JP5854913B2 - Induction heating cooker - Google Patents

Description

  The present invention relates to an induction heating cooker that induction-heats a pan placed on a top plate by a heating coil.

  In the conventional induction heating cooker, the material of the pan placed on the top plate is determined based on the input current detected by the input current detection means and the coil current detected by the coil current detection means. (For example, refer to Patent Document 1).

Japanese Patent Laying-Open No. 2010-3482 (5th page, FIG. 2)

  In the above-described conventional induction heating cooker, the input current and the coil current change due to changes in the pan temperature and the coil temperature, and as a result, there is a possibility that the material determination of the pan may be erroneous.

The present invention has been made to solve the above-described problems, and a first object is induction heating cooking that can accurately determine the material of the pan without being affected by changes in the pan temperature or the coil temperature. To get a vessel.
The second object is to obtain an induction heating cooker that can perform appropriate heating control according to the material of the pan, in addition to accurately determining the material of the pan.

  An induction heating cooker according to the present invention includes a heating coil that induction-heats a pan placed on a top plate, a DC rectifier circuit that converts AC power from an AC power source into DC power, and a DC current of the DC rectifier circuit. An inverter that converts the current into a high frequency current and supplies it to the heating coil, an input current detection means that detects an input current from an AC power supply, a coil current detection means that detects a coil current flowing through the heating coil, and a top plate A pan temperature detecting means for detecting the pan temperature, a coil temperature detecting means for detecting the coil temperature of the heating coil, and a first threshold value for determining the material of the pan are set in advance. The first threshold value is corrected based on the temperature change of both the temperature and the coil temperature, the corrected first threshold value is compared with the coil current and the switch conduction ratio of the inverter, and the comparison result is obtained. In which to determine the material of the pan, and a control means for driving the inverter with drive signals suitable for the material of the determined pan based on.

  According to the present invention, while the heating coil is driven, the first threshold value is corrected based on the temperature change of both the pan temperature and the coil temperature, and the corrected first threshold value, the coil current, and the switch conduction ratio of the inverter are corrected. And the material of the pan is determined based on the comparison result. Thereby, the material determination of a pan can be performed correctly, without being influenced by the change of the temperature of a pan or a heating coil. In addition, since the drive signal control line can be accurately selected regardless of the temperature of the pan or the heating coil, it is possible to suppress the generation of interference sound from low thermal power to high thermal power.

It is a perspective view which shows the external appearance of the induction heating cooking appliance which concerns on embodiment. It is a schematic circuit diagram of the induction heating cooking appliance which concerns on embodiment. It is a mapping figure of the pan of the magnetic system A and the magnetic system B with respect to the threshold value X in the relationship between an input current value and a coil current value. It is a mapping figure which shows the threshold value X with respect to the coil temperature and pan temperature at the time of pan use of the magnetic system A and the magnetic system B in the relationship between an input electric current value and a coil electric current value. It is a figure which shows the drive signal control line for magnetism, and the drive signal control line for normal operation in the relationship between a frequency and the switch conduction ratio by the side of a high electric potential. It is a figure which arrange | positions the pan of the magnetic system B (weak magnetism or nonmagnetic) in heating operation with respect to the threshold value Z after correction | amendment, and arrange | positions from conduction ratio data and a coil current. It is a flowchart which shows operation | movement of the induction heating cooking appliance which concerns on embodiment. It is a flowchart following FIG. It is a flowchart which shows the operation | movement of the material determination of the initial load shown instead of FIG.

FIG. 1 is a perspective view showing the appearance of the induction heating cooker according to the embodiment.
In FIG. 1, a top plate 2 attached to the main body case 1 via a frame 3 is provided on the upper portion of the main body case 1 of the induction heating cooker 100. The top plate 2 is made of heat-resistant tempered glass, and is printed on the back surface so that the inside cannot be seen. On the surface of the top plate 2, a left heating port HL, a right heating port HR, and a central heating port HC indicating the placement position of the cooking container are displayed by a method such as printing. In the main body case 1, three heating coils are arranged corresponding to the heating ports HL, HR, and HC.

  On the front side of the top plate 2 described above, the thermal power display units 4 and 5 for displaying the thermal power of the left heating port HL and the right heating port HR and the liquid crystal display unit for displaying the operating state of each heating port HL, HR and HC. 7, 8, and 9 are provided. Furthermore, a thermal power display unit 6 that displays the thermal power of the central heating port HC is provided at the rear center of the top plate 2.

  An upper surface operation unit 10 is provided on the front side of the frame 3. The upper surface operation unit 10 includes, for example, a heating power setting operation unit provided corresponding to each of the left heating port HL, the right heating port HR, and the central heating port HC, and a grill operation unit that operates heating of the grill. An intake / exhaust cover 13 that covers the intake port 11 and the exhaust port 12 provided in the main body case 1 is detachably provided on the frame 3 on the rear side of the top plate 2.

  A grill door 14 that can move back and forth is provided on the front surface of the main body case 1. Further, front operation sections 15 and 16 are provided on both sides of the grill door 14 on the front surface of the main body case 1. The left front operation unit 15 is an operation unit for adjusting the heating power of the left heating port HL, and the right front operation unit 16 is an operation unit for adjusting the heating power of the right heating port HR.

Next, the circuit configuration of the induction heating cooker described above will be described with reference to FIG.
FIG. 2 is a schematic circuit diagram of the induction heating cooker according to the embodiment. In the present embodiment, since the main circuit configuration for driving the three heating coils is the same, only the circuit configuration on the right heating port HR side will be described.

  The induction heating cooker according to the present embodiment includes a full-wave rectifier circuit 21 connected to an AC power source, for example, a commercial power source, and an inductor 22 and a smoothing capacitor 23 connected in series between outputs of the full-wave rectifier circuit 21. For example, a half-bridge type inverter 24 connected in parallel to the smoothing capacitor 23, and a heating coil 25 and a resonance capacitor connected in parallel to the low-potential side switching element 24b among the switching elements 24a and 24b made of IGBT, for example. 26, an input current detection means 27 for detecting an input current from a commercial power source, a coil current detection means 28 for detecting a current to the heating coil 25, and a lower surface of the top plate 2, and via the top plate 2 A pan temperature detecting means 29 for detecting the pan temperature and a coil temperature detector for detecting the coil temperature of the heating coil 25 Includes a means 30, for example, a control circuit 31 composed of a microcomputer. The full-wave rectifier circuit 21, inductor 22 and smoothing capacitor 23 described above constitute a DC rectifier circuit.

Next, the threshold value for determining the pot material by the control circuit 31 and the heating control suitable for the material of the pot will be described with reference to FIGS.
3 is a mapping diagram of the pans of the magnetic system A and the magnetic system B with respect to the threshold value X in the relationship between the input current value and the coil current value, and FIG. 4 is the magnetic system A and the magnetic system in the relationship between the input current value and the coil current value. FIG. 5 is a mapping diagram showing the coil temperature and the threshold value X relative to the pan temperature when the pan of B is used. FIG. 5 shows the drive signal control line for magnetism and the drive signal control for normal operation in the relationship between the frequency and the switch conduction ratio on the high potential side. FIG. 6 is a diagram showing a line, and FIG. 6 is a diagram showing a pan of a magnetic system B (weak magnetic or non-magnetic) during a heating operation with respect to a corrected threshold value Z, based on conduction ratio data and coil current.

  As shown in FIG. 3, the control circuit 31 stores, as data, a threshold value X (second threshold value) for determining the material of the pot 40 from the intersection of the input current value and the coil current value. When the control circuit 31 drives the inverter 24, the control circuit 31 corrects the threshold value X based on the temperature change of both the coil temperature and the pan temperature, and determines the material of the pan 40 from the corrected threshold value X, the input current and the coil current. An initial load determination mode for determination is provided.

  When the threshold value X is not corrected, as shown in FIG. 3, the pan 40 of the magnetic system A (ferromagnetic material) is positioned below the threshold value X, and the pan 40 of the magnetic system B (weak magnetic material or non-magnetic material). Is higher than the threshold value X, but is close to the threshold value X. The reason for correcting the threshold value X is to cope with an input current value and a coil current value that change due to temperature changes of both the coil temperature and the pan temperature. In the pan 40 of the magnetic system A, as shown in FIG. 4A, when the coil temperature is high and the pan temperature is low (coil Hot-pan Cold), it is set higher than the threshold value X before correction. Further, as shown in FIG. 4B, particularly when the coil temperature is low and the pan temperature is high (coil Cold-pan hot), the threshold value X before the correction is set low. The correction of the threshold value X is set according to the temperature change of both the coil temperature and the pan temperature, as described above.

  When determining the material of the pan 40 in the initial load determination mode, the control circuit 31 drives the inverter 24 based on the drive signal control line corresponding to the determination result. As shown in FIG. 5, the drive signal control line includes a magnetic drive signal control line A and a normal operation drive signal control line B. The horizontal axis represents the drive frequency, and the vertical axis represents the switch conduction ratio on the high potential side. (Switching element 24a) is shown.

  The drive signal control line B for normal operation is a line indicated by a correlation between a predetermined drive frequency range (first drive frequency range) having a lower limit frequency f0 and an upper limit frequency f1, and the switch conduction ratio. Used when the material is a magnetic system B (weak magnetic material or non-magnetic material). The drive signal control line A for magnetism is a line indicated by the correlation between the drive frequency range (second drive frequency range) in which the lower limit frequency is f0 and the upper limit frequency is f2 lower than f1, and the switch conduction ratio. Used when the material is magnetic system A (ferromagnetic material). The frequency difference between the upper limit frequency f2 and the lower limit frequency f0 of the drive frequency range in the magnetic drive signal control line A is about 4 kHz or less. By setting the frequency as described above, for example, even when the pan 40 of the magnetic system A is simultaneously heated by the left heating port HL and the right heating port HR, generation of annoying interference sound due to the frequency difference of the drive signals is suppressed. be able to.

  The control circuit 31 performs a thermal power (electric power) feedback control after the initial load determination, and executes an operation load determination mode in which the material determination of the pan 40 is performed periodically. The control circuit 31 stores, as data, a threshold value Z (first threshold value) for determining the material of the pan 40 from the conduction ratio data of the switching elements 24a and 24b and the coil current value. The control circuit 31 corrects the threshold value Z according to temperature changes of both the coil temperature and the pan temperature, and determines the material of the pan 40 from the corrected threshold value Z, the conduction ratio data, and the coil current (see FIG. 6). . The threshold value Z before correction is set corresponding to each set thermal power, and the threshold value Z corresponding to the thermal power set by the operation of the upper surface operation unit 10 is selected and corrected.

  The reason for determining the material of the pan 40 again is that, for example, when the pan 40 of the magnetic system A is heated by the right heating port HR, it may be replaced with the pan 40 of the magnetic system B. In such a case, the threshold value Z is newly corrected according to the temperature change of both the pot temperature and the coil current, and the material determination of the pot 40 is performed from the corrected threshold value Z, the conduction ratio data, and the coil current. By this material determination, the drive signal control line B for normal operation is switched. Also, for example, when two magnetic system A pots 40 are heated by the magnetic drive signal control line A, even if cold water is put into one of the pots 40, the magnetic drive signal control line A This is so that the control based on it is continued. That is, when cold water is put into one pan 40, the pan temperature decreases, but the threshold value Z is newly corrected according to the temperature change of both the pan temperature and the coil current, and the corrected threshold value Z and the conduction By determining the material of the pan 40 from the ratio data and the coil current, the magnetic drive signal control line A is selected, and the control based on the drive signal control line A is continued. As a result, even if the temperature is lowered by pouring water into one of the pots 40, it is not switched to the drive signal control line B for normal operation, so that an interference sound is generated between the pots 40 of the magnetic system A. Heat cooking can be continued without any problems.

The operation of the induction heating cooker configured as described above will be described with reference to FIGS.
FIG. 7 is a flowchart showing the operation of the induction heating cooker according to the embodiment, and FIG. 8 is a flowchart following FIG.

  For example, when the heating power of the right heating port HR is set by the upper surface operation unit 10 after the pan 40 containing the food is placed on the right heating port HR, the control circuit 31 has a higher frequency (for example, 40 kHz) than that during the heating operation. The drive of the inverter 24 is started by the drive signal (S1). At this time, the control circuit 31 reads the pan temperature detected by the pan temperature detecting means 29 and the coil temperature detected by the coil temperature detecting means 30 (S2). And in S3, the control circuit 31 correct | amends the threshold value X before correction | amendment according to the temperature change of both coil temperature and pan temperature, ie, the applicable conditions in (1)-(4), and thermal power The material determination of the initial load immediately after the start is started (S4).

  First, the control circuit 31 reads the input current detected by the input current detection means 27 and the coil current detected by the coil current detection means 28, respectively, and determines whether the pan 40 is appropriate for heating (S5). . When the control circuit 31 determines that the intersection of the input current and the coil current is equal to or greater than the threshold value for inappropriate heating determination (not shown), the control circuit 31 determines that the pan is a low resistance material pan such as aluminum and stops driving the inverter 24. (S6).

  The control circuit 31 determines that the pan 40 is appropriate for heating when the intersection of the input current and the coil current is lower than the threshold value for determining inappropriate heating, and then determines whether the material of the pan 40 is the magnetic system A. Determine (S7). When the intersection of the input current and the coil current is above the corrected threshold value X, the control circuit 31 determines that the magnetic system B is present, but when the intersection of the input current and the coil current is below the corrected threshold value X, the magnetic system A is determined. The inverter 24 is driven based on the magnetic drive signal control line A, and heating of the pan 40 is started (S8).

  In this case, a drive signal corresponding to the set thermal power and a switch conduction ratio (high potential side) are selected in a drive frequency range having an upper limit frequency f2 and a lower limit frequency f0, and an inverter 24 is generated using the drive signal. Drive. Thereby, even if the pan 40 of the magnetic system A is heated by either the left heating port HL or the central heating port HC after this, the inverter 24 is driven in the driving frequency range having the upper limit frequency f2 and the lower limit frequency f0. Therefore, the frequency difference of the drive signal becomes about 4 kHz or less, and the generation of interference sound between the pans 40 is suppressed.

  Further, when the control circuit 31 determines in S7 that the magnetic system B is based on the corrected threshold value X, input current and coil current, the control circuit 31 drives the inverter 24 based on the drive signal control line B for normal operation, and Heating is started (S9). In this case, the control circuit 31 generates a drive signal by selecting a drive frequency and a switch conduction ratio corresponding to the set thermal power within a drive frequency range having an upper limit frequency f1 and a lower limit frequency f0, and the inverter 24 is driven by the drive signal. To drive. In the magnetic system B (weak magnetic material or nonmagnetic material pan 40), it has been experimentally found that the interference sound due to the frequency difference of the drive signals between the two heating ports hardly occurs. Since it is difficult to operate with a low heating power when operated with the drive signal control line A, the drive signal control line B for normal operation is operated.

  Thereafter, the control circuit 31 shifts to the operation of the thermal power feedback control, and periodically executes the operation load determination mode during the operation of the thermal power feedback control (see FIG. 8). First, the control circuit 31 reads the pan temperature detected by the pan temperature detecting means 29 and the coil temperature detected by the coil temperature detecting means 30 (S10). And the control circuit 31 correct | amends the threshold value Z corresponding to a setting thermal power in S11 according to the temperature change of both coil temperature and pan temperature, ie, the applicable conditions in (1)-(4). (Refer to FIG. 6), load material determination during operation is started (S12).

  First, the control circuit 31 determines whether or not the pan 40 is appropriate from the conduction ratio data of the switching elements 24a and 24b of the inverter 24 and the coil current detected by the coil current detection means 28 (S13). When the control circuit 31 determines that the intersection of the continuity ratio data and the coil current is within a threshold for inappropriate heating determination (not shown), the control circuit 31 determines that the pan is a low-resistance material pan such as aluminum or no load, and performs heating. Stop (S14).

  When the intersection of the conduction ratio data and the coil current is outside the threshold value for determining inappropriate heating, the control circuit 31 determines that the pot 40 is appropriate for heating and determines whether the material of the pot 40 is the magnetic system A ( S15). For example, the control circuit 31 determines that the magnetic system is B when the intersection of the conduction ratio data and the coil current is on the left side of the corrected threshold Z, but the intersection of the conduction ratio data and the coil current is on the right side of the corrected threshold Z. In some cases, the magnetic system A is determined, and the inverter 24 is driven based on the magnetic drive signal control line A to continue heating the pot 40 (S16).

  In this case, the control circuit 31 generates a drive signal by selecting a drive frequency and a switch conduction ratio corresponding to the set thermal power in a drive frequency range having an upper limit frequency f2 and a lower limit frequency f0, and the inverter 24 is driven by the drive signal. Drive. Thereby, even if the pan of the magnetic system A is heated at either the left heating port HL or the central heating port HC, the inverter 24 is driven in the driving frequency range having the upper limit frequency f2 and the lower limit frequency f0. The frequency difference between the drive signals is about 4 kHz or less, and the generation of interference sound between the pans 40 is suppressed.

  Further, when the control circuit 31 determines in S15 that the magnetic system B is based on the corrected threshold value Z, the conduction ratio data, and the coil current, the control circuit 31 drives the inverter 24 based on the drive signal control line B for normal operation, The heating of the pan 40 is continued (S17). In this case, the control circuit 31 generates a drive signal by selecting a drive frequency and a switch conduction ratio corresponding to the set thermal power within a drive frequency range having an upper limit frequency f1 and a lower limit frequency f0, and the inverter 24 is driven by the drive signal. To drive.

  As described above, according to the embodiment, when the inverter 24 is driven, the threshold value X is corrected based on both the coil temperature and the pan temperature, and the corrected threshold value X, the input current, and the coil current are used. The material of the pan 40 is determined. Thus, since the threshold value X is corrected according to the temperature change of both the coil temperature and the pan temperature for the material determination of the pan 40, it is affected by the temperature change of the pan 40 and the heating coil 25. In addition, the material determination of the magnetic system A pot 40 and the magnetic system B pot 40 can be performed accurately, and uncomfortable feeling due to the generation of interference sound can be suppressed.

  Further, when performing the thermal feedback control, by correcting the threshold Z for determination of the drive signal control lines A and B according to the temperature change of both the coil temperature and the pan temperature, regardless of the temperature, It is possible to prevent erroneous determination of the pot material determination (magnetic system A / magnetic system B) from low thermal power to high thermal power. Therefore, appropriate heating control can be performed according to the material of the pan 40, and similarly, discomfort due to the generation of interference sound can be suppressed.

  In the embodiment, when the inverter 24 is driven, the threshold value X is corrected based on the temperature change of both the pot temperature and the coil temperature, and the corrected threshold value is determined when the pot 40 is determined to be appropriate for heating. The material of the pan 40 is determined from X, the input current, and the coil current, and heating of the pan 40 is started by a drive signal corresponding to the determination result (see S1 to S9 in FIG. 7). For example, heating may be started after the operation shown in FIG. 9 is performed.

FIG. 9 is a flowchart showing the operation of determining the material of the initial load shown in place of FIG.
As described above, when the heating power is set by the upper surface operation unit 10, the control circuit 31 first starts driving the inverter 24 with a drive signal having a higher frequency (for example, 40 kHz) than in the heating operation (S21), The material determination of the initial load immediately after the thermal power is input is started (S22). First, the control circuit 31 reads the input current detected by the input current detection means 27 and the coil current detected by the coil current detection means 28, respectively, and determines whether the pan 40 is appropriate (S23).

  When the control circuit 31 determines that the intersection of the input current and the coil current is equal to or greater than the threshold value for inappropriate heating determination (not shown), the control circuit 31 determines that the pan is a low resistance material pan such as aluminum and stops driving the inverter 24. (S25). When the intersection of the input current and the coil current is lower than the threshold for inappropriate heating determination, the control circuit 31 determines that the pan 40 is appropriate for heating and heats the pan 40 with a driving signal corresponding to the set heating power. Start (S24). The subsequent operations are performed based on the flowchart shown in FIG. 8 (S10 to S17).

  Thus, when the inverter 24 is driven, it is determined whether or not the pot 40 is appropriate for heating, and when the pot 40 is determined to be appropriate for heating, heating of the pot 40 is started. After the determination, the processing operation of the control circuit 31 is simplified as compared with the embodiment in which heating of the pot 40 is started after determining whether the material of the pot 40 is the magnetic system A or B.

  DESCRIPTION OF SYMBOLS 1 Main body case, 2 Top plate, 3 Frame body, 4, 5, 6 Thermal display part, 7, 8, 9 Liquid crystal display part, 10 Upper surface operation part, 11 Intake port, 12 Exhaust port, 13 Intake / exhaust cover, 14 Grill door, 15, 16 Front operation part, HL, HR, HC heating port, 21 full-wave rectifier circuit, 22 inductor, 23 smoothing capacitor, 24 inverter, 24a, 24b switching element, 25 heating coil, 26 resonant capacitor, 27 inputs Current detection means, 28 coil current detection means, 29 pan temperature detection means, 30 coil temperature detection means, 31 control circuit, 40 pot, 100 induction heating cooker.

Claims (6)

A heating coil for induction heating the pan placed on the top plate;
A DC rectifier circuit that converts AC power from an AC power source into DC power;
An inverter that converts a direct current of the direct current rectifier circuit into a high frequency current and supplies the high frequency current to the heating coil;
An input current detecting means for detecting an input current from an AC power supply;
Coil current detection means for detecting a coil current flowing in the heating coil;
Pan temperature detecting means for detecting the pot temperature via the top plate;
Coil temperature detection means for detecting the coil temperature of the heating coil;
A first threshold value for determining the material of the pan is set in advance, and the first threshold value is corrected based on temperature changes of both the pan temperature and the coil temperature while the heating coil is being driven, The first threshold value is compared with the coil current and the switch conduction ratio of the inverter, the material of the pan is determined based on the comparison result, and the inverter is driven with a drive signal suitable for the determined material of the pan. And an induction heating cooker comprising a control means.   The control means drives the inverter by switching the first drive frequency range and the second drive frequency range based on the magnitude relationship between the coil current and the switch conduction ratio of the inverter and the first threshold value, The second drive frequency range is a drive signal that is narrower than a frequency width of the first drive frequency range and whose upper limit frequency is lower than the upper limit frequency of the first drive frequency range. Item 2. An induction heating cooker according to item 1.   The control means is set in advance with a second threshold value for determining the material of the pan, and when the inverter is driven, the second threshold value is set based on the temperature change of both the pan temperature and the coil temperature. The corrected second threshold value is compared with the input current and the coil current, the material of the pot is determined based on the comparison result, and the inverter is driven with a drive signal suitable for the determined material of the pot The induction heating cooker according to claim 2, wherein:   When the inverter is driven, the control means switches between the first drive frequency range and the second drive frequency range based on the magnitude relationship between the input current and the coil current and the second threshold value. The induction heating cooker according to claim 3, wherein an inverter is driven.   The control means corrects the second threshold to a value higher than a preset value when the coil temperature is higher than the previously acquired value and the pan temperature is lower than the previously acquired value. The induction heating cooker according to claim 3 or 4, characterized by.   The control means corrects the second threshold to a value lower than a preset value when the coil temperature is lower than the previously acquired value and the pan temperature is higher than the previously acquired value. The induction heating cooker according to any one of claims 3 to 5, wherein

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