You may continue.

When the control unit indicates that the determination result of the material detection unit is within the first region or the third region for a predetermined period after entering the first region from the second region, The inverter may be stopped.

  After the inverter is operated by the stop delay function, the controller controls the increase rate of the conduction time of the switching element when the operation of the inverter by the stop delay function is canceled and increased to the set value. You may make larger than the increase rate of the conduction time of the switching element before making it operate | move.

  The induction heating cooker further includes a storage unit, and the control unit stores, in the storage unit, the material type of the object to be heated, which is determined by the material detection unit, before the stop delay condition is satisfied. If the material type of the object to be heated determined by the material detection unit is different from the material type stored in the storage unit while the operation of the inverter is continued, the inverter may be stopped.

  The induction heating cooker further includes a temperature detection unit that detects the temperature of the object to be heated, and the control unit detects when the temperature detected by the temperature detection unit after stopping the inverter exceeds a predetermined temperature. The stop time may be set to be shorter than the stop time when the predetermined temperature is not exceeded, and the inverter may be operated again after the stop time has elapsed.

  The induction heating cooker further includes a temperature detection unit that detects the temperature of the object to be heated, and the control unit has an overtemperature prevention function that stops the operation of the inverter when the temperature of the object to be heated exceeds a predetermined temperature. You may prepare. In this case, it is preferable to stop the inverter when the overheat prevention function is activated while the operation of the inverter is continued by the stop delay function.

  The induction heating cooker further includes an overcurrent detection unit that detects whether or not an overcurrent flows through the inverter based on the value of the high-frequency current, and the control unit detects that the overcurrent detection unit is overcurrentd in the inverter. When it is detected that the current flows, an overcurrent prevention function for stopping the operation of the inverter may be provided. In this case, it is preferable to stop the inverter when the overcurrent prevention function is activated while the operation of the inverter is continued by the stop delay function.

  The control unit may increase the detection sensitivity of the overcurrent detection unit while continuing the operation of the inverter by the stop delay function as compared with the case where the operation of the inverter is not continued by the stop delay function.

  The induction heating cooker may further include a switch for allowing the user to determine whether or not to operate the stop delay function.

  According to the present invention, abnormal heating of small items can be prevented, and even when a pan is cooked like a stir-fry, it can be immediately restored to a high heating power for cooking.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1. 1. Configuration of induction heating cooker FIG. 1 shows the configuration of an induction heating cooker according to an embodiment of the present invention. The induction heating cooker of this embodiment includes a power switch 2 that switches on / off of a power source and a rectifier circuit 4 that converts AC power into DC power. When the power switch 2 is on, AC power is supplied from the AC power source 1 as input power.

  The induction heating cooker further includes a choke coil 51 and a smoothing capacitor C1. One end of the choke coil 51 is connected to the high potential side of the rectifier circuit 4. The smoothing capacitor C <b> 1 is connected between the other end of the choke coil 51 and the low potential side of the rectifier circuit 4.

  The induction heating cooker is supplied with DC power from the rectifier circuit 4 to input an inverter 5 for heating the cooking container 10 such as a pan, a control means 6 for controlling the inverter 5, and an instruction from the user. And an operation unit 7 for the purpose. The control means 6 controls the inverter 5 according to an instruction from the user.

  The inverter 5 includes a first switching element 53, a second switching element 54, a heating coil 55, and a resonance capacitor C2. The first switching element 53 and the second switching element 54 connected in series are connected in parallel with the smoothing capacitor C1. In addition, the first switching element 53 and the second switching element 54 are respectively connected in parallel with diodes in opposite directions (a state in which the high potential side of the switching element and the cathode side of the diode are connected). Yes. The heating coil 55 and the resonance capacitor C <b> 2 connected in series are connected in parallel with the second switching element 54.

  When the first switching element 53 and the second switching element 54 are turned on / off, a high-frequency coil current IL is supplied to the heating coil 55. Specifically, when the conduction time of the first switching element 53 is increased, the supply amount of the coil current IL is increased, and when the conduction time of the first switching element 53 is shortened, the supply amount of the coil current IL is decreased. When the coil current IL is supplied, the heating coil 55 generates an induction magnetic field, and induction-heats the cooking vessel 10 placed on the top plate 9. The heating coil 55 is provided below the top plate 9.

  The induction heating cooker has an input current detection element 3 and a coil current detection element 52 in order to detect a current value. The input current detection element 3 is connected between the power switch 2 and the input terminal of the rectifier circuit 4 and detects the value of the input current Iin. In the case of FIG. 1, the coil current detection element 52 is a current transformer and is connected in series with the resonance capacitor C2 to detect the value of the coil current IL. The coil current detection element 52 only needs to be able to detect a current value or a voltage value correlated with the coil current IL, such as measuring the coil current IL by measuring the voltage Vc across the resonance capacitor C2, for example. The measuring means is not limited.

  The control means 6 includes a material detection unit 61 that detects a load state, a storage unit 63, an overcurrent detection unit 62 that detects an overcurrent flowing through the inverter 5, a temperature detection unit 64 that calculates the temperature of the cooking vessel 10, and an inverter. 5 has a control unit 65 for controlling the driving of 5.

  The material detection unit 61 detects the value of the input current Iin from the input current detection element 3 and detects the value of the coil current IL from the coil current detection element 52. The material detection unit 61 determines the type or shape of the material forming the load based on these detection values. The discrimination result of the material detection unit 61 is output to the control unit 65.

  Specifically, the material detection unit 61 detects and compares the magnitude of the input current Iin and the magnitude of the coil current IL, and based on the comparison result, whether the load is placed on the top plate 9. Somehow, the type and shape of the material forming the load placed on the top plate 9 are detected. That is, it detects whether there is no load, an aluminum pan, a magnetic pan, or a non-magnetic pan. The detected pot type 631 is stored in the storage unit 63 via the control unit 65.

  Further, the material detector 61 sets the accessory area 23 based on the determination result of the load material, and the value of the input current Iin and the value of the coil current IL are within the accessory area 23 (see FIG. 3A). It is determined whether or not. Furthermore, the material detection unit 61 determines whether the load is in the pan swing area 25 (see FIG. 3A) based on the value of the input current Iin and the value of the coil current IL. Further, the material detection unit 61 outputs to the control unit 35 whether or not the value of the input current Iin exceeds a set value Io for operating the stop delay function 652.

  The overcurrent detection unit 62 detects the value of the coil current IL from the coil current detection element 52, and an overcurrent flows through the first switching element 53 or the second switching element 54 as compared with a predetermined detection level. Determine whether or not. The overcurrent detection unit 62 outputs the determined result to the control unit 65.

  Although the overcurrent detection unit 62 and the material detection unit 61 detect the value of the coil current IL, the detected value is not limited to the coil current IL as long as the value has a correlation with the coil current IL. For example, the current ISW1 flowing through the first switching element 53, the current ISW2 flowing through the second switching element 65, the current flowing through the smoothing capacitor C1, or the voltage Vc applied to the resonant capacitor C2 may be detected.

  The temperature detection unit 64 detects the temperature of the cooking container 10 based on the output value of the temperature detection element 8. The temperature detection element 8 is a thermistor or an infrared sensor.

  The control unit 65 functions based on the output of the material detection unit 61, the overcurrent detection unit 62, or the temperature detection unit 64. The accessory heating prevention function 651, the stop delay function 652, the overtemperature prevention function 653, and the overcurrent A prevention function 654;

  The accessory heating prevention function 651 is a function for preventing the accessory such as a spoon or fork or the aluminum pan from being heated. The accessory heating prevention function 651 stops the inverter 5 when the detected value of the material detection unit 61 indicates that it is in the accessory area.

  The stop delay function 652 is a function for improving usability in cooking while shaking a pan, which is often performed when cooking a fried food or the like. When the control unit 65 detects that the pan is being shaken based on the output of the material detection unit 61 by using the stop delay function 652, the control unit 65 disables the accessory heating prevention function 651 for a predetermined period.

  The over-temperature prevention function 653 is a function for preventing oil ignition. The over-temperature prevention function 653 stops the inverter 5 when the temperature detected by the temperature detector 64 is higher than a predetermined temperature.

  The overcurrent prevention function 654 is a function for preventing the first and second switching elements 53 and 54 from being destroyed by overcurrent. The overcurrent prevention function 654 stops the inverter 5 when the overcurrent detection unit 62 detects that an overcurrent flows in the inverter 5.

  Based on these functions 651 to 654, the control unit 65 controls the conduction time of the first switching element 53 and the second switching element 54 of the inverter 5 and the increasing rate of the conduction time. When the heating is stopped, the first switching element 53 and the second switching element 54 are turned off. During the heating, the first switching element 53 and the second switching element 54 are alternately turned on / off. When heating power is increased during heating, the conduction time Ton of the first switching element 53 is increased. That is, when operating the inverter 5 at a constant frequency, the conduction time Ton of the first switching element 53 is increased, the conduction time of the second switching element 54 is decreased, the drive time ratio is changed, and the operating frequency is changed. When changing, the conduction time of the first and second switching elements 54 is increased simultaneously.

  The operation unit 7 includes an input unit 71 for a user to input a command relating to heating start / stop and heating power, a heating setting unit 72 for performing heating setting based on the command input to the input unit 71, and a setting And a display unit 73 that displays the state thus displayed to the user. The heating setting set by the operation unit 7 is transmitted to the control unit 65. Further, the input unit 71 includes a switch 711 for controlling whether or not the user permits the operation by the stop delay function 652. For example, the user may turn on the switch 711 to permit the operation of the stop delay function 652 when frying, and otherwise turn off the switch 711 to prohibit the operation of the stop delay function 652. it can.

2. Characteristics of pan material FIG. 2 shows the characteristics of coil current IL / input current Iin of no-load, aluminum pan, magnetic pan, and non-magnetic pan. An input current Iin on the horizontal axis in FIG. 2 is a current input to the inverter 5. An aluminum pan is a pan made of aluminum, a nonmagnetic pan is a pan made of a nonmagnetic material other than aluminum (for example, stainless steel), and a magnetic pan is a pan made of a magnetic material such as iron. That is. 2A to 2D indicate the characteristic values of the coil current IL / input current Iin of the no load, the magnetic pan, the non-magnetic pan, and the aluminum pan when the conduction time of the first switching element 53 is minimized. Each is shown. Moreover, the arrow with respect to 2B-2D from 2A has shown the transition when the state on the top plate 9 changes from a no-load to a magnetic pan, a nonmagnetic pan, or an aluminum pan while shaking the pan.

  The magnetic pan has a characteristic that the coil current IL is smaller than the input current Iin. The nonmagnetic pan has a characteristic that both the input current Iin and the coil current IL are large. The aluminum pan has a characteristic that the coil current IL is very large even when the input current Iin is small. Thus, the characteristics of the coil current IL / input current Iin differ depending on the type of pan. Therefore, during heating, the conduction time Ton of the first switching element is increased at an increase rate according to the characteristics of the pan.

  In the case of an aluminum pan, since a large amount of coil current IL flows even with a small input current Iin, the first switching element 53 may be destroyed. Therefore, when the aluminum pan is placed on the top plate 9, the inverter 5 is stopped or the inverter 5 is operated in a heating mode dedicated to the aluminum pan. In the following embodiment, the inverter 5 is stopped when the aluminum pan is used.

3. Fig. 3 (a) shows the path Vc (coil current IL) / input current Iin of the resonant capacitor during panning and the resonance capacitor C2 when panning and the voltage Vc / input of the resonant capacitor C2 during panning. The locus of current Iin is shown. FIG. 3B shows the positional relationship between the cooking container 10 and the heating coil 55 when the pan is shaken.

  3A, the horizontal axis represents the input current Iin corresponding to the AC power input from the AC power 1, and the vertical axis represents the resonant capacitor proportional to the magnitude of the high-frequency current supplied to the heating coil 55. This is a voltage value Vc applied to both ends of C2. The inside of the boundary line 21 or 22 (the side where the voltage Vc of the resonance capacitor C2 is larger than the input current Iin) is the accessory area 23. The accessory area 23 is determined by the material detector 61 that an accessory such as a spoon or fork is placed on the top plate 9 based on the input current Iin and the coil current IL (voltage Vc of the resonance capacitor C2). It is an area. Specifically, the boundary line 21 is a discrimination criterion set when the magnetic pan is used, and the boundary line 22 is a non-magnetic pan. The material detection unit 61 sets the inside of the boundary line 21 as the accessory area 23 when it is determined that the cooking container 10 is a magnetic pan, and the boundary line 22 when it is determined that the cooking container 10 is a non-magnetic pan. Is set as the accessory area 23.

  When the input power Iin is supplied to the inverter 5 with the small article placed on the top plate 9, the voltage Vc of the resonance capacitor C 2 rapidly rises and enters the small article area 23 as shown by the characteristic 26. When the cooking container 10 is not loaded or when the cooking container 10 is an aluminum pan, the start position (2A, 2D) and the inclination of the increase are slightly different from the small items as shown in FIG. No. 5 operates as a locus on a curve similar to the characteristic 26 of the accessory. On the outside of the accessory area 23, the inside of the boundary line 24 is a pan swing area 25. The pot shake area 25 is set by the material detection unit 61. The setting in the pot swing area 25 (see FIG. 3A) may be performed when the value of the input current Iin and the value of the coil current IL enter the accessory area 23 from the outside of the accessory area 23.

  Trajectories A to E in FIG. 3A indicate the characteristics of the voltage Vc / input current Iin of the resonant capacitor C2 when the cooking container 10 is a magnetic pan. Symbols A to E shown in FIGS. 3A and 3B correspond to each other. When the cooking container 10 is placed directly above the heating coil 55 via the top plate 9 (A, B), the conduction time of the switching element 53 is minimum at the heating start point (A), and the resonant capacitor The value of the voltage Vc of C2 is small. The input current Iin and the voltage Vc of the resonant capacitor C2 increase by the soft start operation until the input current Iin reaches the target value I2 set by the heating setting unit 72 (B). The soft start operation is performed by gradually increasing the conduction time of the first switching element 53 (A → B).

  When the cooking vessel 10 starts to shift from a position directly above the heating coil 55, the voltage Vc of the resonance capacitor C2 increases (B → C). The induction heating cooker is usually provided with a limiter that limits the value of the voltage Vc of the resonance capacitor C2. When the voltage Vc of the resonance capacitor C2 reaches a value set by the limiter, the voltage Vc of the resonance capacitor C2 is reached. Is constant, the conduction time of the first switching element 53 decreases, and the input current Iin decreases (C → D). Further, when the cooking container 10 is displaced, it enters the accessory area 23, the conduction time of the first switching element 53 is set to the minimum value, and the voltage Vc of the resonant capacitor C2 decreases together with the input current Vc (D → E).

  From the unloaded state E in which the cooking container 10 is completely removed from the heating coil 55, the cooking container 10 is placed on the heating coil 55 again to be in the state A outside the accessory area 23 and the pan swing area 25. In the meantime, the voltage Vc of the resonant capacitor C2 decreases and the input current Iin increases (E → A). After entering the accessory area 23, when the conduction time of the first switching element 53 is set to the minimum value, the soft start operation is started again when it goes out of the pan swing area 25 within a predetermined time (for example, 2 seconds). The The input current Iin and the voltage Vc of the resonant capacitor increase by the soft start operation until the input current target value I2 set by the heating setting unit 72 is reached (A → B).

  As shown in FIG. 3A, when cooking is performed while the cooking container 10 is moved, when the cooking container 10 is displaced from just above the heating coil 55 (C → D → E), the voltage Vc of the resonance capacitor C2 The value of the input current Iin enters the accessory area 23. At this time, if the accessory heating prevention function 651 is activated and the control unit 65 temporarily stops heating, the cooking container 10 immediately returns to high heating power when the cooking container 10 returns to the position immediately above the heating coil 55. I can't cook. Therefore, the stop delay function 652 of the present embodiment prevents the accessory heating prevention function 651 from working when the cooking container 10 is moving. In the present embodiment, the condition for operating the stop delay function 652 is that the input current Iin once exceeds the set value Io. The set value Io is set to a value that the accessory characteristic 26 does not exceed.

4). Heating control FIG. 4 shows a flow from the start of heating to the progress of the accessory determination A or the pot swing determination B. When the user turns on the power switch 2 and is instructed to start heating via the input unit 71, the control unit 65 minimizes the conduction time Ton of the first switching element 53 (Min.), Heating is started (S401). That is, heating is started in a state where the output of the inverter 5 that can be varied by the conduction time of the first switching element 53 is minimum. After the start of heating (for example, after 5 μs), the material detection unit 61 determines the type or shape of the material of the cooking container (pot) 10 based on the values of the input current Iin and the coil current IL (S402).

  The material detection unit 61 determines whether the cooking container 10 is an aluminum pan (S403). If it is determined that the pan is an aluminum pan, the controller 65 determines that heating is not possible and stops heating (S405). If it is not an aluminum pan, the type 631 of the pan determined by the material detection unit 61 is stored in the storage unit 63 (S404). The controller 65 gradually increases the conduction time Ton of the first switching element 53 at a predetermined increase rate (S406) and continues heating.

  The control unit 35 determines whether the stop delay condition is satisfied (S407). Specifically, based on the output of the material detection unit 61, it is determined whether or not the input current Iin exceeds the set value Io. When the input current Iin exceeds the set value Io, the process proceeds to the pot swing determination step (B). That is, the control unit 65 enables the stop delay function 652 to operate. When the input current Iin does not exceed the set value Io, the process proceeds to the accessory determination step (A). That is, the control unit 65 disables the stop delay function 652.

4.1 Judgment of small items (prevention function of small items)
FIG. 5 shows a flow at the time of accessory determination. The material detector 61 determines whether the values of the input current Iin and the coil current IL (the voltage Vc of the resonant capacitor C2) are within the accessory area 23 (S501). The material detection unit 61 outputs the determined result to the control unit 65. When the result from the material detection unit 61 indicates that it is in the accessory area 23, the controller 65 determines that an accessory or an aluminum pan is placed and stops heating (S502). If it is not in the accessory area 23, it is determined that a pan made of an appropriate material is placed at an appropriate position, and normal heating control (S503 and S504) is performed. Specifically, the conduction time of the switching element 53 is gradually increased to determine whether or not the input current Iin exceeds a target value (S503). The target value is a current value corresponding to the thermal power and temperature preset by the user via the input unit 71. If the target value has not been reached (No in S503), the process returns to S406 in FIG. 4 to increase the conduction time Ton of the first switching element 53 until the target value is reached. If the target value is exceeded (Yes in S503), the conduction time Ton of the first switching element 53 is decreased (S504), and the process returns to S407 in FIG.

4.2 Pan swing judgment (stop delay function)
In FIG. 6, the flow at the time of a pan swing determination is shown. The material detection unit 61 determines whether or not the values of the input current Iin and the coil current IL (the voltage Vc of the resonance capacitor C2) are within the accessory area 23 (S601). If it is not in the accessory area 23, the control part 65 performs normal heating control (S608 and S609). Steps 608 and 609 are the same control as S503 and S504 in FIG. Specifically, it is determined whether or not the input current Iin exceeds the target value (S608). If the target value has not been reached (No in S608), the process returns to S406 in FIG. 4, and the conduction time Ton of the first switching element 53 is gradually increased until the target value is reached. If it exceeds the target value (Yes in S608), the conduction time Ton of the first switching element 53 is decreased (S609), and the process returns to S407 in FIG.

  If it is in the accessory area 23 (Yes in S601), the accessory detection stop delay operation is started (S602 to S607). When the small object detection stop delay operation is started, the conduction time Ton of the first switching element 53 is minimized (Min.) And the heating is continued (S602).

  The controller 65 determines whether there is no change in the material of the cooking container 10 (S603). That is, the current pan material output from the material detection unit 61 is compared with the pan material stored in the storage unit 63 in S404 to determine whether they are the same. If there is a change in the material of the pan, the heating is stopped (S606). If there is no change in the material of the pan, the control unit 35 detects whether the values of the input current Iin and the input current IL (the voltage Vc of the resonant capacitor C2) are within the pan swing area 25 or the accessory area 23. The discrimination result from the unit 61 is input (S604).

  If it is neither in the pot swing area 25 nor in the accessory area 23 (No in S604), it is determined whether or not 4 zvp (zero voltage pulse), that is, a time corresponding to two cycles of the commercial power source has passed (S607). If 4zvp has not elapsed, the process returns to S602. When 4 zvp elapses outside the pan swing area, it is determined that the pan has been placed on the heating coil 55 again, the normal heating control is resumed, and the heating output is increased again (S608 and S609).

  If it is in the accessory area 23 or the pot shake area 25 (Yes in S604), it is determined whether or not a predetermined time (for example, 2 seconds) has elapsed (S605). If 2 seconds have not elapsed, the process returns to S602. When 2 seconds have elapsed after detecting that it is the pan swing area 25 (Yes in S605), the heating is stopped (S606). Usually, when the pan is shaken when cooking the fried food, the pan does not leave the heating coil 55 for a long time. That is, since the pan is returned to the heating coil 55 within 2 seconds, there is little possibility of staying in the pan swing area 25 for 2 seconds or more. Therefore, if it becomes out of the accessory area 23 and out of the pan swing area (No in S604) before 2 seconds elapse, it returns to normal heating control and increases the heating output again. When 2 seconds or more have elapsed, it is determined that the pan is not shaken, and heating is stopped (S606).

  As described above, according to the present embodiment, when the input current Iin does not exceed the set value Io (No in S407) and the values of the input current Iin and the coil current IL enter the accessory area 23 (S501). Yes), the heating is stopped (S502). On the other hand, after the input current Iin exceeds the set value Io (Yes in S407), when the values of the input current Iin and the coil current IL enter the accessory area 23 (Yes in S601), heating is not stopped. (S602). Thereby, while being able to prevent heating of small articles, such as a spoon and a fork, when cooking by shaking a pot, cooking performance can be improved and usability can be improved. When the pan is shaken, heating is not stopped even if the pan is separated from the heating coil 55, and when the pan is returned to the heating coil 55 again, the heating power can be increased immediately. Therefore, it is possible to cook with high heating power when cooking fried foods.

  Further, when the stop delay function 652 is activated and heating is continued, the conduction time of the first switching element 53 is minimized, so that safety can be ensured.

  In the pot swing determination of FIG. 6, the standard for determining that the pan has moved away from the heating coil 55 when the pan is shaken is that when the pan enters the accessory area 23 (Yes in S <b> 601), whereas the pan is on the heating coil 55. The criterion for determining that the return has been made is based on the time when it is outside the accessory area 23 and the pan swing area 25 (No in S604). Thus, by setting the reference when returning to the normal operation by determining that the pan has returned to the heating coil 55 as the pan swing area 25 instead of the accessory area 23, the condition for returning to the normal operation becomes stricter. A hysteresis function can be provided. Therefore, the operational stability is further improved.

  Moreover, in this embodiment, when the stop delay function 652 act | operates and heating is continued, it is judged whether there is any change in the material of a pan (S603). This is to cope with a case where the user replaces the heated pan with another pan without stopping the heating. In order to operate the stop delay function 652 safely, it is preferable that the stop delay function 652 be limited to the same pot type as the initially determined pot type. Therefore, it is judged whether there is any change in the material of the pan while the heating is actually continued. When the material of the pan changes during the heating (Yes in S603), the safety is further improved by stopping the heating (S606). When the materials are the same, the characteristics of the coil current IL / input current Iin are the same, so that safety is ensured even if heating is continued.

  Further, the user can control whether or not to operate the stop delay function 652, that is, whether or not to perform the pot shake determination (FIG. 6) by switching on / off the switch 711 in FIG. . When the switch 711 is on, the above-described processes of FIGS. 4 to 6 are performed. When the switch 711 is off, after S406 in FIG. 4, all the small object determination (FIG. 5) processing is performed without determining whether or not the stop delay condition is satisfied (S407). By turning on the switch 711 only when the user cooks by cooking the pan, the operation of the stop delay function 652 can be limited to when the pan is shaken. Thereby, safety is further improved.

5). Modified example
5.1 Return to thermal power after the pot has been shaken Note that there is no change in the material of the pot (Yes in S603), and the heating is performed with the output at the minimum (S602), and then the normal operation is resumed to increase the output. In the case (S406), the rate of increase in the conduction time of the first switching element 53 is reduced from that during normal heating operation until the power is restored to the power before minimizing the output (before determining that the pot is being shaken). May be enlarged. Thereby, it can return to the heating power at the time of normal heating operation quickly.

  In addition, the conduction time of the first switching element 53 when the stop delay function 652 is working and continuing heating should be shorter than the normal conduction time when the stop delay function 652 is not working. The minimum time is preferable as in the present embodiment.

5.2 Control from Temporary Stop to Resume Heating In addition, in FIG. 4 to FIG. 6, after stopping the heating (S 405, S 502, S 606), it is described that the process is terminated. For a predetermined period (for example, 30 seconds) after the start of heating, the process returns to S401 in FIG. 4 and the process is repeated. FIG. 7 shows a flow from the heating stop (S405, S502, S606) of FIGS. 4 to 6 to the return to the heating start (S401) of FIG.

  In FIG. 7, the control unit 65 determines whether or not the stop delay function 652 was operating before stopping the heating, that is, whether or not the heating continuation in S <b> 602 was performed (S <b> 701). If the stop delay function 652 is working, it is determined whether the pan temperature is equal to or higher than a predetermined value (for example, 60 degrees) based on the output of the temperature detector 64 (S702). When the stop delay function 652 is not operating before stopping the heating (No in S701) or when the pan temperature is not equal to or higher than the predetermined value (No in S702), the stop time is set to a normal time (for example, 2 seconds). (S705). If the temperature of the pan is equal to or higher than the predetermined value (Yes in S702), it is determined that the pan was shaken before stopping the heating, and the stop time is set to a shorter time (for example, 0.5 seconds) (S703). ). It is determined whether or not the set stop time has elapsed (S704), and heating is started when the stop time has elapsed. Thus, when the temperature of the pan is high, the stop time is shortened and heating is started immediately. Therefore, even when the pan stays in the pan swing area for 2 seconds or more when the pan is shaken and heating is temporarily stopped, the reheating can be accelerated.

5.3 Stop Delay Condition In this embodiment, as a condition for operating the stop delay function 652, the input current Iin> the set value Io. However, even when the pan is not heated, there is a possibility that the input delay Iin exceeds the set value Io and the stop delay function 652 is activated due to malfunction of the inverter due to power supply abnormality or external noise. is there. If the stop delay function 652 is activated, the heating is continued even when the accessory area 23 is entered. Therefore, in order to further improve the safety, it is preferable to make the conditions for operating the stop delay function 652 (performing the pot swing determination) more strict.

  For example, the amount of input power supplied to the inverter 5 may be integrated after heating is started, and the stop delay function 652 may not be operated until the integrated power value exceeds a predetermined value. That is, the stop delay condition (S407) for operating the stop delay function 652 may be “input current Iin> set value Io” and “integrated power> predetermined value”.

  Further, the stop delay function 652 may not be operated until the temperature of the pan exceeds a predetermined temperature (for example, 60 degrees). That is, the stop delay condition (S407) for operating the stop delay function 652 may be “input current Iin> set value Io” and “pan temperature> predetermined temperature”. Further, when all of “input current Iin> set value Io”, “integrated power> predetermined value”, and “pan temperature> predetermined temperature” are satisfied, it may be determined that the stop delay condition is satisfied.

  Here, the temperature of the pan 10 is detected by the temperature detection element 8 and the temperature detection unit 64. A specific example of the temperature detecting element 8 is shown in FIG. The temperature detection element 8 can measure thermistor 8 a provided so as to be in contact with the back surface of the top plate 9 or infrared rays radiated from the bottom surface temperature of the pan 10 inside the outer periphery of the heating coil 55 below the top plate 9. It is the infrared sensor 8b arranged. The thermistor 8 a detects the temperature of the cooking container 10 by heat conduction through the top plate 9. The infrared sensor 8 b detects infrared rays radiated from the cooking container 10 via a non-painting portion 81 provided on the top plate 9. The induction heating cooker of this embodiment may include both the thermistor 8a and the infrared sensor 8b, or may include either one. Since the infrared sensor 8b can detect the temperature of the pan 10 with infrared rays, the infrared sensor 8b has good responsiveness and is suitable for cooking while shaking the pan with a high heating power such as fried food.

  FIG. 9A shows the detected temperatures of the thermistor 8a and the infrared sensor 8b. When heating is started, the detected temperatures of the thermistor 8a and infrared sensor 8b gradually increase. In the above-described example, the condition for operating the stop delay function 652 includes that the detected temperature of the thermistor 8a or the infrared sensor 8b exceeds a predetermined temperature H1 (for example, 60 degrees). Therefore, when the pan temperature is detected by the thermistor 8a, the stop delay condition is satisfied at the timing of time T2, and when the pan temperature is detected by the infrared sensor 8b, the stop delay condition at the timing of time T1. Meet. When the detection temperature of the thermistor 8a or the infrared sensor 8b is higher than the predetermined temperature H1, it can be determined that cooking is in progress, so that the stop delay function 652 can be executed more safely by adding conditions for the pan temperature. . The temperatures H2 to H5 in FIG. 9A and FIG. 9B will be described together with the following overheat prevention function 653.

5.4 Overheat prevention function The induction heating cooker of this embodiment gives priority to the control by the overheat prevention function 653 over the stop delay function 652. The over-temperature prevention function 653 is a function for preventing oil ignition, and is a function for stopping the thermal power when the detected temperature is high and returning the thermal power again when the detected temperature is lowered.

  FIG. 9A shows the detected temperature H3 of the thermistor 8a and the detected temperature H5 of the infrared sensor 8b when heating is stopped by the overheat prevention function 653, and the detected temperature H2 and the infrared of the thermistor 8a when heating is resumed. The detected temperature H4 of the sensor 8b is shown. Moreover, the thermal power based on the stop / resumption of heating is shown in FIG. When the temperature detected by the thermistor 8a reaches the predetermined value H3 or the temperature detected by the infrared sensor 8b reaches the predetermined value H5, the overtemperature prevention function 653 stops the inverter 5 and sets the thermal power to zero (T3, T5). Further, after the inverter 5 is stopped, when the temperature detected by the thermistor 8a falls to the predetermined value H2 or the temperature detected by the infrared sensor 8b falls to the predetermined value H4, the inverter 5 is operated again (T4). Here, the relationship between the detected temperature of the thermistor 8a and the infrared sensor 8b when the inverter is operated / stopped is H2 <H3 <H4 <H5.

  The operation of stopping the inverter 5 by the overtemperature prevention function 653 is executed even when the stop delay function 652 is activated and heating is continued. Thus, oil ignition can be prevented even when cooking by shaking the pan.

5.5 Overcurrent prevention function The induction heating cooker of this embodiment gives priority to the control by the overcurrent prevention function 654 over the stop delay function 652. When the cooking vessel 10 is an aluminum pan, an overcurrent flows into the inverter 5 (see FIG. 2). The overcurrent prevention function 654 is a function for preventing the aluminum pan from being heated, and is a function for stopping the inverter 5 when the cooking vessel 10 placed on the top plate 9 is an aluminum pan.

  FIGS. 10A to 10C show the input current Iin, the current ISW1 flowing through the first switching element 53, and the heating power, respectively. Normally, the overcurrent detection unit 62 compares the current ISW1 of the first switching element correlated with the coil current IL with the normal detection level I10 shown in FIG. When ISW1 exceeds the detection level I10, it is determined that an overcurrent is flowing.

  10A to 10C show a state where the cooking container 10 is placed on the aluminum pan from the iron pan. As shown in FIG. 10B, when the cooking vessel 10 is an iron pan, the current ISW1 of the first switching element does not reach the detection level I10, and thus heating is continued. As shown in FIG. 10A, when the iron pan is shifted from right above the heating coil 55 at time T1, the input current Iin decreases. When the user shifts the iron pan and gradually puts the aluminum pan on the heating coil 55, and then places the aluminum pan completely on the heating coil 55, the input current Iin is small but large. .

  When the current ISW1 flowing through the first switching element 53 exceeds the detection level T10, the control unit 65 stops the inverter 5 (time T4). In the present embodiment, the control unit 65 stops the inverter 5 if the overcurrent detection unit 62 detects an overcurrent even when the heating is continued by the stop delay function 652.

  Note that this detection level may be variable. When the cooking container 10 is shifted from right above the heating coil 55, it may be replaced with an aluminum pan from an iron pan or the like. Therefore, when the iron pan is shifted from right above the heating coil 55, preparation is made when it is replaced with an aluminum pan. That is, when the control unit 65 monitors the detection result of the material detection unit 61 and the current value of the input current Iin reaches the accessory area determination value I1 when contacting the accessory area 23 (time T2), the pan is shifted. The overcurrent detection unit 62 is notified. The overcurrent detection unit 62 reduces the detection level to the current value I11 so that the detection sensitivity is increased. Since the current of the first switching element 53 or the second switching element 54 reaches the detection level I11 at time T3, the control unit 65 can stop heating at time T3. Therefore, heating of the aluminum pan can be stopped early.

  Originally, when an aluminum pan is placed during heating, the accessory heating prevention function 651 is activated to protect the inverter 5, and the inverter 5 stops. However, in the present invention, the accessory heating prevention function 651 does not work when the iron pan that has been heated first exceeds the accessory area determination value I1 indicating the boundary with the accessory area and the stop delay function 652 becomes operable. . In such a case, even when the aluminum pan is suddenly replaced, the inverter 5 can be stopped by the overcurrent prevention function 654, and the safety is further improved.

  The induction heating cooker of the present invention has the effect that heating is stopped when a small object is detected, and heating can be continued when cooking while shaking the pan. Useful as.

The block diagram which shows the induction heating cooking appliance of embodiment of this invention Characteristics of pan coil current / input power (A) is a figure which shows the characteristic of the voltage / input current of the resonant capacitor at the time of a pot area and the accessory area and a pot swing area, (b) shows the positional relationship when a cooking container remove | deviates from just above a heating coil. Figure Flowchart from the start of heating to the determination of small items or pan shake Small item flow chart Flow chart of pan swing judgment Flowchart from heating pause to restart The figure which shows the example of the temperature detection element (A) is a figure which shows the detection temperature of an infrared sensor and a thermistor, (b) is a figure which shows a thermal power. It is a figure at the time of replacing an iron pan with an aluminum pan, (a) is a figure which shows input current Iin, (b) is a figure which shows the electric current of a 1st switching element, and the detection level of an overcurrent, (c). Is a figure showing firepower

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power source 2 Power switch 3 Input current detection element 4 Rectifier circuit 5 Inverter 6 Control means 7 Operation part 8 Temperature detection element 9 Top plate 10 Cooking container 51 Choke coil 52 Coil current detection element 53 1st switching element 54 2nd Switching element 55 Heating coil C1 Smoothing capacitor C2 Resonance capacitor 61 Material detection unit 62 Overcurrent detection unit 63 Storage unit 64 Temperature detection unit 71 Input unit 72 Heating installation unit 73 Display unit 711 Switch

Claims (15)

A top plate for placing an object to be heated;
A heating coil that is disposed below the top plate and heats the object to be heated;
An inverter that converts an input current into a high-frequency current and supplies the high-frequency current to the heating coil;
Comparing the magnitude of the input current and the magnitude of the high-frequency current, the comparison result is within the first region indicating that the material of the object to be heated is a material that should not be heated, or even if heated A material detection unit that determines whether the material is in a second region indicating that it is a good material and determines the type or shape of the material that forms the heated object based on the comparison result;
When the discrimination result of the material detection unit indicates that it is within the first region, it has a heating prevention function for stopping the inverter, and the output of the inverter is based on the discrimination result of the material detection unit. A control unit to control,
Have
The control unit indicates that the input current exceeds a predetermined value as a stop delay condition, and indicates that the determination result of the material detection unit has entered the first region after the stop delay condition is satisfied. Has a stop delay function to continue the operation without stopping the inverter,
An induction heating cooker characterized by that. The inverter has a switching element for controlling the supply amount of the high-frequency current supplied to the heating coil, and the supply amount of the high-frequency current increases when the conduction time of the switching element is lengthened. When the conduction time is shortened, the supply amount of the high-frequency current decreases,
The controller is configured such that a conduction time of the switching element when the inverter is operated by the stop delay function is shorter than a conduction time of the switching element when the inverter is operated in the second region. The induction heating cooker according to claim 1. The material detection unit provides a third region around the outside of the first region in the second region, and determines whether the comparison result is in the third region,
In the case where the operation of the inverter is continued by the stop delay function, the control unit sets the switching element to a predetermined driving condition so that the input current is smaller than before the operation of the inverter is continued by the stop delay function. If the determination result of the material detection unit returns to the outside of the first region and the third region before a predetermined period of time elapses after the stop delay function operates, the stop is performed. The induction heating cooker according to claim 2, wherein the delay function is canceled and the output of the inverter is gradually increased to a set value. A temperature detecting unit for detecting the temperature of the object to be heated;
The induction according to any one of claims 1 to 3, wherein the control unit adds to the stop delay condition that the temperature of the object to be heated detected by the temperature detection unit exceeds a predetermined temperature. Cooking cooker.   The said control part integrates the electric power input into the said inverter after starting heating, and adds that the integrated electric power exceeds predetermined amount to the said stop delay conditions. An induction heating cooker according to any one of the claims.   The control unit indicates that the determination result of the material detection unit is within the first region continuously for a predetermined period after entering the first region from the second region, The induction heating cooker according to claim 1, wherein the inverter is stopped. The material detection unit provides a third region around the outside of the first region in the second region, and determines whether the comparison result is in the third region,
When the control unit indicates that the determination result of the material detection unit is within the third region after entering the first region from the second region, the inverter is caused by the stop delay function. The induction heating cooker of Claim 1 which continues operation | movement of.   The control unit determines that the determination result of the material detection unit is within the first region or the third region for a predetermined period after the first region enters the first region from the second region. The induction heating cooker according to claim 7, wherein, when shown, the inverter is stopped.   The control unit, after operating the inverter by the stop delay function, canceling the operation of the inverter by the stop delay function and increasing the conduction time of the switching element when increasing to the set value, The induction heating cooker according to claim 3, wherein the induction heating cooker is larger than a rate of increase in conduction time of the switching element before the inverter is operated by the stop delay function. A storage unit;
The control unit stores the material type of the object to be heated determined by the material detection unit in the storage unit before satisfying the stop delay condition, and continues the operation of the inverter by the stop delay function. The inverter is stopped when the material type of the object to be heated determined by the material detection unit is different from the material type stored in the storage unit. An induction heating cooker according to any one of the claims. A temperature detecting unit for detecting the temperature of the object to be heated;
The control unit has a shorter stop time when the detected temperature of the temperature detection unit after stopping the inverter exceeds a predetermined temperature than a stop time when the detected temperature does not exceed the predetermined temperature. The induction heating cooker according to claim 1, wherein the inverter is operated again when the stop time elapses. A temperature detecting unit for detecting the temperature of the object to be heated;
The control unit includes an over-temperature prevention function that stops the operation of the inverter when the temperature of the object to be heated is equal to or higher than a predetermined temperature.
The induction heating cooker according to claim 1, wherein the inverter is stopped when the overheat prevention function is activated while the operation of the inverter is continued by the stop delay function. Based on the value of the high-frequency current, further comprising an overcurrent detection unit for detecting whether an overcurrent flows through the inverter;
The control unit has an overcurrent prevention function for stopping the operation of the inverter when the overcurrent detection unit detects that an overcurrent flows through the inverter.
The induction heating cooker according to claim 1, wherein when the overcurrent prevention function is activated while the operation of the inverter is continued by the stop delay function, the inverter is stopped.   The control unit increases the detection sensitivity of the overcurrent detection unit while continuing the operation of the inverter by the stop delay function as compared to a case where the operation of the inverter is not continued by the stop delay function. The induction heating cooker according to claim 13.   The induction heating cooker according to claim 1, further comprising a switch for enabling a user to determine whether or not to operate the stop delay function.

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