JP5637265B2 - Induction heating cooker - Google Patents

Description

  The present invention relates to an induction heating cooker.

A conventional induction heating cooker of this type includes three heating coils, and the pan is placed on a top plate facing one heating coil and heated by one heating coil (for example, Patent Document 1). reference). In the conventional induction heating cooker described in Patent Document 1, since the magnetic field contributing to heating is extremely strong on the heating coil wire, the heating distribution of the pan becomes a donut shape that is the same shape as the heating coil wire. Therefore, heating unevenness occurred and cooking performance was not good. In order to reduce heating unevenness, when forming a heating coil, a gap is provided between the inner diameter and outer diameter of the heating coil wire to divide the bundle of heating coil wires, so that the portion with a strong magnetic field is located on the inner side of the heating coil. Many are distributed outside. However, with this method, although the heating unevenness can be reduced to some extent, the heating distribution is still donut-shaped and the pan cannot be heated uniformly.

  Therefore, as another induction heating cooker of this kind, one pan is heated by two heating coils having the same circular center, and the inner heating coil, the outer heating coil, or the inner and outer heating coils are heated. An induction heating cooker that heats the pan by switching both the heating coils and the heating coil through which an electric current flows has been developed (for example, see Patent Document 2). However, when both the inner and outer heating coils are conducted simultaneously, the heating coil wire is in the same state as the heating coil having a gap between the inner diameter and outer diameter, and the heating distribution does not change. Cannot be heated uniformly.

  Then, what heated one pot with the some heating coil which has a different circular center as another induction heating cooking appliance of this kind was developed (for example, refer patent document 3).

  According to the conventional induction heating cooker described in Patent Document 3, by sufficiently shifting the phase of the alternating magnetic field generated by the adjacent heating coils by a half period (= π), sufficient magnetic flux can be generated between the adjacent heating coils. Is supplied and the pan can be heated uniformly.

JP 2007-103110 A JP-A-8-78148 Real Table Sho 60-85096

  However, in the conventional configuration described in Patent Document 3, since the alternating magnetic fields generated by the adjacent heating coils are coordinated between the two heating coils, the cooperation of the magnetic fields is reduced when the distance between the two heating coils is short. The effect is increased, and the magnetic field between the two heating coils becomes larger than the magnetic field on the heating coil, making it impossible to heat uniformly. Therefore, in order to uniformly heat the pan using the cooperative effect of the magnetic field, it is necessary to have a certain distance between the two heating coils. Therefore, if the size of the heatable region and the number of heating coils are fixed, compared to those in which adjacent heating coils are in contact with each other, or in the distance between the coils close to them, there are two Since it is necessary to ensure the distance between the heating coils, the size of the heating coils must be reduced. In order to reduce the size of the heating coil, it is conceivable to reduce the number of turns of the heating coil, to reduce the wire diameter or the number of strands. However, in the former means, since the resistance of the pan as viewed from the heating coil becomes small, a large amount of current is required to input the same power, and the heating efficiency is deteriorated. Further, the latter means has a problem that high electric power cannot be output because the current that can flow through the heating coil is reduced due to the problem of heat generation from the heating coil due to the loss of the heating coil itself.

  Further, in the above invention, which needs to have a certain distance between the heating coils, when the four heating coils are arranged in a square shape, the magnetic field is difficult to be coordinated at the center point when the four heating coils are regarded as one lump. In addition, since the distance between the center point and the heating coil is increased, it is difficult to heat the center point compared to the case where the four heating coils are close to each other, and it is very difficult to adjust the distance of the heating coil for uniform heating. There was also a problem.

The present invention solves the above-mentioned conventional problems, and can heat the pan uniformly while effectively using the installation surface by reducing the dead space as compared with the conventional configuration described in Patent Document 3. It is possible to provide an induction heating cooker that can improve cooking performance.

In order to solve the conventional problems, an induction heating cooker according to the present invention has substantially the same shape and size as a top plate on which an object to be heated is placed, and is substantially flush with the top plate. has four heating coils disposed close to each other, said four heating two inverters supplying coil power, and a control unit for controlling the output of the two inverters in the four heating The coil is composed of two heating coil groups configured by connecting two heating coils arranged on a rectangular diagonal line in series, and the two heating coil groups are each supplied with electric power by the two inverters, When the phase difference θ of the power supplied from the two inverters to the two heating coil groups is set to 0, the magnetic fields cancel each other between adjacent heating coils, and the phase difference θ is set to π. When are those magnetic field between the heating coil adjacent is a state mutually cooperate.

  Thus, by reducing the dead space, it is possible to uniformly heat the pan while effectively using the installation surface, and to provide an induction heating cooker that can improve cooking performance.

Since the induction heating cooker of the present invention can achieve cancellation and cooperation with all heating coils even if the number of heating coils and inverters is not the same, the number of inverters can be reduced by applying the present invention. It can be reduced and reduced, and it can be heated uniformly or with high efficiency .

The block diagram which shows the structure of the induction heating cooking appliance of Embodiment 1 of this invention. The heating coil top view which shows the positional relationship of the heating coil of Embodiment 1 of this invention The figure which defines the direction of the electric current of the two heating coils of Embodiment 1 of this invention The figure which shows a current waveform when phase difference (theta) of Embodiment 1 of this invention is 0 The figure which shows a current waveform when phase difference (theta) of Embodiment 1 of this invention is (pi) / 2. The figure which shows the relationship between the distance from a heating coil center, and the temperature rise (DELTA) of a magnetic SUS pan in one heating coil with a radius of 4 cm. The figure which shows the relationship between the distance from the center of a heating coil, and the temperature rise rate of a magnetic SUS pan in two heating coils with a radius of 4 cm The figure which shows the relationship between the distance from the center of a heating coil, and the temperature rise rate of a multilayer pan in two heating coils with a radius of 4 cm The figure which shows the relationship between the distance from the center of a heating coil, and the temperature rise rate of a magnetic SUS pan in two heating coils with a radius of 9 cm The block diagram which shows the structure of the induction heating cooking appliance of Embodiment 2 of this invention. The figure which shows the current waveform when phase difference (theta) of Embodiment 2 of this invention is (pi). The figure which shows the connection structure of the heating coil and inverter of Embodiment 3 of this invention. The figure which shows the circuit structure of the inverter of Embodiment 4 of this invention. The figure which shows the gate signal and current waveform of the switching element of Embodiment 4 of this invention The figure which shows the relationship of the gate signal when changing the phase difference of Embodiment 4 of this invention. The figure which shows the number of the heating coils of 5th Embodiment of this invention, and direction of an electric current. The figure which shows the relationship of the magnetic field which generate | occur | produces from each coil when the direction of an electric current is made the same between two adjacent heating coils of Embodiment 6 of this invention. The figure which shows the magnetic field area | region which influences the two heating coils distance of Embodiment 6 of this invention The figure which shows the relationship between arrangement | positioning of the heating coil in the induction heating cooking appliance of Embodiment 6 of this invention, and a user's operation position. The figure which shows the arrangement | positioning relationship of the some heating coil and magnetic-shielding ring of Embodiment 7 of this invention The figure which shows the relationship between the operating frequency of Embodiment 8 of this invention, and heating electric power. The figure which shows the electric current waveform which flows into a heating coil when phase difference (theta) of Embodiment 9 of this invention is set to (pi), and Duty is changed.

According to a first aspect of the present invention, there are provided a top plate for placing an object to be heated, four heating coils having substantially the same shape and size and arranged in the vicinity of the substantially same plane below the top plate. , Two inverters for supplying power to the four heating coils, and a control unit for controlling the outputs of the two inverters, and the four heating coils are arranged on two diagonal lines. The heating coil is composed of two heating coil groups configured in series, and the two heating coil groups are each supplied with electric power by the two inverters, and the two inverters supply the two heating coil groups. When the phase difference θ of the power is 0, the magnetic fields cancel each other between adjacent heating coils, and when the phase difference θ is π, the magnetic fields are coordinated between the adjacent heating coils. With the induction heating cooker as a state, since the operation of each other and coordinated cancellation even heating coil and the inverter is not the same number can be implemented in all the heating coil, by applying the present invention, the inverter It is possible to heat uniformly at a low cost by reducing the number of the above, or to heat with high efficiency .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a block diagram showing the configuration of the induction heating cooker according to the first embodiment of the present invention. The top plate 11 is made of an electrical insulator such as glass or ceramic. A plurality of heating coils 12 shown in FIG. 2 are arranged below the top plate 11, but in FIG. 1, two heating coils 13 arranged closest to each other are representatively represented from the plurality of heating coils 12. Is illustrated. The distance between the upper surfaces of the plurality of heating coils 12 and the lower surface of the top plate 11 is realistically within 10 mm from the relationship between the pan and the heating coil.

  The connection relationship of the inverter 14 for supplying power to the plurality of heating coils 12, the control unit 15 for controlling the output of the inverter 14, and the operation unit 16 for instructing start / stop of heating, setting of thermal power, etc. is as shown in FIG. It is. The operation unit 16 is disposed at the upper end of the top plate 11 and is in a form that is easy for the user to use.

  A pan 17 is placed on the top surface of the top plate 11. Directly above the plurality of heating coils 12 via the top plate 11 is at least a heatable region.

  In FIG. 2, the arrangement | positioning relationship of the some heating coil 12 of Embodiment 1 of this invention is shown. The plurality of heating coils 12 are arranged in a matrix, and FIG. 2 shows nine heating coils as a representative.

  When the distance between the coils of the two heating coils 13 arranged closest to each other is a and the radius of the heating coil is b, the heating coils 13 are arranged so as to satisfy the relationship of 0 ≦ a ≦ b. The basis for this will be described later.

  FIG. 3 defines the direction of the current flowing through the two heating coils 13. The current flowing in the left heating coil 27 in FIG. 3 is I1, the current flowing in the right heating coil 28 is I2, and the case where the current flows counterclockwise in both the heating coils is a positive value.

  FIG. 4 shows a current waveform when the phase difference θ between the currents I1 and I2 is zero. When the phase difference θ is 0, in the vicinity of the proximity of the two heating coils 13, the currents flowing through the heating coils are always in opposite directions, and the magnetic fields generated by the mutual heating coils cancel each other. Then, there is almost no magnetic field within the distance a between adjacent heating coils, and the pan becomes difficult to be heated. However, since the distance a between the heating coils is close to the radius b of the heating coil or less, the magnetic field on the heating coil wire is strongly generated and the portion where the pan becomes high temperature is improved. An increase in the amount of heat transfer contributes, and as a result, the pan can be heated uniformly.

  FIG. 5 shows a current waveform when the phase difference θ between the currents I1 and I2 is π / 2. When the phase difference θ is π / 2, in the vicinity of the proximity of the two heating coils 13, the current flowing in the heating coils is halved in the same direction as the opposite direction, canceling out the magnetic fields generated by the heating coils. Co-operation takes place in half each. In this state, the interference of the magnetic field within the distance a between the adjacent heating coils is negligible in terms of calorific value, and the calorific value of the pan is an addition when operating with only a single heating coil.

  Fig. 6 shows the relationship between the distance from the center of the heating coil and the temperature rise of the pan when heating the magnetic SUS pan by applying about 200 W to one heating coil with an outer diameter of 8 cm and an inner diameter of 3 cm. It is. Here, in this experiment, the distance between the top plate 11 and the heating coil is 8 mm. It can be seen from FIG. 6 that the temperature rise is highest when the distance from the center of the heating coil, which is directly above the heating coil wire, is 2 cm.

  The heat generation distribution when the two heating coils 13 are operated with a phase difference θ of π / 2 may be obtained by adding the results obtained in FIG. 6 according to the distance a of the heating coils, and the results are shown in FIG. Shown in The horizontal axis of FIG. 7 represents the distance on a straight line toward the center of the second heating coil, where the center of one of the two heating coils 13 is 0 cm. The vertical axis | shaft in FIG. 7 has shown the ratio of the temperature rise which made the maximum value of the temperature rise of a pan 100%.

  When the distance a between the two heating coils is 4 cm, the center point between the two heating coils is 6 cm, which is the radius of the heating coil 4 cm and 2 cm which is half of the distance a. It can be seen that is lower than other points. This is because the amount of heat between the heating coils is reduced because the distance between the two heating coils is too large. If the pan is heated uniformly by the distance between the heating coils, the invention described in Patent Document 3 is effective. However, as described above, if the distance a between the heating coils is long, there are many problems such as an increase in the size of the heating coils, and the effective surface on which the heating coils can be arranged cannot be fully utilized.

  Next, looking at the case where the distance a between the heating coils is 2 cm, the pan can be heated uniformly with a heating distribution of less than 10% over a long distance centering on 5 cm as the center point between the heating coils. You can see that That is, when the distance a between the heating coils is 2 cm, the pan can be heated uniformly if the two heating coils are operated simultaneously and the phase difference θ of the current flowing through the heating coils is π / 2. When the experiment is performed with two heating coils, the heat retaining property is increased, and in the data in which the distance a between the heating coils in FIG. 7 is 2 cm, the portion where the temperature rise slightly falls between 4 cm to 6 cm is almost flat or slightly bulging. It becomes a state.

Finally, in the case where the distance a between the heating coils is 0 cm, a convex state having a temperature rise peak value at 4 cm which is the center point (= contact point) between the heating coils is obtained. This is because the distance between the heating coils is short because the distance between the heating coils is close, and the magnetic field near the center point between the heating coils becomes stronger than the magnetic field directly above the heating coil wire when the heating value by one heating coil is doubled. Because. In this case, by setting the phase difference θ between π / 2 and 0, the magnetic fields generated from the heating coils cancel each other, and the level of cancellation is controlled by adjusting the phase difference θ. In the vicinity of the center point between the heating coils where interference occurs, heating can be made difficult, the level of the peak value of the temperature distribution can be reduced, the temperature distribution can be improved, and the pan can be heated uniformly.

  FIG. 8 shows a case where the type of the pan is changed to a multi-layer pan, and the temperature data is measured in the same manner as shown in FIG. 6 and is a result of adding according to the distance between the heating coils. Multi-layer pans have better heat transfer performance than pans with a single layer and poor heat transfer, such as magnetic SUS pans, and it is easy to equalize the heating temperature, but as shown in FIG. It can be seen that a temperature gradient is formed according to the distance and that the temperature distribution is flattened at 2 cm as in the case of the magnetic SUS pan.

  FIG. 9 is a view similar to FIGS. 7 and 8 when the pan is a magnetic SUS pan and the size of the heating coil is about double the outer diameter of 18 cm. FIG. 8 shows that the temperature gradient is flattened when the distance a between the heating coils is 4.5 cm. This is because the heating area near the straight line connecting the centers of the two heating coils increases as the radius of the heating coil increases, improving the heat retention and increasing the area where heat can be transferred to the measurement point. Possible cause. From this result, since the relationship between the distance a between the heating coils and the radius b of the heating coil is experimentally a ≦ b, the distance a between the heating coils is defined.

  In a state where the phase difference θ of the current flowing through the two heating coils 13 is π / 2, the distance a between the heating coils that can uniformly heat the pan between the centers of the two heating coils is substantially a radius, and the heating coil is more than that. When the distance is short, the temperature distribution has a temperature rise peak value at the center point between the heating coils. In that case, the temperature rise peak value can be suppressed by changing the phase difference θ between π / 2 and 0. Since there is a phase difference θ that can be uniformly heated when the phase difference θ is between π / 2 and 0, even if the distance a between the heating coils is short, the technique of the present invention is used. The heating container can be heated uniformly.

  In addition, when the inventors tried an experiment with a distance a between the heating coils of 0 cm and a phase difference θ of 0, it was confirmed that the pan could be heated uniformly between the centers of the two heating coils.

  Depending on the relationship between the heating coil size and the distance between the heating coils, the phase difference θ that can heat the pan uniformly can be determined approximately. However, if you want to heat the pan more accurately, the temperature sensor measures the temperature of the pan. And the phase difference may be controlled according to the temperature state of the pan. In that case, if it is judged that the temperature of the pan above the center between the heating coils is higher than the temperature of the pan above the heating coil wire, the temperature of the pan above the center between the heating coils is decreased by reducing the phase difference θ. To do. Conversely, if it is determined that the temperature of the pan above the center between the heating coils is lower than the temperature of the pan above the heating coil wire, the temperature of the pan above the center between the heating coils is increased by increasing the phase difference θ. To raise.

(Embodiment 2)
In FIG. 10, the structure of the induction heating cooking appliance of Embodiment 2 of this invention is shown. The difference from the configuration of the induction heating cooker shown in FIG. 1 is that a phase difference switching unit 18 is provided. The phase difference switching unit 18 shown in FIG. 10 has an inverter 14 and one of the two heating coils when supplying power to both heating coils of the two heating coils 13 that are close to each other. There is a relay between the connections, and the connection is physically switched. With the phase difference switching unit 18 shown in the present embodiment, the phase difference between the currents flowing through the two adjacent heating coils 13 can be realized as 0 or π.

  For example, as shown in FIG. 11, by setting the phase difference θ to π, the magnetic fields generated from the two heating coils cooperate most strongly. When the magnetic field is coordinated by the relationship of the distance a between the heating coils <the radius b of the heating coil, the temperature of the pan above the central point between the heating coils rises to a temperature higher than the phase difference θ operated at π / 2. The distribution is further deteriorated, but the magnetic field canceling is reduced, so that the heating can be performed with high efficiency.

  In addition, by coordinating the magnetic field, the magnetic coupling between the heating coil and the pan is improved, so that the resistance of the panning seen from the heating coil increases, and when compared with the same heating power, compared to the case of cancellation operation As a result, less current flows through the heating coil, reducing the burden on circuit components and making it easier to achieve high output.

  Furthermore, in the case of the same heating power, heating with high efficiency requires less cooling of the heating coil and the inverter 14, so that it is possible to bring out merits other than efficiency, such as noise reduction due to a decrease in the number of rotations of the cooling fan.

  From this point, it becomes impossible to heat the pan uniformly by setting the phase difference θ to π to π / 2, but it is suitable for high output and high efficiency, so it is used properly depending on the cooking menu. It is desirable. For example, in a cooked product such as an egg-bake or a hot cake that does not require a high output and is more advantageous to be heated uniformly, it operates with a phase difference θ between π / 2 and 0 and is heated uniformly. To give priority. Moreover, when high output and high efficiency are required, such as boiling water, the induction heating cooker with good cooking performance can be provided by operating the phase difference θ between π and π / 2.

(Embodiment 3)
The inverter 14 may be composed of a plurality of inverters. In that case, connection of at least one heating coil is essential for each of the plurality of inverters. When the number of inverters is n and the number of heating coils is k, at least one heating coil can be connected to one inverter by dividing the k heating coils into n. Here, it is necessary that n ≦ k. When n = k, one inverter is connected to one heating coil.

  FIG. 12 shows an example of the relationship between the number of inverters and the number of heating coils and the connection method thereof according to the third embodiment of the present invention.

  FIG. 12 shows an induction heating cooker composed of two inverters and four heating coils. The four heating coils are divided into two heating coil groups, the heating coils of the same group are connected in series, and the heating coils are arranged on a rectangular diagonal line.

  By providing multiple inverters, output can be started / stopped and adjusted for each inverter, and power is not supplied to heating coils that do not need to be output for reasons such as not placing a pan. Thus, the heating efficiency can be improved and the leakage magnetic field can be reduced.

In addition, as shown in FIG. 12, when the heating coils are wound from the inside to the outside, when four heating coils wound in the same direction (left-handed in FIG. 12) are arranged, the heating coils in the same group are connected to one side. When the heating coil is on the inside, the other heating coil is on the outside. Then, when the phase difference θ between the inverter 1 and the inverter 2 in FIG. 12 is 0, the magnetic field generated from the heating coil connected to the inverter 1 and the heating coil connected to the inverter 2 is between adjacent coils. Will always cancel each other out. Conversely, when the phase difference θ between the inverter 1 and the inverter 2 is π, the magnetic field generated from the heating coil connected to the inverter 1 and the heating coil connected to the inverter 2 is always coordinated between the adjacent coils. It becomes a state to do. In other words, even if the number of heating coils and inverters is not the same, canceling and cooperative operations can be realized with all the heating coils. Therefore, by applying the present invention, the number of inverters can be reduced and uniformly reduced. Heating can be performed with high efficiency.

(Embodiment 4)
FIG. 13 shows a circuit diagram of an inverter 14 for flowing a high-frequency current through two adjacent heating coils 13 according to the fourth embodiment of the present invention. A power source obtained by full-wave rectifying the commercial power source 19 with the diode bridge 20 is supplied to the inverter unit 22 via the filter unit 21. The inverter unit 22 is a SEPP circuit that is a typical circuit of a constant frequency power conversion (VPCF) circuit. When the pair of the first switching element 23 and the second switching element 24 and the pair of the third switching element 25 and the fourth switching element 26 are exclusively turned on / off, the left heating coil 27 and the right heating coil A high frequency current flows through the coil 28. The first to fourth switching elements in FIG. 13 are formed of IGBTs, and perform on / off operations by inputting gate signals g1 to g4 to the gates of the IGBTs.

  By inputting the gate signals g1 and g2 as shown in FIG. 14 to the first switching element 23 and the second switching element 24, a high-frequency current as shown in the lower part of FIG. An eddy current is generated in the pan 17 by applying a high frequency magnetic field generated by the high frequency current to the pan 17, and the pan 17 is heated with the eddy current and the specific resistance of the pan 17.

  In FIG. 13, there are two heating coils and two inverters in a one-to-one relationship. The second inverter composed of the third switching element 25, the fourth switching element 26, the right heating coil 28, etc. shares the diode bridge 20 and the filter unit 21 with the first inverter, and the first inverter Connected in parallel.

  The two inverters drive the first to fourth switching elements by gate signals g1 to g4 from the control unit 15. At this time, if the timing of the gate signal g1 and the timing of the gate signal g3 are the same, that is, the phase difference θ is set to 0, the current I2 flowing to the right heating coil 28 is also positive when the current I1 flowing to the left heating coil 27 is positive. Thus, when the current I1 is negative, the current I2 is also negative, so that the magnetic field between two adjacent heating coils can be canceled out.

  Conversely, as shown in FIG. 15, when the operation is performed with a phase difference θ1 in which the timing of the gate signal g3 is shifted by π with respect to the gate signal g1, the current I1 flowing through the left heating coil 27 flows into the right heating coil 28 when positive. Since the current I2 is negative and the current I2 is positive when the current I1 is negative, the magnetic field between two adjacent heating coils can be in a coordinated state.

  Further, when the gate signal g1 and the gate signal g3 are operated at a phase difference θ2 in which the timing of the gate signal g3 is shifted by π / 2, the state of cancellation of the magnetic field and the state of cooperation are halved. Can generate the same amount of heat as operating without interference, and the heating distribution can be the sum of the amounts of heat generated by the two heating coils.

  By having two inverters independently, various heating patterns such as energization of only the left heating coil 27 and a change in the heating power balance between the left heating coil 27 and the right heating coil 28 can be realized.

  Phase difference switching is performed by shifting the timing at which the switching elements that make up the inverter transition to a conductive state or non-conductive state between multiple inverters, using relays and other fragile components Thus, the phase difference can be changed without increasing the reliability of the product, and the number of parts used can be reduced, resulting in an inexpensive product. Moreover, in the phase difference control by shifting the conduction timing, the phase difference can be continuously changed between π and 0, so that the state of interference can be finely controlled. It is possible to heat more uniformly by adapting to the change or introducing a temperature sensor.

(Embodiment 5)
FIG. 16 is a diagram showing the relationship between the number of heating coils for heating one pan and the direction of current in the fifth embodiment.

  In a plurality of heating coils that heat a single pan 17 by interfering with the magnetic fields generated by the mutual heating coils, for example, the distance from the center of the mounting position of the pan 17 to the center of each heating coil is set to be equal. A heating coil shall be arranged in As shown in FIG. 16A, when one pan 17 is heated with three (odd) heating coils, interference canceling out the magnetic field can be realized at all three points where the two heating coils are close to each other. It is impossible to perform cooperative operation at all three points where the magnetic field interferes. For example, when a current is applied in the direction indicated by the arrow in FIG. 16A, a cooperative operation is performed at two of the three points causing interference, but a canceling operation is always generated at the remaining one point indicated by a broken line. End up. However, as shown in FIG. 16B, when one pan 17 is heated with four (even) heating coils, both the interference that cancels out the magnetic field and the interference that cooperates are the four heating coils that are closest to each other. Since it becomes realizable in all the points, there is no bias in the heating distribution, and a cooker with good cooking performance can be provided.

(Embodiment 6)
FIG. 17 shows a cross-sectional view of the two heating coils 13 when the magnetic fields generated by the two heating coils 13 are coordinated. When the magnetic fields are coordinated, a large magnetic field loop is formed as indicated by the solid arrows in FIG. Heats strongly. At this time, the magnetic field is coordinated on the heating surface of the pan 17 through the top plate 11 from the heating coil, but in the region A between the heating coil wires, the upper side of the drawing generated from the left heating coil is directed downward. And the magnetic field generated from the lower side of the drawing, which is generated from the right side heating coil, cancel each other, and the synthesized magnetic field becomes smaller. Therefore, as shown in FIG. 18, when the current Ia and the current Ib flowing in the heating coil are in the same direction, the leakage magnetic field in the region A is almost eliminated in the vicinity of the surface where the heating coil is arranged. Can be provided. In the region B, the leakage magnetic field increases as compared with the region A, but the leakage magnetic field can be remarkably reduced as compared with the case where one pan is heated by one heating coil.

FIG. 19 is a top view of the induction heating cooker, showing the relationship between the operation unit and the arrangement of the heating coils. The casing 30 of the induction heating cooker includes a heating coil 12 that heats one pan with four heating coils, an intake / exhaust port 29 that serves as a passage for air for cooling the heating coil and the inverter circuit, and an operation unit. 16 is arranged. Here, the operation unit 16 is disposed at a location near the operation position 31 of the user. As shown in FIG. 19, among the four heating coils that operate simultaneously to heat one pan, two heating coils that operate closest to the place where the user of the cooker is positioned are positioned by the user. It is arranged so as to be substantially parallel to one side of the casing closest to the place. Thereby, a user will be located in the area | region A and the area | region B with few leakage magnetic fields shown in FIG. 18, and safety can be improved. In particular, when a user with a pacemaker or a user who is wearing a wristwatch that is sensitive to magnetism operates an induction heating cooker, the effect of preventing malfunction increases, and cooking is safe. An induction heating cooker can be provided.

(Embodiment 7)
FIG. 20 shows the arrangement relationship between the heating coil and the magnetic shield ring of an induction heating cooker that heats one pan with four heating coils.

  When the current Ia flows through the heating coil arranged at the upper right in FIG. 20 in the direction of the solid arrow, the generated magnetic field is, as indicated by the broken line, the inner side of the coil → the upper surface of the coil → the outer side of the coil → the coil. From bottom to closed inside of the coil.

  When heating one pan with a single heating coil as in the prior art, the magnetic shield ring for reducing the leakage magnetic field to the outside that does not contribute to heating is substantially the same as the center of the heating coil, and the outer periphery of the heating coil Are arranged to loop. Then, a counter electromotive force is generated in the magnetic shield ring in accordance with the amount of the magnetic field that attempts to loop outside the magnetic shield ring, and a current flows in a direction to cancel the magnetic field, so that the leakage magnetic field can be reduced. However, when a single pan is heated with a plurality of heating coils as in the present invention, if a magnetic shielding ring is arranged on the outer periphery of each heating coil, a magnetic field is hardly generated in the outer direction of the magnetic shielding ring, and adjacent to each other. The magnetic field interference between the two heating coils is eliminated, and the effect of the present invention cannot be obtained.

  Therefore, when a single pan is heated by a plurality of heating coils, the magnetic-shielding ring 32 is arranged so as to surround all the heating coils that may operate simultaneously to heat the single pan. When the heating coil currents Ia, Ib, Ic, and Id shown in FIG. 20 are flowing in the directions of the arrows, the directions of the currents flowing through the two adjacent heating coils are opposite to each other. It becomes. At this time, the direction of the magnetic field generated by the four heating coils is the direction indicated by the broken line. The direction of the magnetic field that the magnetic field generated by the individual heating coil portion closest to the magnetic shield ring 32 tries to loop outside the magnetic shield ring 32 is such that all four heating coils are oriented from the top to the bottom. Are generated in the same direction, and the current Ie flows in a direction that cancels out the combined magnetic field that leaks from the four heating coils. As a result, the magnetic field leaking to the outer periphery of the magnetic shield ring 32 can be reduced.

  Furthermore, with this configuration, interference between two adjacent heating coils is not suppressed by the magnetic-shielding ring 32, so that the effect of high-efficiency and high-power heating by the operation of cancellation or the operation of cooperation is maintained. Can do.

(Embodiment 8)
FIG. 21 shows the relationship between the operating frequency and the heating power when the phase difference θ is operated at 0 and π in the same pan. Here, in the SEPP circuit of FIG. 13, the conduction ratio (Duty) of the first switching element 23 and the second switching element 24, and the third switching element 25 and the fourth switching element 26 is constant.

  When the resonance frequency matches the operating frequency, the power enters most.

When the phase difference θ is operated at π as compared with the case where the phase difference θ is operated at 0, the magnetic flux applied to the pan increases because of the cooperation of the magnetic field, and the coupling is improved. As a result, the equivalent resistance included in the pan as viewed from the terminal of the heating coil is increased, and the inductance is also increased. When the resonance capacitor is constant, the resonance frequency decreases as the inductance increases. Therefore, as shown in FIG. 21, the operating frequency at the peak point of the heating power decreases. Considering that it is essential to operate at a higher operating frequency than the resonant frequency in order to perform zero-voltage soft switching operation in order to reduce switching loss, cooperative operation is more effective than cancellation operation. However, since there is a possibility that the rated power cannot be output unless the operating frequency of the inverter is lowered, the operating frequency is set lower than the canceling operation in the cooperative operation of magnetic fields.

  Conversely, if the operating frequency of the inverter is operated in a coordinated manner so that the rated power can be output, the operating frequency may be lower than the resonant frequency when canceling each other. Since switching loss increases, the operating frequency at the time of cancellation operation needs to be higher than the cooperative operating frequency. When this condition is satisfied, power control can be performed in the region above the resonance frequency and switching loss can be reduced due to the characteristics of the voltage source supply type SEPP inverter shown in FIG. Induction heating cookers and induction heating cookers with good heating efficiency can be provided.

(Embodiment 9)
FIG. 22 shows two adjacent heating coils when the duty ratio, which is the ratio between the conductive state and the non-conductive state of the first switching element 23 and the second switching element 24, is changed to other than 0.5. The current waveform which flows is shown. Here, the duty ratio Duty of the third switching element 25 and the fourth switching element 26 is also changed to other than 0.5.

  In the present embodiment, the power adjustment is performed by changing the duty. However, as a matter of course, the power adjustment can be performed even if the operating frequency of the switching element is changed.

  The power adjustment means for changing the duty does not change the fundamental frequency of the heating coil current, but includes a harmonic component at n and the waveform is distorted compared to a sine wave. When the phase difference is changed by changing the timing, in the connection shown in FIG. 13, the values of the current I1 and the current I2 for each moment when the cooperative operation is performed are different. However, although the instantaneous values of the currents do not match, the timing at which the direction of the current switches between positive and negative hardly changes, so that the effect of magnetic field cooperation in the present invention is sufficiently exerted. Depending on the method of connecting the heating coils, there may be cases where the instantaneous values of the current are different in the case of canceling the magnetic field, but even in this case, the effect of canceling the magnetic field is sufficiently exhibited.

  In addition, in the power adjustment as in the present embodiment in which the operating frequency is not changed, the operating frequency is the same as that of the adjacent burner, so that no roaring interference sound is generated and the user feels uncomfortable due to the abnormal sound. It is possible to provide an induction heating cooker without the above.

  In all the above embodiments, in order to clarify the relationship between two heating coils that are close to each other, the operation and the principle are explained using two or four heating coils. The number of heating coils is not limited to two or four, but can be applied to any structure that interferes with the magnetic field generated from the heating coils, such as a matrix as shown in FIG. Technology.

  INDUSTRIAL APPLICABILITY The present invention is useful for an induction heating cooker that requires uniform heating because a pot that is an object to be heated can be uniformly heated in the induction heating cooker. Moreover, since it can also heat with high efficiency by carrying out a coordinated operation, it is useful for the high-function induction heating cooking appliance which changes operation | movement according to a heating use.

  Furthermore, in the embodiment of the present invention, the technical explanation has been given with the induction heating cooker, but the present technology can be applied to all apparatuses that require uniform heating in the induction heating apparatus. Is very useful.

DESCRIPTION OF SYMBOLS 11 Top plate 12 Several heating coils 13 Two heating coils arrange | positioned nearest to 1, 2, 14, inverter 15 Control part 16 Operation part 17 Pan (to-be-heated object)
DESCRIPTION OF SYMBOLS 18 Phase difference switching part 19 Commercial power supply 20 Diode bridge 21 Filter part 22 Inverter part 23 1st switching element 24 2nd switching element 25 3rd switching element 26 4th switching element 27 Left heating coil 28 Right heating coil 29 Inlet / exhaust port 30 IH cooking heater (housing)
31 User operation position 32 Magnetic shield ring

Claims (1)

A top plate for placing an object to be heated, four heating coils having substantially the same shape and size and disposed in the vicinity of the same plane below the top plate, and the four heating coils Two inverters for supplying electric power, and a controller for controlling the outputs of the two inverters, and the four heating coils are connected in series with two heating coils arranged on a rectangular diagonal line Each of the two heating coil groups is supplied with electric power by the two inverters, and the phase difference θ of the electric power supplied by the two inverters to the two heating coil groups is 0. a state next to the magnetic field are canceled between the heating coil adjacent the when, ing a state where the magnetic field between the heating coil adjacent with each other in coordination when the phase difference θ was π induced Heating cooker.

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